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Water Research
1 June 2018
Thallium (Tl) sorption onto illite and smectite: Implications for Tl mobility in the environment
Publication date: 1 June 2018
Source:Geochimica et Cosmochimica Acta, Volume 230 Author(s): Lo
1 June 2018
The impact of the Cretaceous–Paleogene (K–Pg) mass extinction event on the global sulfur cycle: Evidence from Seymour Island, Antarctica
Publication date: 1 June 2018
Source:Geochimica et Cosmochimica Acta, Volume 230 Author(s): James D. Witts, Robert J. Newton, Benjamin J.W. Mills, Paul B. Wignall, Simon H. Bottrell, Joanna L.O. Hall, Jane E. Francis, J. Alistair Crame The Cretaceous–Paleogene (K–Pg) mass extinction event 66 million years ago led to large changes to the global carbon cycle, primarily via a decrease in primary or export productivity of the oceans. However, the effects of this event and longer-term environmental changes during the Late Cretaceous on the global sulfur cycle are not well understood. We report new carbonate associated sulfate (CAS) sulfur isotope data derived from marine macrofossil shell material from a highly expanded high latitude Maastrichtian to Danian (69–65.5
15 May 2018
Chlorine isotopic compositions of apatite in Apollo 14 rocks: Evidence for widespread vapor-phase metasomatism on the lunar nearside
15 May 2018
Microstructural and paleomagnetic insight into the cooling history of the IAB parent body
Publication date: 15 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 229 Author(s): Claire I.O. Nichols, Robert Krakow, Julia Herrero-Albillos, Florian Kronast, Geraint Northwood-Smith, Richard J. Harrison The IABs represent one of only two groups of iron meteorites that did not form by fractional crystallization of liquid Fe-Ni in the core of a differentiated planetesimal. Instead, they are believed to originate from a partially differentiated body that was severely disrupted by one or more impacts during its early history. We present a detailed microstructural and paleomagnetic study of the Odessa and Toluca IAB meteorites, with a view to further constraining the complex history of the IAB parent body. X-ray photoemission electron microscopy and energy dispersive spectroscopy were used to generate high-resolution Ni/Fe maps. The crystallographic architecture of Odessa was analysed using electron backscatter diffraction. Paleomagnetic signals and the magnetic properties of several microstructures were also assessed using X-ray magnetic circular dichroism. Odessa exhibits a complex series of microstructures, requiring an unusual evolution during slow cooling. A conventional Widmanst
15 May 2018
On the changing petroleum generation properties of Alum Shale over geological time caused by uranium irradiation
Publication date: 15 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 229 Author(s): Shengyu Yang, Hans-Martin Schulz, Brian Horsfield, Niels H. Schovsbo, Mareike Noah, Elena Panova, Heike Rothe, Knut Hahne An interdisciplinary study was carried out to unravel organic–inorganic interactions caused by the radiogenic decay of uranium in the immature organic-rich Alum Shale (Middle Cambrian-Lower Ordovician). Based on pyrolysis experiments, uranium content is positively correlated with the gas-oil ratios and the aromaticities of both the free hydrocarbons residing in the rock and the pyrolysis products from its kerogen, indicating that irradiation has had a strong influence on organic matter composition overall and hence on petroleum potential. The Fourier Transform Ion Cyclotron Resonance mass spectrometry data reveal that macro-molecules in the uranium-rich Alum Shale samples are less alkylated than less irradiated counterparts, providing further evidence for structural alteration by
15 May 2018
Modeling the carbon isotope signatures of methane and dissolved inorganic carbon to unravel mineralization pathways in boreal lake sediments
Publication date: 15 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 229 Author(s): F. Clayer, A. Moritz, Y. G
15 May 2018
Composition and molecular scale structure of nanophases formed by precipitation of biotite weathering products
Publication date: 15 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 229 Author(s): Wuhib Zewde Tamrat, J
15 May 2018
Toward an understanding of surface layer formation, growth, and transformation at the glass–fluid interface
