Geochemistry Geophysics Geosystems最新文献

{"title":"Insights Into Subduction-Zone Fluid-Rock Interactions and Carbon Cycling From Magnesium Isotopes of Subducted Ophiolitic Mélanges in the Arabian-Nubian Shield","authors":"Yuan-Ru Qu,&nbsp;Sheng-Ao Liu,&nbsp;Hamed Gamaleldien","doi":"10.1029/2024GC011918","DOIUrl":"https://doi.org/10.1029/2024GC011918","url":null,"abstract":"<p>Fluid-rock interactions play an important role in element mobilization, mass transfer, and formation of critical metals in subduction zones. However, tracking the multistage fluid-rock interactions within subduction channels remains elusive. Here we conducted bulk-rock major and trace element and magnesium (Mg) isotopic analyses on a suite of subducted ophiolitic mélange rocks from Wadi Al Barramiyah in the Arabian-Nubian Shield of the Eastern Desert (ED) of Egypt. The rock suite includes serpentinites, talc rocks, talc-dolomite rocks, tremolite-dominated schists, and marbles. Talc rocks are characterized by low MgO contents and high δ²⁶Mg_DSM-3 values (0.03–0.13‰) relative to serpentinites (−0.18‰), indicating the release of isotopically light fluid during the metasomatic replacement of antigorite by talc. Tremolite-dominated schists and talc-dolomite rocks display higher CaO contents and lower δ²⁶Mg (−0.25‰ to −0.03‰ and −1.04‰ to −0.18‰, respectively) than those of talc rocks and serpentinites. These signatures, along with high CaO/Al₂O₃ and low Rb/Sr ratios, indicate infiltration of low-δ²⁶Mg carbonate-rich fluids, supported by extremely low δ²⁶Mg (down to −2.38‰) observed in nearby marbles. Our findings demonstrate that antigorite dehydration liberates substantial numbers of H₂O-rich fluids, facilitating the dissolution of carbonate minerals in marbles. Subsequent carbonate metasomatism effectively sequesters carbon from aqueous carbon-bearing fluids, transforming silicate minerals into carbonates. These new results highlight the significant role of mélange rocks in the multistage fluid-rock interactions and carbon recycling in subduction zones, offering valuable insights into mantle Mg isotopic heterogeneity and crust-mantle interactions.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 3","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011918","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143688894","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Constraining the Effect of Bathymetric High Subduction in an Accretionary Wedge: Evidence From the Tokai Area of the Nankai Trough, Japan","authors":"Andrzej Górszczyk,&nbsp;Rafael Almeida,&nbsp;Romain Brossier,&nbsp;Ludovic Métivier,&nbsp;Stéphane Operto","doi":"10.1029/2024GC011754","DOIUrl":"https://doi.org/10.1029/2024GC011754","url":null,"abstract":"<p>The Tokai area in the eastern Nankai Trough is characterized by the subduction of a rough plate interface caused by bathymetric highs related to the adjacent Izu-Bonin arc and fault fabrics in the oceanic crust. However, the effect of this process on the structural development of its accretionary wedge and megathrust seismicity is still poorly understood. To get better insight into Tokai area we apply full-waveform inversion to legacy wide-angle seismic data exploiting available signal frequency up to 15 Hz. From this model we extract pseudo-reflectivity attributes, which are complementary to the section obtained with Kirchoff pre-stack depth migration of streamer data. The high-resolution images reveal detailed geological characterization of the subducting oceanic crust, the geometry of the megathrust and splay faults, and the structure of the wedge. The latter is characterized by imbricate fans, out-of-sequence thrusts, and duplexes that significantly contribute to its thickening. We compare these features to published structural models and propose that the increased structural complexity in the Tokai segment is due to fault reactivation triggered by the subduction of the bathymetric highs. We suggest that this fault reactivation also controls the shallow seismogenic behavior of this region. We show that the evolution of the forearc basin is related to the ongoing underplating process and out-of-sequence thrusting within the wedge. We compare our seismic imaging results with bathymetric, magnetic, and gravity data, revealing no evidence of large ridges beneath our profile, which previous studies have proposed as a cause of the persistent Tokai seismic gap.