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Xu, Yingkui, Dan Zhu, Xiongyao Li, and Jianzhong Liu. "Why magnesium isotope fractionation is absent from basaltic melts under thermal gradients in natural settings." Geological Magazine 157, no. 7 (November 25, 2019): 1144–48. http://dx.doi.org/10.1017/s0016756819001304.
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AbstractLaboratory experiments have shown that thermal gradients in silicate melts can lead to isotopic fractionation; this is known as the Richter effect. However, it is perplexing that the Richter effect has not been documented in natural samples as thermal gradients commonly exist within natural igneous systems. To resolve this discrepancy, theoretical analysis and calculations were undertaken. We found that the Richter effect, commonly seen in experiments with wholly molten silicates, cannot be applied to natural systems because natural igneous samples are more likely to be formed out of partially molten magma and the presence of minerals adds complexity to the behaviour of the isotope. In this study, we consider two related diffusion-rate kinetic isotope effects that originate from chemical diffusion, which are absent from experiments with wholly molten samples. We performed detailed calculations for magnesium isotopes, and the results indicated that the Richter effect for magnesium isotopes is buffered by kinetic isotope effects and the total value of magnesium isotope fractionation can be zero or even undetectable. Our study provides a new understanding of isotopic behaviour during the processes of cooling and solidification in natural magmatic systems.
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Doucet, Luc S., Oscar Laurent, Dmitri A. Ionov, Nadine Mattielli, Vinciane Debaille, and Wendy Debouge. "Archean lithospheric differentiation: Insights from Fe and Zn isotopes." Geology 48, no. 10 (June 19, 2020): 1028–32. http://dx.doi.org/10.1130/g47647.1.
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Abstract The Archean continental lithosphere consists of a dominantly felsic continental crust, made of tonalite-trondhjemite-granodiorite (TTG) and subordinate granitoids, and a cratonic lithospheric mantle, made of highly refractory peridotites. Whether they stemmed from the same process of differentiation from the primitive mantle, or were two distinct components that were physically juxtaposed, remains debated. Metal stable isotope ratios are sensitive to magmatic and metamorphic processes and do not evolve with time. Therefore, stable isotope ratios are complementary to radiogenic isotope ratios, and they allow direct comparisons to be made between different terrestrial components without age corrections. Isotopes of iron and zinc, metals ubiquitous in Earth’s lithosphere, can be tracers of lithospheric formation and evolution because they are affected by partial melting (Fe, Zn), redox state (Fe), and the presence of sulfides (Fe, Zn). Here, using stable Fe and Zn isotopic data from Archean samples of the lithospheric mantle and the continental crust, we show that Fe and Zn isotopes define a linear array, best explained by their coupled fractionation behavior during magmatic processes. Our data show that high degrees of partial melting (>30%) during the formation of the cratonic mantle and mafic protocrust, and reworking of the early crust significantly fractionate Fe and Zn isotopes. Conversely, Fe and Zn isotope ratios in the TTG are similar to those in Archean mafic rocks, suggesting an origin by fractional crystallization of basalt, and implying limited Fe and Zn isotopic fractionation, instead of partial melting of mafic crust. Moreover, the absence of Fe and Zn isotope decoupling due to redox effects, melt (fluid)–rock or sediment-rock interaction, and decarbonation indicates that subduction, at least as we understand it now, is not required to explain the Fe and Zn isotope composition of the Archean lithosphere.
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Wang, Yan, Zhongwei Wu, Yi Huang, Xiaoming Sun, Jinhui Yan, Fan Yang, Zhengxin Yin, and Li Xu. "Fe-Cu-Zn Isotopic Compositions in Polymetallic Sulfides from Hydrothermal Fields in the Ultraslow-Spreading Southwest Indian Ridge and Geological Inferences." Minerals 13, no. 7 (June 22, 2023): 843. http://dx.doi.org/10.3390/min13070843.
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Submarine hydrothermal sulfides from the ultraslow-spreading Southwest Indian Ridge (SWIR) were sampled from three hydrothermal fields, and the Fe-Cu-Zn isotopic compositions were analyzed in this study. The Fe isotopes ranged from −0.011‰ to −1.333‰. We believe the processes controlling the Fe isotope variability in the hydrothermal systems include the sulfide precipitation process, the initial isotopic composition of the hydrothermal fluid, and the temperature during precipitation. Among these factors, the sulfide precipitation process is the dominant one. The Cu isotope compositions of the sulfides varied from −0.364‰ to 0.892‰, indicating that the hydrothermal fluid preferentially leached 65Cu in the early stages and that hydrothermal reworking led to decreases in the Cu isotopes in the later stages. In addition, because mass fractionation occurred during sulfide precipitation, the Zn isotope variations ranged from −0.060‰ to 0.422‰. Combined with the S isotopic compositions, these results also implied that different Fe-Cu-Zn isotopic fractionation mechanisms prevailed for the different sample types. Based on these results, we are sure that the metallic elements, including Fe, Cu, and Zn, were derived from the mantle in the SWIR hydrothermal field, and the Fe-Cu isotope results indicated that these metallic elements were provided by fluid leaching processes. Using the isotopic fractionation and sulfide results, we calculated that the Fe-Cu-Zn isotopic compositions of the hydrothermal fluid in this field were δ56Fe(fluid): −0.8~0.0‰; δ65Cu(fluid): 0.3~1.3‰; and δ66Zn(fluid): 0~0.48‰.
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Peters, Stefan T. M., Narges Alibabaie, Andreas Pack, Seann J. McKibbin, Davood Raeisi, Niloofar Nayebi, Farhad Torab, Trevor Ireland, and Bernd Lehmann. "Triple oxygen isotope variations in magnetite from iron-oxide deposits, central Iran, record magmatic fluid interaction with evaporite and carbonate host rocks." Geology 48, no. 3 (December 17, 2019): 211–15. http://dx.doi.org/10.1130/g46981.1.
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Abstract Oxygen isotope ratios in magnetite can be used to study the origin of iron-oxide ore deposits. In previous studies, only 18O/16O ratios of magnetite were determined. Here, we report triple O isotope data (17O/16O and 18O/16O ratios) of magnetite from the iron-oxide–apatite (IOA) deposits of the Yazd and Sirjan areas in central Iran. In contrast to previous interpretations of magnetite from similar deposits, the triple O isotope data show that only a few of the magnetite samples potentially record isotopic equilibrium with magma or with pristine magmatic water (H2O). Instead, the data can be explained if magnetite had exchanged O isotopes with fluids that had a mass-independently fractionated O isotope composition (i.e., MIF-O), and with fluids that had exchanged O isotopes with marine sedimentary carbonate rocks. The MIF-O signature of the fluids was likely obtained by isotope exchange with evaporite rocks of early Cambrian age that are associated with the IOA deposits in central Iran. In order to explain the triple O isotope composition of the magnetite samples in conjunction with available iron isotope data for magnetite from the deposits, we propose that magnetite formed from magmatic fluids that had interacted with evaporite and carbonate rocks at high temperatures and at variable water/rock ratios; e.g., magmatic fluids that had been released into the country rocks of a magma reservoir. Additionally, the magnetite could have formed from magmatic fluids that had exchanged O isotopes with SO2 and CO2 that, in turn, had been derived by the magmatic assimilation and/or metamorphic breakdown of evaporite and carbonate rocks.
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Dickin, Alan P., and Richard Muller. "Radiogenic Isotope Geology." Physics Today 49, no. 6 (June 1996): 60. http://dx.doi.org/10.1063/1.2807660.
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Corfield, Richard M., and Richard D. Norris. "Isotope Paleobiology and Paleoecology: So Why Should Paleontologists Care About Geochemistry?" Paleontological Society Papers 4 (October 1998): 1–6. http://dx.doi.org/10.1017/s1089332600000371.
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Stable isotopic techniques in geology illuminate not only variations in past climates and oceans, but also the life-histories of extinct animals, plants and protistans. This volume focuses on the ways that stable isotopes can be used as tracers of the fossil biology and ecology of long-dead organisms and ecosystems. Here, we introduce relevant aspects of stable isotope systematics and provide a summary of the papers collected in this volume. The nine contributions collected here, from some of the most eminent workers in their respective fields, explore aspects of the ecology, evolution and biology of organisms from planktonic foraminifera to dinosaurs.
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Carlson, Richard W. "Principles of isotope geology." Geochimica et Cosmochimica Acta 51, no. 6 (June 1987): 1779. http://dx.doi.org/10.1016/0016-7037(87)90361-9.
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Ji, Mingyu, Debin Jia, Zhang Hao, Jinyan Guo, Xiaoyan Li, Xiujuan Li, and Wenqiang Liu. "Isotope Applications Exploration and Research Progress." Journal of Engineering System 1, no. 4 (December 2023): 39–44. http://dx.doi.org/10.62517/jes.202302408.
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Isotopes, as key concepts in chemistry and physics, are extremely important for understanding elemental properties and behavior. This review aims to provide a comprehensive view of the basic theory of isotopes, including their definition and classification: stable isotopes versus radioactive isotopes. Isotopes not only have a place in theoretical studies, but also play a key role in several practical applications, such as radioisotopes for diagnosis and treatment in medicine, isotopes for determining the age of rocks and fossils in geology, tracking sources of pollution and ecosystem changes in environmental sciences. In addition, this paper will explore recent advances in isotope research, including the discovery of new isotopes, the enhancement of isotope analysis techniques, and new applications of isotopes at the intersection of several disciplines, including biology, environmental science, and forensic science. Through these comprehensive discussions, this review aims to provide researchers and students in related fields with an updated and comprehensive research perspective and reference.
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He, Zhiwei, Bo Li, Xinfu Wang, Xianguo Xiao, Xin Wan, and Qingxi Wei. "The Origin of Carbonate Components in Carbonate Hosted Pb-Zn Deposit in the Sichuan-Yunnan-Guizhou Pb-Zn Metallogenic Province and Southwest China: Take Lekai Pb-Zn Deposit as an Example." Minerals 12, no. 12 (December 15, 2022): 1615. http://dx.doi.org/10.3390/min12121615.
