Zircon behavior in the partially melted planetary mantle

Zircon behavior in the partially melted planetary mantle | 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 Zircon behavior in the partially melted planetary mantle Alisa Yakimenko, Anastassia Borisova, Yana Fedortchouk, Lydia Fairhurst This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9168576/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 5 You are reading this latest preprint version Abstract Zircon (Zr,Hf)SiO 4 , a common mineral in felsic rocks, preserves invaluable information about the parental magmas due to its exceptional stability. Findings of cm-size zircon crystals in (ultra)mafic rocks are at odds with the experimentally derived high dissolution rates and saturation at low pressures (< 1 GPa) in low-silica melts. To explore the zircon stability in the mantle, we established the saturation and the kinetics of zircon dissolution in basaltic melt at 0.5-2 GPa and discovered zircon stabilization at 1–2 GPa. Our discovery of zircon stabilization with pressure and slower Zr diffusion as a network-former in major element contents (wt% ZrO 2 ) compared to the network modifier in trace contents (ppm Zr) provides unique physical chemical conditions for zircon survival and the dissolution-recrystallization in the crust-mantle system. Physical sciences/Materials science Earth and environmental sciences/Solid earth sciences Figures Figure 1 Figure 2 Figure 3 Introduction Zircon (Zr,Hf)SiO 4 is an orthosilicate and one of the most versatile geological tracers and planetary geochronometers 1 . Incorporation of rare and minor elements such as U, Th, Ti, Hf, and rare earth elements (REE) makes zircon a geochemical clue for rock dating (e.g., 2 ), thermo-barometry, and oxygen barometry 3–5 . Zircon is unique for its robustness due to its hardness and refractory properties. Furthermore, diffusion rates for many elements within zircon are extremely low 6 , allowing this mineral to retain the isotopic information even when exposed to high magmatic temperatures. These properties make it well-suited for reconstructing geological sources, the composition of the melts, physical chemical conditions, and the chronology of geological processes. Zircon crystals can grow from a melt or a fluid phase at a wide range of physical-chemical conditions in different geodynamic or tectono-magmatic environments. Zircon is a ubiquitous accessory mineral in silica-rich crustal rocks, whose geochemical indicators are widely used as markers of crustal growth, evolution, and processes in continental crust 7–9 . In addition, numerous findings of zircon in mafic and ultramafic rocks (e.g., gabbros, dunites, and chromitites) 10–16 suggest that zircon can grow and survive in the mantle-derived melts and can be used as a geochemical tracer of mantle processes. However, the mechanism of zircon growth and survival in mantle magmas remains unknown and requires knowledge of zircon saturation and Zr diffusion coefficients in mafic melts at high pressures. The limited data on the diffusion of Zr in synthetic melts 17–22 and in natural tholeiitic basaltic and haplobasaltic melts 23 vary over 5 orders of magnitude. Furthermore, there is no data on the effect of high Zr contents close to the zircon saturation and the effect of high pressure corresponding to mantle conditions. Previous experimental studies demonstrated that zircon saturation strongly depends on temperature and melt composition 24,25 . Zircon dissolution was first examined in felsic and intermediate melts with varying water contents at pressures and temperatures associated with granitic magmatism in the Earth's crust 24 . This study was expanded in 25 by conducting zircon dissolution experiments in melts ranging from rhyolite to basalt at 930–1225ºC and building a model of zircon saturation in these melts. Both studies showed that Zr contents at zircon saturation increase strongly with decreasing silica and increasing alkali content of the melt and with temperature increase. The alkali and silica contents of the melt impose a major control on Zr contents at zircon saturation 24–26 . The model by Boehnke et al. 25 extrapolated for basaltic melts produces unrealistically high Zr concentration (5000 ppm) required for the crystallization of zircon in basaltic liquids at temperatures above 900°C. DeLong and Chatelain 27 found that Zr concentrations in water-saturated MORB gabbro are seven times greater than in a felsic melt. They assumed that zircon begins crystallizing at 840°C due to the fractionation of modal phases. There are only a few experimental studies of zircon saturation in mafic and ultramafic systems 21,23,28,29 . Experimental data on zircon dissolution in anhydrous natural mid-ocean ridge basalt (MORB) by Borisova et al. 23 showed that typical 100 µm zircon crystals dissolve rapidly (~ 10 h) upon reaction with basaltic melt at pressures of 0.2–0.7 GPa if controlled by Zr diffusion. These findings raise questions about the origin and stability of zircon in the mantle and its survival in mafic magmas. However, these studies cover a very limited pressure range up to 0.7 GPa. The effect of pressure on zircon saturation in the mantle melts remains largely unknown above 0.7 GPa. Zhang and Xu 22 reported a decrease in zircon saturation from 1.26 to 1.10 wt% ZrO 2 with an increase in pressure from 0.5 to 1.5 GPa for rhyolitic melts. However, Boehnke et al. 25 found no significant pressure effect on zircon saturation at pressures less than 2.5 GPa. The model of Borisov and Aranovich 29 , developed for zircon saturation in mafic melts over a pressure range of 0.1 MPa to 2.5 GPa and a temperature range of 750–1500°C, suggests that zircon crystallization in mafic melts is unlikely. However, the model is primarily based on experiments conducted at 1 atm (0.0001 GPa), and extrapolation to pressures as high as 2.5 GPa may introduce significant uncertainties. Crisp and Berry 30,31 developed a zircon solubility model for their experimental data on granitic to andesitic compositions at pressure from 0.0001 to 4.0 GPa and temperatures between 800 and 1500°C. However, their study did not address zircon solubility in mafic melts. Thus, the goal of our study is to examine the effect of pressure on zircon saturation and Zr diffusivity in basaltic melt using zircon dissolution experiments at 0.5, 1, and 2 GPa. The new data on Zr geochemistry at mantle conditions help to better understand the kinetics of zircon growth in the mantle and the Zr geochemical cycle during the subduction of basaltic crust into the mantle. Results Saturation of mantle-derived melt with zircon Our experiments investigated the effect of pressure between 0.5 and 2 GPa, over a temperature range of 1350 to 1550 °C, on zircon dissolution. Table 1 summarize the experimental conditions and the results of eight experimental runs reporting zircon saturation concentrations and Zr diffusion rates in basaltic melts. Zircon shows congruent dissolution in all runs (Fig. 1), and the diffusive boundary layer melt is produced between zircon and the mid-ocean ridge basalt (MORB) melt. All runs except PC321 are super-liquidus and produced only glass in association with the partially dissolved zircon. The PC321 run (1400ºC and 2 GPa) developed euhedral crystals 10 to 50 microns in size along the zircon-glass interface with the composition similar to augite ((Ca 0.65 ,Na 0.09 )(Mg 0.84 ,Fe 0.19 ,Al 0.17 )(Si 1.83 ,Al 0.22 )O 6 ) (Fig. S4) (Table 1). During diffusion-controlled dissolution, zircon saturation is reached in the melt at the zircon-melt interface. For this reason, we used the Zr content in the glass at the zircon-glass interface to obtain Zr concentration at the zircon saturation (C sat ). This concentration ranges in our experiments from 2.03 wt% ZrO 2 (at 2 GPa, 1400⁰C) to 7.73 wt% ZrO 2 (at 2 GPa, 1500⁰C) (Table 1). It positively correlates with temperature (Fig. 2A). We observed an increase in the zircon stability with pressure in the investigated pressure range. At 2 GPa, zircon saturation increases markedly at 1500 °C - 1550 °C (Table 1). However, zircon saturation reaches 6.18 wt% ZrO 2 at 1500°C, compared to 5.33 wt% ZrO 2 at 1550 °C (Fig. 2A). Table 1. Experimental conditions and results for zircon dissolution experiments in basalt (MORB). Zrn- zircon, Zircon C sat – Zr concentration at zircon saturation, D Zr – Zr diffusion rate. Run# H 2 O, wt% T, o C P, GPa Duration, min Phases Zircon C sat , ZrO 2 wt% D Zr , cm 2 /s PC343 0.0 1550 ± 20 2 15 Glass, Zrn 5.33 ± 0.02 2.03E-07 PC341 0.0 1500 ± 20 2 15 Glass, Zrn 6.18 ± 0.03 1.61E-07 PC333 0.0 1450 ± 20 2 15 Glass, Zrn 2.45 ± 0.01 8.30E-08 PC321 5.0 1400 ± 20 2 60 Glass, Zrn, augite 2.03 ± 0.01 3.00E-08 PC328 0.0 1450 ± 20 1 120 Glass, Zrn 4.37 ± 0.01 2.03E-08 PC325 0.0 1400 ± 20 1 90 Glass, Zrn 3.75 ± 0.01 1.54E-08 PC314 0.0 1350 ± 20 1 60 Glass, Zrn 2.12 ± 0.01 6.01E-09 PC332 0.0 1400 ± 20 0.5 15 Glass, Zrn 5.36 ± 0.01 8.26E-08 Borisova et al., 2020 0.0 1300 0.5 300 Glass, Zrn 2.82± 0.05 2.87E-08 Our experiments demonstrate significantly lower Zr concentration at zircon saturation in basaltic melts than previous experiments 25 . For example, we obtained a zircon saturation of 2.1 wt% ZrO 2 at 1350°C and 1 GPa, which is less than half of the 4.5 wt% ZrO 2 reported by 25 at 1225°C and 1 GPa. This effect can be explained by 1.5 times higher alkali content used in 25 , Indeed, it has been shown that as the (Na 2 O + K 2 O)/Al 2 O 3 rises from 1 to 2, Zr concentration increases from 1 to 4 wt% at 800 °C in felsic melts 24,26 . This suggests that zircon can be more stable in low-alkali mafic mantle-derived melts than previously expected. When the latest model of Crisp and Berry 30,31 is applied to our experimental data, the predicted zircon saturation is two to three times higher than the saturation observed in our experiments (Fig. S5). This discrepancy may reflect differences in experimental methodology, as Crisp and Berry grew zircon crystals from melts oversaturated in Zr (15%) during experiments lasting 48 and 72 hours. In addition, their model was developed primarily for granitic and andesitic compositions, and experiments conducted at pressures above 1 GPa represent less than 10% of their dataset. As a result, the model may not adequately capture the effects of elevated pressure and mafic compositions on zircon saturation. Discussion Previous experimental studies of zircon dissolution have demonstrated that the Zr diffusion coefficient primarily depends on temperature, melt composition, and water content, while being less affected by pressure 23,32 . Higher temperatures and lower silica content in the melt increase the