Publication date: 15 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 229 Author(s): J. Hopf, J.R. Eskelsen, M. Chiu, A.V. Ievlev, O.S. Ovchinnikova, D. Leonard, E.M. Pierce Silicate glass is a metastable and durable solid that has application to a number of energy and environmental challenges (e.g., microelectronics, fiber optics, and nuclear waste storage). If allowed to react with water over time silicate glass develops an altered layer at the solid-fluid interface. In this study, we used borosilicate glass (LAWB45) as a model material to develop a robust understanding of altered layerformation (i.e., amorphous hydrated surface layer and crystalline reaction products). Experiments were conducted at high surface area-to-volume ratio (
15 May 2018
Origin of depleted basalts during subduction initiation and early development of the Izu-Bonin-Mariana island arc: Evidence from IODP expedition 351 site U1438, Amami-Sankaku basin
Publication date: 15 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 229 Author(s): R. Hickey-Vargas, G.M. Yogodzinski, O. Ishizuka, A. McCarthy, M. Bizimis, Y. Kusano, I.P. Savov, R. Arculus The Izu-Bonin-Mariana (IBM) island arc formed following initiation of subduction of the Pacific plate beneath the Philippine Sea plate at about 52
15 May 2018
Diagenetic variation at the lamina scale in lacustrine organic-rich shales: Implications for hydrocarbon migration and accumulation
Publication date: 15 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 229 Author(s): Chao Liang, Yingchang Cao, Keyu Liu, Zaixing Jiang, Jing Wu, Fang Hao Lacustrine carbonate-rich shales are well developed within the Mesozoic-Cenozoic strata of the Bohai Bay Basin (BBB) of eastern China and across southeast Asia. Developing an understanding of the diagenesis of these shales is essential to research on mass balance, diagenetic fluid transport and exchange, and organic-inorganic interactions in black shales. This study investigates the origin and distribution of authigenic minerals and their diagenetic characteristics, processes, and pathways at the scale of lacustrine laminae within the Es4s-Es3x shale sequence of the BBB. The research presented in this study is based on thin sections, field emission scanning electron microscope (FESEM) and SEM-catholuminescence (CL) observations of well core samples combined with the use of X-ray diffraction (XRD), energy dispersive spectroscopy, electron microprobe analysis, and carbon and oxygen isotope analyses performed using a laser microprobe mass spectrometer. The dominant lithofacies within the Es4s-Es3x sequence are a laminated calcareous shale (LCS-1) and a laminated clay shale (LCS-2). The results of this study show that calcite recrystallization1 is the overarching diagenetic process affecting the LCS-1, related to acid generation from organic matter (OM) thermal evolution. This evolutionary transition is the key factor driving the diagenesis of this lithofacies, while the transformation of clay minerals is the main diagenetic attribute of the LCS-2. Diagenetic differences occur within different laminae and at variable locations within the same lamina level, controlled by variations in mineral composition and the properties of laminae interfaces. The diagenetic fluid migration scale is vertical and responses (dissolution and replacement) are limited to individual laminae, between zero and 100
15 May 2018
Kinetics of dissolution of sapphire in melts in the CaO–Al2O3–SiO2 system
Publication date: 15 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 229 Author(s): Cliff S.J. Shaw, Kim B. Klausen, Huahai Mao The dissolution rate of sapphire in melts in the CAS system of varying silica activity, viscosity and degree of alumina saturation has been determined at 1600
15 May 2018
The silicon isotopic composition of fine-grained river sediments and its relation to climate and lithology
Publication date: 15 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 229 Author(s): G. Bayon, C. Delvigne, E. Ponzevera, A.V. Borges, F. Darchambeau, P. De Deckker, T. Lambert, L. Monin, S. Toucanne, L. Andr
1 May 2018
Age and evolution of diachronous erosion surfaces in the Amazon: Combining (U-Th)/He and cosmogenic 3He records
Publication date: 15 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 229 Author(s): H.S. Monteiro, P.M.P. Vasconcelos, K.A. Farley, C.A.M. Lopes (U-Th)/He geochronology of two weathered plateaus in the Caraj
1 May 2018