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The Lekai lead–zinc (Pb-Zn) deposit is located in the northwest of the Sichuan–Yunnan–Guizhou (SYG) Pb-Zn metallogenic province, southwest China. Even now, the source of the metallogenic fluid of Pb-Zn deposits in the SYG Pb-Zn metallogenic province has not been recognized. Based on traditional lithography, rare earth elements (REEs), and carbon–oxygen (C–O) isotopes, this work uses the magnesium (Mg) isotopes of hydrothermal carbonate to discuss the fluid source of the Lekai Pb-Zn deposit and discusses the fractionation mechaism of Mg isotopes during Pb-Zn mineralization. The REE distribution patterns of hydrothermal calcite/dolomite are similar to that of Devonian sedimentary carbonate rocks, which are all present steep right-dip type, indicating that sedimentary carbonate rocks may be serve as the main source units of ore-forming fluids. The C–O isotopic results of hydrothermal dolomite/calcite and the δ13CPDB–δ18 OSMOW diagram show that dolomite formation is closely related to the dissolution of marine carbonate rocks, and calcite may be affected to some extent by basement fluid. The Mg isotopic composition of dolomite/calcite ranges from −3.853‰ to −1.358‰, which is obviously lighter than that of chondrites, mantle, or seawater and close to that of sedimentary carbonate rock. It shows that the source of the Mg element in metallogenic fluid of Lekai Pb-Zn deposit may be sedimentary carbonate rock rather than mantle, chondrites, or seawater. In addition, the mineral phase controls the Mg isotope fractionation of dolomite/calcite in the Lekai Pb-Zn deposit. Based on the geological, mineralogical, and hydrothermal calcite/dolomite REE, C–O isotope, and Mg isotope values, this work holds that the mineralization of the Lekai Pb-Zn deposit is mainly caused by basin fluids, influenced by the basement fluids; the participation of basement fluids affects the scale and grade of the deposit.
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Deng, Chenglai, Changqing Hu, Ming Li, and Wu Li. "Iron Isotope Composition of Adakitic Rocks: The Shangcheng Pluton, Western Dabie Orogen, Central China." Minerals 11, no. 12 (November 30, 2021): 1356. http://dx.doi.org/10.3390/min11121356.
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There has been little research on the metal isotopic composition of adakitic rock. The main objective of our investigation was to obtain more knowledge on the iron isotopic composition of adakitic rocks and provide new evidence for the genesis of Shangcheng pluton from an iron isotope perspective. The Dabie orogen is divided into eastern and western areas by the Shangcheng-Macheng fault, and the Shangcheng pluton is located in the western Dabie orogen area. The iron isotopic composition of these rocks ranges from 0.08‰ to 0.20‰ (2SD, n = 3). The δ56Fe values of two rocks from the SGD (Sigudun) unit are relatively low (0.11 ± 0.03‰ and 0.08 ± 0.04‰), while the δ56Fe values of the other samples are basically consistent (0.18–0.2‰). Evidence from elemental geochemical characteristics and petrogenesis defines the Shangcheng pluton as adakitic rocks. Our investigation on the elemental and isotopic compositions hints that the enrichment of heavy iron isotopes cannot be explained by weathering/alteration and fluid exsolution. Fractional crystallization of magnetite may account for the enrichment of light iron isotopes in two rocks from the SGD unit, while the fractional iron isotope trend in the other five samples can be explained by Δ56Fecrystal-melt = ~0.035‰. Two investigated rocks from SGD units may have been derived from the partial melting of amphibolite, while the other five samples may have been derived from the partial melting of eclogite containing 10–15% garnet.
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Alatarvas, Raisa, Ninna Immonen, and Kari Strand. "Clay mineral and Nd, Pb, and Sr isotope provenance of a MIS 4-3 sediment record from the Lomonosov Ridge, central Arctic Ocean." Bulletin of the Geological Society of Finland 95, no. 1 (June 22, 2023): 35–46. http://dx.doi.org/10.17741/bgsf/95.1.003.
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Modern techniques for detrital mineral provenance were applied to sediment core 96/12-1pc from the Lomonosov Ridge in the central Arctic Ocean. The techniques include quantitative clay mineralogy analysis combined with determination of Nd, Pb, and Sr isotopes from clay fraction. The clay mineral assemblage and the isotope signatures depict distinct changes during the Marine Isotope Stage (MIS) 4-3 transition corresponding to the Middle Weichselian deglaciation. This transition is characterised by a homogenous, 48 cm thick, dark grey, silty clay layer with a distinctive IRD concentration, forming a prominent marker bed for the central Arctic Ocean sediments. The elevated smectite and kaolinite contents in the transitional interval are possible weathering products of the Siberian basaltic rocks, such as the Putorana Plateau, feeding the shelves of the Kara Sea and the western Laptev Sea. The Nd and Sr isotope values are compatible with input from the basaltic rocks and fall within the isotopic range of sediments from these shelves. The abrupt changes in the Nd, Pb and Sr isotopic data from the distinct grey layer attributed to the MIS 4-3 transition likely mark a pronounced deglaciation event. An increase in coarse debris in the grey layer indicates a change in the sedimentation regime with a strong iceberg rafting component. This change may also be related to a sudden release of meltwater from a large ice-dammed lake in the northern Siberia.
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Xue, Song, Yaoling Niu, Yanhong Chen, Yining Shi, Boyang Xia, Peiyao Wang, Hongmei Gong, Xiaohong Wang, and Meng Duan. "Iron Isotope Fractionation during Skarn Cu-Fe Mineralization." Minerals 11, no. 5 (April 22, 2021): 444. http://dx.doi.org/10.3390/min11050444.
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Fe isotopes have been applied to the petrogenesis of ore deposits. However, the behavior of iron isotopes in the mineralization of porphyry-skarn deposits is still poorly understood. In this study, we report the Fe isotopes of ore mineral separations (magnetite, pyrite, chalcopyrite and pyrrhotite) from two different skarn deposits, i.e., the Tonglvshan Cu-Fe skarn deposit developed in an oxidized hydrothermal system and the Anqing Cu skarn deposit developed in a reduced hydrothermal system. In both deposits, the Fe isotopes of calculated equilibrium fluids are lighter than those of the intrusions responsible for the skarn and porphyry mineralization, corroborating the “light-Fe fluid” hypothesis. Interestingly, chalcopyrite in the oxidized-Tonglvshan skarn deposit has lighter Fe than chalcopyrite in the reduced-Anqing skarn deposit, which is best understood as the result of the prior precipitation of magnetite (heavy Fe) from the ore fluid in the oxidized-Tonglvshan systems and the prior precipitation of pyrrhotite (light Fe) from the ore fluid in the reduced-Anqing system. The δ56Fe for pyrite shows an inverse correlation with δ56Fe of magnetite in the Tonglvshan. In both deposits, the Fe isotope fractionation between chalcopyrite and pyrite is offset from the equilibrium line at 350 °C and lies between the FeS-chalcopyrite equilibrium line and pyrite-chalcopyrite equilibrium line at 350 °C. These observations are consistent with the FeS pathway towards pyrite formation. That is, Fe isotopes fractionation during pyrite formation depends on a path from the initial FeS-fluid equilibrium towards the pyrite-fluid equilibrium due to the increasing extent of Fe isotopic exchange with fluids. This finding, together with the data from other deposits, allows us to propose that the pathway effect of pyrite formation in the Porphyry-skarn deposit mineralization is the dominant mechanism that controls Fe isotope characteristics.
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Cantrell, Dave L., Abdullah Al-Khammash, and Peter D. Jenden. "Characterization and significance of dedolomite in Wadi Nisah, central Saudi Arabia." GeoArabia 12, no. 3 (July 1, 2007): 15–30. http://dx.doi.org/10.2113/geoarabia120315.
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ABSTRACT Two different types of calcified dolomite, or dedolomite, occur as stratiform and non-stratiform bodies within the Jurassic (Kimmeridgian) upper Jubaila Formation in the Wadi Nisah area of central Saudi Arabia. In the stratigraphically-equivalent subsurface Arab-D reservoir in eastern Saudi Arabia, two types of dolomite, stratiform and non-stratiform, occur which appear to be similar in architecture to the dedolomites examined in this study. However, Wadi Nisah dedolomites exhibit systematic changes in texture and isotopic composition from their precursor dolomites. Non-stratiform dedolomite contains lower oxygen isotope (average δ18O = -10.99‰) and much lower carbon isotope (average δ13C = -7.51‰) values and is much more coarsely crystalline than typical subsurface Arab-D non-stratiform dolomite; in contrast, Wadi Nisah stratiform dedolomite contains similar oxygen isotope values (δ18O = -2.89‰) and only slightly lower carbon isotopes (δ13C = 0.98‰) relative to subsurface Arab-D stratiform dolomites. We suggest that non-stratiform dolomite was more susceptible to late meteoric diagenesis than the horizontally bedded stratiform dolomite intervals. Such differences in character highlight the importance of structural and diagenetic architecture in determining later, post-dolomitization diagenesis and ultimately final reservoir quality.
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Hasegawa, Takuma, Kotaro Nakata, and Rhys Gwynne. "Measurement on Diffusion Coefficients and Isotope Fractionation Factors by a Through-Diffusion Experiment." Minerals 11, no. 2 (February 16, 2021): 208. http://dx.doi.org/10.3390/min11020208.
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For radioactive waste disposal, it is important that local groundwater flow is slow as groundwater flow is the main transport medium for radioactive nuclides in geological formations. When the groundwater flow is very slow, diffusion is the dominant transport mechanism (diffusion-dominant domain). Key pieces of evidence indicating a diffusion-dominant domain are the separation of components and the fractionation of isotopes by diffusion. To prove this, it is necessary to investigate the different diffusion coefficients for each component and the related stable isotope fractionation factors. Thus, in this study, through-diffusion and effective-porosity experiments were conducted on selected artificial materials and natural rocks. We also undertook measurements relating to the isotope fractionation factors of Cl and Br isotopes for natural samples. For natural rock samples, the diffusion coefficients of water isotopes (HDO and H218O) were three to four times higher than those of monovalent anions (Cl−, Br- and NO3−), and the isotope fractionation factor of 37Cl (1.0017–1.0021) was slightly higher than that of free water. It was experimentally confirmed that the isotope fractionation factor of 81Br was approximately 1.0007–1.0010, which is equivalent to that of free water. The enrichment factor of 81Br was almost half that of 37Cl. The effective porosity ratios of HDO and Cl were slightly different, but the difference was not significant compared to the ratio of their diffusion coefficients. As a result, component separation was dominated by diffusion. For artificial samples, the diffusion coefficients and effective porosities of HDO and Cl were almost the same; it was thus difficult to assess the component separation by diffusion. However, isotope fractionation of Cl and Br was confirmed using a through-diffusion experiment. The results show that HDO and Cl separation and isotope fractionation of Cl and Br can be expected in diffusion-dominant domains in geological formations.
