Vanadium (V) isotope analysis of geological samples with high Ti/V is analytically challenging due to the formation of Ti-rich precipitates during digestion and Ti-induced interferences during purification and mass spectrometry. Here, a four-column chromatographic purification protocol is established for efficient V separation from Ti-rich matrices. Digestion in concentrated acids suppresses precipitate formation, and sequential column chromatography under strongly acidic conditions enables the effective removal of Fe and Ti using AG1-X8 and LN-B50-S resins. Residual matrix elements are further eliminated under weakly acidic conditions with AG50W-X12 and AG1-X8 resins. Systematic experiments employing variable Ti/V ratios and controlled sample loading were performed to constrain the practical loading capacity of the purification scheme. Quantitative V recovery higher than 99.9% and long-term external precision better than +/- 0.10 parts per thousand (2 SD) were achieved. High-precision delta 51V data are reported for nine geological reference materials, demonstrating the robustness of the protocol for high Ti/V systems.

The first trilobite mass extinction, known as the Redlichiid-Olenellid extinction, occurred at the Cambrian Series 2-3 boundary and is associated with the Redlichiid-Olenellid Extinction negative Carbon isotope Excursion (ROECE). The causes of the ROECE event remain debated, with some researchers attributing it to the Kalkarindji volcanism and others linking it to a coeval large-scale transgression event. Continuous seawater sulfur isotope records across this boundary are crucial for resolving this debate. In this study, we present sulfur isotope data of carbonate-associated sulfate (CAS) across the Cambrian Series 2-3 boundary from the Xiaoerbrak section, Tarim Basin and reconstruct a seawater S34S variation curve for this critical period. Our findings show that seawater S34S values were likely positively coupled with S13C values during Cambrian Series 2 but showed an abrupt increase across the Series 2-3 boundary, marking a shift from coupled to decoupled carbon-sulfur isotope behaviour. According to the prevailing ROECE hypothesis, this decoupling of carbon and sulfur isotopes may be caused by isotopically light carbon inputs to surface water from Kalkarindji volcanism or from anoxic bottom water. These two hypotheses are tested quantitively using a biogeochemical box model. The modelling results show that light carbon emission from volcanism is insufficient to explain the recorded seawater isotope variations. Instead, the best fit comes from a dissolved organic carbon (DOC) oxidation hypothesis, an updated version of the anoxic bottom water shoaling/upwelling hypothesis. This hypothesis posits that DOC-enriched anoxic bottom water was upwelled and oxidised by oxygen during a large-scale transgression, leading to a negative seawater S13C excursion. Along with oxygen consumption and expanded anoxia, increased pyrite burial resulted in a sharp rise in seawater S34S at the Cambrian Series 2-3 boundary. The proposed DOC oxidation hypothesis effectively explains the decoupled carbon and sulfur isotope behaviour at this boundary and highlights the significant role of reduced oxygen levels in the Redlichiid-Olenellid extinction.

The Lower Paleozoic Qiongzhusi Formation is an important next target for shale gas exploration and development in South China, following the Wufeng-Longmaxi Formation. The total organic carbon (TOC) content is a key indicator of shale gas enrichment; however, systematic comparative studies of the factors controlling the organic matter enrichment of the Qiongzhusi Formation shales across the western Hunan-Hubei and northern Guizhou region are lacking. In this study, we compared the sedimentological and geochemical characteristics of the Qiongzhusi Formation shale deposited at the passive continental margin versus within the cratonic depression in the western Hunan-Hubei and northern Guizhou region and explored the main controlling factors and formation models of the differential organic matter enrichment. The results show that the shale intervals with high TOC values are located at the base of the Qiongzhusi Formation and were formed in environments characterized by low terrigenous input, high paleoproductivity, and favorable preservation conditions. Subsequently, the basin rifting gradually weakened, and the sea level continuously fell, which manifested as increased terrigenous input and deteriorating preservation conditions. In addition, the ocean current activity weakened as the sea level fell, resulting in a corresponding decline in the paleoproductivity. Therefore, the vertical decrease in the TOC content of the Qiongzhusi Formation was jointly controlled by the reduced paleoproductivity, poorer preservation conditions, and increased terrigenous input. Laterally, from the passive continental margin toward the interior of the cratonic depression, both the sea level and the intensity of the oceanic circulation exhibited decreasing trends, accompanied by simultaneous deterioration of the preservation conditions and paleoproductivity, resulting in progressively lower TOC contents.