182W and HSE constraints from 2.7
1 May 2018
Dissolution of minerals with rough surfaces
Publication date: 1 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 228 Author(s): Thiago A. de Assis, F
1 May 2018
Reliability of shell carbon isotope composition of different land snail species as a climate proxy: A case study in the monsoon region of China
Publication date: 1 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 228 Author(s): Rui Bao, Xuefen Sheng, Henry H. Teng, Junfeng Ji Carbon isotope compositions of land snail shells (
1 May 2018
Isotopic coherence of refractory inclusions from CV and CK meteorites: Evidence from multiple isotope systems
Publication date: 1 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 228 Author(s): Quinn R. Shollenberger, Lars E. Borg, Jan Render, Samuel Ebert, Addi Bischoff, Sara S. Russell, Gregory A. Brennecka Calcium-aluminum-rich inclusions (CAIs) are the oldest dated materials in the Solar System and numerous previous studies have revealed nucleosynthetic anomalies relative to terrestrial rock standards in many isotopic systems. However, most of the isotopic data from CAIs has been limited to the Allende meteorite and a handful of other CV3 chondrites. To better constrain the isotopic composition of the CAI-forming region, we report the first Sr, Mo, Ba, Nd, and Sm isotopic compositions of two CAIs hosted in the CK3 desert meteorites NWA 4964 and NWA 6254 along with two CAIs from the CV3 desert meteorites NWA 6619 and NWA 6991. After consideration of neutron capture processes and the effects of hot-desert weathering, the Sr, Mo, Ba, Nd, and Sm stable isotopic compositions of the samples show clearly resolvable nucleosynthetic anomalies that are in agreement with previous results from Allende and other CV meteorites. The extent of neutron capture, as manifested by shifts in the observed 149Sm-150Sm isotopic composition of the CAIs is used to estimate the neutron fluence experienced by some of these samples and ranges from 8.40
1 May 2018
A new type of highly-vaporized microtektite from the Transantarctic Mountains
Publication date: 1 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 228 Author(s): M. Van Ginneken, M.J. Genge, R.P. Harvey We report on the discovery of microtektites (microscopic impact glass spherules) in a glacial moraine near Larkman Nunatak in the Transantarctic Mountains, Antarctica. The microtektites were identified based on their physical and chemical properties. Major and trace element compositions of the particles suggest that they may be related to the Australasian strewn field. This would further extend the current strewn field
1 May 2018
Geochemistry of fluids from Earth’s deepest ridge-crest hot-springs: Piccard hydrothermal field, Mid-Cayman Rise
Publication date: 1 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 228 Author(s): Jill M. McDermott, Sean P. Sylva, Shuhei Ono, Christopher R. German, Jeffrey S. Seewald Hosted in basaltic substrate on the ultra-slow spreading Mid-Cayman Rise, the Piccard hydrothermal field is the deepest currently known seafloor hot-spring (4957–4987
1 May 2018
Diagenesis in tephra-rich sediments from the Lesser Antilles Volcanic Arc: Pore fluid constraints
Publication date: 1 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 228 Author(s): Natalie A. Murray, James McManus, Martin R. Palmer, Brian Haley, Hayley Manners We present sediment pore fluid and sediment solid phase results obtained during IODP Expedition 340 from seven sites located within the Grenada Basin of the southern Lesser Antilles Volcanic Arc region. These sites are generally characterized as being low in organic carbon content and rich in calcium carbonate and volcanogenic material. In addition to the typical reactions related to organic matter diagenesis, pore fluid chemistry indicates that the diagenetic reactions fall within two broad categories; (1) reactions related to chemical exchange with volcanogenic material and (2) reactions related to carbonate dissolution, precipitation, or recrystallization. For locations dominated by reaction with volcanogenic material, these sites exhibit increases in dissolved Ca with coeval decreases in Mg. We interpret this behavior as being driven by sediment-water exchange reactions from the alteration of volcanic material that is dispersed throughout the sediment package, which likely result in formation of Mg-rich secondary authigenic clays. In