Mafic-ultramafic igneous rocks as a source of reactive phosphorus for the origin of life

Mafic-ultramafic igneous rocks as a source of reactive phosphorus for the origin of 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 Mafic-ultramafic igneous rocks as a source of reactive phosphorus for the origin of life Abu Baidya, Craig Walton, Joanna Kalita, Kristoffer Szilas, Marco Viccaro, and 6 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7915382/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Reduced and polymerized phosphorus species such as phosphite and pyrophosphate may have been crucial prebiotic substrates due to their higher reactivity and greater solubility, yet their sources remain debated and fluxes poorly constrained. Here, we show that mafic–ultramafic rocks on the early Earth could serve as a geologically sustainable source of reactive phosphorus via seafloor weathering. Analysis of mafic-ultramafic rocks from 15 locations reveals phosphite accounting for up to 7%, 24%, 17%, and 0.6% of total extracted phosphorus in olivine separates, peridotite, komatiite, and basalt, respectively, while pyrophosphate reached up to 5% and 0.4% in komatiite and basalt. Using a box model, we show that phosphite could have reached 1 µM in the deep ocean and 67 µM in lakes under low ultra-violet conditions on the prebiotic Earth. We conclude that mafic-ultramafic rocks on the early Earth and possibly other planetary bodies could be an important source of reactive phosphorus for the origin and early evolution of life. Earth and environmental sciences/Solid Earth sciences/Geochemistry Earth and environmental sciences/Solid Earth sciences/Mineralogy Earth and environmental sciences/Solid Earth sciences/Petrology Earth and environmental sciences/Planetary science/Astrobiology Earth and environmental sciences/Planetary science/Geochemistry Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction Phosphorus (P) is indispensable for life as a structural component of nucleic acids, cell membranes, and adenosine triphosphate (ATP). Among the major bioessential elements, however, P is the least abundant in surface environments compared to other major biogenic elements 1 and has no stable gaseous phase, limiting its availability to prebiotic chemistry on terrestrial planets. Under most habitable surface conditions, P occurs as orthophosphate (P 5+ ), an oxidized, sparingly soluble, and relatively inert species 2 . While this stability is key for the persistence of biological molecules, it hinders prebiotic phosphorylation reactions 3 . High concentrations of P 5+ may have been required for life’s origins, yet such environments were likely rare 4 . Alternatively, prebiotic chemistry may have drawn on more soluble and reactive P species, particularly phosphite (P 3+ ) and pyrophosphate (PP 5+ ) 5–7 . For example, PP 5+ can act as a phosphorylating agent 8 , a precursor to ATP-based metabolism, and a potential energy source for early life 9 . On the other hand, P 3+ is ca. 1,000 times more soluble than P 5+ in natural fluids, and more efficient at producing phosphorylated organics 6 , 7 , 10 . Furthermore, geochemical analyses of Paleoarchean carbonates and Neoarchean–Paleoproterozoic banded iron formations indicate that P 3+ comprised potentially 5–88% of dissolved inorganic P in the Archean ocean 11 , 12 . Two main abiotic mechanisms have been proposed for forming reactive, soluble P species. The first involves the aqueous dissolution of iron–nickel phosphides (e.g., schreibersite, (Fe,Ni)₃P), delivered by meteorites 13 or formed during contact-metamorphism 14 , 15 and lightning strikes 16 . Schreibersite corrosion releases P 3+ , PP 5+ , and other reactive and soluble P compounds 17 – 19 . The second mechanism involves thermal processing of P 5+ precursors in magmatic or metamorphic settings. Volcanic processes above ~ 1200°C can produce P 4 O 10 , which hydrates to PP 5+ and other higher-order polyphosphates; such species have been detected in volcanic fumaroles in Japan 20 . Dry-heating of alkali, ammonium, or divalent metal P 5+ salts can yield polyphosphates including PP 5+ , with higher yields in the presence of Fe–Cr–Ni-bearing minerals 7 , 21 , 22 . Metamorphic heating of phosphate precursors with Fe 2+ , H 2 , or organic matter can also reduce P 5+ to P 3+ , as shown by dry-heating of amorphous Fe-phosphate, where Fe 2+ oxidation accompanies P reduction 7 , 14 , 21 . Phosphite detected in Eoarchean carbonates and iron formations of amphibolite–granulite grade may reflect such metamorphic reduction 7 , 21 . Collectively, these studies indicate that low water activity, high temperature, and reducing conditions promote P³⁺ generation. Although the mechanisms for P 3+ and PP 5+ formation described above seem feasible, they are spatially and temporally limited, episodic, or restricted in scale, raising concerns about their ability to sustain widespread and continuous prebiotic P chemistry. In this study, we reveal a new geochemical source of reactive P species: magmatic mafic and ultramafic rocks and their associated fluid–rock interactions. These lithologies, which were volumetrically extensive on the early Earth and remain common on other planetary bodies, are characterized by high temperatures, low water activity, and high Fe 2+ -conditions that favour the formation and stabilization of reduced and polymerized P species. To evaluate this hypothesis, we analyzed a suite of mafic to ultramafic rocks representing the top and bottom of the prebiotic lithosphere, from 15 globally distributed locations (Supplementary Table 1). We chose basalt and komatiite because they were the dominant surface rock on the prebiotic and early Earth. Peridotite, particularly harzburgite and dunite were included to probe the mantle reservoir, the latter representing restite left after basalt and komatiite extraction from primitive mantle. Ultramafic rocks in particular are undersaturated with respect to apatite, meaning that olivine, which can contain several wt% P 23 , would be the main reservoir of P in these rocks so long as the fO 2 was above the Iron-Iron Wüstite buffer 24 below which native Fe and thus iron phosphides such as FeP and Fe 3 P are stabilised. Hence, we also investigated olivine separates from lherzolite peridotite, a pallasite meteorite, and basalt. Phosphorus was extracted from rock powders with an EDTA–NaOH solution (solid-to-solution ratio 1:10, shaken for 14–15h at room temperature), and concentrations of hypophosphite, P 3+ , P 5+ , and PP 5+ were quantified by ion chromatography coupled with inductively coupled plasma mass spectrometry (IC–ICP–MS; see Methods) 11 , 25 . Separate powder aliquots were analyzed for total P and major and trace element concentrations by bulk digestion and ICP-MS. Data from basalts in the Moodies Group (Barberton, South Africa) were taken from a previous study 15 . The compiled data were used to estimate the potential reserves of reactive P species—particularly P 3+ and PP 5+ —in the early oceanic crust. We further use these data to constrain a simple box model of the prebiotic ocean and of a volcanic lake where rock weathering would have liberated P 3+ into solution. Our findings suggest that: (1) Earth’s crust in the Hadean to Archean may have contained reactive P species up to 0.70% of total P (with 0.34% P 3+ and 0.34% PP 5+ ) ; (2) early Earth mafic and ultramafic lithologies could have provided sustained sources of reactive P for prebiotic phosphorylation and early metabolic pathways; and (3) similar lithologies present on other planetary bodies such as Mars and Enceladus may harbour primary reactive P reservoirs suitable for prebiotic chemistry. Results and Discussion Phosphorus speciation in mafic and ultramafic rocks We find that the total P content is the lowest in peridotite (10–40 ppm with an average of 17 ppm). The olivine separate from the lherzolite contains a similarly low amount of P (20 ppm). Komatiite is P-enriched compared to peridotite (70–120 ppm, average 93 ppm), and basalt shows even higher enrichments (590–4110 ppm, average 2097 ppm) (Table 1 ). The olivine separate from basalt is P-depleted (40 ppm) compared to bulk average basalts, suggesting that most P in basalts is not olivine-hosted and instead perhaps present as apatite. Total P in the studied samples shows a good correlation with K 2 O with a r 2 value of 0.77 (Supplementary Fig. S3A). Overall, these trend reflect the incompatible behaviour of P during mantle melting and magmatic differentiation, which leads to progressive enrichment in differentiating melts until apatite saturation is reached 26 , 27 . Komatiite forms due to a higher degree of partial melting of mantle compared to basalt 28 , which explains enhanced P concentrations in the lower degree melts (basalt) compared with higher degree melts (komatiite). Table 1 Concentrations of phosphorus species in the studied mafic and ultramafic rocks Rock types Average proportions (%) Average Concentration (ppm)* P(III) SD P(III) P(V) SD P(V) PP(V) SD PP(V) P(III) SD P(III) P(V) SD P(V) PP(V) SD PP(V) Basalt (n = 6) 0.22 0.24 99.52 0.33 0.26 0.11 4.78 7.95 2086.79 1447.80 5.09 4.73 Komatiite (n = 5) 4.89 6.82 92.71 8.74 2.40 2.03 4.37 6.17 81.52 11.94 2.11 1.86 Olivine sep. (n = 2) 5.33 1.99 92.35 5.27 2.31 3.27 1.46 0.16 28.08 14.64 0.46 0.65 Peridotite (n = 15) 5.52 7.05 94.46 7.03 0.02 0.07 0.97 1.34 21.69 23.04 0.01 0.03 Median proportions (%) Median Concentration (ppm) Basalt (n = 6) 0.14 99.63 0.28 1.51 1912.93 3.83 Komatiite (n = 5) 1.71 96.43 1.96 1.60 87.35 1.60 Olivine sep. (n = 2) 3.06 96.94 0.00 1.46 28.08 0.46 Peridotite (n = 15) 2.20 97.80 0.00 0.44 17.75 0.00 * Concentrations are estimated using ratios of P-species in the EDTA-NaOH extract, extraction yield, and total P contents Our P speciation analyses reveal that mafic and ultramafic rocks are important repositories of reduced and polymerized P species, particularly P 3+ and PP 5+ . The IC-ICP-MS measurements of EDTA–NaOH extracts indicate that komatiite, olivine separates, and peridotite samples contain markedly higher proportions of P 3+ relative to the total P content compared to basalt. The average percentages of P 3+ in basalt, komatiite, olivine separates, and peridotite are 0.22, 4.89, 5.33, and 5.52%, respectively, relative to total P (Table 1 , Fig. 1 ). One possible explanation for the difference in P 3+ percentage in komatiite and basalt is the melt temperature. Previous experimental studies suggested that higher temperature may enhance the formation of P 3+ from P 5+ in the Fe-P-O system 7 , 21 . As komatiites formed at a higher temperature than basalts (ca. >1600 o C vs < 1200 o C) 29 , 30 , P 3+ , which preferentially forms at higher temperatures in the presence of Fe 2+ , 7,21 may therefore have been thermodynamically favored. Alternatively, it is possible that P 3+ behaves more compatibly than P 5+ during mantle melting, such that it is depleted in basalts, which form from a lower degree of partial melting than komatiites. The latter is consistent with relatively higher P 3+ contents in restite dunite and olivine separates. Regarding PP 5+ , komatiite and basalt samples exhibit moderate abundances (2.40 and 0.26%, respectively, relative to total P), whereas this species is below the detection limit in olivine and peridotite (Table 1 , Fig. 1 ). We speculate that PP 5+ behaves like an incompatible species, such that it becomes enriched during mantle melting. This inference is supported by strong correlations between PP 5+ and molybdenum (Mo) as well as potassium (K), both of which behave incompatibly during partial melting and correlate with total P content (Supplementary Fig. S3). This suggests that as residual melts become enriched in P, this increases the probability of phosphate–phosphate interactions and thus PP 5+ formation. These observations are consistent with experimental results showing that polyphosphates can form in heated mixtures of basalt and apatite at temperatures above the basalt melting point (~ 1200°C), where the enhanced mobility of P 5+ in the melt was proposed to promote polymerization reactions 20 . To estimate the concentrations of different P species in bulk samples, we normalized the speciation data to the extraction yield, determined by comparison to the total P contents. These calculations show that P 3+ concentrations remain relatively constant across the studied lithologies (average of 4.78 ppm, 4.37 ppm, 1.46 ppm, and 0.97 ppm for basalt, komatiite, olivine separates, and peridotite, respectively), while P 5+ concentrations follow the same pattern as of total P (Fig. 1 ). Absolute concentrations of PP 5+ in basalt and komatiite are also similar (5 ppm and 2 ppm, respectively; Fig. 1 ). The observed distribution of reduced and polymerized P species reflects primary magmatic processes rather than secondary alteration. The studied komatiite samples show no or minor alteration 31 . Similarly, the olivine separates and peridotite samples do not show any visible alteration, and the positive correlation between CaO and Al 2 O 3 in these samples is indicative of magmatic differentiation (Supplementary Fig. S2). Some basalt samples, particularly from the Moodies Group show minor alteration in the form of secondary sericite formation; however, altered samples were not considered 15 . Furthermore, K 2 O is positively correlated with U in the basalt samples, consistent with the incompatible and fluid-mobile element geochemistry being controlled by magmatic factors and not controlled by secondary processes (Supplementary Fig. S1 D). Importantly, fluid-induced alteration would imply the addition of water; however, experimental studies have suggested that elevated water activity prohibits the formation of reduced and polymerized P species from phosphate percursors 7 , 21 , 22 . Therefore, P 3+ and PP 5+ are unlikely to be the product of secondary alteration. In contrast, a recent study noted magmatic PP 5+ in two natural olivine samples 32 while experimental studies suggest that magmatic glass may host polyphosphates 33 . We therefore conclude that the observed P 3+ and PP 5+ are magmatic in origin. Basalt and komatiite may have represented the principal magmatic sources of reactive P species on the early Earth. Although the relative abundances of P 3+ and PP 5+ are lower in basalts compared to ultramafic rocks, their substantially higher total P contents result in comparable absolute concentrations of reactive P species (Fig. 1 ). Moreover, both basalt and komatiite are highly susceptible to chemical weathering and commonly contain volcanic glass, which alters more rapidly than mineral phases 24 . These properties make basaltic and komatiitic lithologies not only efficient hosts for reactive P but also more accessible contributors of magmatic reactive P species via fluid-rock interaction, underscoring their relevance in prebiotic geochemical cycles. Reactive phosphorus reservoirs in Earth’s crust The P speciation data in the studied samples allow us to evaluate the crustal reservoir of reactive P species through time. We considered the evolving composition of the oceanic crust between 3.5 and 2.0 Ga, integrating the declining abundance of komatiite and increasing dominance of basalt 34 with their respective reactive P profiles (see Method section