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Calcium Diffusion in Enstatite, with Application to Closure Temperature of the Ca-in-opx Thermometer Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-25 D.J. Cherniak, Y. Liang
Chemical diffusion of Ca has been characterized in natural enstatite under buffered conditions (IW, NNO) and in air. Experiments were conducted using synthesized powder sources, with Ca diffusion profiles measured with Rutherford Backscattering Spectrometry. A variety of sources of diffusant were used to investigate the effects of silica activity and Ca concentration on diffusion. Calcium diffusion
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Oxidative Dissolution of Orpiment and Realgar Induced by Dissolved and Solid Mn(III) Species Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-25 Xingxing Wang, Jiajia Wang, Xiaohan Lu, Ming Zhou, Qihuang Wang, Zezhen Pan, Naresh Kumar, Mengqiang Zhu, Zimeng Wang
A thorough understanding of the complex redox coupling among manganese, arsenic, sulfur and oxygen in subsurface environments is still obscured by their metastable intermediate valances and speciation. Arsenic sulfide minerals may be disturbed by natural or anthropogenic activities, and encounter oxidants such as oxygen and reactive trivalent Mn species, and how these abiotic interactions impact the
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Preface to Base, Precious and Critical Metals in Fluid-Mineral Interactions Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-25 Yuan Mei, Fang Xia, Weihua Liu, Zoltán Zajacz, Artas Migdisov, Anthony Wiliams-Jones
Abstract not available
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Whole-rock geochemistry and zircon O-Hf isotope compositions of ca. 2.35 Ga strongly peraluminous granites: Implications for increase in zircon δ18O values during the Paleoproterozoic Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-25 Shi-Wen Xie, Fang Wang, Claire E. Bucholz, Fu-Lai Liu, Pei-Zhi Wang, Ze-Min Bao, Dun-Yi Liu
Zircon oxygen isotope ratios have been used to trace the incorporation of sedimentary rocks into magmas. The dramatic increase in maximum zircon δ18O values in the Paleoproterozoic observed in global databases coincides with changes in surface environments (e.g., the rise of subaerial and oxidative weathering), implying a connection between elevated zircon δ18O and these changes. Zircon δ18O between
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Soil potassium isotope composition during four million years of ecosystem development in Hawai‘i Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-24 Wenshuai Li, Xiao-Ming Liu, Kun Wang, Yoshio Takahashi, Yongfeng Hu, Oliver A. Chadwick
We combine spectroscopic and geochemical approaches to interpret the fate of potassium (K) during forest soil development along a 4-million-year chronosequence sampled from relatively undisturbed rainforests in Hawai‘i. Potassium derived from weathering of lava is dominant in the youngest site (0.3 ky), but its contribution to the soil K budget declines as weathering progresses. Sites older than 0
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Chemical weathering signatures at Mt. Achernar, Central Transantarctic Mountains II: Surface exposed sediments Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-24 Joseph A Graly, Kathy J Licht, Nicole A Bader, Christine M Kassab, David L Bish, Michael R Kaplan
Mt Achernar Moraine is a high altitude, high latitude blue ice moraine where typical conditions preclude the presence of liquid water. Cosmogenic and salt accumulation dating indicate that the moraine’s surface is progressively older away from the active ice margin, with surface exposure ages up to 1 Ma. We analyze the chemical and mineralogical transformations in the <63 µm fraction along transects
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Hydrothermal activity and associated subsurface processes at Niuatahi rear-arc volcano, North East Lau Basin, SW Pacific: Implications from trace elements and stable isotope systematics in vent fluids Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-23 Lukas Klose, Charlotte Kleint, Wolfgang Bach, Alexander Diehl, Frederike Wilckens, Christian Peters, Harald Strauss, Karsten Haase, Andrea Koschinsky
Hydrothermal activity is abundant in the area between the North Eastern Lau Spreading Center and the Tofua intra-oceanic island arc with multiple active sites in the rear-arc at the Mata and Niuatahi volcanoes. We report geochemical data for high-temperature vent fluids sampled from within the caldera of Niuatahi volcano. Hydrothermal fluids were sampled from three vent sites: South Central, Southwestern
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The Dynamic Formation Process of the CB Chondrite Gujba Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-23 Piers Koefoed, Olga Pravdivtseva, Ryan Ogliore, Yun Jiang, Katharina Lodders, Mason Neuman, Kun Wang
The many unique characteristics of CB chondrites have resulted in the impact hypothesis becoming the favoured model for their formation. Here, we further investigate the formation mechanisms of CB chondrites by analysing the elemental and K isotope compositions of chondrules and bulk fractions from the CBa chondrite Gujba. Similar to previous work, the refractory element ratios in the Gujba chondrules