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Kämpf, Lucas, Birgit Plessen, Stefan Lauterbach, Carla Nantke, Hanno Meyer, Bernhard Chapligin, and Achim Brauer. "Stable oxygen and carbon isotopes of carbonates in lake sediments as a paleoflood proxy." Geology 48, no. 1 (October 16, 2019): 3–7. http://dx.doi.org/10.1130/g46593.1.
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Abstract Lake sediments are increasingly explored as reliable paleoflood archives. In addition to established flood proxies including detrital layer thickness, chemical composition, and grain size, we explore stable oxygen and carbon isotope data as paleoflood proxies for lakes in catchments with carbonate bedrock geology. In a case study from Lake Mondsee (Austria), we integrate high-resolution sediment trapping at a proximal and a distal location and stable isotope analyses of varved lake sediments to investigate flood-triggered detrital sediment flux. First, we demonstrate a relation between runoff, detrital sediment flux, and isotope values in the sediment trap record covering the period 2011–2013 CE including 22 events with daily (hourly) peak runoff ranging from 10 (24) m3 s−1 to 79 (110) m3 s−1. The three- to ten-fold lower flood-triggered detrital sediment deposition in the distal trap is well reflected by attenuated peaks in the stable isotope values of trapped sediments. Next, we show that all nine flood-triggered detrital layers deposited in a sediment record from 1988 to 2013 have elevated isotope values compared with endogenic calcite. In addition, even two runoff events that did not cause the deposition of visible detrital layers are distinguished by higher isotope values. Empirical thresholds in the isotope data allow estimation of magnitudes of the majority of floods, although in some cases flood magnitudes are overestimated because local effects can result in too-high isotope values. Hence we present a proof of concept for stable isotopes as reliable tool for reconstructing flood frequency and, although with some limitations, even for flood magnitudes.
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Ebert, Claire E., Asta J. Rand, Kirsten Green-Mink, Julie A. Hoggarth, Carolyn Freiwald, Jaime J. Awe, Willa R. Trask, et al. "Sulfur isotopes as a proxy for human diet and mobility from the preclassic through colonial periods in the Eastern Maya lowlands." PLOS ONE 16, no. 8 (August 12, 2021): e0254992. http://dx.doi.org/10.1371/journal.pone.0254992.
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Maya archaeologists have long been interested in understanding ancient diets because they provide information about broad-scale economic and societal transformations. Though paleodietary studies have primarily relied on stable carbon (δ13C) and nitrogen (δ15N) isotopic analyses of human bone collagen to document the types of food people consumed, stable sulfur (δ34S) isotope analysis can potentially provide valuable data to identify terrestrial, freshwater, or marine/coastal food sources, as well as determine human mobility and migration patterns. Here we assess applications of δ34S for investigating Maya diet and migration through stable isotope analyses of human bone collagen (δ13C, δ15N, and δ34S) from 114 individuals from 12 sites in the Eastern Maya lowlands, temporally spanning from the Late Preclassic (300 BCE—300 CE) through Colonial periods (1520–1800 CE). Results document a diet dominated by maize and other terrestrial resources, consistent with expectations for this inland region. Because δ34S values reflect local geology, our analyses also identified recent migrants to the Eastern lowlands who had non-local δ34S signatures. When combined with other indicators of mobility (e.g., strontium isotopes), sulfur isotopic data provide a powerful tool to investigate movement across a person’s lifespan. This study represents the largest examination of archaeological human δ34S isotope values for the Maya lowlands and provides a foundation for novel insights into both subsistence practices and migration.
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Han, Wenxue, Xiangchun Chang, Weijiao Ma, Shizhen Tao, Jingli Yao, Lianhua Hou, and Weiwei Yang. "Geochemical characteristics and reasons for the carbon isotopic reversal of natural gas in the southern Jingbian gas field, Ordos Basin, China." Geological Magazine 157, no. 4 (August 1, 2019): 527–38. http://dx.doi.org/10.1017/s0016756819000682.
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AbstractThe carbon isotope value of ethane in the southern part of the Jingbian gas field is lower than that in the northern part, indicating a carbon isotopic reversal in the southern Jingbian gas field (δ13Cmethane > δ13Cethane). Through comparing the geochemical characteristics of gases in the southern and northern parts of the gas field, the reasons for the carbon isotopic reversal in the southern Jingbian gas field were determined to be high thermal maturity and mixing action. When thermal maturity reaches a critical value, the carbon isotope value of ethane becomes relatively more depleted with thermal maturity. Although the carbon isotope value of methane increases with thermal maturity, the extent is relatively smaller. Finally, the rare phenomenon of δ13Cmethane > δ13Cethane occurs. High thermal maturity leads to the secondary thermal cracking of gases. Mixing of the cracked gases and primary gases also leads to carbon isotopic reversal. Both of the above mechanisms share a common premise, which is high thermal maturity.
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Rossi, Mattia, Paola Iacumin, and Gianpiero Venturelli. "87Sr/86Sr Isotope Ratio as a Tool in Archaeological Investigation: Limits and Risks." Quaternary 7, no. 1 (January 11, 2024): 6. http://dx.doi.org/10.3390/quat7010006.
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During the last forty years, the use of strontium isotopes in archaeology and biogeochemical research has spread widely. These isotopes, alone or in combination with others, can contribute to trace past and present environmental conditions. However, the interpretation of the isotopic values of strontium is not always simple and requires good knowledge of geochemistry and geology. This short paper on the use of strontium isotopes is aimed at those who use this tool (archaeologists, but not only) but who do not have a thorough knowledge of mineralogy, geology, and geochemistry necessary for a good understanding of natural processes involving these isotopes. We report basic knowledge and suggestions for the correct use of these isotopes. The isotopic characteristics of bio-assimilable strontium depend not so much on the isotopic characteristics of the bulk rock as, rather, on those of its more soluble minerals. Before studying human, animal and plant remains, the state of conservation and any conditions of isotopic pollution should be carefully checked. Samples should be collected according to random sampling rules. The data should be treated by a statistical approach. To make comparisons between different areas, it should be borne in mind that the study of current soils can be misleading since the mineralogical modification of soil over time can be very rapid.
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Jenkyns, Hugh C., and Sophie Macfarlane. "The chemostratigraphy and environmental significance of the Marlstone and Junction Bed (Beacon Limestone, Toarcian, Lower Jurassic, Dorset, UK)." Geological Magazine 159, no. 3 (November 2, 2021): 357–71. http://dx.doi.org/10.1017/s0016756821000972.
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AbstractTwo fallen blocks of the Marlstone and stratigraphically overlying Junction Bed sampled on the beach below Doghouse Cliff in Dorset, UK (Wessex Basin) have been examined for carbon and oxygen isotopes of bulk carbonate as well as for strontium, carbon and oxygen isotopes and Mg:Ca ratios in the contained belemnites. The sequence, which contains most of the Toarcian zones and subzones within a metre or less of grey to yellow to pink, red and brown fossil-rich nodular limestone, is extremely condensed and lithologically similar to pelagic red limestones of the Tethyan Jurassic that are locally mineralized with Fe-Mn oxyhydroxides (e.g., Rosso Ammonitico). Strontium-isotope ratios of the contained belemnites are compatible with existing reference curves and both blocks show a rise to more radiogenic values post-dating the Pliensbachian–Toarcian boundary. The high degree of correlation between the relatively negative carbon and oxygen isotopes of the bulk carbonate is compatible with significant diagenetic overprint, and contrasts with higher carbon-isotope values in coeval condensed coccolith-rich limestones elsewhere. Evidence for the characteristic signature of the Toarcian Oceanic Anoxic Event, as represented by organic-rich sediment, is absent, possibly owing to a stratigraphic gap. Both blocks exhibit abrupt carbon-isotope shifts to lower values, one of which could represent the limbs of an incompletely recorded negative excursion associated with the Toarcian Oceanic Anoxic Event. That the Toarcian Oceanic Anoxic Event was also a significant hyperthermal is illustrated in both blocks by a drop in oxygen-isotope values and rise in Mg:Ca ratios of belemnites close to the base of the Junction Bed in the lowest part of the serpentinum zone.
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Thiagarajan, Nivedita, Jon Halvard Pedersen, Harald Brunstad, Joachim Rinna, Aivo Lepland, and John Eiler. "Clumped isotope constraints on the origins of reservoir methane from the Barents Sea." Petroleum Geoscience 28, no. 2 (March 14, 2022): petgeo2021–037. http://dx.doi.org/10.1144/petgeo2021-037.
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The Barents Sea basin is an oil and gas province containing more than 760 million tons of oil equivalents. The reservoir geology of the Barents Sea is complex due to multiple episodes of subsidence, uplift and erosion, which opened a network of extensional and wrench related faults allowing for fluid migration. The multifaceted geological history complicates efforts to describe the source and characteristics of natural gas in the subsurface Barents Sea. Here we apply stable isotopes, including methane clumped isotope measurements, to thirteen natural gases from five (Skrugard Appraisal, Havis, Alta, Filicudi, and Svanefjell) reservoirs in the Loppa High area in the southwestern Barents Sea to estimate the origins of methane. We compare estimates of methane formation temperature based on clumped isotopes to thermal evolution models for the region. We find that the methane has diverse origins including microbial and thermogenic sources forming and equilibrating at temperatures ranging from 34–238°C. Our clumped isotope temperature estimates are consistent with thermal evolution models for the area. These temperatures can be explained by gas generation and expulsion in the oil and gas window followed by isotopic re-equilibration in some reservoirs due to microbial methanogenesis and/or anaerobic oxidation of methane. Gases from the Skrugard Appraisal, Havis and Alta have methane equilibration temperatures consistent with maximum burial temperatures, while gases from Svanefjell have methane equilibration temperatures consistent with current reservoir temperature, suggesting isotope re-equilibration in the shallow reservoir. Gases from Filicudi on the other hand are consistent with generation over multiple points over its thermal history.
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Gudelius, Dominik, Sonja Aulbach, Hans-Michael Seitz, and Roberto Braga. "Crustal fluids cause strong Lu-Hf fractionation and Hf-Nd-Li isotopic provinciality in the mantle of continental subduction zones." Geology 50, no. 2 (November 2, 2021): 163–68. http://dx.doi.org/10.1130/g49317.1.