In this study, we analyzed trace-element and S-Cd isotopic compositions of sphalerite and related igneous rocks from four representative skarn deposits in southern Hunan Province, southeastern China. These include the Shuikoushan (SKS), Tongshanling (TSL), and Baoshan (BS) Zn-Pb(-Cu) deposits associated with granodiorite porphyry, and the Huangshaping (HSP) Zn-Pb-W deposit related to granite porphyry. Our results indicate that sphalerite from the SKS deposit exhibits consistent delta 114/110Cd and delta 34S values near 0 parts per thousand, with Zn/Cd ratios resembling those of typical high-temperature mineralization systems. In contrast, sphalerite from the BS and TSL deposits shows lower delta 114/110Cd and Zn/Cd ratios but higher delta 34S values, suggesting that although the granodiorite porphyry was the primary source of Zn-Pb mineralization in these three deposits, the carbonate strata contributed additional sulfur and metals to the BS and TSL systems. Meanwhile, sphalerite from the HSP deposit is characterized by elevated delta 114/110Cd, delta 34S, and Zn/Cd ratios, implying that hydrothermal circulation through basement rocks played a dominant role in metal and sulfur extraction, with evaporite layers providing heavy sulfur. Integrating these findings with previous petrological data, we propose that lower crustal melting alone was sufficient to generate Zn-Pb mineralization. Additional contributions from dehydrated and melted sub-ducted slabs, together with upper crustal melting, further led to the superposition of Cu and W-Sn mineralization in southern Hunan Province.

The sulfur isotopic composition of marcasite (FeS2, orthorhombic), a dimorph of pyrite (FeS2, isometric), can be used to trace ore-forming fluid source(s) and ocean acidification events in deep time. However, matrix-matched standards for marcasite are scarce, and in practice, a pyrite standard is commonly used to calibrate the sulfur isotope ratio of marcasite during laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) and secondary ion mass spectrometry (SIMS) analyses. Recently, it has been suggested that it is feasible to calibrate the sulfur isotope ratio of marcasite with a pyrite standard during SIMS analysis, but the crystal orientation effect during sulfur isotope analysis of marcasite using SIMS remains unexplored. We investigated this topic by analyzing a natural marcasite sample (NJUMc-1). We analyzed NJUMc-1 using LA-MC-ICP-MS and SIMS. The analysis spots for LA-MC-ICP-MS and SIMS were very close to each other, and both spots were located in domains with the same brightness in backscattered electron images (BSE). The results derived from these two methods lie around a 1 : 1 line in a delta(34)S(LA-MC-ICP-MS)vs. delta S-34(SIMS) binary diagram, indicating that SIMS data are comparable to LA-MC-ICP-MS data. However, there are some grains in which delta S-34(LA-MC-ICP-MS) deviates from delta S-34(SIMS) ("delta S-34(LA-MC-ICP-MS_NJU) - delta S-34(SIMS)" >+2 parts per thousand or <-2 parts per thousand). This discrepancy possibly indicates a crystal orientation effect during SIMS analysis. To confirm whether there is a crystal orientation effect during SIMS analysis, we conducted a second round of LA-MC-ICP-MS analysis in Beijing and selected two sets of NJUMc-1 marcasite grains and conducted electron backscatter diffraction (EBSD) analysis. For the first set of NJUMc-1 grains, characterized by variable "delta S-34(LA-MC-ICP-MS_Beijing) - delta S-34(SIMS)" values, there is no correlation between crystal orientation and "delta S-34(LA-MC-ICP-MS_beijing) - delta S-34(SIMS)" values. For the second set of NJUMc-1 grains, characterized by "delta S-34(LA-MC-ICP-MS_Beijing) - delta S-34(SIMS)" values around 0 parts per thousand, highly variable crystal orientations are observed. These findings suggest that if a crystal orientation effect exists during SIMS analysis, it should be no larger than 1.5 parts per thousand.