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Erratum to “The contribution of hydrodynamic processes to calcite dissolution rates and rate spectra” [Geochim. Cosmochim. Acta 307 (2021) 338–350] Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-23 Priyanka Agrawal, Till Bollermann, Amir Raoof, Oleg Iliev, Cornelius Fischer, Mariëtte Wolthers
Abstract not available
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Diffusional isotope fractionation of singly and doubly substituted isotopologues of H2, N2 and O2 during air-water gas transfer Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-23 Xiaobin Cao
Air-water gas transfer largely influences the geochemical and biogeochemical cycles of essential atmospheric components (e.g. O2 and CO2), in which gas molecular diffusion in water is recognized as the rate limiting step. Isotope compositions in these gas molecules are useful tools to quantify this mass transfer process, in which diffusional isotope fractionation factors (i.e. αdiff) are the key intrinsic
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Nickel isotopic composition of the upper continental crust Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-21 Guangliang Wu, Jian-Ming Zhu, Xiangli Wang, Thomas M. Johnson, Yongsheng He, Fang Huang, Lian-Xun Wang, Shao-Cong Lai
Establishing the nickel (Ni) isotopic composition of the upper continental crust (UCC) is crucial for using the Ni isotope system to trace biogeochemical processes and understand crust-mantle interactions. This study reports the Ni isotopic composition of eighty-four well-characterized upper crustal samples, including granites, granodiorites, tonalite-trondhjemite-granodiorite (TTG), loess, river sediments
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Molybdenum isotopic constraint from Java on slab inputs to subduction zone magmatism Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-20 Yang Yu, Xiao-Long Huang, Sun-Lin Chung, Jie Li, Yu-Ming Lai, Iwan Setiawan, Min Sun
Molybdenum isotope is a diagnostic tracer for crustal and mantle components in arc magmatism. However, the mechanism of Mo isotopic variation in arc magmas is still debated, e.g., input of different subduction components into the mantle wedge versus isotopic fractionation during dehydration of subducted slab. Here we present whole-rock Mo-Sr-Nd-Hf-Pb isotopic data for the Continental Arc Basalt (CAB)
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New insights into Mn2+ and Mg2+ inhibition of calcite growth Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-20 Jennifer V. Mills, Holly A. Barnhart, Donald J. DePaolo, Laura N. Lammers
Impurity ion and isotope partitioning into carbonate minerals provide a window into the molecular processes occurring at the fluid-mineral interface during crystal growth. Here, we employ calcium isotope fractionation together with process-based modeling to elucidate the mechanisms by which two divalent cations with starkly contrasting compatibility, magnesium and manganese, inhibit calcite growth
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Thermodynamic modelling of perchlorate/chloride and perchlorate/chlorate deliquescence at Mars-relevant temperatures Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-20 Vincent F. Chevrier, Alec Fitting, Amira Elsenousy, Edgard G. Rivera-Valentín
Perchlorate (ClO4-) salts were discovered on Mars and are known to absorb water vapor from the atmosphere and deliquesce into the aqueous phase. Other species such as chlorides (Cl-) and chlorates (ClO3-) were also identified; these species can affect the deliquescence of perchlorates. Here we generate phase diagrams of perchlorate / chloride and perchlorate / chlorate binary mixtures for K, Na, Mg
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Lithium isotope fractionation during magmatic differentiation and hydrothermal processes in post–collisional adakitic rocks Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-20 Heng-Ci Tian, Shi-Hong Tian, Zeng-Qian Hou, Zhi-Ming Yang, Yuanchuan Zheng
To investigate the behavior of Li isotopes during magmatic differentiation and the petrogenesis of Cu-bearing ore deposits, a suite of post-collisional adakitic rocks from Qulong region, southern Tibet, was studied. Their lithologies range from diorite through granodiorite to granite porphyry with the latter containing giant Cu deposits. Detailed evidence of field observation and geochemical signature
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Earliest Evidence of Nebular Shock Waves Recorded in a Calcium-Aluminum-rich Inclusion Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-20 Prajkta Mane, Shawn Wallace, Maitrayee Bose, Paul Wallace, Meenakshi Wadhwa, Juliane Weber, Thomas J. Zega
Calcium-aluminum-rich inclusions (CAIs) and chondrules are among the most predominant chondritic components contained within primitive meteorites. As CAIs are the first solids to form in the solar nebula, they contain a record of its earliest chemical and physical processes. Here we combine electron backscatter diffraction (EBSD) and 26Al-26Mg chronology techniques to determine the crystallographic
