Magmatic phosphite and thermally polymerized phosphate 3.2 billion years ago: Implications for early life

Magmatic phosphite and thermally polymerized phosphate 3.2 billion years ago: Implications for early life | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Magmatic phosphite and thermally polymerized phosphate 3.2 billion years ago: Implications for early life Abu Baidya, Michelle Gehringer, Cristian Savaniu, Christoph Heubeck, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6529805/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 13 Nov, 2025 Read the published version in Communications Earth & Environment → Version 1 posted You are reading this latest preprint version Abstract Reduced and polymerized phosphorus (P) species may have been crucial for the origin and early evolution of life, as they are more reactive and soluble than phosphate (P(V)). Thermal processes could have produced these P species; however, the underlying mechanism is poorly constrained, and geological evidence of polymerized P in the Precambrian is so far absent. Here, we investigated contact-metamorphic rocks from the ca. 3.22 Ga Moodies Group (South Africa), where mafic dikes intruded into shallow-marine sediments. We provide evidence of magmatic phosphite (up to 2.85 ppm) and metamorphic polyphosphate (up to 39.3 ppm) in the Archean. Our laboratory experiments suggest that carbon can facilitate the thermal production of polyphosphates and reduced P species including phosphide from less reactive minerals including apatite and vivianite. We conclude that magmatic and thermal-metamorphic rocks could have provided soluble and reactive P species crucial for the origin and early evolution of life. Earth and environmental sciences/Solid Earth sciences/Geochemistry Earth and environmental sciences/Biogeochemistry/Element cycles Earth and environmental sciences/Solid Earth sciences/Geology/Precambrian geology Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Phosphorus is a key element for modern biological systems and has likely played an important role in the origin of life on our planet 1 , 2 . Unlike other major elements (C, H, O, N, S) required for the origin of life, P does not have a stable gaseous phase, is less abundant, and is locked in solid rocks in its most abundant form, phosphate (P(V), where P has an oxidation state of + 5). Furthermore, P(V) is only weakly reactive towards organic compounds, which could have hindered abiotic phosphorylation of biomolecules. The low solubility and low reactivity of P(V) thus raise questions on the journey of P from rock to life - a conundrum that has become known as the ‘P-problem’ 3 . Reduced and polymerized P species have been proposed to solve the ‘P-problem’ 1 , 2 . Polymerized P species (also known as condensed P), including pyrophosphate (PP(V)), triphosphate (PPP(V)), tetra- and other higher-order phosphates (PPPP(V)), and cyclophosphates such as trimetaphosphate (PPPc) are more reactive than unpolymerized P(V) and, therefore, may have facilitated phosphorylation on the prebiotic Earth. The simplest polyphosphates is dimer PP(V), which could have been a phosphorylating agent 4 , a source of ATP-based metabolism, and a potential energy source for early life 2 . Similarly, cyclophosphates may phosphorylate several organic compounds including glyceric acid, sugars, amino acids, and nucleosides 5 . Thermal processes in metamorphic and magmatic environments have been proposed to produce polyphosphates, such as (1) dry-heating of sodium or ammonium phosphate salt (e.g., NaH 2 PO 4 /NH 4 H 2 PO 4 ) and rare minerals (whitlockite (Ca 18 Mg 2 H 2 (PO 4 ) 14 ), newberyite (MgHPO 4 ·3H 2 O), struvite (MgNH 4 PO 4 ·6H 2 O), brushite (CaHPO 4 ·2H 2 O), and amorphous Fe-phosphate at 80–600°C, especially in the presence of urea and other organics or Fe-Cr-Ni-bearing minerals 6 – 10 ; and (2) partial dissolution of P 4 O 10 produced in high-temperature (> 1200°C) volcanic processes 11 . Volcanic fumaroles in modern-day Japan and 2.5–14 Myr-old contact-metamorphic rocks from the Levant region have been shown to contain polyphosphates 11 , 12 . However, there is so far no geological record of polyphosphates older than the Miocene, so the validity and importance of thermal or magmatic formation of polyphosphates in early Earth history is not known. Reduced P species such as phosphite (P(III), oxidation state of 3+), hypophosphite (P(I), oxidation state of + 1), and phosphonate (molecules with P-C bonds and P with a 3 + oxidation state) are more soluble than P(V) in the presence of bivalent metals such as Ca and Fe 8 . Furthermore, they are more reactive than P(V). For example, P(III) is ca. 1,000 times more soluble than P(V) in natural fluids including seawater and more efficient than P(V) in forming organophosphorus compounds 1 , 8 . P(I) is even more reactive than P(III), and P-C compounds already contain P-C bonds, suggesting that these reduced P species may act as more efficient phosphorylating agents than P(V). Thermal processes have been proposed as important routes to form reduced P species, such as metamorphic heating of phosphate in the presence of Fe 2+ , H 2 and/or organic matter 8 , 9 , 13 – 15 . However, these studies use sodium and ammonium phosphate as a precursor, which may not be relevant for early Earth as these salts do not readily form in nature 6 . Therefore, the underlying mechanism of P(V) reduction, particularly P(V) hosted in naturally occurring minerals such as apatite and vivianite that are considered less reactive, is not well understood. Importantly, only one study has documented P(V) reduction by metamorphic conditions in the Precambrian, specifically in seven Eoarchean carbonates and iron formation samples of amphibolite to granulite metamorphic grade 8 , 15 . Therefore, the importance of thermal P(V) reduction on the early Earth is so far poorly constrained. To explore the effect of heat on P speciation in the Archean, we turned to the Paleoarchean Moodies Group (ca. 3.2 Ga) of the Barberton Greenstone Belt in South Africa, where mafic intrusions invaded into shallow-marine biomass-bearing sedimentary rocks 16 , 17 , providing an ideal test bed for exploring if P polymerization and/or reduction could occur under Archean thermal metamorphic conditions. We collected 5 samples from metasedimentary units, 2 from intrusive units, and 4 from the contact zones between them and measured the concentrations of P(I), P(III), P(V), and PP(V), along with major and minor elemental abundances (see Methods). To validate our findings in Moodies Group and previous findings of phosphate reduction in other locations (e.g., the 2.5–14 Ma old Levant region and 60 Ma old Disko Island), we additionally performed laboratory experiments that replicated thermal metamorphism of biomass- and P-bearing sediments. We chose four prebiotically relevant P(V) minerals, namely, hydroxyapatite ((Ca 5 (PO 4 ) 3 (OH)), magnesium phosphate (Mg 3 (PO 4 ) 2 ·xH 2 O);, vivianite (Fe 3 (PO 4 ) 2 ·8H 2 O), and amorphous Fe-phosphate (Fe 3 (PO 4 ) 2 ·xH 2 O) 18 and two different C sources, namely carbon black (CB) and bacterial biomass (hereafter OM for ‘organic matter’). We mixed the P(V) source, C source, and silica powder (mimicking very fine-grained sand), pelleted them, and heated them up at 1150 o C or 1300 o C in an anoxic environment. The experimental products were analyzed by powder X-ray diffraction for phase identification. Phosphorus species were extracted from the experimental products using an Ethylenediaminetetraacetic acid-sodium hydroxide solution and measured using an IC-ICPMS 19 and NMR. Collectively, our data have implications for prebiotic P chemistry as well as for the origin and early evolution of life on our planet. Results Geological Setting We investigated the contact zones of Paleoarchean metasedimentary siliciclastic rocks intruded by mafic dikes in the north-central Barberton Greenstone Belt, South Africa (Fig. 1 A). Samples were obtained from borehole BASE-1A, drilled within the framework of the ICDP BASE (Barberton Archean Surface Environments) project, which obtained continuous and unweathered core from the ca. 3.2 Ga Moodies Group (Fig. 1 B, Supplementary Fig. S1 -2). These are among the oldest well-preserved sedimentary rocks on Earth. The regional metamorphic grade is lower-greenschist facies with maximum temperatures of 420-460 o C, as indicated by Raman spectroscopy of carbonaceous matter (RSCM) 20 . Syn- and post-depositional magmatic activity affected Moodies Group strata. The most noteworthy event is the emplacement of the Moodies lava, a ca. 20–400 m thick complex of basaltic amygdaloidal lavas approximately midway in the Moodies stratigraphic column, widely overlain by dacitic air-fall tuffs dated at 3219 ± 9 Ma, 3222 ± 8 Ma, and 3228 ± 8 Ma (LA-ICP-MS U-Pb ages of zircon 17 ). An eruption age of about 3224 Ma is also consistent with a growing body of related age dates in the Moodies Group 21 . In stratigraphically correlatable Moodies Group strata in the central Barberton Greenstone Belt ca. 11 km to the south and southwest of the BASE-1A drill site, large mafic laccoliths occur, surrounded by halos of thermally altered Moodies sandstone and mafic stockwork dikes that apparently intruded in unconsolidated Moodies sands, resulting in local peperites 22 . Stratigraphic and geochronologic data indicate that stockwork dikes connect the sills, ca. 2 km below the paleosurface, with the Moodies lava, although no mappable connection has been documented yet. Stratiform mafic dikes, sills and thin lava flows were also encountered by borehole BASE-2A, ca. 7 km to the south of the BASE-1A location. Thermal alteration of sandstones was noted in borehole BASE-4B, ca. 14 km to the SSW. This alteration is probably the result of a nearby bedding-parallel-trending feldspar-porphyritic dike 21 . The diverse nature of (sub-)volcanic contributions to the Moodies Group sedimentary environments was summarized by reference 16 . The authors also documented from outcrop detail how magma at the base of the Moodies lava intruded downwards into fractured, apparently cemented Moodies sandstones (Fig. 13 in reference 16 ). This location lies only ca. 500 m NE of and stratigraphically ca. 30 m below the projected surface location of the investigated samples. Furthermore, there are two younger thermal and magnetic events in the BGB: a thermal alteration related to sulfidic and Au mineralization at ca. 3084 Ma in the northern part of BGB 23 and a younger magmatic event at ca. 2967 Ma, comprising NW-SE oriented, intermediate, feldspar-porphyritic, dolerite dikes 24 (additional information is given in the Supplementary Material). The borehole samples studied here are approximately 40 drilled meters (or ca. 25 stratigraphic meters) above the Moodies lava complex (Fig. 1 ). Core description shows that the contacts are intrusive; they are, in part, curved and free of indications of faulting or shearing (Supplementary Figs. S1 and S2). The thermal alteration event at ca. 3084 Ma is not associated with magmatism in the study area and the composition and structural orientation of the dolerite dikes of ca. 2967 Ma are different from the sampled intrusive rocks. All available geological evidence thus indicates that the contacts investigated here are likely part of magmatic-sedimentary interaction that took place during the Paleoarchean, prior to 3.2 Ga. Intrusion may have occurred at shallow depths and into unconsolidated sediment, as suggested by the nonlinear contacts, or occurred thousands to a few million years later, during late deformation of the BGB and subsequent beginning consolidation of the Kaapvaal craton. Textures and phosphorus speciation in Moodies Group rocks The metasedimentary rocks from the Moodies Group investigated in this study show alternate banding with dark and light bands containing mostly biotite and mostly quartz, respectively (Fig. 2 A, D, G), indicating alternation between shale, siltstone and fine-grained sandstone. K-feldspar, calcite, chlorite, and plagioclase are common while zircon, arsenopyrite, and apatite are accessory phases (Fig. 2 G). The metasedimentary samples do not show significant alteration (Fig. 2 D) although minor sericitization is observed at some places. The mafic intrusive bodies are massive and contain pyroxene, plagioclase, ilmenite, and olivine. Ilmenite shows skeletal textures and is mostly associated with fine-grained feldspar, pyroxene, and glassy material (Fig. S3A, B), which is indicative of quenching 26 . These quenched spots contain rare microcrystalline apatite (Fig. S3D). Olivine shows minor alteration along grain boundaries and fractures; however, the overall alteration in the rock is limited (Fig. 2 F). Of the four contacts zones that we studied, two are dominated by shale at the metasedimentary-igneous interface while two are dominated by siltstone (Supplementary Fig. S4). The intrusive units at the contact zone show variable degree of sericitization, mostly along fractures (Fig. 2 E), indicating some degree of fluid alteration. These samples show textural evidence of intrusion of a mafic melt into pre-existing sedimentary rock. First, fragments of laminated metasedimentary rock are incorporated into the intrusive units, indicating that the sedimentary rocks were already emplaced and at least somewhat lithified by the time the magma intruded (Fig. 2 B, E). Second, we observe formation of cryptocrystalline pyrite and pyrite aggregates and compositional change along the intrusive side of the contact z.one (Supplementary Fig. S5A). On the metasedimentary side, we observe aggregation of biotite (Fig. S5B). Third, apatite is present at the contact between the sedimentary unit and the intrusive bodies (Fig. S5D). Collectively, these features indicate a thermal effect on a P(V) source and associated contact-metamorphic reactions. Total Organic C concentrations are highest (833–3310 ppm) in metasedimentary rocks and lowest (76–93 ppm) in the intrusive bodies (Fig. 3 E, Supplementary Table S2). Total P concentrations are higher (590–610 ppm) in the intrusive bodies compared to the sedimentary rocks (310–330 ppm), although apatite is absent or rare in the former and common in the latter (Fig. 3 A). Contact zone samples have intermediate concentration of P (370–560 ppm), consistent with conservative mixing of the two units in bulk powders of the contact zones (Fig. 3 A). Phosphorus speciation data for Moodies Group samples are given in Supplementary Table S3. We note that P extraction yields with EDTA-NaOH solutions are low, 1.4–2.4% for the metasedimentary unit, 5.2–5.6% for the intrusive unit, and 3.8–5.2% for the contact zone samples; however, these yields are consistent with previous studies 8 , 15 . Stronger solvents may increase the yield but risk losing P speciation via oxidation of reduced P or disintegration of polymerized P. The low and variable yields thus likely explain the high level of uncertainty in measured P(III) and PP(V) concentrations, but general trends between the two lithologies and the contact zones are nevertheless comparable. We estimated concentrations of three P species in the bulk Moodies samples using the ratios of them in the EDTA-NaOH extract, total P contents of the rocks, and extraction yields. The data of extracted and estimated concentrations are shown in Table S4. Extracted P(V) concentrations in the intrusive bodies, the metasedimentary unit, and the contact zones follow a similar pattern as total P concentrations (which were measured by bulk digestion of the rock, see Methods and Materials section), indicative of conservative mixing (Fig. 3 B). Averages of estimated phosphite concentrations in intrusive, contact zone, and metasediments are up to 2.84, 1.64, and 1.13 ppm, respectively, which follows conservative mixing predictions with similar percentages of total extracted P (0.25, 0.25, and 0.18%, in metasedimentary, intrusive, and the contact zone samples, respectively; Fig. 3 C, H). For PP(V), the highest estimated (2.32-39.218 ppm) concentrations are observed in the contact zone, followed by the intrusive bodies (1.65–1.65 ppm) and sedimentary rocks (0.47–1.20 ppm) (Table S5). The highest relative proportion of PP(V) in the EDTA-NaOH extract is observed in the contact zone samples (averages for metasedimentary, intrusive, and the contact zone samples are 