Oxygenic photosynthesis played an essential role in the accumulation of free oxygen (O2) at Earth’s surface, but questions persist regarding its evolutionary timeline. Manganese (Mn)-rich sedimentary rocks from the Mesoarchean Pongola Supergroup in South Africa have been invoked among the earliest evidence for O2-dependent Mn(II) oxidation and thus photosynthetic O2 production in oceans. However, as a singular suite of rocks, uncertainties persist about whether the evidence for O2 in the Pongola region has global implications. Here we report on another Mesoarchean Mn-rich iron formation in South China, dating back to ca. 2.88−2.80 Ga. The Dianzihe iron formation exhibits a positive correlation between Mn enrichment (MnO up to 7.08 wt%, Fe/Mn ratio down to 5.1) and negative δ56Fe values (−0.21 to −1.33‰; average = −0.91‰). This pattern requires oxygenated seawater (i.e., O2 > 10 μM) at least to the seafloor, allowing not only for the oxidation of Fe(II) and Mn(II) but also for the preservation of Fe(Mn) oxyhydroxides until post-depositional modifications. Based on our findings in China alongside the distribution of Mn-rich iron formations in South Africa, we posit that a global distribution of oxygen oases, driven by cyanobacterial O2 production, already existed in the Mesoarchean.

The characteristics of coal-bearing source rocks in the continuous sedimentary environment of the Xujiahe Formation are discussed in the Southwest Sichuan through the thermal simulation and organic geochemical experiments, and the quantitative relationships are determined between carbon isotopes, maturity, and distinct organic matter (OM) types. The results show that the source rocks of the first member and third member of the Xujiahe Formation are mainly formed in the transitional sedimentary environment, while the source rocks of the fifth member of the Xujiahe Formation are primarily developed in the continental sedimentary environment, controlled by the continuous sedimentary environment of the Xujiahe Formation. The vitrinite and inertinite content increases with the liptinite content decreasing from the first member to the fifth member of the Xujiahe Formation. Moreover, the OM of the source rocks is typed II2 in the first member of the Xujiahe Formation, with the III OM in the third member and fifth member of the Xujiahe Formation. Additionally, the quantitative relationship is identified between methane carbon isotopes and maturities of the humic and mixed gas. The quantitative relationship is presented at δ 13C1 = 12.21 ln Ro – 39.72 (humic gas) and δ 13C1 = 8.07 ln Ro – 38.3 (mixed gas). The ethane carbon isotopes range from −24.93 to −21.07‰ in the first member and the third member of the Xujiahe source rocks, and are between −29.31 and −26.78‰ in the fifth member of the Xujiahe source rocks, which can effectively distinguish the OM type by ethane carbon isotopes. The emergence of new recombined heavy hydrocarbons leads to the carbon isotope inversion of heavy hydrocarbon in the high thermal evolution stage. This study has contributed to the hydrocarbon-generating characteristics of source rocks in the continuous sedimentary environment and the fine gas source correlation.

The ocean crust remnants of the Proto-Tethys were preserved as the Kudi ophiolites in the West Kunlun Orogenic Belt (WKOB), and its evolutionary history was mainly constructed by research on igneous or metamorphic rocks in the WKOB. Sedimentary rocks in the WKOB received little attention in the past; however, they could provide important constraints on the evolution of the oceanic lithosphere. Here, a series of shales and greywackes found in the Kudi area of WKOB were studied to constrain their deposition ages and explore their significance in the evolution of the Proto-Tethys oceanic crust. The U-Pb dating and europium anomaly (Eu/Eu*) were analyzed for detrital zircons from greywackes interlayers, while bulk rare earth elements and yttrium (REY) of the shales were measured. Detrital zircons U-Pb ages yield a maximum deposition age of 436 Ma for the greywackes and black shales, while the REY distribution patterns of the black shales are similar to those of the Tarim Ordovician Saergan shales. Accordingly, the studied WKOB black shales were deposited in the Proto-Tethys Ocean during the Late Ordovician–Early Silurian period. The maximum deposition age at 436 Ma may represent a minimum closure time of the Proto-Tethys Ocean, which is also supported by the absence of increases in Eu/Eu* values during the Late Ordovician–Early Silurian. Besides, our Eu/Eu* values in detrital zircons indicate diminished orogenesis during the Archean to Meso–Proterozoic, subduction-related accretion at the margins of the supercontinent Rodinia during the Neoproterozoic.