for details; Fig. 2 a). The results show similar values of relative abundance and absolute concentration of P 3+ and PP 5+ in the oceanic crust in this timeframe such that relative percentages of P 3+ and PP 5+ vary between 0.33 − 0.22% and 0.28 − 0.22%, respectively, whereas the absolute concentrations of these two species vary between 4–5 ppm during this interval (Fig. 2 a). Importantly, these results suggest that oceanic crust and seamount volcanoes could have been a long-term and stable source of reactive and soluble P species via seafloor weathering. Phosphite availability in early ocean and lake environments Our discovery of P 3+ and PP 5+ in mafic igneous rocks implies that seafloor weathering could have supplied reactive P to the deep ocean on the early Earth, with important implications for the origin of life on Earth and other habitable worlds and for the bioavailability of P for ancient ecosystems. To estimate the concentration of P 3+ in the prebiotic ocean resulting from this flux, we constructed a simple box model in which seafloor weathering was the sole source. Sinks included photochemical oxidation 36 and dark oxidation (dark oxidation refers to natural oxidation of P 3+ in the absence of UV-radiation) of P 3+ to P 5+ (Fig. 3 A; see Methods for details) 7 . The seafloor weathering flux of P 3+ was derived from the corresponding P 5+ weathering flux proposed by Syverson et al. 35 , scaled by the crustal P 3+ /P 5+ ratio measured in this study (Table 1 ). Because CO 2 uptake by mafic rocks is proportional to P release 35 , the global seafloor P weathering flux is tied to volcanic CO 2 outgassing. The photochemical sink was assumed to equal the flux of P 3+ from the deep ocean to the surface, where rapid photo-oxidation reduces surface concentrations effectively to zero 36 . The abiotic dark oxidation sink was calculated from the half-life of 600,000 years estimated by Herschy et al. 7 . Mineral precipitation was neglected due to the high solubility of P 3+ relative to P 5 + 7 . A similar model could not be constructed for PP 5+ because its solubility and sinks in aqueous systems are not well constrained. The model suggests that the prebiotic deep ocean could have maintained an upper-bound steady-state reservoir of ~ 1 nM P 3+ in a scenario with high CO 2 outgassing rates and therefore intense seafloor weathering (Fig. 4 A). Under conditions that suppress photo-oxidation, such as attenuation at shallower depth (< 10m), an atmospheric haze, or due to the presence of dissolved Fe 2+ , 37,38 steady-state concentrations could have increased up to 1–2 µM. In the prebiotic lake analogue, drainage would have supplied the dominant P 3+ flux, with both photochemical and dark oxidation acting as sinks (Fig. 3 B–D). The lake inventory is highly sensitive to the oxidative half-life of P 3+ , which depends on UV penetration. Under strong photo-oxidation (half-life < 1 year), steady-state concentrations would have remained below 0.1 µM (Fig. 4 B). However, under restricted UV exposure—due to organic surface layers 39 or density stratification 4 —steady-state concentrations could have been much higher, reaching up to 67 µM (Fig. 4 B). Implications for the origin of life and planetary habitability This study bears several important implications for the origin of life and planetary habitability. Beyond Earth, our results suggest that magmatic P³⁺ may occur in meteorites and in the crusts of other planetary bodies. On Mars, Enceladus, and Europa, interactions between water and mafic–ultramafic rocks may have created environments that some studies have proposed as potential cradles for life’s origin 40 , 41 . Meteorite-derived phosphides may have provided reactive P on Mars 18 , 36 , but no comparable source has yet been identified for Enceladus or Europa. However, phosphide content varies widely among meteorite classes, with carbonaceous and ordinary chondrites containing only minor proportions of total P as phosphide (< 1% and < 10%, respectively) 18 , 36 . Our data instead point to mafic and ultramafic surface rocks on Mars as a significant reservoir, capable of releasing P³⁺ and P⁵⁺ during water–rock interaction. The chondritic rocky cores of Enceladus and Europa 42 , 43 may likewise host substantial reduced P, potentially up to ~ 24% of total P (as observed in some peridotite samples), which could be mobilised into their subsurface oceans via water–rock interaction 44 , 45 . As the oceans of these moons are shielded from ultraviolet radiation by overlying ice, P³⁺ may have accumulated to higher concentrations than on early Earth, where photochemical oxidation would have limited its stability. While P⁵⁺ has already been detected in Enceladus’ ocean 46 , we suggest that P³⁺ is also likely present and could have supported prebiotic phosphorylation reactions. On Earth, our findings contrast with the prevailing view that nearly all P outside the core exists in oxidised form 24 . Instead, a cryptic reduced reservoir has probably persisted since planetary accretion, supplying reactive species to surface environments. This implies a much larger endogenous supply of reactive P to prebiotic chemistry than previously assumed. Mafic and ultramafic rocks could also have provided reactive P to prebiotic hydrothermal systems, oceans, and lakes. Fluids from hydrothermal vents—long regarded as plausible sites for life’s emergence 47 —may have contained both P 3+ and PP 5+ derived from rock–fluid interaction. Previous work has shown that phosphate can form high-energy PP 5+ compounds via reactions with acetyl phosphate in Fe-sulfide/silicate precipitates 48 ; our results suggest an additional pathway for PP 5+ delivery that would increase the availability of energy-rich phosphates in vent systems. In lacustrine settings, P 3+ concentrations may have reached tens of micromolar under UV-dark conditions maintained by Fe 2+ , 37 an organic surface layer, 39 or stratification 4 , particularly if the supply was stable. Although experimental constraints on the concentrations of P 3+ required for phosphorylation are limited 6 , 10 , a komatiitic source with higher P 3+ /P 5+ ratio coupled with wet–dry cycles that enhance solute accumulation and the greater reactivity of P 3+ relative to P 5+ , suggests that such concentrations could have been sufficient to drive prebiotic phosphorylation chemistry. In the ocean, reactive P released from mafic crust may have constituted a stable, long-term source of P during the Archean. The availability of P 5+ in Archean seawater remains debated, with some studies arguing for high P 5+ abundance 49–51 and others suggesting strong P-limitation 52 – 54 . During this time, meteorites have likely been an important source of P 3+ , owing to its greater solubility 12 . Our results indicate that in the absence of extraterrestrial or biological inputs, and under strong UV irradiation, the standing concentration of P 3+ supplied by seafloor weathering was likely low. This may help explain the relatively late emergence of P 3+ -utilising enzymes near the Archean–Proterozoic boundary 55 . Nonetheless, the high solubility of P 3+ and its photochemical oxidation would have provided an indirect flux of P 5+ to the early biosphere. Recent estimates indicate that during the Great Oxidation Event, P 3+ accounted for 5–88% of dissolved inorganic P, at concentrations up to 0.17 µM 11 . In light of our new data, this reservoir may have been at least in part sustained by crustal weathering under reduced UV flux or augmented by early biological inputs of reduced P. Altogether, our findings show that mafic and ultramafic rocks could have been an important reservoir of reactive P on the early Earth. Up to ~ 0.70% of total crustal P may have occurred as P 3+ and PP 5+ in the Archean, yielding upper bound P 3+ oceanic concentrations of hundreds of nanomolar and lake concentrations of tens of micromolar. Transiently elevated levels of these reactive P species could have fuelled prebiotic phosphorylation while maintaining a stable, long-term P source in the Archean ocean. Comparable P 3+ reservoirs on Mars, Europa, and Enceladus may likewise have expanded the availability of reactive P and the potential for life. Methods Quantification of phosphorus species in rock samples All glass and plastic containers used in this study were cleaned with 1M HCl followed by two rinses with hot water and dried. Glass containers were subsequently baked at 500°C to ensure complete removal of organic contaminants. Rock and mineral samples were initially crushed into millimeter-sized chips, then sequentially washed with methanol and 1M HCl (four times each) to eliminate surface contaminants. After rinsing five times with deionized (DI) water, the samples were freeze-dried and further pulverized using a ball mill. For phosphorus (P) extraction, an aliquot (ca. 0.2–0.25 g) of the powdered sample was treated with an ethylenediaminetetraacetic acid-sodium hydroxide (EDTA-NaOH) solution (0.05M EDTA and 0.25M NaOH) at a solid-to-solution ratio of 1:10 for 14–15 hours at room temperature on a rotary shaker. The EDTA-NaOH solution was prepared by dissolving Na₂EDTA (Sigma-Aldrich) and 10M NaOH (Thermo Scientific) in DI water. The extraction was conducted in 15 mL Falcon tubes. Following extraction, the solutions were centrifuged at 3000 rpm for 15–20 minutes, and the clear supernatant was collected for analysis. Four P species, namely hypophosphite, phosphite, phosphate, and pyrophosphate, were analyzed using an ion chromatography-inductively coupled plasma mass spectrometry (IC-ICP-MS) system 25 . The IC system (Thermo Scientific Dionex ICS-6000) was equipped with a Dionex AS-AP autosampler, an IonPac AS17-C separation column (250 mm, 2 mm bore), an IonPac AG17-G guard column (50 mm, 2 mm bore), and an ADRS-600 suppressor (2 mm). Prior to analysis, the extracted supernatant was diluted 25-fold to prevent column interference from high metal and EDTA concentrations. Chromatographic separation was achieved using a KOH eluent gradient (1–40 mM over 20 min), maintained at 40 mM for additional 25 min, then ramped back to 1 mM over next 5 min, with a constant flow rate of 0.5 mL/min. The IC suppressor outlet was directly coupled to a Scott-type quartz spray chamber via a 1 mL/min nebulizer, connected to an Element 2 ICP-MS. The suppressor was regenerated with deionized water at 1 mL/min using an external pump. The ICP-MS was operated in medium resolution mode with the following parameters: RF power, 1183 W; cool gas flow, 16 L/min; and sample gas flow, 1.1 L/min. Data acquisition involved 3-minute chromatograms per P species, comprising 1 min of pre-peak background, 1 min of peak monitoring, and 1 min of post-peak background measurements. Chromatographic data were smoothed using OriginLab software with a Fast Fourier Transform (FFT) filter (window size = 5 points), and peak areas were used for P quantification. Calibration standards for all four P species—prepared from NaH₂PO₂·H₂O (hypophosphite), Na₂HPO₃·5H₂O (P 3+ ), NaH₂PO₄ (P 5+ ), and Na₄P₂O₇ (PP 5+ )—were matrix-matched to the sample EDTA-NaOH solution and covered a concentration range of 0.2–100 ppb. These standards were analyzed identically to the samples, and their peak integrals were used to construct calibration curves for quantification. The starting reagents (HCl, EDTA, NAOH, DI water) were analyzed as procedural blanks and corrections were made. Blanks prepared with EDTA–NaOH but without samples were analyzed to assess background contributions, revealing minor levels of P(V) and PP(V). Method detection limits (MDLs) in the solutions were determined to be < 0.1 ppb for P 3+ and P 5+ , 0.1 ppb for hypophosphite, and 0.2 ppb for PP 5+ . Whole rock analysis Approximately 0.30–0.60 g of powder from each of the samples was 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 -AES analyses. Reproducibility was assessed with rock standards OREAS-45d (50:50 blend of mineralised lateritic soil and barren soil), OREAS-905 (a blend of copper oxide ore and rhyodacite), and MRGeo-08, and with two or three sample replicates. It was found to be 5% or better for P and trace elements. Estimation of crustal reactive phosphorus reservoir To estimate the temporal evolution of crustal reactive P, we considered the compositional change of oceanic crust over geological time. During the Archean, komatiite and basalt were the dominant lithologies forming the oceanic crust, although komatiite generation declined significantly after 2.5 Ga. Following the approach of Greber et al. 34 , who used titanium isotope systematics to infer the proportions of major lithologies in the continental crust from 3.5 to 2.0 Ga, we adopted analogous ratios for the oceanic crust, assuming it was composed solely of basalt and komatiite. For instance, at 3.5 Ga, the oceanic crust is modelled to consist of 64% basalt and 36% komatiite, based on the estimated 27% basalt and 15% komatiite contributions to the contemporaneous continental crust 34 . Using these proportions, together with our constrained average concentrations of P 3+ and PP 5+ in basalt and komatiite, we quantified the evolving abundance of reactive P species in the oceanic crust from 3.5 to 2.0 Ga. Estimations of reactive phosphorus in prebiotic ocean and lakes The crustal estimation of P 3+ enables us to quantify its source flux into the early Earth's ocean by seafloor weathering. On the other hand, previous studies have identified potential sinks for P 3+ in the early Earth’s oceans 7 , 36 . These source and sink fluxes were incorporated into a box model to estimate the concentration of P 3+ in the early Earth's deep ocean. Syverson et al. (2021) 35 demonstrated that aqueous alteration of mafic crust under anoxic conditions can liberate P 5+ into seawater through reaction with carbonic acid. Based on laboratory experiments, they derived an empirical P 5+ -to-CO₂ release ratio (R PC ) of 4 ± 1 µmol/mmol. This ratio was used to estimate the global P 5+ weathering flux by multiplying R PC with the global volcanic CO₂ outgassing flux (J volc ) and the fraction of CO₂ consumed during reaction with mafic crust (f wx ). Building on this framework, we extended the P 5+ weathering flux to estimate the P 3+ weathering flux, incorporating our measured P 3+ -to-P 5+ ratio (P 3+ /P 5+ ) in mafic igneous rocks. The resulting P 3+ input to the prebiotic ocean (P hyd ) is given by: P hyd = J volc × R PC × f wx × (P 3+ /P 5+ ) Reported values for J volc on modern Earth range from 5 to 20 × 10 12 mol/yr 35 . We explored a broader range of 1–100 × 10 12 mol/yr to account for the possibility of enhanced volcanic activity on the early Earth 56 , 57 . Syverson et al. 35 varied f wx between 0.1 and 0.9 to represent a range of Archean conditions; in our model, we fixed f wx at 0.9, assuming an ocean-dominated prebiotic Earth 58 where seafloor alteration acted as the primary carbon sink. The P 3+ /P 5+ ratio was varied from 0.001 to 0.01, with an average value of 0.002 based on our measurements. The main sinks of P 3+ are linked with its photochemical 36 and dark 7 oxidation to P 5+ , among which photochemical oxidation dominates. Ritson et al. 36 demonstrated that of P 3+ is rapidly oxidized to of P 5+ under ultraviolet irradiation, with complete conversion occurring within hours. We therefore assumed that