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 3","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011754","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143688895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Triassic Tectonic Affinity to Indochina-East Malaya Block for West Sumatra and Paleo-Tethys Implications: Constraints From Late Triassic Igneous Rocks","authors":"Xin Qian,&nbsp;Shaojie Jin,&nbsp;Tianxing Bai,&nbsp;Xiaoqing Yu,&nbsp;Thomas C. Sheldrick,&nbsp;Chengshi Gan,&nbsp;Khairul Azlan Mustapha,&nbsp;Sayed Murtadha,&nbsp;Yuejun Wang","doi":"10.1029/2024GC012030","DOIUrl":"https://doi.org/10.1029/2024GC012030","url":null,"abstract":"<p>Mesozoic igneous rocks from Sumatra provide crucial insights into the temporal-spatial connection with the Eastern Tethys Domain. This study presents new zircon ages and whole-rock elemental data for the Late Triassic igneous rocks in West Sumatra. These igneous rocks yield consistent ages of 227–211 Ma. Granitoid and rhyolite exhibit A-type affinities with high K₂O and FeOt contents, and are depleted in HFSEs. They have similar <i>ε</i>_Nd (<i>t</i>) values of −8.3 to −5.0, <i>ε</i>_Hf (<i>t</i>) values of −8.0 to +1.4, and initial ratios for ²⁰⁶Pb/²⁰⁴Pb (18.71–19.17), ²⁰⁷Pb/²⁰⁴Pb (15.74–15.77) and ²⁰⁸Pb/²⁰⁴Pb (39.28–39.48). They were derived from an “ancient” meta-mafic source with a juvenile mafic crust component. Mafic-intermediate igneous rocks can be classified as medium- to high-K calc-alkaline series and are characterized by depletion in Nb, Ta, and Ti. Mafic-intermediate volcanic rocks show higher <i>ε</i>_Nd (<i>t</i>) values of −0.7 to +1.3 and <i>ε</i>_Hf (<i>t</i>) values of +3.5 to +4.2 than the diabases with <i>ε</i>_Nd (<i>t</i>) of −9.0 to −8.5 and <i>ε</i>_Hf (<i>t</i>) of −5.5 to −1.2. All these igneous rocks share similar initial ratios for ²⁰⁶Pb/²⁰⁴Pb (18.62–18.84), ²⁰⁷Pb/²⁰⁴Pb (15.68–15.75) and ²⁰⁸Pb/²⁰⁴Pb (38.67–39.05), suggesting a metasomatized lithospheric mantle origin. These Late Triassic igneous rocks share similar isotopic compositions with the synchronous post-collisional igneous rocks along the Eastern Paleo-Tethys giant igneous belt and were formed in a post-collisional extensional setting. Regional stratigraphy and detrital zircon observations indicate that West Sumatra constitutes the southern part of the Indochina-East Malaya Block, and the Eastern Paleo-Tethys zone likely extends into Sumatra.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 3","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012030","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143689164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"S-to-P Receiver Function Imaging of Lithospheric Discontinuities in New Zealand at the Hikurangi Subduction Zone","authors":"William A. Buffett,&nbsp;Catherine A. Rychert,&nbsp;Nicholas Harmon","doi":"10.1029/2024GC011897","DOIUrl":"https://doi.org/10.1029/2024GC011897","url":null,"abstract":"<p>Subduction zones are important regions for understanding plate tectonic processes. New Zealand experiences slow slip, volcanism, and back-arc rifting, and has evidence of large megathrust events and tsunamis. We use <i>S</i>-to-<i>P</i> receiver functions to image lithospheric discontinuities beneath the North Island of New Zealand. A positive discontinuity interpreted as the Moho is imaged at 15–30 ± 3 km depth beneath the overriding Australian Plate. In some locations, near the interface of the Pacific and Australian Plates, we don't image the Pacific Plate Moho, and the Australian Plate Moho is faint or absent. The former could be related to the increasing dip or eclogitization of the Pacific Plate crust, and the latter is likely related to mantle wedge serpentinization. A negative velocity discontinuity associated with the lithosphere-asthenosphere boundary (LAB) of the Australian Plate is imaged at 63–80 ± 8 km depth across the northwestern side of the island. Negative discontinuities are imaged beneath the southern Pacific Plate at 85–105 ± 10 km and 130 ± 13 km depth, representing either a mid-lithospheric discontinuity (MLD) and a deeper LAB, or more likely a shallow LAB and a deeper artifact, given that the latter is better aligned with previous work. Beneath the Australian Plate, asthenospheric melt is inferred in the northwest beneath several regions of active volcanism. Beneath the Pacific Plate, asthenospheric melt is inferred near the trench, also corresponding to the transition to where the plates become locked; therefore, plate locking could be related to the buoyancy of the melt.