contrast to this behavior, sediment sequences that exhibit decreases in Ca, Mg, Mn, and Sr with depth suggest that carbonate precipitation is an active diagenetic process affecting solute distributions. The distributions of pore fluid 87Sr/86Sr reflect these competitive diagenetic reactions between volcanic material and carbonate, which are inferred by the major cation distributions. From one site where we have solid phase 87Sr/86Sr (site U1396), the carbonate fraction is found to be generally consistent with the contemporaneous seawater isotope values. However, the 87Sr/86Sr of the non-carbonate fraction ranges from 0.7074 to 0.7052, and these values likely represent a mixture of local arc volcanic sources and trans-Atlantic eolian sources. Even at this site where there is clear evidence for diagenesis of volcanogenic material, carbonate diagenesis appears to buffer pore fluid 87Sr/86Sr from the larger changes that might be expected given the high abundance of tephra in these sediments. Part of this carbonate buffering, at this site as well as throughout the region, derives from the fact that the Sr concentration in the non-carbonate fraction is generally low (<200
1 May 2018
Implications of Eocene-age Philippine Sea and forearc basalts for initiation and early history of the Izu-Bonin-Mariana arc
Publication date: 1 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 228 Author(s): Gene M. Yogodzinski, Michael Bizimis, Rosemary Hickey-Vargas, Anders McCarthy, Benjamin D. Hocking, Ivan P. Savov, Osamu Ishizuka, Richard Arculus Whole-rock isotope ratio (Hf, Nd, Pb, Sr) and trace element data for basement rocks at ocean drilling Sites U1438, 1201 and 447 immediately west of the KPR (Kyushu-Palau Ridge) are compared to those of FAB (forearc basalts) previously interpreted to be the initial products of IBM subduction volcanism. West-of-KPR basement basalts (drill sites U1438, 1201, 447) and FAB occupy the same Hf-Nd and Pb-Pb isotopic space and share distinctive source characteristics with
1 May 2018
Modern rather than Mesoarchaean oxidative weathering responsible for the heavy stable Cr isotopic signatures of the 2.95
1 May 2018
Multicomponent diffusion in basaltic melts at 1350
1 May 2018
Mechanisms of interaction between arsenian pyrite and aqueous arsenite under anoxic and oxic conditions
Publication date: 1 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 228 Author(s): Guohong Qiu, Tianyu Gao, Jun Hong, Yao Luo, Lihu Liu, Wenfeng Tan, Fan Liu Pyrite affects the conversion and migration processes of arsenic in soils and waters. Adsorption and redox reactions of arsenite (As(III)) occur on the surface of pyrite, and the interaction processes are influenced by the arsenic incorporated into pyrite. This work examined the effects of arsenic content, pH and oxygen on the interaction between arsenian pyrite and aqueous As(III) and investigated the underlying mechanisms. The results indicated that arsenic incorporation led to a high content of Fe(III) in pyrite, and that As(III) was mainly adsorbed on pyrite surface and part of As(III) was oxidized to As(V) by the newly formed intermediates including hydroxyl radicals and hydrogen peroxide. The oxidation rate increased with increasing arsenic content in the pyrite and the presence of air (oxygen), and first decreased and then increased with increasing pH from 3.0 to 11.0. Hydroxyl radicals and hydrogen peroxide significantly contributed to the oxidation of pyrite and aqueous As(III) in acidic and alkaline solutions, respectively. Although pyrite oxidation increased with increasing arsenic content as indicated by the elevated concentrations of elemental S and SO4 2
1 May 2018
Oxygen isotope systematics of chondrules in the Murchison CM2 chondrite and implications for the CO-CM relationship
Publication date: 1 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 228 Author(s): No
1 May 2018
Massive production of heavy metals in the Ganga (Hooghly) River estuary, India: Global importance of solute-particle interaction and enhanced metal fluxes to the oceans
