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Vacuum
5 February 2018
Editorial Board
Publication date: 5 February 2018
Source:Chemical Geology, Volume 478

5 February 2018
The speciation, distribution, transport, and impact of volatile elements in the Earth's interior
Publication date: 5 February 2018
Source:Chemical Geology, Volume 478 Author(s): Huaiwei Ni, Kate Kiseeva, Oliver Lord, Andrew Thomson, Klaus Mezger
5 February 2018
Metasomatism in the sub-continental lithospheric mantle beneath the south French Massif Central: Constraints from trace elements, Li and H in peridotite minerals
Publication date: 5 February 2018
Source:Chemical Geology, Volume 478 Author(s): Xiaoyan Gu, Jannick Ingrin, Etienne Deloule, Lyd
5 February 2018
Water in garnet pyroxenite from the Sulu orogen: Implications for crust-mantle interaction in continental subduction zone
Publication date: 5 February 2018
Source:Chemical Geology, Volume 478 Author(s): Hai-Yong Li, Ren-Xu Chen, Yong-Fei Zheng, Zhaochu Hu Mineral water contents, together with the major and trace element compositions of minerals and whole-rock, were determined for garnet pyroxenites enclosed by ultrahigh-pressure (UHP) metamorphic gneiss at Hujialin in the Sulu orogen. The garnet pyroxenites have low SiO2 contents of 40.25 to 46.68wt% and MgO contents of 10.99 to 14.79wt%. They are characterized by enrichment in LREE and LILE (Ba, Sr, Pb) but depletion in HFSE (Nb, Zr) and HREE. They were generated in the Triassic by metasomatic reaction of the mantle wedge peridotite with hydrous felsic melts derived from partial melting of the deeply subducted continental crust. Measured water contents vary from 523 to 1213ppm for clinopyroxene, and 55 to 1476ppm for garnet. These mineral water contents are not only correlated with mineral major and trace element abundances but also relatively homogenous within single mineral grains. Such features preclude significant disturbance of the mineral water contents during pyroxenite exhumation from the mantle depth to the surface and thus indicate preservation of the primary water contents for the UHP metasomatites. The garnet pyroxenites are estimated to have bulk water contents of 424660ppm, which are higher than those for the MORB source, similar to or higher than those for the OIB sources and close to the lower limit for the arc magma source. The relationships between contents of mineral water and some elements suggest that the high water contents of garnet pyroxenites are primarily determined by the abundance of water-rich clinopyroxene. Garnet also has the high water contents, suggesting its importance in hosting water at mantle depths. Calculated whole-rock H2O/Ce ratios are 63145, higher than those for Hawaiian garnet pyroxenites and SWIR abyssal pyroxenites. These observations suggest that metasomatic pyroxene-rich lithologies have the capacity to contribute high H2O concentrations and variable H2O/Ce ratios to the mantle. This lends support to the interpretation that the source of some intraplate basalts may be a heterogeneous mixture of peridotite and pyroxenite. On the other hand, the high water contents of garnet pyroxenites suggest that the presence of ultramafic metasomatites in the mantle wedge would enhance its water storage and thus reduce the water transport into deeper mantle by subduction.
5 February 2018
Belingwe komatiites (2.7Ga) originate from a plume with moderate water content, as inferred from inclusions in olivine
Publication date: 5 February 2018
Source:Chemical Geology, Volume 478 Author(s): E.V. Asafov, A.V. Sobolev, A.A. Gurenko, N.T. Arndt, V.G. Batanova, M.V. Portnyagin, D. Garbe-Sch
5 February 2018
A general model of water diffusivity in calc-alkaline silicate melts and glasses
Publication date: 5 February 2018
Source:Chemical Geology, Volume 478 Author(s): Huaiwei Ni, Li Zhang The calc-alkaline magma series (basalt, andesite, dacite, and rhyolite) commonly occurring at subduction zones are typically hydrous. Water diffusivity in silicate melt is a crucial parameter controlling the transport and evolution of water throughout magma differentiation. Based on experimental data accumulated over the past three decades, we develop a unified, mechanistic and quantitative model of water diffusion and diffusivity in calc-alkaline silicate melts and glasses. This model involves the following features: (1) the coupling of water diffusion and water speciation; (2) an exponential increase of molecular H2O (H2O m ) diffusivity with the mole fraction of total water (X), D H2O m = D 0 exp(aX), and OH diffusivity (D OH) independent of total water content; (3) the influence of temperature and melt/glass composition on water speciation, the parameter a, and the ratio D OH /D 0; and (4) the influence of temperature, composition and pressure on D 0. Using the mole fraction of Si among all cations (Y Si) to index melt/glass composition, we find that total water (H2O t ) diffusivity at 1wt% H2O t decreases with increasing Y Si (i.e., from basaltic to rhyolitic composition) at high temperature (T >1300K) but this trend is reversed in the low temperature range (T <900K). A vast majority of diffusivity data, including those used for model development and those excluded, can be reproduced by our model within a factor of 2, only slightly greater than experimental uncertainty. This new model allows to trace the evolution of water diffusivity along the liquid line of descent, and is particularly useful when the composition of interest is intermediate between the specific compositions previously investigated.
5 February 2018
Carbonated mantle domains at the base of the Earth's transition zone
Publication date: 5 February 2018
Source:Chemical Geology, Volume 478 Author(s): Wei-dong Sun, Chris J. Hawkesworth, Chao Yao, Chan-chan Zhang, Rui-fang Huang, Xi Liu, Xin-lei Sun, Trevor Ireland, Mao-shuang Song, Ming-xing Ling, Xing Ding, Zhao-feng Zhang, Wei-ming Fan, Zhong-qing Wu The oxygen fugacity of the upper mantle is 34 orders of magnitude higher than that of the lower mantle and this has been attributed to Fe2+ disproportionating into Fe3+ plus Fe0 at pressures >24GPa. The upper mantle might therefore have been expected to have evolved to more oxidizing compositions through geological time, but it appears that the oxygen fugacity of the upper mantle has remained constant for the last 3.5billionyears. Thus, it indicates that the mantle has been actively buffered from the accumulation of Fe3+, and that this is linked to oxidation of diamond to carbonate coupled with reduction of Fe3+ to Fe2+. When subducted plates penetrate into the lower mantle, compensational upwelling transports bridgmanite into the transition zone, where it breaks down to ringwoodite and majorite, releasing the ferric iron. The system returns to equilibrium through oxidation of diamond. Early in Earth history, diamond may have been enriched at the base of the transition zone in the Magma Ocean, because it is denser than peridotite melts at depths shallower than 660km, and it is more buoyant below. Ongoing oxidation of diamond forms carbonate, leading to relatively high carbonate concentrations in the source of ocean island basalts.