Zr diffusion and, therefore, zircon dissolution rate. Our diffusion data (Table 1 ) show the fastest diffusion (D Zr ) in basaltic melt at 1550°C (Fig. S6). Our obtained values of Zr diffusion coefficients in basalts are close to those in the same melt estimated by Borisova et al. 23 and lower than Zr diffusion coefficients derived by Holycross and Watson 21 (Fig. S6). Our experiments reveal a significant pressure control on the D Zr in the studied range of 0.5 to 2 GPa. Furthermore, they indicate that Zr diffusion varies non-linearly with pressure, where the lowest D Zr occurs at 1 GPa, while at 0.5 GPa and 2 GPa Zr diffusion is faster (Fig. S6 and Table 1 ). For example, at 1450°C, D Zr at 1 GPa is four times lower than at 2 GPa. The D Zr are nearly the same for 0.5 GPa at 1400°C and 2 GPa at 1450°C. At the same temperature of 1400°C, D Zr at 0.5 GPa is almost 3 times higher than at 2 GPa. This suggests that increased pressure slows down the diffusion of Zr. The maximum Zr diffusivity D Zr = 2.03·10 − 7 cm 2 /s was observed at the highest temperature studied of 1550⁰C and 2 GPa. We compared our data to previous studies by calculating Zr diffusion coefficients using the equation from Zhang and Xu 22 . Fig. S7 shows that our experimentally derived Zr diffusivity in basaltic melt aligns with the diffusion coefficients calculated using Zhang's model within 18% relative error. However, because this model was developed for experiments below 1 GPa, it cannot fully account for the pressure effect observed in our experiments at 2 GPa. To investigate the dependence of the Zr diffusion coefficient from temperature, we applied the Arrhenius equation for MORB at 1 GPa and 2 GPa: \(\:D={D}_{0}\bullet\:{e}^{\frac{-{E}_{a}}{RT}},\) (Eq. 1 ), where \(\:D\:\text{\--}\) diffusion coefficient, \(\:{D}_{0\:}\text{\--}\) pre-exponential factor (constant in cm 2 s − 1 ), \(\:{E}_{a}\) ​ \(\:\:\text{\--}\) activation energy (J/mol), \(\:R\:\text{\--}\) gas constant (J/(mol·K)), \(\:T\:\text{\--}\) temperature (K). We obtained Arrhenius relationship for D Zr at 1350, 1400, and 1450ºC at 1 GPa and 1450, 1500, and 1550ºC at 2 GPa. Zr diffusivities were fit using a linear regression to find the slope and activation energy of the Arrhenius equation for Zr diffusion rate (Fig. 2 B). Standard error (σ) estimation for diffusion coefficients was acquired from least-squares fits of the experimental data at a given temperature. The slope in Fig. 2 B is proportional to E a , which is estimated to be 283.82 ± 19.13 kJ/mol with D 0 of 8.98 cm²/s at 1 GPa. This activation energy differs from the previous estimate 219.73 ± 17.80 kJ/ mol and D 0 of 1.41 cm²/s for Zr as a trace element in basalts 21 , because, in our study, Zr becomes a major element within the boundary layer (Fig. 3 ). At 2 GPa, we estimated the activation energy to be 234.38 ± 13.75 kJ/mol, and D 0 is 1.13 cm²/s. The E a = 283.82 ± 19.13 kJ/mol for Zr diffusion at 1 GPa obtained in our study for MORB with non-bridging oxygens to tetrahedral cations (NBO/T) of 0.83 is even higher than the activation energies for self-diffusion of network formers, such as Si at 227 ± 13 kJ/mol (1 GPa) and O at 215 ± 13 kJ/mol (1 GPa) 33 . In fact, diffusion becomes faster at higher pressures for tightly packed aluminosilicate melts such as basalt 34 . The effect of pressure is likely due to the structural compaction within the melt, which reduces energy barriers for atomic motion 35 . It suggests that at concentrations close to zircon saturation, Zr in the boundary layer behaves as a network former. This effect slows down Zr diffusion and suppresses dissolution of zircon compared to the diffusion of trace amounts of Zr, studied by Holycross and Watson at 1 GPa (Fig. 2 B). Importantly, the higher Zr diffusion at 2 GPa compared to that at 1 GPa can be explained by the lower viscosity of the aluminosilicate melts at high pressure 34 and by the similar behavior of Zr to the network-forming Si and O ions in the melts. This fact is directly related to high Zr concentration in the diffusive boundary layer melt produced due to zircon dissolution. High Zr in the aluminosilicate melts is a trigger for the combination of ZrO 6 with SiO 4 to polyhedron ZrO 6 SiO 4 and the related network connectivity 36,37 . To determine how long zircon survives in basaltic melt, we applied Harrison and Watson's model 32 . The time required for zircon crystals of a given radius to dissolve is a function of temperature at 1 and 2 GPa pressures. Figure 3 B shows that our results follow the same trend as Harrison and Watson's data for anhydrous felsic melts. This similarity is due to our use of the same experimental approach of diffusion-controlled dissolution. In this approach, Zr diffusion and zircon saturation are measured within the interface melt saturated in zircon and confined by a boundary layer. Under these conditions, zirconium (Zr) is a major element in the melt structure where Zr is the network-former cation. Implications for zircon stability and Zr geochemistry in the mantle The results of our experiments indicate that zircon in mid-ocean ridge basalt undergoes only congruent dissolution at pressures between 0.5-2 GPa and temperatures of 1350–1550°C. Zircon is more stable than previously predicted by earlier models 29,30 . Zircon saturation decreases as pressure increases to 2 GPa, indicating the higher stability of zircon at depths of up to 30–60 km. At 1–2 GPa, the Zr diffusivity in the boundary layer melts as a major element (> 1 wt%) becomes slower compared to the diffusivity of Zr in trace concentrations (ppm), decreasing zircon dissolution/crystallization rates in the deep upper mantle melt, which is likely related to the structural role of Zr as a network former ion. Considering slow Zr diffusion in this boundary layer melt to be the rate limiting process for the zircon dissolution/crystallization, the optimal conditions for preserving zircon in basaltic melt occur at temperatures between 1400 and 1500ºC at a pressure of 1–2 GPa. This physical-chemical stabilization allows zircon to survive and/or recrystallize in the basaltic or hybrid melt at depths of up to 30–60 km and to remain preserved until the uplift, during slab-mantle interactions, as well as crust-mantle interactions such as delamination and rejuvenation (see Fig. 3 in 38 ). Materials and Methods Experimental methods Experiments were conducted using a piston-cylinder apparatus at the Experimental Petrology lab, Department of Earth and Environmental Sciences, Dalhousie University (Halifax, Nova Scotia). A double-polished disk of natural zircon was placed at the bottom of a noble metal capsule and filled with natural mid-ocean ridge basalt (MORB). Au 80 Pd 20 alloy capsules and pure Pt capsules, each with a 3 mm outer diameter, were used as sample containers at temperatures of 1300–1350°C and 1350–1450°C, respectively. Runs conducted in Pt capsules experienced an iron loss of about 5 wt% FeO (total), which didn’t affect the overall structure of the melt. We used zircon chips from the ~ 730 Ma Mud Tank carbonatite (Australia) 39 , known for their low trace element content, making them ideal for dissolution experiments 23,32 . The zircon slides were polished on both sides to a thickness of 1.15 to 1.65 mm. After polishing, the disks were cut to a diameter of 2.25 mm and ultrasonically cleaned in ethanol for 5 minutes. The disks were examined under a stereomicroscope to select the cleanest, most transparent, and with minimal cracks or inclusions, and to check the quality of the polishing. The mid-ocean ridge basalt (MORB) glass used in our experiments is a typical moderately differentiated (8.2 wt% of MgO, Table S1 ) glassy tholeiitic basalt (number 3786/3) from Knipovich ridge of the Mid-Atlantic Ridge 23,40 . The MORB glass has been crushed to a powder (< 100 µm glass size). The starting material was loaded directly into the noble metal capsule, and oxygen fugacity ( f O 2 ) was not controlled using an additional buffer. We assumed f O 2 to be buffered by the enclosing NaCl-Pyrex assembly, approximating near NNO conditions (average NNO = 0.1, following 41 ). The loaded capsules were subsequently welded shut and dried in an oven at 100°C for 12 hours. In one experiment, water was added with a microsyringe. The capsules were loaded into a 1/2 inch assembly, which included a NaCl cell, Pyrex glass, graphite furnace, and crushable MgO inserts (Fig. S1 ). The accuracy of pressure calibrated using diopside melting at 1 GPa and 1530°C 42 was better than 5%, and no pressure correction was applied. The temperatures were monitored with a Eurotherm controller using W 95 Re 5 –W 74 Re 26 thermocouple without any correction for pressure on emf. Thermal gradients within the capsule were ± 15°C at 1300°C, established by the spinel thermometer 43 . The thermocouple was housed in an alumina sleeve and positioned at the top of the sample capsule, separated by an Al 2 O 3 disc (0.5 mm thickness), ensuring accurate temperature measurement without direct contact between the thermocouple and the capsule. The experiments were conducted at pressures ranging from 0.5 to 3 GPa and temperatures from 1300 to 1450°C, with durations varying from 15 minutes to 5 hours. Shorter 15-minute runs were used for determining Zr diffusion in the boundary melt, whereas the extended runs > 2 hours were effective in determining zircon saturation. Initially, each sample was pressurized to approximately 3 MPa, heated to 600°C at a rate of 50°C/min, and held at that temperature for 6 minutes while the pressure increased to the desired value. The temperature was then ramped up to the final temperature at a rate of 50°C/min (for longer runs) or 100°C/min (for 15-minute runs) and pressure adjusted to the final value (T systematic error = -5°C). If the pressure deviated by more than 10% during the run, it was adjusted back to the run value. The quenching was achieved by cutting power to the graphite furnace, which brought the sample to room temperature within a few seconds. To prevent cracking, runs at 2 GPa and 3 GPa were slowly decompressed. The pressure on the piston was decreased by 2.1–2.8 MPa every 5 minutes until it reached 5.5–6.0 MPa. After each experiment, the capsules were sliced in half with a diamond saw, mounted in epoxy, and polished using diamond paste to expose the zircon-melt boundary. The polished sections were observed under an optical microscope and a scanning electron microscope (SEM) before analyses with electron probe microanalysis (EPMA). Analytical techniques The experimental products were initially analyzed under a petrographic microscope to identify dissolution textures. Identification of