Highly metalliferous black shales, enriched in trace metals like nickel and molybdenum, are valuable archives for reconstructing ancient marine environment and metal cycling. Despite various metallogenic models, the mechanisms driving Ni-Mo mineralization remain unclear, with limited attention to continuous stratigraphic profiles and environmental context. To address this, we apply the coupled S98Mo-S60Ni isotopic approach, along with multi-proxy geochemical data, to a continuous early Cambrian section (Songlin section) and compares with three other Ni-Mo-enriched deposits across South China (Zunyi, Nayong and Zhangjiajie). S98Mo values range from-0.3 %o to +2.1 %o and S60Ni from-0.4 %o to +0.8 %o, with a strong positive correlation (R2 = 0.51). Consistent trend between ore layers and host rocks suggests co-fractionation of Mo and Ni isotopes through adsorption onto Fe-Mn (hydro)oxides. Stratigraphic trends suggest a three-stage paleoenvironmental evolution, with intensified euxinia and upwelling during Member II deposition favoring Ni-Mo precipitation. While euxinia and organic matter burial contributed to metal retention in the sediments, these factors alone cannot fully explain the isotope variations. We propose that redox-sensitive Fe-Mn (hydro)oxide cycling, modulated by variable redox, upwelling and primary productivity conditions, serves as the primary control on the metal accumulation. Comparable isotopic patterns in other metalliferous shales along the earth's history suggest a common mechanism during global redox transitions. This study underscores the potential of coupled S98Mo-S60Ni as powerful tracers for marine metal cycling and paleoredox reconstruction, offering new insights into the role of ocean chemistry in metal deposition during key redox transitions in the Earth's past.

During the Cambrian Explosion, episodic radiations of major animal phyla occurred in concert with repeated coupled carbon‐sulfur isotope excursions. These isotope patterns are thought to reflect oscillations in atmospheric and shallow‐marine O 2 , which promoted animal diversification events. However, the driver for oxygenation pulses is unclear. Here we show that these synchronous carbon‐sulfur isotope cycles and marine oxygenation pulses can be driven by long‐period orbital forcing through effects on continental weathering and nutrient delivery. The impact of orbital forcing is explored using a combined climate‐biogeochemical model. When forced with latitudinally‐resolved insolation signals, the model produces long‐term variations in nutrient weathering and carbon burial, which reproduces the co‐variation of carbon‐sulfur isotopes. We conclude that the oxygen‐driven evolutionary changes in the early Cambrian can be explained by recurrent nutrient inputs to the ocean, resulting from climate change caused by long‐period orbital cycles.