all of P 3+ transported to the surface ocean was instantaneously oxidized. The photochemical sink (P photo ) was calculated as: P photo = F mix × [P 3+ ] deep where F mix , the global marine upwelling flux, was fixed at 10 15 m 3 /yr 59 , and [P 3+ ] deep is the deep ocean P 3+ concentration, calculated by numerical integration (see below). To account for dark (non-photochemical) oxidation of P 3+ , we used a half-life (τ) of 600,000 years under Archean conditions, as reported by Herschy et al. 7 . The associated first-order rate constant (k ox ) was calculated as: k ox = ln(2)/τ. The total dark oxidation sink (P dark_ox ) was then: P dark_ox = k ox × V deep × [P 3+ ] deep where V deep , the volume of the deep ocean 60 , was set to 10 18 m 3 . The overall mass balance for the deep ocean P 3+ reservoir, i.e., the rate of change of P 3+ accumulation in deep ocean, can be described by the following ordinary differential equation: $$\:\frac{dP}{dt}=\frac{\left({P}_{hyd}-\:{P}_{photo}\:-{P}_{dark\_ox}\right)\:}{{V}_{deep}}$$ or explicitly: $$\:\frac{dP}{dt}=\frac{\left(\left({J}_{volc}*{R}_{PC}*{f}_{wx}*\frac{{P}^{3+}}{{P}^{5+}}\right)-\:\left({F}_{mix}*{P}_{deep}^{3+}\right)\:-\left({k}_{ox}*{V}_{deep}*{P}_{deep}^{3+}\right)\right)\:}{{V}_{deep}}$$ This differential equation was numerically solved using the odeint solver in Python. The model was run until steady state was reached, and the resulting equilibrium concentration of [P 3+ ] deep was recorded and plotted. The code developed to solve this equation is given in the Supplementary material. To quantify steady-state P 3+ concentrations, we modeled a hydrothermally fed soda lake under closed-basin conditions, where hydrologic inputs are fully balanced by evaporation. In such systems, dissolved species approach equilibrium when removal by oxidative sinks (e.g., photolysis, hydrolysis, or precipitation) offsets influx. The steady-state concentration C of a solute can be expressed by: $$\:{C}_{i}=\:\frac{{F}_{i}*{L}_{i}}{V}$$ Where C i is the concentration (mol/L) of a species i, F i is the flux (mol/year) of species i entering the lake system, L i is the lifetime (year) of species i in the lake environment, and V is volume (litre) of water in the lake. We considered the accumulation of P 3+ in the hypothetical lake, exploring lifetime as a free parameter and then highlighting the expected value for anoxic early Earth systems based on available experimental evidence. For values of flux and volume, we considered a hydrothermally active soda lake with similar hydrological properties to Mono Lake in California 4 . In other words, the hypothetical lake is a prebiotic analogue of modern Mono lake. For Mono lake, volume of lake V = 3 * 10 12 litre and P 5+ inflow rate F P5+ is = 1 × 10 − 3 mmol/year 4 . With the observed ratios of P 3+ /P 5+ in the basalt samples, we have considered three phosphite annual inflow rate (F P3+ ) values − 0.001, 0.01 and 0.1 µmol/year. We have considered two endmember cases in terms of the extent of photochemical oxidation in these types of lake. If the lake was exposed to UV-radiation, phosphite oxidation would have been rapid leading to sub-nanomolar or lower concentrations of P 3+ . On the other extreme end, we assumed that photochemistry is not occurring, requiring efficient UV attenuation in the lake surface. This may be accomplished by the accumulation of effective UV-absorbing organics in surficial ‘scum’ layers 39 or by the density segregation of the lake to form basal dark layers 4 . Declarations Acknowledgements This work was financially supported by a Natural Environment Research Council (NERC< UKRI) Frontiers grant and a Leverhulme Trust research grant (RPG-2022-313) to EES (NE/V010824/1) and Marie Skłodowska-Curie Actions grant to ASB (EP/Y026497/1). CRW acknowledges funding from the NOMIS Foundation in the form of an ETH-NOMIS Fellowship. The complete data for this study is 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; ASB, KS, PS, SA, MV, EN, SM and EES provided samples; ASB and JK analyzed the samples; EES and CRW did the modelling; ASB, SM, EES, and CRW led the data interpretation. ASB prepared the first draft of the manuscript with contribution from CRW and EES. The manuscript was reviewed and edited by all authors. Competing Interest Statement The authors declare that they have no competing interests. Data and materials availability All data including the Code developed for modelling are available in the main text or in the supplementary materials. Phosphorus speciation data can also be accessed from British Geological Survey at https://doi.org/10.5285/18ee8cec-f141-4544-b210-aa3a4f0a557b. References Anders E, Ebihara M (1982) Solar-system abundances of the elements. Geochim Cosmochim Acta 46:2363–2380 Tyrrell T (1999) The relative influences of nitrogen and phosphorus on oceanic primary production. Nature 400:525–531 Pasek MA, Gull M, Herschy B (2017) Phosphorylation on the early earth. Chem Geol 475:149–170 Walton CR, Hao J, Schönbächler M, Shorttle O (2025) Large closed-basin lakes sustainably supplied phosphate during the origins of life. Sci Adv 11:eadq0027 Gulick A (1955) Phosphorus as a factor in the origin of life. Am Sci 43:479–489 Schwartz AW (2006) Phosphorus in prebiotic chemistry. Philos Trans R Soc B Biol Sci 361:1743–1749 Herschy B et al (2018) Archean phosphorus liberation induced by iron redox geochemistry. Nat Commun 9:1346 Gull M, Omran A, Feng T, Pasek MA (2020) Silicate-, magnesium ion-, and urea-induced prebiotic phosphorylation of uridine via pyrophosphate: revisiting the hot drying water pool scenario. Life vol. 10 Nicholls JWF et al (2023) On the potential roles of phosphorus in the early evolution of energy metabolism. Front Microbiol 14 Gull M, Feng T, Bracegirdle J, Abbott-Lyon H, Pasek MA (2023) Organophosphorus Compound Formation Through the Oxidation of Reduced Oxidation State Phosphorus Compounds on the Hadean Earth. J Mol Evol 91:60–75 Baidya AS et al (2025) Bioavailable phosphite in the surface ocean during the Great Oxidation Event. Nat Commun 16:4825 Pasek MA, Harnmeijer JP, Buick R, Gull M, Atlas Z (2013) Evidence for reactive reduced phosphorus species in the early Archean ocean. Proc. Natl. Acad. Sci. 110, 10089–10094 Pasek MA (2008) Rethinking early Earth phosphorus geochemistry. Proc. Natl. Acad. Sci. 105, 853–858 Britvin SN, Murashko MN, Vapnik Y, Polekhovsky YS, Krivovichev SV (2015) Earth’s Phosphides in Levant and insights into the source of Archean prebiotic phosphorus. Sci Rep 5:8355 Baidya AS, Gehringer MM, Savaniu C, Heubeck C, Stüeken EE (2025) Magmatic and thermally produced reactive phosphorus 3.2 billion years ago and its implications for early life. Commun. Earth Environ. Accepted Hess BL, Piazolo S, Harvey J (2021) Lightning strikes as a major facilitator of prebiotic phosphorus reduction on early Earth. Nat Commun 12:1535 Pasek MA, Kee TP, Bryant DE, Pavlov AA, Lunine (2008) J. I. Production of Potentially Prebiotic Condensed Phosphates by Phosphorus Redox Chemistry. Angew Chemie Int Ed 47:7918–7920 Pasek MA, Lauretta DS (2005) Aqueous corrosion of phosphide minerals from iron meteorites: A highly reactive source of prebiotic phosphorus on the surface of the early Earth. Astrobiology 5:515–535 Bryant DE, Kee TP (2006) Direct evidence for the availability of reactive, water soluble phosphorus on the early Earth. H-Phosphinic acid from the Nantan meteorite. Chem Commun 2344–2346. 10.1039/B602651F Yamagata Y, Watanabe H, Saitoh M, Namba T (1991) Volcanic production of polyphosphates and its relevance to prebiotic evolution. Nature 352:516–519 Baidya AS, Pasek MA, Stüeken EE (2024) Moderate and high-temperature metamorphic conditions produced diverse phosphorous species for the origin of life. Commun Earth Environ 5:1–12 Keefe AD, Miller SL (1995) Are polyphosphates or phosphate esters prebiotic reagents? J Mol Evol 41:693–702 Bekker T et al (2021) Experimental and Ab Initio Investigation of the Formation of Phosphoran Olivine. ACS Earth Sp Chem 5:1373–1383 Walton CR et al (2021) Phosphorus mineral evolution and prebiotic chemistry: From minerals to microbes. Earth Sci Rev 221:103806 Baidya AS, Stüeken EE (2024) On-line chloride removal from ion chromatography for trace-level analyses of phosphite and other anions by coupled ion chromatography–inductively coupled plasma mass spectrometry. Rapid Commun Mass Spectrom 38:e9665 Cox GM, Lyons TW, Mitchell RN, Hasterok D, Gard M (2018) Linking the rise of atmospheric oxygen to growth in the continental phosphorus inventory. Earth Planet Sci Lett 489:28–36 Horton F (2015) Did phosphorus derived from the weathering of large igneous provinces fertilize the Neoproterozoic ocean? Geochem Geophys Geosyst 16:1723–1738 Arndt N, Barnes S, Lesher C (2008) Komatiite. Cambridge University Press Mole DR et al (2014) Archean komatiite volcanism controlled by the evolution of early continents. Proc. Natl. Acad. Sci. 111, 10083–10088 Herzberg C et al (2007) Temperatures in ambient mantle and plumes: Constraints from basalts, picrites, and komatiites. Geochem Geophys Geosyst 8 Nisbet EG et al (1987) Uniquely fresh 2.7 Ga komatiites from the Belingwe greenstone belt. Zimbabwe Geology 15:1147–1150 Abbatiello J, Henson JE, Pasek M (2024) Phosphorus availability from olivine for biospheres. Front Astron Sp Sci 11 Holm NG (2014) Glasses as sources of condensed phosphates on the early earth. Geochem Trans 15:8 Greber ND et al (2017) Titanium isotopic evidence for felsic crust and plate tectonics 3.5 billion years ago. Sci (80-) 357:1271–1274 Syverson DD et al (2021) Nutrient supply to planetary biospheres from anoxic weathering of mafic oceanic crust. Geophys. Res. Lett. 48, eGL094442 (2021) Ritson DJ, Mojzsis SJ, Sutherland JD (2020) Supply of phosphate to early Earth by photogeochemistry after meteoritic weathering. Nat Geosci 13:344–348 Ranjan S et al (2021) UV Transmission in Natural Waters on Prebiotic Earth. Astrobiology 22:242–262 Nisbet EG, Cann JR, Lee C, Dover V (1995) Origins of photosynthesis. Nature 373:479–480 Walton CR, Shorttle O (2021) Scum of the Earth: A Hypothesis for Prebiotic Multi-Compartmentalised Environments. Life vol. 11 Clark BC et al (2021) Origin of Life on Mars: Suitability and Opportunities. Life vol. 11 Parkinson CD, Liang M-C, Yung YL, Kirschivnk JL (2008) Habitability of Enceladus: Planetary Conditions for Life. Orig Life Evol Biosph 38:355–369 Sekine Y et al (2015) High-temperature water–rock interactions and hydrothermal environments in the chondrite-like core of Enceladus. Nat Commun 6:8604 Kuskov OL, Kronrod VA (2005) Internal structure of Europa and Callisto. Icarus 177:550–569 Hsu H-W et al (2015) Ongoing hydrothermal activities within Enceladus. Nature 519:207–210 Melwani Daswani M, Vance SD, Mayne MJ, Glein CR (2021) A Metamorphic Origin for Europa’s Ocean. Geophys. Res. Lett. 48, e2021GL094143 Postberg F et al (2023) Detection of phosphates originating from Enceladus’s ocean. Nature 618:489–493 Martin W, Baross J, Kelley D, Russell MJ (2008) Hydrothermal vents and the origin of life. Nat Rev Microbiol 6:805–814 Barge LM et al (2014) Pyrophosphate synthesis in iron mineral films and membranes simulating prebiotic submarine hydrothermal precipitates. Geochim Cosmochim Acta 128:1–12 Brady MP, Tostevin R, Tosca NJ (2022) Marine phosphate availability and the chemical origins of life on Earth. Nat Commun 13:5162 Ingalls M, Grotzinger JP, Present T, Rasmussen B, Fischer WW (2022) Carbonate-associated phosphate (CAP) indicates elevated phosphate availability in Neoarchean shallow marine environments. Geophys. Res. Lett. 49, eGL098100 (2022) Rasmussen B, Muhling JR, Tosca NJ (2024) Nanoparticulate apatite and greenalite in oldest, well-preserved hydrothermal vent precipitates. Sci Adv 10:eadj4789 Jones C, Nomosatryo S, Crowe SA, Bjerrum CJ, Canfield DE (2015) Iron oxides, divalent cations, silica, and the early earth phosphorus crisis. Geology 43:135–138 Rego ES et al (2023) Low-phosphorus concentrations and important ferric hydroxide scavenging in Archean seawater. PNAS Nexus 2:pgad025 Reinhard CT et al (2017) Evolution of the global phosphorus cycle. Nature 541:386–389 Boden JS, Zhong J, Anderson RE, Stüeken EE (2024) Timing the evolution of phosphorus-cycling enzymes through geological time using phylogenomics. Nat Commun 15:3703 Richter FM (1985) Models for the Archean thermal regime. Earth Planet Sci Lett 73:350–360 Herzberg C, Condie K, Korenaga J (2010) Thermal history of the Earth and its petrological expression. Earth Planet Sci Lett 292:79–88 Korenaga J, Planavsky NJ, Evans DA (2017) D. Global water cycle and the coevolution of the Earth’s interior and surface environment. Philos Trans R Soc Math Phys Eng Sci 375:20150393 Walker JCG (1990) Numerical adventures with geochemical cycles. Oxford University Press Henderson P, Henderson GM (2009) The Cambridge handbook of earth science data (Vol. 277). Cambridge University Press Additional Declarations There is NO Competing Interest. Supplementary Files 251021Baidyaetal.crustalphosphiteSupplement.docx Supplementary Material Cite Share Download PDF Status: Under Review 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-7915382","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":563188966,"identity":"56f0ec06-3267-40c6-8473-8c7865ef12cc","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":563188967,"identity":"fe984dac-e500-4e61-831a-692b0a2aa2d9","order_by":1,"name":"Craig Walton","email":"","orcid":"","institution":"ETH Zurich","correspondingAuthor":false,"prefix":"","firstName":"Craig","middleName":"","lastName":"Walton","suffix":""},{"id":563188968,"identity":"44e90231-662c-4978-ab91-50b11ed78770","order_by":2,"name":"Joanna Kalita","email":"","orcid":"https://orcid.org/0009-0006-5836-6613","institution":"University of St. Andrews","correspondingAuthor":false,"prefix":"","firstName":"Joanna","middleName":"","lastName":"Kalita","suffix":""},{"id":563188969,"identity":"8678d3cb-1642-4268-a886-eed8df8e1059","order_by":3,"name":"Kristoffer Szilas","email":"","orcid":"","institution":"University of Copenhagen","correspondingAuthor":false,"prefix":"","firstName":"Kristoffer","middleName":"","lastName":"Szilas","suffix":""},{"id":563188970,"identity":"aefdeb95-f1ad-4a39-ac8c-bb63e01cc4f7","order_by":4,"name":"Marco Viccaro","email":"","orcid":"","institution":"Università di Catania","correspondingAuthor":false,"prefix":"","firstName":"Marco","middleName":"","lastName":"Viccaro","suffix":""},{"id":563188971,"identity":"04a857d3-2e06-4f6a-82ff-bda03b7624bf","order_by":5,"name":"Paul Savage","email":"","orcid":"https://orcid.org/0000-0001-8464-0264","institution":"University of St. Andrews","correspondingAuthor":false,"prefix":"","firstName":"Paul","middleName":"","lastName":"Savage","suffix":""},{"id":563188972,"identity":"16e0d387-8268-4bee-bd38-2581bfefd58a","order_by":6,"name":"Stuart Allison","email":"","orcid":"","institution":"University of St Andrews","correspondingAuthor":false,"prefix":"","firstName":"Stuart","middleName":"","lastName":"Allison","suffix":""},{"id":563188973,"identity":"a95c4b72-64df-48c6-977f-fd9502d21ce3","order_by":7,"name":"Euan Nisbet","email":"","orcid":"","institution":"Royal Holloway University of London","correspondingAuthor":false,"prefix":"","firstName":"Euan","middleName":"","lastName":"Nisbet","suffix":""},{"id":563188974,"identity":"79eba66c-4621-4c4e-9835-a74dc132a42d","order_by":8,"name":"Maria Schönbächler","email":"","orcid":"https://orcid.org/0000-0003-4304-214X","institution":"ETH Zürich","correspondingAuthor":false,"prefix":"","firstName":"Maria","middleName":"","lastName":"Schönbächler","suffix":""},{"id":563188975,"identity":"d5b3bc7c-760f-482f-bee5-011a0f8d9d54","order_by":9,"name":"Sami Mikhail","email":"","orcid":"https://orcid.org/0000-0001-5276-0229","institution":"University of St Andrews","correspondingAuthor":false,"prefix":"","firstName":"Sami","middleName":"","lastName":"Mikhail","suffix":""},{"id":563188976,"identity":"d752deb0-b7cf-4d80-901e-f016e8f287f0","order_by":10,"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":"2025-10-21 16:55:41","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7915382/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7915382/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":99761108,"identity":"7df60956-ff29-4a71-97cd-174bdc19594a","added_by":"auto","created_at":"2026-01-08 06:59:25","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":176203,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAbundance and speciation of phosphorus in mafic and ultramafic rocks. Bottom panel:\u003c/strong\u003e Box plots showing the relative abundance of phosphorus species—phosphate (P⁵\u003csup\u003e+\u003c/sup\u003e), phosphite (P³\u003csup\u003e+\u003c/sup\u003e), and pyrophosphate (PP⁵\u003csup\u003e+\u003c/sup\u003e)—expressed as a percentage of total extracted P in EDTA–NaOH solutions. Komatiite, olivine, and peridotite samples exhibit higher proportions of P³\u003csup\u003e+\u003c/sup\u003e compared to basalt, while PP\u003csup\u003e5+\u003c/sup\u003e is enriched in komatiites but largely absent in olivine and peridotite. \u003cstrong\u003eTop panel:\u003c/strong\u003e Estimated concentrations of each P species in bulk rock (ppm), calculated using total P content, extraction yield, and speciation data from the EDTA–NaOH extracts. Phosphate concentrations are highest in basalt and decrease progressively in komatiite, olivine, and peridotite. In contrast, P\u003csup\u003e3+\u003c/sup\u003e concentrations are broadly similar across all lithologies.