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Article ; Online: Natural stable calcium isotope ratios: a new gold standard for bone balance?

Hill Gallant, Kathleen M / Zheng, Xin-Yuan

2022 Volume 102, Issue 3, Page(s) 473–476

Abstract: Bone calcium balance is the net gain, loss, or equilibrium of calcium moving to and from bone, which reflects bone balance. There are currently no clinically available tools for measuring real-time bone balance. In this issue, Shroff et al. demonstrate ... ...

Abstract	Bone calcium balance is the net gain, loss, or equilibrium of calcium moving to and from bone, which reflects bone balance. There are currently no clinically available tools for measuring real-time bone balance. In this issue, Shroff et al. demonstrate the use of natural stable calcium isotope ratios as a novel biomarker of bone balance in children with chronic kidney disease on dialysis that is highly repeatable and associated with radiological and biochemical markers of bone metabolism.
MeSH term(s)	Bone and Bones/diagnostic imaging ; Bone and Bones/metabolism ; Calcium/metabolism ; Calcium Isotopes ; Calcium, Dietary ; Child ; Humans ; Renal Dialysis
Chemical Substances	Calcium Isotopes ; Calcium, Dietary ; Calcium (SY7Q814VUP)
Language	English
Publishing date	2022-08-18
Publishing country	United States
Document type	Journal Article ; Comment
ZDB-ID	120573-0
ISSN	1523-1755 ; 0085-2538
ISSN (online)	1523-1755
ISSN	0085-2538
DOI	10.1016/j.kint.2022.06.017
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Article ; Online: Comprehensive metabolome characterization and comparison between two sources of Dragon's blood by integrating liquid chromatography/mass spectrometry and chemometrics.

Lou, Jia / Xu, Xiao-Yan / Xu, Bei / Wang, Hong-da / Li, Xue / Sun, He / Zheng, Xin-Yuan / Zhou, Jun / Zou, Ya-Dan / Wu, Hong-Hua / Wang, Yue-Fei / Yang, Wen-Zhi

Analytical and bioanalytical chemistry

2024 Volume 416, Issue 7, Page(s) 1571–1587

Abstract: Dragon's Blood (DB) serves as a precious Chinese medicine facilitating blood circulation and stasis dispersion. Daemonorops draco (D. draco; Qi-Lin-Jie) and Dracaena cochinchinensis (D. cochinchinenesis; Long-Xue-Jie) are two reputable plant sources for ... ...

Abstract	Dragon's Blood (DB) serves as a precious Chinese medicine facilitating blood circulation and stasis dispersion. Daemonorops draco (D. draco; Qi-Lin-Jie) and Dracaena cochinchinensis (D. cochinchinenesis; Long-Xue-Jie) are two reputable plant sources for preparing DB. This work was designed to comprehensively characterize and compare the metabolome differences between D. draco and D. cochinchinenesis, by integrating liquid chromatography/mass spectrometry and untargeted metabolomics analysis. Offline two-dimensional liquid chromatography/ion mobility-quadrupole time-of-flight mass spectrometry (2D-LC/IM-QTOF-MS), by utilizing a powerful hybrid scan approach, was elaborated for multicomponent characterization. Configuration of an XBridge Amide column and an HSS T3 column in offline mode exhibited high orthogonality (A
MeSH term(s)	Chemometrics ; Metabolome ; Mass Spectrometry ; Chromatography, Liquid ; Chromatography, High Pressure Liquid/methods ; Plant Extracts
Chemical Substances	dragon's blood (M3YJ2C28IC) ; Plant Extracts
Language	English
Publishing date	2024-01-27
Publishing country	Germany
Document type	Journal Article
ZDB-ID	201093-8
ISSN	1618-2650 ; 0016-1152 ; 0372-7920
ISSN (online)	1618-2650
ISSN	0016-1152 ; 0372-7920
DOI	10.1007/s00216-024-05159-2
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Article: Determination of Picogram-per-Gram Concentrations of ²³¹Pa and ²³⁰Th in Sediments by Melt Quenching and Laser Ablation Mass Spectrometry

Zheng, Jianfan / Chen, Tianyu / Ng, Hong Chin / Robinson, Laura F. / Zheng, Xin-Yuan / Shi, Xuefa / Huang, Mu

Analytical chemistry. 2022 May 16, v. 94, no. 21

2022

Abstract: Uranium, thorium, and protactinium radionuclides in marine sediments are important proxies for understanding the earth’s environmental evolution. Conventional solution-based methods, which typically involve isotope spike preparation, concentrated acid ... ...