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 3","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011897","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143646074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Paleogeography of the Southern Tarim Terrane Revealed by Neoproterozoic Mafic Dyke Swarm in Altyn","authors":"Xian-Tao Ye,&nbsp;Wen-Jun Hu,&nbsp;Chuan-Lin Zhang,&nbsp;Wei Gan,&nbsp;Rui-Chen Gao,&nbsp;Ming-Can Yang","doi":"10.1029/2024GC012058","DOIUrl":"https://doi.org/10.1029/2024GC012058","url":null,"abstract":"<p>Using high-resolution remote sensing images and detailed field investigations, this study provides the spatiotemporal distribution and geometry of the Neoproterozoic giant mafic dyke swarm in the southeastern Tarim Craton, which is crucial for reconstructing the paleogeographic position of the Tarim Craton within the Rodinia supercontinent. This dyke swarm extends over 600 km in length and 20 km in width, spanning more than 12,000 km². Individual dykes ranged from 1.9 to 168 m in thickness and from 27 to 2,778 m in length. The mafic dykes were emplaced at 933–914 Ma, and exhibit trace element and isotope compositions similar to those of enriched mid-ocean ridge basalts (E-MORBs). The mantle potential temperature and pressure of the primary magma were estimated at ∼1,570°C and ∼4.0 GPa, respectively. The large-scale dyke swarm, together with its geochemical signatures and estimated P-T conditions, proposed that these dykes were generated by interaction between a Neoproterozoic mantle plume and the asthenospheric mantle. In addition, the Neoproterozoic giant mafic dyke swarm shares a close spatial and temporal relationship with the ∼890 Ma Sailajiazitage large igneous province in the southwestern Tarim Craton. Similar 930–890 Ma mafic dyke swarms have also been identified in North China Craton, São Francisco Craton, and Congo Craton, indicating the presence of a single giant mantle plume beneath the Rodinia supercontinent. Together with the sedimentary records and paleomagnetic data, it is proposed that the Southern Tarim Terrane was located adjacent to the São Francisco Craton and Congo Craton in the Northern Hemisphere.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 3","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012058","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143638900","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Refining the Eruption Chronology of Atitlán Caldera Through Zircon Double-Dating","authors":"Alejandro Cisneros de León,&nbsp;Martin Danišík,&nbsp;Axel K. Schmitt,&nbsp;Julie C. Schindlbeck-Belo,&nbsp;Steffen Kutterolf,&nbsp;Tushar Mittal,&nbsp;Jennifer M. Garrison,&nbsp;Kenneth W. W. Sims","doi":"10.1029/2024GC011953","DOIUrl":"https://doi.org/10.1029/2024GC011953","url":null,"abstract":"<p>Precise dating of Quaternary volcanism is vital for risk mitigation, understanding volcano-climate interactions, and deciphering the evolution of large silicic magmatic systems. The Atitlán caldera in Guatemala has experienced major eruptions that challenge radiometric dating techniques and complicate eruption chronology in this densely populated area. This study refines the eruptive history of Atitlán caldera using zircon double-dating (ZDD: combined [U-Th]/He and ²³⁸U-²³⁰Th disequilibrium dating). We present new ZDD eruption ages for previously undated events, including the I-tephra and the newly discovered Atitlán Early Tephra (AET). Additionally, we provide crystallization dates for the Los Chocoyos (LCY) supereruption, utilizing ultra-distal samples from the Pacific Ocean, Lake Petén Itzá, and Mexico. ZDD was also applied to the ⁴⁰Ar/³⁹Ar sanidine-dated W-tephra confirming its reliability. Our findings yield an internally consistent chronology, with the first radiometric ages of 64 ± 8 ka for the I-tephra and 497 ± 12 ka for AET. The ZDD eruption age of 160 ± 9 ka for W-tephra corroborates the existing ⁴⁰Ar/³⁹Ar sanidine age. Bayesian eruption age modeling (BEAM) of new LCY ²³⁸U-²³⁰Th disequilibrium dates consistently yields ages younger than previous estimates based on overdispersed zircon and plagioclase dates. Regardless of the prescribed zircon age distribution, BEAM results indicate the youngest zircon crystallization at ca. 88–76 ka, supporting the established ZDD eruption age of 75 ± 2 ka for LCY. This refined chronology provides insights into the Atitlán caldera volcanic activity, enhances hazard assessment and understanding of regional geological evolution, and highlights the pitfalls of Bayesian age modeling when integrating different chronometers.