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Carbon in the deep upper mantle and transition zone under reduced conditions: insights from high-pressure experiments and machine learning models Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-20 Jiali Lei, Sayan Sen, Yuan Li, J. Zhang Zhou
The storage of carbon in Earth’s mantle is an important consideration within the framework of the deep carbon cycle. In the deep (>250 km depth) reduced mantle, carbon storage mechanisms differ greatly from those in the oxidized shallow mantle. To investigate the stability of carbon-bearing phases in Earth’s deep mantle, we experimentally constrained compositional effects on phase stability in the
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16O-rich anhydrous silicates in CI chondrites: Implications for the nature and dynamics of dust in the solar accretion disk Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-20 Gatien L.F. Morin, Yves Marrocchi, Johan Villeneuve, Emmanuel Jacquet
CI chondrites have nonvolatile chemical compositions closely resembling that of the Sun’s photosphere and are thus considered to have the most primitive compositions of all known solar system materials. They have, however, experienced pervasive parent-body alteration processes that transformed their primary constituents, obscuring the nature and origin of primordial CI dust. We used in-situ quantitative
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Nickel-rich, volatile depleted iron meteorites: Relationships and formation processes Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-20 C.M. Corrigan, K. Nagashima, C. Hilton, T.J. McCoy, R.D. Ash, H.A. Tornabene, R.J. Walker, W.F. McDonough, D. Rumble
Ungrouped iron meteorites Tishomingo, Willow Grove, and Chinga, and group IVB iron meteorites, are Ni-rich. Similarities include enrichments of 10-100 × CI for some refractory siderophile elements, and equivalent depletions in more volatile siderophile elements. Superimposed on the overall enrichment/depletion trend, certain siderophile elements (P, W, Fe, Mo) are depleted relative to elements of similar
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On the nature of oxygen-isotope heterogeneity of igneous calcium-aluminum-rich inclusions in cv carbonaceous chondrites Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-20 Alexander N. Krot, Kazuhide Nagashima, Glenn J. MacPherson, Alexander A. Ulyanov
Coarse-grained igneous Ca,Al-rich inclusions (CAIs) in CV (Vigarano group) carbonaceous chondrites have typically heterogeneous O-isotope compositions with melilite, anorthite, and high-Ti (>10 wt% TiO2) fassaite being 16O-depleted (Δ17O up to ∼ −3±2‰) compared to hibonite, spinel, low-Ti (<10 wt% TiO2) fassaite, Al-diopside, and forsterite, all having close-to-solar Δ17O ∼ −24±2‰. To test a hypothesis
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Metasomatized mantle lithosphere and altered ocean crust as a fluid source for orogenic gold deposits Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-20 Hesen Zhao, Qingfei Wang, Mark A. Kendrick, David I. Groves, Tao Fan, Jun Deng
Whether auriferous hydrothermal fluid is generated during crustal metamorphism or by subcrustal processes to form orogenic gold deposits is hotly debated. Noble gas isotope and halogen abundance ratios can provide important constraints to help resolve this controversy. The Danba gold deposit is a rare example of a Jurassic age hypozonal orogenic gold deposit on the western margin of the Yangtze Craton
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Titanite links rare-element (meta-)pegmatite mineralization to Caledonian metamorphism Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-20 Haoyang Zhou, Axel Müller, Lars Eivind Augland, Magnus Kristoffersen, Muriel Erambert
The metamorphic reworking of mineralized pegmatites during orogenesis remains unclear, making the genesis and the tectonomagmatic significance of pegmatite mineralization obscure. This study demonstrates the multiple utilities of titanite geochemistry in establishing the Caledonian metamorphic evolution of the world’s largest intra-plutonic Nb-Y-F pegmatites in the Paleoproterozoic host rocks in Tysfjord
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LIP volcanism (not anoxia) tracked by Cr isotopes during Ocean Anoxic Event 2 in the proto-North Atlantic region Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-20 Lucien Nana Yobo, Chris Holmden, Alan D. Brandon, Kimberly V. Lau, James S. Eldrett, Steven Bergman
Chromium is a redox sensitive element that exhibits a large range of isotopic compositions in Earth’s surface environments because of Cr(VI)-Cr(III) transformations. This property of Cr has been exploited as a tracer of Earth’s oxygenation history using marine sediments. However, paleoredox applications using Cr are difficult to implement due to its complicated cycling, which creates spatial variability