baddeleyite ZrO 2 and other phases, as well as initial measurement of Zr concentrations in the glass adjacent to the zircon crystal, were performed on carbon-coated samples (~ 20 nm) using energy dispersive spectroscopy (EDS) and backscattered electron (BSE) imaging on a Tescan Mira3 Field-Emission Scanning Electron Microscope (FE-SEM) at Saint Mary’s University, Halifax, Canada. Operating conditions included a 20 kV accelerating voltage, 5 nm beam size, and a beam current of 260 pA. We employed electron microprobe analysis (EMPA) to determine the Zr concentration and to obtain its profile in the reaction zones. Major and minor element content (including Zr) in crystals and glasses was determined using wavelength-dispersive spectrometry (WDS) on a CAMECA SX-Five microprobe at Centre Castaing, Toulouse, France. Operating conditions for the electron microprobe were: an accelerating voltage of 15 kV, currents of 100 nA, and a 2 × 2 µm spot beam. The detection limit for Zr was estimated as 70 ppm; this value was derived from the Cameca SX Five software based on the MPI-DING standard glasses. The synthetic reference MPI-DING glasses of mafic and ultramafic composition (AT-HO, St-HS 44 ) obtained from natural rock powders were analyzed as unknown samples to monitor the accuracy of the major and trace element analyses. The standard deviation estimated on the reference glasses ranges from 0.7 to 1 wt%. Compositional profiles were measured in the glass perpendicular to the zircon disc, starting from the interface (Fig. S2 ). The linear interface allowed for corrections of secondary fluorescence effects, ensuring accurate zircon (Zr) concentrations in the interface glasses, using the method described in 23 . The secondary fluorescence effect was calculated using the "numpy.interp" function in Python (version 1.17) 45 . However, this effect contributes less than 1% to each measurement, meaning it is negligible compared to the relative error. Zr diffusion coefficient extraction The extraction of the Zr diffusion coefficient from the profiles of Zr concentration at the zircon-glass interface (Fig. S1 A) was performed using the method from Harrison and Watson 32 . The concentrations of Zr measured in the profiles were converted to the inverse error function (erf⁻¹ (1 – C x /C o )), revealing a linear correlation with the distance from the interface. For each sample, we analyzed two or three parallel compositional profiles perpendicular to the zircon-melt interface to confirm that zircon dissolution is controlled by Zr diffusion in the melt. The identical shape of these parallel profiles allowed us to extract the Zr diffusion coefficient. In addition, a linear correlation of the erc function with the profile distance from the interface was an additional test confirming that the zircon dissolution in our runs was controlled by Zr diffusion without any additional effect of convection. The shape of the profile shown in Fig. S1 suggests that congruent zircon dissolution is primarily controlled by Zr diffusion, according to the criterion established by Harrison and Watson 32 . In this case, the slope (m) of the error function graph (Fig. S3B) is equal to $$\:m\:=\frac{1}{\sqrt{4Dt}}$$ 1 where \(\:D\:\) is the diffusion coefficient (cm 2 /s), \(\:t\:\) is the experiment duration (s), which allows to extract the Zr diffusion coefficient as: $$\:D=\:\frac{1}{4\:{m}^{2}t}$$ 2 The plots for all experimental runs used for Zr diffusion extraction can be found in Supplementary Fig. 1, and the values of the Zr diffusion coefficient are presented in Table 1 . The R-squared values of the trend line (Fig. S1 B) for the Zr diffusion calculations ranged from 0.989 to 0.999, indicating high reliability of this approach. In sample PC321 at 1400ºC and 2 GPa, we observed the formation of isometric crystals from 20 to 40 microns in size, with a chemical composition similar to augite ((Ca,Na)(Mg,Fe,Al)(Si,Al) 2 O 6 ) at the zircon-glass interface. We measured the Zr profile in this sample while avoiding the crystals. Since this phase does not concentrate Zr in its crystal structure (according to EPMA analysis), the Zr content profile appeared sufficient for extracting the diffusion coefficient. The Zr diffusion coefficients are affected by zircon dissolution textures. In samples where only the zircon crystal and homogeneous glass are present, Harrison and Watson's method for the calculation of Zr diffusion coefficients is effective. In sample PC321, a liquidus phase is present alongside glass. We were able to calculate diffusion for this sample because the rare augite crystals formed did not contain Zr, and the crystal growth did not affect the Zr content in glass. Thermodynamic modeling To estimate the silica activity in our experiments, we performed MELTS thermodynamic equilibrium calculations in the basalt system. Calculations were conducted at a temperature range from 1350° to 1550°C and pressures of 0.5 to 2 GPa. Modelling of thermodynamic equilibrium phases was performed using the rhyolite-MELTS (version 1.0.1) and pMELTS (version 5.6.1, published 13 November 2016) software 46 . PERPLE_X modelling (version 7.1.5, published 12 January 2023) was used to calculate the reaction zircon-baddeleiyte on the P-T diagram and to compare it to the experimental data. The database was set to hp633ver.dat 47 . Declarations Acknowledgments: Funding: European Research Council grant [ERC Advanced ADG 101141259 PLANETAFELSIC] (AB) NSERC Discovery grant [RGPIN-2020-06718] and International Alliance Catalyst grant [ALLRP/587298 -2023] (YF) AY thanks Mitacs for Mitacs Globalink Research Award [IT38392] Dalhousie Earth And Environmental Sciences Doctoral (AY) TESS Booster grant (AY) Author contributions: Conceptualization: AB, YF Mixture preparation: AY, LF Experiments: AY, LF Analytical techniques: AY, AB Funding acquisition: AB, YF, AY Supervision: YF, AB Writing – original draft: AY, YF, AB Writing – review & editing: AY, YF, AB Competing interests: Authors declare that they have no competing interests. Data and materials availability: All data are available in the main text or the supplementary materials. References Moser, D. E. et al. Solving the Martian meteorite age conundrum using micro-baddeleyite and launch-generated zircon. 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Lithos 294-295 , 53-72 (2017). https://doi.org/10.1016/j.lithos.2017.09.020 Bychkova, Y. V. et al. Proterozoic Kivakka layered mafic-ultramafic intrusion, Northern Karelia, Russia: Implications for the origin of granophyres of the upper boundary group. Precambrian research 331 , 105381 (2019). https://doi.org/10.1016/j.precamres.2019.105381 Bea, F. et al. Zircon xenocryst evidence for crustal recycling at the Mid-Atlantic Ridge. Lithos 354-355 , 105361 (2020). https://doi.org/10.1016/j.lithos.2019.105361 Nakamura, E. & Kushiro, I. Trace element diffusion in jadeite and diopside melts at high pressures and its geochemical implication. Geochimica et cosmochimica acta 62 , 3151-3160 (1998). https://doi.org/10.1016/S0016-7037(98)00223-3 Mungall, J. E., Dingwell, D. B. & Chaussidon, M. Chemical diffusivities of 18 trace elements in granitoid melts. Geochimica et cosmochimica acta 63 , 2599-2610 (1999). https://doi.org/10.1016/S0016-7037(99)00209-4 Koepke, J. & Behrens, H. Trace element diffusion in andesitic melts: an application of synchrotron X-ray fluorescence analysis. Geochimica et cosmochimica acta 65 , 1481-1498 (2001). https://doi.org/10.1016/S0016-7037(01)00550-6 Baker, D. R., Conte, A., Freda, C. & Ottolini, L. The effect of halogens on Zr diffusion and zircon dissolution in hydrous metaluminous granitic melts. Contributions to mineralogy and petrology 142 , 666-678 (2002). https://doi.org/10.1007/s00410-001-0328-3 Holycross, M. E. & Watson, B. Diffusive fractionation of trace elements in basaltic melt. Contributions to Mineralogy and Petrology 171 , 80 (2016). https://doi.org/10.1007/s00410-016-1289-x Zhang, Y. & Xu, Z. Zircon saturation and Zr diffusion in rhyolitic melts, and zircon growth geospeedometer. The American mineralogist 101 , 1252-1267 (2016). https://doi.org/10.2138/am-2016-5462 Borisova, A. Y. et al. Zircon survival in shallow asthenosphere and deep lithosphere. American Mineralogist 105 , 1662-1671 (2020). https://doi.org/doi:10.2138/am-2020-7402 Watson, E. B. & Harrison, T. M. Zircon saturation revisited: temperature and composition effects in a variety of crustal magma types. Earth and planetary science letters 64 , 295-304 (1983). https://doi.org/10.1016/0012-821X(83)90211-X Boehnke, P., Watson, E. B., Trail, D., Harrison, T. M. & Schmitt, A. K. Zircon saturation re-revisited. Chemical geology 351 , 324-334 (2013). https://doi.org/10.1016/j.chemgeo.2013.05.028 Watson, E. B. Zircon saturation in felsic liquids: Experimental results and applications to trace element geochemistry. Contributions to mineralogy and petrology 70 , 407-419 (1979). https://doi.org/10.1007/BF00371047 DeLong, S. E. & Chatelain, C. Trace-element constraints on accessory-phase saturation in evolved MORB magma. Earth and Planetary Science Letters 101 , 206-215 (1990). https://doi.org/https://doi.org/10.1016/0012-821X(90)90154-P Shao, T., Xia, Y., Ding, X., Cai, Y. & Song, M. Zircon saturation in terrestrial basaltic melts and its geological implications. Solid earth sciences 4 , 27-42 (2019). https://doi.org/10.1016/j.sesci.2018.08.001 Borisov, A. & Aranovich, L. Zircon solubility in silicate melts: New experiments and probability of zircon crystallization in deeply evolved basic melts. Chemical geology 510 , 103-112 (2019). https://doi.org/10.1016/j.chemgeo.2019.02.019 Crisp, L. J. & Berry, A. J. A new model for zircon saturation in silicate melts. Contributions to mineralogy and petrology 177 , 71 (2022). https://doi.org/10.1007/s00410-022-01925-6 Crisp, L. J. & Berry, A. J. Correction to: A new model for zircon saturation in silicate melts. Contributions to mineralogy and petrology 179 , 75 (2024). https://doi.org/10.1007/s00410-024-02145-w Harrison, T. M. & Watson, E. B. Kinetics of zircon dissolution and zirconium diffusion in granitic melts of variable water content. Contributions to mineralogy and petrology 84 , 66-72 (1983). https://doi.org/10.1007/BF01132331 Tinker, D., Lesher, C. E. & Hutcheon, I. D. Self-diffusion of Si and O in diopside-anorthite melt at high pressures. Geochimica et cosmochimica acta 67 , 133-142 (2003). https://doi.org/10.1016/S0016-7037(02)01039-6 Wolf, G. H. & McMillan, P. F. Pressure effects on silicate melt structure and properties. Reviews in Mineralogy and Geochemistry 32 , 505-561 (1995). Kushiro, I., Yoder, H. S. & Mysen, B. O. Viscosities of basalt and andesite melts