Institute of Geochemistry

• Establishes the first precise mineralization age (230–240 Ma, Middle Triassic) for the Juyuan tungsten deposit using multi-method geochronology (in-situ zircon and wolframite/scheelite U-Pb, and muscovite Ar-Ar dating). • Identifies a coeval, highly fractionated I-type granite (242.0 ± 1.2 Ma) as the metallogenic source, formed in a post-orogenic intraplate extensional setting. • Extends the East Tianshan Triassic tungsten belt eastward, revealing significant quartz vein-type tungsten potential in the western Beishan orogenic belt. The Beishan Orogenic Belt, situated on the southern margin of the Central Asian Orogenic Belt, represents a significant endogenous metallic mineral resource base in northwestern China. Previous studies have indicated that tungsten mineralization in the Beishan Orogenic Belt primarily occurred from the Early Silurian to Middle Carboniferous. However, whether quartz vein-type tungsten mineralization developed during the Middle Triassic remains controversial. This study focuses on the newly discovered Juyuan tungsten deposit in the western segment of the Beishan Orogenic Belt. We investigated the geological characteristics, tectonic setting, and timing of magmatism and mineralization, establish a metallogenic model for the Juyuan deposit, and compare it with typical regional tungsten deposits to provide guidance for future mineral exploration through systematic fieldwork, geochemical analyses, and isotopic geochronology, and show that the zircon U-Pb age of the monzogranite in the mining area is 242.0 ± 1.2 Ma. The granite exhibits high SiO 2 , high alkalinity, high Al 2 O 3 , and low CaO characteristics, identifying it as a highly fractionated I-type granite formed in a post-orogenic intraplate extensional setting. The 40 Ar- 39 Ar plateau age of muscovite from the ore-bearing quartz veins is 239.97 ± 0.98 Ma, while the insitu U-Pb ages of wolframite and scheelite are 232 ± 14 Ma and 236 ± 24 Ma, respectively, collectively constraining the mineralization age to between 230 and 240 Ma. This study demonstrates that the Juyuan tungsten deposit is a quartz vein-type tungsten deposit closely related to magmatic-hydrothermal processes. The East Tianshan Triassic tungsten metallogenic belt can be extended eastward into the Beishan Orogenic Belt, indicating significant potential for exploring quartz vein-type tungsten deposits in an intraplate extensional setting in its western segment.

A series of mononuclear-aromatic des-A-triterpenoids (MADATTS) and des-A-triterpenoids (DATTS) were simultaneously detected in terrestrial oils from the Baiyun Sag, Pearl River Mouth Basin, South China Sea. Besides five previously reported MADATTS, i.e., C23 mononuclear-aromatic des-oleanane (C23MADAO), C23 mononuclear-aromatic des-ursane (C23MADAU), C24MADAO, C24MADAU, and C26MADAU, this study identified a novel molecular marker in these oil samples, namely C26 mononuclear-aromatic des-oleanane (C26MADAO). C26MADAO elutes before C26MADAU in m/z 187 and 352 → 187 chromatograms, with a molecular ion at M+·352, base peak ion at m/z 187, and diagnostic ion fragment at m/z 199, 213, and 337. MADATTS with the same carbon number and identical substitutions on the B-ring exhibit strong positive correlations in their chromatographic peak abundance but show no evident correlation with the DATTS counterparts that share corresponding similar molecular skeletons, indicating that the formation mechanisms of the two series of compounds are different. In addition, the chromatographic peak abundance of both MADATTS and DATTS shows strong correlations with the C29 diasteranes/C29 regular steranes (C29-DiaSt/C29-St) and C30 rearranged oleananes/C30 hopane ((I + II + III)/C30H), which possibly reflects that their formation process is jointly controlled by terrestrial organic inputs and the catalysis of acidic clay minerals. Based on the sedimentary facies characteristics, conventional biomarker parameters, and distribution patterns of MADATTS and DATTS, this study finely reclassifies the Baiyun Sag oils into five groups and provides a comprehensive interpretation of their origins across different subregions.