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7915382/v1/a2531de4b801fd47017c3b5d.png"},{"id":99761109,"identity":"ec16db51-7786-44be-b558-46651696122e","added_by":"auto","created_at":"2026-01-08 06:59:25","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":153406,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCrustal reservoir of reactive phosphorus species.\u003c/strong\u003e Temporal evolution (3.5–2.0 Ga) of phosphite (P\u003csup\u003e3+\u003c/sup\u003e) and pyrophosphate (PP\u003csup\u003e5+\u003c/sup\u003e) in the oceanic crust, shown as both relative proportions (%) and absolute concentrations (ppm). Black lines (left y-axis) indicate the relative abundances of P\u003csup\u003e3+\u003c/sup\u003e and PP\u003csup\u003e5+\u003c/sup\u003e in %, while red lines (right y-axis) denote their estimated concentrations in ppm. Estimates are based on the evolving proportion of basalt and komatiite in the crust\u003csup\u003e34\u003c/sup\u003e and the measured concentrations of P\u003csup\u003e3+\u003c/sup\u003e and PP\u003csup\u003e5+\u003c/sup\u003e in these lithologies (see Method section for details). The declining trend in reactive P proportions is attributed to the progressive decrease in komatiite content over time. Absolute concentrations of both species in the oceanic crust remain between 4-5 ppm across this time interval.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7915382/v1/8760719dba277b03db05a70a.png"},{"id":99798069,"identity":"57fe82bd-3e74-40e2-8508-f634cc68065b","added_by":"auto","created_at":"2026-01-08 13:47:11","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":587997,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eConceptual models for phosphite (P\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e3+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e) cycling in early Earth ocean and lake environments. (A) \u003c/strong\u003eSchematic representation of the box model components used to estimate P\u003csup\u003e3+\u003c/sup\u003e concentrations in the deep ocean. The primary source is ocean floor weathering, while major sinks include photochemical oxidation in the sunlit surface ocean (driven by UV radiation) and dark oxidation in deeper waters. (B-D) Box models for estimating P\u003csup\u003e3+\u003c/sup\u003e concentrations in a prebiotic Mono Lake analogue. Riverine input is the dominant source, while photochemical and dark oxidation serve as sinks. (C) A stratified lake scenario in which UV radiation is attenuated, either by the formation of an organic-rich surface scum\u003csup\u003e24\u003c/sup\u003e or by density stratification\u003csup\u003e4\u003c/sup\u003e, resulting in reduced P\u003csup\u003e3+\u003c/sup\u003e oxidation and higher concentrations. (D) An unstratified lake with full UV exposure, leading to enhanced photochemical oxidation and lower P\u003csup\u003e3+\u003c/sup\u003e retention.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7915382/v1/d9856a4070e71d1d66169b7b.png"},{"id":99761112,"identity":"2f6a200a-45c1-48e4-a9eb-1a2493a455f4","added_by":"auto","created_at":"2026-01-08 06:59:25","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":433646,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eEstimated concentrations of phosphite (P\u003c/strong\u003e\u003csup\u003e\u003cstrong\u003e3+\u003c/strong\u003e\u003c/sup\u003e\u003cstrong\u003e) in early ocean and prebiotic lake environments. (A)\u003c/strong\u003e Modelled P\u003csup\u003e3+\u003c/sup\u003e concentrations in the deep ocean as a function of volcanic CO₂ flux. Estimates incorporate two oxidative scenarios: combined photochemical and dark oxidation (red line) and dark oxidation only (black line). Upper-bound values assume a P-to-CO₂ flux ratio (R\u003csub\u003ePC\u003c/sub\u003e) of 5 (based on the highest experimental value\u003csup\u003e35\u003c/sup\u003e) and the maximum P\u003csup\u003e3+\u003c/sup\u003e/P\u003csup\u003e5+\u003c/sup\u003e ratio of 0.01 observed in the studied samples. Lower-bound estimates are based on an R\u003csub\u003ePC\u003c/sub\u003e of 3 and a P\u003csup\u003e3+\u003c/sup\u003e/P\u003csup\u003e5+\u003c/sup\u003e ratio of 0.001. Modern CO\u003csub\u003e2\u003c/sub\u003e flux are from Syverson et al\u003csup\u003e35\u003c/sup\u003e. Given the elevated volcanic activity on the early Earth\u003csup\u003e28,29\u003c/sup\u003e, a CO₂ flux of 100 × 10\u003csup\u003e12\u003c/sup\u003e mol yr\u003csup\u003e-1\u003c/sup\u003e is considered the most realistic. (B) Estimated P\u003csup\u003e3+\u003c/sup\u003e concentrations in a prebiotic Mono Lake analogue as a function of P\u003csup\u003e3+\u003c/sup\u003e half-life. Upper and lower bounds correspond to the highest and lowest measured P\u003csup\u003e3+\u003c/sup\u003e/P\u003csup\u003e5+\u003c/sup\u003e ratios in the studied samples. The longevity of P\u003csup\u003e3+\u003c/sup\u003e is strongly influenced by UV exposure: the highest concentrations occur under UV-shielded conditions, where photochemical oxidation is suppressed and P\u003csup\u003e3+\u003c/sup\u003e half-life is extended to that in dark-oxidation-only scenarios (0.6 Ma)\u003csup\u003e7\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7915382/v1/00c4ebf4e1422729be9e7c16.png"},{"id":100356418,"identity":"8418d0af-ed27-40f1-a3dc-f7b360d4c24c","added_by":"auto","created_at":"2026-01-16 07:08:45","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2077855,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7915382/v1/612be3aa-bfa7-4a3c-8e24-5b0aad7c08a1.pdf"},{"id":99798113,"identity":"bffcbd39-a222-4138-a73d-6604cdc69fa6","added_by":"auto","created_at":"2026-01-08 13:47:18","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":475184,"visible":true,"origin":"","legend":"Supplementary Material","description":"","filename":"251021Baidyaetal.crustalphosphiteSupplement.docx","url":"https://assets-eu.researchsquare.com/files/rs-7915382/v1/3a1e69b509213b8b0e7b7980.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Mafic-ultramafic igneous rocks as a source of reactive phosphorus for the origin of life","fulltext":[{"header":"Introduction","content":"\u003cp\u003ePhosphorus (P) is indispensable for life as a structural component of nucleic acids, cell membranes, and adenosine triphosphate (ATP). Among the major bioessential elements, however, P is the least abundant in surface environments compared to other major biogenic elements\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e\u003c/sup\u003e and has no stable gaseous phase, limiting its availability to prebiotic chemistry on terrestrial planets. Under most habitable surface conditions, P occurs as orthophosphate (P\u003csup\u003e5+\u003c/sup\u003e), an oxidized, sparingly soluble, and relatively inert species\u003csup\u003e\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u003c/sup\u003e. While this stability is key for the persistence of biological molecules, it hinders prebiotic phosphorylation reactions\u003csup\u003e\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. High concentrations of P\u003csup\u003e5+\u003c/sup\u003e may have been required for life\u0026rsquo;s origins, yet such environments were likely rare\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eAlternatively, prebiotic chemistry may have drawn on more soluble and reactive P species, particularly phosphite (P\u003csup\u003e3+\u003c/sup\u003e) and pyrophosphate (PP\u003csup\u003e5+\u003c/sup\u003e)\u003csup\u003e5\u0026ndash;7\u003c/sup\u003e. For example, PP\u003csup\u003e5+\u003c/sup\u003e can act as a phosphorylating agent\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u003c/sup\u003e, a precursor to ATP-based metabolism, and a potential energy source for early life\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e\u003c/sup\u003e. On the other hand, P\u003csup\u003e3+\u003c/sup\u003e is ca. 1,000 times more soluble than P\u003csup\u003e5+\u003c/sup\u003e in natural fluids, and more efficient at producing phosphorylated organics\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. Furthermore, geochemical analyses of Paleoarchean carbonates and Neoarchean\u0026ndash;Paleoproterozoic banded iron formations indicate that P\u003csup\u003e3+\u003c/sup\u003e comprised potentially 5\u0026ndash;88% of dissolved inorganic P in the Archean ocean\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eTwo main abiotic mechanisms have been proposed for forming reactive, soluble P species. The first involves the aqueous dissolution of iron\u0026ndash;nickel phosphides (e.g., schreibersite, (Fe,Ni)₃P), delivered by meteorites\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e or formed during contact-metamorphism\u003csup\u003e\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e and lightning strikes\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e. Schreibersite corrosion releases P\u003csup\u003e3+\u003c/sup\u003e, PP\u003csup\u003e5+\u003c/sup\u003e, and other reactive and soluble P compounds\u003csup\u003e\u003cspan additionalcitationids=\"CR18\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e\u003c/sup\u003e. The second mechanism involves thermal processing of P\u003csup\u003e5+\u003c/sup\u003e precursors in magmatic or metamorphic settings. Volcanic processes above ~\u0026thinsp;1200\u0026deg;C can produce P\u003csub\u003e4\u003c/sub\u003eO\u003csub\u003e10\u003c/sub\u003e, which hydrates to PP\u003csup\u003e5+\u003c/sup\u003e and other higher-order polyphosphates; such species have been detected in volcanic fumaroles in Japan\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e. Dry-heating of alkali, ammonium, or divalent metal P\u003csup\u003e5+\u003c/sup\u003e salts can yield polyphosphates including PP\u003csup\u003e5+\u003c/sup\u003e, with higher yields in the presence of Fe\u0026ndash;Cr\u0026ndash;Ni-bearing minerals\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. Metamorphic heating of phosphate precursors with Fe\u003csup\u003e2+\u003c/sup\u003e, H\u003csub\u003e2\u003c/sub\u003e, or organic matter can also reduce P\u003csup\u003e5+\u003c/sup\u003e to P\u003csup\u003e3+\u003c/sup\u003e, as shown by dry-heating of amorphous Fe-phosphate, where Fe\u003csup\u003e2+\u003c/sup\u003e oxidation accompanies P reduction\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. Phosphite detected in Eoarchean carbonates and iron formations of amphibolite\u0026ndash;granulite grade may reflect such metamorphic reduction\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. Collectively, these studies indicate that low water activity, high temperature, and reducing conditions promote P\u0026sup3;⁺ generation.\u003c/p\u003e \u003cp\u003eAlthough the mechanisms for P\u003csup\u003e3+\u003c/sup\u003e and PP\u003csup\u003e5+\u003c/sup\u003e formation described above seem feasible, they are spatially and temporally limited, episodic, or restricted in scale, raising concerns about their ability to sustain widespread and continuous prebiotic P chemistry. In this study, we reveal a new geochemical source of reactive P species: magmatic mafic and ultramafic rocks and their associated fluid\u0026ndash;rock interactions. These lithologies, which were volumetrically extensive on the early Earth and remain common on other planetary bodies, are characterized by high temperatures, low water activity, and high Fe\u003csup\u003e2+\u003c/sup\u003e-conditions that favour the formation and stabilization of reduced and polymerized P species.\u003c/p\u003e \u003cp\u003eTo evaluate this hypothesis, we analyzed a suite of mafic to ultramafic rocks representing the top and bottom of the prebiotic lithosphere, from 15 globally distributed locations (Supplementary Table\u0026nbsp;1). We chose basalt and komatiite because they were the dominant surface rock on the prebiotic and early Earth. Peridotite, particularly harzburgite and dunite were included to probe the mantle reservoir, the latter representing restite left after basalt and komatiite extraction from primitive mantle. Ultramafic rocks in particular are undersaturated with respect to apatite, meaning that olivine, which can contain several wt% P\u003csup\u003e23\u003c/sup\u003e, would be the main reservoir of P in these rocks so long as the fO\u003csub\u003e2\u003c/sub\u003e was above the Iron-Iron W\u0026uuml;stite buffer\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e below which native Fe and thus iron phosphides such as FeP and Fe\u003csub\u003e3\u003c/sub\u003eP are stabilised. Hence, we also investigated olivine separates from lherzolite peridotite, a pallasite meteorite, and basalt. Phosphorus was extracted from rock powders with an EDTA\u0026ndash;NaOH solution (solid-to-solution ratio 1:10, shaken for 14\u0026ndash;15h at room temperature), and concentrations of hypophosphite, P\u003csup\u003e3+\u003c/sup\u003e, P\u003csup\u003e5+\u003c/sup\u003e, and PP\u003csup\u003e5+\u003c/sup\u003e were quantified by ion chromatography coupled with inductively coupled plasma mass spectrometry (IC\u0026ndash;ICP\u0026ndash;MS; see Methods)\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e,\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. Separate powder aliquots were analyzed for total P and major and trace element concentrations by bulk digestion and ICP-MS. Data from basalts in the Moodies Group (Barberton, South Africa) were taken from a previous study\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. The compiled data were used to estimate the potential reserves of reactive P species\u0026mdash;particularly P\u003csup\u003e3+\u003c/sup\u003e and PP\u003csup\u003e5+\u003c/sup\u003e\u0026mdash;in the early oceanic crust. We further use these data to constrain a simple box model of the prebiotic ocean and of a volcanic lake where rock weathering would have liberated P\u003csup\u003e3+\u003c/sup\u003e into solution.