at high pressures. Journal of Geophysical Research 81 , 6351-6356 (1976). https://doi.org/10.1029/JB081i035p06351 Ficheux, M., Burov, E., Cormier, L., Gouillart, E. & Trcera, N. Influence of zirconium on cation mobilities in Na2O-CaO-Al2O3-SiO2 melts: A multicomponent diffusion and XANES study. Geochimica et cosmochimica acta 270 , 394-408 (2020). https://doi.org/10.1016/j.gca.2019.12.006 Dou, H. et al. Effect of zirconium on the viscosity, structure and crystallization behavior of melts for basalt fiber production. Ceramics international 51 , 19497-19507 (2025). https://doi.org/10.1016/j.ceramint.2025.02.125 Bernadet, J. et al. Making continental crust on water-bearing terrestrial planets. Science Advances 11 , eads6746 (2025). https://doi.org/doi:10.1126/sciadv.ads6746 Gain, S. E. M. et al. Mud Tank Zircon: Long‐Term Evaluation of a Reference Material for U‐Pb Dating, Hf‐Isotope Analysis and Trace Element Analysis. Geostandards and geoanalytical research 43 , 339-354 (2019). https://doi.org/10.1111/ggr.12265 Borisova, A. Y. et al. Hydrated Peridotite – Basaltic Melt Interaction Part I: Planetary Felsic Crust Formation at Shallow Depth. Frontiers in earth science (Lausanne) 9 (2021). https://doi.org/10.3389/feart.2021.640464 Fedortchouk, Y., Canil, D. & Semenets, E. Mechanisms of diamond oxidation and their bearing on the fluid composition in kimberlite magmas. The American mineralogist 92 , 1200-1212 (2007). https://doi.org/10.2138/am.2007.2416 Williams, D. W. & Kennedy, G. C. Melting curve of diopside to 50 kilobars. Journal of Geophysical Research 74 , 4359-4366 (1969). https://doi.org/10.1029/JB074i017p04359 Watson, E., Wark, D., Price, J. & Van Orman, J. Mapping the thermal structure of solid-media pressure assemblies. Contributions to mineralogy and petrology 142 , 640-652 (2002). https://doi.org/10.1007/s00410-001-0327-4 Jochum, K. P. et al. MPI-DING reference glasses for in situ microanalysis: New reference values for element concentrations and isotope ratios. Geochemistry, geophysics, geosystems : G3 7 , Q02008-n/a (2006). https://doi.org/10.1029/2005GC001060 Oliphant, T. E. Guide to numpy . Vol. 1 (Trelgol Publishing USA, 2006). Ghiorso, M. S. & Sack, R. O. Chemical mass transfer in magmatic processes IV. A revised and internally consistent thermodynamic model for the interpolation and extrapolation of liquid-solid equilibria in magmatic systems at elevated temperatures and pressures. Contributions to Mineralogy and Petrology 119 , 197-212 (1995). Holland, T. & Powell, R. An internally consistent thermodynamic data set for phases of petrological interest. Journal of metamorphic Geology 16 , 309-343 (1998). Additional Declarations No competing interests reported. Supplementary Files A.YakimenkoScientificReportsNatureSupplementary.pdf A.YakimenkoSupplementaryDataS1.xlsx Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 17 May, 2026 Reviewers invited by journal 15 Apr, 2026 Editor assigned by journal 21 Mar, 2026 Submission checks completed at journal 21 Mar, 2026 First submitted to journal 19 Mar, 2026 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-9168576","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":623523364,"identity":"0848b489-a0f1-4e6c-be51-e5812d0a34c4","order_by":0,"name":"Alisa Yakimenko","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAxklEQVRIiWNgGAWjYDACdobEBwk/aur7GRIYDxCnhZnhscHHnmOMMxsSGIjVwvhMcgYbM+OGA8Rq4W9mTjbm4WFjNj6e/OAAQ40dYS0Sh9kSH/NYyLCZnXlmcIDhWDIR1hzmAdvCY3YjweAAYwMzYR3yh/m/SQPdJWE8I/0DUEs9YS0GhxnSQN43MJDIAdlymLAWw8MMyaBATpA486bgQMKx44S1yB1vAEdlAn97+sYHH2qqCWtBBQmkahgFo2AUjIJRgB0AAAoyPRZ17PtSAAAAAElFTkSuQmCC","orcid":"","institution":"Université de Toulouse, CNRS, IRD","correspondingAuthor":true,"prefix":"","firstName":"Alisa","middleName":"","lastName":"Yakimenko","suffix":""},{"id":623523366,"identity":"3ba812da-c55b-4f49-82ba-904fac735bb6","order_by":1,"name":"Anastassia Borisova","email":"","orcid":"","institution":"Université de Toulouse, CNRS, IRD","correspondingAuthor":false,"prefix":"","firstName":"Anastassia","middleName":"","lastName":"Borisova","suffix":""},{"id":623523367,"identity":"5058f52a-b893-4161-a0f5-faf9539c8544","order_by":2,"name":"Yana Fedortchouk","email":"","orcid":"","institution":"Dalhousie University","correspondingAuthor":false,"prefix":"","firstName":"Yana","middleName":"","lastName":"Fedortchouk","suffix":""},{"id":623523368,"identity":"184c93af-167d-47e1-b579-c4ed59f7a9a3","order_by":3,"name":"Lydia Fairhurst","email":"","orcid":"","institution":"Dalhousie University","correspondingAuthor":false,"prefix":"","firstName":"Lydia","middleName":"","lastName":"Fairhurst","suffix":""}],"badges":[],"createdAt":"2026-03-19 10:53:48","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9168576/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9168576/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":107613747,"identity":"699af22a-cd36-404f-9922-96d4224c9119","added_by":"auto","created_at":"2026-04-23 08:57:28","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":254670,"visible":true,"origin":"","legend":"\u003cp\u003e(A) Backscattered electron (BSE) image of the experimental sample PC333 showing an example of congruent zircon dissolution in basaltic melt and the location of the compositional profile presented on (B) and (C). (B) Zr contents in the melt vs. the distance from the zircon crystal interface in the PC333 run. (C) Error function erf\u003csup\u003e-1\u003c/sup\u003e (1 – C\u003csub\u003ex\u003c/sub\u003e/C\u003csub\u003eo\u003c/sub\u003e ) vs. distance from the zircon crystal interface in the PC333 run.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9168576/v1/865d57d5265cd022f6d47a52.jpeg"},{"id":107613688,"identity":"33a59507-edb9-4393-98a0-66e0bd340a73","added_by":"auto","created_at":"2026-04-23 08:57:15","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":423951,"visible":true,"origin":"","legend":"\u003cp\u003e(A) Zircon saturation concentration at different pressures vs. inverse temperature. Error bars are smaller than the symbol size. (B) Arrhenius-type plot of diffusion coefficients calculated for basaltic melts at 1 GPa and 2 GPa. The similar slopes are evidence that diffusion is the dominant transport process in these experiments. Error bars are shown as the standard deviation of residuals (σ).\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9168576/v1/4de955c5d93523d0581781f8.jpeg"},{"id":107613750,"identity":"af1c599d-b4e2-4622-a553-4574a76cb610","added_by":"auto","created_at":"2026-04-23 08:57:29","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":429543,"visible":true,"origin":"","legend":"\u003cp\u003e(A) Zircon survival in oceanic crust as it descends into the mantle within a subducting slab (zircons not to scale). The dissolution/crystallization of zircon is controlled by the Zr as a major element diffusivity in the boundary layer melt. (B) Time of zircon survival in felsic and mid-ocean basaltic melts as a function of temperature, calculated using the model of Harrison and Watson \u003csup\u003e32\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"floatimage3.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-9168576/v1/bb5a2bdf110f7de4fceb4c82.jpeg"},{"id":107613808,"identity":"590917f0-ac83-40d4-8778-389ffd55b880","added_by":"auto","created_at":"2026-04-23 08:57:40","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1580624,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9168576/v1/997fe05f-4b15-4519-ba2f-9250c380b449.pdf"},{"id":107613695,"identity":"318eee12-4685-4310-a36d-08f048d3db2d","added_by":"auto","created_at":"2026-04-23 08:57:21","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":420714,"visible":true,"origin":"","legend":"","description":"","filename":"A.YakimenkoScientificReportsNatureSupplementary.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9168576/v1/b43f5023ecd5b906003e9349.pdf"},{"id":107613733,"identity":"601721a3-c4ee-4577-b87a-ceaa2044e2d8","added_by":"auto","created_at":"2026-04-23 08:57:27","extension":"xlsx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":287956,"visible":true,"origin":"","legend":"","description":"","filename":"A.YakimenkoSupplementaryDataS1.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-9168576/v1/24fae581caf2eafc62c4ddc6.xlsx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Zircon behavior in the partially melted planetary mantle","fulltext":[{"header":"Introduction","content":"\u003cp\u003eZircon (Zr,Hf)SiO\u003csub\u003e4\u003c/sub\u003e is an orthosilicate and one of the most versatile geological tracers and planetary geochronometers \u003csup\u003e1\u003c/sup\u003e. Incorporation of rare and minor elements such as U, Th, Ti, Hf, and rare earth elements (REE) makes zircon a geochemical clue for rock dating (e.g., \u003csup\u003e2\u003c/sup\u003e), thermo-barometry, and oxygen barometry \u003csup\u003e3\u0026ndash;5\u003c/sup\u003e. Zircon is unique for its robustness due to its hardness and refractory properties. Furthermore, diffusion rates for many elements within zircon are extremely low \u003csup\u003e6\u003c/sup\u003e, allowing this mineral to retain the isotopic information even when exposed to high magmatic temperatures. These properties make it well-suited for reconstructing geological sources, the composition of the melts, physical chemical conditions, and the chronology of geological processes.\u003c/p\u003e\n\u003cp\u003eZircon crystals can grow from a melt or a fluid phase at a wide range of physical-chemical conditions in different geodynamic or tectono-magmatic environments. Zircon is a ubiquitous accessory mineral in silica-rich crustal rocks, whose geochemical indicators are widely used as markers of crustal growth, evolution, and processes in continental crust \u003csup\u003e7\u0026ndash;9\u003c/sup\u003e. In addition, numerous findings of zircon in mafic and ultramafic rocks (e.g., gabbros, dunites, and chromitites) \u003csup\u003e10\u0026ndash;16\u003c/sup\u003e suggest that zircon can grow and survive in the mantle-derived melts and can be used as a geochemical tracer of mantle processes. However, the mechanism of zircon growth and survival in mantle magmas remains unknown and requires knowledge of zircon saturation and Zr diffusion coefficients in mafic melts at high pressures. The limited data on the diffusion of Zr in synthetic melts \u003csup\u003e17\u0026ndash;22\u003c/sup\u003e and in natural tholeiitic basaltic and haplobasaltic melts \u003csup\u003e23\u003c/sup\u003e vary over 5 orders of magnitude. Furthermore, there is no data on the effect of high Zr contents close to the zircon saturation and the effect of high pressure corresponding to mantle conditions.