5 February 2018
Monticellite in group-I kimberlites: Implications for evolution of parental melts and post-emplacement CO2 degassing
Publication date: 5 February 2018
Source:Chemical Geology, Volume 478 Author(s): Adam Abersteiner, Vadim S. Kamenetsky, D. Graham Pearson, Maya Kamenetsky, Karsten Goemann, Kathy Ehrig, Thomas Rodemann Monticellite is a magmatic and/or deuteric mineral that is often present, but widely varying in concentrations in Group-I (or archetypal) kimberlites. To provide new constraints on the petrogenesis of monticellite and its potential significance to kimberlite melt evolution, we examine the petrography and geochemistry of the minimally altered hypabyssal monticellite-rich Leslie (Canada) and Pipe 1 (Finland) kimberlites. In these kimberlites, monticellite (Mtc) is abundant (2545vol%) and can be classified into two distinct morphological types: discrete and intergrown groundmass grains (Mtc-I), and replacement of olivine (Mtc-II). Primary multiphase melt inclusions in monticellite, perovskite and Mg-magnetite contain assemblages dominated by alkali (Na, K, Ba, Sr)-enriched Ca-Mg-carbonates, chlorides, phosphates, spinel, silicates (e.g. olivine, phlogopite) and sulphides. These melt inclusions probably represent snapshots of a variably differentiated kimberlite melt that evolved in-situ towards carbonatitic and silica-poor compositions. Although unconstrained in their concentration, the presence of alkali-carbonates and chlorides in melt inclusions suggests they are a more significant component of the kimberlite melt than commonly recorded by whole-rock analyses. We present petrographic and textural evidence showing that pseudomorphic Mtc-II resulted from an in-situ reaction between olivine and the carbonate component of the kimberlite melt in the decarbonation reaction: Forsterite + Carbonate melt
5 February 2018
Recycling of subducted carbonates: Formation of the Taohuala Mountain carbonatite, North China Craton
Publication date: 5 February 2018
Source:Chemical Geology, Volume 478 Author(s): Shuo Xue, Ming-Xing Ling, Yu-Long Liu, Weidong Sun Carbonatitic magmatism plays a significant role in Earth's carbon cycle, which is also a lithoprobe of crust-mantle interaction, mantle metasomatism and partial melting. Due to different mineral assemblages and geochemical compositions, and diverse tectonic settings, the origin of carbonatite has long been debated. At subduction zones, sediments (including carbonates) are subducted into the mantle with the downgoing oceanic slab. However, the detailed mechanism of how subducted carbonates contribute to carbonatitic magmatism remains unclear. Here we present geochronological, geochemical and isotopic study on the Taohuala Mountain carbonatite at the southern margin of the Alxa Block, North China Craton. The classification of carbonatite from the Taohuala Mountain relies strongly on the observations of obvious intrusion contact relationships and flow structures in field outcrop. The Taohuala Mountain carbonatite has SiO2 ranging from 2.37wt.% to 11.45wt%, high CaO (45.9353.86wt%) and low MgO (0.514.39wt%), and is characterized by enrichment of LILE (Ba, Sr), depletion of HFSE (Nb, Ta, Zr, Hf), and slightly negative Ce and Eu anomalies. Carbonates in the samples have high 87Sr/86Sr (0.706860.70694) and low 143Nd/144Nd (0.5116350.511924). Remarkably, the highly fractionated
5 February 2018
Silicate-sulfide liquid immiscibility in modern arc basalt (Tolbachik volcano, Kamchatka): Part I. Occurrence and compositions of sulfide melts
Publication date: 5 February 2018
Source:Chemical Geology, Volume 478 Author(s): M. Zelenski, V.S. Kamenetsky, J.A. Mavrogenes, A.A. Gurenko, L.V. Danyushevsky Silicate-sulfide liquid immiscibility plays a key role in the formation of magmatic sulfide ore deposits but incipient sulfide melts are rarely preserved in natural rocks. This study presents the distribution and compositions of olivine-hosted sulfide melt globules resulting from silicate-sulfide liquid immiscibility in primitive arc basalts. Abundant sulfide droplets entrapped in olivine from primitive basalts of the 1941 eruption and pre-historic eruptive cone Mt. 1004 of the Tolbachik volcano, Kurile-Kamchatka arc. Inclusions range from submicron to 250
5 February 2018
Reprint of Silicate-sulfide liquid immiscibility in modern arc basalt (Tolbachik volcano, Kamchatka): Part II. Composition, liquidus assemblage and fractionation of the silicate melt
Publication date: 5 February 2018
Source:Chemical Geology, Volume 478 Author(s): Vadim S. Kamenetsky, Michael Zelenski, Andrey Gurenko, Maxim Portnyagin, Kathy Ehrig, Maya Kamenetsky, Tatiana Churikova, Sandrin Feig Olivine-hosted inclusions of silicate and sulfide melts, Cr-spinel and pyroxene were studied to estimate magma composition, temperature, pressure, and fO2 at the onset and during the silicate-sulfide immiscibility in modern arc basalt from Tolbachik volcano, Kamchatka arc. We demonstrate that the olivine phenocrysts hosting sulfide and silicate melt inclusions belong to the same population. The compositions of the silicate melt inclusions in most primitive olivine (8891mol% Fo) represent moderately oxidized (~QFM+1.1) high-MgO (up to 1212.6wt%) and high CaO/Al2O3 (0.81.2) melt that has abundances and ratios of the lithophile trace elements typical of island arc magmas. The initial volatile contents in parental Tolbachik magma are estimated from the melt inclusions and mass-balance considerations to be at least 4.9wt% H2O, 2600ppm S, 1100ppm Cl, 550ppm F, and 1200ppm CO2. These data are used to calculate the temperature (~1220C) and minimum pressure (3kbar) at which the beginning of crystallization and exsolution of sulfide melt took place. The presence of anhydrite, especially ubiquitous in the crystallized silicate melt associated with sulfide globules, suggest that much higher sulfur abundances prior to degassing and sulfate immiscibility and/or crystallization should be expected. We tentatively considered hydrothermal accumulations of sulfur (elemental, sulfate and sulfide) in the volcanic conduit responsible for local contamination and oversaturation of the Tolbachik magma in sulfur and related sulfide immiscibility. Coexisting sulfide and sulfate can be also interpreted in favor of the magmatic sulfide oxidation and related generation of S-rich fluids. Such fluids are expected to accumulate metals released from decomposed sulfide melts and supply significant epithermal mineralization, including native gold.
