Geochimica et Cosmochimica Acta最新文献

{"title":"Electron transfer at birnessite/organic compound interfaces: mechanism, regulation, and two-stage kinetic discrepancy in structural rearrangement and decomposition","authors":"Huan Ye , Zhaoyang Hu , Rongzhang Yin , Teak D. Boyko , Yunpeng Liu , Yanzhang Li , Chunjiang Li , Anhuai Lu , Yan Li","doi":"10.1016/j.gca.2024.10.009","DOIUrl":"10.1016/j.gca.2024.10.009","url":null,"abstract":"<div><div>Electron transfer between birnessite and organic compounds (OC) plays a dominant role in the coupling cycle of manganese (Mn) and carbon across diverse environmental settings. While previous studies have extensively investigated individual processes of interface Mn reduction, surface Mn<sup>2+</sup> adsorption, and surface-to-interior electron transfer, the dynamic interplay among these reactions and the mechanisms regulating subtle changes in surface and interior Mn states remained poorly understood. Additionally, existing models have not adequately captured electron transfer kinetics in multivariable systems involving pH, Mn<sup>2+</sup> concentration, electron donor type, etc. In this study, we investigated the reduction kinetics of birnessite under the influence of multiple environmental variables by employing three typical OC: formic acid (HCOOH), formaldehyde (HCHO), and methanol (CH<sub>3</sub>OH). Time-series analysis revealed kinetic discrepancy and time lag between the alteration of the average Mn oxidation state (AMOS) within the solid and the release of Mn<sup>2+</sup> from the reductive dissolution of birnessite, indicating a two-stage electron transfer mechanism occurring at the interface between birnessite and OC. X-ray absorption fine structure spectra revealed a rapid increase in corner-sharing MnO<sub>6</sub> octahedra and a decline in AMOS during the initial stage, followed by a slight decrease in AMOS and substantial mineral dissolution to release Mn<sup>2+</sup> in the subsequent stage. The transition point between the two stages is primarily influenced by the concentration of surface Mn<sup>II</sup> under pH regulation, as confirmed by soft X-ray absorption spectroscopy and density functional theory calculations. Based on these findings, the adsorption equilibrium and electron transfer rate were modeled by a machine learning framework (JAX), which is influenced by three main factors: pH, Mn<sup>2+</sup> concentration, and OC types. The adsorption equilibrium constant for HCHO was one order of magnitude lower than for HCOOH, yet displayed a faster reaction rate due to higher electron transfer rates. Competitive adsorption of OC and Mn<sup>2+</sup> on reactive sites was influenced by both pH and Mn<sup>2+</sup> concentrations. Combining these parameters, we created a 3D surface plot that comprehensively considered the interplay between different elementary reactions, including competitive adsorption and redox reaction rates, thereby visualizing the kinetic regulation mechanisms in multivariable systems. Furthermore, a comprehensive rate equation for the reduction of birnessite by OC was developed to predict its behavior in natural settings. With an electron storage capacity of 2.7×10<sup>23</sup> electrons/mol Mn before structural decomposition or dissolution, we propose that birnessite can act as a geobattery driving cryptic elemental biogeochemical cycling. Our findings also suggest that the highly reversible redox","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"388 ","pages":"Pages 253-267"},"PeriodicalIF":4.5,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142763014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Citation for the 2024 F. W. Clarke Award to Jihua Hao","authors":"Dimitri A. Sverjensky","doi":"10.1016/j.gca.2024.10.031","DOIUrl":"10.1016/j.gca.2024.10.031","url":null,"abstract":"","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"388 ","pages":"Page 315"},"PeriodicalIF":4.5,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coupled effects of iron (hydr)oxides and clay minerals on the heterogeneous oxidation of aqueous Mn(II) and crystallization of manganese (hydr)oxides","authors":"Yixuan Yang ,&nbsp;Qingze Chen ,&nbsp;Jing Liu ,&nbsp;Jieqi Xing ,&nbsp;Yiping Yang ,&nbsp;Runliang Zhu ,&nbsp;Hongping He ,&nbsp;Michael F. Hochella