Barite serves as a crucial archive for reconstructing sulfur cycling evolution throughout geologic history. Microscale space variations in sulfur isotope compositions (delta 34S) of barite provide valuable insights into the barite precipitation process. While secondary ion mass spectrometry (SIMS) microanalysis has emerged as a powerful tool for such investigations, the availability of high quality reference materials remains a fundamental requirement for accurate measurements. Although several barite reference materials have been developed for SIMS analysis, the potential influence of crystallographic orientation on sulfur isotope measurements has not been systematically evaluated. Moreover, the development of more in situ barite reference materials with diverse sulfur isotopic compositions would greatly facilitate cross-laboratory data comparison. In this study, we conducted a comprehensive investigation of the crystallographic orientation effect by combining electron backscatter diffraction (EBSD) and SIMS analyses. Our results demonstrate that crystallographic orientation does not produce significant analytical bias in SIMS barite sulfur isotope measurements at current levels of analytical precision. Furthermore, we present two new well-characterized potential reference materials NJU-Ba-1 and NJU-Ba-2 barite specifically developed for microbeam sulfur isotope analysis. Detailed characterization of texture and major element composition confirms the absence of internal zoning in ground fragments from both barite specimens. These two reference materials establish an extended delta 34SV-CDT calibration range for microanalytical studies, with certified values of 6.18 +/- 0.34 parts per thousand (2SD, N = 17) and 14.16 +/- 0.26 parts per thousand (2SD, N = 9) for NJU-Ba-1 and NJU-Ba-2 respectively, as determined by gas-source isotope ratio mass spectrometry (GS-IRMS). Extensive SIMS analyses revealed exceptional homogeneity at both inter- and intra-unit scales, with delta 34S variations of 0.36 parts per thousand (2SD, N = 328) for NJU-Ba-1 and 0.45 parts per thousand (2SD, N = 343) for NJU-Ba-2. These performance characteristics indicate that NJU-Ba-1 and NJU-Ba-2 are promising candidates as reference materials for high-precision microanalytical studies of barite sulfur isotopes.

The prevailing view that solid-state diffusion is negligible at low temperatures is challenged by rapid sulfur and barium isotope exchange between natural barite crystals and aqueous solutions in laboratory experiments. This assumption relies on diffusivities extrapolated from high-temperature experiments. Here, isotope exchange rates were measured in solutions enriched with 137Ba and 32S at 50 and 80 oC for less than 10,360 hours. SIMS depth profiles revealed 137Ba enrichment to 75 nm, with shapes characteristic of classical diffusion. Isotope disequilibrium between the barite surface and aqueous solution implies a continuous supply from the interior. These results indicate that defects and vacancies in barite and similar low-temperature minerals enable effective solid-state diffusion, with profound implications for paleoenvironmental reconstructions, materials science, and engineering.

On the basis of a one-dimensional transport-reaction model, we propose a novel approach to identify the relationship between the depth of the sulfate-methane transition (SMT) and the stratigraphic distribution of authigenic sulfide minerals in terms of both concentration and sulfur isotopic composition. We apply this approach to Ocean Drilling Program Sites 994 and 995 at the Blake Ridge, offshore southeastern North America. Within the present-day sulfate reduction zone, our numerical simulation suggests that sulfide mineralization is basically at a steady state, the concentrations of which depend largely on the reactivity of sedimentary organic carbon. The observed extreme 34S-depletion of sulfide minerals (e.g., delta 34S values as low as - 45 parts per thousand VCDT) can occur without the process of sulfur disproportionation. We then derive a series of theoretical profiles by changing the SMT depth from 4 m to 30 m below the seafloor and construct a contour plot of the theoretical SMT depth as a function of the concentration and sulfur isotopic composition of solid-phase sulfides after complete mineralization under steady-state conditions. Below the present-day SMT, six stratigraphic locations of the ancient SMT are identified and their depths below each contemporaneous seafloor are interpolated. Theoretical estimates suggest that the SMT gradually subsided from 8.4 to ca. 24 m below the contemporaneous seafloor (mbcsf) over the past 643 to 6.6 ka. At present, the SMT has been occurring steadily at depths of ca. 21 to 22 mbcsf for at least 2.9 kyr. This is the first time that the evolution of the ancient SMT depth has been quantitatively reconstructed, by which the attainment of knowledge can be used to research the early diagenetic evolution history of the pore water sulfur species and will arouse much interest and concern from other researchers.