0.25, 0.28, and 2.14%, respectively), which cannot be explained by conservative mixing between intrusive rocks and metasediments (Fig. 2 G). We did not notice any trends in the sedimentary rocks with increasing distance from the intrusions. Carbon-phosphate mineral heating experiments To further explore the effects of heating on P-bearing sediments that also contain ferrous iron and carbon, we performed a series of experiments, which are listed in Supplementary Table S4 and results are summarized in Supplementary Table S5. Three types of control experiments were conducted to verify the sources of polymerized and reduced P in starting materials. (1) Dry heating the silica powder alone did not produce polymerized or reduced P species but produced significant P(V) at 1150 o C suggesting that the silica powder contained some P(V) but was sufficiently clean in terms of polymerized and reduced P species. (2) Heating a mixture of silica and OM without a P-source produced significant PP(V) (1.81% of total extracted P). Similarly, a mixture of silica and CB produced significant amounts of P(I), P(III), PP(V), and PPP(V) (0.04, 0.48, 22.05, and 2.97% respectively). NMR analysis identified at least two organophosphate and one phosphonate compound in the OM but none in the CB. Therefore, a part of PP(V) in the heated OM and silica mixture may be produced due to polymerization of organophosphate compounds present in the OM, but collective data from these two control experiments point to the carbon-enhanced polymerization of the unidentified P(V)-phase present in the silica. The unheated mixture of silica and CB contained a similar amount of P(III) compared to the heated mixture, implying that the carbon sources contributed background levels of reduced P, but heating did not enhance P(III) production in these controls. (3) Heating phosphate precursors in the presence of silica, particularly magnesium phosphate, hydroxyapatite, and amorphous Fe-phosphate at 1150 o C produced PP(V) with a yield of 0.003, 0.026, and 2.065%, respectively (Figs. 4 , 5 ). Neither P(III), nor any other reduced P species were detected in any of these three control experiments. The vivianite and silica mixture produced P(III) and another unknown P species, which is also present in the unheated mixture, indicating that the heating did not facilitate the formation of these species. In summary, our control experiments indicate that heating alone can polymerize P(V) above background levels, but it does not noticeably enhance reduction. Carbon in both forms impacted the polymerization of mineral-hosted P(V) with dependence on P(V) host (Supplementary Table S5 and Fig. S6, S7; Figs. 4 , 5 ). The addition of OM and CB to magnesium phosphate and silica mixtures enhanced the PP(V) yield from 0.003% (without C) to 0.047% (with OM) and 0.157% (with CB), respectively, at 1150 o C. Similarly, for hydroxyapatite, OM and CB enhanced the PP(V) yield from 0.026–0.032% and 0.289%, respectively. These yields are low compared to that for CB + silica mixture alone, implying limited polymerization of P(V) hosted in these minerals. In contrast, adding OM and CB to vivianite and silica mixtures enhanced the polymerization yield from 0.000% to 1.08 and 30.98% and produced several polymerized molecules including PP(V), PPP(V), and PPPP(V). Adding the same C sources to amorphous Fe-phosphate and silica enhanced the polymerization yield from 2.065–9.264% and 13.486%, respectively, and produced several polyphosphates and cyclophosphates including PP(V), PPP(V), PPPc(V), and PPPP(V). Better polymerization yield in Fe-phosphate phases points to the control of the mechanism of polyphosphate formation. Barringerite (Fe 2 P) but not any polyphosphates are detected in experiments containing Fe-phosphates, suggesting the formation of polyphosphates during dissolution in the EDTA solution, which is consistent with previous studies that reported polyphosphate formation during schreibersite ((Fe,Ni) 3 P) dissolution 27 , 28 . This mechanism is distinct from polyphosphate formation during amorphous Fe-phosphate heating at low temperatures (175–200 o C) where polyphosphate phases were likely formed 9 and during apatite-basalt heating where polyphosphates were formed during partial dissolution of P 4 O 10 11 . Temperature seems to be an important controlling factor for P polymerization. Previous studies suggested that simple heating of metastable Fe, Ca and Mg phosphates such as amorphous Fe-phosphate, brushite (CaHPO 4 ·2H 2 O), whitlockite (Ca 18 Mg 2 H 2 (PO 4 ) 14 ), struvite (MgNH 4 PO 4 ·6H 2 O), and newberyite (MgHPO 4 ·3H 2 O) can produce polymerized P(V) at lower temperatures (< 300 o C) 6 , 10 , 29 . For amorphous Fe-phosphate, polymerization was low (0.19%) at 350 o C 9 and moderate (2.1%) at 1150 o C (this study). On the other hand, heating apatite alone did not produce polyphosphates even at 1340 o C, which is consistent with low polymerization yield at 1150 o C in the apatite + silica control experiment. Hence, although P(V) polymerization may happen at a range of temperatures (70-1350 o C), a better yield is observed with amorphous Fe-phosphate or other metastable phosphate minerals compared stable minerals such as vivianite and apatite at low temperatures. At higher temperatures such as 1150 o C as used in our experiments, amorphous Fe-phosphate provides a better polymerization yield than apatite and vivianite. Amorphous Fe-phosphate may likely host HPO 4 instead of PO 4 tetrahedra as in apatite or vivianite, which favours the polymerization and can explain the better yield. Carbon and temperature controlled the reduction of P(V) hosted in all four minerals (Supplementary Table S5 and Fig. S7; Figs. 4 , 5 ). For magnesium phosphate, P(III) is the only reduced species that formed at 1150 o C upon addition of OM and CB while for hydroxyapatite, both P(I) and P(III) were formed. For magnesium phosphate, only CB produced P(III) with a yield of 0.003%, while for hydroxyapatite, both OM and CB produced P(III) and P(I) with a yield of 0.004 and 1.063%, respectively. At 1300 o C, the silica-hydroxyapatite-CB mixture produced P(I) and P(III) and gave a total reduction yield of 0.70%. Vivianite produced several reduced P species including P(I), P(III), PP(IV), and P-C(III) when OM and CB were added to the experiment at 1150 o C and the total reduction yield for these carbon sources were 2.9 and 29.28%, respectively. XRD suggest the presence of Fe 2 P in this CB-bearing experiment (Fig. 6 ). At 1300 o C, the silica-vivianite-CB mixture produced similar reduced P species, including P(I), P(III), P-C(III), and PP(IV) with a total reduction yield of 17.4%. Amorphous Fe-phosphate also produced several reduced P species, including P(I), P(III), P-C(III), and PP(IV) in the presence of OM and CB at 1150 o C with the reduction yields of 8.1 and 10.2%, respectively. XRD data suggest the presence of Fe 2 P in both of these amorphous Fe-phosphate experiments (Fig. 6 ). Previous studies suggested that Fe 2+ can reduce P(V) at moderate temperatures (200–350 o C); however, the reduction yield varied significantly in two separate studies (either < 0.001% 9 or 4% 8 ). Increasing temperature did enhance the reduction in one study; however, the yield was still low (0.075% at 350 o C) 9 . Even at higher temperatures explored here (e.g., 1150 o C), Fe 2+ is an ineffective P(V) reducing agent. We, therefore, suggest that C in both forms is more efficient compared to Fe 2+ to reduce P(V) in Fe-phosphate minerals, particularly at high temperatures. Addition of an Fe source enhanced the reduction and polymerization yield of hydroxyapatite-hosted P(V) (Fig. 5 , Supplementary Table S5 and Fig. S7). At 1300 o C, the silica-hydroxyapatite-CB experiment produced P(I) and P(III) with a reduction yield of 0.70%. When FeS, Fe 3 O 4 , or Fe were added to the experiment, the reduction yield increased 81.5, 96.2, and 22.7%, respectively. The FeS-bearing experiment produced P(III) and several unidentified P species. XRD data indicate the presence of schreibersite (Fe 3 P) in this experiment (Fig. 7 ). Fe 3 O 4 - and Fe-bearing experiments produced P(I), P(III), and P-C(III) and the latter one also produced PP(IV) as well as several polymerized P species including PP(V), PPP(V), and PPPP(V). XRD data suggest the presence of Fe 3 P and Fe 2 P in both of these two experiments (Fig. 7 ). FeS 2 addition produced a reduction yield of 0.076%; however, absolute concentrations of P(I) and P(III) were high compared to the silica-hydroxyapatite-CB experiment, and this experiment produced Fe 3 P, which was not the case for silica-hydroxyapatite-CB. Our data thus suggest that the Fe oxidation state (Fe 0 for metallic Fe, Fe 2+ for FeS and FeS 2 , and a mixture of Fe 2+ and Fe 3+ in Fe 3 O 4 ) and mineralogy (oxide or sulphide) did not impact phosphide formation from apatite. We suggest that apatite can be reduced extensively in the presence of any form of Fe-oxide or -sulfide by a C source (organic matter, organic or pure carbon) in the temperature range of 1100–1300 o C or higher. Discussion Geological evidence of magmatic P reduction and polymerization in the Archean There are three possible explanations for P(III) and PP(V) observed in Moodies Group intrusive and metasedimentary units. First, since the relative proportion of P(III) is similar in both rock units, it is possible that P(III) abundances were reset as a consequence of regional metamorphism consistent with previous experiments 8 , 9 and with reports of P(III) from high-grade Eoarchean metasediments 8 . P(V) reduction in such cases required water-poor conditions and higher temperatures, which is likely the case for the amphibolite grade banded iron formation rocks where P(III) is previously reported 8 . In the Moodies Group, temperatures achieved during greenschist-facies metamorphism (350 ± 50 o C; reaching up to 420–460 o C 20 ) are much lower compared to that. Furthermore, it is unknown if Fe 2+ -induced reduction of phosphate can happen inside a silicate mineral containing Fe 2+ , which is the case of the intrusive samples. In case of PP(V), the magmatic units contain a much higher concentration compared to the sedimentary units, which cannot be explained by regional metamorphism. We therefore discard the possibility of metamorphic origin of P(III) and PP(V) in Moodies intrusive and sedimentary units. Second possibility is that biological processes indirectly or directly contributed to P(III) and PP(V) observed in the sedimentary units. This would be consistent with the presence of widespread microbial mats in Moodies Group 30 , 31 . A direct biological conversion of P(V) compounds to P(III) or PP(V) is not known in the Archean 2 . Although P(III) may form indirectly due to disintegration of phosphonates produced by microbial life 32 , 33 , microbial life did not have the ability to generate phosphonate before the Great Oxygenation Event 34 . We therefore discard the possibility of a direct or indirect biologic origin for the P(III) and PP(V) in the sediments. Third possibility, which is most likely, is that P(III) and PP(V) in the intrusive bodies are of magmatic origin and that in the sedimentary units are recycled from the intrusive bodies. Previous reports of PP(V) occurrence in modern magmatic fumarole 11 , in Phanerozoic olivine samples from Hawaii and Pakistan 35 , and in experimentally produced alkali glass 36 supports the magmatic origin of PP(V). PP(V) in the Moodies intrusive bodies may be hosted in glass or in olivine. Previous studies suggested that weathering of basaltic rock in anoxic conditions favours the release of P(V) into ocean water 37 . Given that P(III) and possibly PP(V) are more soluble than P(V) 1 , similar weathering as well as hydrothermal alteration may release P(III) and PP(V) into water from the mafic igneous rocks such as those in Moodies. These species may subsequently get incorporated into sedimentary rocks. To the best of our knowledge, this is the first evidence of magmatic P(III) and PP(V) and their recycling in the Archean. Reduction and polymerization of P during thermal metamorphism and in natural conditions The contact zone samples from the Moodies Group suggest thermal induced formation of polyphosphates, but not of P(V) reduction. Experimental data suggest that P(V) polymerization is comparatively easier than reduction, as it may happen even in low temperatures (1150 o C; See Supplementary Material) and may be enhanced in the presence of carbon. In the Moodies Group, pyrite formation and biotite accumulation along the contact zones, and reworking of lithified sediment fragments into the magma, indicate that magma emplacement postdated sedimentation and thus likely heated the sediments at the contact zone. Previous studies noted diverse and widespread interactions of the mafic lava with sedimentary units at inferred temperatures of 700–1000 o C, in the Moodies Group 16 , 17 . Apatite present at the contact zones and organophosphorus compounds, the presence of which can be speculated by the presence of organic carbon and previous reports of microbial mats in sedimentary units in the Moodies Group 30 , are the most plausible P(V) source during the heating. Although we notice pyrite at the contact zones, a close association of apatite and pyrite is rare, if not absent. Based on these observations, we suggest that our OM + silica, OM + hydroxyapatite, and OM + silica + hydroxyapatite experiments (1150 o C) are the most relevant for the thermal metamorphism in the Moodies Group. These experiments produced PP(V) ranging from 0.026 to 1.81% and P(III) < 0.004%, which is consistent with the observed PP(V) (average 2.14%) and P(III) in the contact zone samples. Depending on the initial P(V) host, either simple heating or heating in the presence of organic carbon could have produced the observed PP(V) at the contact zones but the conditions were unfavourable to generate additional P(III) than existing levels. Our experimental data can explain other natural occurrences of P(V) reduction. Metallic phosphides including Fe 2 P and Fe 3 P have been reported from pyrometamorphosed rocks in the Hatrurim Formation (Levant region) and from volcanic rocks on Disko Island 13 , 14 , 38 . In those cases, organic matter or hydrocarbon was present in association with apatite as well as Fe-minerals. The country rock was heated by magmatism at temperatures above 1050 o C in the Levant region 13 and at ca. 1200-1300 o C on the Disko Island 14 . Hence, the hydroxyapatite + silica + CB + Fe-source experiments at 1300 o C broadly covers the conditions in these two places and produced similar phosphide minerals, explaining P(V) reduction in these two regions. These experiments can also explain apatite-hosted P(V) reduction in the presence of organic matter or tree-roots during lighting where temperatures reaches > 1725 o C 39 , 40 . Implications for the origin and evolution of early life Our findings carry three major implications for the origin and early evolution of life on Earth. First, experimental and Moodies Group data together suggest that high-temperature alteration of sediments containing organic carbon could have been an important mechanism of polyphosphate generation in the Archean and likely on the prebiotic Earth. Previous studies have shown that in the presence of organic compounds and urea-based eutectic solution with low water activity, apatite and other phosphate salt can produce polymerized species at relatively mild conditions 18 , 41 ; however, geological evidence of such organic compounds is yet to be discovered. In absence of these organics, high-temperature thermal induced processes shown in this study, could have been crucial for making polymerized P species. Second, the Moodies Group data suggest that magmatic rocks could have been an important, long-term, and stable source of P(III) and PP(V) along with P(V) on the prebiotic Earth and in the Archean. Although the total amounts of P(III) and PP(V) in the studied basaltic rock are in the low ppm range (2.84 and 1.65 ppm), they are more water-soluble than P(V) 1 , implying that anoxic weathering and hydrothermal alteration of these rocks could have liberated them more efficiently than P(V) to the ocean. Previous studies argued in favour a significant amount of P(III) along with P(V) in the Archean ocean, which has been attributed to