Jr.","doi":"10.1016/j.gca.2024.09.034","DOIUrl":"10.1016/j.gca.2024.09.034","url":null,"abstract":"<div><div>The formation of nanominerals and mineral nanoparticles (NMMNs) has drawn broad attention due to their high reactivity and omnipresence in the environment. While the heterogeneous formation of NMMNs on surfaces of various minerals has been extensively studied, there is limited understanding of how mineral heteroaggregates influence this process. In this study, we investigated how heteroaggregates of iron (hydr)oxides and clay minerals affect the heterogeneous oxidation of aqueous Mn(II) and crystallization of manganese (hydr)oxides (MnO_x). Our results revealed that iron (hydr)oxides (ferrihydrite) and clay minerals (kaolinite or montmorillonite) in heteroaggregates exerted coupled effects on these processes, dictating the distribution of Mn and the morphology of MnO_x. Specifically, ferrihydrite catalyzed gradual oxidative removal of Mn(II) and triggered MnO_x nucleation; in contrast, kaolinite/montmorillonite rapidly adsorbed Mn(II) but hardly catalyzed its oxidation. These reactions collectively resulted in fast adsorption and gradual oxidation of Mn(II) on the heteroaggregates. Further, MnO_x nanoparticles formed on ferrihydrite surfaces migrated to kaolinite/montmorillonite surfaces, leading to interactions between MnO_x and various component minerals within the heteroaggregates. This significantly altered the subsequent growth pathways and the eventual morphology of MnO_x. Consequently, while MnO_x nanoparticles in the ferrihydrite-only system aggregated freely and formed well-extended nanowires, those in the ferrihydrite-kaolinite system predominantly became short nanorods due to the immobilization by kaolinite surfaces; in the ferrihydrite-montmorillonite system, considerable MnO_x nanoparticles attached to montmorillonite surfaces due to strong electrostatic attraction, and subsequently grew into blocky particles via particle attachment. These findings illustrate that surface reactivities of heteroaggregated ferrihydrite and kaolinite/montmorillonite are coupled when they interact with aqueous Mn(II) or MnO_x. Our work exemplifies, for the first time, the cooperation between surfaces of various minerals during the heterogeneous formation of NMMNs. Findings from this study also enhance our understanding of MnO_x formation on surfaces with diverse atomic structures, and contribute to the knowledge of Mn cycling in the environment.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"388 ","pages":"Pages 167-181"},"PeriodicalIF":4.5,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673693","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Manganese oxidation states and availability in forest weathering profiles of contrasting climate","authors":"Zhuojun Zhang ,&nbsp;Peng Yang ,&nbsp;Ke Wen ,&nbsp;Hai-Ruo Mao ,&nbsp;Zhiqi Zhao ,&nbsp;Congqiang Liu ,&nbsp;Qing Zhu ,&nbsp;Mengqiang Zhu","doi":"10.1016/j.gca.2024.10.006","DOIUrl":"10.1016/j.gca.2024.10.006","url":null,"abstract":"<div><div>The abundance and oxidation states (II, III and IV) of manganese (Mn) in a weathering profile encompassing both the soil layers (A and B horizons) and the underlaid saprolite (C horizons) determine the availability of Mn as a plant nutrient and regulate its role in cycles of other elements in Earth’s critical zone. However, it remains unclear how the abundance and oxidation states vary with depth under different climates, and how the soil forming processes and soil properties control the variations. We examined four forest granite weathering profiles developed under climates ranging from temperate to tropical climate. Regardless of climate types, all four profiles showed similar vertical variation patterns of Mn concentration and oxidation states. The major features of the patterns can be understood from the perspective of soil forming processes and soil properties. Climate affected the Mn oxidation states in the fine fraction (&lt; 2 mm; i.e., the soil fraction) of the poorly weathered saprolite by controlling the weathering degree of Mn-bearing primary minerals. The weathering released Mn(II) and Mn(III) in the primary minerals to the circumneutral environment where it was subsequently oxidized by O₂. In contrast, climate affected the Mn oxidation states in the soil layers poor in