5 February 2018
Origin of volatiles emitted by Plinian mafic eruptions of the Chikurachki volcano, Kurile arc, Russia: Trace element, boron and sulphur isotope constraints
Publication date: 5 February 2018
Source:Chemical Geology, Volume 478 Author(s): Andrey A. Gurenko, Alexander B. Belousov, Vadim S. Kamenetsky, Michael E. Zelenski Chikurachki is a 1816-m high stratovolcano on Paramushir Island, Kurile arc, Russia, which has repeatedly produced highly explosive eruptions of mafic composition. The present work is aimed at constraining the origin of volatile components (CO2, H2O, F, S, and Cl), along with B and S isotopic compositions in a series of phenocryst-hosted melt inclusions and groundmass glasses from basaltic andesite pyroclasts of the 1853, 1986, and prehistoric Plinian eruptions of the volcano. The ranges of volatile concentrations in melt inclusions (471580
5 February 2018
Significance of halogens (F, Cl) in kimberlite melts: Insights from mineralogy and melt inclusions in the Roger pipe (Ekati, Canada)
Publication date: 5 February 2018
Source:Chemical Geology, Volume 478 Author(s): Adam Abersteiner, Vadim S. Kamenetsky, Maya Kamenetsky, Karsten Goemann, Kathy Ehrig, Thomas Rodemann The abundance and distribution of halogens (F, Cl) are rarely recorded in kimberlites and therefore their petrogenetic significance is poorly constrained. Halogens are usually present in kimberlite rocks in the structure of phlogopite and apatite, but their original concentrations are never fully retained due to the effects of alteration. To provide new constraints on the origin and evolution of halogens in kimberlites and their melts, we present a detailed study of the petrography and geochemistry of the late-Cretaceous Group-I (or archetypal) Roger kimberlite (Ekati cluster, Canada). The studied samples contain abundant anhedral-to-euhedral olivine which is set in a crystalline groundmass of monticellite, phlogopite, apatite, spinel (i.e. magnesian ulv
20 January 2018
Halogen geochemistry of I- and A-type granites from Jiuhuashan region (South China): Insights into the elevated fluorine in A-type granite
Publication date: 5 February 2018
Source:Chemical Geology, Volume 478 Author(s): Lian-Xun Wang, Chang-Qian Ma, Chao Zhang, Yu-Xiang Zhu, Michael A.W. Marks Spatially associated A- and I- type granites and mafic dyke rocks from the Jiuhuashan region (South China) have been geochemically studied with a special emphasis on their halogen (F, Cl, Br, I) contents to better understand the role of halogens during their genesis. The A-type granites and mafic dyke rocks (125130Ma) intruded later than the I-type rocks (140143Ma) and whole-rock Nb/Ta ratios increase from I-type granites (1214) via A-type granites (1418) to mafic dykes (1920). The
20 January 2018
Editorial Board
Publication date: 20 January 2018
Source:Chemical Geology, Volume 477

20 January 2018
Phosphorus cycling in marine sediments: Advances and challenges
Publication date: 20 January 2018
Source:Chemical Geology, Volume 477 Author(s): Delphine Defforey, Adina Paytan Phosphorus (P) is a critical macronutrient for all living cells, as it provides the phosphate-ester backbone of nucleic acids, plays a crucial role in the transmission of chemical energy by the ATP molecule and is also a structural constituent in many cell components. While P cycling in the marine water column has been the subject of many studies and reviews, many aspects of the sedimentary P cycling remain poorly understood. This is mainly due to low P concentrations in sediments and analytical difficulties associated with isolating distinct P forms from sediment samples. The aim of this review is to highlight the advances made in our understanding of P cycling in marine sediments as a result of improved instrumentation and novel approaches. Some of these techniques range from sediment sequential extractions (SEDEX) to spectroscopic techniques (31P NMR) and innovative isotope tracer experiments (stable oxygen ratios in phosphate, radioactive P isotopes). While our understanding of P cycling has considerably improved, numerous aspects of sedimentary P cycling including the fate of organic P in sediments as a function of redox conditions, organic matter content and burial depth, as well as turnover rates of different sedimentary P compounds remain poorly constrained. The techniques presented in this review, along with yet to be utilized innovative approaches used in soil and lacustrine sediment P research, will play an important role in addressing these important questions and in furthering our understanding of this critical component of the P global biogeochemical cycle.
20 January 2018
Synergistic adsorption of Cd(II) with sulfate/phosphate on ferrihydrite: An in situ ATR-FTIR/2D-COS study
Publication date: 20 January 2018
Source:Chemical Geology, Volume 477 Author(s): Jing Liu, Runliang Zhu, Xiaoliang Liang, Lingya Ma, Xiaoju Lin, Jianxi Zhu, Hongping He, Stephen C. Parker, Marco Molinari Elucidation of the co-adsorption characteristics of heavy metal cations and oxyanions on (oxyhydr)oxides can help to better understand their distribution and transformation in many geological settings. In this work, batch adsorption experiments in combination with in situ attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) were applied to explore the interaction mechanisms of Cd(II) with sulfate or phosphate at the ferrihydrite (Fh)water interface, and the two-dimensional correlation spectroscopic analysis (2DCOS) was used to enhance the resolution of ATR-FTIR bands and the accuracy of analysis. The batch adsorption experiments showed enhanced adsorption of both sulfate (S) and phosphate (P) on Fh when co-adsorbed with Cd(II); additionally, the desorbed percentages of Cd(II) were much lower in the P+Cd adsorption systems than those in the S+Cd adsorption systems. The spectroscopic results suggested that in the single adsorption systems, sulfate primarily adsorbed as outer-sphere complexes with a small amount of bidentate inner-sphere complexes, while the dominant adsorbed species of phosphate were largely the bidentate nonprotonated inner-sphere complexes, although there was significant pH-dependence. In the co-adsorption systems, the synergistic adsorption of Cd(II) and sulfate was dominantly attributed to the electrostatic interaction, as well as the formation of FeCdS (i.e., Cd-bridged) ternary complexes. In contrast, FePCd (i.e., phosphate-bridged) ternary complexes were found in all of the co-adsorption systems of phosphate and Cd(II); furthermore, electrostatic interaction should also contribute to the co-adsorption process. Our results show that in situ ATR-FTIR in combination with 2DCOS can be an efficient tool in analyzing the co-adsorption mechanisms of anions and heavy metal cations on iron (oxyhydr)oxides in ternary adsorption systems. The co-existence of Cd(II) with sulfate or phosphate can be beneficial for their accumulations on Fh, and phosphate is more efficient than sulfate for the long-term immobilization of Cd(II).