dissolution of phosphide delivered by meteorite and produced by lightning strike 15 . We suggest that part of the Archean seawater P(III) could have been delivered by ocean-floor weathering and hydrothermal vents. The half-life of P(III) under Archean conditions has been estimated to 0.6 Ma while that of PP(V) may have much lower 6 , 8 , 42 ; both of them eventually would convert into P(V). Therefore, these species could have contributed to bioavailable P(V) in the Archean ocean. Third, although the Moodies Group represents a volcano-sedimentary succession in shallow-marine and coastal depositional settings, our experimental results are applicable to prebiotic volcanic lakes and hot-spring environments, where thermal metamorphism or magma-sediment interaction could have taken place. In these settings, organic C species may have been generated abiotically by volcanism or lightning strikes and/or delivered by meteorites 43 , 44 and accumulated in the lakes and pools along with phosphate minerals and metal oxides and sulphides 9 , 18 . Here, volcanism was common due to a significantly higher heat flux than today, driven by the combined effects of a hotter mantle and residual heat from planetary accretion 45 , 46 , and basalt and komatiite were likely the most abundant rocks 47 . Because eruption temperatures of the latter exceeded in places 1600 o C 48 , sediments in contact with komatiitic magmas would have readily achieved temperatures approaching those in our experiments (1150 and 1300 o C) or higher. Similarly, the ingredients used in the experiments, i.e., P(V) source, C, Fe-oxide/-sulphide, and heat, are also relevant to impact events and lightning strikes, which were likely common on prebiotic Earth 28 , 40 and known to create temperatures as high as > 1700 o C 49 . We therefore suggest that there might be several local niches on the prebiotic Earth where P(V) hosted in so-called ‘un-reactive’ minerals such as apatite and vivianite, could potentially have been transformed into phosphides, as seen in our experiments. The presence of phosphides in thermal metamorphic rocks in the Levant region and on Disko Island 13 , 14 and in lightning-stroke soil 39 , 40 further suggests the natural relevance of this reduction mechanism. Once produced such phosphide may dissolve in water and produce the reduced and polymerized P species as seen in our experimental products including P(I), P(III), P-C(IIII), PP(IV), PP(V), PPP(V), and PPPc(V), which are more reactive compared to P(V). Because of high solubility and better reactivity, these species are better phosphorylating agent or organic molecules 2 , 5 and thus crucial for the origin of life. Furthermore, phosphides may directly phosphorylate nucleosides and other organic compounds as well 15 , 50 . This reduction mechanism plausibly operated at local scale on the prebiotic Earth, particularly when the criteria for P(V) reduction was fulfilled but such local supply of reactive P species may have been sufficient to trigger phosphorylation reactions required for the origin of life. In summary, we provide geological evidence of magmatic and thermal-metamorphic polyphosphate production and magmatic phosphite during the Archean and suggest that weathering and hydrothermal alteration of magmatic rocks can be a stable source of reactive and bioavailable P to Archean seawater. Our data suggest that P(V)-polymerization at high temperatures can be facilitated by the presence of organic carbon. Organic carbon might be an important reducing agent at temperatures > 1150 o C for P(V) hosted in so called ‘unreactive’ minerals such as vivianite and apatite producing phosphides, that upon dissolution can provide several soluble and reactive P species, including P(I), P(III), P-C(IIII), PP(IV), PP(V), PPP(V), and PPPc(V) crucial for prebiotic phosphorylation reactions. In conclusion, both magmatic and carbon-bearing thermally metamorphosed rock might have played important roles in supplying reactive and soluble P species during the origin and early evolution of biosphere. Methods and Materials Whole rock analysis and TOC measurements Powders (0.60 g each) of all samples were sent to Australian Laboratory Services (ALS) in Dublin, Ireland, for whole-rock geochemical characterisation using their method ME-MS-61r of four-acid digestion (HCl, HNO 3 , HF, HClO 4 ) followed by ICP-MS and ICP-AES analyses. Reproducibility was assessed with rock standards OREAS-45d, OREAS-905, and MRGeo-08, and with sample replicates. For P, Fe, Cr, and Ti, the reproducibility was 5% or better. Total organic carbon (TOC) was measured at the University of St Andrews on decarbonated rock powders. Circa 0.5 g of powder were treated with 2M HCl overnight at room temperature, followed by triple-rinsing with 18.2 MΩ·cm ultrapure water and drying in a sealed oven for three days. The dried powders were then analyzed by flash-combustion with an elemental analyzer (EA-Isolink) coupled to an IRMS (MAT253, both Thermo Fisher Scientific). Peak areas were calibrated for carbon abundances. Reproducibility is better than 5%. Bacteria biomass and culture conditions Bacteria biomass (OM) used as a C source in the dry-heating experiments was generated from phosphate replete cultures of both nitrogen fixing (diazotrophic) and non-nitrogen fixing strains of cyanobacteria. The cyanobacterial diazotrophs included the freshwater Calothrix PCC7507 (Pasteur Culture Collection) and Nostoc sp., which were cultured in nitrogen-free BG11 0 medium 51 and the brackish dwelling strains Nodularia spumigena CCY 9414 (obtained from Lukas Stal, Culture Collection Yerseke, The Netherlands), and Nodularia harveyana SAG 44.85 (Culture Collection of Algae, Göttingen University), grown in Baltic Sea medium (Ba 0 ) lacking a combined nitrogen source 52 . Freshwater species Microcystis aeruginosa PCC7806 and PCC9432 were grown in nitrate containing BG11 medium 51 . An inoculum of exponentially growing culture material was used to inoculate 100 ml of the appropriate medium in T 175 ventilated cell culture flasks (Sarstedt, Germany) at a concentration of chlorophyll a of ~ 0.1 µg.ml − 1 and incubated at 24°C, 60 µmol photons m − 2 s − 1 on a 14:10 hour day-night cycle, under present day atmospheric conditions (Plant growth chamber E-22L, Percival, USA). Biomass was harvested after 4–6 weeks once the cultures had reached stationary phase 51 , 52 . Cultures were pelleted in sterile 50 ml polypropylene tubes (Sarstedt, Germany) by centrifugation at 7 500 rcf for 30 min., washed twice with sterile MQ water and frozen at -80°C. The pellets were lyophilized (at -10°C, 0.04 mbar; CHRIST LSC plus) and the dried biomass powdered using an agate mortar and pestle. The final mixture of biomass (referred to as OM in the main text) includes 0.26 g Calothrix PCC7507, 0.17 g N. harveyana , 0.19 g Nostoc , 0.18 g N. spumigena , 0.70 g M. aeruginosa PCC7806, and 0.67 g M. aeruginosa PCC9432. While these particular diazotrophs are not representative of deep branching cyanobacteria, their OM was not found to significantly vary with respect to C and N contents, nor stable isotope signatures, when grown under anoxic conditions simulating those on early Earth, present-day atmospheric conditions, nor under elevated atmospheric CO 2 conditions 52 . The OM thus used in these experiments can be considered as an Archean equivalent of organic-carbon-containing matter. Heating experiments All experiments and associated analyses were carried out at the University of St Andrews. Acid-washed (1M or 2M HCl) and baked (500°C) glass containers and acid- and hot-water (18.2 MΩ·cm, ultrapure) washed plastic centrifuge tubes, bottles, pipette tips, and syringes were used in all the stages of the experiments and subsequent sampling. Synthetic hydroxyapatite (Ca 5 (PO 4 ) 3 (OH); Thermo Scientific; Cat. No. 036731.36, Lot. X15F024) and magnesium phosphate (Mg 3 (PO 4 ) 2 ·xH 2 O; Sigma-Aldrich; PCode 1002982444), natural vivianite (Brazil), and in-house amorphous Fe-phosphate were used as a P(V) precursor. To prepare amorphous Fe-phosphate, FeCl 2 ·4H 2 O (Sigma Aldrich, PCode 101074277) and (NH 4 )H 2 PO 4 , (Thermo Scientific; Cat No. 193701000, Lot A0443028) were added in a molar ratio of 3:1 in 300 ml deoxygenated, deionized water (18.2 MΩ·cm) with a pH of 4 (this method is adopted from Herschy et al. 8 and Baidya et al. 9 ). The glass bottle was connected to a vacuum pump and N 2 cylinder for maintaining an anoxic condition and a hot plate for increasing temperature. The solution was stirred in the dark (shielded with Al foil), evaporated into dryness maintaining anoxic conditions at 60 o C, and the solid residue was brought back to room temperature. The residue was crushed with pestle & mortar, stored in a sealed vial, and used as a P(V) precursor for subsequent heating experiments. OM as described above and carbon black from Cabot were used as a C source. Metallic Fe (Thermo Scientific, Cat. No. 000737.30, Lot. R20F039), Fe 3 O 4 (Inoxia Limited (UK); EC 215-169-8), FeS (Thermo Scientific; Cat No. 014024.09, Lot. T07H028) and FeS 2 (natural; Thermo Scientific; Cat. No. 042633.06, Lot. T23G054) were used as an Fe-source in selected apatite-bearing experiments. Additionally, SiO 2 powder (crushed Sea sands, VWR, CAS 14808-60-7) was used to prepare the initial mixture. For each experiment, 0.6 g of powdered mixture was prepared by mixing 0.18 g of one of the phosphate sources, 0.18 g of one of the C sources, variable proportions of powdered SiO 2 , and in some cases, a Fe source using a pestle & mortar (Supplementary Table 1). The weight ratio for C and P(V) was 1:1 except for the control experiments. Variable weights of Fe precursors were used to maintain the total Fe added in each experiment the same. As an example, in Exp 8, 0.18 g of hydroxyapatite, 0.18 g of OM, and 0.24 g of silica powder were mixed. For control experiments containing only SiO 2 powder, 0.6 g od SiO 2 powder was used while those containing SiO 2 powder and a P(V) source or silica powder and a C source, 0.18 g of C or P(V) source was mixed with 0.42 g of SiO 2 . 0.52–0.56 g of the powder mixtures were pelted, each pellet containing 0.13–0.14 g of powder mixture. The pellets were then loaded into an alumina boat and kept inside a tube furnace under flowing N 2 gas (30 ml/minute) at room temperature for 3 hours. This step was done to make sure the gas inside the tube is inert before the heating stage started. The furnace was equipped with a K-type thermocouple and a temperature controller. A forward ramp of 7–8°C/min was used to reach the desired temperatures i.e., 1150 o C or 1300 o C, which was maintained for 48 hours, followed by a downward ramp of 5°C/min (Supplementary Fig. S1 B). The heated residues were brought back to room temperature while maintaining the same N 2 flow rate. They were then powdered and stored in sealed vials before subsequent analysis. Solid characterization using powder X-ray diffraction (PXRD) An aliquot of the powdered experimental products was loaded into 0.5- or 0.7-mm capillary tubes and sealed for XRD analysis. The PXRD patterns were recorded on a STOE STADIP diffractometer using Mo Kα1 radiation at room temperature from 2.5 o to 40° (2θ) with a scan rate of 2.75 o (2θ)/step in capillary Debye-Scherrer mode. The PXRD data were compared to solids in the Inorganic Crystal Structure Database (ICSD) and Crystallography Open Database (COD) for phase identification using the Crystal Diffract software (version 7.0.4.300). NMR and IC-ICPMS analysis for P speciation The P speciation analysis for the rock samples were done using an ion chromatography-inductively coupled plasma mass spectrometer (IC-ICPMS) set-up at the University of St Andrews 19 . For the experimental samples, both nuclear magnetic resonance (NMR) spectroscopy and IC-ICPMS were used. It is important to note that NMR has higher detection limits (150–200 ppb) for P species in the used analytical conditions while the IC-ICPMS set-up can detect as little as 0.1 ppb of P species in solution. Furthermore, NMR can detect several P species while only inorganic P(I), P(III), P(V), and PP(V) can be detected in the IC-ICPMS set-up. For each rock sample, 0.20 g powder was treated with an Ethylenediaminetetraacetic acid-sodium hydroxide (0.05M EDTA and 0.25M NaOH) solution 53 maintaining a solid:solution ratio of 1:10, 1:5, or 1:3.75. As the total concentration of P species, particularly P(III) and PP(V), in the rock samples were low, three different solid:solution ratios were chosen. For preparing the EDTA-NaOH solution, Na 2 EDTA (Sigma Aldrich) salt and 10M NaOH solution (Thermo Scientific) were dissolved in deionized water. The solid and solution mixture were prepared in 15 ml Falcon tubes (acid- and hot-water washed) and left on a shaker (175 rpm/minute) for 14–15 hours. The solid-solution mixtures were then centrifuged at 3000 rpm for 15 minutes. For the metasedimentary and contact zone samples, a floating grey phase was observed in the supernatant, which most likely is organic carbon. For these samples, the supernatant was filtered by 0.20 µm PTFE syringe filter (Fisherbrand). A transparent solution at this stage suggests the precipitation of all the extracted Fe and other transition metals. Precipitation of these metals is essential for the P speciation measurements using the subsequent IC-ICPMS analysis 19 because excess dissolved metal may precipitate as oxides in the anion separation column of the IC and bind phosphate by adsorption within the column, thereby impacting analytical quality. The supernatant was then diluted 25 or 50 times and P species analysis was done using the IC-ICPMS set-up. For each experimental sample, 0.1 g of powder was treated with 1ml of EDTA-NaOH solution for 8 hours. A 4 ml, flat-bottom glass vial with a magnetic stirrer was used for this step. After this, the supernatant was filtered with 0.20 µM PTFE syringe filter (Fisherbrand). The solution was then diluted 25, 50, or 75 times and analyzed with IC-ICP-MS. An aliquot of the solution was analysed with an NMR. The IC-ICPMS set-up consisted of a Dionex ICS-6000 ion chromatograph (IC) and an Element 2 inductively coupled plasma mass spectrometer (ICP-MS) (both from Thermo Scientific). The IC was equipped with a Dionex AS-AP autosampler, a 25 mm Dionex IonPac AS17-C separation column (2 mm bore), a 25mm Dionex IonPac AG17-G guard column (2 mm bore), and a Dionex ADRS-600 (2 mm) suppressor. The flow rate in the IC was held constant at 0.5 ml/min. The concentration of the KOH eluent solution was ramped up from 1 mM to 40 mM over 20 minutes, which was then maintained for another 24 minutes followed by a ramp-down to 1 mM in 6 minutes. The detector outlet of the IC was physically connected to a 1 ml/min nebulizer attached to the spray chamber (Scott model; quartz glass) of the ICP-MS. The ICP-MS was operated at a sample gas flow rate of 1.03–1.10 ml/min, cool gas flowrate of 16 ml/min, and RF power of 1183 in medium-resolution mode. Data were collected in the ICP-MS as chromatographs of 3 minutes duration. Each chromatogram consisted of the pre-peak background, the peak, and the post-peak background for each P-species. The chromatographic data were produced for samples and standards. Standards contained 0.2 to 100 ppb of four P species (prepared from NaH 2 PO 2 .H 2 O (Thermo Fisher), Na 2 HPO 3 ·5H 2 O (Thermo Fisher), NaH 2 PO 4 (Thermo Fisher), and Na 4 P 2 O 7 (Sigma Aldrich)) in a solution matrix similar to the samples. The acquired chromatogram data were smoothened with the OriginLab software, using the FFT filter with a points-of-window value of 5, and the peak area under the curve was used for quantification. The detection limits of the IC-ICPMS set-up were < 0.1 ppb for P(III) and P(V), 0.1 ppb for P(I), and 0.2 ppb for PP(V). Analysis was done twice or thrice, and the geometric mean was calculated due to large variations in the replicates. For NMR analyses, an aliquot (540 µL) of EDTA-NaOH extracts of the experimental samples was mixed with 60 µL of D 2 O and loaded in an NMR tube to be measured on a Bruker AVIII 500 MHz NMR. This NMR set-up is equipped with a nitrogen-cooled broadband cryoprobe, which improves sensitivity. Samples were analyzed in proton-decoupled mode with 15000 scans. The 31 P chemical shifts were referenced to phosphoric acid, which has a chemical shift of 0δ. Standards containing six different P species, P-C(III), P(I), P(III), P(V), PP(V), PPP(V), PPPc(V) of known concentrations (0.2 ppm to 800 ppm phosphorus), prepared using NaH 2 PO 2 .H 2 O (Thermo Scientific), Na 2 HPO 3 ·5H 2 O (Thermo Scientific), NaH 2 PO 4 (Thermo Scientific), and Na 4 P 2 O 7 (Sigma Aldrich), Na 5 P 3 O 10 ,(Thermo Scientific), and Na 5 P 3 O 9 (Thermo Scientific) were analysed to build calibration curves for each P species. The experimental samples contained PPPP(V) or even longer-chain polyphosphates as well as several unknown P species. For PPPP(V), the calibration curve of PPP(V) was used; for the unknown P species, the calibration of P(V). Declarations Acknowledgements This work was financially supported by a Natural Environment Research Council (NERC- UKRI) Frontiers grant to EES (NE/V010824/1), a Marie Skłodowska-Curie Actions grant to ASB (EP/Y026497/1), and a German Research Foundation (DFG) grant (GE2558/4-1) to MMG. We acknowledge Sami Mikhail for his help during pellet making and Tomas Lebl and Siobhan Smith for their help during the NMR analysis. Rajan Biswas and Oxana Magdysyuk helped during XRD analyses and data interpretation. For XRD analyses, we also acknowledge the Engineering and Physical Science Research Council (EPSRC) Core Equipment Grant (EP/V034138/1). ICDP staff provided access to core and administration of the sample database. Sebastian Reimann drafted the geologic map. South Africa’s Council for Geoscience supplied the hyperspectral core maps shown in Fig. S1. The complete data for this study are available through the National Geoscience Data Centre of the British Geological Survey. In order to meet institutional and research funder open-access requirements, any accepted manuscript arising shall be open access under a Creative Commons Attribution (CC BY) reuse licence with zero embargo. Author contributions The idea is conceived by EES and ASB. 