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Abstract Metasomatized mantle wedge peridotites exhumed within high-pressure terranes of continental collision zones provide unique insights into crust-mantle interaction and attendant mass transfer, which are critical to our understanding of terrestrial element cycles. Such peridotites occur in high-grade gneisses of the Ulten Zone in the European Alps and record metasomatism by crustal fluids at 330 Ma and high-pressure conditions (2.0 GPa, 850 °C) that caused a transition from coarse-grained, garnet-bearing to fine-grained, amphibole-rich rocks. We explored the effects of crustal fluids on canonically robust Lu-Hf peridotite isotope signatures in comparison with fluid-sensitive trace elements and Nd-Li isotopes. Notably, we found that a Lu-Hf pseudo-isochron is created by a decrease in bulk-rock 176Lu/177Hf from coarse- to fine-grained peridotite that is demonstrably caused by heavy rare earth element (HREE) loss during fluid-assisted, garnet-consuming, amphibole-forming reactions accompanied by enrichment in fluid-mobile elements and the addition of unradiogenic Nd. Despite close spatial relationships, some peridotite lenses record more intense fluid activity that causes complete garnet breakdown and high field strength element (HFSE) addition along with the addition of crust-derived unradiogenic Hf, as well as distinct chromatographic light REE (LREE) fractionation. We suggest that the observed geochemical and isotopic provinciality between peridotite lenses reflects different positions relative to the crustal fluid source at depth. This interpretation is supported by Li isotopes: inferred proximal peridotites show light δ7Li due to strong kinetic Li isotope fractionation (−4.7–2.0‰) that accompanies Li enrichment, whereas distal peridotites show Li contents and δ7Li similar to those of the depleted mantle (1.0–7.2‰). Thus, Earth's mantle can acquire significant Hf-Nd-Li-isotopic heterogeneity during locally variable ingress of crustal fluids in continental subduction zones.
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Fitzpatrick, Ryan M., Dana L. Winkelman, and Brett M. Johnson. "Using Isotopic Data to Evaluate Esox lucius (Linnaeus, 1758) Natal Origins in a Hydrologically Complex River Basin." Fishes 6, no. 4 (November 22, 2021): 67. http://dx.doi.org/10.3390/fishes6040067.
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Otolith microchemistry has emerged as a powerful technique with which to identify the natal origins of fishes, but it relies on differences in underlying geology that may occur over large spatial scales. An examination of how small a spatial scale on which this technique can be implemented, especially in water bodies that share a large proportion of their flow, would be useful for guiding aquatic invasive species control efforts. We examined trace isotopic signatures in northern pike (Esox lucius) otoliths to estimate their provenance between two reservoirs in the Upper Yampa River Basin, Colorado, USA. This is a challenging study area as these reservoirs are only 11-rkm apart on the same river and thus share a high proportion of their inflow. We found that three isotopes (86Sr, 137Ba, and 55Mn) were useful in discriminating between these reservoirs, but their signatures varied annually, and the values overlapped. Strontium isotope ratios (87Sr/86Sr) were different between sites and relatively stable across three years, which made them an ideal marker for determining northern pike provenance. Our study demonstrates the usefulness of otolith microchemistry for natal origin determination within the same river over a relatively small spatial scale when there are geologic differences between sites, especially geologic differences underlying tributaries between sites.
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PE-PIPER, GEORGIA, and DAVID J. W. PIPER. "Late Cenozoic, post-collisional Aegean igneous rocks: Nd, Pb and Sr isotopic constraints on petrogenetic and tectonic models." Geological Magazine 138, no. 6 (November 2001): 653–68. http://dx.doi.org/10.1017/s0016756801005957.
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Nd isotopic composition has been determined for 16 igneous rocks, representing the wide geochemical, spatial and temporal range of post-collisional, late Cenozoic magmas in the Aegean area. Nd isotopes are used to further interpret previously published Pb and Sr isotope data. The overall pattern of late Cenozoic volcanism resulted from rapid extension, with thermal effects causing melting of hydrated, enriched, subcontinental lithosphere to produce widespread K-rich magmas. Slab break-off and intrusion of hot asthenosphere caused partial melting of rift-related continental margin basalts at the detachment point to generate adakitic magmas. Further outboard, mafic magma from enriched lithospheric mantle melted thickened lower crust to produce the granitoid plutons of the Cyclades. Nd isotopic variation in these varied rock types correlates with pre-Cenozoic palaeo-geography. Proterozoic subduction-related enrichment in Th and U, together with other large-ion lithophile elements, produced distinctive Pb isotope composition. This was later modified where Mesozoic subduction of terrigenous sediment was important, whereas subduction of oceanic carbonate sediments produced enrichment in radiogenic Sr and low Ce/Sr ratios. Late Cenozoic magmas sourced in eastern Pelagonian zone sub-continental lithospheric mantle have Nd model ages of about 1.0 Ga, and generally high 87Sr/86Sr and high 207Pb/204Pb (∼ 15.68) and 208Pb/204Pb (∼ 39.0) for low 206Pb/204Pb (∼ 18.6), but rocks to the west have more radiogenic Pb and higher Ce/Sr as a result of greater subduction of terrigenous sediment from the northern Pindos ocean. Magmas sourced from sub-continental lithosphere beneath the Apulian continental block were strongly influenced by subduction of oceanic crust and sediments north of the passive margin of north Africa. Subduction of Nile-derived terrigenous sediment in the east resulted in Nd model ages of 0.7 to 0.8 Ga and radiogenic Pb isotopes. Greater subduction of oceanic carbonate in the west resulted in magmas with higher 87Sr/86Sr and lower Ce/Sr. The strongly negative εNd for adakites in the central Aegean rules out a source from subducted oceanic basalt, and the adakite magma was probably derived from melting of hydrated Triassic sub-alkaline basalt of continental origin. Where trachytic rocks are succeeded by nepheline-normative basalts (e.g. Samos), Nd isotope data imply that early partial melting of the enriched subcontinental lithospheric mantle involved hydrous amphibole and phlogopite, but once these minerals were consumed, younger magmas were produced by partial melting dominated by olivine and orthopyroxene.
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Yakovlev, Evgeny Yu. "Features of radioactive element distribution within the Arkhangelsk diamondiferous province: possible directions for development of isotope–radiogeochemical methods for kimberlite prospecting in complex landscape–geology and climate conditions of the subarctic zone." Geochemistry: Exploration, Environment, Analysis 20, no. 3 (July 3, 2019): 269–79. http://dx.doi.org/10.1144/geochem2019-023.
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The effectiveness of traditional methods of searching for kimberlite pipes in the Arkhangelsk diamondiferous province (in the subarctic zone of Russia) has decreased greatly in recent years, and new methods of kimberlite exploration must therefore be developed. This study discusses new patterns of the distribution of natural radioactive isotopes within the Arkhangelsk diamondiferous province (Zolotitskoe kimberlite field), and the uranium isotopes 234U and 238U in particular. A variety of isotope radiogeochemical studies has shown that the kimberlite pipes are characterized by local radioisotope anomalies, on the surface and in exploration drill cores. These irregularities are clearly manifested in the formation of a non-equilibrium anomalous uranium isotope composition in the surrounding rocks and groundwater of the near-contact zone of the pipes. These uranium isotopes can be used to explore for kimberlites in other areas with similar complex landscape–geology and climate conditions of the subarctic zone.
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Sun, Yuqin, Xin Wang, Yan Zhang, Dapeng Li, Wei Shan, Ke Geng, Pengfei Wei, Qiang Liu, Wei Xie, and Naijie Chi. "Cu–S Isotopes of the Main Sulfides and Indicative Significance in the Qibaoshan Cu–Au Polymetallic Ore District, Wulian County, Shandong Province, North China Craton." Minerals 13, no. 6 (May 25, 2023): 723. http://dx.doi.org/10.3390/min13060723.
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With a focus on the Cu isotope geochemistry of chalcopyrite, this paper analyzed the Cu isotope geochemistry of the Qibaoshan crypto-explosive breccia-type Cu–Au polymetallic ore district in Wulian, Shandong Province, North China Craton (NCC). Combined with the results of the in situ sulfur isotope analysis of sulfides, a certain reference and evidence for the study of the genetic mechanism of the epithermal-porphyry Cu polymetallic metallogenic system were provided. The results of the in situ isotope analysis show that the δ34S values of the main sulfides in the Qibaoshan Cu–Au polymetallic ore district range from −6.81‰ to +3.82‰ and are likely to be attributed to the mixing of the derived mantle with the surrounding sedimentary rock assimilation. The ore-forming mechanism may be related to the progressive cooling and transition of the earliest hydrothermal fluids that were dominated by H2S under relatively reducing conditions, followed by a gradual transition from oxidation to reduction. The Cu isotopic composition of the sulfides in ores (δ65Cu = +0.169‰–+0.357‰) decreases with depth, which is likely caused by the upward transport of heavier Cu isotopes. The upper part of the crypto-explosive breccia pipe in the Qibaoshan area may be relatively more gaseous, resulting in the enrichment of δ65Cu. As the gas phase decreases and the liquid phase increases with depth, the δ65Cu value gradually decreases. This indicates the transition from a low-temperature phyllic alteration to a high-temperature K-feldspar alteration. Large, concealed pluton intrusions or orebodies may be present at a depth of the Qibaoshan area. The heavy δ65Cu characteristic is a potential indicator for tracing the fluid activity of the porphyry system and searching for Cu mines. The results provide a reference for the study of the genetic mechanisms of the epithermal-porphyry Cu polymetallic metallogenic system.
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Holdsworth, Chris, John MacDonald, and Cedric John. "Non-Linear Clumped Isotopes from DIC Endmember Mixing and Kinetic Isotope Fractionation in High pH Anthropogenic Tufa." Minerals 12, no. 12 (December 14, 2022): 1611. http://dx.doi.org/10.3390/min12121611.
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Clumped isotope values (Δ47) of carbonates forming in high pH conditions do not correspond to mineral precipitation temperatures due to certain effects including kinetic isotope fractionation and dissolved inorganic carbon (DIC) endmember mixing. Field-based archives of these carbonate environments are needed to evaluate and quantity these effects accurately. In this study, we measure the clumped isotope values of anthropogenic carbonates for the first time. Tufa layers were analyzed from samples precipitating in a high pH (>10) stream that drains a major slag heap in north east England. Δ47 values are 0.044‰–0.183‰ higher than expected equilibrium values. Non-linear distribution of clumped isotope data is diagnostic of DIC endmember mixing, rather than partial equilibration of DIC. Episodic dilution of hydroxide-rich stream waters by equilibrated rainfall surface runoff provides the mechanism by which mixing occurs. Δ47 values are ~0.010‰–0.145‰ higher than linear clumped isotope mixing profiles, suggesting that the majority of Δ47 increase results from a combination of endmember non-linear mixing effects and an atmosphere-hydroxide sourcing of DIC. The diagnostic trends and variation in clumped isotope values present in these results demonstrates the potential of anthropogenic carbonate systems as a useful archive for studying and quantifying kinetic effects in clumped isotopes.