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20 January 2018
U-series disequilibria in minerals from Gandak River sediments (Himalaya)
Publication date: 20 January 2018
Source:Chemical Geology, Volume 477 Author(s): Clio Bosia, Fran
20 January 2018
Lead isotopes as particulate contaminant tracers and chronostratigraphic markers in lake sediments in northeastern North America
Publication date: 20 January 2018
Source:Chemical Geology, Volume 477 Author(s): Carol A.L. Cheyne, Alyson M. Thibodeau, Gregory F. Slater, Bridget A. Bergquist The utility of lead (Pb) isotopes as tracers of particulate contamination and as chronostratigraphic markers was assessed in five lake sediment cores from the Great Lakes and southern Ontario region. The marker for smelting of highly radiogenic ores in the Upper Mississippi Valley in the mid-19th century was seen in the Pb isotopes in four lakes expanding the geographic range of this established marker into southern and central Ontario. This marker is useful for age-dating sediments deposited in the 1800s in archives where it is present. The estimated dates for this ~1850 marker using other dating methods span a range of 57years, emphasizing the importance of the marker as a tie-point for extrapolated dates in the 19th century. Lead isotopes identified leaded gasoline as an important source only in one lake in the second half of the 20th century; its signal was not identified in all other lakes because the lakes were more affected by local and regional inputs. Lead isotopes combined with trace metal fluxes identified a potential marker for coal combustion or urban sources in the second half of the 20th century in southern Ontario, where these sources were significant enough to outweigh leaded gasoline input. The effects of Canadian mining and smelting activities were seen in the trace metal flux profiles of central Ontario lakes; however, these activities were not visible in the Pb isotopes, likely due to mixing of several sources with similar Pb isotopic signatures. This study demonstrates the usefulness of combining lead isotopes and trace metal flux profiles for identifying markers of historical and modern particulate contamination sources, especially in regions where several pollution sources exist.
20 January 2018
Environmental geochemistry of rare earth elements in Cu-porphyry mine tailings in the semiarid climate conditions of Sarcheshmeh mine in southeastern Iran
Publication date: 20 January 2018
Source:Chemical Geology, Volume 477 Author(s): Mehdi Khorasanipour, Zahra Jafari Sarcheshmeh mine is one of the largest Oligo-Miocene porphyry Cu deposits in the world. It is located in the Kerman Cenozoic magmatic arc in southeastern Iran. This paper discusses the geo-environmental behavior of rare earth elements (REEs) in the Sarcheshmeh dammed tailing pond, situated in semiarid climate. For this purpose, solid and water samples were collected to consider: (1) weathering/oxidation reactions and upward migration of soluble elements; (2) super-saturation and formation/dissolution of the secondary evaporative phases; (3) hydro-geochemical changes of the surface and groundwater resources; (4) flotation of the Cu-sulfide ore and tailing management strategies. The mean values of the
20 January 2018
Zinc isotope composition of the Earth and its behaviour during planetary accretion
Publication date: 20 January 2018
Source:Chemical Geology, Volume 477 Author(s): Paolo A. Sossi, Oliver Nebel, Hugh St.C. O'Neill, Fr
20 January 2018
Mineralogical transformation during hydroxyapatite dissolution in simple aqueous solutions
Publication date: 20 January 2018
Source:Chemical Geology, Volume 477 Author(s): S. Boudia, P. Zuddas, F. Fernane, M. Fiallo, P. Sharrock Hydroxyapatite (HAP) is considered to be a stable mineral under surface Earth conditions and adopted as a proxy for paleo-environmental reconstructions and in choice of remediation strategies. A clear description of the solubility properties for HAP is fundamental and can be gained by understanding the basic principals governing the solid-solution interface. In this study we investigated the early stage of HAP dissolution at 25, 50 and 70C using solubility and ATR-FTIR spectroscopy measurements. We found a non-stoichiometric release of calcium and total phosphorus in solution in the experimental close to neutral pH conditions. The ATR-FTIR measurements revealed the presence of new peaks corresponding to the vibrations of HPO4 2
20 January 2018
Sulfur isotope analysis by IC-MC-ICP-MS provides insight into fractionation of thioarsenates during abiotic oxidation
Publication date: 20 January 2018
Source:Chemical Geology, Volume 477 Author(s): Maria K. Ullrich, Faina Gelman, Yevgeni Zakon, Ludwik Halicz, Kay Kn
20 January 2018
Coordination environment of Zn in foraminifera Elphidium aculeatum and Quinqueloculina seminula shells from a polluted site
Publication date: 20 January 2018
Source:Chemical Geology, Volume 477 Author(s): Giovanni De Giudici, Carlo Meneghini, Daniela Medas, Carla Buosi, Pierpaolo Zuddas, Antonella Iadecola, Olivier Mathon, Antonietta Cherchi, Andrei Cristian Kuncser Foraminifera, unicellular organisms that are widespread throughout marine ecosystems, build Ca-carbonate shells that may incorporate trace metals present in the ocean waters because of natural or anthropogenic supply. In this study, we focussed on the trace element Zn, which is abundant in both contaminated and clean waters. We used X-ray and electron spectromicroscopy to investigate the Zn coordinative environment in individual shells of two species of benthic foraminifera, Elphidium aculeatum and Quinqueloculina seminula, that were sampled from a heavy-metal polluted area of Sardinia, Italy. These species synthesise the Ca
20 January 2018
Rapid formation of eclogites during a nearly closed ocean: Revisiting the Pianshishan eclogite in Qiangtang, central Tibetan Plateau
Publication date: 20 January 2018
Source:Chemical Geology, Volume 477 Author(s): Wei Dan, Qiang Wang, William M. White, Xiu-Zheng Zhang, Gong-Jian Tang, Zi-Qi Jiang, Lu-Lu Hao, Quan Ou The Pianshishan eclogites discovered in central Qiangtang are a key piece of evidence constraining the main suture of the Paleo-Tethys Ocean in Tibet. Based on the eclogite-facies metamorphic inclusions found in them, a previous study interpreted the zircon grains as metamorphic in origin, although their catholuminescence images were similar to zircons of igneous origin. Distinguishing metamorphic from igneous zircons can be difficult, however, especially in high-pressure metamorphic rocks. In this study, we report new SIMS zircon U-Pb dates along with zircon O isotope and trace element analyses, to constrain the origin of these zircons and the interpretation of zircon dates. Twenty-five of 26 zircons analyzed from three samples yielded zircon U-Pb dates ranging from 239 to 236Ma with an average of 2381Ma. The zircon rare earth element (REE) patterns are characterized by positive Ce and negative Eu anomalies, strongly indicating an igneous origin. This interpretation is also supported by the high Ti-in-zircon temperatures (>700C) and depleted mantle-like zircon O isotope ratios (5.150.57, 2SD). Thus, we conclude that the protoliths of the Pianshishan eclogites were generated at ~238Ma. Their geochemistry is similar to the oceanic island basalts (OIB), and they were probably generated by small extents partial melting of enriched oceanic asthenospheric mantle within the garnet stability field and emplaced or erupted as a seamount in the Paleo-Tethys Ocean. We infer the age of eclogite-facies metamorphism to be ~233Ma based on previously reported Lu-Hf isochron ages, and that this metamorphism marks the collision between the Southern and Northern Qiangtang terranes. Thus, metamorphism of the eclogites occurred within 5My of protolith generation and exhumation occurred only 13 to 19 My later, based on the 40Ar/39Ar dates of 220214Ma. The time between protolith generation and exhumation was thus <24My. This rare rapid evolution may be due to the protoliths having formed as a petit-spot seamount in response to outer rise flexure as the Paleo-Tethys Ocean entered the Longmu Co-Shuanghu subduction zone.