parent materials largely by controlling soil redox conditions and pH because most of the Mn in soils was reactive. As the climate became warmer/wetter, the weathering intensified and soils became more reducing and acidic, resulting in more reduced Mn in the soil layers but more oxidized Mn in the fine fraction of saprolite. Moreover, relative to Mn(II) and Mn(IV), Mn(III) preferentially accumulated in the subsoil (B horizons), likely as Mn(III) oxyhydroxides in the colder and drier climates, and as a substitute ion in well-crystallized Fe(III) oxides in the warmer and wetter climates. These findings improve our understanding of Mn availability and cycling and its role in biogeochemical cycles of other elements in Earth’s critical zone.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"388 ","pages":"Pages 221-235"},"PeriodicalIF":4.5,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673572","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bio-mediated enhancement of supergene copper mineralization: Evidence from Cu isotope geochemistry","authors":"J. Javier Rey-Samper ,&nbsp;Ryan Mathur ,&nbsp;Fernando Tornos","doi":"10.1016/j.gca.2024.10.014","DOIUrl":"10.1016/j.gca.2024.10.014","url":null,"abstract":"<div><div>The relationship between microbial activity and the supergene modification of ore systems has been a major subject of debate. Here, we present isotopic evidence of microbial-driven secondary copper mineralization in the active cementation zone of the Las Cruces deposit, a volcanogenic massive sulfide deposit located in Iberian Pyrite Belt, Spain. Copper isotopic data show that the lower isotopic ratios (δ⁶⁵Cu ≈ −9.2 ± 0.11 ‰, the lowest value measured worldwide in a supergene environment) are found in the upper part of the cementation zone, the same zone where the maximum copper grades are found and where there is direct evidence of extremophilic microbial activity. There is a tendency towards higher values downwards through the cementation zone (−9.2 ± 0.11 ‰ to + 1.67 ± 0.11 ‰ δ⁶⁵Cu) and upwards into the former Cu-depleted gossan that originally capped the cementation zone (−7.79 ± 0.11 ‰ to −1.32 ± 0.11 ‰ δ⁶⁵Cu). As microbes preferentially sequester the lighter isotope when incorporating intracellular Cu, this distribution indicates that microbes played a major role in the formation of the high-grade zones. Water arrives to the deposit enriched in isotopically heavy copper, likely because it has leached other ore bodies upstream. δ⁶⁵Cu values of water currently flowing into the system are remarkably more positive than those in the ore, indicating that microbial activity is a major cause of copper isotope fractionation. At least half of the copper transported by the incoming waters remains within the ore body. Our best interpretation is that the large and high-grade cementation zone at Las Cruces is of biogenic origin, and that the primary mineralization acted as a trap for copper transported by groundwater, leading to the formation of an exotic mineralization distal to sub-eroded massive sulfides located upstream.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"388 ","pages":"Pages 283-293"},"PeriodicalIF":4.5,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Foraminiferal denitrification and deep bioirrigation influence benthic biogeochemical cycling in a seasonally hypoxic fjord","authors":"Subhadeep Rakshit ,&nbsp;Nicolaas Glock ,&nbsp;Andrew W. Dale ,&nbsp;Maria M.L. Armstrong ,&nbsp;Florian Scholz ,&nbsp;Andrè Mutzberg ,&nbsp;Christopher K. Algar","doi":"10.1016/j.gca.2024.10.010","DOIUrl":"10.1016/j.gca.2024.10.010","url":null,"abstract":"<div><div>Benthic macro- and micro-biota often play significant roles in controlling the biogeochemical dynamics in sediments. Their activity can be influenced by oxygen availability and impacted by the rise in global hypoxia in coastal regions over the last decades. To understand how these organisms interact with coastal hypoxia and influence sediment biogeochemistry, we undertook a study of early diagenesis in Bedford Basin, a seasonally hypoxic fjord on the West Atlantic coast in Nova Scotia, Canada, using a combination of observations and reaction-transport modeling. We observed that the seafloor was a source of ammonium and sink of nitrate with average fluxes of 2.2 ± 1.8 and −0.9 ± 0.7 mmol m⁻² d⁻¹ respectively. The diffusive oxygen uptake was 14 ± 4.6 mmol m⁻² d⁻¹ and the total organic carbon content in collected sediment cores was 5–7 % with a C/N ratio of ∼10. The pyrite content increased steadily from 0.5 wt% Fe at surface to ∼2 wt% Fe at 20 cm depth. Hydrogen sulfide was negligible down to 25 cm depth most of the time. The sediment was inhabited by tube-forming polychaete <em>Spiochaetopterus</em> sp. that formed tubes up to ∼30 cm in length. The living foraminiferal assemblage in the top 5 cm sediment was found to be dominated (&gt;85 %) by nitrate-storing and denitrifying benthic foraminifera <em>Stainforthia fusiformis</em>. These observations were used to develop and constrain a biogeochemical reaction-transport model. The model results suggest that the observed decrease in porewater concentrations of ammonium and dissolved inorganic carbon below 5 cm depth, was due to deep bioirrigation by tubeworms, accounting for almost 50 % of the benthic efflux. The model further revealed that the deep bioirrigation along with bioturbation and iron cycling prevented accumulation of free sulfide in the top 25 cm sediment despite oxygen penetration depths of ∼1 mm. Modelled organic carbon and nitrogen deposition was 25.2 and 2.9 mmol m⁻² d⁻¹ with burial efficiencies of 23 % and 17 %, respectively. The model indicated a total denitrification rate of 1.3 mmol N m⁻² d⁻¹ that was largely (∼70 %) driven by benthic foraminifera. This study reports the first evidence of foraminiferal denitrification in western Atlantic coastal sediments, and suggests that eukaryote mediated denitrification is an important driver of sediment N-loss in seasonally hypoxic environments, a process that has been traditionally assumed to be carried out by prokaryotic microbes.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"388 ","pages":"Pages 268-282"},"PeriodicalIF":4.5,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143098819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Stable carbon isotope ratios of pristine carbohydrates preserved within nannofossil calcite","authors":"Harry-Luke Oliver McClelland ,&nbsp;Renee B.Y. Lee ,&nbsp;Ann Pearson ,&nbsp;Rosalind E.M. Rickaby","doi":"10.1016/j.gca.2024.09.007","DOIUrl":"10.1016/j.gca.2024.09.007","url":null,"abstract":"<div><div>The geochemical characterization of phytoplankton-derived organic compounds found in marine sediments has been widely used to reconstruct atmospheric pCO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> throughout the Cenozoic. This is possible owing to a well-established relationship between the carbon isotope ratios of phytoplankton biomass and CO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> concentration in the ambient seawater. An ideal molecular target for such proxy reconstructions would be degradation resistant on geologic timescales and unambiguously associated with known, experimentally tractable, organisms, so that species-specific models can be developed, calibrated, and applied to appropriate material. However, existing organic matter targets do not meet these criteria, primarily owing to ambiguity in the source species of recalcitrant compounds in deep time. Here we explore the potential of a novel organic carbon target for isotopic analysis: acidic polysaccharides extracted from the calcite plates (coccoliths) that are produced by all calcifying haptophytes. Carbohydrates are usually rapidly remineralized in sediments, but coccolith-associated polysaccharides (CAPs) are mechanically protected from diagenesis within the coccolith calcite lattice. Coccoliths can be taxonomically separated by size and identified, often to species level, prior to CAP extraction, providing a species-specific record. Coccolith morphology and composition are important additional sources of information, which are then unambiguously associated with the extracted CAPs. We found that carbon isotope ratios of CAPs changed in response to the environmental changes associated with a glacial cycle, which we attribute to temperature-driven changes in average growth rate. Once the underlying biosynthetic processes and the associated isotope effects are better understood, this archive of pristine organic matter has the potential to provide insight into phytoplankton growth rates and atmospheric pCO<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span> far beyond the Cenozoic, to when the first coccolithophores inhabited the surface ocean over 200 million years ago.