\u003c/p\u003e \u003cp\u003eOur findings suggest that: (1) Earth\u0026rsquo;s crust in the Hadean to Archean may have contained reactive P species up to 0.70% of total P (with 0.34% P\u003csup\u003e3+\u003c/sup\u003e and 0.34% PP\u003csup\u003e5+\u003c/sup\u003e) ; (2) early Earth mafic and ultramafic lithologies could have provided sustained sources of reactive P for prebiotic phosphorylation and early metabolic pathways; and (3) similar lithologies present on other planetary bodies such as Mars and Enceladus may harbour primary reactive P reservoirs suitable for prebiotic chemistry.\u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003cp\u003ePhosphorus speciation in mafic and ultramafic rocks\u003c/p\u003e \u003cp\u003eWe find that the total P content is the lowest in peridotite (10–40 ppm with an average of 17 ppm). The olivine separate from the lherzolite contains a similarly low amount of P (20 ppm). Komatiite is P-enriched compared to peridotite (70–120 ppm, average 93 ppm), and basalt shows even higher enrichments (590–4110 ppm, average 2097 ppm) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The olivine separate from basalt is P-depleted (40 ppm) compared to bulk average basalts, suggesting that most P in basalts is not olivine-hosted and instead perhaps present as apatite. Total P in the studied samples shows a good correlation with K\u003csub\u003e2\u003c/sub\u003eO with a r\u003csup\u003e2\u003c/sup\u003e value of 0.77 (Supplementary Fig. S3A). Overall, these trend reflect the incompatible behaviour of P during mantle melting and magmatic differentiation, which leads to progressive enrichment in differentiating melts until apatite saturation is reached\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e,\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. Komatiite forms due to a higher degree of partial melting of mantle compared to basalt\u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e, which explains enhanced P concentrations in the lower degree melts (basalt) compared with higher degree melts (komatiite).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c11\" colnum=\"11\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c12\" colnum=\"12\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c13\" colnum=\"13\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eConcentrations of phosphorus species in the studied mafic and ultramafic rocks\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"13\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eRock types\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colspan=\"5\" nameend=\"c6\" namest=\"c2\"\u003e \u003cp\u003eAverage proportions (%)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colspan=\"5\" nameend=\"c12\" namest=\"c8\"\u003e \u003cp\u003eAverage Concentration (ppm)*\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/th\u003e\u003c/tr\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eP(III)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSD P(III)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eP(V)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eSD P(V)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePP(V)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eSD PP(V)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eP(III)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003eSD P(III)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003eP(V)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c11\"\u003e \u003cp\u003eSD P(V)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c12\"\u003e \u003cp\u003ePP(V)\u003c/p\u003e \u003c/th\u003e\u003cth align=\"left\" colname=\"c13\"\u003e \u003cp\u003eSD PP(V)\u003c/p\u003e \u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBasalt (n = 6)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.22\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.24\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e99.52\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.33\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.26\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.11\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e4.78\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e7.95\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e2086.79\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e1447.80\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e5.09\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e4.73\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKomatiite (n = 5)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4.89\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.82\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e92.71\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.74\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.40\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e2.03\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e4.37\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e6.17\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e81.52\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e11.94\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e2.11\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e1.86\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOlivine sep. (n = 2)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.33\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.99\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e92.35\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e5.27\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.31\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e3.27\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.46\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e0.16\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e28.08\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e14.64\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e0.46\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e0.65\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePeridotite (n = 15)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.52\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.05\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e94.46\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.03\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.02\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.07\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.97\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e1.34\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e21.69\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e \u003cp\u003e23.04\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e0.01\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c13\"\u003e \u003cp\u003e0.03\u003c/p\u003e \u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"5\" nameend=\"c6\" namest=\"c2\"\u003e \u003cp\u003eMedian proportions (%)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colspan=\"5\" nameend=\"c12\" namest=\"c8\"\u003e \u003cp\u003eMedian Concentration (ppm)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eBasalt (n = 6)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.14\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e99.63\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.28\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.51\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e1912.93\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e3.83\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eKomatiite (n = 5)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.71\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e96.43\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.96\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.60\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e87.35\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e1.60\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOlivine sep. (n = 2)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e3.06\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e96.94\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.00\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e1.46\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e28.08\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e0.46\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePeridotite (n = 15)\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2.20\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e97.80\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.00\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e0.44\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c9\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c10\"\u003e \u003cp\u003e17.75\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c11\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c12\"\u003e \u003cp\u003e0.00\u003c/p\u003e \u003c/td\u003e\u003ctd align=\"left\" colname=\"c13\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"13\"\u003e* Concentrations are estimated using ratios of P-species in the EDTA-NaOH extract, extraction yield, and total P contents\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e \u003cp\u003e\u003c/p\u003e \u003cp\u003eOur P speciation analyses reveal that mafic and ultramafic rocks are important repositories of reduced and polymerized P species, particularly P\u003csup\u003e3+\u003c/sup\u003e and PP\u003csup\u003e5+\u003c/sup\u003e. The IC-ICP-MS measurements of EDTA–NaOH extracts indicate that komatiite, olivine separates, and peridotite samples contain markedly higher proportions of P\u003csup\u003e3+\u003c/sup\u003e relative to the total P content compared to basalt. The average percentages of P\u003csup\u003e3+\u003c/sup\u003e in basalt, komatiite, olivine separates, and peridotite are 0.22, 4.89, 5.33, and 5.52%, respectively, relative to total P (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). One possible explanation for the difference in P\u003csup\u003e3+\u003c/sup\u003e percentage in komatiite and basalt is the melt temperature. Previous experimental studies suggested that higher temperature may enhance the formation of P\u003csup\u003e3+\u003c/sup\u003e from P\u003csup\u003e5+\u003c/sup\u003e in the Fe-P-O system\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. As komatiites formed at a higher temperature than basalts (ca. \u0026gt;1600 \u003csup\u003eo\u003c/sup\u003eC vs \u0026lt; 1200 \u003csup\u003eo\u003c/sup\u003eC)\u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e,\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e, P\u003csup\u003e3+\u003c/sup\u003e, which preferentially forms at higher temperatures in the presence of Fe\u003csup\u003e2+\u003c/sup\u003e,\u003csup\u003e7,21\u003c/sup\u003e may therefore have been thermodynamically favored. Alternatively, it is possible that P\u003csup\u003e3+\u003c/sup\u003e behaves more compatibly than P\u003csup\u003e5+\u003c/sup\u003e during mantle melting, such that it is depleted in basalts, which form from a lower degree of partial melting than komatiites. The latter is consistent with relatively higher P\u003csup\u003e3+\u003c/sup\u003e contents in restite dunite and olivine separates.\u003c/p\u003e \u003cp\u003eRegarding PP\u003csup\u003e5+\u003c/sup\u003e, komatiite and basalt samples exhibit moderate abundances (2.40 and 0.26%, respectively, relative to total P), whereas this species is below the detection limit in olivine and peridotite (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). We speculate that PP\u003csup\u003e5+\u003c/sup\u003e behaves like an incompatible species, such that it becomes enriched during mantle melting. This inference is supported by strong correlations between PP\u003csup\u003e5+\u003c/sup\u003e and molybdenum (Mo) as well as potassium (K), both of which behave incompatibly during partial melting and correlate with total P content (Supplementary Fig. S3). This suggests that as residual melts become enriched in P, this increases the probability of phosphate–phosphate interactions and thus PP\u003csup\u003e5+\u003c/sup\u003e formation. These observations are consistent with experimental results showing that polyphosphates can form in heated mixtures of basalt and apatite at temperatures above the basalt melting point (~ 1200°C), where the enhanced mobility of P\u003csup\u003e5+\u003c/sup\u003e in the melt was proposed to promote polymerization reactions\u003csup\u003e\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eTo estimate the concentrations of different P species in bulk samples, we normalized the speciation data to the extraction yield, determined by comparison to the total P contents. These calculations show that P\u003csup\u003e3+\u003c/sup\u003e concentrations remain relatively constant across the studied lithologies (average of 4.78 ppm, 4.37 ppm, 1.46 ppm, and 0.97 ppm for basalt, komatiite, olivine separates, and peridotite, respectively), while P\u003csup\u003e5+\u003c/sup\u003e concentrations follow the same pattern as of total P (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Absolute concentrations of PP\u003csup\u003e5+\u003c/sup\u003e in basalt and komatiite are also similar (5 ppm and 2 ppm, respectively; Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe observed distribution of reduced and polymerized P species reflects primary magmatic processes rather than secondary alteration. The studied komatiite samples show no or minor alteration\u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. Similarly, the olivine separates and peridotite samples do not show any visible alteration, and the positive correlation between CaO and Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e in these samples is indicative of magmatic differentiation (Supplementary Fig. S2). Some basalt samples, particularly from the Moodies Group show minor alteration in the form of secondary sericite formation; however, altered samples were not considered\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. Furthermore, K\u003csub\u003e2\u003c/sub\u003eO is positively correlated with U in the basalt samples, consistent with the incompatible and fluid-mobile element geochemistry being controlled by magmatic factors and not controlled by secondary processes (Supplementary Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003eD). Importantly, fluid-induced alteration would imply the addition of water; however, experimental studies have suggested that elevated water activity prohibits the formation of reduced and polymerized P species from phosphate percursors\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e,\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. Therefore, P\u003csup\u003e3+\u003c/sup\u003e and PP\u003csup\u003e5+\u003c/sup\u003e are unlikely to be the product of secondary alteration. In contrast, a recent study noted magmatic PP\u003csup\u003e5+\u003c/sup\u003e in two natural olivine samples\u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e\u003c/sup\u003e while experimental studies suggest that magmatic glass may host polyphosphates\u003csup\u003e\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e. We therefore conclude that the observed P\u003csup\u003e3+\u003c/sup\u003e and PP\u003csup\u003e5+\u003c/sup\u003e are magmatic in origin.