Barium isotope compositions (S138Ba) represent a novel tracer for elucidating complex interactions between marine Ba cycling dynamics, paleoproductivity, and seawater redox evolution in ancient oceans. Here we present integrated S138Bacarb values and Ce/Ce* ratios from Lower Cambrian carbonates (Yurtus Formation, Xiaoxigou section, Tarim Basin). The studied carbonates record substantial S138Bacarb variations (-0.46 %o to +0.69 %o), with three prominent negative excursions interrupting baseline values comparable to modern open-ocean signatures. In combination with Ce/Ce* and S13Ccarb data, we interpret that the two stratigraphically lower negative S138Bacarb excursions, synchronized with a negative S13C shift, correspond to a transgressive event involving incursions of deep anoxic seawater. In contrast, the third negative S138Bacarb excursion, coincident with a positive S13C shift, points to the expansion of deep-water anoxic/euxinic conditions coupled with enhanced organic carbon burial. These findings collectively suggest highly dynamic barium cycling in the early Cambrian seawater of the northwestern Tarim Basin, with active, modern-like barium cycling in shallow waters episodically disrupted by incursions/upwelling of anoxic deep waters. Notably, while elevated Ce/Ce* ratios generally correspond to S138Bacarb decreases, the decreasing Ce/Ce* alongside sustained S138Bacarb decline during the third S138Bacarb excursion highlights decoupled redox evolution between shallow and deep water masses. While lowered Ce/Ce* values imply intensified oxygenation in shallow marine settings, synchronous increase in S13Ccarb and decrease in S138Bacarb collectively argue for the expansion of anoxic-euxinic conditions in deeper water masses. The coupled S138Bacarb and Ce/Ce* systematics thus provides complementary constraints for resolving redox evolution across vertically stratified water masses.

User-friendly chromatographic procedures using Chelex-100 achieve high recovery and minimize procedural blanks in nickel isotope analysis.

Two accretionary sediment sequences from Sites 1245 and 1252 recovered during Ocean Drilling Program (ODP) Leg 204 at southern Hydrate Ridge were investigated to explore the response of geochemical partitioning of iron and sulfur isotopic composition of authigenic pyrite to non-steady-state depositional and diagenetic scenarios. Five iron species were characterized by a modified sequential extraction procedure that covers almost all iron-bearing minerals in sediment cores, including: (1) iron-bearing carbonates, mainly siderite; (2) ferric (hydr)oxides, probably ferrihydrite and/or lepidocrocite; (3) magnetite; (4) iron-bearing silicates; and (5) pyrite. Highly reactive iron has been accumulated for a long-term steady-state history and its pyritization, to varying degrees, is limited by availability of dissolved sulfide. This causes pyrite and siderite occurred in the same sedimentary layer and shows an inverse relationship between their concentrations. From this, their proportions to highly reactive iron can be chosen for evaluating the degree of sulfidization. A significant change in sulfur isotopic composition of pyrite (-42.4 to +16.8‰ VCDT) indicates that the steady-state conditions are dramatically limited, where the δ34S values higher than -20‰ may result from an upward shift of SMT zone close to the seafloor or a sudden, massive depositional event. To explain the downcore sulfidization effects and pyrite δ34S values, we developed two categories of conceptual scenarios based on variations in sedimentation rate and methane flux. The geochemical features similar to those derived from each scenario were searched in the sediment columns and the non-steady-state events behind the scenarios were proved to be consistent with the real observations. Thus, iron species and pyrite δ34S values can be regarded as a proxy to differentiate different non-steady-state depositional and diagenetic controls on the sedimentary record.

Coal tar pitch (CTP) has become an ideal choice in the preparation of anode precursors for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) because of its abundant carbon content, competitive pricing and adjustable structure properties. In this paper, sulfurized pitch-based carbon (SPC-800) was obtained by allowing CTP to react with sulfur at 350 °C and subsequently achieve carbonization at 800 °C. SPC-800 was more disordered and had a larger layer spacing than carbonized CTP (PC-800). Upon utilization as an anode for LIBs, SPC-800 possessed a higher reversible specific capacity (478.1 mAh g−1 at 0.1 A g−1), while utilization in SIBs displayed a capacity of 220.9 mAh g−1 at 20 mA g−1. This work is an important guide to the design of high-performance anodes suitable for use with both LIBs and SIBs.