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Synchronous solid-state diffusion, dissolution-reprecipitation, and recrystallization leading to isotopic resetting: insights from chalcopyrite replacement by copper sulfides Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-08 Alok Chaudhari, Joël Brugger, Rahul Ram, Priyadarshi Chowdhury, Barbara Etschmann, Paul Guagliardo, Fang Xia, Allan Pring, Gediminas Gervinskas, Amelia Liu, Andrew Frierdich
Reactions among minerals occur via solid-state diffusion or fluid-induced, interface-coupled dissolution-reprecipitation (ICDR). Both mechanisms can coexist under conditions where the rates of both processes are similar, depending mainly on the nature of the mineral, temperature, and fluid composition. To clarify the synergies between these reaction mechanisms, we investigated the replacement and recrystallization
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Copper mobilization via seawater-volcanic rock interactions: new experimental constraints for the formation of the iron oxide Cu-Au (IOCG) mineralization Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-07 Jianping Li, Huayong Chen, Weihua Liu, Xing Ding, Richen Zhong, Chang Yu
The involvement of modified seawater and/or basinal brine in IOCG mineralization was documented by numerous geologic studies. Still, this process remains poorly understood. In this study, we reacted seawater with andesite and basalt, the most common arc volcanic rocks, at 150 and 240 oC and water vapor-saturated pressure to assess the Cu leaching capacity and fluid evolution due to the seawater-volcanic
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Geochemical evolution of a sublacustrine hydrothermal vent system: Temporal constraints imposed by reactive transport modeling Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-07 Liheng Wang, Yanhui Dong, Amanda Tudor, Chunyang Tan, William E. Seyfried
Studies of heat and mass transport in hydrothermal systems are challenging owing to the complex feedback that exists between chemical and physical processes. Taking full advantage of the existing geochemical framework recently recognized for sublacustrine vent fluids in the Stevenson Island Deep Hole, Yellowstone Lake, here we apply a multiphase reactive transport model, coupling hydraulic and thermal
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Noble gas isotope systematics in the Canary Islands and implications for refractory mantle components Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-07 James M.D. Day
Noble gas isotope systematics of ocean island basalts (OIB) provide evidence for relatively undegassed and primitive mantle sources. These OIB sources partly derive from the deep mantle by virtue of their distinctiveness from mid-ocean ridge basalts (MORB), which dominantly sample upper mantle. New helium, neon and argon isotope data are presented for Canary Islands lavas, carbonatites and cumulate
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Comparing paleo-oxygenation proxies (benthic foraminiferal surface porosity, I/Ca, authigenic uranium) on modern sediments and the glacial Arabian Sea Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-06 Wanyi Lu, Yi Wang, Delia W. Oppo, Sune G. Nielsen, Kassandra M. Costa
Oceanic oxygen reconstructions of the last glacial period are needed to understand the mechanisms of glacial deep ocean carbon storage and to validate climate model simulations. However, existing bottom-water oxygen (BWO) reconstructions are ambiguous due to limitations of each paleo-BWO proxy. Here we present data on three proxies for BWO: benthic foraminiferal surface porosity, benthic foraminiferal
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Enhanced continental chemical weathering during the multiple early Eocene hyperthermals: New constraints from the southern Indian Ocean Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-03 Erika Tanaka, Kazutaka Yasukawa, Junichiro Ohta, Yasuhiro Kato
Multiple short-term (<105 years) global warming events (“hyperthermals”) occurred throughout the early Eocene. Chemical weathering of continental silicate rocks is considered to have played a key role in recovery from these transient global warming events via consumption of excess atmospheric CO2. However, although evidence of this negative feedback has been reported for the Paleocene–Eocene Thermal
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IVA iron meteorites as late-stage crystallization products affected by multiple collisional events Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-02 Alan E. Rubin, Bidong Zhang, Nancy L. Chabot
Although IVA irons have O- and Cr-isotopic compositions resembling those of equilibrated LL chondrites, the bulk composition of refractory elements (e.g., Re, Ir, Pt) in the IVA core appears to be significantly lower than LL. These compositional discrepancies suggest known IVA irons may be missing early crystallized samples. We hypothesize the bulk composition of the IVA core is LL-like, but current
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Testing the global significance of the sulfur isotope record of the ca. 2.0 Ga Zaonega Formation: A micro-scale S isotope investigation Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-06-02 K. Paiste, D.A. Fike, K. Kirsimäe, C. Jones, A. Lepland