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eBasalt and komatiite may have represented the principal magmatic sources of reactive P species on the early Earth. Although the relative abundances of P\u003csup\u003e3+\u003c/sup\u003e and PP\u003csup\u003e5+\u003c/sup\u003e are lower in basalts compared to ultramafic rocks, their substantially higher total P contents result in comparable absolute concentrations of reactive P species (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Moreover, both basalt and komatiite are highly susceptible to chemical weathering and commonly contain volcanic glass, which alters more rapidly than mineral phases\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. These properties make basaltic and komatiitic lithologies not only efficient hosts for reactive P but also more accessible contributors of magmatic reactive P species via fluid-rock interaction, underscoring their relevance in prebiotic geochemical cycles.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eReactive phosphorus reservoirs in Earth’s crust\u003c/p\u003e \u003cp\u003eThe P speciation data in the studied samples allow us to evaluate the crustal reservoir of reactive P species through time. We considered the evolving composition of the oceanic crust between 3.5 and 2.0 Ga, integrating the declining abundance of komatiite and increasing dominance of basalt\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e with their respective reactive P profiles (see Method section for details; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). The results show similar values of relative abundance and absolute concentration of P\u003csup\u003e3+\u003c/sup\u003e and PP\u003csup\u003e5+\u003c/sup\u003e in the oceanic crust in this timeframe such that relative percentages of P\u003csup\u003e3+\u003c/sup\u003e and PP\u003csup\u003e5+\u003c/sup\u003e vary between 0.33 − 0.22% and 0.28 − 0.22%, respectively, whereas the absolute concentrations of these two species vary between 4–5 ppm during this interval (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). Importantly, these results suggest that oceanic crust and seamount volcanoes could have been a long-term and stable source of reactive and soluble P species via seafloor weathering.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003ePhosphite availability in early ocean and lake environments\u003c/p\u003e \u003cp\u003eOur discovery of P\u003csup\u003e3+\u003c/sup\u003e and PP\u003csup\u003e5+\u003c/sup\u003e in mafic igneous rocks implies that seafloor weathering could have supplied reactive P to the deep ocean on the early Earth, with important implications for the origin of life on Earth and other habitable worlds and for the bioavailability of P for ancient ecosystems. To estimate the concentration of P\u003csup\u003e3+\u003c/sup\u003e in the prebiotic ocean resulting from this flux, we constructed a simple box model in which seafloor weathering was the sole source. Sinks included photochemical oxidation\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e and dark oxidation (dark oxidation refers to natural oxidation of P\u003csup\u003e3+\u003c/sup\u003e in the absence of UV-radiation) of P\u003csup\u003e3+\u003c/sup\u003e to P\u003csup\u003e5+\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA; see Methods for details)\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. The seafloor weathering flux of P\u003csup\u003e3+\u003c/sup\u003e was derived from the corresponding P\u003csup\u003e5+\u003c/sup\u003e weathering flux proposed by Syverson et al.\u003csup\u003e35\u003c/sup\u003e, scaled by the crustal P\u003csup\u003e3+\u003c/sup\u003e/P\u003csup\u003e5+\u003c/sup\u003e ratio measured in this study (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Because CO\u003csub\u003e2\u003c/sub\u003e uptake by mafic rocks is proportional to P release\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e, the global seafloor P weathering flux is tied to volcanic CO\u003csub\u003e2\u003c/sub\u003e outgassing. The photochemical sink was assumed to equal the flux of P\u003csup\u003e3+\u003c/sup\u003e from the deep ocean to the surface, where rapid photo-oxidation reduces surface concentrations effectively to zero\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e. The abiotic dark oxidation sink was calculated from the half-life of 600,000 years estimated by Herschy et al.\u003csup\u003e7\u003c/sup\u003e. Mineral precipitation was neglected due to the high solubility of P\u003csup\u003e3+\u003c/sup\u003e relative to P\u003csup\u003e5 + 7\u003c/sup\u003e. A similar model could not be constructed for PP\u003csup\u003e5+\u003c/sup\u003e because its solubility and sinks in aqueous systems are not well constrained.\u003c/p\u003e \u003cp\u003eThe model suggests that the prebiotic deep ocean could have maintained an upper-bound steady-state reservoir of ~ 1 nM P\u003csup\u003e3+\u003c/sup\u003e in a scenario with high CO\u003csub\u003e2\u003c/sub\u003e outgassing rates and therefore intense seafloor weathering (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA). Under conditions that suppress photo-oxidation, such as attenuation at shallower depth (\u0026lt; 10m), an atmospheric haze, or due to the presence of dissolved Fe\u003csup\u003e2+\u003c/sup\u003e,\u003csup\u003e37,38\u003c/sup\u003e steady-state concentrations could have increased up to 1–2 µM.\u003c/p\u003e \u003cp\u003eIn the prebiotic lake analogue, drainage would have supplied the dominant P\u003csup\u003e3+\u003c/sup\u003e flux, with both photochemical and dark oxidation acting as sinks (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB–D). The lake inventory is highly sensitive to the oxidative half-life of P\u003csup\u003e3+\u003c/sup\u003e, which depends on UV penetration. Under strong photo-oxidation (half-life \u0026lt; 1 year), steady-state concentrations would have remained below 0.1 µM (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB). However, under restricted UV exposure—due to organic surface layers\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e or density stratification\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e—steady-state concentrations could have been much higher, reaching up to 67 µM (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB).\u003c/p\u003e \u003cp\u003eImplications for the origin of life and planetary habitability\u003c/p\u003e \u003cp\u003eThis study bears several important implications for the origin of life and planetary habitability. Beyond Earth, our results suggest that magmatic P³⁺ may occur in meteorites and in the crusts of other planetary bodies. On Mars, Enceladus, and Europa, interactions between water and mafic–ultramafic rocks may have created environments that some studies have proposed as potential cradles for life’s origin\u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e,\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. Meteorite-derived phosphides may have provided reactive P on Mars\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e,\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e, but no comparable source has yet been identified for Enceladus or Europa. However, phosphide content varies widely among meteorite classes, with carbonaceous and ordinary chondrites containing only minor proportions of total P as phosphide (\u0026lt; 1% and \u0026lt; 10%, respectively)\u003csup\u003e\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e,\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e. Our data instead point to mafic and ultramafic surface rocks on Mars as a significant reservoir, capable of releasing P³⁺ and P⁵⁺ during water–rock interaction. The chondritic rocky cores of Enceladus and Europa\u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e,\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e may likewise host substantial reduced P, potentially up to ~ 24% of total P (as observed in some peridotite samples), which could be mobilised into their subsurface oceans via water–rock interaction\u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e,\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e. As the oceans of these moons are shielded from ultraviolet radiation by overlying ice, P³⁺ may have accumulated to higher concentrations than on early Earth, where photochemical oxidation would have limited its stability. While P⁵⁺ has already been detected in Enceladus’ ocean\u003csup\u003e\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e, we suggest that P³⁺ is also likely present and could have supported prebiotic phosphorylation reactions.\u003c/p\u003e \u003cp\u003eOn Earth, our findings contrast with the prevailing view that nearly all P outside the core exists in oxidised form\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e. Instead, a cryptic reduced reservoir has probably persisted since planetary accretion, supplying reactive species to surface environments. This implies a much larger endogenous supply of reactive P to prebiotic chemistry than previously assumed.\u003c/p\u003e \u003cp\u003eMafic and ultramafic rocks could also have provided reactive P to prebiotic hydrothermal systems, oceans, and lakes. Fluids from hydrothermal vents—long regarded as plausible sites for life’s emergence\u003csup\u003e\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u003c/sup\u003e—may have contained both P\u003csup\u003e3+\u003c/sup\u003e and PP\u003csup\u003e5+\u003c/sup\u003e derived from rock–fluid interaction. Previous work has shown that phosphate can form high-energy PP\u003csup\u003e5+\u003c/sup\u003e compounds via reactions with acetyl phosphate in Fe-sulfide/silicate precipitates\u003csup\u003e\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e\u003c/sup\u003e; our results suggest an additional pathway for PP\u003csup\u003e5+\u003c/sup\u003e delivery that would increase the availability of energy-rich phosphates in vent systems. In lacustrine settings, P\u003csup\u003e3+\u003c/sup\u003e concentrations may have reached tens of micromolar under UV-dark conditions maintained by Fe\u003csup\u003e2+\u003c/sup\u003e,\u003csup\u003e37\u003c/sup\u003e an organic surface layer,\u003csup\u003e39\u003c/sup\u003e or stratification\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e, particularly if the supply was stable. Although experimental constraints on the concentrations of P\u003csup\u003e3+\u003c/sup\u003e required for phosphorylation are limited\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e, a komatiitic source with higher P\u003csup\u003e3+\u003c/sup\u003e/P\u003csup\u003e5+\u003c/sup\u003e ratio coupled with wet–dry cycles that enhance solute accumulation and the greater reactivity of P\u003csup\u003e3+\u003c/sup\u003e relative to P\u003csup\u003e5+\u003c/sup\u003e, suggests that such concentrations could have been sufficient to drive prebiotic phosphorylation chemistry.\u003c/p\u003e \u003cp\u003eIn the ocean, reactive P released from mafic crust may have constituted a stable, long-term source of P during the Archean. The availability of P\u003csup\u003e5+\u003c/sup\u003e in Archean seawater remains debated, with some studies arguing for high P\u003csup\u003e5+\u003c/sup\u003e abundance\u003csup\u003e49–51\u003c/sup\u003e and others suggesting strong P-limitation\u003csup\u003e\u003cspan additionalcitationids=\"CR53\" citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e–\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e\u003c/sup\u003e. During this time, meteorites have likely been an important source of P\u003csup\u003e3+\u003c/sup\u003e, owing to its greater solubility\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. Our results indicate that in the absence of extraterrestrial or biological inputs, and under strong UV irradiation, the standing concentration of P\u003csup\u003e3+\u003c/sup\u003e supplied by seafloor weathering was likely low. This may help explain the relatively late emergence of P\u003csup\u003e3+\u003c/sup\u003e-utilising enzymes near the Archean–Proterozoic boundary\u003csup\u003e\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e\u003c/sup\u003e. Nonetheless, the high solubility of P\u003csup\u003e3+\u003c/sup\u003e and its photochemical oxidation would have provided an indirect flux of P\u003csup\u003e5+\u003c/sup\u003e to the early biosphere. Recent estimates indicate that during the Great Oxidation Event, P\u003csup\u003e3+\u003c/sup\u003e accounted for 5–88% of dissolved inorganic P, at concentrations up to 0.17 µM\u003csup\u003e11\u003c/sup\u003e. In light of our new data, this reservoir may have been at least in part sustained by crustal weathering under reduced UV flux or augmented by early biological inputs of reduced P.\u003c/p\u003e \u003cp\u003eAltogether, our findings show that mafic and ultramafic rocks could have been an important reservoir of reactive P on the early Earth. Up to ~ 0.70% of total crustal P may have occurred as P\u003csup\u003e3+\u003c/sup\u003e and PP\u003csup\u003e5+\u003c/sup\u003e in the Archean, yielding upper bound P\u003csup\u003e3+\u003c/sup\u003e oceanic concentrations of hundreds of nanomolar and lake concentrations of tens of micromolar. Transiently elevated levels of these reactive P species could have fuelled prebiotic phosphorylation while maintaining a stable, long-term P source in the Archean ocean. Comparable P\u003csup\u003e3+\u003c/sup\u003e reservoirs on Mars, Europa, and Enceladus may likewise have expanded the availability of reactive P and the potential for life.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003eQuantification of phosphorus species in rock samples\u003c/p\u003e\u003cp\u003eAll glass and plastic containers used in this study were cleaned with 1M HCl followed by two rinses with hot water and dried. Glass containers were subsequently baked at 500°C to ensure complete removal of organic contaminants. Rock and mineral samples were initially crushed into millimeter-sized chips, then sequentially washed with methanol and 1M HCl (four times each) to eliminate surface contaminants. After rinsing five times with deionized (DI) water, the samples were freeze-dried and further pulverized using a ball mill.\u003c/p\u003e\u003cp\u003eFor phosphorus (P) extraction, an aliquot (ca. 0.2–0.25 g) of the powdered sample was treated with an ethylenediaminetetraacetic acid-sodium hydroxide (EDTA-NaOH) solution (0.05M EDTA and 0.25M NaOH) at a solid-to-solution ratio of 1:10 for 14–15 hours at room temperature on a rotary shaker. The EDTA-NaOH solution was prepared by dissolving Na₂EDTA (Sigma-Aldrich) and 10M NaOH (Thermo Scientific) in DI water. The extraction was conducted in 15 mL Falcon tubes. Following extraction, the solutions were centrifuged at 3000 rpm for 15–20 minutes, and the clear supernatant was collected for analysis.