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Dyer-Pietras, Kuwanna. "Lake basin closure and episodic inflow as recorded by radiogenic Sr isotopes: Eocene Green River Formation in the Piceance Creek Basin, Colorado." Mountain Geologist 57, no. 4 (October 28, 2020): 355–73. http://dx.doi.org/10.31582/rmag.mg.57.4.355.
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Lacustrine basins are excellent archives of lake evolution, and deposits record the uplift and weathering histories of the surrounding terrain. The application of Sr isotopes has been tested in several lacustrine basins, both modern and ancient, based on the premise that lakes are well mixed, and shifting Sr isotopes may suggest changes in lake provenance. In the Eocene lacustrine Green River Formation in the Piceance Creek Basin of Colorado, Sr isotope analysis of carbonate mudstones indicates that radiogenic Sr in the center of the Piceance lake decreased during the evolution of the lake, from 52.8–48.4 Ma. Because deposition in the basin center occurred away from the influence of episodic alluvial inflow at the basin margin, Sr isotope evolution in the Piceance lake after basin closure is recorded in the John Savage #24-1 core deposits, not the Anvil Points deposits. Sr isotope analysis of carbonate mudstones at Anvil Points below 55 m shows fluctuating radiogenic Sr values that record episodic inflow from the White River Uplift. This inflow is responsible for the difference in radiogenic Sr trends recorded between the basin center and margin. Above 55 m, fluctuating Sr isotope values at Anvil Points record episodic inflow from the White River Uplift, without inflow of Paleozoic and Mesozoic carbonates. The boundary at 55 m records the hydrologic closure of the Uinta and Piceance lakes around 52 Ma, when lake level lowered beneath the basin sill and the lakes were no longer connected across the Douglas Creek Arch. A significant increase in radiogenic Sr across the 55-m-boundary records this transition from open to closed hydrology, reflecting a loss of dissolved Sr sourced from Paleozoic and Mesozoic carbonates.
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Novikov, Dmitry A., Aleksandr N. Pyrayev, Anastasia A. Maksimova, Fedor F. Dultsev, and Anatoly V. Chernykh. "Evolution of the composition of Н, О and C stable isotopes in the groundwaters of oil and gas bearing sediments in the northern regions of West Siberia." Georesursy 25, no. 4 (December 30, 2023): 219–32. http://dx.doi.org/10.18599/grs.2023.4.16.
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The results of a study of the isotopic composition of oxygen and hydrogen of groundwater and dissolved inorganic carbon in oil and gas deposits of the northern regions of Western Siberia, covering a wide stratigraphic range – Mesozoic and Paleozoic are presented. The obtained values are very diverse, covering the intervals from –120 to –50‰ (δD) and from –17 to –2‰ (δ18O). Such a variable isotopic composition of waters indicates the absence of a unified mechanism for the accumulation of waters and their transformation during the geological evolution of the West Siberian sedimentary basin. The main feature of most of the studied waters is the pronounced values of oxygen isotope shifts relative to GMWL, which generally increase with the age of water-bearing deposits and reach 9‰, which indicates their ancient sedimentary origin. Variations in the isotopic composition of DIC (from –51.8 to +21.8‰) and its content in waters (from 0.2 to 38.6 mmol/I) indicate a wide range of water burial conditions and processes involved in the conversion of water-soluble carbon dioxide. A general pattern of changes in the isotopic composition of carbon in CO2 with time, expressed in general form by damped oscillations of the “isotope oscillator”, is revealed. A model of transformation of the carbon isotope composition in carbon dioxide in the closed cycle “atmosphere-soils-deep aquifers” for oil and gas deposits of the northern regions of Western Siberia based on the obtained isotope data is proposed.
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Brasier, Martin D., Mordeckai Magaritz, Richard Corfield, Luo Huilin, Wu Xiche, Ouyang Lin, Jiang Zhiwen, B. Hamdi, He Tinggui, and A. G. Fraser. "The carbon- and oxygen-isotope record of the Precambrian–Cambrian boundary interval in China and Iran and their correlation." Geological Magazine 127, no. 4 (July 1990): 319–32. http://dx.doi.org/10.1017/s0016756800014886.
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AbstractThe fossiliferous section at Meishucun of Yunnan, China, is a candidate stratotype section for the Precambrian–Cambrian boundary. Early diagenetic dolomites and phosphorites have been sampled across the boundary interval here, and in the correlated section at Maidiping in Sichuanand Valiabad in Iran, for comparison of their carbon and oxygen isotopes. This is the first such study that is calibrated by biostratigraphy in the interval from the earliest (pre-Tommotian) skeletal fossils to trilobites. Although negative oxygen isotopes indicate a diagenetic signal in the Zhongyicun Member and basal Badaowan Member phosphorites, two carbon-isotope cycles are clearly present and can be correlated in dolomitic rocks between the two sections. The first appearance datum (FAD) of the earliest skeletal assemblage (zone I, Marker A), FAD of diverse micromolluscs (zone II, Marker B) and FAD of Chinese trilobites (zones IV, V) and Marker C appear at similar points on the carbon-isotope curve in the two Chinese sections. Integrated carbon-isotope and early skeletal fossil biostratigraphy is shown to have the potential to correlate further afield, with sections in Iran, as well as with India, Siberia, Morocco and Australia. We suggest that a distinctive positive excursion provides a global marker for the interval between Marker B and C in China and just below the Tommotian Stage of Siberia.
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Jing, Xiuchun, Svend Stouge, Yufeng Tian, Xunlian Wang, and Hongrui Zhou. "Katian (Upper Ordovician) carbon isotope chemostratigraphy in the Neixiang area, central China: implications for intercontinental correlation." Geological Magazine 156, no. 12 (May 17, 2019): 2053–66. http://dx.doi.org/10.1017/s0016756819000372.
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AbstractThe Katian (Upper Ordovician) Shiyanhe Formation at the Sigang section, Neixiang area, Henan Province, central China, has been investigated for carbon isotope (δ13Ccarb) chemostratigraphy. The carbon isotopic data document signal between the two major Ordovician positive shifts in δ13C, the early Katian Guttenberg and the Hirnantian excursions. The Kope (Ka1/2), Fairview (Ka2/3), Waynesville (Ka3/4), Whitewater (Ka4) excursions and a doubtful Elkhorn (Ka4) excursion are identified herein. The continuous and well-defined conodont zonal succession of the Sigang section provides a secure biostratigraphic framework for the mid-late Katian carbon isotope chemostratigraphy in China. Correlation between carbon-isotope data curve and the relative sea-level changes shows no clear correspondence, and hence the sea-level change is probably not the main driver of δ13C excursions during the Katian. Intercontinentally, the mid–late Katian carbon isotope excursions, identified mainly in the North American and Baltoscandian successions, are useful for improving long-distance stratigraphic correlations. This further suggests that these excursions represent global perturbations in the carbon cycle.
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Holcová, Katarína, and Attila Demeny. "The oxygen and carbon isotopic composition of Langhian foraminiferal tests as a paleoecological proxy in a marginal part of the Carpathian Foredeep (Czech Republic)." Geologica Carpathica 63, no. 2 (April 1, 2012): 121–37. http://dx.doi.org/10.2478/v10096-012-0010-x.
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The oxygen and carbon isotopic composition of Langhian foraminiferal tests as a paleoecological proxy in a marginal part of the Carpathian Foredeep (Czech Republic)Foraminiferal assemblages from three locations of the Moravian part of the Carpathian Foredeep (Kralice, Přemyslovice, Židlochovice) have been studied in order to determine the paleoenvironmental conditions during the Early Badenian (Middle Miocene). Paleobiological characteristics (plankton/benthos-ratio, relative abundances of warm-water plankton species, five-chamberedGloboturborotalitaspp.,Coccolithus pelagicusand high nutrient markers [benthos], test sizes and ranges ofGlobigerinasp. and cibicidoids, Benthic Foraminiferal Oxygen Index) were determined along with stable C and O isotope compositions. The stable isotope compositions show large variabilities indicating sample inhomogeneity in well preserved foraminiferal samples, interpreted as a sign of primary environmental variation and postmortem mixing of tests of different populations and sources. Based on the combined interpretation of paleobiological indicators and isotopic compositions, two theoretical models were established to describe the observed paleobiological and stable isotope data, that were used to categorize the locations studied. Several types of near-shore paleoenvironment were distinguished using the theoretical models: (i) bay influenced by seasonal phytodetritus supply from the continent (Kralice); (ii) dynamic shore characterized by variable isotopic compositions probably due to mixing of indigenous, transported and reworked tests (Přemyslovice); (iii) shore of alternating normal marine and continentally influenced environments (Židlochovice).
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Price, T. Douglas, Corina Knipper, Gisela Grupe, and Václav Smrcka. "Strontium Isotopes and Prehistoric Human Migration: The Bell Beaker Period in Central Europe." European Journal of Archaeology 7, no. 1 (2004): 9–40. http://dx.doi.org/10.1177/1461957104047992.
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Human skeletal remains from Bell Beaker graves in southern Germany, Austria, the Czech Republic, and Hungary were analyzed for information on human migration. Strontium isotope ratios were measured in bone and tooth enamel to determine if these individuals had changed ‘geological’ residence during their lifetimes. Strontium isotopes vary among different types of rock. They enter the body through diet and are deposited in the skeleton. Tooth enamel forms during early childhood and does not change. Bone changes continually through life. Difference in the strontium isotope ratio between bone and enamel in the same individual indicates change in residence. Results from the analysis of 81 Bell Beaker individuals indicated that 51 had moved during their lifetime. Information on the geology of south-central Europe, the application of strontium isotope analysis, and the relevant Bell Beaker sites is provided along with discussion of the results of the study.
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Leketa, Khahliso, and Tamiru Abiye. "Using Environmental Tracers to Characterize Groundwater Flow Mechanisms in the Fractured Crystalline and Karst Aquifers in Upper Crocodile River Basin, Johannesburg, South Africa." Hydrology 8, no. 1 (March 19, 2021): 50. http://dx.doi.org/10.3390/hydrology8010050.