Publication date: 1 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 228 Author(s): Saumik Samanta, Tarun K. Dalai The Ganga River System is a major contributor to the global sediment and water discharge to the oceans. The estuary of Ganga (Hooghly) River in India is under increasing influence of anthropogenic contributions via discharge of the industrial and urban effluents. Here we document, based on the investigation of water and suspended sediment samples collected during six periods over two years, that there is extensive production of heavy metals (Co, Ni and Cu) in the estuary such that the annual dissolved fluxes of metals from the Hooghly River are enhanced by up to 230–1770%. Furthermore, the estuarine dissolved metal fluxes, when normalized with water fluxes, are the highest among estuaries of the major rivers in the world. Our simultaneous data on the dissolved, suspended particulate and exchangeable phases allow us to identify the ion-exchange process (coupled adsorption and desorption) as the dominant contributor to the generation of heavy metals in the middle and lower estuary where the estimated anthropogenic contribution is negligible. The estimated contributions from the groundwater are also insufficient to explain the measured metal concentrations in the estuary. A strong positive correlation that is observed between the dissolved heavy metal fluxes and the suspended particulate matter (SPM) fluxes, after normalizing them with the water fluxes, for estuaries of the major global rivers imply that the solute-particle interaction is a globally significant process in the estuarine production of metals. Based on this correlation that is observed for major estuaries around the world, we demonstrate that the South Asian Rivers which supply only
1 May 2018
Surface structure-dependent pyrite oxidation in relatively dry and moist air: Implications for the reaction mechanism and sulfur evolution
Publication date: 1 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 228 Author(s): Jianxi Zhu, Haiyang Xian, Xiaoju Lin, Hongmei Tang, Runxiang Du, Yiping Yang, Runliang Zhu, Xiaoliang Liang, Jingming Wei, H. Henry Teng, Hongping He Pyrite oxidation not only is environmentally significant in the formation of acid mine (or acid rock) drainage and oxidative acidification of lacustrine sediment but also is a critical stage in geochemical sulfur evolution. The oxidation process is always controlled by the reactivity of pyrite, which in turn is controlled by its surface structure. In this study, the oxidation behavior of naturally existing {1
1 May 2018
High temperature (&gt;350
1 May 2018
Processes controlling silicon isotopic fractionation in a forested tropical watershed: Mule Hole Critical Zone Observatory (Southern India)
Publication date: 1 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 228 Author(s): Jean Riotte, Jean-Dominique Meunier, Thomas Zambardi, St
1 May 2018
Tin isotope fractionation during magmatic processes and the isotope composition of the bulk silicate Earth
Publication date: 1 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 228 Author(s): Xueying Wang, Quentin Amet, Caroline Fitoussi, Bernard Bourdon Tin is a moderately volatile element whose isotope composition can be used to investigate Earth and planet differentiation and the early history of the Solar System. Although the Sn stable isotope composition of several geological and archaeological samples has been reported, there is currently scarce information about the effect of igneous processes on Sn isotopes. In this study, high-precision Sn isotope measurements of peridotites and basalts were obtained by MC-ICP-MS with a double-spike technique. The basalt samples display small variations in
15 April 2018
Corrigendum to “Processes and time scales of magmatic evolution as revealed by Fe–Mg chemical and isotopic zoning in natural olivines” [Geochim. Cosmochim. Acta 154 (2015) 130–150]
Publication date: 1 May 2018
Source:Geochimica et Cosmochimica Acta, Volume 228 Author(s): Martin Oeser, Ralf Dohmen, Ingo Horn, Stephan Schuth, Stefan Weyer
15 April 2018
Rapid arsenic(V)-reduction by fire in schwertmannite-rich soil enhances arsenic mobilisation
Publication date: 15 April 2018
Source:Geochimica et Cosmochimica Acta, Volume 227 Author(s): Scott G. Johnston, William W. Bennett, Edward D. Burton, Kerstin Hockmann, Nigel Dawson, Niloofar Karimian Arsenic in acid sulfate soil (ASS) landscapes commonly associates with schwertmannite, a poorly crystalline Fe(III) mineral. Fires in ASS landscapes can thermally transform Fe(III) minerals to more crystalline phases, such as maghemite (
15 April 2018
Chronology of formation of early solar system solids from bulk Mg isotope analyses of CV3 chondrules
Publication date: 15 April 2018