20 January 2018
Constraints on the uptake of REE by scheelite in the Baoshan tungsten skarn deposit, South China
Publication date: 20 January 2018
Source:Chemical Geology, Volume 477 Author(s): Wen Winston Zhao, Mei-Fu Zhou, Anthony E. Williams-Jones, Zheng Zhao Scheelite is the main ore mineral in skarn-type tungsten deposits, and a common accessory mineral in a variety of rock-types. The Baoshan deposit in South China is one of the most important polymetallic scheelite skarn deposits in China, hosting 40,000t of WO3 with economic concentrations of Zn, Cu, and Ag. It is hosted by a calcic skarn that is zoned outwards mineralogically from garnet-clinopyroxene, through clinopyroxene-garnet, to wollastonite, and overprinted by retrograde minerals. Scheelite occurs in both the prograde and retrograde skarns, and is complexly zoned. On the basis of its textures, the scheelite was classified into three types. Scheelite I and II belong to the early and late prograde stages, respectively, and Scheelite III precipitated during the retrograde stage. The molybdenum (Mo) content of these scheelite types ranges from 54ppm to 24wt%, and the total rare earth element content ranges from 12 to 321ppm. Rare earth element (REE) concentrations and chondrite-normalized REE profiles vary with the distribution of major elements. The profiles indicate variable degrees of REE enrichment, which correlates negatively with the Mo content. Molybdenum-rich scheelite displays a negative Eu anomaly, and Mo-poor scheelite a positive Eu anomaly. Crystal structure provided the first-order control on the minor and trace element composition of the scheelite. Incorporation of REE3+ into scheelite was controlled partly by a coupled substitution involving Mo. The lattice strain model was used to estimate scheelite-fluid partition coefficients for the REE from the contents of these elements in the scheelite and to predict the relative distributions of the REE in the ore-forming fluids. It is proposed that conditions were initially oxidizing, leading to strong incorporation of Mo in Scheelite I, that they became more reducing with the crystallization of Scheelite II containing lesser Mo, and that during retrograde skarn formation there was a return to oxidizing conditions due to an influx of meteoric waters, which altered Scheelite II giving rise to the formation of Scheelite III. The study shows that the composition of scheelite recorded the history of the Baoshan hydrothermal system, and that the behaviour of the REE could be used to quantitatively reconstruct the changing physicochemical conditions during ore formation.

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20 January 2018
The post-mortem history of a bone revealed by its trace element signature: The case of a fossil whale rostrum
Publication date: 20 January 2018
Source:Chemical Geology, Volume 477 Author(s): Sophie Decr
20 January 2018
Mineral inclusion assemblage and detrital zircon provenance
Publication date: 20 January 2018
Source:Chemical Geology, Volume 477 Author(s): Elizabeth A. Bell, Patrick Boehnke, T. Mark Harrison, Matthew M. Wielicki Mineral inclusions are common in magmatic zircon and a potentially rich source of petrologic information. Controls on the relative proportions of inclusion phases, specifically early-crystallizing minerals such as apatite and late-crystallizing phases such as quartz, K-feldspar, and muscovite, have not been systematically studied. For instance, apatite dominates many magmatic zircon inclusion suites, and selective replacement of apatite over other phases has been proposed as a mechanism for generating apatite-poor inclusion assemblages in detrital zircons. However, the extent to which apatite inclusion abundance is influenced by source rock composition has not been established. The preservation of characteristic minerals in granite series, such as differences in magnetite and ilmenite abundances due to varying redox, have also not been systematically explored as inclusion phases in zircon. We surveyed zircon inclusion assemblages in Phanerozoic granitoids of a range of compositions and found a broadly inverse relationship between the presence of apatite in the inclusion suite and whole-rock SiO2 content. Selective loss of apatite is evident from deficits in apatite content among inclusions in contact with cracks in both detrital zircons and some granitoid zircons with independent evidence for fluid ingress (i.e., secondary phases filling open cracks). In cases where microstructural observations can identify primary inclusion assemblages (versus those impacted by fluid ingress), the relative occurrence of apatite can be used to broadly predict source rock SiO2 content. There is little relationship between whole-rock chemistry and the abundance of late-crystallizing phases or the relative proportions of quartz, plagioclase, and alkali feldspar. The presence of ilmenite not in contact with cracks in the host zircon likely points to origins in ilmenite-series (i.e., reduced) magmas, but the presence of magnetite is less diagnostic. Using the apatite abundance metric, detrital Hadean zircons from Jack Hills (Western Australia), appear to derive from felsic rather than intermediate or mafic granitoids and detrital Eoarchean zircons from Nuvvuagittuq Supracrustal Belt (Quebec) may derive from intermediate to felsic granitoids. No Fe-Ti oxides have been identified in Nuvvuagittuq zircons, but rare ilmenite in Jack Hills zircons points to origins of at least some part of the population in ilmenite-series magmas.