Abstract	Uranium, thorium, and protactinium radionuclides in marine sediments are important proxies for understanding the earth’s environmental evolution. Conventional solution-based methods, which typically involve isotope spike preparation, concentrated acid sample digestion, column chemistry, and mass spectrometry, allow precise but time-consuming and costly measurements of these nuclide concentrations (i.e., ²³⁰Th and ²³¹Pa). In this work, we have established an efficient method for ²³⁰Th and ²³¹Pa measurement of marine sediments down to the picogram-per-gram level without purification and enrichment. Our method first transforms a small amount of thermally decomposed sediments (∼0.1–0.2 g) to homogeneous silicate glass using a melt quenching technique and then analyzes the glass with laser ablation multicollector inductively coupled plasma–mass spectrometry. Standard sample bracketing with isotope-spike-calibrated glass standards prepared in this study was used to correct for instrumental fractionation during measurement. It is demonstrated that our method can accurately determine the U–Th–Pa concentrations of typical marine sediments in the late Pleistocene with precision of a few percent. Compared with the conventional solution-based methods, the turnover time of sample preparation and measurement with our established protocol is greatly reduced, facilitating future application of U-series radionuclides in reconstructing oceanic processes at high temporal and spatial resolution.
Keywords	Pleistocene epoch ; analytical chemistry ; fractionation ; glass ; isotopes ; mass spectrometry ; protactinium ; silicates ; thorium ; uranium
Language	English
Dates of publication	2022-0516
Size	p. 7576-7583.
Publishing place	American Chemical Society
Document type	Article
ZDB-ID	1508-8
ISSN	1520-6882 ; 0003-2700
ISSN (online)	1520-6882
ISSN	0003-2700
DOI	10.1021/acs.analchem.2c00438
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Article: Geochemistry and Cosmochemistry of Potassium Stable Isotopes.

Wang, Kun / Li, Weiqiang / Li, Shilei / Tian, Zhen / Koefoed, Piers / Zheng, Xin-Yuan

Chemie der Erde : Beitrage zur chemischen Mineralogie, Petrographie und Geologie

2021 Volume 81, Issue 3

Abstract: Stable potassium isotopes are one of the emerging non-traditional isotope systems enabled in recent years by the advance of Multi-Collector Inductively-Coupled-Plasma Mass-Spectrometry (MC-ICP-MS). In this review, we first summarize the geochemical and ... ...

Abstract	Stable potassium isotopes are one of the emerging non-traditional isotope systems enabled in recent years by the advance of Multi-Collector Inductively-Coupled-Plasma Mass-Spectrometry (MC-ICP-MS). In this review, we first summarize the geochemical and cosmochemical properties of K, its major reservoirs, and the analytical methods of K isotopes. Following this, we review recent literature on K isotope applications in the fields of geochemistry and cosmochemistry. Geochemically, K is a highly incompatible lithophile element, and a highly soluble, biophile element. The isotopic fractionation of K is relatively small during magmatic processes such as partial melting and fractional crystallization, whereas during low-temperature and biological processes fractionation is considerably larger. This resolvable fractionation has made K isotopes promising tracers for a variety of Earth and environmental processes, including chemical weathering, low-temperature alteration of igneous rocks, reverse weathering, and the recycling of sediments into the mantle during subduction. Sorption and interactions of aqueous K with different clay minerals during cation exchange and clay formation are likely to be of fundamental significance in generating much of the K isotope variability seen in samples from the Earth surface and samples carrying recycled surface materials from the deep Earth. The magnitude of this fractionation is process- and mineral-dependent. Comprehensive quantification of pertinent K isotope fractionation factors is currently lacking and urgently needed. Significant fractionation during biological activities, such as plant uptake, demonstrates the potential utility of K isotopes in the study of the nutrient cycle and its relation to the climate and various ecosystems, enabling new and largely unexplored avenues for future research. Of significant importance to the cosmochemistry community, K is a moderately volatile element with large variations in K/U ratio observed among chondrites and planetary materials. As this indicates different degrees of volatile depletion, it has become a fundamental chemical signature of both chondritic and planetary bodies. This volatile depletion has been attributed to various processes such as solar nebula condensation, mixing of volatile-rich and -poor reservoirs, planetary accretional volatilization via impacts, and/or magma ocean degassing. While K isotopes have the potential to distinguish these different processes, the current results are still highly debated. A good correlation between the K isotope compositions of four differentiated bodies (Earth, Mars, Moon, and Vesta) and their masses suggests a ubiquitous volatile depletion mechanism during the formation of the terrestrial planets. It is still unknown whether any of the K isotopic variation among chondrites and differentiated bodies can be attributed to inherited signatures of mass-independent isotopic anomalies.
Language	English
Publishing date	2021-06-09
Publishing country	Germany
Document type	Journal Article
ZDB-ID	1505-2
ISSN	0009-2819
ISSN	0009-2819
DOI	10.1016/j.chemer.2021.125786
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Article ; Online: Determination of Picogram-per-Gram Concentrations of