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 3","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011953","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143629845","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrous Regions of the Mantle Transition Zone Lie Beneath Areas of Continental Intraplate Volcanism","authors":"Helene Wang,&nbsp;Valentina Magni,&nbsp;Clinton P. Conrad,&nbsp;Mathew Domeier","doi":"10.1029/2024GC011901","DOIUrl":"https://doi.org/10.1029/2024GC011901","url":null,"abstract":"<p>Great volumes of water are carried downward into the mantle transition zone (MTZ, 410–670 km depth) by subducting slabs. If this water is later drawn upward, the resulting mantle melting may generate continental intraplate volcanism (IPV). Despite water's importance, its amount and spatial distribution within the MTZ, and its impact on IPV, are poorly constrained. Here we use plate tectonic reconstructions to estimate the rates and positions of water injection into the MTZ by subducted slabs during the past 400 Myr. This allows us to construct global maps of heterogeneous MTZ hydration, which we then compare to IPV eruption locations from the past 200 Myr. We detect a statistically significant correlation between wet MTZ regions and IPV locations at the surface, but only if slabs sink faster than 1 cm/yr, water remains stored in the MTZ for periods of 30–100 Myr, and IPV eruptions occur 10–30 Myr later. We find that 42%–68% of continental IPV is underlain by wet MTZ, with greater fractions associated with longer MTZ residence time. Hydrous underpinning of continental IPV was highest during the Jurassic, when more extensive slab interaction with the MTZ hydrated a wider area of the MTZ. Since the Cretaceous, continents have been moving over the wet MTZ, increasing IPV possibilities. MTZ regions near the northern Pacific, southern Africa, and western Europe have remained dry by avoiding wet slabs. We suggest that subducted water shapes global patterns of intraplate volcanism, with hydrous upwellings rising from the MTZ to generate continental IPV above wet MTZ regions.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 3","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011901","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143612556","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Zircon Solubility, Metamict ZrSiO4 Replacement, and Hydrothermal Zircon Formation at Upper Crustal Pressures","authors":"John C. Ayers,&nbsp;Chen Zhu","doi":"10.1029/2024GC011925","DOIUrl":"https://doi.org/10.1029/2024GC011925","url":null,"abstract":"<p>Stable and inert under most conditions, zircon can be dissolved and precipitated by aqueous fluids in the upper crust. Geochemical models using currently available thermodynamic properties for Zr aqueous species at 0.2 GPa predict that zircon solubility increases with temperature from 400 to 900°C in fluids saturated with quartz or baddeleyite. Zircon solubility is low in near-neutral pH fluids and enhanced in acidic and alkaline fluids. Adding NaOH and to a lesser extent NaF to the solution significantly increases the solution pH values and Zr concentrations at zircon saturation. Modeled Zr concentrations are often orders of magnitude different from zircon solubilities measured experimentally under similar conditions. Metamict (amorphous) ZrSiO₄ is more soluble than crystalline zircon and is replaced through a coupled dissolution-precipitation process. Reaction path kinetics models were constructed to simulate experiments described in the literature and extract rate constants for replacement of metamict ZrSiO₄. Replacement is rate limited by zircon precipitation and is nearly complete after 1 week when fluid is present at 600°C, with the rate of replacement increasing with temperature. In a closed system, hydrothermal zircon may form by replacement of radiation-damaged zircon but not fully crystalline zircon. Replacement of metamict ZrSiO₄ forms characteristic porosity. Geochemical models identify the conditions that promote zircon solubility, metamict ZrSiO₄ replacement, and the formation of hydrothermal zircon, and provide constraints on the interpretation of zircon U-Pb dates of hydrothermal events.