The Paleoproterozoic metasedimentary rocks of the Zaonega Formation (Onega Basin, NW Russia) are important archives of inferred global environmental change following the initial oxygenation of the Earth’s atmosphere and oceans. However, the geochemical signals preserved in these exceptionally organic-and pyrite-rich metasedimentary rocks and their environmental meaning remain contested. In particular
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Water film-driven Mn (oxy)(hydr)oxide nanocoating growth on rhodochrosite Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-27 N. Tan Luong, Eugene S. Ilton, Andrey Shchukarev, Jean-François Boily
Minerals exposed to moist air stabilize thin water films that drive a score of chemical reactions of great importance to water-unsaturated terrestrial environments. In this study, we identified Mn (oxy)(hydr)oxide nanocoatings formed by the dissolution, oxidation and precipitation of Mn in oxygenated water films grown on rhodochrosite (MnCO3) microparticles. Nanocoatings that could be identified by
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Synergy of oxalic acid and sunlight triggered Cr(III)-bearing Schwertmannite transformation: Reaction mechanism, Cr and C spatial distribution and speciation on the nano scale Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-26 Qian Yao, Chuling Guo, Xiaofei Li, Xiaohu Jin, Guining Lu, Xiaoyun Yi, Weilin Huang, Zhi Dang
Cr(III)-bearing iron minerals are widely present in acid mine drainage (AMD)-contaminated areas. In the light-transmitting layer of natural systems, dissolved organic matter (DOM) can synergize with solar irradiation to transform Fe-bearing minerals, but the behavior of Cr(III) and its interfacial reaction with schwertmannite (Sch) under the combined effect of DOM and solar radiation remain unclear
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Phase separation and fluid mixing revealed by trace element signatures in pyrite from porphyry systems Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-25 Manuel Keith, Karsten M. Haase, Allan R. Chivas, Reiner Klemd
Porphyry deposits host various trace elements in economic amounts, but the hydrothermal processes causing their fractionation and enrichment are still not fully understood, but vital to target the most prospective mineralisation. We present the first micro-analytical study on the trace element composition of pyrite from the Koloula Cu-Au porphyry in the young and thin (<25 km) Solomon Island arc. A
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Formation and decomposition of vacancy-rich clinopyroxene in a shocked eucrite: New insights for multiple impact events Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-23 Ai-Cheng Zhang, Jie-Ya Li, Jia-Ni Chen, Yuan-Yun Wen, Yan-Jun Guo, Yang Li, Naoya Sakamoto, Hisayoshi Yurimoto
Impact is a fundamental process shaping the formation and evolution of planets and asteroids. It is inevitable that some materials on the surface of planets and asteroids have been impacted for many times. However, unambiguous petrological records for multiple post-formation impact events are rarely described. Here, we report that the thin shock melt veins of the shocked eucrite Northwest Africa 8647
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Microbial Fe cycling in a simulated Precambrian ocean environment: Implications for secondary mineral (trans)formation and deposition during BIF genesis Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-21 Manuel Schad, James M. Byrne, Laurel K. ThomasArrigo, Ruben Kretzschmar, Kurt O. Konhauser, Andreas Kappler
Banded Iron Formations (BIFs) are ancient marine chemical sediments that contain various Fe-bearing minerals such as hematite (Fe2O3), magnetite (Fe3O4), siderite (FeCO3) and a variety of FeII -/FeIII-silicates. The prevailing opinion is that primary Fe(III) (oxyhydr)oxides, such as ferrihydrite (simplified formula of Fe(OH)3), were precipitated from the ocean’s photic zone by marine plankton, and
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Controls on the evolution of Cenozoic seawater chemistry Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-20 Laurence A. Coogan, Stan E. Dosso
A simple process-based model of the Li, Mg, Ca, Sr and alkalinity cycles in the ocean has been developed with the aim of better understanding the information contained in the evolution of Cenozoic seawater chemistry. In the model, changes in seawater chemistry are forced by changing climatic (temperature) and tectonic (ocean crust accretion rate and continental weatherability) conditions. These drive
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Feedbacks and non-linearity of silicate glass alteration in hyperalkaline solution studied by in operando fluid-cell Raman spectroscopy Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-18 Gerrit Müller, Moritz B.K. Fritzsche, Lars Dohmen, Thorsten Geisler
Mechanisms, feedbacks and resulting non-linearity during silicate glass alteration in a hyperalkaline carbonate solution were studied through hyperspectral Raman imaging of heated fluid-cells. Our experimental setup enabled in operando visualization and rate measurements of glass dissolution and secondary phase precipitation, complemented by spectral characterization of the phases involved and semi-quantitative