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Environmental isotope tracers were applied in the Upper Crocodile River Basin, Johannesburg, South Africa, to understand the groundwater recharge conditions, flow mechanisms and interactions between surface and subsurface water. Stable isotope analysis indicated that recharge into the fractured quartzite aquifer occurs through direct mechanisms. The high variability in the stable isotope signature of temporal samples from Albert Farm spring indicated the importance of multiple samples for groundwater characterization, and that using a single sample may be yielding biased conclusions. The observed inverse relationship between spring discharge and isotope signature indicated the traces of rainfall amount effect during recharge, thereby suggesting piston groundwater flow. It is deduced that a measured discharge value can be used in this relationship to calculate the isotopic signature, which resembles effective rainfall. In the shallow alluvial deposits that overlie the granitic bed-rock, piezometer levels and stable isotopes revealed an interaction between Montgomery stream and interflow, which regulates streamflow throughout the year. This suggests that caution should be taken where hydrograph separation is applied for baseflow estimates, because the stream flow that overlies such geology may include significant interflow. The hydrochemistry evolution was observed in a stream fed by karst springs. As pH rises due to CO2 degassing, CaCO3 precipitates, thereby forming travertine moulds. The values of saturation indices that were greater than zero in all samples indicated supersaturation by calcite and dolomite and hence precipitation. Through 14C analysis, groundwater flow rate in the karst aquifer was estimated as 11 km/year, suggesting deep circulation in karst structures.
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Gao, Peng, Chris Yakymchuk, Jian Zhang, Changqing Yin, Jiahui Qian, and Yanguang Li. "Preferential dissolution of uranium-rich zircon can bias the hafnium isotope compositions of granites." Geology 50, no. 3 (December 1, 2021): 336–40. http://dx.doi.org/10.1130/g49656.1.
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Abstract Hafnium (Hf) isotopes in zircon are important tracers of granite petrogenesis and continental crust evolution. However, zircon in granites generally shows large Hf isotope variations, and the reasons for this are debated. We applied U-Pb geochronology, trace-element, and Hf isotope analyses of zircon from the Miocene Himalayan granites to address this issue. Autocrystic zircon had εHf values (at 20 Ma) of–12.0 to–4.3 (median =–9). Inherited zircon yielded εHf values (at 20 Ma) of–34.8 to +0.3 (median =–13); the majority of εHf values were lower than those of autocrystic zircon. The εHf values of inherited zircon with high U concentrations resembled those of autocrystic zircon. Geochemical data indicates that the granites were generated during relatively low-temperature (<800 °C) partial melting of metasedimentary rocks, which, coupled with kinetic hindrance, may have led to the preferential dissolution of high-U zircon that could dissolve more efficiently into anatectic melt due to higher amounts of radiation damage. Consequently, Hf values of autocrystic zircon can be biased toward the values of U-rich zircon in the source. By contrast, literature data indicate that granites generated at high temperatures (>820–850 °C) generally contain autocrystic and inherited zircons with comparable Hf isotope values. During higher-temperature melting, indiscriminate dissolution of source zircon until saturation is reached will result in near-complete inheritance of Hf isotope ratios from the source. Our results impose an extra layer of complexity to interpretation of the zircon Hf isotope archive that is not currently considered.
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Malitch, K. N., I. S. Puchtel, I. Yu Badanina, S. L. Votyakov, N. G. Soloshenko, E. A. Belousova, T. A. Velivetskaya, and A. V. Ignatiev. "Sources of Ore Material in the Platinum-Group Element Deposits of Polar Siberia and the Middle Urals Based on the Data from Radiogenic (Re–Os, Pt–Os) and Stable (Cu, S) Isotopes." Russian Geology and Geophysics 65, no. 3 (March 1, 2024): 366–87. http://dx.doi.org/10.2113/rgg20234681.
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Abstract —Understanding the main events of platinum-group element (PGE) ore formation is impossible without analysis of the sources and behavior of major ore-forming components, namely, platinum, osmium, sulfur, and copper, which are important indicators of magmatic and hydrothermal processes. In contrast to the Re–Os isotope system, the radiogenic Pt–Os isotope system, as well as stable isotopes of Cu and S in PGE deposits, are still relatively understudied. Our comprehensive research is aimed at filling this gap. The paper presents data for the Guli massif of ultramafic and alkaline rocks and carbonatites in Polar Siberia and on the zonal Nizhny Tagil and Svetly Bor clinopyroxenite–dunite massifs in the Middle Urals, which include: (1) the contents of the highly siderophile elements (HSE) in whole rocks and platinum-group minerals (PGM), (2) the Re–Os and Pt–Os isotope systematics of chromitite, Os–Ir alloys, and Ru–Os sulfides, (3) the sulfur isotope composition in Ru–Os and Ir–Rh sulfides in primary and secondary PGM assemblages, and (4) the copper isotope composition in Pt–Fe minerals from chromitites and placers. The research was performed using scanning electron microscopy, electron probe microanalysis, and high-precision isotope-geochemical analysis. The high-precision Re–Os and Pt–Os isotope data show that the HSE contents in chromitites and PGM of the Guli massif were controlled by the composition of the mantle source that evolved with near-chondritic time-integrated Re/Os and Pt/Os ratios, which are also typical of the sources of most komatiites and abyssal peridotites. The δ65Cu values of the studied samples of ferroan platinum and isoferroplatinum are identical within the analytical uncertainty and are close to 0‰, which is typical of high-temperature Cu-containing minerals. The sulfur isotope compositions of the Ir–Rh sulfides of the kashinite–bowieite series and of the Ru–Os sulfides of the laurite–erlichmanite series in the primary PGM assemblages indicate that the source of sulfur has a chondritic isotope composition, which is in agreement with the osmium isotope composition of the Ru–Os sulfides and Os–Ir alloys. The heavy sulfur isotope composition (δ34S = 5.6 ± 1.5‰) of As-containing erlichmanite is consistent with its secondary origin. The new data on the isotope compositions of osmium, copper, and sulfur can be used as new important parameters that characterize the sources of PGE mineralization.
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Wang, Jun, and Yangtong Cao. "Sulfur Isotopic Composition of Gypsum from Paleocene, Northwest China: Implications for the Evolution of Eastern Paratethys Seawater." Minerals 12, no. 8 (August 16, 2022): 1031. http://dx.doi.org/10.3390/min12081031.
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The sulfate isotope record of marine sedimentary sulfate through time has been used successfully to determine global variations in the composition of seawater sulfate. The variations in the sulfur isotope composition of marine sulfate reflect changes in the global sulfur cycle and are also closely related to changes in the atmospheric oxygen cycles. However, data for the Paleocene are very sparse and the stratigraphic evolution of the sulfur isotope composition of seawater is poorly constrained due to the small number of samples analyzed. The Yarkand Basin, as a northeastern part of the eastern Paratethys ocean with the trumpet-shaped bay, in which a suite of evaporitic sequences named the Aertashen Formation was continuously developed in the Paleocene and was principally composed of massive gypsum interbedded fragmental rocks. The values of sulfur isotopic composition are from 12.2‰ to 20.6‰ (δ34 SCDT or δ34 SVCDT) and the mean is 17.7‰ in 97 gypsum samples in the basin. Three gradually increasing trends of sulfur isotopic curves reflect that enrichment of δ34 S occurred in seawater sulfate, and indicate oxidation of seawater sulfide. These may hint to at least three oxidation events or the bacterial reduction of seawater sulfide that occurred in the Paleocene, and that three oxygen-enriched events or the biological sulfur cycle might exist in this epoch. The sulfur isotopic composition (δ34 SCDT or δ34 SVCDT) in the seawater of the northeastern part of the eastern Paratethys ocean was about 15.0‰ to 20.6‰, and averaged 17.9‰ in the Paleocene. Combined with the previous global sulfur isotopic composition of seawater, the final range of global sulfur isotopic composition of seawater might be from 15.0‰ to 21.0‰, with 17.9‰–18.3‰ the average in the Paleocene, so the variations in the sulfur isotope composition of Paleocene seawater sulfate are reconstructed and supplemented.
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Korte, Christoph, and Heinz W. Kozur. "Bio- and chemostratigraphic assessment of carbon isotope records across the Triassic–Jurassic boundary at Csővár quarry (Hungary) and Kendlbachgraben (Austria) and implications for global correlations." Bulletin of the Geological Society of Denmark 59 (December 19, 2011): 100–115. http://dx.doi.org/10.37570/bgsd-2011-59-10.
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Carbon isotope trends are useful for stratigraphic correlation, especially for time intervals when major perturbations of the global carbon cycle occurred. Such perturbations have been documented for the Triassic–Jurassic (T–J) boundary, and several successions from this time interval are characterized by (1) an initial negative excursion, followed by (2) a pronounced positive excursion and a subsequent (3) main negative carbon isotope excursion. These features, however, are not present in all T–J boundary sections, or the stratigraphic position of the positive or the main negative excursion has variable locations. In the present study, we analysed carbon isotopes in bulk carbonate from the pelagic Csővár quarry section in Hungary and from the intra-platform basin to shallow subtidal marine Kendlbachgraben section in Austria. Both T–J boundary successions are biostratigraphically well controlled enabling – with particular focus on the bio- and chemostratigraphy of other T–J boundary sections – correlation of the carbon isotope trends. This evaluation shows that the apex of the initial negative δ13C excursion occurred slightly, but distinctly, below the mass extinction event and represents an excellent stratigraphic correlation tool.
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Liu, Yidong, Aihua Zeng, Wenjun Chen, and Yangtong Cao. "The Sulfur Isotopic Characteristics of Evaporites in the Yarkand Basin of Xinjiang Province in the Paleocene and Its Paleoenvironmental Evolution." Minerals 13, no. 6 (June 15, 2023): 816. http://dx.doi.org/10.3390/min13060816.
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The Yarkand Basin, located in the southwest of the Tarim Basin, is a northeastern part of the eastern Paratethys ocean in the Paleocene, and a significant amount of evaporites, with gypsum, anhydrite, and halite as the main types, were developed in this area. These evaporites record the sedimentary environment at that time. A study was conducted on the sulfur isotopic composition of gypsum in the Paleocene of the Yarkand Basin to explore the origin of the evaporites and interpret the sedimentary environment. The experimentally measured sulfur isotope δ34SCDT values of 187 gypsum samples ranged from 6.69‰ to 25.92‰ with an average value of 18.64‰. The overall trend of the Paleocene gypsum sulfur isotopic curve is consistent with the global seawater sulfur isotopic curve, which shows a decreasing trend. In the early and middle Paleocene, the curve shows four stages of sulfur isotope increase, indicating that the sedimentary environment during that time was mainly influenced by bacterial reduction and a relatively open sedimentary environment, while the late period shows a decreasing trend, suggesting that the late period may be primarily influenced by terrigenous freshwater. In addition, the sulfur isotope value has the characteristics of decreasing from northwest to southeast of the basin, which may indicate that the sedimentary environment of Paleocene evaporites in the Yarkand Basin may also be related to paleotopography and distance from the estuary, resulting in differences in sedimentary environments. The mainly original sulfur isotope values of the Paleocene evaporites in the Yarkand Basin should be in the range of 18‰–20‰, which is a supplement to the Paleocene global paleoseawater and is of great significance for the reconstruction of the marine transgressive–regressive cycle and sulfur isotopic composition of the eastern Paratethys ocean during this period.