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Supplementary Files SupplementaryMaterial.docx Supplementary Material DataS1XRD.zip Data S1 - XRD DataS2NMRdata.zip Data S2 - NMR DataS3AdditionalGeologicalMaps.zip Data S3 - Additional Maps Cite Share Download PDF Status: Published Journal Publication published 13 Nov, 2025 Read the published version in Communications Earth & Environment → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6529805","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":453170716,"identity":"32fd2f83-006b-4f2d-88b8-5facc570ed70","order_by":0,"name":"Abu Baidya","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA80lEQVRIie2RsWrDMBCGLwiSRUXreUlfQaZQyKRXsTFkMp49GCMvXvMCJo/hWUbgLjZZXbykBDp56N7S1sZDhxAl3TLom47jPv47DsBiuUvo4vQVzyX+dZVRIZw28/TNyhIf8v8obNcqdPZpCqu26uNYC1jpIxlzL4Jd5HG31Ag0CjZNo31Jt5zQzrBXR7nnlwqFCp+dLO89gBAI/bhsPB4arqoiRWDDqHz3YizMClehm2WSIOCUIvuFxCnFsJjbRQGBWjsSh6eNrH/8HN95VRjOXx/al09IUgYsdF9lshWMBW/HoTacf8YSrjzSYrFYLNf5BV+HTrndNoj2AAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0001-8894-8813","institution":"University of St. Andrews","correspondingAuthor":true,"prefix":"","firstName":"Abu","middleName":"","lastName":"Baidya","suffix":""},{"id":453170717,"identity":"852fe382-c2ec-46b7-8233-52dc01ee1ee7","order_by":1,"name":"Michelle Gehringer","email":"","orcid":"https://orcid.org/0000-0002-4982-2465","institution":"RPTU University Kaiserslautern Landau","correspondingAuthor":false,"prefix":"","firstName":"Michelle","middleName":"","lastName":"Gehringer","suffix":""},{"id":453170718,"identity":"701632e4-a105-4ec0-94f9-568a99e3d401","order_by":2,"name":"Cristian Savaniu","email":"","orcid":"","institution":"University of St Andrews","correspondingAuthor":false,"prefix":"","firstName":"Cristian","middleName":"","lastName":"Savaniu","suffix":""},{"id":453170719,"identity":"71949154-bb24-41eb-a796-84d8c3c06492","order_by":3,"name":"Christoph Heubeck","email":"","orcid":"","institution":"Archean geology and tectonics","correspondingAuthor":false,"prefix":"","firstName":"Christoph","middleName":"","lastName":"Heubeck","suffix":""},{"id":453170720,"identity":"489213e4-60c8-4af9-a659-5d937f0b2edc","order_by":4,"name":"Eva Stüeken","email":"","orcid":"https://orcid.org/0000-0001-6861-2490","institution":"University of St Andrews","correspondingAuthor":false,"prefix":"","firstName":"Eva","middleName":"","lastName":"Stüeken","suffix":""}],"badges":[],"createdAt":"2025-04-25 14:26:43","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6529805/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6529805/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s43247-025-02824-x","type":"published","date":"2025-11-13T05:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":83629265,"identity":"054b4d1b-b9c5-416d-876e-75c74c9cf51c","added_by":"auto","created_at":"2025-05-29 18:18:40","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":269005,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eGeological map of the study area and schematic diagram of the sampled core.\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e A. Geological map of the Barberton Greenstone Belt, South Africa, modified from Homann et al.\u003c/em\u003e\u003csup\u003e22\u003c/sup\u003e\u003cem\u003e. The Eureka Syncline is a large, refolded syncline in the north-central BGB. Stratigraphic column to the right shows generalized lithology of the Moodies Group in the Saddleback Syncline which preserves the greatest stratigraphic thickness of this unit. Gray box (dashed line) in the stratigraphic column shows the sampled section. B. Schematic stratigraphic column of the sampled section showing locations of the samples along with their specific depths. Note that the stratigraphy is overturned in core BASE 1A; drilling depth thus increases stratigraphically up. Supplementary Table S1 contains further information on sample positions.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6529805/v1/c8ce17dc34b0f414368fa8bb.jpeg"},{"id":83629281,"identity":"392fd765-cbc8-4440-a367-7914051ebcac","added_by":"auto","created_at":"2025-05-29 18:18:44","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":843493,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eTextural features of Moodies Group core BASE-1A.\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e A-C, D-F, and G-I are hand specimen, optical microscopic, and back-scattered electron images, respectively. A, D, and G (sample no. B20) show textures in metasedimentary strata. They contain apatite and lack visible alteration. B, E, and H (sample no. B13) illustrate textures of the contact zone and a close interaction between the intrusive and the metasedimentary strata. C, F, and I (sample no. B23) show textures of the intrusive unit, which shows no alteration. Sample depths are provided in Supplementary Table 1.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6529805/v1/d23f19f73398776ec8872302.jpeg"},{"id":83629262,"identity":"85ab3a0e-4235-4461-ab9a-ed65833b1e30","added_by":"auto","created_at":"2025-05-29 18:18:40","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":204047,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eConcentrations of different P species and TOC in studied samples from the Moodies BASE-1A borehole.\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e Concentrations of P(III), P(V), and PP(V) are measured with the IC-ICP-MS set-up while total P and TOC contents are measured by ICP-MS and IR-MS, respectively. The presented concentrations of different P species (B-D) represent estimated concentrations in samples. In B-D, geometric means of P(III), P(V), and PP(V) are plotted due to large variations in the acquired data. Percentages of different P species in total extracted P (in EDTA-NaOH) are shown in F-H. These ratios are presented as averages and as their standard deviations (grey line). The red dotted lines represent conservative mixing lines of the intrusives and metasediments. Generally, where the contact zone sample data fall on that line, intrusive magma and sediments (or sedimentary rocks) may have physically mixed, e.g., P(III) in G.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6529805/v1/8418804ca221d58b5897baf0.jpeg"},{"id":83629267,"identity":"1e815a44-99e1-407e-9658-1141316ebc40","added_by":"auto","created_at":"2025-05-29 18:18:40","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":298003,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eNMR spectra of end products from vivianite and amorphous Fe-phosphate experiments. \u003c/strong\u003e\u003c/em\u003e\u003cem\u003eAll the experiments were performed at 1150 \u003c/em\u003e\u003csup\u003e\u003cem\u003eo\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eC except for the top Viv+SiO\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e+CB experiment which was done at 1300 \u003c/em\u003e\u003csup\u003e\u003cem\u003eo\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eC. In general, addition of C in either forms, i.e., CB and OM, produced several reduced and polymerized P species.\u003c/em\u003e\u003cem\u003e\u003cstrong\u003e \u003c/strong\u003e\u003c/em\u003e\u003cem\u003eMinor shifts in P(V) and other peaks are due to minor differences in pH of the solution.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6529805/v1/fa28ab018e2180b0eb8c0e9f.jpeg"},{"id":83629264,"identity":"477bb26d-3591-43d5-8131-fa2407fd84fe","added_by":"auto","created_at":"2025-05-29 18:18:40","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":370212,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eNMR spectra of experimental products containing apatite\u003c/strong\u003e\u003c/em\u003e\u003cem\u003e. Experiments were conducted at 1300 \u003c/em\u003e\u003csup\u003e\u003cem\u003eo\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eC except for the bottom three experiments that were conducted at 1150 \u003c/em\u003e\u003csup\u003e\u003cem\u003eo\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eC. Addition of an iron source to a mixture of apatite, silica, and CB produced several reduced and some polymerized P species.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6529805/v1/26d90e19df75a825c228ba71.jpeg"},{"id":83629272,"identity":"54f1108f-698e-44e1-a829-bfb985860d2f","added_by":"auto","created_at":"2025-05-29 18:18:40","extension":"jpeg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":287600,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eXRD patterns of the products from amorphous Fe-phosphate and vivianite experiments. \u003c/strong\u003e\u003c/em\u003e\u003cem\u003eBarringerite (Fe\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eP) is detected in two amorphous Fe-phosphate-bearing experiments in the presence of C (OM and CB). This phosphide is possibly present as a minor phase in the vivianite-CB-bearing experiments at 1150 and 1300 \u003c/em\u003e\u003csup\u003e\u003cem\u003eo\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eC.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6529805/v1/258690f1385ac02ad0465465.jpeg"},{"id":83629684,"identity":"eb4db56d-0d72-4519-bf09-0f8f56966e18","added_by":"auto","created_at":"2025-05-29 18:26:40","extension":"jpeg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":353276,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003e\u003cstrong\u003eXRD patterns of the products from hydroxyapatite experiments. \u003c/strong\u003e\u003c/em\u003e\u003cem\u003eHydroxyapatite is not present in the Fe-bearing experiments at 1300 \u003c/em\u003e\u003csup\u003e\u003cem\u003eo\u003c/em\u003e\u003c/sup\u003e\u003cem\u003eC. Both schreibersite (Fe\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eP) and barrigerite (Fe\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003eP) or only schreibersite is present in Fe-bearing experiments.\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage7.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-6529805/v1/8f60c3d5266e2bde1059eede.jpeg"},{"id":95900082,"identity":"bc5c589e-c9ed-4ae8-a257-c2e97f78a514","added_by":"auto","created_at":"2025-11-14 08:10:57","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3582297,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6529805/v1/20278a38-76e3-4291-b718-b400ce705230.pdf"},{"id":83629270,"identity":"897d3200-df6b-43d6-b85f-8c2408f8dbf2","added_by":"auto","created_at":"2025-05-29 18:18:40","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":4590675,"visible":true,"origin":"","legend":"Supplementary Material","description":"","filename":"SupplementaryMaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-6529805/v1/2cf3e84ed351ef639439cac2.docx"},{"id":83629682,"identity":"322bccc5-da9b-47d7-acd1-48a299798002","added_by":"auto","created_at":"2025-05-29 18:26:40","extension":"zip","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":135119,"visible":true,"origin":"","legend":"Data S1 - XRD","description":"","filename":"DataS1XRD.zip","url":"https://assets-eu.researchsquare.com/files/rs-6529805/v1/c21a74323b07814685acc6f9.zip"},{"id":83629280,"identity":"6e3a47e5-9b72-49ce-9555-47afbbe1d047","added_by":"auto","created_at":"2025-05-29 18:18:41","extension":"zip","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":19374480,"visible":true,"origin":"","legend":"Data S2 - NMR","description":"","filename":"DataS2NMRdata.zip","url":"https://assets-eu.researchsquare.com/files/rs-6529805/v1/2a8016071bde9bdb45294f34.zip"},{"id":83629282,"identity":"ebcd5e8f-4cc6-46dd-926f-1e13c2978441","added_by":"auto","created_at":"2025-05-29 18:18:44","extension":"zip","order_by":4,"title":"","display":"","copyAsset":false,"role":"supplement","size":8243225,"visible":true,"origin":"","legend":"Data S3 - Additional Maps","description":"","filename":"DataS3AdditionalGeologicalMaps.zip","url":"https://assets-eu.researchsquare.com/files/rs-6529805/v1/5649c6b6b220f001f7a06899.zip"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Magmatic phosphite and thermally polymerized phosphate 3.2 billion years ago: Implications for early life","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePhosphorus is a key element for modern biological systems and has likely played an important role in the origin of life on our planet\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. Unlike other major elements (C, H, O, N, S) required for the origin of life, P does not have a stable gaseous phase, is less abundant, and is locked in solid rocks in its most abundant form, phosphate (P(V), where P has an oxidation state of +\u0026thinsp;5). Furthermore, P(V) is only weakly reactive towards organic compounds, which could have hindered abiotic phosphorylation of biomolecules. The low solubility and low reactivity of P(V) thus raise questions on the journey of P from rock to life - a conundrum that has become known as the \u0026lsquo;P-problem\u0026rsquo;\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eReduced and polymerized P species have been proposed to solve the \u0026lsquo;P-problem\u0026rsquo;\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. Polymerized P species (also known as condensed P), including pyrophosphate (PP(V)), triphosphate (PPP(V)), tetra- and other higher-order phosphates (PPPP(V)), and cyclophosphates such as trimetaphosphate (PPPc) are more reactive than unpolymerized P(V) and, therefore, may have facilitated phosphorylation on the prebiotic Earth. The simplest polyphosphates is dimer PP(V), which could have been a phosphorylating agent\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e, a source of ATP-based metabolism, and a potential energy source for early life\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. Similarly, cyclophosphates may phosphorylate several organic compounds including glyceric acid, sugars, amino acids, and nucleosides\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e. Thermal processes in metamorphic and magmatic environments have been proposed to produce polyphosphates, such as (1) dry-heating of sodium or ammonium phosphate salt (e.g., NaH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e/NH\u003csub\u003e4\u003c/sub\u003eH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e) and rare minerals (whitlockite (Ca\u003csub\u003e18\u003c/sub\u003eMg\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e14\u003c/sub\u003e), newberyite (MgHPO\u003csub\u003e4\u003c/sub\u003e\u0026middot;3H\u003csub\u003e2\u003c/sub\u003eO), struvite (MgNH\u003csub\u003e4\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO), brushite (CaHPO\u003csub\u003e4\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO), and amorphous Fe-phosphate at 80\u0026ndash;600\u0026deg;C, especially in the presence of urea and other organics or Fe-Cr-Ni-bearing minerals\u003csup\u003e\u003cspan additionalcitationids=\"CR7 CR8 CR9\" citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e; and (2) partial dissolution of P\u003csub\u003e4\u003c/sub\u003eO\u003csub\u003e10\u003c/sub\u003e produced in high-temperature (\u0026gt;\u0026thinsp;1200\u0026deg;C) volcanic processes\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. Volcanic fumaroles in modern-day Japan and 2.5\u0026ndash;14 Myr-old contact-metamorphic rocks from the Levant region have been shown to contain polyphosphates\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. However, there is so far no geological record of polyphosphates older than the Miocene, so the validity and importance of thermal or magmatic formation of polyphosphates in early Earth history is not known.