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Evidence for a primitive deep mantle component in the source of Marquesas Islands Lavas from Os isotope and highly siderophile element abundance systematics Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-18 Robert W. Nicklas, James M.D. Day, Timothy D. Jones, Paterno R. Castillo
The Marquesas islands are an age-progressive volcanic chain in French Polynesia formed by partial melting above a mantle plume. Previous studies have demonstrated the presence of an enriched mantle (EM2) endmember mixed with a high-3He/4He (up to 14.4 RA) component in Marquesas post-shield lavas. In contrast, Marquesas shield lavas sample a dilute high-μ (HIMU) type component with lower 3He/4He (∼8
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Isotopically anomalous metabolic oxygen in marine vertebrates as physiology and atmospheric proxy Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-17 Dingsu Feng, Thomas Tütken, Niklas Löffler, Gert Tröster, Andreas Pack
Triple oxygen isotope data of tooth enamel (phosphate) from 16 modern marine vertebrates (sharks, mammals) from different marine habitats are presented. Marine mammal data show a clear signature of isotopically anomalous metabolic oxygen in their bioapatite. This is related to a low flux ratio of isotopically normal drinking and food water to anomalous metabolic oxygen. Traces of anomalous metabolic
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Fractionation of Dissolved Selenium Isotopic composition during a Phytoplankton Bloom in an Estuarya Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-17 Yan Chang, Jing Zhang, Ying Wu, Shan Jiang, Xiao Na Wang, Jian Guo Qu, Han Su
Selenium (Se) isotopes have been widely used to track the Earth's redox evolution based on the assumption that terrestrial Se is faithfully transported at the land-ocean interface without nonconservative behavior or biological fractionation affecting its isotope composition. However, dissolved Se isotope behavior in estuaries is poorly constrained, which calls this assumption into question. In this
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The interaction of slab-derived silicic fluid and harzburgite – Metasomatism in the sub cratonic lithospheric mantle Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-16 Amit Meltzer, Ronit Kessel
Understanding the interaction between fluids and the depleted peridotite is essential in deciphering the geochemical and mineralogical variability of the sub-continental lithospheric mantle (SCLM). High-density fluid (HDF) inclusions trapped in diamonds during their formation in the SCLM are potential metasomatic agents. In this study, experiments were performed on a harzburgite + silicic fluid system
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Uranium isotope reconstruction of ocean deoxygenation during OAE 2 hampered by uncertainties in fractionation factors and local U-cycling Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-13 Brayden S. McDonald, Camille A. Partin, Brad Sageman, Chris Holmden
A δ238U record of changing ocean anoxia during OAE 2 is reconstructed using seawater derived U in pelagic marine sediments in the Portland #1 core in the south-central region of the Western Interior Seaway of North America. The peak negative excursion of 1.4‰ in authigenic sedimentary δ238U values is consistent with expansion of marine anoxia during the event, but the size of the shift is much larger
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Clumped isotope signatures of nitrous oxide formed by bacterial denitrification Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-13 Kristýna Kantnerová, Shohei Hattori, Sakae Toyoda, Naohiro Yoshida, Lukas Emmenegger, Stefano M. Bernasconi, Joachim Mohn
Multiply substituted isotopic species of nitrous oxide (N2O), referred to as clumped isotopes, represent a promising new tool for distinguishing production pathways of this potent greenhouse gas. This work presents the first determination of enrichment factors of N2O clumped isotopes during bacterial denitrification. Samples of N2O obtained after 1-, 3-, and 7-day incubations of a pure culture of the
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Atomistic Simulations of 40Ar Diffusion in Muscovite Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-12 Jehiel Nteme, Stéphane Scaillet, Pascal Brault, Laurent Tassan-Got
Muscovite ranks among the most commonly dated minerals in 40Ar/39Ar geochronology. Yet, its use in thermochronological reconstructions is hampered by the lack of reliable data on its 40Ar diffusional behavior. In this contribution, we investigate 40Ar lattice diffusion in muscovite at the atomic scale using Molecular Dynamics (MD) simulations combined with Nudged Elastic Band (NEB) and Transition State
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Stable Silicon Isotopes Uncover a Mineralogical Control on the Benthic Silicon Cycle in the Arctic Barents Sea Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-12 James P.J. Ward, Katharine R. Hendry, Sandra Arndt, Johan C. Faust, Felipe S. Freitas, Sian F. Henley, Jeffrey W. Krause, Christian März, Hong Chin Ng, Rebecca A. Pickering, Allyson C. Tessin