\u003c/p\u003e\n\u003cp\u003ePrevious experimental studies demonstrated that zircon saturation strongly depends on temperature and melt composition \u003csup\u003e24,25\u003c/sup\u003e. Zircon dissolution was first examined in felsic and intermediate melts with varying water contents at pressures and temperatures associated with granitic magmatism in the Earth\u0026apos;s crust \u003csup\u003e24\u003c/sup\u003e. This study was expanded in \u003csup\u003e25\u003c/sup\u003e by conducting zircon dissolution experiments in melts ranging from rhyolite to basalt at 930\u0026ndash;1225\u0026ordm;C and building a model of zircon saturation in these melts. Both studies showed that Zr contents at zircon saturation increase strongly with decreasing silica and increasing alkali content of the melt and with temperature increase. The alkali and silica contents of the melt impose a major control on Zr contents at zircon saturation \u003csup\u003e24\u0026ndash;26\u003c/sup\u003e. The model by Boehnke et al. \u003csup\u003e25\u003c/sup\u003e extrapolated for basaltic melts produces unrealistically high Zr concentration (5000 ppm) required for the crystallization of zircon in basaltic liquids at temperatures above 900\u0026deg;C. DeLong and Chatelain \u003csup\u003e27\u003c/sup\u003e found that Zr concentrations in water-saturated MORB gabbro are seven times greater than in a felsic melt. They assumed that zircon begins crystallizing at 840\u0026deg;C due to the fractionation of modal phases.\u003c/p\u003e\n\u003cp\u003eThere are only a few experimental studies of zircon saturation in mafic and ultramafic systems \u003csup\u003e21,23,28,29\u003c/sup\u003e. Experimental data on zircon dissolution in anhydrous natural mid-ocean ridge basalt (MORB) by Borisova et al. \u003csup\u003e23\u003c/sup\u003e showed that typical 100 \u0026micro;m zircon crystals dissolve rapidly (~\u0026thinsp;10 h) upon reaction with basaltic melt at pressures of 0.2\u0026ndash;0.7 GPa if controlled by Zr diffusion. These findings raise questions about the origin and stability of zircon in the mantle and its survival in mafic magmas. However, these studies cover a very limited pressure range up to 0.7 GPa. The effect of pressure on zircon saturation in the mantle melts remains largely unknown above 0.7 GPa. Zhang and Xu \u003csup\u003e22\u003c/sup\u003e reported a decrease in zircon saturation from 1.26 to 1.10 wt% ZrO\u003csub\u003e2\u003c/sub\u003e with an increase in pressure from 0.5 to 1.5 GPa for rhyolitic melts. However, Boehnke et al. \u003csup\u003e25\u003c/sup\u003e found no significant pressure effect on zircon saturation at pressures less than 2.5 GPa. The model of Borisov and Aranovich \u003csup\u003e29\u003c/sup\u003e, developed for zircon saturation in mafic melts over a pressure range of 0.1 MPa to 2.5 GPa and a temperature range of 750\u0026ndash;1500\u0026deg;C, suggests that zircon crystallization in mafic melts is unlikely. However, the model is primarily based on experiments conducted at 1 atm (0.0001 GPa), and extrapolation to pressures as high as 2.5 GPa may introduce significant uncertainties. Crisp and Berry\u003csup\u003e30,31\u003c/sup\u003e developed a zircon solubility model for their experimental data on granitic to andesitic compositions at pressure from 0.0001 to 4.0 GPa and temperatures between 800 and 1500\u0026deg;C. However, their study did not address zircon solubility in mafic melts. Thus, the goal of our study is to examine the effect of pressure on zircon saturation and Zr diffusivity in basaltic melt using zircon dissolution experiments at 0.5, 1, and 2 GPa. The new data on Zr geochemistry at mantle conditions help to better understand the kinetics of zircon growth in the mantle and the Zr geochemical cycle during the subduction of basaltic crust into the mantle.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003eSaturation of mantle-derived melt with zircon\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eOur experiments investigated the effect of pressure between 0.5 and 2 GPa, over a temperature range of 1350 to 1550 \u0026deg;C, on zircon dissolution. Table 1 summarize the experimental conditions and the results of eight experimental runs reporting zircon saturation concentrations and Zr diffusion rates in basaltic melts. Zircon shows congruent dissolution in all runs (Fig. 1), and the diffusive boundary layer melt is produced between zircon and the mid-ocean ridge basalt (MORB) melt.\u0026nbsp;All runs except PC321 are super-liquidus and produced only glass in association with the partially dissolved zircon. The PC321 run (1400\u0026ordm;C and 2 GPa) developed euhedral crystals 10 to 50 microns in size along the zircon-glass interface with the composition similar to augite ((Ca\u003csub\u003e0.65\u003c/sub\u003e,Na\u003csub\u003e0.09\u003c/sub\u003e)(Mg\u003csub\u003e0.84\u003c/sub\u003e,Fe\u003csub\u003e0.19\u003c/sub\u003e,Al\u003csub\u003e0.17\u003c/sub\u003e)(Si\u003csub\u003e1.83\u003c/sub\u003e,Al\u003csub\u003e0.22\u003c/sub\u003e)O\u003csub\u003e6\u003c/sub\u003e) (Fig. S4) (Table 1). During diffusion-controlled dissolution, zircon saturation is reached in the melt at the zircon-melt interface. For this reason, we used the Zr content in the glass at the zircon-glass interface to obtain Zr concentration at the zircon saturation (C\u003csub\u003esat\u003c/sub\u003e). This concentration ranges in our experiments from 2.03 wt% ZrO\u003csub\u003e2\u003c/sub\u003e (at 2 GPa, 1400⁰C) to 7.73 wt% ZrO\u003csub\u003e2\u003c/sub\u003e (at 2 GPa, 1500⁰C) (Table 1). It positively correlates with temperature (Fig. 2A). We observed an increase in the zircon stability with pressure in the investigated pressure range. At 2 GPa, zircon saturation increases markedly at 1500 \u0026deg;C - 1550 \u0026deg;C (Table 1). However, zircon saturation reaches 6.18 wt% ZrO\u003csub\u003e2\u003c/sub\u003e at 1500\u0026deg;C, compared to 5.33 wt% ZrO\u003csub\u003e2\u003c/sub\u003e at 1550 \u0026deg;C (Fig. 2A).\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003cspan style='color: rgb(0, 0, 0); font-family: \"Times New Roman\"; font-size: medium; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: normal; background-color: rgb(255, 255, 255); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;'\u003eTable 1. Experimental conditions and results for zircon dissolution experiments in basalt (MORB). Zrn- zircon, Zircon\u0026nbsp;\u003c/span\u003e\u003cem style='color: rgb(0, 0, 0); font-family: \"Times New Roman\"; font-size: medium; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: normal; background-color: rgb(255, 255, 255); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;'\u003eC\u003csub\u003esat\u003c/sub\u003e\u003c/em\u003e\u003cspan style='color: rgb(0, 0, 0); font-family: \"Times New Roman\"; font-size: medium; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: normal; background-color: rgb(255, 255, 255); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;'\u003e\u0026nbsp;\u0026ndash; Zr concentration at zircon saturation,\u0026nbsp;\u003c/span\u003e\u003cem style='color: rgb(0, 0, 0); font-family: \"Times New Roman\"; font-size: medium; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: normal; background-color: rgb(255, 255, 255); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial;'\u003eD\u003csub\u003eZr\u003c/sub\u003e\u0026nbsp;\u003c/em\u003e\u003cspan style='color: rgb(0, 0, 0); font-family: \"Times New Roman\"; font-size: medium; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; white-space: normal; background-color: rgb(255, 255, 255); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;'\u003e\u0026ndash; Zr diffusion rate.\u003c/span\u003e\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" align=\"\" width=\"607\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eRun#\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eH\u003csub\u003e2\u003c/sub\u003eO, wt%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eT,\u003csup\u003eo\u003c/sup\u003eC\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 58px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eP, GPa\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eDuration, min\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePhases\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eZircon \u003cem\u003eC\u003csub\u003esat\u003c/sub\u003e\u003c/em\u003e, ZrO\u003csub\u003e2\u003c/sub\u003e wt%\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 76px;\"\u003e\n \u003cp\u003e\u003cstrong\u003e\u003cem\u003eD\u003csub\u003eZr\u003c/sub\u003e\u003c/em\u003e\u003c/strong\u003e\u003cstrong\u003e, cm\u003csup\u003e2\u003c/sup\u003e/s\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 104px;\"\u003e\n \u003cp\u003ePC343\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003e0.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e1550\u0026nbsp;\u0026plusmn; 20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 58px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003eGlass, Zrn\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 85px;\"\u003e\n \u003cp\u003e5.33\u0026nbsp;\u0026plusmn; 0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 76px;\"\u003e\n \u003cp\u003e2.03E-07\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 104px;\"\u003e\n \u003cp\u003ePC341\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003e0.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e1500\u0026nbsp;\u0026plusmn; 20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 58px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003eGlass, Zrn\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 85px;\"\u003e\n \u003cp\u003e6.18\u0026nbsp;\u0026plusmn; 0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 76px;\"\u003e\n \u003cp\u003e1.61E-07\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 104px;\"\u003e\n \u003cp\u003ePC333\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003e0.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e1450\u0026nbsp;\u0026plusmn; 20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 58px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003eGlass, Zrn\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 85px;\"\u003e\n \u003cp\u003e2.45 \u0026plusmn; 0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 76px;\"\u003e\n \u003cp\u003e8.30E-08\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 104px;\"\u003e\n \u003cp\u003ePC321\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003e5.