20 January 2018
Spatial and temporal variability in Marquesas Islands volcanism revealed by 3He/4He and the composition of olivine-hosted melt inclusions
Publication date: 20 January 2018
Source:Chemical Geology, Volume 477 Author(s): Kevin Konrad, David W. Graham, Adam J.R. Kent, Anthony A.P. Koppers The Marquesas Islands are a volcanic chain having an oblique orientation to Pacific plate motion. They represent the surface manifestation of a mantle hotspot having a low melt flux and a large intrinsic chemical and isotopic heterogeneity. Here we provide new helium isotope data for olivine separated from 23 basalts and one gabbroic xenolith, plus whole rock major and trace element data for the same lavas. We also carried out trace element analyses of 41 olivine-hosted melt inclusions (OHMIs) from 15 of the basalts, and 40Ar/39Ar age determinations for basalt groundmass from the islands of Fatu Hiva and Hiva Oa. 3He/4He shows a large range of values from <5 RA up to 14.5 RA. Elevated 3He/4He ratios >9 RA are found at Nuku Hiva and Hiva Oa near the center of the archipelago, in agreement with previous findings (Castillo et al., 2007). The new ages for the Hiva Oa lavas indicate that 3He/4He increases from ~8 RA to 14.5 RA during the mid-late shield stage of volcanism (2.62.0Ma), followed by a decrease during the post-shield stage (<1.8Ma) after collapse of the Temetiu caldera. Lavas from Fatu Hiva, Ua Huka, Ua Pou, Tahuata and Motane have 3He/4He<8.3 RA, with values typically between 5 and 7 RA. Incompatible element ratios observed in the OHMIs show more variability than what is observed in the lavas because they represent a less extensive aggregation of melts derived from small scale chemical heterogeneities within the Marquesas mantle plume. The Cl/K ratio of OHMIs ranges from 0.02 to 0.4, potentially due to both mantle source heterogeneity and assimilation of brine or seawater-altered rocks at crustal levels. The geographic distribution of 3He/4He suggests the mantle plume is concentrically zoned in He isotope composition, with high 3He/4He material concentrated near its central axis that is sourced from hot, primitive material entrained near the core-mantle boundary region.
Available online 17 January 2018
Illitization decrypted by B and Li isotope geochemistry of nanometer-sized illite crystals from bentonite beds, East Slovak Basin
Publication date: 20 January 2018
Source:Chemical Geology, Volume 477 Author(s): Norbert Clauer, Lynda B. Williams, Damien Lemarchand, Pierre Florian, Miroslav Honty Boron and lithium contents and isotopic compositions were determined in nucleating and growing nanometer-sized illite crystals (<0.02 to 0.2
Available online 16 January 2018
The relationship between Mn oxidation state and structure in triclinic and hexagonal birnessites
Publication date: Available online 17 January 2018
Source:Chemical Geology Author(s): Florence T. Ling, Jeffrey E. Post, Peter J. Heaney, Eugene S. Ilton Because of their nanocrystallinity and high cation exchange capacities, birnessite phases can control the cycling of heavy metals in soils and groundwaters, and they also are implicated in the oxidation of transition metals in natural environments. Birnessite reactivity is determined by crystal structure and composition. Because birnessites typically are poorly crystalline, synchrotron-based absorption spectroscopy (EXAFS, XANES) often is utilized for structural characterization. For example, linear combination fitting (LCF) of X-ray absorption spectra typically is applied to quantify mixed triclinic and hexagonal birnessite phases. This approach is challenged, however, because the structures of the standards are not always plainly apparent. Moreover, it is difficult to distinguish birnessites with nanoscale intergrowths of hexagonal and triclinic endmembers from homogeneous birnessite structures of intermediate triclinicity. We explored these issues by synthesizing a host of cation-exchanged birnessite specimens whose long-range symmetrical character could be determined by X-ray diffraction without ambiguity. Through a combination of Fourier transform infrared spectroscopy (FTIR), extended X-ray absorption fine structure (EXAFS), and X-ray photoelectron spectroscopy (XPS), we have examined the relationships among structural symmetry, Mn oxidation state, and interlayer composition. Our results confirm prior models that as the concentration of Mn3+ increases, the departure from hexagonal symmetry also increases. Rietveld refinements indicate that the Jahn-Teller distortions associated with Mn3+ induce systematic variations in unit-cell parameters, particularly an increase in the a-axis and the
Available online 12 January 2018
Transport of rare earth elements by hydrocarbon-bearing brines: Implications for ore deposition and the use of REEs as fluid source tracers
Publication date: Available online 16 January 2018
Source:Chemical Geology Author(s): Pilar Lecumberri-Sanchez, Mohammed Bouabdellah, Oussama Zemri Low-temperature (100160
Available online 12 January 2018
The use of dithiothreitol for the quantitative analysis of elemental sulfur concentrations and isotopes in environmental samples
Publication date: Available online 12 January 2018
Source:Chemical Geology Author(s): Martin R. Kurek, William P. Gilhooly, Gregory K. Druschel, Molly D. O'Beirne, Josef P. Werne Determining the concentration and isotopic composition of elemental sulfur in modern and ancient environments is essential to improved interpretation of the mechanisms and pathways of sulfur utilization in biogeochemical cycles. Elemental sulfur can be extracted from sediment or water samples and quantified by converting to hydrogen sulfide. Alternatively, elemental sulfur concentrations can themselves be analyzed using HPLC and other methodologies; however, the preparation and analysis times can be long and these methods are not amenable to stable isotopic analysis. Current reduction methods involve the use of costly and specialized glassware in addition to toxins such as chromium chloride or cyanide to reduce the sulfur to hydrogen sulfide. The novel reduction method presented here uses dithiothreitol (DTT) as a less toxic reducing agent to obtain both elemental sulfur concentrations and isotopic composition from the same sample. The sample is dissolved in an aqueous or organic liquid medium and upon reaction with DTT, the elemental sulfur is volatilized as hydrogen sulfide and collected in a sulfide trap using an inexpensive gas extraction apparatus. The evolved sulfide concentrations can easily be measured for concentration, by absorbance spectrophotometery or voltammetry techniques, and then analyzed for sulfur isotopic composition. The procedure is quantitative at >93% recovery to dissolved elemental sulfur with no observed sulfur isotope fractionation during reduction and recovery. Controlled experiments also demonstrate that DTT is not reactive to sulfate, sulfite, pyrite, or organic sulfur.