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"388 ","pages":"Pages 143-153"},"PeriodicalIF":4.5,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142245681","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"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":"Citation for the 2024 Goldschmidt to Donald E. Canfield","authors":"Timothy W. Lyons","doi":"10.1016/j.gca.2024.10.029","DOIUrl":"10.1016/j.gca.2024.10.029","url":null,"abstract":"","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"388 ","pages":"Pages 307-308"},"PeriodicalIF":4.5,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673570","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Citation for the 2024C. C. Patterson Award to Satoshi Utsunomiya","authors":"Rodney C. Ewing","doi":"10.1016/j.gca.2024.10.033","DOIUrl":"10.1016/j.gca.2024.10.033","url":null,"abstract":"","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"388 ","pages":"Page 317"},"PeriodicalIF":4.5,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673616","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Molybdenum isotope behavior during subduction zone metamorphism","authors":"Cassidy J. Stegner ,&nbsp;Richard M. Gaschnig ,&nbsp;Samuel Marshall ,&nbsp;Shelby T. Rader ,&nbsp;Gray E. Bebout ,&nbsp;Sarah C. Penniston-Dorland","doi":"10.1016/j.gca.2024.10.016","DOIUrl":"10.1016/j.gca.2024.10.016","url":null,"abstract":"<div><div>The molybdenum (Mo) isotope composition (defined as δ⁹⁸Mo measured per mil relative to NIST-3134) of many modern arc systems and the upper continental crust is heavier than the mantle and most subducting slab lithologies. This observation has led to a model whereby fluids leaving the slab transfer isotopically heavy Mo preferentially to the mantle wedge, leaving the residual slab isotopically lighter. We explore this model via an Mo isotope study of the metasedimentary and mélange lithologies of the Catalina Schist in California. These rocks record subduction zone metamorphism over a wide range of high-pressure/low-to-medium temperature conditions.</div><div>Mo isotope compositions of the metasedimentary rocks decrease with increasing metamorphic grade, from a δ⁹⁸Mo_mean of −0.04 ± 0.13 ‰ (1σ, n = 3) for the lawsonite albite facies to −0.38 ± 0.07 ‰ (1σ, n = 5) for the epidote–amphibolite facies. The highest grade [amphibolite facies] samples show a slight uptick in δ⁹⁸Mo values, with a mean of −0.19± 0.14 ‰ (1σ, n = 4). When coupled with major and trace element variations, the changes in δ⁹⁸Mo appear to reflect metamorphic effects rather than sedimentary source rock heterogeneity. The positive relationship between δ⁹⁸Mo and [Mo] and negative relationship with Ce/Mo argue for progressive loss of Mo with isotope fractionation during increasing P-T conditions; the reversal of this trend, seen in the increase in δ⁹⁸Mo between the epidote amphibolite and amphibolite facies may reflect a subsequent partial re-fertilization by fluids carrying isotopically heavy Mo. δ⁹⁸Mo values in the mélange across all grades are highly variable, ranging from −1.75 to −0.19‰, consistent with large scale mobilization of Mo with isotope fractionation. A metasomatized amphibolite block and reaction rind show similar light isotope compositions and signs of Mo depletion and transport. Together these three whole-rock data sets demonstrate pervasive open system behavior and mobility of Mo in the Catalina Schist. LA-ICP-MS Mo measurement of minerals in the differing metasedimentary metamorphic grades indicates that Fe oxides and/or hydroxides, titanite, rutile, and epidote are important reservoirs of Mo but when comparing mineral Mo content and modal abundance to whole-rock Mo concentrations, several samples were found to have “missing Mo”, something that has been observed in other Mo inventory studies. We attribute this to sample heterogeneity between the thin section and whole-rock powder scales.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"388 ","pages":"Pages 294-306"},"PeriodicalIF":4.5,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673653","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}