Zheng, Jianfan / Chen, Tianyu / Ng, Hong Chin / Robinson, Laura F / Zheng, Xin-Yuan / Shi, Xuefa / Huang, Mu

Analytical chemistry

2022 Volume 94, Issue 21, Page(s) 7576–7583

Abstract: Uranium, thorium, and protactinium radionuclides in marine sediments are important proxies for understanding the earth's environmental evolution. Conventional solution-based methods, which typically involve isotope spike preparation, concentrated acid ... ...

Abstract	Uranium, thorium, and protactinium radionuclides in marine sediments are important proxies for understanding the earth's environmental evolution. Conventional solution-based methods, which typically involve isotope spike preparation, concentrated acid sample digestion, column chemistry, and mass spectrometry, allow precise but time-consuming and costly measurements of these nuclide concentrations (i.e.,
MeSH term(s)	Isotopes/analysis ; Laser Therapy ; Mass Spectrometry/methods ; Protactinium ; Thorium/analysis
Chemical Substances	Isotopes ; Protactinium (0S6855V29M) ; Thorium (60YU5MIG9W)
Language	English
Publishing date	2022-05-16
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	1508-8
ISSN	1520-6882 ; 0003-2700
ISSN (online)	1520-6882
ISSN	0003-2700
DOI	10.1021/acs.analchem.2c00438
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Article: Early Archean biogeochemical iron cycling and nutrient availability: New insights from a 3.5 Ga land-sea transition

Johnson, Clark M. / Zheng, Xin-Yuan / Djokic, Tara / Van Kranendonk, Martin J. / Czaja, Andrew D. / Roden, Eric E. / Beard, Brian L.

Earth-science reviews. 2022 Mar. 10,

2022

Abstract: The chemical and isotopic compositions of Precambrian Fe-rich chemical sedimentary rocks have figured prominently in discussions on the Fe biogeochemical cycle and redox conditions in the early Earth. Broad trends of decreasing δ⁵⁶Fe values for Eoarchean ...