Source:Geochimica et Cosmochimica Acta, Volume 227 Author(s): Hsin-Wei Chen, Jennifer L. Claydon, Tim Elliott, Christopher D. Coath, Yi-Jen Lai, Sara S. Russell We have analysed the petrography, major element abundances and bulk Al-Mg isotope systematics of 19 ferromagnesian chondrules from the CV3 chondrites Allende, Mokoia, and Vigarano, together with an Al-rich chondrule and refractory olivine from Mokoia. Co-variations of Al/Mg with Na/Mg and Ti/Mg in our bulk chondrules suggest their compositions are dominantly controlled by reworking of different proportions of chondrule components (e.g. mafic minerals and mesostatis); their precursors are thus fragments from prior generations of chondrules. Our samples show a range in fractionation corrected 26Mg/24Mg (
15 April 2018
I-Xe dating of aqueous alteration in the CI chondrite Orgueil: I. Magnetite and ferromagnetic separates
Publication date: 15 April 2018
Source:Geochimica et Cosmochimica Acta, Volume 227 Author(s): O. Pravdivtseva, A.N. Krot, C.M. Hohenberg The I-Xe system was studied in a ferromagnetic sample separated from the Orgueil CI carbonaceous chondrite with a hand-held magnet and in two magnetite samples, one chemically separated before and the other one after neutron irradiation. This work was done in order to investigate the effects of chemical separation by LiCl and NaOH on the I-Xe system in magnetite. Our test demonstrated that the chemical separation of magnetite before irradiation using either LiCl or NaOH, or both, does not contaminate the sample with iodine and thus cannot lead to erroneous I-Xe ages due to introduction of uncorrelated 128
15 April 2018
Revisiting the effects of hydrodynamic sorting and sedimentary recycling on chemical weathering indices
Publication date: 15 April 2018
Source:Geochimica et Cosmochimica Acta, Volume 227 Author(s): Yulong Guo, Shouye Yang, Ni Su, Chao Li, Ping Yin, Zhongbo Wang Although the proxies based on elemental geochemistry of siliciclastic sediments have been well developed to indicate the intensity of chemical weathering in various catchments, their geological indications and limitations, and especially how the differentiation of minerals and sediment grain size influences the applications of these proxies needs more clarification. This paper investigates the interactive effects of weathering, hydraulic sorting and sedimentary recycling on river sediment chemistry, and further validates the application of various weathering indices by measuring mineralogical and geochemical compositions of bank sediments and suspended particulate matters (SPMs) from five rivers in East China bearing various sizes, geologic settings and climatic regimes. For a specific river, the silicate weathering intensity registered in the fine SPMs is systematically stronger than that in the coarse-grained bank sediments. Most of the weathering indices not only reflect the integrated weathering history of various catchments but also depend on hydraulic sorting effect during sediment transport and depositional processes. The correlation between CIA (chemical index of alteration) and WIP (weathering index of Parker) offers an approach to predict the weathering trends of the fine SPMs, coarse bank sediments and recycled sediments under the influence of quartz dilution. To minimize the effects of hydrodynamic sorting and sedimentary recycling, we suggest that the fine sediments (e.g. SPMs and <2
15 April 2018
Computational prediction of Mg-isotope fractionation between aqueous [Mg(OH2)6]2+ and brucite
Publication date: 15 April 2018
Source:Geochimica et Cosmochimica Acta, Volume 227 Author(s): Christopher A. Colla, William H. Casey, C. Andr
15 April 2018
A model for the oceanic mass balance of rhenium and implications for the extent of Proterozoic ocean anoxia
Publication date: 15 April 2018
Source:Geochimica et Cosmochimica Acta, Volume 227 Author(s): Alex I. Sheen, Brian Kendall, Christopher T. Reinhard, Robert A. Creaser, Timothy W. Lyons, Andrey Bekker, Simon W. Poulton, Ariel D. Anbar Emerging geochemical evidence suggests that the atmosphere-ocean system underwent a significant decrease in O2 content following the Great Oxidation Event (GOE), leading to a mid-Proterozoic ocean (ca. 2.0–0.8
15 April 2018
Montmorillonite dissolution kinetics: Experimental and reactive transport modeling interpretation
Publication date: 15 April 2018