Available online 12 January 2018
Mantle sources of kimberlites through time: A U-Pb and Lu-Hf isotope study of zircon megacrysts from the Siberian diamond fields
Publication date: Available online 12 January 2018
Source:Chemical Geology Author(s): Jing Sun, Sebastian Tappe, Sergey I. Kostrovitsky, Chuan-Zhou Liu, Sergey Yu. Skuzovatov, Fu-Yuan Wu A comprehensive, internally consistent U-Pb and Lu-Hf isotope data set for 93 mantle-derived zircons from the Yakutian kimberlite province confirms and further refines the four major episodes of kimberlite magmatism on the Siberian craton: 421409
Available online 11 January 2018
Distribution of Rb, Ga and Cs in agricultural land soils at European continental scale (GEMAS): Implications for weathering conditions and provenance
Publication date: Available online 12 January 2018
Source:Chemical Geology Author(s): Philippe N
Available online 11 January 2018
Bulk solubility and speciation of H2O in silicate melts
Publication date: Available online 11 January 2018
Source:Chemical Geology Author(s): G. Ottonello, P. Richet, P. Papale The bulk solubility and speciation of H2O in silicate melts of virtually any composition is predicted from first principles with a satisfactory precision. The solubility of molecular water is first predicted from the Scaling Particle Theory (SPT) coupled with an ab initio assessment of the electronic, dispersive and repulsive energy terms based on the Polarized Continuum Model (PCM). The Silver-Stolper ideal homogeneous speciation model is then applied to compute the fractional molar amount of neutral hydroxyl functionals [OH] in the melt and the computed [OH] amount is added to the molecular form [OH2]. The Hydrogen Bonding (HB) electrostatic contributions to the stabilization of molecular water [OH2] in solution are then resolved through an inverse non-linear minimization procedure on the basis of an extended dataset (970 samples) of experiments concerning the H2O saturation hyper-surface carried out in the last half century. The Gibbs free energy of solution
Available online 10 January 2018
Combined dating of goethites and kaolinites from ferruginous duricrusts. Deciphering the Late Neogene erosion history of Central Amazonia
Publication date: Available online 11 January 2018
Source:Chemical Geology Author(s): Thierry Allard, C
Available online 9 January 2018
Wollastonite carbonation in water-bearing supercritical CO2: Effects of water saturation conditions, temperature, and pressure
Publication date: Available online 10 January 2018
Source:Chemical Geology Author(s): Yujia Min, Young-Shin Jun The carbonation of silicates in water-bearing supercritical CO2 (scCO2) can affect the performance of CO2-enhanced subsurface operation. This study investigated the effects of water, temperature, and pressure on the carbonation of wollastonite (CaSiO3) in water-bearing scCO2 at 3593
Available online 8 January 2018
Carbonate speciation in depolymerized and polymerized (alumino)silicate glasses: Constraints from 13C MAS and static NMR measurements and ab initio calculations
Publication date: Available online 9 January 2018
Source:Chemical Geology Author(s): Xianyu Xue, Masami Kanzaki, Paul Floury, Tsubasa Tobase, James Eguchi Knowledge of the dissolution mechanisms of carbon dioxide in silicate melts/glasses is indispensable for understanding its effects on physical and thermodynamic properties. Carbon dioxide is generally known to dissolve as molecular CO2 and CO3 2 species, with the latter dominant for depolymerized compositions. However, less is agreed upon about how the CO3 2 groups are incorporated, especially for depolymerized silicate melt compositions relevant to natural mafic and ultramafic magmas. Here we report 13C MAS and static NMR results on a series of 13CO2-bearing glasses (quenched from melts) of diverse silicate compositions, including nominally fully polymerized sodium aluminosilicate and calcium aluminosilicate, depolymerized sodium silicate and sodium aluminosilicate, and depolymerized calcium
Available online 7 January 2018
Controls on magnesium, manganese, strontium, and barium concentrations recorded in freshwater mussel shells from Ohio
Publication date: Available online 8 January 2018
Source:Chemical Geology Author(s): Thomas J. Geeza, David P. Gillikin, David H. Goodwin, Scott D. Evans, Thomas Watters, Nathaniel R. Warner Freshwater bivalve shells may record inter-annual fluctuations in water chemistry, which in turn may archive variations in solute load due to pollution or discharge events. Here, using weekly surface water chemistry collected at two locations and shells of Lampsilis cardium grown in the surface water we investigate if the Mg/Ca, Mn/Ca, Sr/Ca, and Ba/Ca ratios measured at high resolution in the shells on an intra-annual time scale consistently reflect the chemistry of the surface water. Two relationships appear highly correlated, Sr/Cacarb and Sr/Cawater, and Mn/Cacarb and temperature. Ba/Cacarb correlated strongly with Ba/Cawater in one shell but temperature in another shell yielding inconclusive results. Mn/Cacarb and Mg/Cacarb were not strongly correlated with elemental ratios in the water, but Mn/Cacarb did show variable, weak to moderate correlation with pH. We found consistent partition coefficient (DMe) values between individual shell samples grown in the same water with mean DMg
Available online 6 January 2018
Evaluating baddeleyite oxygen isotope analysis by secondary ion mass spectrometry (SIMS)
Publication date: Available online 7 January 2018
Source:Chemical Geology Author(s): J.H.F.L. Davies, R.A. Stern, L.M. Heaman, D.E. Moser, E.L. Walton, T. Vennemann Two baddeleyite megacrysts were evaluated as potential reference materials (RMs) for SIMS oxygen isotope analysis, and utilized to understand and calibrate instrumental mass fractionation (IMF). A baddeleyite crystal (S0045) from the Phalaborwa carbonatite, South Africa has a mean
Available online 6 January 2018
Determination of Fe3+/
5 January 2018
Tracing metal sources in peribatholitic hydrothermal W deposits based on the chemical composition of wolframite: The example of the Variscan French Massif Central
Publication date: Available online 6 January 2018
Source:Chemical Geology Author(s): Matthieu Harlaux, Julien Mercadier, Christian Marignac, Chantal Peiffert, Christophe Cloquet, Michel Cuney We present a complete dataset for major, minor and trace elements in wolframite ([Fe,Mn]WO4) based on the example of several peribatholitic hydrothermal W deposits located in the Variscan French Massif Central (FMC). The wolframite samples were characterized down to the micrometer scale by combining scanning electron microscopy observations and in situ chemical analysis by electron probe microanalyzer and laser ablation inductively coupled plasma mass spectrometry. Most samples are Fe-dominated wolframites and are characterized by variable Fe/(Fe+Mn) values for the studied deposits (from 0.36 to 0.86) without significant alteration features. Wolframites present intracrystalline variations for concentrations of several minor and trace elements, principally for Nb, Ta, and Sn, which reflect growth zoning. The minor and trace element compositions of the different wolframite samples show at first order similar enrichments in Ta, Nb, Sn, Zn, and In, as well as depletions in LREE, Li, Th, Ti, Zr, Hf, Pb, V, Co, and Mg, compared to the upper continental crust. Second order compositional variations are observed between the studied deposits, which can be separated in four main regional geochemical groups. This work highlights that the chemical composition of wolframite is controlled by both the crystallochemical parameters and the composition of the primary hydrothermal fluid. The regional variations observed in the geochemical signatures of wolframite reflect local variations in the composition of the hydrothermal fluid, i.e. variable metal sources. Therefore, this suggests that the minor and trace element contents in wolframite likely represent direct markers of the source of the hydrothermal fluid and ultimately of the metals. The comparison between the trace element compositions of wolframite with the compositions of regional granitic rocks and worldwide shales suggests that evolved peraluminous granites represent the main source of metals in peribatholitic hydrothermal W deposits from the FMC, whereas metasedimentary rocks have a limited to no influence on the metal budget.