Abstract	The chemical and isotopic compositions of Precambrian Fe-rich chemical sedimentary rocks have figured prominently in discussions on the Fe biogeochemical cycle and redox conditions in the early Earth. Broad trends of decreasing δ⁵⁶Fe values for Eoarchean to Paleoproterozoic iron formations (IFs) and jaspilites (hematite-chert) with decreasing age reflect a general increase in extent of oxidation of aqueous Fe(II) (Fe(II)ₐq) in marine environments, consistent with increasing oxygenation of surface environments, particularly since the Mesoarchean. Such trends may record a shift from anaerobic to aerobic oxidation, in part reflecting increasing nutrient abundances that follow increased emergence of continental crust. It is commonly proposed that the size of the biosphere in the early Archean was largely nutrient limited, specifically P limited. Highly positive δ⁵⁶Fe values for Fe oxides in chemical sedimentary rocks deposited in open marine environments at this time are consistent with excess Fe(II)ₐq. Here, we present new data on Fe isotopes and trace element chemistry for 3.4–3.5 Ga jaspilites from the North Pole region of the Pilbara Craton, including the first example of a land-sea transition preserved in the lower Dresser Formation as jaspilite deposition in restricted basin and open-marine settings. A review of the possible mechanisms of Fe(II)ₐq oxidation in the early Archean - including O₂ generated by oxygenic photosynthesis, UV photo-oxidation, or photoferrotrophy (anoxygenic photosynthesis) - suggests that the latter is most likely, in light of evidence for low-O₂ contents and the strong role that silica plays in inhibiting abiologic Fe(II) oxidation. Y + REE contents of lower Dresser Formation jaspilites indicate a freshwater component in the restricted basin settings, in contrast to exclusively seawater components in the open-marine environments. δ⁵⁶Fe values for open-marine jaspilites are highly positive. (δ⁵⁶Fe ~ +1 to +2.4‰), similar to other jaspilites and IFs of Eoarchean to Paleoarchean age. Assuming photoferrotrophy as the oxidative pathway, this would indicate electron donor (Fe(II)ₐq) excess and nutrient limitation. For the restricted-basin jaspilites of the lower Dresser Formation, δ⁵⁶Fe values extend to slightly negative values (δ⁵⁶Fe ~ −0.4‰), correlating with changes in Y + REE contents that indicate fluid mixing. In toto, there is a range of ~3‰ in δ⁵⁶Fe values across the land-sea transition of the lower Dresser Formation, significantly exceeding the range previously measured in early Archean jaspilites. Combined with an advection-dispersion-reaction model for Fe(II)ₐq oxidation via photoferrotrophy, these observations suggest a range of nutrient abundance with environment, where samples from near-shore or restricted settings record excess nutrients from terrestrial input and hence electron donor limitation. Integrating the new results from the Pilbara Craton with the broader Fe isotope database for Eoarchean through Paleoarchean jaspilites and IFs, as well as a simple mass-balance model relating δ⁵⁶Fe values and P contents, it becomes apparent that the relatively high nutrient abundance seen only in restricted settings at ~3.5 Ga becomes more characteristic of the open oceans by ~3.2 Ga. This expansion of nutrient availability is correlated with a marked increase in ⁸⁷Sr/⁸⁶Sr ratios for seawater, which can be shown to be a proxy for P delivery to the open oceans from the continents via weathering fluxes. Collectively, these findings demonstrate the importance of considering geologic context in interpreting Fe isotope and chemical compositions of jaspilites and IFs. Capture of the land-sea transition of the lower Dresser Formation provides insights into the biosphere that would have been missed in sample suites that only record open-marine conditions.
Keywords	Eoarchean era ; Mesoarchean era ; Paleoarchean era ; Paleoproterozoic era ; basins ; biogeochemical cycles ; biosphere ; databases ; freshwater ; models ; nutrient availability ; photooxidation ; photosynthesis ; seawater ; silica ; Arctic region
Language	English
Dates of publication	2022-0310
Publishing place	Elsevier B.V.
Document type	Article
Note	Pre-press version
ZDB-ID	1792-9
ISSN	0012-8252
ISSN	0012-8252
DOI	10.1016/j.earscirev.2022.103992
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: Constraining silicon isotope exchange kinetics and fractionation between aqueous and amorphous Si at room temperature

Zheng, Xin-Yuan / Beard, Brian L. / Johnson, Clark M.

2019

Abstract: Silicon (Si) isotopes are useful tracers for the modern and ancient Si cycle, but their interpretation is limited by inadequate understanding of Si isotope exchange kinetics and fractionation factors at low temperature. This study investigated Si isotope ...

Abstract	Silicon (Si) isotopes are useful tracers for the modern and ancient Si cycle, but their interpretation is limited by inadequate understanding of Si isotope exchange kinetics and fractionation factors at low temperature. This study investigated Si isotope exchange and fractionation between aqueous and amorphous Si at circumneutral pH and room temperature through a series of 29Si-spiked isotope-exchange experiments. Four different amorphous Si solids with varied surface areas were reacted with aqueous Si solutions of high ionic strength similar to seawater, or low ionic strength typical of freshwater, under conditions close to chemical equilibrium with respect to amorphous Si solubility. In contrast to the common perception of negligible Si isotope exchange at low temperature, ∼50–85% isotope exchange was achieved between aqueous and amorphous Si within ∼60 days. Larger solid surface areas and higher aqueous ionic strength generally promoted Si isotope exchange. Drying/aging of Si gel, however, impedes Si isotope exchange between amorphous and aqueous Si relative to freshly prepared Si gels. Excluding the experiments that used the aged Si gel, temporal trajectories of Si isotope evolution of the two phases from all other experiments showed significant curvature in three-isotope space (29Si/28Si and 30Si/28Si). These results can be best explained by a model that comprises two Si isotope exchange processes with different exchange rates and fractionation factors during the interactions between aqueous and amorphous Si towards isotope equilibrium. The faster exchange is associated with surface sites, and slower exchange occurs between exterior and interior Si atoms of the solid. Exchange with surface sites tends to partition heavy Si isotopes in the aqueous phase relative to the solid surface, whereas exchange between surface and interior sites in the solid tends to enrich heavy Si isotopes in the interior. Two experiments that achieved >80% isotope exchange provided the best estimates of equilibrium Si isotope ...
Subject code	541
Language	English
Publisher	Elsevier
Publishing country	de
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Stable potassium (K) isotope characteristics at mid-ocean ridge hydrothermal vents and its implications for the global K cycle