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e1400\u0026nbsp;\u0026plusmn; 20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 58px;\"\u003e\n \u003cp\u003e2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003eGlass, Zrn, augite\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 85px;\"\u003e\n \u003cp\u003e2.03 \u0026plusmn; 0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 76px;\"\u003e\n \u003cp\u003e3.00E-08\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 104px;\"\u003e\n \u003cp\u003ePC328\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003e0.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e1450\u0026nbsp;\u0026plusmn; 20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 58px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e120\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003eGlass, Zrn\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 85px;\"\u003e\n \u003cp\u003e4.37 \u0026plusmn; 0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 76px;\"\u003e\n \u003cp\u003e2.03E-08\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 104px;\"\u003e\n \u003cp\u003ePC325\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003e0.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e1400\u0026nbsp;\u0026plusmn; 20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 58px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003eGlass, Zrn\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 85px;\"\u003e\n \u003cp\u003e3.75 \u0026plusmn; 0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 76px;\"\u003e\n \u003cp\u003e1.54E-08\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 104px;\"\u003e\n \u003cp\u003ePC314\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003e0.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e1350\u0026nbsp;\u0026plusmn; 20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 58px;\"\u003e\n \u003cp\u003e1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e60\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003eGlass, Zrn\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 85px;\"\u003e\n \u003cp\u003e2.12 \u0026plusmn; 0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 76px;\"\u003e\n \u003cp\u003e6.01E-09\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 104px;\"\u003e\n \u003cp\u003ePC332\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003e0.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e1400\u0026nbsp;\u0026plusmn; 20\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 58px;\"\u003e\n \u003cp\u003e0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003eGlass, Zrn\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 85px;\"\u003e\n \u003cp\u003e5.36 \u0026plusmn; 0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 76px;\"\u003e\n \u003cp\u003e8.26E-08\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd nowrap=\"\" style=\"width: 104px;\"\u003e\n \u003cp\u003eBorisova et al., 2020\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 62px;\"\u003e\n \u003cp\u003e0.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e1300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 58px;\"\u003e\n \u003cp\u003e0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 70px;\"\u003e\n \u003cp\u003e300\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 83px;\"\u003e\n \u003cp\u003eGlass, Zrn\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 85px;\"\u003e\n \u003cp\u003e2.82\u0026plusmn; 0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd nowrap=\"\" style=\"width: 76px;\"\u003e\n \u003cp\u003e2.87E-08\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eOur experiments demonstrate significantly lower Zr concentration at zircon saturation in basaltic melts than previous experiments \u003csup\u003e25\u003c/sup\u003e. For example, we obtained a zircon saturation of 2.1 wt% ZrO\u003csub\u003e2\u003c/sub\u003e at 1350\u0026deg;C and 1 GPa, which is less than half of the 4.5 wt% ZrO\u003csub\u003e2\u0026nbsp;\u003c/sub\u003ereported by \u003csup\u003e25\u003c/sup\u003e at 1225\u0026deg;C and 1 GPa. This effect can be explained by 1.5 times higher alkali content used in \u003csup\u003e25\u003c/sup\u003e, Indeed, it has been shown that as the (Na\u003csub\u003e2\u003c/sub\u003eO + K\u003csub\u003e2\u003c/sub\u003eO)/Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e rises from 1 to 2, Zr concentration increases from 1 to 4 wt% at 800 \u0026deg;C in felsic melts \u003csup\u003e24,26\u003c/sup\u003e. This suggests that zircon can be more stable in low-alkali mafic mantle-derived melts than previously expected.\u003c/p\u003e\n\u003cp\u003eWhen the latest model of Crisp and Berry \u003csup\u003e30,31\u003c/sup\u003e is applied to our experimental data, the predicted zircon saturation is two to three times higher than the saturation observed in our experiments (Fig. S5). This discrepancy may reflect differences in experimental methodology, as Crisp and Berry grew zircon crystals from melts oversaturated in Zr (15%) during experiments lasting 48 and 72 hours. In addition, their model was developed primarily for granitic and andesitic compositions, and experiments conducted at pressures above 1 GPa represent less than 10% of their dataset. As a result, the model may not adequately capture the effects of elevated pressure and mafic compositions on zircon saturation.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003ePrevious experimental studies of zircon dissolution have demonstrated that the Zr diffusion coefficient primarily depends on temperature, melt composition, and water content, while being less affected by pressure \u003csup\u003e23,32\u003c/sup\u003e. Higher temperatures and lower silica content in the melt increase the Zr diffusion and, therefore, zircon dissolution rate. Our diffusion data (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) show the fastest diffusion (D\u003csub\u003e\u003cem\u003eZr\u003c/em\u003e\u003c/sub\u003e) in basaltic melt at 1550\u0026deg;C (Fig. S6). Our obtained values of Zr diffusion coefficients in basalts are close to those in the same melt estimated by Borisova et al.\u003csup\u003e23\u003c/sup\u003e and lower than Zr diffusion coefficients derived by Holycross and Watson \u003csup\u003e21\u003c/sup\u003e (Fig. S6). Our experiments reveal a significant pressure control on the \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eZr\u003c/em\u003e\u003c/sub\u003e in the studied range of 0.5 to 2 GPa. Furthermore, they indicate that Zr diffusion varies non-linearly with pressure, where the lowest \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eZr\u003c/em\u003e\u003c/sub\u003e occurs at 1 GPa, while at 0.5 GPa and 2 GPa Zr diffusion is faster (Fig. S6 and Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). For example, at 1450\u0026deg;C, \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eZr\u003c/em\u003e\u003c/sub\u003e at 1 GPa is four times lower than at 2 GPa. The \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eZr\u003c/em\u003e\u003c/sub\u003e are nearly the same for 0.5 GPa at 1400\u0026deg;C and 2 GPa at 1450\u0026deg;C. At the same temperature of 1400\u0026deg;C, \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eZr\u003c/em\u003e\u003c/sub\u003e at 0.5 GPa is almost 3 times higher than at 2 GPa. This suggests that increased pressure slows down the diffusion of Zr. The maximum Zr diffusivity \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eZr\u003c/em\u003e\u003c/sub\u003e = 2.03\u0026middot;10\u003csup\u003e\u0026minus;\u0026thinsp;7\u003c/sup\u003ecm\u003csup\u003e2\u003c/sup\u003e/s was observed at the highest temperature studied of 1550⁰C and 2 GPa.\u003c/p\u003e \u003cp\u003eWe compared our data to previous studies by calculating Zr diffusion coefficients using the equation from Zhang and Xu \u003csup\u003e22\u003c/sup\u003e. Fig. S7 shows that our experimentally derived Zr diffusivity in basaltic melt aligns with the diffusion coefficients calculated using Zhang's model within 18% relative error. However, because this model was developed for experiments below 1 GPa, it cannot fully account for the pressure effect observed in our experiments at 2 GPa.\u003c/p\u003e \u003cp\u003eTo investigate the dependence of the Zr diffusion coefficient from temperature, we applied the Arrhenius equation for MORB at 1 GPa and 2 GPa:\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\(\\:D={D}_{0}\\bullet\\:{e}^{\\frac{-{E}_{a}}{RT}},\\)\u003c/span\u003e \u003c/span\u003e (Eq.\u0026nbsp;\u003cspan refid=\"Equ1\" class=\"InternalRef\"\u003e1\u003c/span\u003e),\u003c/p\u003e \u003cp\u003ewhere \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:D\\:\\text{\\--}\\)\u003c/span\u003e\u003c/span\u003e diffusion coefficient, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{D}_{0\\:}\\text{\\--}\\)\u003c/span\u003e\u003c/span\u003e pre-exponential factor (constant in cm\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e), \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{E}_{a}\\)\u003c/span\u003e\u003c/span\u003e​\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\:\\text{\\--}\\)\u003c/span\u003e\u003c/span\u003e activation energy (J/mol), \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:R\\:\\text{\\--}\\)\u003c/span\u003e\u003c/span\u003e gas constant (J/(mol\u0026middot;K)), \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:T\\:\\text{\\--}\\)\u003c/span\u003e\u003c/span\u003e temperature (K). We obtained Arrhenius relationship for \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eZr\u003c/em\u003e\u003c/sub\u003e at 1350, 1400, and 1450\u0026ordm;C at 1 GPa and 1450, 1500, and 1550\u0026ordm;C at 2 GPa. Zr diffusivities were fit using a linear regression to find the slope and activation energy of the Arrhenius equation for Zr diffusion rate (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB). Standard error (σ) estimation for diffusion coefficients was acquired from least-squares fits of the experimental data at a given temperature. The slope in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB is proportional to \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003ea\u003c/em\u003e\u003c/sub\u003e, which is estimated to be 283.82\u0026thinsp;\u0026plusmn;\u0026thinsp;19.13 kJ/mol with \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e of 8.98 cm\u0026sup2;/s at 1 GPa. This activation energy differs from the previous estimate 219.73\u0026thinsp;\u0026plusmn;\u0026thinsp;17.80 kJ/ mol and \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e of 1.41 cm\u0026sup2;/s for Zr as a trace element in basalts \u003csup\u003e21\u003c/sup\u003e, because, in our study, Zr becomes a major element within the boundary layer (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). At 2 GPa, we estimated the activation energy to be 234.38\u0026thinsp;\u0026plusmn;\u0026thinsp;13.75 kJ/mol, and \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003e0\u003c/em\u003e\u003c/sub\u003e is 1.13 cm\u0026sup2;/s. The \u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003ea\u003c/em\u003e\u003c/sub\u003e = 283.82\u0026thinsp;\u0026plusmn;\u0026thinsp;19.13 kJ/mol for Zr diffusion at 1 GPa obtained in our study for MORB with non-bridging oxygens to tetrahedral cations (NBO/T) of 0.83 is even higher than the activation energies for self-diffusion of network formers, such as Si at 227\u0026thinsp;\u0026plusmn;\u0026thinsp;13 kJ/mol (1 GPa) and O at 215\u0026thinsp;\u0026plusmn;\u0026thinsp;13 kJ/mol (1 GPa) \u003csup\u003e33\u003c/sup\u003e. In fact, diffusion becomes faster at higher pressures for tightly packed aluminosilicate melts such as basalt \u003csup\u003e34\u003c/sup\u003e. The effect of pressure is likely due to the structural compaction within the melt, which reduces energy barriers for atomic motion \u003csup\u003e35\u003c/sup\u003e. It suggests that at concentrations close to zircon saturation, Zr in the boundary layer behaves as a network former. This effect slows down Zr diffusion and suppresses dissolution of zircon compared to the diffusion of trace amounts of Zr, studied by Holycross and Watson at 1 GPa (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB). Importantly, the higher Zr diffusion at 2 GPa compared to that at 1 GPa can be explained by the lower viscosity of the aluminosilicate melts at high pressure \u003csup\u003e34\u003c/sup\u003e and by the similar behavior of Zr to the network-forming Si and O ions in the melts. This fact is directly related to high Zr concentration in the diffusive boundary layer melt produced due to zircon dissolution. High Zr in the aluminosilicate melts is a trigger for the combination of ZrO\u003csub\u003e6\u003c/sub\u003e with SiO\u003csub\u003e4\u003c/sub\u003e to polyhedron ZrO\u003csub\u003e6\u003c/sub\u003eSiO\u003csub\u003e4\u003c/sub\u003e and the related network connectivity \u003csup\u003e36,37\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eTo determine how long zircon survives in basaltic melt, we applied Harrison and Watson's model \u003csup\u003e32\u003c/sup\u003e. The time required for zircon crystals of a given radius to dissolve is a function of temperature at 1 and 2 GPa pressures. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB shows that our results follow the same trend as Harrison and Watson's data for anhydrous felsic melts. This similarity is due to our use of the same experimental approach of diffusion-controlled dissolution. In this approach, Zr diffusion and zircon saturation are measured within the interface melt saturated in zircon and confined by a boundary layer. Under these conditions, zirconium (Zr) is a major element in the melt structure where Zr is the network-former cation.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e\n\u003ch3\u003eImplications for zircon stability and Zr geochemistry in the mantle\u003c/h3\u003e\n\u003cp\u003eThe results of our experiments indicate that zircon in mid-ocean ridge basalt undergoes only congruent dissolution at pressures between 0.5-2 GPa and temperatures of 1350\u0026ndash;1550\u0026deg;C. Zircon is more stable than previously predicted by earlier models \u003csup\u003e29,30\u003c/sup\u003e. Zircon saturation decreases as pressure increases to 2 GPa, indicating the higher stability of zircon at depths of up to 30\u0026ndash;60 km.\u003c/p\u003e \u003cp\u003eAt 1\u0026ndash;2 GPa, the Zr diffusivity in the boundary layer melts as a major element (\u0026gt;\u0026thinsp;1 wt%) becomes slower compared to the diffusivity of Zr in trace concentrations (ppm), decreasing zircon dissolution/crystallization rates in the deep upper mantle melt, which is likely related to the structural role of Zr as a network former ion. Considering slow Zr diffusion in this boundary layer melt to be the rate limiting process for the zircon dissolution/crystallization, the optimal conditions for preserving zircon in basaltic melt occur at temperatures between 1400 and 1500\u0026ordm;C at a pressure of 1\u0026ndash;2 GPa. This physical-chemical stabilization allows zircon to survive and/or recrystallize in the basaltic or hybrid melt at depths of up to 30\u0026ndash;60 km and to remain preserved until the uplift, during slab-mantle interactions, as well as crust-mantle interactions such as delamination and rejuvenation (see Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e in \u003csup\u003e38\u003c/sup\u003e).\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eExperimental methods\u003c/h2\u003e \u003cp\u003eExperiments were conducted using a piston-cylinder apparatus at the Experimental Petrology lab, Department of Earth and Environmental Sciences, Dalhousie University (Halifax, Nova Scotia). A double-polished disk of natural zircon was placed at the bottom of a noble metal capsule and filled with natural mid-ocean ridge basalt (MORB). Au\u003csub\u003e80\u003c/sub\u003ePd\u003csub\u003e20\u003c/sub\u003e alloy capsules and pure Pt capsules, each with a 3 mm outer diameter, were used as sample containers at temperatures of 1300\u0026ndash;1350\u0026deg;C and 1350\u0026ndash;1450\u0026deg;C, respectively. Runs conducted in Pt capsules experienced an iron loss of about 5 wt% FeO (total), which didn\u0026rsquo;t affect the overall structure of the melt.\u003c/p\u003e \u003cp\u003eWe used zircon chips from the ~\u0026thinsp;730 Ma Mud Tank carbonatite (Australia) \u003csup\u003e39\u003c/sup\u003e, known for their low trace element content, making them ideal for dissolution experiments \u003csup\u003e23,32\u003c/sup\u003e. The zircon slides were polished on both sides to a thickness of 1.15 to 1.65 mm. After polishing, the disks were cut to a diameter of 2.25 mm and ultrasonically cleaned in ethanol for 5 minutes. The disks were examined under a stereomicroscope to select the cleanest, most transparent, and with minimal cracks or inclusions, and to check the quality of the polishing.\u003c/p\u003e \u003cp\u003eThe mid-ocean ridge basalt (MORB) glass used in our experiments is a typical moderately differentiated (8.2 wt% of MgO, Table \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e) glassy tholeiitic basalt (number 3786/3) from Knipovich ridge of the Mid-Atlantic Ridge \u003csup\u003e23,40\u003c/sup\u003e. The MORB glass has been crushed to a powder (\u0026lt;\u0026thinsp;100 \u0026micro;m glass size). The starting material was loaded directly into the noble metal capsule, and oxygen fugacity (\u003cem\u003ef\u003c/em\u003eO\u003csub\u003e2\u003c/sub\u003e) was not controlled using an additional buffer. We assumed \u003cem\u003ef\u003c/em\u003eO\u003csub\u003e2\u003c/sub\u003e to be buffered by the enclosing NaCl-Pyrex assembly, approximating near NNO conditions (average NNO\u0026thinsp;=\u0026thinsp;0.1, following \u003csup\u003e41\u003c/sup\u003e). The loaded capsules were subsequently welded shut and dried in an oven at 100\u0026deg;C for 12 hours. In one experiment, water was added with a microsyringe.\u003c/p\u003e \u003cp\u003eThe capsules were loaded into a 1/2 inch assembly, which included a NaCl cell, Pyrex glass, graphite furnace, and crushable MgO inserts (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e). The accuracy of pressure calibrated using diopside melting at 1 GPa and 1530\u0026deg;C \u003csup\u003e42\u003c/sup\u003e was better than 5%, and no pressure correction was applied. The temperatures were monitored with a Eurotherm controller using W\u003csub\u003e95\u003c/sub\u003eRe\u003csub\u003e5\u003c/sub\u003e\u0026ndash;W\u003csub\u003e74\u003c/sub\u003eRe\u003csub\u003e26\u003c/sub\u003e thermocouple without any correction for pressure on emf. Thermal gradients within the capsule were \u0026plusmn;\u0026thinsp;15\u0026deg;C at 1300\u0026deg;C, established by the spinel thermometer \u003csup\u003e43\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe thermocouple was housed in an alumina sleeve and positioned at the top of the sample capsule, separated by an Al\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e3\u003c/sub\u003e disc (0.5 mm thickness), ensuring accurate temperature measurement without direct contact between the thermocouple and the capsule.\u003c/p\u003e \u003cp\u003eThe experiments were conducted at pressures ranging from 0.5 to 3 GPa and temperatures from 1300 to 1450\u0026deg;C, with durations varying from 15 minutes to 5 hours. Shorter 15-minute runs were used for determining Zr diffusion in the boundary melt, whereas the extended runs\u0026thinsp;\u0026gt;\u0026thinsp;2 hours were effective in determining zircon saturation.\u003c/p\u003e \u003cp\u003eInitially, each sample was pressurized to approximately 3 MPa, heated to 600\u0026deg;C at a rate of 50\u0026deg;C/min, and held at that temperature for 6 minutes while the pressure increased to the desired value. The temperature was then ramped up to the final temperature at a rate of 50\u0026deg;C/min (for longer runs) or 100\u0026deg;C/min (for 15-minute runs) and pressure adjusted to the final value (T systematic error = -5\u0026deg;C). If the pressure deviated by more than 10% during the run, it was adjusted back to the run value. The quenching was achieved by cutting power to the graphite furnace, which brought the sample to room temperature within a few seconds. To prevent cracking, runs at 2 GPa and 3 GPa were slowly decompressed. The pressure on the piston was decreased by 2.1\u0026ndash;2.8 MPa every 5 minutes until it reached 5.5\u0026ndash;6.0 MPa. After each experiment, the capsules were sliced in half with a diamond saw, mounted in epoxy, and polished using diamond paste to expose the zircon-melt boundary. The polished sections were observed under an optical microscope and a scanning electron microscope (SEM) before analyses with electron probe microanalysis (EPMA).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eAnalytical techniques\u003c/h2\u003e \u003cp\u003eThe experimental products were initially analyzed under a petrographic microscope to identify dissolution textures. Identification of baddeleyite ZrO\u003csub\u003e2\u003c/sub\u003e and other phases, as well as initial measurement of Zr concentrations in the glass adjacent to the zircon crystal, were performed on carbon-coated samples (~\u0026thinsp;20 nm) using energy dispersive spectroscopy (EDS) and backscattered electron (BSE) imaging on a Tescan Mira3 Field-Emission Scanning Electron Microscope (FE-SEM) at Saint Mary\u0026rsquo;s University, Halifax, Canada. Operating conditions included a 20 kV accelerating voltage, 5 nm beam size, and a beam current of 260 pA.