\u003c/p\u003e \u003cp\u003eReduced P species such as phosphite (P(III), oxidation state of 3+), hypophosphite (P(I), oxidation state of +\u0026thinsp;1), and phosphonate (molecules with P-C bonds and P with a 3\u0026thinsp;+\u0026thinsp;oxidation state) are more soluble than P(V) in the presence of bivalent metals such as Ca and Fe\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. Furthermore, they are more reactive than P(V). For example, P(III) is ca. 1,000 times more soluble than P(V) in natural fluids including seawater and more efficient than P(V) in forming organophosphorus compounds\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. P(I) is even more reactive than P(III), and P-C compounds already contain P-C bonds, suggesting that these reduced P species may act as more efficient phosphorylating agents than P(V). Thermal processes have been proposed as important routes to form reduced P species, such as metamorphic heating of phosphate in the presence of Fe\u003csup\u003e2+\u003c/sup\u003e, H\u003csub\u003e2\u003c/sub\u003e and/or organic matter\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan additionalcitationids=\"CR14\" citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. However, these studies use sodium and ammonium phosphate as a precursor, which may not be relevant for early Earth as these salts do not readily form in nature\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e\u003c/sup\u003e. Therefore, the underlying mechanism of P(V) reduction, particularly P(V) hosted in naturally occurring minerals such as apatite and vivianite that are considered less reactive, is not well understood. Importantly, only one study has documented P(V) reduction by metamorphic conditions in the Precambrian, specifically in seven Eoarchean carbonates and iron formation samples of amphibolite to granulite metamorphic grade\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Therefore, the importance of thermal P(V) reduction on the early Earth is so far poorly constrained.\u003c/p\u003e \u003cp\u003eTo explore the effect of heat on P speciation in the Archean, we turned to the Paleoarchean Moodies Group (ca. 3.2 Ga) of the Barberton Greenstone Belt in South Africa, where mafic intrusions invaded into shallow-marine biomass-bearing sedimentary rocks \u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e, providing an ideal test bed for exploring if P polymerization and/or reduction could occur under Archean thermal metamorphic conditions. We collected 5 samples from metasedimentary units, 2 from intrusive units, and 4 from the contact zones between them and measured the concentrations of P(I), P(III), P(V), and PP(V), along with major and minor elemental abundances (see Methods). To validate our findings in Moodies Group and previous findings of phosphate reduction in other locations (e.g., the 2.5\u0026ndash;14 Ma old Levant region and 60 Ma old Disko Island), we additionally performed laboratory experiments that replicated thermal metamorphism of biomass- and P-bearing sediments. We chose four prebiotically relevant P(V) minerals, namely, hydroxyapatite ((Ca\u003csub\u003e5\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e(OH)), magnesium phosphate (Mg\u003csub\u003e3\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;xH\u003csub\u003e2\u003c/sub\u003eO);, vivianite (Fe\u003csub\u003e3\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;8H\u003csub\u003e2\u003c/sub\u003eO), and amorphous Fe-phosphate (Fe\u003csub\u003e3\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;xH\u003csub\u003e2\u003c/sub\u003eO)\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e and two different C sources, namely carbon black (CB) and bacterial biomass (hereafter OM for \u0026lsquo;organic matter\u0026rsquo;). We mixed the P(V) source, C source, and silica powder (mimicking very fine-grained sand), pelleted them, and heated them up at 1150 \u003csup\u003eo\u003c/sup\u003eC or 1300 \u003csup\u003eo\u003c/sup\u003eC in an anoxic environment. The experimental products were analyzed by powder X-ray diffraction for phase identification. Phosphorus species were extracted from the experimental products using an Ethylenediaminetetraacetic acid-sodium hydroxide solution and measured using an IC-ICPMS\u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e and NMR. Collectively, our data have implications for prebiotic P chemistry as well as for the origin and early evolution of life on our planet.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eGeological Setting\u003c/p\u003e \u003cp\u003eWe investigated the contact zones of Paleoarchean metasedimentary siliciclastic rocks intruded by mafic dikes in the north-central Barberton Greenstone Belt, South Africa (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA). Samples were obtained from borehole BASE-1A, drilled within the framework of the ICDP BASE (Barberton Archean Surface Environments) project, which obtained continuous and unweathered core from the ca. 3.2 Ga Moodies Group (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB, Supplementary Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e-2). These are among the oldest well-preserved sedimentary rocks on Earth. The regional metamorphic grade is lower-greenschist facies with maximum temperatures of 420-460\u003csup\u003eo\u003c/sup\u003eC, as indicated by Raman spectroscopy of carbonaceous matter (RSCM)\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eSyn- and post-depositional magmatic activity affected Moodies Group strata. The most noteworthy event is the emplacement of the Moodies lava, a ca. 20\u0026ndash;400 m thick complex of basaltic amygdaloidal lavas approximately midway in the Moodies stratigraphic column, widely overlain by dacitic air-fall tuffs dated at 3219\u0026thinsp;\u0026plusmn;\u0026thinsp;9 Ma, 3222\u0026thinsp;\u0026plusmn;\u0026thinsp;8 Ma, and 3228\u0026thinsp;\u0026plusmn;\u0026thinsp;8 Ma (LA-ICP-MS U-Pb ages of zircon\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e). An eruption age of about 3224 Ma is also consistent with a growing body of related age dates in the Moodies Group\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. In stratigraphically correlatable Moodies Group strata in the central Barberton Greenstone Belt ca. 11 km to the south and southwest of the BASE-1A drill site, large mafic laccoliths occur, surrounded by halos of thermally altered Moodies sandstone and mafic stockwork dikes that apparently intruded in unconsolidated Moodies sands, resulting in local peperites\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. Stratigraphic and geochronologic data indicate that stockwork dikes connect the sills, ca. 2 km below the paleosurface, with the Moodies lava, although no mappable connection has been documented yet. Stratiform mafic dikes, sills and thin lava flows were also encountered by borehole BASE-2A, ca. 7 km to the south of the BASE-1A location. Thermal alteration of sandstones was noted in borehole BASE-4B, ca. 14 km to the SSW. This alteration is probably the result of a nearby bedding-parallel-trending feldspar-porphyritic dike\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. The diverse nature of (sub-)volcanic contributions to the Moodies Group sedimentary environments was summarized by reference\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. The authors also documented from outcrop detail how magma at the base of the Moodies lava intruded downwards into fractured, apparently cemented Moodies sandstones (Fig.\u0026nbsp;13 in reference \u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e). This location lies only ca. 500 m NE of and stratigraphically ca. 30 m below the projected surface location of the investigated samples. Furthermore, there are two younger thermal and magnetic events in the BGB: a thermal alteration related to sulfidic and Au mineralization at ca. 3084 Ma in the northern part of BGB\u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e and a younger magmatic event at ca. 2967 Ma, comprising NW-SE oriented, intermediate, feldspar-porphyritic, dolerite dikes\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e (additional information is given in the Supplementary Material).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe borehole samples studied here are approximately 40 drilled meters (or ca. 25 stratigraphic meters) above the Moodies lava complex (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Core description shows that the contacts are intrusive; they are, in part, curved and free of indications of faulting or shearing (Supplementary Figs. S1 and S2). The thermal alteration event at ca. 3084 Ma is not associated with magmatism in the study area and the composition and structural orientation of the dolerite dikes of ca. 2967 Ma are different from the sampled intrusive rocks. All available geological evidence thus indicates that the contacts investigated here are likely part of magmatic-sedimentary interaction that took place during the Paleoarchean, prior to 3.2 Ga. Intrusion may have occurred at shallow depths and into unconsolidated sediment, as suggested by the nonlinear contacts, or occurred thousands to a few million years later, during late deformation of the BGB and subsequent beginning consolidation of the Kaapvaal craton.\u003c/p\u003e \u003cp\u003eTextures and phosphorus speciation in Moodies Group rocks\u003c/p\u003e \u003cp\u003eThe metasedimentary rocks from the Moodies Group investigated in this study show alternate banding with dark and light bands containing mostly biotite and mostly quartz, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA, D, G), indicating alternation between shale, siltstone and fine-grained sandstone. K-feldspar, calcite, chlorite, and plagioclase are common while zircon, arsenopyrite, and apatite are accessory phases (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eG). The metasedimentary samples do not show significant alteration (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eD) although minor sericitization is observed at some places. The mafic intrusive bodies are massive and contain pyroxene, plagioclase, ilmenite, and olivine. Ilmenite shows skeletal textures and is mostly associated with fine-grained feldspar, pyroxene, and glassy material (Fig. S3A, B), which is indicative of quenching\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. These quenched spots contain rare microcrystalline apatite (Fig. S3D). Olivine shows minor alteration along grain boundaries and fractures; however, the overall alteration in the rock is limited (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eF).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eOf the four contacts zones that we studied, two are dominated by shale at the metasedimentary-igneous interface while two are dominated by siltstone (Supplementary Fig. S4). The intrusive units at the contact zone show variable degree of sericitization, mostly along fractures (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eE), indicating some degree of fluid alteration. These samples show textural evidence of intrusion of a mafic melt into pre-existing sedimentary rock. First, fragments of laminated metasedimentary rock are incorporated into the intrusive units, indicating that the sedimentary rocks were already emplaced and at least somewhat lithified by the time the magma intruded (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB, E). Second, we observe formation of cryptocrystalline pyrite and pyrite aggregates and compositional change along the intrusive side of the contact z.one (Supplementary Fig. S5A). On the metasedimentary side, we observe aggregation of biotite (Fig. S5B). Third, apatite is present at the contact between the sedimentary unit and the intrusive bodies (Fig. S5D). Collectively, these features indicate a thermal effect on a P(V) source and associated contact-metamorphic reactions.\u003c/p\u003e \u003cp\u003eTotal Organic C concentrations are highest (833\u0026ndash;3310 ppm) in metasedimentary rocks and lowest (76\u0026ndash;93 ppm) in the intrusive bodies (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eE, Supplementary Table S2). Total P concentrations are higher (590\u0026ndash;610 ppm) in the intrusive bodies compared to the sedimentary rocks (310\u0026ndash;330 ppm), although apatite is absent or rare in the former and common in the latter (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA). Contact zone samples have intermediate concentration of P (370\u0026ndash;560 ppm), consistent with conservative mixing of the two units in bulk powders of the contact zones (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA). Phosphorus speciation data for Moodies Group samples are given in Supplementary Table S3. We note that P extraction yields with EDTA-NaOH solutions are low, 1.4\u0026ndash;2.4% for the metasedimentary unit, 5.2\u0026ndash;5.6% for the intrusive unit, and 3.8\u0026ndash;5.2% for the contact zone samples; however, these yields are consistent with previous studies\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Stronger solvents may increase the yield but risk losing P speciation via oxidation of reduced P or disintegration of polymerized P. The low and variable yields thus likely explain the high level of uncertainty in measured P(III) and PP(V) concentrations, but general trends between the two lithologies and the contact zones are nevertheless comparable.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWe estimated concentrations of three P species in the bulk Moodies samples using the ratios of them in the EDTA-NaOH extract, total P contents of the rocks, and extraction yields. The data of extracted and estimated concentrations are shown in Table S4. Extracted P(V) concentrations in the intrusive bodies, the metasedimentary unit, and the contact zones follow a similar pattern as total P concentrations (which were measured by bulk digestion of the rock, see Methods and Materials section), indicative of conservative mixing (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB). Averages of estimated phosphite concentrations in intrusive, contact zone, and metasediments are up to 2.84, 1.64, and 1.13 ppm, respectively, which follows conservative mixing predictions with similar percentages of total extracted P (0.25, 0.25, and 0.18%, in metasedimentary, intrusive, and the contact zone samples, respectively; Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC, H). For PP(V), the highest estimated (2.32-39.218 ppm) concentrations are observed in the contact zone, followed by the intrusive bodies (1.65\u0026ndash;1.65 ppm) and sedimentary rocks (0.47\u0026ndash;1.20 ppm) (Table S5). The highest relative proportion of PP(V) in the EDTA-NaOH extract is observed in the contact zone samples (averages for metasedimentary, intrusive, and the contact zone samples are 0.25, 0.28, and 2.14%, respectively), which cannot be explained by conservative mixing between intrusive rocks and metasediments (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eG). We did not notice any trends in the sedimentary rocks with increasing distance from the intrusions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eCarbon-phosphate mineral heating experiments\u003c/p\u003e \u003cp\u003eTo further explore the effects of heating on P-bearing sediments that also contain ferrous iron and carbon, we performed a series of experiments, which are listed in Supplementary Table S4 and results are summarized in Supplementary Table S5.