5 January 2018
Editorial Board
Publication date: 5 January 2018
Source:Chemical Geology, Volume 476

5 January 2018
Gold diffusion into and out of quartz-hosted fluid inclusions during re-equilibration experiments at 600800C and 2kbar
Publication date: 5 January 2018
Source:Chemical Geology, Volume 476 Author(s): Haihao Guo, Andreas Aud
5 January 2018
Effect of water and solid activities at high pressure on supercritical CO2 sequestration in saline aquifers
Publication date: 5 January 2018
Source:Chemical Geology, Volume 476 Author(s): Yasmin A. Abdelraouf, Robert K. Niven This study presents a multiphase (water, supercritical fluid and solid species) thermodynamic model applicable to the sequestration of supercritical CO2 in a saline aquifer at high pressures, which accounts for the effects of water activity, solid activity, supercritical fluid fugacity and aqueous species activities. The model is formulated using mass action laws, species and charge balances, a new correlation for species activity coefficients based on the Davies equation, supercritical fluid fugacities (Peng-Robinson equation of state), water activity (a new explicit form in terms of state variables and salinity), corrected equilibrium constants of aqueous reactions as functions of pressure, temperature and salinity, water-supercritical partitioning (Krichevsky-Ilinskaya correction to Henry's law), and a new model for water-solid partitioning. The effects of high pressures to 60MPa consistent with sequestration at depths to 6000m are examined in detail. The model is applied to the scCO2 - H2O - CaCO3(s) - Na+ - Cl
5 January 2018
Geochemical composition of Aeolian dust and surface deposits from the Qatar Peninsula
Publication date: 5 January 2018
Source:Chemical Geology, Volume 476 Author(s): Oguz Yigiterhan, Balint Z. Alfoldy, Mariasilvia Giamberini, Jesse C. Turner, Ebrahim S. Al-Ansari, Mohamed A. Abdel-Moati, Ibrahim A. Al-Maslamani, Mohamed M. Kotb, Elnaiem A. Elobaid, Hassan M. Hassan, Jeffrey P. Obbard, James W. Murray The trace metal geochemistry of atmospheric dust and terrestrial surface particles were studied on the Qatar Peninsula from February 2014 to November 2015. We included samples of the mega dust-storm event on 0102 April 2015. Atmospheric dust samples were collected using passive dust traps. Terrestrial surface deposits of recent dust accumulation and traffic particulate from roads were also sampled. All samples were total acid digested and analyzed for major and trace elements using ICP-OES analyzer. The concentration of thirteen elements (Ca, Mg, Ag, As, Cd, Cr, Cu, Mo, Ni, Se, Sn, Sr, Zn) were enriched in atmospheric dust samples, relative to upper continental crust (UCC). Calcium was especially enriched by up to 435% relative to UCC. About 33% of the total sample mass was CaCO3, reflecting the composition of surface rocks and soils in the source areas. Of the elements typically associated with anthropogenic activity, Ag, Ni, and Zn were most enriched relative to UCC, with enrichment factors (EF) of 182%, 233%, and 209%, respectively. Other metals, which normally reflect anthropogenic sources, including Pb and V, were not significantly enriched, with enrichment factors of 25% and 3%, respectively. Major elements (Al, Mn, Fe) were depleted (
5 January 2018
Changes in the structure of birnessite during siderophore-promoted dissolution: A time-resolved synchrotron X-ray diffraction study
Publication date: 5 January 2018
Source:Chemical Geology, Volume 476 Author(s): Timothy B. Fischer, Peter J. Heaney, Jeffrey E. Post We used time-resolved synchrotron X-ray diffraction to follow the complete dissolution of synthetic triclinic Na-birnessite as promoted by the trihydroxamate siderophore desferrioxamine B (DFOB). Many microorganisms employ siderophores to increase the availability of Fe, Mn, and other trace metals for metabolic processes. Our primary goal was to quantify the DFOB-assisted dissolution rate by direct, continuous observation of the solid phase. Our kinetic model indicates that the rate of dissolution is dependent on [DFOB] but not pH, and has a reaction order of 0.505 with a rate constant of 0.112wt%birnmin

Biological and chemical processes of microbially mediated nitrate-reducing Fe(II) oxidation by Pseudogulbenkiania sp. strain 2002
Publication date: 5 January 2018
Source:Chemical Geology, Volume 476 Author(s): Dandan Chen, Tongxu Liu, Xiaomin Li, Fangbai Li, Xiaobo Luo, Yundang Wu, Ying Wang In the microbially mediated nitrate-reducing Fe(II) oxidation system, it is recognized that chemical oxidation of Fe(II) by nitrite, which is a bioreduction intermediate of nitrate, can occur under anoxic conditions (chemodenitrification), but it is still difficult to quantitatively evaluate the contributions of biological Fe(II) oxidation and chemodenitrification. Here, nitrate reduction coupled with Fe(II) oxidation by a suggested lithoautotrophic nitrate-reducing Fe(II)-oxidizing bacterium, Pseudogulbenkiania sp. strain 2002, was investigated in PIPES buffered medium without any organic cosubstrate through reaction kinetics, nitrogen isotope fractionation, and secondary mineral characterization. Substantial Fe(II) oxidation was observed in the presence of cells and nitrate, and nitrite (0.59mM) was able to quickly oxidize Fe(II). Stored carbon in strain 2002 harvested during pre-incubation can serve as carbon source for nitrate reduction. Furthermore, the N isotopic composition (
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