Source:Geochimica et Cosmochimica Acta, Volume 227 Author(s): Chiara Cappelli, Shingo Yokoyama, Jordi Cama, F. Javier Huertas The dissolution kinetics of K-montmorillonite was studied at 25
15 April 2018
More than ten million years of hyper-aridity recorded in the Atacama Gravels
Publication date: 15 April 2018
Source:Geochimica et Cosmochimica Acta, Volume 227 Author(s): Tao Sun, Huiming Bao, Martin Reich, Sidney R. Hemming The Atacama Desert’s hyper-aridity is closely linked to the development of world-class copper and nitrate/iodine ores and to regional tectonics and global paleoclimate changes in the Cenozoic era. The timing when the hyper-aridity commenced remains controversial, with proposed ages ranging from Late Oligocene to Pleistocene. In this study, we provide an independent constraint on the initiation of Atacama hyper-aridity utilizing a 100-m deep profile within the Atacama Gravels and underneath porphyry copper deposit in Spence, northern Chile. The overall high concentration of sulfate (up to 10
15 April 2018
Intracrystalline “geothermometry” assessed on clino and orthopyroxene bearing synthetic rocks
Publication date: 15 April 2018
Source:Geochimica et Cosmochimica Acta, Volume 227 Author(s): M. Murri, F. C
15 April 2018
Thallium dynamics in the southern North Sea
Publication date: 15 April 2018
Source:Geochimica et Cosmochimica Acta, Volume 227 Author(s): Philipp B
15 April 2018
Archaeal and bacterial H-GDGTs are abundant in peat and their relative abundance is positively correlated with temperature
Publication date: 15 April 2018
Source:Geochimica et Cosmochimica Acta, Volume 227 Author(s): B.D.A. Naafs, D. McCormick, G.N. Inglis, R.D. Pancost Glycerol monoalkyl glycerol tetraether lipids (GMGTs; also called ‘H-GDGTs’) differ from the more commonly studied glycerol dialkyl glycerol tetraether (GDGTs) in that they have an additional covalent bond that links the two alkyl chains. Six different archaeal isoprenoidal H-GDGTs (H-isoGDGTs) and one branched H-GDGT (H-brGDGT), presumably produced by bacteria, have previously been found. However, the function of H-GDGTs in both domains of life is unknown. It is thought that the formation of this additional covalent bond results in enhanced membrane stability, accounting for the high abundance of H-GDGTs in extreme environments such as geothermal settings, but so far there has been little evidence to support this hypothesis. Here we report the distribution of H-GDGTs in a global peat database (n
15 April 2018
Transport and deposition of the fire biomarker levoglucosan across the tropical North Atlantic Ocean
Publication date: 15 April 2018
Source:Geochimica et Cosmochimica Acta, Volume 227 Author(s): Laura T. Schreuder, Ellen C. Hopmans, Jan-Berend W. Stuut, Jaap S. Sinninghe Damst
15 April 2018
Miocene weathering environments in Western Australia—Inferences from the abundance and 13C/12C of Fe(CO3)OH in CID goethite
Publication date: 15 April 2018
Source:Geochimica et Cosmochimica Acta, Volume 227 Author(s): Tyler O. Fritz, Crayton J. Yapp The channel iron deposits (CID) of the Hamersley Province in Western Australia are dominated by pedogenic goethite/hematite-rich ooids and pisoids that were transported to, and deposited in, the meandering channels of Miocene rivers. Information about the Miocene weathering environments that produced the Fe(III) oxides is archived in the mole fraction (X) and
15 April 2018
Effect of aqueous Si/Mg ratio and pH on the nucleation and growth of sepiolite at 25
15 April 2018
Development of a mixed seawater-hydrothermal fluid geochemical signature during alteration of volcanic rocks in the Archean (
15 April 2018
Physical heterogeneity control on effective mineral dissolution rates
Publication date: 15 April 2018
Source:Geochimica et Cosmochimica Acta, Volume 227 Author(s): Heewon Jung, Alexis Navarre-Sitchler Hydrologic heterogeneity may be an important factor contributing to the discrepancy in laboratory and field measured dissolution rates, but the governing factors influencing mineral dissolution rates among various representations of physical heterogeneity remain poorly understood. Here, we present multiple reactive transport simulations of anorthite dissolution in 2D latticed random permeability fields and link the information from local grid scale (1
Available online 14 April 2018
Modeling the effects of diagenesis on carbonate clumped-isotope values in deep- and shallow-water settings
Publication date: 15 April 2018