\u003c/p\u003e \u003cp\u003eThree types of control experiments were conducted to verify the sources of polymerized and reduced P in starting materials. (1) Dry heating the silica powder alone did not produce polymerized or reduced P species but produced significant P(V) at 1150 \u003csup\u003eo\u003c/sup\u003eC suggesting that the silica powder contained some P(V) but was sufficiently clean in terms of polymerized and reduced P species. (2) Heating a mixture of silica and OM without a P-source produced significant PP(V) (1.81% of total extracted P). Similarly, a mixture of silica and CB produced significant amounts of P(I), P(III), PP(V), and PPP(V) (0.04, 0.48, 22.05, and 2.97% respectively). NMR analysis identified at least two organophosphate and one phosphonate compound in the OM but none in the CB. Therefore, a part of PP(V) in the heated OM and silica mixture may be produced due to polymerization of organophosphate compounds present in the OM, but collective data from these two control experiments point to the carbon-enhanced polymerization of the unidentified P(V)-phase present in the silica. The unheated mixture of silica and CB contained a similar amount of P(III) compared to the heated mixture, implying that the carbon sources contributed background levels of reduced P, but heating did not enhance P(III) production in these controls. (3) Heating phosphate precursors in the presence of silica, particularly magnesium phosphate, hydroxyapatite, and amorphous Fe-phosphate at 1150 \u003csup\u003eo\u003c/sup\u003eC produced PP(V) with a yield of 0.003, 0.026, and 2.065%, respectively (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Neither P(III), nor any other reduced P species were detected in any of these three control experiments. The vivianite and silica mixture produced P(III) and another unknown P species, which is also present in the unheated mixture, indicating that the heating did not facilitate the formation of these species. In summary, our control experiments indicate that heating alone can polymerize P(V) above background levels, but it does not noticeably enhance reduction.\u003c/p\u003e \u003cp\u003eCarbon in both forms impacted the polymerization of mineral-hosted P(V) with dependence on P(V) host (Supplementary Table S5 and Fig. S6, S7; Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). The addition of OM and CB to magnesium phosphate and silica mixtures enhanced the PP(V) yield from 0.003% (without C) to 0.047% (with OM) and 0.157% (with CB), respectively, at 1150 \u003csup\u003eo\u003c/sup\u003eC. Similarly, for hydroxyapatite, OM and CB enhanced the PP(V) yield from 0.026\u0026ndash;0.032% and 0.289%, respectively. These yields are low compared to that for CB\u0026thinsp;+\u0026thinsp;silica mixture alone, implying limited polymerization of P(V) hosted in these minerals. In contrast, adding OM and CB to vivianite and silica mixtures enhanced the polymerization yield from 0.000% to 1.08 and 30.98% and produced several polymerized molecules including PP(V), PPP(V), and PPPP(V). Adding the same C sources to amorphous Fe-phosphate and silica enhanced the polymerization yield from 2.065\u0026ndash;9.264% and 13.486%, respectively, and produced several polyphosphates and cyclophosphates including PP(V), PPP(V), PPPc(V), and PPPP(V). Better polymerization yield in Fe-phosphate phases points to the control of the mechanism of polyphosphate formation. Barringerite (Fe\u003csub\u003e2\u003c/sub\u003eP) but not any polyphosphates are detected in experiments containing Fe-phosphates, suggesting the formation of polyphosphates during dissolution in the EDTA solution, which is consistent with previous studies that reported polyphosphate formation during schreibersite ((Fe,Ni)\u003csub\u003e3\u003c/sub\u003eP) dissolution\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e,\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. This mechanism is distinct from polyphosphate formation during amorphous Fe-phosphate heating at low temperatures (175\u0026ndash;200 \u003csup\u003eo\u003c/sup\u003eC) where polyphosphate phases were likely formed\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e and during apatite-basalt heating where polyphosphates were formed during partial dissolution of P\u003csub\u003e4\u003c/sub\u003eO\u003csub\u003e10\u003c/sub\u003e\u003csup\u003e11\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eTemperature seems to be an important controlling factor for P polymerization. Previous studies suggested that simple heating of metastable Fe, Ca and Mg phosphates such as amorphous Fe-phosphate, brushite (CaHPO\u003csub\u003e4\u003c/sub\u003e\u0026middot;2H\u003csub\u003e2\u003c/sub\u003eO), whitlockite (Ca\u003csub\u003e18\u003c/sub\u003eMg\u003csub\u003e2\u003c/sub\u003eH\u003csub\u003e2\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e14\u003c/sub\u003e), struvite (MgNH\u003csub\u003e4\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e\u0026middot;6H\u003csub\u003e2\u003c/sub\u003eO), and newberyite (MgHPO\u003csub\u003e4\u003c/sub\u003e\u0026middot;3H\u003csub\u003e2\u003c/sub\u003eO) can produce polymerized P(V) at lower temperatures (\u0026lt;\u0026thinsp;300 \u003csup\u003eo\u003c/sup\u003eC)\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e\u003c/sup\u003e. For amorphous Fe-phosphate, polymerization was low (0.19%) at 350 \u003csup\u003eo\u003c/sup\u003eC\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e and moderate (2.1%) at 1150 \u003csup\u003eo\u003c/sup\u003eC (this study). On the other hand, heating apatite alone did not produce polyphosphates even at 1340 \u003csup\u003eo\u003c/sup\u003eC, which is consistent with low polymerization yield at 1150 \u003csup\u003eo\u003c/sup\u003eC in the apatite\u0026thinsp;+\u0026thinsp;silica control experiment. Hence, although P(V) polymerization may happen at a range of temperatures (70-1350 \u003csup\u003eo\u003c/sup\u003eC), a better yield is observed with amorphous Fe-phosphate or other metastable phosphate minerals compared stable minerals such as vivianite and apatite at low temperatures. At higher temperatures such as 1150 \u003csup\u003eo\u003c/sup\u003eC as used in our experiments, amorphous Fe-phosphate provides a better polymerization yield than apatite and vivianite. Amorphous Fe-phosphate may likely host HPO\u003csub\u003e4\u003c/sub\u003e instead of PO\u003csub\u003e4\u003c/sub\u003e tetrahedra as in apatite or vivianite, which favours the polymerization and can explain the better yield.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eCarbon and temperature controlled the reduction of P(V) hosted in all four minerals (Supplementary Table S5 and Fig. S7; Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). For magnesium phosphate, P(III) is the only reduced species that formed at 1150 \u003csup\u003eo\u003c/sup\u003eC upon addition of OM and CB while for hydroxyapatite, both P(I) and P(III) were formed. For magnesium phosphate, only CB produced P(III) with a yield of 0.003%, while for hydroxyapatite, both OM and CB produced P(III) and P(I) with a yield of 0.004 and 1.063%, respectively. At 1300 \u003csup\u003eo\u003c/sup\u003eC, the silica-hydroxyapatite-CB mixture produced P(I) and P(III) and gave a total reduction yield of 0.70%. Vivianite produced several reduced P species including P(I), P(III), PP(IV), and P-C(III) when OM and CB were added to the experiment at 1150 \u003csup\u003eo\u003c/sup\u003eC and the total reduction yield for these carbon sources were 2.9 and 29.28%, respectively. XRD suggest the presence of Fe\u003csub\u003e2\u003c/sub\u003eP in this CB-bearing experiment (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). At 1300 \u003csup\u003eo\u003c/sup\u003eC, the silica-vivianite-CB mixture produced similar reduced P species, including P(I), P(III), P-C(III), and PP(IV) with a total reduction yield of 17.4%. Amorphous Fe-phosphate also produced several reduced P species, including P(I), P(III), P-C(III), and PP(IV) in the presence of OM and CB at 1150 \u003csup\u003eo\u003c/sup\u003eC with the reduction yields of 8.1 and 10.2%, respectively. XRD data suggest the presence of Fe\u003csub\u003e2\u003c/sub\u003eP in both of these amorphous Fe-phosphate experiments (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Previous studies suggested that Fe\u003csup\u003e2+\u003c/sup\u003e can reduce P(V) at moderate temperatures (200\u0026ndash;350 \u003csup\u003eo\u003c/sup\u003eC); however, the reduction yield varied significantly in two separate studies (either \u0026lt;\u0026thinsp;0.001%\u003csup\u003e9\u003c/sup\u003e or 4%\u003csup\u003e8\u003c/sup\u003e). Increasing temperature did enhance the reduction in one study; however, the yield was still low (0.075% at 350 \u003csup\u003eo\u003c/sup\u003eC)\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. Even at higher temperatures explored here (e.g., 1150 \u003csup\u003eo\u003c/sup\u003eC), Fe\u003csup\u003e2+\u003c/sup\u003e is an ineffective P(V) reducing agent. We, therefore, suggest that C in both forms is more efficient compared to Fe\u003csup\u003e2+\u003c/sup\u003e to reduce P(V) in Fe-phosphate minerals, particularly at high temperatures.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAddition of an Fe source enhanced the reduction and polymerization yield of hydroxyapatite-hosted P(V) (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, Supplementary Table S5 and Fig. S7). At 1300 \u003csup\u003eo\u003c/sup\u003eC, the silica-hydroxyapatite-CB experiment produced P(I) and P(III) with a reduction yield of 0.70%. When FeS, Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e, or Fe were added to the experiment, the reduction yield increased 81.5, 96.2, and 22.7%, respectively. The FeS-bearing experiment produced P(III) and several unidentified P species. XRD data indicate the presence of schreibersite (Fe\u003csub\u003e3\u003c/sub\u003eP) in this experiment (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e- and Fe-bearing experiments produced P(I), P(III), and P-C(III) and the latter one also produced PP(IV) as well as several polymerized P species including PP(V), PPP(V), and PPPP(V). XRD data suggest the presence of Fe\u003csub\u003e3\u003c/sub\u003eP and Fe\u003csub\u003e2\u003c/sub\u003eP in both of these two experiments (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). FeS\u003csub\u003e2\u003c/sub\u003e addition produced a reduction yield of 0.076%; however, absolute concentrations of P(I) and P(III) were high compared to the silica-hydroxyapatite-CB experiment, and this experiment produced Fe\u003csub\u003e3\u003c/sub\u003eP, which was not the case for silica-hydroxyapatite-CB. Our data thus suggest that the Fe oxidation state (Fe\u003csup\u003e0\u003c/sup\u003e for metallic Fe, Fe\u003csup\u003e2+\u003c/sup\u003e for FeS and FeS\u003csub\u003e2\u003c/sub\u003e, and a mixture of Fe\u003csup\u003e2+\u003c/sup\u003e and Fe\u003csup\u003e3+\u003c/sup\u003e in Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e) and mineralogy (oxide or sulphide) did not impact phosphide formation from apatite. We suggest that apatite can be reduced extensively in the presence of any form of Fe-oxide or -sulfide by a C source (organic matter, organic or pure carbon) in the temperature range of 1100\u0026ndash;1300 \u003csup\u003eo\u003c/sup\u003eC or higher.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eGeological evidence of magmatic P reduction and polymerization in the Archean\u003c/p\u003e \u003cp\u003eThere are three possible explanations for P(III) and PP(V) observed in Moodies Group intrusive and metasedimentary units. First, since the relative proportion of P(III) is similar in both rock units, it is possible that P(III) abundances were reset as a consequence of regional metamorphism consistent with previous experiments \u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e and with reports of P(III) from high-grade Eoarchean metasediments\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. P(V) reduction in such cases required water-poor conditions and higher temperatures, which is likely the case for the amphibolite grade banded iron formation rocks where P(III) is previously reported\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e. In the Moodies Group, temperatures achieved during greenschist-facies metamorphism (350\u0026thinsp;\u0026plusmn;\u0026thinsp;50 \u003csup\u003eo\u003c/sup\u003eC; reaching up to 420\u0026ndash;460 \u003csup\u003eo\u003c/sup\u003eC\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e) are much lower compared to that. Furthermore, it is unknown if Fe\u003csup\u003e2+\u003c/sup\u003e-induced reduction of phosphate can happen inside a silicate mineral containing Fe\u003csup\u003e2+\u003c/sup\u003e, which is the case of the intrusive samples. In case of PP(V), the magmatic units contain a much higher concentration compared to the sedimentary units, which cannot be explained by regional metamorphism. We therefore discard the possibility of metamorphic origin of P(III) and PP(V) in Moodies intrusive and sedimentary units.\u003c/p\u003e \u003cp\u003eSecond possibility is that biological processes indirectly or directly contributed to P(III) and PP(V) observed in the sedimentary units. This would be consistent with the presence of widespread microbial mats in Moodies Group\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e,\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. A direct biological conversion of P(V) compounds to P(III) or PP(V) is not known in the Archean\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. Although P(III) may form indirectly due to disintegration of phosphonates produced by microbial life\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e,\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e, microbial life did not have the ability to generate phosphonate before the Great Oxygenation Event\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. We therefore discard the possibility of a direct or indirect biologic origin for the P(III) and PP(V) in the sediments.\u003c/p\u003e \u003cp\u003eThird possibility, which is most likely, is that P(III) and PP(V) in the intrusive bodies are of magmatic origin and that in the sedimentary units are recycled from the intrusive bodies. Previous reports of PP(V) occurrence in modern magmatic fumarole\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e, in Phanerozoic olivine samples from Hawaii and Pakistan\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e, and in experimentally produced alkali glass \u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e supports the magmatic origin of PP(V). PP(V) in the Moodies intrusive bodies may be hosted in glass or in olivine. Previous studies suggested that weathering of basaltic rock in anoxic conditions favours the release of P(V) into ocean water\u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e. Given that P(III) and possibly PP(V) are more soluble than P(V) \u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, similar weathering as well as hydrothermal alteration may release P(III) and PP(V) into water from the mafic igneous rocks such as those in Moodies. These species may subsequently get incorporated into sedimentary rocks. To the best of our knowledge, this is the first evidence of magmatic P(III) and PP(V) and their recycling in the Archean.