\u003c/p\u003e\u003cp\u003eFour P species, namely hypophosphite, phosphite, phosphate, and pyrophosphate, were analyzed using an ion chromatography-inductively coupled plasma mass spectrometry (IC-ICP-MS) system\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. The IC system (Thermo Scientific Dionex ICS-6000) was equipped with a Dionex AS-AP autosampler, an IonPac AS17-C separation column (250 mm, 2 mm bore), an IonPac AG17-G guard column (50 mm, 2 mm bore), and an ADRS-600 suppressor (2 mm). Prior to analysis, the extracted supernatant was diluted 25-fold to prevent column interference from high metal and EDTA concentrations.\u003c/p\u003e\u003cp\u003eChromatographic separation was achieved using a KOH eluent gradient (1–40 mM over 20 min), maintained at 40 mM for additional 25 min, then ramped back to 1 mM over next 5 min, with a constant flow rate of 0.5 mL/min. The IC suppressor outlet was directly coupled to a Scott-type quartz spray chamber via a 1 mL/min nebulizer, connected to an Element 2 ICP-MS. The suppressor was regenerated with deionized water at 1 mL/min using an external pump. The ICP-MS was operated in medium resolution mode with the following parameters: RF power, 1183 W; cool gas flow, 16 L/min; and sample gas flow, 1.1 L/min. Data acquisition involved 3-minute chromatograms per P species, comprising 1 min of pre-peak background, 1 min of peak monitoring, and 1 min of post-peak background measurements.\u003c/p\u003e\u003cp\u003eChromatographic data were smoothed using OriginLab software with a Fast Fourier Transform (FFT) filter (window size = 5 points), and peak areas were used for P quantification. Calibration standards for all four P species—prepared from NaH₂PO₂·H₂O (hypophosphite), Na₂HPO₃·5H₂O (P\u003csup\u003e3+\u003c/sup\u003e), NaH₂PO₄ (P\u003csup\u003e5+\u003c/sup\u003e), and Na₄P₂O₇ (PP\u003csup\u003e5+\u003c/sup\u003e)—were matrix-matched to the sample EDTA-NaOH solution and covered a concentration range of 0.2–100 ppb. These standards were analyzed identically to the samples, and their peak integrals were used to construct calibration curves for quantification. The starting reagents (HCl, EDTA, NAOH, DI water) were analyzed as procedural blanks and corrections were made. Blanks prepared with EDTA–NaOH but without samples were analyzed to assess background contributions, revealing minor levels of P(V) and PP(V). Method detection limits (MDLs) in the solutions were determined to be \u0026lt; 0.1 ppb for P\u003csup\u003e3+\u003c/sup\u003e and P\u003csup\u003e5+\u003c/sup\u003e, 0.1 ppb for hypophosphite, and 0.2 ppb for PP\u003csup\u003e5+\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eWhole rock analysis\u003c/p\u003e\u003cp\u003eApproximately 0.30–0.60 g of powder from each of the samples was 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 -AES analyses. Reproducibility was assessed with rock standards OREAS-45d (50:50 blend of mineralised lateritic soil and barren soil), OREAS-905 (a blend of copper oxide ore and rhyodacite), and MRGeo-08, and with two or three sample replicates. It was found to be 5% or better for P and trace elements.\u003c/p\u003e\u003cp\u003eEstimation of crustal reactive phosphorus reservoir\u003c/p\u003e\u003cp\u003eTo estimate the temporal evolution of crustal reactive P, we considered the compositional change of oceanic crust over geological time. During the Archean, komatiite and basalt were the dominant lithologies forming the oceanic crust, although komatiite generation declined significantly after 2.5 Ga. Following the approach of Greber et al.\u003csup\u003e34\u003c/sup\u003e, who used titanium isotope systematics to infer the proportions of major lithologies in the continental crust from 3.5 to 2.0 Ga, we adopted analogous ratios for the oceanic crust, assuming it was composed solely of basalt and komatiite. For instance, at 3.5 Ga, the oceanic crust is modelled to consist of 64% basalt and 36% komatiite, based on the estimated 27% basalt and 15% komatiite contributions to the contemporaneous continental crust\u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. Using these proportions, together with our constrained average concentrations of P\u003csup\u003e3+\u003c/sup\u003e and PP\u003csup\u003e5+\u003c/sup\u003e in basalt and komatiite, we quantified the evolving abundance of reactive P species in the oceanic crust from 3.5 to 2.0 Ga.\u003c/p\u003e\u003cp\u003eEstimations of reactive phosphorus in prebiotic ocean and lakes\u003c/p\u003e\u003cp\u003eThe crustal estimation of P\u003csup\u003e3+\u003c/sup\u003e enables us to quantify its source flux into the early Earth's ocean by seafloor weathering. On the other hand, previous studies have identified potential sinks for P\u003csup\u003e3+\u003c/sup\u003e in the early Earth’s oceans\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e,\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e. These source and sink fluxes were incorporated into a box model to estimate the concentration of P\u003csup\u003e3+\u003c/sup\u003e in the early Earth's deep ocean. Syverson et al. (2021)\u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e demonstrated that aqueous alteration of mafic crust under anoxic conditions can liberate P\u003csup\u003e5+\u003c/sup\u003e into seawater through reaction with carbonic acid. Based on laboratory experiments, they derived an empirical P\u003csup\u003e5+\u003c/sup\u003e-to-CO₂ release ratio (R\u003csub\u003ePC\u003c/sub\u003e) of 4 ± 1 µmol/mmol. This ratio was used to estimate the global P\u003csup\u003e5+\u003c/sup\u003e weathering flux by multiplying R\u003csub\u003ePC\u003c/sub\u003e with the global volcanic CO₂ outgassing flux (J\u003csub\u003evolc\u003c/sub\u003e) and the fraction of CO₂ consumed during reaction with mafic crust (f\u003csub\u003ewx\u003c/sub\u003e).\u003c/p\u003e\u003cp\u003eBuilding on this framework, we extended the P\u003csup\u003e5+\u003c/sup\u003e weathering flux to estimate the P\u003csup\u003e3+\u003c/sup\u003e weathering flux, incorporating our measured P\u003csup\u003e3+\u003c/sup\u003e-to-P\u003csup\u003e5+\u003c/sup\u003e ratio (P\u003csup\u003e3+\u003c/sup\u003e/P\u003csup\u003e5+\u003c/sup\u003e) in mafic igneous rocks. The resulting P\u003csup\u003e3+\u003c/sup\u003e input to the prebiotic ocean (P\u003csub\u003ehyd\u003c/sub\u003e) is given by:\u003c/p\u003e\u003cp\u003eP\u003csub\u003ehyd\u003c/sub\u003e = J\u003csub\u003evolc\u003c/sub\u003e × R\u003csub\u003ePC\u003c/sub\u003e × f\u003csub\u003ewx\u003c/sub\u003e × (P\u003csup\u003e3+\u003c/sup\u003e/P\u003csup\u003e5+\u003c/sup\u003e)\u003c/p\u003e\u003cp\u003eReported values for J\u003csub\u003evolc\u003c/sub\u003e on modern Earth range from 5 to 20 × 10\u003csup\u003e12\u003c/sup\u003e mol/yr\u003csup\u003e35\u003c/sup\u003e. We explored a broader range of 1–100 × 10\u003csup\u003e12\u003c/sup\u003e mol/yr to account for the possibility of enhanced volcanic activity on the early Earth\u003csup\u003e\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e,\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e\u003c/sup\u003e. Syverson et al.\u003csup\u003e35\u003c/sup\u003e varied f\u003csub\u003ewx\u003c/sub\u003e between 0.1 and 0.9 to represent a range of Archean conditions; in our model, we fixed f\u003csub\u003ewx\u003c/sub\u003e at 0.9, assuming an ocean-dominated prebiotic Earth\u003csup\u003e\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e\u003c/sup\u003e where seafloor alteration acted as the primary carbon sink. The P\u003csup\u003e3+\u003c/sup\u003e/P\u003csup\u003e5+\u003c/sup\u003e ratio was varied from 0.001 to 0.01, with an average value of 0.002 based on our measurements.\u003c/p\u003e\u003cp\u003eThe main sinks of P\u003csup\u003e3+\u003c/sup\u003e are linked with its photochemical\u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e and dark\u003csup\u003e\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e oxidation to P\u003csup\u003e5+\u003c/sup\u003e, among which photochemical oxidation dominates. Ritson et al.\u003csup\u003e36\u003c/sup\u003e demonstrated that of P\u003csup\u003e3+\u003c/sup\u003e is rapidly oxidized to of P\u003csup\u003e5+\u003c/sup\u003e under ultraviolet irradiation, with complete conversion occurring within hours. We therefore assumed that all of P\u003csup\u003e3+\u003c/sup\u003e transported to the surface ocean was instantaneously oxidized. The photochemical sink (P\u003csub\u003ephoto\u003c/sub\u003e) was calculated as:\u003c/p\u003e\u003cp\u003eP\u003csub\u003ephoto\u003c/sub\u003e = F\u003csub\u003emix\u003c/sub\u003e × [P\u003csup\u003e3+\u003c/sup\u003e]\u003csub\u003edeep\u003c/sub\u003e\u003c/p\u003e\u003cp\u003ewhere F\u003csub\u003emix\u003c/sub\u003e, the global marine upwelling flux, was fixed at 10\u003csup\u003e15\u003c/sup\u003e m\u003csup\u003e3\u003c/sup\u003e/yr\u003csup\u003e59\u003c/sup\u003e, and [P\u003csup\u003e3+\u003c/sup\u003e]\u003csub\u003edeep\u003c/sub\u003e is the deep ocean P\u003csup\u003e3+\u003c/sup\u003e concentration, calculated by numerical integration (see below).\u003c/p\u003e\u003cp\u003eTo account for dark (non-photochemical) oxidation of P\u003csup\u003e3+\u003c/sup\u003e, we used a half-life (τ) of 600,000 years under Archean conditions, as reported by Herschy et al.\u003csup\u003e7\u003c/sup\u003e. The associated first-order rate constant (k\u003csub\u003eox\u003c/sub\u003e) was calculated as: k\u003csub\u003eox\u003c/sub\u003e = ln(2)/τ. The total dark oxidation sink (P\u003csub\u003edark_ox\u003c/sub\u003e) was then:\u003c/p\u003e\u003cp\u003eP\u003csub\u003edark_ox\u003c/sub\u003e = k\u003csub\u003eox\u003c/sub\u003e × V\u003csub\u003edeep\u003c/sub\u003e × [P\u003csup\u003e3+\u003c/sup\u003e]\u003csub\u003edeep\u003c/sub\u003e\u003c/p\u003e\u003cp\u003ewhere V\u003csub\u003edeep\u003c/sub\u003e, the volume of the deep ocean\u003csup\u003e\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e\u003c/sup\u003e, was set to 10\u003csup\u003e18\u003c/sup\u003e m\u003csup\u003e3\u003c/sup\u003e.\u003c/p\u003e\u003cp\u003eThe overall mass balance for the deep ocean P\u003csup\u003e3+\u003c/sup\u003e reservoir, i.e., the rate of change of P\u003csup\u003e3+\u003c/sup\u003e accumulation in deep ocean, can be described by the following ordinary differential equation:\u003c/p\u003e\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:\\frac{dP}{dt}=\\frac{\\left({P}_{hyd}-\\:{P}_{photo}\\:-{P}_{dark\\_ox}\\right)\\:}{{V}_{deep}}$$\u003c/div\u003e\u003c/div\u003e\u003cp\u003eor explicitly:\u003c/p\u003e\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$$\\:\\frac{dP}{dt}=\\frac{\\left(\\left({J}_{volc}*{R}_{PC}*{f}_{wx}*\\frac{{P}^{3+}}{{P}^{5+}}\\right)-\\:\\left({F}_{mix}*{P}_{deep}^{3+}\\right)\\:-\\left({k}_{ox}*{V}_{deep}*{P}_{deep}^{3+}\\right)\\right)\\:}{{V}_{deep}}$$\u003c/div\u003e\u003c/div\u003e\u003cp\u003eThis differential equation was numerically solved using the \u003cem\u003eodeint\u003c/em\u003e solver in Python. The model was run until steady state was reached, and the resulting equilibrium concentration of [P\u003csup\u003e3+\u003c/sup\u003e]\u003csub\u003edeep\u003c/sub\u003e was recorded and plotted. The code developed to solve this equation is given in the Supplementary material.\u003c/p\u003e\u003cp\u003eTo quantify steady-state P\u003csup\u003e3+\u003c/sup\u003e concentrations, we modeled a hydrothermally fed soda lake under closed-basin conditions, where hydrologic inputs are fully balanced by evaporation. In such systems, dissolved species approach equilibrium when removal by oxidative sinks (e.g., photolysis, hydrolysis, or precipitation) offsets influx. The steady-state concentration C of a solute can be expressed by:\u003c/p\u003e\u003cdiv id=\"Equc\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equc\" name=\"EquationSource\"\u003e\n$$\\:{C}_{i}=\\:\\frac{{F}_{i}*{L}_{i}}{V}$$\u003c/div\u003e\u003c/div\u003e\u003cp\u003eWhere C\u003csub\u003ei\u003c/sub\u003e is the concentration (mol/L) of a species i, F\u003csub\u003ei\u003c/sub\u003e is the flux (mol/year) of species i entering the lake system, L\u003csub\u003ei\u003c/sub\u003e is the lifetime (year) of species i in the lake environment, and V is volume (litre) of water in the lake.\u003c/p\u003e\u003cp\u003eWe considered the accumulation of P\u003csup\u003e3+\u003c/sup\u003e in the hypothetical lake, exploring lifetime as a free parameter and then highlighting the expected value for anoxic early Earth systems based on available experimental evidence. For values of flux and volume, we considered a hydrothermally active soda lake with similar hydrological properties to Mono Lake in California\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. In other words, the hypothetical lake is a prebiotic analogue of modern Mono lake. For Mono lake, volume of lake V = 3 * 10\u003csup\u003e12\u003c/sup\u003e litre and P\u003csup\u003e5+\u003c/sup\u003e inflow rate F\u003csub\u003eP5+\u003c/sub\u003e is = 1 × 10\u003csup\u003e− 3\u003c/sup\u003e mmol/year\u003csup\u003e4\u003c/sup\u003e. With the observed ratios of P\u003csup\u003e3+\u003c/sup\u003e/P\u003csup\u003e5+\u003c/sup\u003e in the basalt samples, we have considered three phosphite annual inflow rate (F\u003csub\u003eP3+\u003c/sub\u003e) values − 0.001, 0.01 and 0.1 µmol/year. We have considered two endmember cases in terms of the extent of photochemical oxidation in these types of lake. If the lake was exposed to UV-radiation, phosphite oxidation would have been rapid leading to sub-nanomolar or lower concentrations of P\u003csup\u003e3+\u003c/sup\u003e. On the other extreme end, we assumed that photochemistry is not occurring, requiring efficient UV attenuation in the lake surface. This may be accomplished by the accumulation of effective UV-absorbing organics in surficial ‘scum’ layers\u003csup\u003e\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e or by the density segregation of the lake to form basal dark layers\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e.\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\u0026lt; UKRI) Frontiers grant and a Leverhulme Trust research grant (RPG-2022-313) to EES (NE/V010824/1) and Marie Skłodowska-Curie Actions grant to ASB (EP/Y026497/1). CRW acknowledges funding from the NOMIS Foundation in the form of an ETH-NOMIS Fellowship.\u0026nbsp;The complete data for this study is available through\u0026nbsp;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.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAuthor Contributions\u003c/p\u003e\n\u003cp\u003eThe idea is conceived by EES and ASB; ASB, KS, PS, SA, MV, EN, SM and EES provided samples; ASB and JK analyzed the samples; EES and CRW did the modelling; ASB, SM, EES, and CRW led the data interpretation. ASB prepared the first draft of the manuscript with contribution from CRW and EES. The manuscript was reviewed and edited by all authors.\u003c/p\u003e\n\u003cp\u003eCompeting Interest Statement\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eData and materials availability\u003c/p\u003e\n\u003cp\u003eAll data including the Code developed for modelling are available in the main text or in the supplementary materials. Phosphorus speciation data can also be accessed from British Geological Survey at https://doi.org/10.5285/18ee8cec-f141-4544-b210-aa3a4f0a557b.