Iron and sulfur isotope geochemistry serves as a powerful tool for probing diverse geological processes, spanning igneous, metamorphic, sedimentary, hydrothermal, and biological systems. Pyrite, a ubiquitous iron and sulfur-bearing mineral in various rock types and the predominant sulfide in hydrothermal ore deposits, is a common product throughout hydrothermal mineralization stages. The coupled Fe-S isotopic system in pyrite offers crucial constraints on fluid sources, fluid–rock interaction, and the physicochemical and redox conditions during mineral precipitation.In contrast to conventional bulk analytical methods, in situ microanalytical techniques—notably laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) and secondary ion mass spectrometry (SIMS, mainly for S isotopes)—permit to investigate Fe and S isotopic variations and fine-scale heterogeneity at high spatial resolution, which is essential for deciphering complex, multistage hydrothermal systems. The broader application of these techniques, however, is currently limited by the lack of matrix-matched reference materials with well-characterized Fe and S isotopic compositions.Here, we assess a natural pyrite sample (IGGPy-1) for its major-element and Fe–S isotopic homogeneity. Bulk analysis by elemental analyzer–isotope ratio mass spectrometry (EA-IRMS) yields a δ34SVCDT value of +17.09 ± 0.30‰. Solution-nebulization MC-ICP-MS (SN-MC-ICP-MS) gives δ56FeIRMM‑014 and δ57FeIRMM‑014 values of –1.31 ± 0.06‰ and –1.94 ± 0.12‰, respectively. These results position IGGPy-1 as a promising candidate reference material for in situ Fe–S isotopic microanalysis of pyrite.

Iron isotope ratios of Fe(‐Ti) oxide minerals have been widely used in constraining different geological processes. Laser ablation‐MC‐ICP‐MS has been commonly used to identify subtle Fe isotopic variations of these iron oxides, but matrix‐matched reference materials for calibration are still lacking. Here, five mineral pellets were prepared using a high‐temperature and high‐pressure sintering method. These pellets are proved to be homogenous in Fe isotope ratio by femtosecond LA‐MC‐ICP‐MS. The reference values (δ 56 Fe IRMM‐014 ) determined by solution nebulisation MC‐ICP‐MS are 0.08 ± 0.03‰, 0.29 ± 0.02‰, 0.20 ± 0.06‰, 0.23 ± 0.03‰ and 0.32 ± 0.01‰ for MtFe‐2 (magnetite), HemFe‐1 (haematite), IlmFe‐1 (ilmenite), VTiMtFe‐1 (V‐Ti magnetite) and VTiMtFe‐2 (V‐Ti magnetite), respectively. Previous magnetite reference material MtFe‐1 can be used as the bracketing calibrator for MtFe‐2 and HemFe‐1. Similarly, there is no matrix effect between MtFe‐2 and HemFe‐1. IlmFe‐1 can be used as the bracketing calibrator for VTiMtFe‐1 and VTiMtFe‐2. VTiMtFe‐1 and VTiMtFe‐2 can be used as the bracketing calibrator for each other. The effects of blank on the determination of Fe isotopes are negligible. The analysis of natural magnetite and ilmenite validates their practical use in geological studies. The prepared reference materials are in sufficient quantities to be shared with other laboratories.

Glacial isostatic adjustment (GIA) profoundly influences postglacial tectonics, sea-level change, and geothermal systems; however, its role during the deglaciation of the Neoproterozoic Snowball Earth remains poorly constrained. Sheet-crack is one of the diagnostic structures in Marinoan (635 Ma) cap carbonates that overlie glacial tillites. Available geochemical evidence indicates that sheet-crack cements precipitated immediately following crack formation, potentially preserving GIA-driven fluid signatures. This study presents fluid inclusion microthermometric data from sheet-crack quartz and barite cements along shelf-to-slope transects on the Yangtze Block, South China. Fluid inclusion homogenization temperatures (Th) reveal the occurrence of a ubiquitous low-temperature hydrothermal event, with most Th values clustering at ∼145 °C–190 °C and ∼120 °C–180 °C in platform facies and slope facies, respectively. Fluid salinities in platform facies exhibit unimodal distributions and low to moderate (∼2–8 wt % NaCl eq.), while those in slope facies show broadly continuous distributions, with most values concentrated at intermediate-to-high salinities (∼6–15 wt % NaCl eq.) and a subordinate low-salinity tail. These patterns are consistent with varying contributions from recirculated, geothermally heated seawater and basinal brines. We propose a refined model in which GIA-related geothermal anomalies promoted a widespread low-temperature hydrothermal circulation event, responsible for sheet-crack cementation shortly after the Marinoan deglaciation, South China.

The radiometric ages of the returned samples are the cornerstone of lunar cratering chronology models. However, all the previous samples were from the lunar nearside and the radiometric ages of those samples that can be associated with particular surfaces are <4.0 billion years. On 25 June 2024, Chang’e-6 successfully returned 1.935-kilogram samples from the lunar farside. The samples included local basalts with an age of 2807 ± 3 million years and the norites with an age of 4247 ± 5 million years likely corresponding to the age of the South Pole–Aitken basin. With these radiometric ages, we refined the lunar chronology function (CF) and verified that it is still consistent with a combination of an exponential decrease and a linear rate. We further derived the impacting rate and found it supports a smooth decay instead of abrupt changes of the impactor flux at early times. The refined lunar CF can be used to obtain more reliable ages for unsampled lunar areas and provide critical constraint for the lunar early impact history.