\u003c/p\u003e \u003cp\u003eReduction and polymerization of P during thermal metamorphism and in natural conditions\u003c/p\u003e \u003cp\u003eThe contact zone samples from the Moodies Group suggest thermal induced formation of polyphosphates, but not of P(V) reduction. Experimental data suggest that P(V) polymerization is comparatively easier than reduction, as it may happen even in low temperatures (\u0026lt;\u0026thinsp;200 \u003csup\u003eo\u003c/sup\u003eC vs. \u0026gt;1150 \u003csup\u003eo\u003c/sup\u003eC; See Supplementary Material) and may be enhanced in the presence of carbon. In the Moodies Group, pyrite formation and biotite accumulation along the contact zones, and reworking of lithified sediment fragments into the magma, indicate that magma emplacement postdated sedimentation and thus likely heated the sediments at the contact zone. Previous studies noted diverse and widespread interactions of the mafic lava with sedimentary units at inferred temperatures of 700\u0026ndash;1000 \u003csup\u003eo\u003c/sup\u003eC, in the Moodies Group\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e,\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u003c/sup\u003e. Apatite present at the contact zones and organophosphorus compounds, the presence of which can be speculated by the presence of organic carbon and previous reports of microbial mats in sedimentary units in the Moodies Group\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e, are the most plausible P(V) source during the heating. Although we notice pyrite at the contact zones, a close association of apatite and pyrite is rare, if not absent. Based on these observations, we suggest that our OM\u0026thinsp;+\u0026thinsp;silica, OM\u0026thinsp;+\u0026thinsp;hydroxyapatite, and OM\u0026thinsp;+\u0026thinsp;silica\u0026thinsp;+\u0026thinsp;hydroxyapatite experiments (1150 \u003csup\u003eo\u003c/sup\u003eC) are the most relevant for the thermal metamorphism in the Moodies Group. These experiments produced PP(V) ranging from 0.026 to 1.81% and P(III)\u0026thinsp;\u0026lt;\u0026thinsp;0.004%, which is consistent with the observed PP(V) (average 2.14%) and P(III) in the contact zone samples. Depending on the initial P(V) host, either simple heating or heating in the presence of organic carbon could have produced the observed PP(V) at the contact zones but the conditions were unfavourable to generate additional P(III) than existing levels.\u003c/p\u003e \u003cp\u003eOur experimental data can explain other natural occurrences of P(V) reduction. Metallic phosphides including Fe\u003csub\u003e2\u003c/sub\u003eP and Fe\u003csub\u003e3\u003c/sub\u003eP have been reported from pyrometamorphosed rocks in the Hatrurim Formation (Levant region) and from volcanic rocks on Disko Island\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e. In those cases, organic matter or hydrocarbon was present in association with apatite as well as Fe-minerals. The country rock was heated by magmatism at temperatures above 1050 \u003csup\u003eo\u003c/sup\u003eC in the Levant region\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e and at ca. 1200-1300\u003csup\u003eo\u003c/sup\u003eC on the Disko Island\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e. Hence, the hydroxyapatite\u0026thinsp;+\u0026thinsp;silica\u0026thinsp;+\u0026thinsp;CB\u0026thinsp;+\u0026thinsp;Fe-source experiments at 1300 \u003csup\u003eo\u003c/sup\u003eC broadly covers the conditions in these two places and produced similar phosphide minerals, explaining P(V) reduction in these two regions. These experiments can also explain apatite-hosted P(V) reduction in the presence of organic matter or tree-roots during lighting where temperatures reaches\u0026thinsp;\u0026gt;\u0026thinsp;1725 \u003csup\u003eo\u003c/sup\u003eC\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e,\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eImplications for the origin and evolution of early life\u003c/p\u003e \u003cp\u003eOur findings carry three major implications for the origin and early evolution of life on Earth. First, experimental and Moodies Group data together suggest that high-temperature alteration of sediments containing organic carbon could have been an important mechanism of polyphosphate generation in the Archean and likely on the prebiotic Earth. Previous studies have shown that in the presence of organic compounds and urea-based eutectic solution with low water activity, apatite and other phosphate salt can produce polymerized species at relatively mild conditions\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e,\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e; however, geological evidence of such organic compounds is yet to be discovered. In absence of these organics, high-temperature thermal induced processes shown in this study, could have been crucial for making polymerized P species.\u003c/p\u003e \u003cp\u003eSecond, the Moodies Group data suggest that magmatic rocks could have been an important, long-term, and stable source of P(III) and PP(V) along with P(V) on the prebiotic Earth and in the Archean. Although the total amounts of P(III) and PP(V) in the studied basaltic rock are in the low ppm range (2.84 and 1.65 ppm), they are more water-soluble than P(V)\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e, implying that anoxic weathering and hydrothermal alteration of these rocks could have liberated them more efficiently than P(V) to the ocean. Previous studies argued in favour a significant amount of P(III) along with P(V) in the Archean ocean, which has been attributed to dissolution of phosphide delivered by meteorite and produced by lightning strike\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. We suggest that part of the Archean seawater P(III) could have been delivered by ocean-floor weathering and hydrothermal vents. The half-life of P(III) under Archean conditions has been estimated to 0.6 Ma while that of PP(V) may have much lower\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e\u003c/sup\u003e; both of them eventually would convert into P(V). Therefore, these species could have contributed to bioavailable P(V) in the Archean ocean.\u003c/p\u003e \u003cp\u003eThird, although the Moodies Group represents a volcano-sedimentary succession in shallow-marine and coastal depositional settings, our experimental results are applicable to prebiotic volcanic lakes and hot-spring environments, where thermal metamorphism or magma-sediment interaction could have taken place. In these settings, organic C species may have been generated abiotically by volcanism or lightning strikes and/or delivered by meteorites\u003csup\u003e\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e,\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e\u003c/sup\u003e and accumulated in the lakes and pools along with phosphate minerals and metal oxides and sulphides\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e. Here, volcanism was common due to a significantly higher heat flux than today, driven by the combined effects of a hotter mantle and residual heat from planetary accretion\u003csup\u003e\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e,\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e, and basalt and komatiite were likely the most abundant rocks\u003csup\u003e\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e. Because eruption temperatures of the latter exceeded in places 1600 \u003csup\u003eo\u003c/sup\u003eC\u003csup\u003e\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u003c/sup\u003e, sediments in contact with komatiitic magmas would have readily achieved temperatures approaching those in our experiments (1150 and 1300 \u003csup\u003eo\u003c/sup\u003eC) or higher. Similarly, the ingredients used in the experiments, i.e., P(V) source, C, Fe-oxide/-sulphide, and heat, are also relevant to impact events and lightning strikes, which were likely common on prebiotic Earth\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e,\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e and known to create temperatures as high as \u0026gt;\u0026thinsp;1700 \u003csup\u003eo\u003c/sup\u003eC\u003csup\u003e\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e. We therefore suggest that there might be several local niches on the prebiotic Earth where P(V) hosted in so-called \u0026lsquo;un-reactive\u0026rsquo; minerals such as apatite and vivianite, could potentially have been transformed into phosphides, as seen in our experiments. The presence of phosphides in thermal metamorphic rocks in the Levant region and on Disko Island\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u003c/sup\u003e and in lightning-stroke soil\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e,\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e further suggests the natural relevance of this reduction mechanism. Once produced such phosphide may dissolve in water and produce the reduced and polymerized P species as seen in our experimental products including P(I), P(III), P-C(IIII), PP(IV), PP(V), PPP(V), and PPPc(V), which are more reactive compared to P(V). Because of high solubility and better reactivity, these species are better phosphorylating agent or organic molecules\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e and thus crucial for the origin of life. Furthermore, phosphides may directly phosphorylate nucleosides and other organic compounds as well\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e,\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e. This reduction mechanism plausibly operated at local scale on the prebiotic Earth, particularly when the criteria for P(V) reduction was fulfilled but such local supply of reactive P species may have been sufficient to trigger phosphorylation reactions required for the origin of life.\u003c/p\u003e \u003cp\u003eIn summary, we provide geological evidence of magmatic and thermal-metamorphic polyphosphate production and magmatic phosphite during the Archean and suggest that weathering and hydrothermal alteration of magmatic rocks can be a stable source of reactive and bioavailable P to Archean seawater. Our data suggest that P(V)-polymerization at high temperatures can be facilitated by the presence of organic carbon. Organic carbon might be an important reducing agent at temperatures\u0026thinsp;\u0026gt;\u0026thinsp;1150 \u003csup\u003eo\u003c/sup\u003eC for P(V) hosted in so called \u0026lsquo;unreactive\u0026rsquo; minerals such as vivianite and apatite producing phosphides, that upon dissolution can provide several soluble and reactive P species, including P(I), P(III), P-C(IIII), PP(IV), PP(V), PPP(V), and PPPc(V) crucial for prebiotic phosphorylation reactions. In conclusion, both magmatic and carbon-bearing thermally metamorphosed rock might have played important roles in supplying reactive and soluble P species during the origin and early evolution of biosphere.\u003c/p\u003e "},{"header":"Methods and Materials","content":"\u003cp\u003eWhole rock analysis and TOC measurements\u003c/p\u003e \u003cp\u003ePowders (0.60 g each) of all samples were sent to Australian Laboratory Services (ALS) in Dublin, Ireland, for whole-rock geochemical characterisation using their method ME-MS-61r of four-acid digestion (HCl, HNO\u003csub\u003e3\u003c/sub\u003e, HF, HClO\u003csub\u003e4\u003c/sub\u003e) followed by ICP-MS and ICP-AES analyses. Reproducibility was assessed with rock standards OREAS-45d, OREAS-905, and MRGeo-08, and with sample replicates. For P, Fe, Cr, and Ti, the reproducibility was 5% or better. Total organic carbon (TOC) was measured at the University of St Andrews on decarbonated rock powders. Circa 0.5 g of powder were treated with 2M HCl overnight at room temperature, followed by triple-rinsing with 18.2 MΩ\u0026middot;cm ultrapure water and drying in a sealed oven for three days. The dried powders were then analyzed by flash-combustion with an elemental analyzer (EA-Isolink) coupled to an IRMS (MAT253, both Thermo Fisher Scientific). Peak areas were calibrated for carbon abundances. Reproducibility is better than 5%.\u003c/p\u003e \u003cp\u003eBacteria biomass and culture conditions\u003c/p\u003e \u003cp\u003eBacteria biomass (OM) used as a C source in the dry-heating experiments was generated from phosphate replete cultures of both nitrogen fixing (diazotrophic) and non-nitrogen fixing strains of cyanobacteria. The cyanobacterial diazotrophs included the freshwater \u003cem\u003eCalothrix\u003c/em\u003e PCC7507 (Pasteur Culture Collection) and \u003cem\u003eNostoc\u003c/em\u003e sp., which were cultured in nitrogen-free BG11\u003csub\u003e0\u003c/sub\u003e medium \u003csup\u003e\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e\u003c/sup\u003e and the brackish dwelling strains \u003cem\u003eNodularia spumigena\u003c/em\u003e CCY 9414 (obtained from Lukas Stal, Culture Collection Yerseke, The Netherlands), and \u003cem\u003eNodularia harveyana\u003c/em\u003e SAG 44.85 (Culture Collection of Algae, G\u0026ouml;ttingen University), grown in Baltic Sea medium (Ba\u003csub\u003e0\u003c/sub\u003e) lacking a combined nitrogen source \u003csup\u003e\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e\u003c/sup\u003e. Freshwater species \u003cem\u003eMicrocystis aeruginosa\u003c/em\u003e PCC7806 and PCC9432 were grown in nitrate containing BG11 medium \u003csup\u003e\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAn inoculum of exponentially growing culture material was used to inoculate 100 ml of the appropriate medium in T\u003csub\u003e175\u003c/sub\u003e ventilated cell culture flasks (Sarstedt, Germany) at a concentration of chlorophyll a of ~\u0026thinsp;0.1 \u0026micro;g.ml\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e and incubated at 24\u0026deg;C, 60 \u0026micro;mol photons m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e on a 14:10 hour day-night cycle, under present day atmospheric conditions (Plant growth chamber E-22L, Percival, USA). Biomass was harvested after 4\u0026ndash;6 weeks once the cultures had reached stationary phase \u003csup\u003e\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e,\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e\u003c/sup\u003e. Cultures were pelleted in sterile 50 ml polypropylene tubes (Sarstedt, Germany) by centrifugation at 7 500 rcf for 30 min., washed twice with sterile MQ water and frozen at -80\u0026deg;C. The pellets were lyophilized (at -10\u0026deg;C, 0.04 mbar; CHRIST LSC plus) and the dried biomass powdered using an agate mortar and pestle. The final mixture of biomass (referred to as OM in the main text) includes 0.26 g \u003cem\u003eCalothrix\u003c/em\u003e PCC7507, 0.17 g \u003cem\u003eN. harveyana\u003c/em\u003e, 0.19 g \u003cem\u003eNostoc\u003c/em\u003e, 0.18 g \u003cem\u003eN. spumigena\u003c/em\u003e, 0.70 g \u003cem\u003eM. aeruginosa\u003c/em\u003e PCC7806, and 0.67 g \u003cem\u003eM. aeruginosa\u003c/em\u003e PCC9432. While these particular diazotrophs are not representative of deep branching cyanobacteria, their OM was not found to significantly vary with respect to C and N contents, nor stable isotope signatures, when grown under anoxic conditions simulating those on early Earth, present-day atmospheric conditions, nor under elevated atmospheric CO\u003csub\u003e2\u003c/sub\u003e conditions \u003csup\u003e\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e\u003c/sup\u003e. The OM thus used in these experiments can be considered as an Archean equivalent of organic-carbon-containing matter.\u003c/p\u003e \u003cp\u003eHeating experiments\u003c/p\u003e \u003cp\u003eAll experiments and associated analyses were carried out at the University of St Andrews. Acid-washed (1M or 2M HCl) and baked (500\u0026deg;C) glass containers and acid- and hot-water (18.2 MΩ\u0026middot;cm, ultrapure) washed plastic centrifuge tubes, bottles, pipette tips, and syringes were used in all the stages of the experiments and subsequent sampling. Synthetic hydroxyapatite (Ca\u003csub\u003e5\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e3\u003c/sub\u003e(OH); Thermo Scientific; Cat. No. 036731.36, Lot. X15F024) and magnesium phosphate (Mg\u003csub\u003e3\u003c/sub\u003e(PO\u003csub\u003e4\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e\u0026middot;xH\u003csub\u003e2\u003c/sub\u003eO; Sigma-Aldrich; PCode 1002982444), natural vivianite (Brazil), and in-house amorphous Fe-phosphate were used as a P(V) precursor. To prepare amorphous Fe-phosphate, FeCl\u003csub\u003e2\u003c/sub\u003e\u0026middot;4H\u003csub\u003e2\u003c/sub\u003eO (Sigma Aldrich, PCode 101074277) and (NH\u003csub\u003e4\u003c/sub\u003e)H\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e, (Thermo Scientific; Cat No. 193701000, Lot A0443028) were added in a molar ratio of 3:1 in 300 ml deoxygenated, deionized water (18.2 MΩ\u0026middot;cm) with a pH of 4 (this method is adopted from Herschy et al.\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e and Baidya et al.