Biogeochemical cycling of silicon (Si) in the Barents Sea is under considerable pressure from physical and chemical changes, including dramatic warming and sea ice retreat, together with a decline in dissolved silicic acid (DSi) concentrations of Atlantic inflow waters since 1990. Associated changes in the community composition of phytoplankton blooms will alter the material comprising the depositional
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Monthly resolved coral barium isotopes record increased riverine inputs during the South Asian summer monsoon Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-11 Yang Yu, Ed Hathorne, Christopher Siebert, Thomas Felis, C.P. Rajendran, Martin Frank
We present a monthly resolved stable Ba isotope record (δ138Bacoral) of a young fossil coral (Porites) from the eastern side of the Andaman Islands (NE Indian Ocean), which grew prior to the 19th century. This δ138Bacoral record complements 19-years of monthly resolved Ba/Cacoral, Sr/Cacoral, U/Cacoral, δ18Ocoral and δ13Ccoral data from the same colony that can serve as a baseline of environmental
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Asteroids accretion, differentiation, and break-up in the Vesta source region: evidence from cosmochemistry of mesosiderites Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-11 S. Iannini Lelarge, L. Folco, M. Masotta, R.C. Greenwood, S.S. Russell, H.C. Bates
The cosmochemistry of meteorites provides unique clues on asteroids accretion, differentiation, collisional break-up and reassembly, processes of critical importance for understanding planet formation in the early solar system. Mesosiderites are a complex group of achondrites whose nearly 50:50 metal-silicate composition is interpreted in the literature as resulting from the mixing of core and crustal
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Triple oxygen isotope distribution in modern mammal teeth and potential geologic applications Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-11 Sophie B. Lehmann, Naomi E. Levin, Benjamin H. Passey, Huanting Hu, Thure E. Cerling, Joshua H. Miller, Laura Arppe, Emily J. Beverly, Kathryn A. Hoppe, Tyler E. Huth, Julia R. Kelson, Julie Luyt, Judith Sealy
Reconstructing water availability in terrestrial ecosystems is key to understanding past climate and landscapes, but there are few proxies for aridity that are available for use at terrestrial sites across the Cenozoic. The isotopic composition of tooth enamel is widely used as a paleoenvironmental indicator and recent work suggests the potential for using the triple oxygen isotopic composition of
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TEM analyses of in situ presolar grains from unequilibrated ordinary chondrite LL3.0 Semarkona Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-11 S.A. Singerling, L.R. Nittler, J. Barosch, E. Dobrică, A.J. Brearley, R.M. Stroud
We investigated six presolar grains from very primitive regions of the matrix in the unequilibrated ordinary chondrite Semarkona with transmission electron microscopy (TEM). These grains include one SiC, one oxide (Mg-Al spinel), and four silicates. This is the first TEM investigation of presolar grains within an ordinary chondrite host (in situ) and the first TEM study to report on any presolar silicates
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Vanadium isotope fractionation during hydrothermal sedimentation: Implications for the vanadium cycle in the oceans Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-11 Fei Wu, Jeremy D. Owens, Christopher R. German, Rachel A. Mills, Sune G. Nielsen
Variations of V isotope ratios (δ51V) in sedimentary rocks have been proposed as a potential proxy for paleo-oceanic redox conditions, although the marine δ51V system is not fully constrained. Hydrothermal sediments are known to be a significant sink of V from the ocean. However, the V isotope fractionation associated with the accumulation into hydrothermal sediments from seawater and its influence
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Corrigendum to “The influence of skeletal micro-structures on potential proxy records in a bamboo coral” [Geochim. Cosmochim. Acta 248 (2019) 43–60] Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-07 Sebastian Flöter, Jan Fietzke, Marcus Gutjahr, Jesse Farmer, Bärbel Hönisch, Gernot Nehrke, Anton Eisenhauer
Abstract not available
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CaCO3 dissolution in carbonate-poor shelf sands increases with ocean acidification and porewater residence time Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-05 Abby Lunstrum, William Berelson
Carbonate-poor sandy sediments comprise much of the shelf area, and—despite their low CaCO3 content—contain a significant pool of CaCO3 base available to neutralize ocean acid. Here, we conducted flow-through column experiments on permeable, carbonate-poor sand obtained from Catalina Island, CA, to quantify CaCO3 dissolution across a range of current and future seawater conditions. Using 13C isotope