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAnders E, Ebihara M (1982) Solar-system abundances of the elements. Geochim Cosmochim Acta 46:2363\u0026ndash;2380\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTyrrell T (1999) The relative influences of nitrogen and phosphorus on oceanic primary production. Nature 400:525\u0026ndash;531\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePasek MA, Gull M, Herschy B (2017) Phosphorylation on the early earth. Chem Geol 475:149\u0026ndash;170\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWalton CR, Hao J, Sch\u0026ouml;nb\u0026auml;chler M, Shorttle O (2025) Large closed-basin lakes sustainably supplied phosphate during the origins of life. Sci Adv 11:eadq0027\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGulick A (1955) Phosphorus as a factor in the origin of life. Am Sci 43:479\u0026ndash;489\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchwartz AW (2006) Phosphorus in prebiotic chemistry. Philos Trans R Soc B Biol Sci 361:1743\u0026ndash;1749\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHerschy B et al (2018) Archean phosphorus liberation induced by iron redox geochemistry. Nat Commun 9:1346\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGull M, Omran A, Feng T, Pasek MA (2020) Silicate-, magnesium ion-, and urea-induced prebiotic phosphorylation of uridine via pyrophosphate: revisiting the hot drying water pool scenario. \u003cem\u003eLife\u003c/em\u003e vol. 10\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNicholls JWF et al (2023) On the potential roles of phosphorus in the early evolution of energy metabolism. Front Microbiol 14\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGull M, Feng T, Bracegirdle J, Abbott-Lyon H, Pasek MA (2023) Organophosphorus Compound Formation Through the Oxidation of Reduced Oxidation State Phosphorus Compounds on the Hadean Earth. J Mol Evol 91:60\u0026ndash;75\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBaidya AS et al (2025) Bioavailable phosphite in the surface ocean during the Great Oxidation Event. Nat Commun 16:4825\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePasek MA, Harnmeijer JP, Buick R, Gull M, Atlas Z (2013) Evidence for reactive reduced phosphorus species in the early Archean ocean. \u003cem\u003eProc. Natl. Acad. Sci.\u003c/em\u003e 110, 10089\u0026ndash;10094\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePasek MA (2008) Rethinking early Earth phosphorus geochemistry. \u003cem\u003eProc. Natl. Acad. Sci.\u003c/em\u003e 105, 853\u0026ndash;858\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBritvin SN, Murashko MN, Vapnik Y, Polekhovsky YS, Krivovichev SV (2015) Earth\u0026rsquo;s Phosphides in Levant and insights into the source of Archean prebiotic phosphorus. Sci Rep 5:8355\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBaidya AS, Gehringer MM, Savaniu C, Heubeck C, St\u0026uuml;eken EE (2025) Magmatic and thermally produced reactive phosphorus 3.2 billion years ago and its implications for early life. \u003cem\u003eCommun. Earth Environ.\u003c/em\u003e Accepted\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHess BL, Piazolo S, Harvey J (2021) Lightning strikes as a major facilitator of prebiotic phosphorus reduction on early Earth. Nat Commun 12:1535\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePasek MA, Kee TP, Bryant DE, Pavlov AA, Lunine (2008) J. I. Production of Potentially Prebiotic Condensed Phosphates by Phosphorus Redox Chemistry. Angew Chemie Int Ed 47:7918\u0026ndash;7920\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePasek MA, Lauretta DS (2005) Aqueous corrosion of phosphide minerals from iron meteorites: A highly reactive source of prebiotic phosphorus on the surface of the early Earth. Astrobiology 5:515\u0026ndash;535\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBryant DE, Kee TP (2006) Direct evidence for the availability of reactive, water soluble phosphorus on the early Earth. H-Phosphinic acid from the Nantan meteorite. Chem Commun 2344\u0026ndash;2346. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1039/B602651F\u003c/span\u003e\u003cspan address=\"10.1039/B602651F\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYamagata Y, Watanabe H, Saitoh M, Namba T (1991) Volcanic production of polyphosphates and its relevance to prebiotic evolution. Nature 352:516\u0026ndash;519\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBaidya AS, Pasek MA, St\u0026uuml;eken EE (2024) Moderate and high-temperature metamorphic conditions produced diverse phosphorous species for the origin of life. Commun Earth Environ 5:1\u0026ndash;12\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKeefe AD, Miller SL (1995) Are polyphosphates or phosphate esters prebiotic reagents? J Mol Evol 41:693\u0026ndash;702\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBekker T et al (2021) Experimental and Ab Initio Investigation of the Formation of Phosphoran Olivine. ACS Earth Sp Chem 5:1373\u0026ndash;1383\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWalton CR et al (2021) Phosphorus mineral evolution and prebiotic chemistry: From minerals to microbes. Earth Sci Rev 221:103806\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBaidya AS, St\u0026uuml;eken EE (2024) On-line chloride removal from ion chromatography for trace-level analyses of phosphite and other anions by coupled ion chromatography\u0026ndash;inductively coupled plasma mass spectrometry. Rapid Commun Mass Spectrom 38:e9665\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCox GM, Lyons TW, Mitchell RN, Hasterok D, Gard M (2018) Linking the rise of atmospheric oxygen to growth in the continental phosphorus inventory. Earth Planet Sci Lett 489:28\u0026ndash;36\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHorton F (2015) Did phosphorus derived from the weathering of large igneous provinces fertilize the Neoproterozoic ocean? Geochem Geophys Geosyst 16:1723\u0026ndash;1738\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eArndt N, Barnes S, Lesher C (2008) Komatiite. Cambridge University Press\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMole DR et al (2014) Archean komatiite volcanism controlled by the evolution of early continents. \u003cem\u003eProc. Natl. Acad. Sci.\u003c/em\u003e 111, 10083\u0026ndash;10088\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHerzberg C et al (2007) Temperatures in ambient mantle and plumes: Constraints from basalts, picrites, and komatiites. Geochem Geophys Geosyst 8\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNisbet EG et al (1987) Uniquely fresh 2.7 Ga komatiites from the Belingwe greenstone belt. Zimbabwe Geology 15:1147\u0026ndash;1150\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAbbatiello J, Henson JE, Pasek M (2024) Phosphorus availability from olivine for biospheres. Front Astron Sp Sci 11\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHolm NG (2014) Glasses as sources of condensed phosphates on the early earth. Geochem Trans 15:8\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGreber ND et al (2017) Titanium isotopic evidence for felsic crust and plate tectonics 3.5 billion years ago. Sci (80-) 357:1271\u0026ndash;1274\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSyverson DD et al (2021) Nutrient supply to planetary biospheres from anoxic weathering of mafic oceanic crust. \u003cem\u003eGeophys. Res. Lett.\u003c/em\u003e 48, eGL094442 (2021)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRitson DJ, Mojzsis SJ, Sutherland JD (2020) Supply of phosphate to early Earth by photogeochemistry after meteoritic weathering. Nat Geosci 13:344\u0026ndash;348\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRanjan S et al (2021) UV Transmission in Natural Waters on Prebiotic Earth. Astrobiology 22:242\u0026ndash;262\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNisbet EG, Cann JR, Lee C, Dover V (1995) Origins of photosynthesis. Nature 373:479\u0026ndash;480\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWalton CR, Shorttle O (2021) Scum of the Earth: A Hypothesis for Prebiotic Multi-Compartmentalised Environments. \u003cem\u003eLife\u003c/em\u003e vol. 11\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eClark BC et al (2021) Origin of Life on Mars: Suitability and Opportunities. \u003cem\u003eLife\u003c/em\u003e vol. 11\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eParkinson CD, Liang M-C, Yung YL, Kirschivnk JL (2008) Habitability of Enceladus: Planetary Conditions for Life. Orig Life Evol Biosph 38:355\u0026ndash;369\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSekine Y et al (2015) High-temperature water\u0026ndash;rock interactions and hydrothermal environments in the chondrite-like core of Enceladus. Nat Commun 6:8604\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKuskov OL, Kronrod VA (2005) Internal structure of Europa and Callisto. Icarus 177:550\u0026ndash;569\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHsu H-W et al (2015) Ongoing hydrothermal activities within Enceladus. Nature 519:207\u0026ndash;210\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMelwani Daswani M, Vance SD, Mayne MJ, Glein CR (2021) A Metamorphic Origin for Europa\u0026rsquo;s Ocean. \u003cem\u003eGeophys. Res. Lett.\u003c/em\u003e 48, e2021GL094143\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePostberg F et al (2023) Detection of phosphates originating from Enceladus\u0026rsquo;s ocean. Nature 618:489\u0026ndash;493\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMartin W, Baross J, Kelley D, Russell MJ (2008) Hydrothermal vents and the origin of life. Nat Rev Microbiol 6:805\u0026ndash;814\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBarge LM et al (2014) Pyrophosphate synthesis in iron mineral films and membranes simulating prebiotic submarine hydrothermal precipitates. Geochim Cosmochim Acta 128:1\u0026ndash;12\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBrady MP, Tostevin R, Tosca NJ (2022) Marine phosphate availability and the chemical origins of life on Earth. Nat Commun 13:5162\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIngalls M, Grotzinger JP, Present T, Rasmussen B, Fischer WW (2022) Carbonate-associated phosphate (CAP) indicates elevated phosphate availability in Neoarchean shallow marine environments. \u003cem\u003eGeophys. Res. Lett.\u003c/em\u003e 49, eGL098100 (2022)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRasmussen B, Muhling JR, Tosca NJ (2024) Nanoparticulate apatite and greenalite in oldest, well-preserved hydrothermal vent precipitates. Sci Adv 10:eadj4789\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJones C, Nomosatryo S, Crowe SA, Bjerrum CJ, Canfield DE (2015) Iron oxides, divalent cations, silica, and the early earth phosphorus crisis. Geology 43:135\u0026ndash;138\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRego ES et al (2023) Low-phosphorus concentrations and important ferric hydroxide scavenging in Archean seawater. PNAS Nexus 2:pgad025\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eReinhard CT et al (2017) Evolution of the global phosphorus cycle. Nature 541:386\u0026ndash;389\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBoden JS, Zhong J, Anderson RE, St\u0026uuml;eken EE (2024) Timing the evolution of phosphorus-cycling enzymes through geological time using phylogenomics. Nat Commun 15:3703\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRichter FM (1985) Models for the Archean thermal regime. Earth Planet Sci Lett 73:350\u0026ndash;360\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHerzberg C, Condie K, Korenaga J (2010) Thermal history of the Earth and its petrological expression. Earth Planet Sci Lett 292:79\u0026ndash;88\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKorenaga J, Planavsky NJ, Evans DA (2017) D. Global water cycle and the coevolution of the Earth\u0026rsquo;s interior and surface environment. Philos Trans R Soc Math Phys Eng Sci 375:20150393\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWalker JCG (1990) Numerical adventures with geochemical cycles. Oxford University Press\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHenderson P, Henderson GM (2009) The Cambridge handbook of earth science data (Vol. 277). Cambridge University Press\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"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-7915382/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7915382/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eReduced and polymerized phosphorus species such as phosphite and pyrophosphate may have been crucial prebiotic substrates due to their higher reactivity and greater solubility, yet their sources remain debated and fluxes poorly constrained. Here, we show that mafic\u0026ndash;ultramafic rocks on the early Earth could serve as a geologically sustainable source of reactive phosphorus via seafloor weathering. Analysis of mafic-ultramafic rocks from 15 locations reveals phosphite accounting for up to 7%, 24%, 17%, and 0.6% of total extracted phosphorus in olivine separates, peridotite, komatiite, and basalt, respectively, while pyrophosphate reached up to 5% and 0.4% in komatiite and basalt. Using a box model, we show that phosphite could have reached 1 \u0026micro;M in the deep ocean and 67 \u0026micro;M in lakes under low ultra-violet conditions on the prebiotic Earth. We conclude that mafic-ultramafic rocks on the early Earth and possibly other planetary bodies could be an important source of reactive phosphorus for the origin and early evolution of life.\u003c/p\u003e","manuscriptTitle":"Mafic-ultramafic igneous rocks as a source of reactive phosphorus for the origin of life","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-08 06:59:19","doi":"10.21203/rs.3.rs-7915382/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-communications","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"NCOMMS","sideBox":"Learn more about [Nature Communications](http://www.nature.com/ncomms/)","snPcode":"","submissionUrl":"https://mts-ncomms.nature.com/","title":"Nature Communications","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Communications","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"dc57fece-5dd6-48a0-8ebe-44cce0ceb1a6","owner":[],"postedDate":"January 8th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":59978121,"name":"Earth and environmental sciences/Solid Earth sciences/Geochemistry"},{"id":59978122,"name":"Earth and environmental sciences/Solid Earth sciences/Mineralogy"},{"id":59978123,"name":"Earth and environmental sciences/Solid Earth sciences/Petrology"},{"id":59978124,"name":"Earth and environmental sciences/Planetary science/Astrobiology"},{"id":59978125,"name":"Earth and environmental sciences/Planetary science/Geochemistry"}],"tags":[],"updatedAt":"2026-01-08T06:59:19+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-08 06:59:19","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7915382","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7915382","identity":"rs-7915382","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}