\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e). The glass bottle was connected to a vacuum pump and N\u003csub\u003e2\u003c/sub\u003e cylinder for maintaining an anoxic condition and a hot plate for increasing temperature. The solution was stirred in the dark (shielded with Al foil), evaporated into dryness maintaining anoxic conditions at 60 \u003csup\u003eo\u003c/sup\u003eC, and the solid residue was brought back to room temperature. The residue was crushed with pestle \u0026amp; mortar, stored in a sealed vial, and used as a P(V) precursor for subsequent heating experiments. OM as described above and carbon black from Cabot were used as a C source. Metallic Fe (Thermo Scientific, Cat. No. 000737.30, Lot. R20F039), Fe\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e (Inoxia Limited (UK); EC 215-169-8), FeS (Thermo Scientific; Cat No. 014024.09, Lot. T07H028) and FeS\u003csub\u003e2\u003c/sub\u003e (natural; Thermo Scientific; Cat. No. 042633.06, Lot. T23G054) were used as an Fe-source in selected apatite-bearing experiments. Additionally, SiO\u003csub\u003e2\u003c/sub\u003e powder (crushed Sea sands, VWR, CAS 14808-60-7) was used to prepare the initial mixture.\u003c/p\u003e \u003cp\u003eFor each experiment, 0.6 g of powdered mixture was prepared by mixing 0.18 g of one of the phosphate sources, 0.18 g of one of the C sources, variable proportions of powdered SiO\u003csub\u003e2\u003c/sub\u003e, and in some cases, a Fe source using a pestle \u0026amp; mortar (Supplementary Table\u0026nbsp;1). The weight ratio for C and P(V) was 1:1 except for the control experiments. Variable weights of Fe precursors were used to maintain the total Fe added in each experiment the same. As an example, in Exp 8, 0.18 g of hydroxyapatite, 0.18 g of OM, and 0.24 g of silica powder were mixed. For control experiments containing only SiO\u003csub\u003e2\u003c/sub\u003e powder, 0.6 g od SiO\u003csub\u003e2\u003c/sub\u003e powder was used while those containing SiO\u003csub\u003e2\u003c/sub\u003e powder and a P(V) source or silica powder and a C source, 0.18 g of C or P(V) source was mixed with 0.42 g of SiO\u003csub\u003e2\u003c/sub\u003e. 0.52\u0026ndash;0.56 g of the powder mixtures were pelted, each pellet containing 0.13\u0026ndash;0.14 g of powder mixture.\u003c/p\u003e \u003cp\u003eThe pellets were then loaded into an alumina boat and kept inside a tube furnace under flowing N\u003csub\u003e2\u003c/sub\u003e gas (30 ml/minute) at room temperature for 3 hours. This step was done to make sure the gas inside the tube is inert before the heating stage started. The furnace was equipped with a K-type thermocouple and a temperature controller. A forward ramp of 7\u0026ndash;8\u0026deg;C/min was used to reach the desired temperatures i.e., 1150\u003csup\u003eo\u003c/sup\u003eC or 1300\u003csup\u003eo\u003c/sup\u003eC, which was maintained for 48 hours, followed by a downward ramp of 5\u0026deg;C/min (Supplementary Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003eB). The heated residues were brought back to room temperature while maintaining the same N\u003csub\u003e2\u003c/sub\u003e flow rate. They were then powdered and stored in sealed vials before subsequent analysis.\u003c/p\u003e \u003cp\u003eSolid characterization using powder X-ray diffraction (PXRD)\u003c/p\u003e \u003cp\u003eAn aliquot of the powdered experimental products was loaded into 0.5- or 0.7-mm capillary tubes and sealed for XRD analysis. The PXRD patterns were recorded on a STOE STADIP diffractometer using Mo Kα1 radiation at room temperature from 2.5\u003csup\u003eo\u003c/sup\u003e to 40\u0026deg; (2θ) with a scan rate of 2.75\u003csup\u003eo\u003c/sup\u003e (2θ)/step in capillary Debye-Scherrer mode. The PXRD data were compared to solids in the Inorganic Crystal Structure Database (ICSD) and Crystallography Open Database (COD) for phase identification using the Crystal Diffract software (version 7.0.4.300).\u003c/p\u003e \u003cp\u003eNMR and IC-ICPMS analysis for P speciation\u003c/p\u003e \u003cp\u003eThe P speciation analysis for the rock samples were done using an ion chromatography-inductively coupled plasma mass spectrometer (IC-ICPMS) set-up at the University of St Andrews \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. For the experimental samples, both nuclear magnetic resonance (NMR) spectroscopy and IC-ICPMS were used. It is important to note that NMR has higher detection limits (150\u0026ndash;200 ppb) for P species in the used analytical conditions while the IC-ICPMS set-up can detect as little as 0.1 ppb of P species in solution. Furthermore, NMR can detect several P species while only inorganic P(I), P(III), P(V), and PP(V) can be detected in the IC-ICPMS set-up.\u003c/p\u003e \u003cp\u003eFor each rock sample, 0.20 g powder was treated with an Ethylenediaminetetraacetic acid-sodium hydroxide (0.05M EDTA and 0.25M NaOH) solution \u003csup\u003e\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e\u003c/sup\u003e maintaining a solid:solution ratio of 1:10, 1:5, or 1:3.75. As the total concentration of P species, particularly P(III) and PP(V), in the rock samples were low, three different solid:solution ratios were chosen. For preparing the EDTA-NaOH solution, Na\u003csub\u003e2\u003c/sub\u003eEDTA (Sigma Aldrich) salt and 10M NaOH solution (Thermo Scientific) were dissolved in deionized water. The solid and solution mixture were prepared in 15 ml Falcon tubes (acid- and hot-water washed) and left on a shaker (175 rpm/minute) for 14\u0026ndash;15 hours. The solid-solution mixtures were then centrifuged at 3000 rpm for 15 minutes. For the metasedimentary and contact zone samples, a floating grey phase was observed in the supernatant, which most likely is organic carbon. For these samples, the supernatant was filtered by 0.20 \u0026micro;m PTFE syringe filter (Fisherbrand). A transparent solution at this stage suggests the precipitation of all the extracted Fe and other transition metals. Precipitation of these metals is essential for the P speciation measurements using the subsequent IC-ICPMS analysis \u003csup\u003e\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e because excess dissolved metal may precipitate as oxides in the anion separation column of the IC and bind phosphate by adsorption within the column, thereby impacting analytical quality. The supernatant was then diluted 25 or 50 times and P species analysis was done using the IC-ICPMS set-up.\u003c/p\u003e \u003cp\u003eFor each experimental sample, 0.1 g of powder was treated with 1ml of EDTA-NaOH solution for 8 hours. A 4 ml, flat-bottom glass vial with a magnetic stirrer was used for this step. After this, the supernatant was filtered with 0.20 \u0026micro;M PTFE syringe filter (Fisherbrand). The solution was then diluted 25, 50, or 75 times and analyzed with IC-ICP-MS. An aliquot of the solution was analysed with an NMR.\u003c/p\u003e \u003cp\u003eThe IC-ICPMS set-up consisted of a Dionex ICS-6000 ion chromatograph (IC) and an Element 2 inductively coupled plasma mass spectrometer (ICP-MS) (both from Thermo Scientific). The IC was equipped with a Dionex AS-AP autosampler, a 25 mm Dionex IonPac AS17-C separation column (2 mm bore), a 25mm Dionex IonPac AG17-G guard column (2 mm bore), and a Dionex ADRS-600 (2 mm) suppressor. The flow rate in the IC was held constant at 0.5 ml/min. The concentration of the KOH eluent solution was ramped up from 1 mM to 40 mM over 20 minutes, which was then maintained for another 24 minutes followed by a ramp-down to 1 mM in 6 minutes. The detector outlet of the IC was physically connected to a 1 ml/min nebulizer attached to the spray chamber (Scott model; quartz glass) of the ICP-MS. The ICP-MS was operated at a sample gas flow rate of 1.03\u0026ndash;1.10 ml/min, cool gas flowrate of 16 ml/min, and RF power of 1183 in medium-resolution mode. Data were collected in the ICP-MS as chromatographs of 3 minutes duration. Each chromatogram consisted of the pre-peak background, the peak, and the post-peak background for each P-species.\u003c/p\u003e \u003cp\u003eThe chromatographic data were produced for samples and standards. Standards contained 0.2 to 100 ppb of four P species (prepared from NaH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e2\u003c/sub\u003e.H\u003csub\u003e2\u003c/sub\u003eO (Thermo Fisher), Na\u003csub\u003e2\u003c/sub\u003eHPO\u003csub\u003e3\u003c/sub\u003e\u0026middot;5H\u003csub\u003e2\u003c/sub\u003eO (Thermo Fisher), NaH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e (Thermo Fisher), and Na\u003csub\u003e4\u003c/sub\u003eP\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e7\u003c/sub\u003e (Sigma Aldrich)) in a solution matrix similar to the samples. The acquired chromatogram data were smoothened with the OriginLab software, using the FFT filter with a points-of-window value of 5, and the peak area under the curve was used for quantification. The detection limits of the IC-ICPMS set-up were \u0026lt;\u0026thinsp;0.1 ppb for P(III) and P(V), 0.1 ppb for P(I), and 0.2 ppb for PP(V). Analysis was done twice or thrice, and the geometric mean was calculated due to large variations in the replicates.\u003c/p\u003e \u003cp\u003eFor NMR analyses, an aliquot (540 \u0026micro;L) of EDTA-NaOH extracts of the experimental samples was mixed with 60 \u0026micro;L of D\u003csub\u003e2\u003c/sub\u003eO and loaded in an NMR tube to be measured on a Bruker AVIII 500 MHz NMR. This NMR set-up is equipped with a nitrogen-cooled broadband cryoprobe, which improves sensitivity. Samples were analyzed in proton-decoupled mode with 15000 scans. The \u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003eP chemical shifts were referenced to phosphoric acid, which has a chemical shift of 0δ. Standards containing six different P species, P-C(III), P(I), P(III), P(V), PP(V), PPP(V), PPPc(V) of known concentrations (0.2 ppm to 800 ppm phosphorus), prepared using NaH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e2\u003c/sub\u003e.H\u003csub\u003e2\u003c/sub\u003eO (Thermo Scientific), Na\u003csub\u003e2\u003c/sub\u003eHPO\u003csub\u003e3\u003c/sub\u003e\u0026middot;5H\u003csub\u003e2\u003c/sub\u003eO (Thermo Scientific), NaH\u003csub\u003e2\u003c/sub\u003ePO\u003csub\u003e4\u003c/sub\u003e (Thermo Scientific), and Na\u003csub\u003e4\u003c/sub\u003eP\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e7\u003c/sub\u003e (Sigma Aldrich), Na\u003csub\u003e5\u003c/sub\u003eP\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e10\u003c/sub\u003e,(Thermo Scientific), and Na\u003csub\u003e5\u003c/sub\u003eP\u003csub\u003e3\u003c/sub\u003eO\u003csub\u003e9\u003c/sub\u003e (Thermo Scientific) were analysed to build calibration curves for each P species. The experimental samples contained PPPP(V) or even longer-chain polyphosphates as well as several unknown P species. For PPPP(V), the calibration curve of PPP(V) was used; for the unknown P species, the calibration of P(V).\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eAcknowledgements\u003c/p\u003e\n\u003cp\u003eThis work was financially supported by a Natural Environment Research Council (NERC- UKRI) Frontiers grant to EES (NE/V010824/1), a Marie Skłodowska-Curie Actions grant to ASB (EP/Y026497/1), and a German Research Foundation (DFG) grant (GE2558/4-1) to MMG. We acknowledge Sami Mikhail for his help during pellet making and Tomas Lebl and Siobhan Smith for their help during the NMR analysis. Rajan Biswas and Oxana Magdysyuk helped during XRD analyses and data interpretation. For XRD analyses, we also acknowledge the Engineering and Physical Science Research Council (EPSRC) Core Equipment Grant (EP/V034138/1). ICDP staff provided access to core and administration of the sample database. Sebastian Reimann drafted the geologic map. South Africa’s Council for Geoscience supplied the hyperspectral core maps shown in Fig. S1. The complete data for this study are available through the National Geoscience Data Centre of the British Geological Survey. In order to meet institutional and research funder open-access requirements, any accepted manuscript arising shall be open access under a Creative Commons Attribution (CC BY) reuse licence with zero embargo.\u003c/p\u003e\n\u003cp\u003eAuthor contributions\u003c/p\u003e\n\u003cp\u003eThe idea is conceived by EES and ASB. MMG and CH supplied bacteria extracts and rock samples, respectively. ASB analyzed the samples and did the experimental investigations with the help of EES and CS. ASB prepared the first draft of the manuscript with contribution from MMG and CS. The manuscript were reviewed and edited by EES, ASB, CH and MMG.\u003c/p\u003e\n\u003cp\u003eCompeting interests\u003c/p\u003e\n\u003cp\u003eAuthors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003eData and materials availability\u003c/p\u003e\n\u003cp\u003eAll data are available in the main text or in the supplementary materials.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eSchwartz, A. W. Phosphorus in prebiotic chemistry. \u003cem\u003ePhilos. Trans. R. Soc. B Biol. Sci.\u003c/em\u003e \u003cstrong\u003e361\u003c/strong\u003e, 1743\u0026ndash;1749 (2006).\u003c/li\u003e\n\u003cli\u003eNicholls, J. W. F. \u003cem\u003eet al.\u003c/em\u003e On the potential roles of phosphorus in the early evolution of energy metabolism. \u003cem\u003eFront. Microbiol.\u003c/em\u003e \u003cstrong\u003e14\u003c/strong\u003e, (2023).\u003c/li\u003e\n\u003cli\u003eGulick, A. Phosphorus as a factor in the origin of life. \u003cem\u003eAm. 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Acta\u003c/em\u003e \u003cstrong\u003e336\u003c/strong\u003e, 332\u0026ndash;340 (2022).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-6529805/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6529805/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eReduced and polymerized phosphorus (P) species may have been crucial for the origin and early evolution of life, as they are more reactive and soluble than phosphate (P(V)). Thermal processes could have produced these P species; however, the underlying mechanism is poorly constrained, and geological evidence of polymerized P in the Precambrian is so far absent. Here, we investigated contact-metamorphic rocks from the ca. 3.22 Ga Moodies Group (South Africa), where mafic dikes intruded into shallow-marine sediments. We provide evidence of magmatic phosphite (up to 2.85 ppm) and metamorphic polyphosphate (up to 39.3 ppm) in the Archean. Our laboratory experiments suggest that carbon can facilitate the thermal production of polyphosphates and reduced P species including phosphide from less reactive minerals including apatite and vivianite. We conclude that magmatic and thermal-metamorphic rocks could have provided soluble and reactive P species crucial for the origin and early evolution of life.\u003c/p\u003e","manuscriptTitle":"Magmatic phosphite and thermally polymerized phosphate 3.2 billion years ago: Implications for early life","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-29 18:18:36","doi":"10.21203/rs.3.rs-6529805/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"communications-earth-and-environment","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"commsenv","sideBox":"Learn more about [Communications Earth and Environment](https://www.nature.com/commsenv/)","snPcode":"","submissionUrl":"","title":"Communications Earth \u0026 Environment","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Communications Series","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"dc57fece-5dd6-48a0-8ebe-44cce0ceb1a6","owner":[],"postedDate":"May 29th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":48191043,"name":"Earth and environmental sciences/Solid Earth sciences/Geochemistry"},{"id":48191044,"name":"Earth and environmental sciences/Biogeochemistry/Element cycles"},{"id":48191045,"name":"Earth and environmental sciences/Solid Earth sciences/Geology/Precambrian geology"}],"tags":[],"updatedAt":"2025-11-14T08:10:51+00:00","versionOfRecord":{"articleIdentity":"rs-6529805","link":"https://doi.org/10.1038/s43247-025-02824-x","journal":{"identity":"communications-earth-and-environment","isVorOnly":false,"title":"Communications Earth \u0026 Environment"},"publishedOn":"2025-11-13 05:00:00","publishedOnDateReadable":"November 13th, 2025"},"versionCreatedAt":"2025-05-29 18:18:36","video":"","vorDoi":"10.1038/s43247-025-02824-x","vorDoiUrl":"https://doi.org/10.1038/s43247-025-02824-x","workflowStages":[]},"version":"v1","identity":"rs-6529805","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6529805","identity":"rs-6529805","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}