\u003c/p\u003e \u003cp\u003eWe employed electron microprobe analysis (EMPA) to determine the Zr concentration and to obtain its profile in the reaction zones. Major and minor element content (including Zr) in crystals and glasses was determined using wavelength-dispersive spectrometry (WDS) on a CAMECA SX-Five microprobe at Centre Castaing, Toulouse, France. Operating conditions for the electron microprobe were: an accelerating voltage of 15 kV, currents of 100 nA, and a 2 \u0026times; 2 \u0026micro;m spot beam. The detection limit for Zr was estimated as 70 ppm; this value was derived from the Cameca SX Five software based on the MPI-DING standard glasses. The synthetic reference MPI-DING glasses of mafic and ultramafic composition (AT-HO, St-HS \u003csup\u003e44\u003c/sup\u003e) obtained from natural rock powders were analyzed as unknown samples to monitor the accuracy of the major and trace element analyses. The standard deviation estimated on the reference glasses ranges from 0.7 to 1 wt%.\u003c/p\u003e \u003cp\u003eCompositional profiles were measured in the glass perpendicular to the zircon disc, starting from the interface (Fig. \u003cspan refid=\"MOESM2\" class=\"InternalRef\"\u003eS2\u003c/span\u003e). The linear interface allowed for corrections of secondary fluorescence effects, ensuring accurate zircon (Zr) concentrations in the interface glasses, using the method described in \u003csup\u003e23\u003c/sup\u003e. The secondary fluorescence effect was calculated using the \"numpy.interp\" function in Python (version 1.17) \u003csup\u003e45\u003c/sup\u003e. However, this effect contributes less than 1% to each measurement, meaning it is negligible compared to the relative error.\u003c/p\u003e \u003c/div\u003e\n\u003ch3\u003eZr diffusion coefficient extraction\u003c/h3\u003e\n\u003cp\u003eThe extraction of the Zr diffusion coefficient from the profiles of Zr concentration at the zircon-glass interface (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003eA) was performed using the method from Harrison and Watson \u003csup\u003e32\u003c/sup\u003e. The concentrations of Zr measured in the profiles were converted to the inverse error function (erf⁻\u0026sup1; (1 \u0026ndash; C\u003csub\u003ex\u003c/sub\u003e/C\u003csub\u003eo\u003c/sub\u003e )), revealing a linear correlation with the distance from the interface.\u003c/p\u003e \u003cp\u003eFor each sample, we analyzed two or three parallel compositional profiles perpendicular to the zircon-melt interface to confirm that zircon dissolution is controlled by Zr diffusion in the melt. The identical shape of these parallel profiles allowed us to extract the Zr diffusion coefficient. In addition, a linear correlation of the erc function with the profile distance from the interface was an additional test confirming that the zircon dissolution in our runs was controlled by Zr diffusion without any additional effect of convection. The shape of the profile shown in Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e suggests that congruent zircon dissolution is primarily controlled by Zr diffusion, according to the criterion established by Harrison and Watson \u003csup\u003e32\u003c/sup\u003e. In this case, the slope (m) of the error function graph (Fig. S3B) is equal to\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:m\\:=\\frac{1}{\\sqrt{4Dt}}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:D\\:\\)\u003c/span\u003e\u003c/span\u003eis the diffusion coefficient (cm\u003csup\u003e2\u003c/sup\u003e/s), \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:t\\:\\)\u003c/span\u003e\u003c/span\u003eis the experiment duration (s), which\u003c/p\u003e \u003cp\u003eallows to extract the Zr diffusion coefficient as:\u003cdiv id=\"Equ2\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ2\" name=\"EquationSource\"\u003e\n$$\\:D=\\:\\frac{1}{4\\:{m}^{2}t}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e2\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003eThe plots for all experimental runs used for Zr diffusion extraction can be found in Supplementary Fig.\u0026nbsp;1, and the values of the Zr diffusion coefficient are presented in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The R-squared values of the trend line (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003eB) for the Zr diffusion calculations ranged from 0.989 to 0.999, indicating high reliability of this approach.\u003c/p\u003e \u003cp\u003eIn sample PC321 at 1400\u0026ordm;C and 2 GPa, we observed the formation of isometric crystals from 20 to 40 microns in size, with a chemical composition similar to augite ((Ca,Na)(Mg,Fe,Al)(Si,Al) \u003csub\u003e2\u003c/sub\u003eO \u003csub\u003e6\u003c/sub\u003e) at the zircon-glass interface. We measured the Zr profile in this sample while avoiding the crystals. Since this phase does not concentrate Zr in its crystal structure (according to EPMA analysis), the Zr content profile appeared sufficient for extracting the diffusion coefficient.\u003c/p\u003e \u003cp\u003eThe Zr diffusion coefficients are affected by zircon dissolution textures. In samples where only the zircon crystal and homogeneous glass are present, Harrison and Watson's method for the calculation of Zr diffusion coefficients is effective. In sample PC321, a liquidus phase is present alongside glass. We were able to calculate diffusion for this sample because the rare augite crystals formed did not contain Zr, and the crystal growth did not affect the Zr content in glass.\u003c/p\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eThermodynamic modeling\u003c/h2\u003e \u003cp\u003eTo estimate the silica activity in our experiments, we performed MELTS thermodynamic equilibrium calculations in the basalt system. Calculations were conducted at a temperature range from 1350\u0026deg; to 1550\u0026deg;C and pressures of 0.5 to 2 GPa. Modelling of thermodynamic equilibrium phases was performed using the rhyolite-MELTS (version 1.0.1) and pMELTS (version 5.6.1, published 13 November 2016) software \u003csup\u003e46\u003c/sup\u003e. PERPLE_X modelling (version 7.1.5, published 12 January 2023) was used to calculate the reaction zircon-baddeleiyte on the P-T diagram and to compare it to the experimental data. The database was set to hp633ver.dat \u003csup\u003e47\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments:\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding:\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eEuropean Research Council grant [ERC Advanced ADG 101141259 PLANETAFELSIC] (AB)\u003c/p\u003e\n\u003cp\u003eNSERC Discovery grant [RGPIN-2020-06718] and International Alliance Catalyst grant [ALLRP/587298 -2023] (YF)\u003c/p\u003e\n\u003cp\u003eAY thanks Mitacs for Mitacs Globalink Research Award [IT38392]\u003c/p\u003e\n\u003cp\u003eDalhousie Earth And Environmental Sciences Doctoral (AY)\u003c/p\u003e\n\u003cp\u003eTESS Booster grant (AY)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions:\u003c/strong\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eConceptualization: AB, YF\u003c/p\u003e\n\u003cp\u003eMixture preparation: AY, LF\u003c/p\u003e\n\u003cp\u003eExperiments: AY, LF\u003c/p\u003e\n\u003cp\u003eAnalytical techniques: AY, AB\u003c/p\u003e\n\u003cp\u003eFunding acquisition: AB, YF, AY\u003c/p\u003e\n\u003cp\u003eSupervision: YF, AB\u003c/p\u003e\n\u003cp\u003eWriting \u0026ndash; original draft: AY, YF, AB\u003c/p\u003e\n\u003cp\u003eWriting \u0026ndash; review \u0026amp; editing: AY, YF, AB\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests:\u003c/strong\u003e Authors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData and materials availability:\u003c/strong\u003e All data are available in the main text or the supplementary materials.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMoser, D. 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An internally consistent thermodynamic data set for phases of petrological interest. \u003cem\u003eJournal of metamorphic Geology\u003c/em\u003e \u003cstrong\u003e16\u003c/strong\u003e, 309-343 (1998). \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"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":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-9168576/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9168576/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eZircon (Zr,Hf)SiO\u003csub\u003e4\u003c/sub\u003e, a common mineral in felsic rocks, preserves invaluable information about the parental magmas due to its exceptional stability. Findings of cm-size zircon crystals in (ultra)mafic rocks are at odds with the experimentally derived high dissolution rates and saturation at low pressures (\u0026lt;\u0026thinsp;1 GPa) in low-silica melts. To explore the zircon stability in the mantle, we established the saturation and the kinetics of zircon dissolution in basaltic melt at 0.5-2 GPa and discovered zircon stabilization at 1\u0026ndash;2 GPa. Our discovery of zircon stabilization with pressure and slower Zr diffusion as a network-former in major element contents (wt% ZrO\u003csub\u003e2\u003c/sub\u003e) compared to the network modifier in trace contents (ppm Zr) provides unique physical chemical conditions for zircon survival and the dissolution-recrystallization in the crust-mantle system.\u003c/p\u003e","manuscriptTitle":"Zircon behavior in the partially melted planetary mantle","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-04-23 08:56:21","doi":"10.21203/rs.3.rs-9168576/v1","editorialEvents":[{"type":"communityComments","content":1},{"type":"reviewerAgreed","content":"177972290264072871189910224855990710020","date":"2026-05-18T02:09:59+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-04-15T09:24:56+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-21T04:31:24+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-21T04:30:26+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2026-03-19T10:41:55+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"a11fee04-f427-4f25-b2d5-8fbce4870588","owner":[],"postedDate":"April 23rd, 2026","published":true,"recentEditorialEvents":[{"type":"reviewerAgreed","content":"177972290264072871189910224855990710020","date":"2026-05-18T02:09:59+00:00","index":16,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":66358539,"name":"Physical sciences/Materials science"},{"id":66358540,"name":"Earth and environmental sciences/Solid earth sciences"}],"tags":[],"updatedAt":"2026-04-23T08:56:22+00:00","versionOfRecord":[],"versionCreatedAt":"2026-04-23 08:56:21","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9168576","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9168576","identity":"rs-9168576","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}