Zheng, Xin-Yuan / Beard, Brian L. / Neuman, Mason / Fahnestock, Maria F. / Bryce, Julia G. / Johnson, Clark M.

2022

Abstract: Highlights • Potassium isotopes of modern hydrothermal fluids are reported for the first time. • Potassium isotope fractionation in hydrothermal systems is resolved and quantified. • Hydrothermal systems cannot explain the heavy K isotope signature of ... ...

Abstract	Highlights • Potassium isotopes of modern hydrothermal fluids are reported for the first time. • Potassium isotope fractionation in hydrothermal systems is resolved and quantified. • Hydrothermal systems cannot explain the heavy K isotope signature of seawater. • Authigenic clay formation likely has a significant role in the global K cycle. Recent discoveries of significant variations in stable K isotope ratios (41K/39K or K) among various terrestrial samples indicate that K isotopes can be a novel tracer for the global K cycle, but a key observation that seawater K is ‰ higher than the bulk silicate Earth remains unexplained. An unconstrained component critical to this puzzle is hydrothermal systems that represent both a major K source and sink in the ocean. Here we report K results on mid-ocean ridge (MOR) hydrothermal fluids from the Gorda Ridge and ∼9°N East Pacific Rise (EPR), including time-series samples that recorded major perturbations in fluid chemistry induced by a local volcanic eruption. Fluid K values range from -0.46‰ to -0.15‰, falling between those of fresh basalts and seawater. K values of “time-zero” fluids collected shortly after the volcanic eruption are shifted towards the seawater value, followed by a return to pre-eruption values within ∼2 years. Fluid K variations are largely influenced by water–rock interactions, but they cannot be solely explained by simple mixing of seawater and K leached from basalts at high temperatures. Instead, these data imply small but significant isotope fractionation that enriches heavy K isotopes in basalts, likely caused by low-temperature alteration during the recharge stage of hydrothermal circulation. Our results preclude MOR hydrothermal systems as the cause for the heavy K value of seawater. Using fluid K data and K isotope fractionation constrained here for hydrothermal systems, a K mass-balance model implies a critical role for a marine sedimentary sink, possibly authigenic clay formation, in the global K cycle. Also, applying the K isotope ...
Subject code	550
Language	English
Publisher	Elsevier
Publishing country	de
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Abiologic silicon isotope fractionation between aqueous Si and Fe(III)–Si gel in simulated Archean seawater

Zheng, Xin-Yuan / Beard, Brian L. / Reddy, Thiruchelvi R. / Roden, Eric E. / Johnson, Clark M.

Implications for Si isotope records in Precambrian sedimentary rocks

2016

Abstract: Precambrian Si-rich sedimentary rocks, including cherts and banded iron formations (BIFs), record a >7‰ spread in 30Si/28Si ratios (δ30Si values), yet interpretation of this large variability has been hindered by the paucity of data on Si isotope ... ...