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Yoshida, M. "Second Symposium of South American Isotope Geology." Gondwana Research 3, no. 2 (April 2000): 268–70. http://dx.doi.org/10.1016/s1342-937x(05)70109-x.
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Price, T. Douglas, James H. Burton, Paul D. Fullagar, Lori E. Wright, Jane E. Buikstra, and Vera Tiesler. "Strontium Isotopes and the Study of Human Mobility in Ancient Mesoamerica." Latin American Antiquity 19, no. 2 (June 2008): 167–80. http://dx.doi.org/10.1017/s1045663500007781.
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We analyzed strontium isotopes in more than 500 samples of shell, bone, and dental enamel from modern and archaeological contexts throughout Mesoamerica. The results correspond closely with expectations based upon the local geology and earlier measurements of geological materials. The results show that isotopic variation is significant across Mesoamerica. Thus strontium isotope ratios in dental enamel, which mark the place of childhood residence, can be used not only to document mobility but also in some cases to determine geographic origin. We present five archaeological case studies to illustrate the anthropological significance and range of applications for this technique: the origins of individuals in the “Oaxaca Barrio” at Teotihuacan, a northern origin for the founder of Copan, a local king at Tikal, the regional origin of two of Palenque's rulers, and individuals of African birth in a colonial cemetery in Campeche.
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Price, T. Douglas, Joachim Wahl, and R. Alexander Bentley. "Isotopic evidence for mobility and group organization among Neolithic farmers at Talheim, Germany, 5000 BC." European Journal of Archaeology 9, no. 2-3 (2006): 259–84. http://dx.doi.org/10.1177/1461957107086126.
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The mass grave found near Talheim in southern Germany dates to approximately 7000 years ago and contains the skeletal remains of 34 individuals from the Early Neolithic period, associated with what is known as the Linearbandkeramik culture. These individuals appear to have been the victims of a massacre, based on the presence of numerous lethal head wounds, several arrow wounds, and the placement of all of these individuals in the same burial pit. The burials are considered to likely represent members of the same community attacked and executed by another group. In this study we examine the remains from the mass grave at Talheim for information on migration and community structure using strontium isotope ratios in tooth enamel. In essence, strontium isotope ratios are signatures of different rock types. The food chain moves these atoms into the human skeleton from bedrock through water, soils, plants, and herbivores. Because human tooth enamel does not change after formation, it provides a stored signal of the strontium isotopes of the place of birth. If the strontium isotope ratio of the place of death is different, the individual under study must have moved from one geology to another during his or her lifetime. Isotopic provenancing shows that several of the individuals in the group at Talheim were born in a different geological location. We discuss the results of the analysis and its significance in terms of questions of migration and community structure in the Early Neolithic of prehistoric Europe.
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Sanz-Montero, María E., Pablo del del Buey, Óscar Cabestrero, and Mónica Sánchez-Román. "Isotopic Signatures of Microbial Mg-Carbonates Deposited in an Ephemeral Hyperalkaline Lake (Central Spain): Paleoenvironmental Implications." Minerals 13, no. 5 (April 28, 2023): 617. http://dx.doi.org/10.3390/min13050617.
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Interpretation of stable isotope (C and O) composition of lacustrine carbonates requires in-depth knowledge about the interplay between the abiotic and biotic processes in sedimentary environments. The present study, focused on Mg-carbonates from a well-characterized alkaline and ephemeral lake, gives new insight into the behavior of the stable isotopes during the seasonal precipitation of a variety of carbonates. Dolomite and Mg-calcite precipitate intracellularly within Spirogyra during spring and show lighter isotopic signatures (δ13C aver. −4.10‰ and δ18O aver. −0.75‰, VPDB) than a second association of carbonates, such as hydromagnesite, northupite and traces of magnesite among other sodium-bearing carbonates (δ13C aver., −1.34‰ and δ18O aver. 4.52‰, VPDB). The latter precipitate in association with degraded microbial mats as the lake desiccates during summer. Covariant trends between carbonate δ13C and δ18O reflect isotope enrichment related to evapoconcentration. The seasonal cycling of inorganic carbon among carbonate minerals, microbial biomass, lake water and pore water was also analyzed, revealing variations of δ13C within a range of −12.40‰ to −0.43‰. The more depleted 13C derives from the decay of the microbial mats. The less negative values are distinctive of the bulk carbonates forming crusts in summer. Intracellular calcite and dolomite have δ13C and δ18O values (VPDB) ranging, from −5.45‰ to −3.07‰ and −2.48‰ to 1.58‰, respectively, that are intermediate between those two endmembers. These intracellular carbonates are enriched in 13C by 5‰ with respect to dissolved inorganic carbon (δ13C in the range of −11.79‰ to −6.87‰, VPDB) due to the vital effect of photosynthesis. The crust of carbonates deposited as the lake desiccates dissolve interannually. Alternatively, dolomite and Mg-calcite as well as their isotopic compositions persist during synsedimentary diagenesis, confirming that carbonate biominerals provide isotopic signatures related to the environmental conditions of formation with potential of preservation in the rock record.
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Wu, Fei, Simon Turner, and Bruce F. Schaefer. "Mélange versus fluid and melt enrichment of subarc mantle: A novel test using barium isotopes in the Tonga-Kermadec arc." Geology 48, no. 11 (June 25, 2020): 1053–57. http://dx.doi.org/10.1130/g47549.1.
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Abstract In the past few years, the so-called mélange model has been offered as an alternative to the long-standing model of enrichment of the subarc mantle by separate additions of fluid and sediment components from the subducting plate. In the mélange model, components from the subducting plate become physically mixed at the slab-mantle interface. Partial melting of the peridotite subsequently occurs after being hybridized by the mélange material that diapirically rises into hotter portions of the wedge. Here, we present the first Ba isotope study of lavas from the Tonga-Kermadec arc (southwest Pacific Ocean) and show that Ba isotopes distinguish between fluid and melt derived from different subducted components. This provides fresh constraints on the debate. Remarkable along-strike Ba isotope variations were observed and are best explained by contributions from variable proportions of sediment and altered oceanic crust (AOC) fluid from the subducting plate. Combined Ba-Sr-Pb isotope relationships indicate that sediment melt and AOC fluid were added to the source of the arc lavas separately at different times. This is inconsistent with the mélange model, at least in this arc.
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Wang, Peiyao, Yaoling Niu, Pu Sun, Xiaohong Wang, Pengyuan Guo, Hongmei Gong, Meng Duan, et al. "Iron Isotope Compositions of Coexisting Sulfide and Silicate Minerals in Sudbury-Type Ores from the Jinchuan Ni-Cu Sulfide Deposit: A Perspective on Possible Core-Mantle Iron Isotope Fractionation." Minerals 11, no. 5 (April 28, 2021): 464. http://dx.doi.org/10.3390/min11050464.
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Many studies have shown that the average iron (Fe) isotope compositions of mantle-derived rocks, mantle peridotite and model mantle are close to those of chondrites. Therefore, it is considered that chondrite values represent the bulk Earth Fe isotope composition. However, this is a brave assumption because nearly 90% of Fe of the Earth is in the core, where its Fe isotope composition is unknown, but it is required to construct bulk Earth Fe isotope composition. We approach the problem by assuming that the Earth’s core separation can be approximated in terms of the Sudbury-type Ni-Cu sulfide mineralization, where sulfide-saturated mafic magmas segregate into immiscible sulfide liquid and silicate liquid. Their density/buoyancy controlled stratification and solidification produced net-textured ores above massive ores and below disseminated ores. The coexisting sulfide minerals (pyrrhotite (Po) > pentlandite (Pn) > chalcopyrite (Cp)) and silicate minerals (olivine (Ol) > orthopyroxene (Opx) > clinopyroxene (Cpx)) are expected to hold messages on Fe isotope fractionation between the two liquids before their solidification. We studied the net-textured ores of the Sudbury-type Jinchuan Ni-Cu sulfide deposit. The sulfide minerals show varying δ56Fe values (−1.37–−0.74‰ (Po) < 0.09–0.56‰ (Cp) < 0.53–1.05‰ (Pn)), but silicate minerals (Ol, Opx, and Cpx) have δ56Fe values close to chondrites (δ56Fe = −0.01 ± 0.01‰). The heavy δ56Fe value (0.52–0.60‰) of serpentines may reflect Fe isotopes exchange with the coexisting pyrrhotite with light δ56Fe. We obtained an equilibrium fractionation factor of Δ56Fesilicate-sulfide ≈ 0.51‰ between reconstructed silicate liquid (δ56Fe ≈ 0.21‰) and sulfide liquid (δ56Fe ≈ −0.30‰), or Δ56Fesilicate-sulfide ≈ 0.36‰ between the weighted mean bulk-silicate minerals (δ56Fe[0.70ol,0.25opx,0.05cpx] = 0.06‰) with weighted mean bulk-sulfide minerals (δ56Fe ≈ −0.30‰). Our study indicates that significant Fe isotope fractionation does take place between silicate and sulfide liquids during the Sudbury-type sulfide mineralization. We hypothesize that significant iron isotope fractionation must have taken place during core–mantle segregation, and the bulk Earth may have lighter Fe isotope composition than chondrites although Fe isotope analysis on experimental sulfide-silicate liquids produced under the varying mantle depth conditions is needed to test our results. We advocate the importance of further research on the subject. Given the close Fe-Ni association in the magmatic mineralization and the majority of the Earth’s Ni is also in the core, we infer that Ni isotope fractionation must also have taken place during the core separation that needs attention.
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Jin, Luying, Kezhang Qin, Guangming Li, Junxing Zhao, Zhenzhen Li, Zhuyin Chu, and Guoxue Song. "Formation of the Chalukou High Fluorine-Type Mo (–Zn–Pb) Deposit, NE China: Constraints from Fluorite and Sphalerite Rare Earth Elements and Sr–Nd Isotope Compositions." Minerals 13, no. 1 (January 3, 2023): 77. http://dx.doi.org/10.3390/min13010077.