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 3","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011925","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143595467","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Combining 3-D Probabilistic Kinematic Modeling With Thermal Resetting Measurements: An Approach to Reduce Uncertainty in Exhumation Histories","authors":"Sofia Brisson,&nbsp;Denise Degen,&nbsp;David Nathan,&nbsp;Florian Wellmann,&nbsp;Christoph von Hagke","doi":"10.1029/2024GC011815","DOIUrl":"https://doi.org/10.1029/2024GC011815","url":null,"abstract":"<p>To understand the exhumation history of orogens and their fold-thrust belts, it is important to accurately reconstruct their time-temperature evolution. This is often done by employing thermokinematic models. One problem of current approaches is that they are limited in prescribing geometric constraints only as far as they affect transient thermal conditions. This often results in 2-D plane strain assumptions, and a simple treatment of structural and kinematic uncertainties. In this work, we combine 3-D kinematic forward modeling with a random sampling approach to automatically generate an ensemble of kinematic models in the range of assigned geometric uncertainties. Using Markov Chain Monte Carlo, each randomly generated model is assessed regarding how well it fits the available paleo-depth data taken from low-temperature thermochronology. The resulting, more robust model can then be used to re-interpret the thermal resetting data. We first apply this method to synthetic experiments with variable structural complexity and sample uncertainties, and later to the Alpine fold-thrust belt, the Subalpine Molasse. Results show that it is possible to use thermochronological data to make predictions about exhumation, which can be translated into likelihood functions to obtain the range of 3-D kinematic forward models explaining the data. Though the method performs well for the synthetic models, additional thermochronological parameters may need to be considered to improve the inversion results for structurally complex settings. The method is useful, however, to study alternative mechanisms of exhumation for the thermochronological samples that are not respected by the modeling, even when uncertainty is considered.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 3","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC011815","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143595436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Machine Learning Approach to Single Garnet Geothermometry and Application to Tracing the Fingerprint of Superdeep Diamonds","authors":"Qiwei Zhang,&nbsp;Matthew F. Hardman,&nbsp;Thomas Stachel,&nbsp;Ingrid Chinn,&nbsp;Michael Seller,&nbsp;Bruce Kjarsgaard,&nbsp;D. Graham Pearson","doi":"10.1029/2024GC012124","DOIUrl":"https://doi.org/10.1029/2024GC012124","url":null,"abstract":"<p>Estimating the equilibration temperatures of mantle-derived garnets is crucial for assessing the diamond potential of kimberlites. Traditional garnet geothermometers require co-existing mineral data or costly trace element analysis, limiting their practical use. As an alternative approach, based on the major and minor element composition of garnet alone, we first re-calibrated an Mn-in-garnet thermometer using a newly compiled data set of garnets from well-equilibrated peridotitic xenoliths with well-constrained pressure-temperature (P-T) conditions. The re-calibrated Mn-in-garnet thermometer, however, is only of intermediate accuracy, with a relatively large discrepancy relative to the most reliable multi-phase thermometry, indicated by a high root mean square error value (RMSE = 79°C) across a temperature range from 900 to 1,400°C. In a second improve approach, we developed a new machine learning (ML)-based garnet thermometer that demonstrated superior performance, achieving significantly better accuracy and reduced discrepancies (average RMSE = 61°C). The ML-based garnet thermometer outperforms the Mn-in-garnet thermometer because it considers not only MnO but also other major and minor elements, particularly TiO₂, revealed by the ML model to be critical for accurate prediction of garnet temperatures. Applying the ML-based thermometer to garnet xenocrysts from kimberlites on the Slave and Kaapvaal cratons reveals that high numbers of sublithospheric (superdeep) diamonds are associated with significantly higher proportions of high-T (&gt;1,200°C) high-Ti garnets, compared to kimberlites in which superdeep diamonds are either few or absent. This finding indicates that a number of kimberlites, not currently identified as containing superdeep diamond populations, are promising hosts of such diamonds.</p>","PeriodicalId":50422,"journal":{"name":"Geochemistry Geophysics Geosystems","volume":"26 3","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GC012124","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143571212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}