Abstract	Precambrian Si-rich sedimentary rocks, including cherts and banded iron formations (BIFs), record a >7‰ spread in 30Si/28Si ratios (δ30Si values), yet interpretation of this large variability has been hindered by the paucity of data on Si isotope exchange kinetics and equilibrium fractionation factors in systems that are pertinent to Precambrian marine conditions. Using the three-isotope method and an enriched 29Si tracer, a series of experiments were conducted to constrain Si isotope exchange kinetics and fractionation factors between amorphous Fe(III)–Si gel, a likely precursor to Precambrian jaspers and BIFs, and aqueous Si in artificial Archean seawater under anoxic conditions. Experiments were conducted at room temperature, and in the presence and absence of aqueous Fe(II) (Fe(II)aq). Results of this study demonstrate that Si solubility is significantly lower for Fe–Si gel than that of amorphous Si, indicating that seawater Si concentrations in the Precambrian may have been lower than previous estimates. The experiments reached ∼70–90% Si isotope exchange after a period of 53–126 days, and the highest extents of exchange were obtained where Fe(II)aq was present, suggesting that Fe(II)–Fe(III) electron-transfer and atom-exchange reactions catalyze Si isotope exchange through breakage of Fe–Si bonds. All experiments except one showed little change in the instantaneous solid–aqueous Si isotope fractionation factor with time, allowing extraction of equilibrium Si isotope fractionation factors through extrapolation to 100% isotope exchange. The equilibrium 30Si/28Si fractionation between Fe(III)–Si gel and aqueous Si (Δ30Sigel–aqueous) is −2.30 ± 0.25‰ (2σ) in the absence of Fe(II)aq. In the case where Fe(II)aq was present, which resulted in addition of ∼10% Fe(II) in the final solid, creating a mixed Fe(II)–Fe(III) Si gel, the equilibrium fractionation between Fe(II)–Fe(III)–Si gel and aqueous Si (Δ30Sigel–aqueous) is −3.23 ± 0.37‰ (2σ). Equilibrium Si isotope fractionation for Fe–Si gel systems is ...
Subject code	541
Language	English
Publisher	Elsevier
Publishing country	de
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Silicon isotope fractionation during microbial reduction of Fe(III)–Si gels under Archean seawater conditions and implications for iron formation genesis

Reddy, Thiruchelvi R. / Zheng, Xin-Yuan / Roden, Eric E. / Beard, Brian L. / Johnson, Clark M.

2016

Abstract: Microbial dissimilatory iron reduction (DIR) is a deeply rooted metabolism in the Bacteria and Archaea. In the Archean and Proterozoic, the most likely electron acceptor for DIR in marine environments was Fe(III)–Si gels. It has been recently suggested ... ...

Abstract	Microbial dissimilatory iron reduction (DIR) is a deeply rooted metabolism in the Bacteria and Archaea. In the Archean and Proterozoic, the most likely electron acceptor for DIR in marine environments was Fe(III)–Si gels. It has been recently suggested that the Fe and Si cycles were coupled through sorption of aqueous Si to iron oxides/hydroxides, and through release of Si during DIR. Evidence for the close association of the Fe and Si cycles comes from banded iron formations (BIFs), which consist of alternating bands of Fe-bearing minerals and quartz (chert). Although there has been extensive study of the stable Fe isotope fractionations produced by DIR of Fe(III)–Si gels, as well as studies of stable Fe isotope fractionations in analogous abiologic systems, no studies to date have investigated stable Si isotope fractionations produced by DIR. In this study, the stable Si isotope fractionations produced by microbial reduction of Fe(III)–Si gels were investigated in simulated artificial Archean seawater (AAS), using the marine iron-reducing bacterium Desulfuromonas acetoxidans. Microbial reduction produced very large 30Si/28Si isotope fractionations between the solid and aqueous phase at ∼23 °C, where Δ30Sisolid–aqueous isotope fractionations of −3.35 ± 0.16‰ and −3.46 ± 0.09‰ were produced in two replicate experiments at 32% Fe(III) reduction (solid-phase Fe(II)/FeTotal = 0.32). This isotopic fractionation was substantially greater than that observed in two abiologic controls that had solid-phase Fe(II)/FeTotal = 0.02–0.03, which produced Δ30Sisolid–aqueous isotope fractionations of −2.83 ± 0.24‰ and −2.65 ± 0.28‰. In a companion study, the equilibrium Δ30Sisolid–aqueous isotope fractionation was determined to be −2.3‰ for solid-phase Fe(II)/FeTotal = 0. Collectively, these results highlight the importance of Fe(II) in Fe–Si gels in producing large changes in Si isotope fractionations. These results suggest that DIR should produce highly negative δ30Si values in quartz that is the product of diagenetic ...
Subject code	540
Language	English
Publisher	Elsevier
Publishing country	de
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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