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Magma oceans, iron and chromium redox, and the origin of comparatively oxidized planetary mantles Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-04 M.M. Hirschmann
The mantles of both Earth and Mars are more oxidized than would be expected based on low pressure equilibration of molten silicate and alloy during their magma ocean stages. High pressure silicate-alloy equilibration in a magma ocean can produce appreciable ferric iron in the silicate, leading to comparatively oxidized near surface conditions and overlying atmospheres. Upon crystallization, this may
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Lithium isotope behaviour during basalt weathering experiments amended with organic acids Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-05 Philip A.E. Pogge von Strandmann, Xianyi Liu, Chun-Yao Liu, David J. Wilson, Samantha J. Hammond, Gary Tarbuck, Ludmilla Aristilde, Alexander J. Krause, Wesley T. Fraser
Lithium (Li) isotopes are a tracer of silicate weathering processes, but how they react to different components of organic and plant-assisted weathering is poorly known. To examine the effect of organic acids compared to a strong mineral acid (HCl) on Li isotope behaviour, basalt-water weathering experiments were amended with different organic acids (glycine, malic acid, cinnamic acid, and humic acid;
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A mechanistic investigation of the coral Mn/Ca-based trade-wind proxy at Kiritimati Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-04 Alice U. Chapman, Diane M. Thompson, Stephan R. Hlohowskyj, Jessica E. Carilli, Gwyneth Gordon, Tyler J. Goepfert, Hussein R. Sayani, Thomas M. Marchitto, Kim M. Cobb
Tropical Pacific trade-wind behavior is linked to the El Niño-Southern Oscillation and Pacific Decadal Variability, which modulate the rate of climate change. Despite their importance, high-resolution trade-wind observations span only the past 30–40 years and are too sparse to assess decadal wind variability and long-term trends. Previous work demonstrated that reef-building corals growing at the tropical
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Experimental determination of hydrogen isotope exchange rates between methane and water under hydrothermal conditions Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-05-02 Andrew C. Turner, Nicholas J. Pester, Markus Bill, Mark E. Conrad, Kevin G. Knauss, Daniel A. Stolper
The hydrogen isotopic composition of methane (CH4) is used as a fingerprint of gas origins. Exchange of hydrogen isotopes between CH4 and liquid water has been proposed to occur in both low- and high-temperature settings. However, despite environmental evidence for hydrogen isotope exchange between CH4 and liquid water, there are few experimental constraints on the kinetics of this process. We present
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Soil organic carbon accrual due to more efficient microbial utilization of plant inputs at greater long-term soil moisture Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-04-30 Itamar A. Shabtai, Srabani Das, Thiago M. Inagaki, Behrooz Azimzadeh, Brian Richards, Carmen Enid Martínez, Ingrid Kögel-Knabner, Johannes Lehmann
High long-term soil moisture may either stimulate or inhibit soil organic carbon (SOC) losses through changes to mineral and chemical composition, and resultant organo-mineral interactions. Yet, the trade-off between mineralization and accrual of SOC under long-term variation in unsaturated soil moisture remains uncertain. We tested the underexplored relationships between long-term soil moisture and
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Early diagenetic constraints on Permian seawater chemistry from the Capitan Reef Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-04-30 Roger N. Bryant, Theodore M. Present, Anne-Sofie C. Ahm, Harry-Luke O. McClelland, Dan Razionale, Clara L. Blättler
The Capitan Reef Complex in West Texas is famous for its high prevalence of early marine cements, unusual for a Phanerozoic platform, leading some to suggest that Precambrian styles of carbonate sedimentation enjoyed a Permian encore. Here, we use patterns of stable Ca, Mg, C and S isotopes to better understand the environmental driver(s) of the enigmatic cementation. We find that calcite that is the
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Oxidizing fluids associated with detachment hosted hydrothermal systems: Example from the Suye hydrothermal field on the ultraslow-spreading Southwest Indian Ridge Geochim. Cosmochim. Acta (IF 5.01) Pub Date : 2022-04-30 Shili Liao, Chunhui Tao, John W. Jamieson, Jia Liu, Chuanwei Zhu, Fernando J.A.S. Barriga, Wei Li, Jin Liang, Weifang Yang, Jianping Zhou, Xianming Deng, Junyu Yu
The redox state of hydrothermal fluids on mid-ocean ridges, which is indirectly affected by the depth of hydrothermal circulation and crustal permeability, plays an important role on the diversity of hydrothermal precipitates and associated ecosystems. Primary hydrothermal fluids that circulate along detachment faults are generally reducing as a result of the serpentinization of ultramafic rocks, while