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Fluorite is a widespread mineral in porphyry and hydrothermal vein Mo-polymetallic deposits. Here, fluorite is utilised as a probe to trace the fluid source and reveal the fluid evolution process in the Chalukou giant Mo (Pb‒Zn) deposit, Northeast China, which is characterised as early porphyry Mo and later vein-style Zn–Pb mineralisation. A detailed rare earth element (REE) and Sr–Nd isotope study of fluorite combined with Sr isotopes of sphalerite is conducted for the Chalukou deposit. The chondrite-normalised REE patterns of fluorites from molybdenite veins show light REE (LREE)-enriched patterns, with negative Eu anomalies (δEu = 0.60) and weakly negative Y anomalies (Y/Y* = 0.72). The fluorites associated with sphalerite veins exhibit rare earth element (REE)-flat patterns with negative Eu anomalies (δEu = 0.65 to 0.99) and positive Y anomalies (Y/Y* = 1.37 to 3.08). In addition, during the progression from Mo to Zn–Pb mineralisation, the total concentration of REEs decreases from 839 ppm to 53.7 ppm, and Y/Ho ratios increase from 22.1 to 92.5. These features may be explained by the different mobilities of REE complexes during fluid migration. The Eu anomalies are considered to be inherited from source fluids. All the initial 87Sr/86Sr ratios of fluorite and sphalerite are between those of ore-forming porphyries and wall rocks (rhyolite), with fluorite ratios ranging from 0.706942 to 0.707386 and sphalerite ratios varying from 0.705221 to 0.710417. The majority of εNd(t) values of fluorite varying from −6.4 to −3.6 are also located between the ratios exhibited by ore-forming porphyries and rhyolite, whereas three εNd(t) values of fluorites ranging from −0.26 to 0.36 are close to those of ore-forming porphyries. All the isotopic features indicate that the Sr-Nd isotope ratios of hydrothermal fluid are derived from porphyries and disturbed by fluid–rock reactions. Together with a two-stage Sr–Nd isotope mixing model, we suggest that different sources and fluid‒rock interactions (syn-ore intrusions and strata) finally influence the Sr–Nd isotopes of the ore-forming fluids, which are recorded by the majority of fluorite and sphalerite.
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COLOMBIÉ, CLAUDE, CHRISTOPHE LÉCUYER, and ANDRÉ STRASSER. "Carbon- and oxygen-isotope records of palaeoenvironmental and carbonate production changes in shallow-marine carbonates (Kimmeridgian, Swiss Jura)." Geological Magazine 148, no. 1 (July 2, 2010): 133–53. http://dx.doi.org/10.1017/s0016756810000518.
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AbstractCarbon- and oxygen-isotope ratios are commonly used to correlate shallow- and deep-marine successions. Carbon- and oxygen-isotope analyses were performed on bulk-carbonate samples from two Kimmeridgian sections of the Swiss Jura platform in order to correlate them with biostratigraphically well-dated coeval sections in the adjacent basin. On the platform, a general decrease in δ13C and δ18O values from the base to the top of the studied interval is measured, whereas time-equivalent pelagic–hemipelagic carbonates record an increase in carbon- and oxygen-isotope ratios. Moreover, the measured δ13C and δ18O values are generally lower than those indicated for the Kimmeridgian open ocean and show high-frequency variations superimposed on the general trend. Samples were screened for diagenetic alteration using optical and cathodoluminescence petrography and coupled carbon- and oxygen-isotope and trace-element analyses. Some observations favour a role for diagenetic alteration, but isotopic and elemental trends as well as sedimentological evidence suggest that the more negative values of δ13C and δ18O relative to Kimmeridgian seawater are also due to local environmental conditions. High-frequency changes in δ18O and δ13C values most likely result from variations in salinity and carbonate production and accumulation rates. These variations were produced by different water masses that were isolated from the open ocean and developed their own geochemical signatures. Repeated isolation was induced by high-frequency sea-level fluctuations and helped by irregular platform morphology. Consequently, carbon- and oxygen-isotope records in shallow-marine carbonates can be used for stratigraphic correlation only if their origin is well known.
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Szőcs, Emese, and Kinga Hips. "Multiphase carbonate cementation in the Miocene Pétervására Sandstone (North Hungary): implications for basinal fluid flow and burial history." Geologica Carpathica 69, no. 6 (December 1, 2018): 515–27. http://dx.doi.org/10.1515/geoca-2018-0030.
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Abstract The paper focuses on the reservoir heterogeneity of a sandstone formation in which the main issue is the evaluation of diagenetic features. Integrated data from field observations as well as petrographic and geochemical analyses from surface and core sections from different structural settings were applied. In the shallow marine Pétervására Sandstone, eogenetic minerals are comprised of calcite, pyrite and siderite; mesogenetic minerals are albite, ankerite, calcite, quartz, mixed layer clays and kaolinite. Dissolution occurred during mesogenetic and telogenetic phases. Ankerite is only present in the core setting, where the sandstone is at ca. 900 m depth and diagenetic calcite predates quartz cementation. Based on stable isotopic values (δ13 CV-PDB −18.3 to −11.4 ‰ and δ18 OV-PDB −9.5 to −7.2 ‰), diagenetic calcite is of mesogenetic origin and was precipitated from fluids migrated along fault zones from the underlying, organic matter-rich formation. In outcrop setting, on the other hand, calcite is present in a larger quantity and postdates quartz cementation. Carbon isotope data (δ13 CV-PDB = −9.9 to −5.1 ‰) indicate less contribution of light isotope, whereas more negative oxygen isotopic values (OV-PDB = −13.1 to −9.9 ‰) likely imply higher temperature of mesogenetic fluids.However, carbon–oxygen isotope covariation can indicate precipitation from meteoric fluid. In this case, further analyses are required to delineate the final model.
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Yang, Zhen, Guiqin Wang, Yuming Xu, Yuling Zeng, and Zhaofeng Zhang. "A Review of the Lunar 182Hf-182W Isotope System Research." Minerals 12, no. 6 (June 15, 2022): 759. http://dx.doi.org/10.3390/min12060759.
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In recent years, the extinct nuclide 182Hf-182W system has been developed as an essential tool to date and trace the lunar origin and evolution. Despite a series of achievements, controversies and problems exist. As a review, this paper details the application principles of the 182Hf-182W isotope system and summarizes the research development on W isotopes of the Moon. A significant radiogenic ε182W excess of 0.24 ± 0.01 was found in the lunar mantle, leading to heated debates. There are three main explanations for the origin of the excess, including (1) radioactive origin; (2) the mantle of the Moon-forming impactor; and (3) disproportional late accretion to the Earth and the Moon. Debates on these explanations have revealed different views on lunar age. The reported ages of the Moon are mainly divided into two views: an early Moon (30–70 Ma after the solar system formation); and a late Moon (>70 Ma after the solar system formation). This paper discusses the possible effects on lunar 182W composition, including the Moon-forming impactor, late veneer, and Oceanus Procellarum-forming projectile. Finally, the unexpected isotopic similarities between the Earth and Moon are discussed.
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Demeny, Attila, Ágnes Berentés, László Rinyu, Ivett Kovács, Gergely Surányi, and Magdolna Virág. "Subaqueous carbonate speleothems as paleotemperature archives – clumped isotope thermometry and stable isotope compositions of inclusion-hosted water." International Journal of Speleology 53, no. 1 (February 2024): 25–37. http://dx.doi.org/10.5038/1827-806x.53.1.2480.
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Clumped isotope measurements of carbonates and stable isotope analyses of water trapped in fluid inclusions are both promising techniques to determine carbonate formation temperatures. Cave-hosted carbonate deposits (speleothems) are excellent targets for such studies, but kinetic fractionations and diagenetic influences frequently deteriorate the temperature data obtained from these methods. However, subaqueous carbonate deposits may provide reliable data, as kinetic fractionations are less significant in underwater environments. In this study, subaqueous speleothems, whose formation temperatures were directly measured in the water, were investigated. Additionally, temperatures calculated from the oxygen isotope fractionations between calcite and fluid inclusion-hosted water were compared with clumped isotope temperatures obtained for subaqueous carbonate formations in cave-hosted lakes. The clumped isotope temperatures fit the measured and calculated fluid inclusion temperatures within the analytical precisions. Carbonate deposits formed at elevated temperatures (~50°C or above) may undergo post-formational calcite-water oxygen isotope exchange, altering the composition of the inclusion-hosted water. In contrast, subaqueous speleothems formed at about 20-25°C appear to preserve the primary isotopic compositions. Our study shows that subaqueous carbonate speleothems are useful targets for clumped isotope and inclusion water analyses, making them valuable paleotemperature archives.
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Brasier, M. D., G. Shields, V. N. Kuleshov, and E. A. Zhegallo. "Integrated chemo- and biostratigraphic calibration of early animal evolution: Neoproterozoic–early Cambrian of southwest Mongolia." Geological Magazine 133, no. 4 (July 1996): 445–85. http://dx.doi.org/10.1017/s0016756800007603.
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AbstractFive overlapping sections from the thick Neoproterozoic to early Cambrian sediments of western Mongolia were analysed to yield a remarkable carbon-isotope, strontium-isotope and small shellyfossil (SSF) record. Chemostratigraphy suggests that barren limestones of sequences 3 and 4, which lie above the two Maikhan Uul diamictites, are post-Sturtian but pre-Varangerian in age. Limestones and dolomites of sequence 5, withBoxonia grumulosa, have geochemical signatures consistent with a post-Varangerian (Ediacarian) age. A major negative δ13C anomaly (feature ‘W’) in sequence 6 lies a shortdistance above anAnabarites trisulcatusZone SSF asemblage with hexactinellid sponges, of probable late Ediacarian age. Anomaly ‘W’ provides an anchor point for cross-correlation charts of carbon isotopes and small shelly fossils. Trace fossil assemblages with a distinctly Cambrian character first appear in sequence 8(PurellaZone), at the level of carbon isotopic feature ‘B’, provisionally correlated with the upper part of cycle Z in Siberia. A paradox is found from sequence 10 to 12 in Mongolia: Tommotian-type SSFs continue to appear, accompanied by Nemakit-Daldynian/Tommotian-type87Sr/86Sr ratios but by increasingly heavyδ13C values that cannot be matched in the Tommotian of eastern Siberia. The steady rate of generic diversification in Mongolia also contrasts markedly with the Tommotian ‘diversity explosion’ in eastern Siberia, which occurs just above a major karstic emergence surface. One explanation is that sequences 10 to 12 in Mongolia preserve a pre-Tommotian portion of the fossil record that was missing or removed in easternSiberia. The Mongolian sections certainly deserve an important place in tracing the true course and timing of the ‘Cambrian radiation’.