Source:Geochimica et Cosmochimica Acta, Volume 227 Author(s): Daniel A. Stolper, John M. Eiler, John A. Higgins The measurement of multiply isotopically substituted (‘clumped isotope’) carbonate groups provides a way to reconstruct past mineral formation temperatures. However, dissolution-reprecipitation (i.e., recrystallization) reactions, which commonly occur during sedimentary burial, can alter a sample’s clumped-isotope composition such that it partially or wholly reflects deeper burial temperatures. Here we derive a quantitative model of diagenesis to explore how diagenesis alters carbonate clumped-isotope values. We apply the model to a new dataset from deep-sea sediments taken from Ocean Drilling Project site 807 in the equatorial Pacific. This dataset is used to ground truth the model. We demonstrate that the use of the model with accompanying carbonate clumped-isotope and carbonate
Available online 14 April 2018
Formation and evolution of multistage magmatic-hydrothermal fluids at the Yulong porphyry Cu-Mo deposit, eastern Tibet: Insights from LA-ICP-MS analysis of fluid inclusions
Publication date: Available online 14 April 2018
Source:Geochimica et Cosmochimica Acta Author(s): Jia Chang, Jian-Wei Li, Andreas Aud

Evidence for a sulfur-undersaturated lunar interior from the solubility of sulfur in lunar melts and sulfide-silicate partitioning of siderophile elements
Publication date: Available online 14 April 2018
Source:Geochimica et Cosmochimica Acta Author(s): E.S. Steenstra, A.X. Seegers, J. Eising, B.G.J. Tomassen, F.P.F. Webers, J. Berndt, S. Klemme, S. Matveev, W. van Westrenen Sulfur concentrations at sulfide saturation (SCSS) were determined for a range of low- to high-Ti lunar melt compositions (synthetic equivalents of Apollo 14 black and yellow glass, Apollo 15 green glass, Apollo 17 orange glass and a late-stage lunar magma ocean melt, containing between 0.2 and 25 wt.% TiO2) as a function of pressure (1 – 2.5 GPa) and temperature (1683 – 1883 K). For the same experiments, sulfide-silicate partition coefficients were derived for elements V, Cr, Mn, Co, Cu, Zn, Ga, Ge, As, Se, Mo, Sn, Sb, Te, W and Pb. The SCSS is a strong function of silicate melt composition, most notably FeO content. An increase in temperature increases the SCSS and an increase in pressure decreases the SCSS, both in agreement with previous work on terrestrial, lunar and martian compositions. Previously reported SCSS values for high-FeO melts were combined with the experimental data reported here to obtain a new predictive equation to calculate the SCSS for high-FeO lunar melt compositions. Calculated SCSS values, combined with previously estimated S contents of lunar low-Ti basalts and primitive pyroclastic glasses, suggest their source regions were not sulfide saturated. Even when correcting for the currently inferred maximum extent of S degassing during or after eruption, sample S abundances are still >700 ppm lower than the calculated SCSS values for these compositions. To achieve sulfide saturation in the source regions of low-Ti basalts and lunar pyroclastic glasses, the extent of degassing of S in lunar magma would have to be orders of magnitude higher than currently thought, inconsistent with S isotopic and core-to-rim S diffusion profile data. The only lunar samples that could have experienced sulfide saturation are some of the more evolved A17 high-Ti basalts, if sulfides are Ni- and/or Cu rich. Sulfide saturation in the source regions of lunar melts is also inconsistent with the sulfide-silicate partitioning systematics of Ni, Co and Cu. Segregation of significant quantities of (non)-stoichiometric sulfides during fractional crystallization would result in far larger depletions of Ni, Co and Cu than observed, whereas trends in their abundances are more likely explained by olivine fractionation. The sulfide exhaustion of the lunar magma source regions agrees with previously proposed low S abundances in the lunar core and mantle, and by extension with relatively minor degassing of S during the Moon-forming event. Our results support the hypothesis that refractory chalcophile and highly siderophile element systematics of low-Ti basalts and pyroclastic glasses reflect the geochemical characteristics of their source regions, instead of indicating the presence of residual sulfides in the lunar interior.
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