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Rationale: A novel laser ablation‐isotope ratio mass spectrometry (LA‐IRMS) method for in situ analysis of sulfur isotopes in sulfides has been developed. Instead of the in situ reaction applied by the traditional laser microprobe, the analyte gas preparation in this method is separated temporally and spatially from the LA, resulting in improved precision and accuracy. Methods: Our LA‐IRMS system combines an ultraviolet LA system, an elemental analyzer (EA), a custom‐built cryogenic concentration system, a continuous‐flow interface, and an IRMS. The sulfide aerosol particles generated from LA were transferred by a helium carrier gas from the ablation cell into the reaction tube and were then converted into SO2. Subsequently, SO2 was enriched in two cold traps and was finally introduced into the ion source of the IRMS through the continuous‐flow interface. Results: We measured three synthetic and four natural sulfide reference materials to test the performance of this method. Precisions of ±0.25‰–±0.48‰ and ±0.32‰–±0.64‰ (1SD, n = 5) for δ34S values of synthetic and natural sulfide standards can be obtained for spot sizes ranging from 64 to 80 μm. Measured values and their recommended values showed a good linear relationship (R2 within 0.998 and 0.9995) with the slope of approaching unity (within 1.0509 and 1.1313). Conclusions: Data from the measurement of reference materials showed that the precision and accuracy of our method were satisfactory. This method is a powerful tool for in situ sulfur isotope measurement of sulfides and can be further applied to in situ carbon and oxygen isotope analyses. [ABSTRACT FROM AUTHOR]

The Jiajika rare metal deposit contains the largest area of granitic pegmatite-type rare metal deposits in China. The X03 vein is an immense rare metal deposit dominated by lithium, which was found in the deposit in recent years. The contact metamorphic belt of tourmalinization and petrochemistry is widely developed in its wall rocks, and the altered rocks formed contain Li and other rare metal mineralization. In this paper, the tourmaline found in the different rocks of the Jiajika X03 vein is divided into four types: two-mica quartz schist (Tur-Ⅰ), tourmaline hornfels (Tur-Ⅱ), tourmaline-bearing granite pegmatite (Tur-Ⅲ) and spodumene-bearing granite pegmatite (Tur-Ⅳ); their in situ major element, trace element and boron isotope data are systematically studied. The results show that all tourmalines in the Jiajika X03 vein deposit belong to the alkali group, and are schorl–Oxy/Fluor–schorl, dravite–Hydroxy-dravite and foitite–Oxy foitite solid solutions, among which Tur-Ⅰ are dravite, Tur-Ⅱ are foitite of hydrothermal origin and Tur-Ⅲ and Tur-Ⅳ are schorl of magmatic origin. The boron isotope values show that the boron involved the formation process of tourmaline mainly originates from the Majingzi S-type granite, and the boron isotope variations in tourmaline are controlled by melt fluid and Rayleigh fractionation. Moreover, there is a clear correlation between the B isotope value of tourmaline and the Li, Mn, Zn, Mg, and V contents, showing that these contents in tourmaline are good indicators of the mineralization type of pegmatite. [ABSTRACT FROM AUTHOR]

The Taoshan granite complex located at the North-East part of the Nanling region, hosts the largest granite-related uranuim ore field in China. Baohuashan granite and Huangpi granite are two major components of the Taoshan granite complex. The formation age of Baohuashan granite was in the Indosinian period, which is more closely associated with uranuium ore, however, only individual uranium ore has been found in Baohuashan granite. Huangpi and Daguzhai granites have the same age of (154±2) Ma, but this is in conflict with the field geological phenomena, i.e. Huangpi granite was intruded by Daguzhai granite. High precision techniques of Laser Ablation-Multicollector Inductively Coupled Plasma-Mass Spectrometry (LA-MC-ICPMS) have been used to re-determine the emplacement age of these two plutons and the method is reported in this paper. The results indicate that Baohuashan granite was formed in the Indosinian era (229.98±0.98) Ma, and the Huangpi granite was formed in the early Yanshanian era (160.9±2.4) Ma. The emplacement age of Huangpi granite is a little earlier than Daguzhai granite, which is more aligned with the geological facts. Combining with previous studies, the magma evolutionary sequence, tectonic environment and uranium-production capacity of Taoshan complex are discussed. The magma evolutionary sequence of Taoshan complex was classified into five main stages, which is composed of Baohuashan granite in Indonisian, Huangpi and Daguzhai granites in early Yanshanian, Luobuli and Caishan granite in late Yanshanian. Granite formed at deferent stage belongs to deferent genesis type. The formation of Indonian and Yanshanian granite in Taoshan complex was speculated to related extension tectonic environment caused by subduction of pacific plate. We pointed out that the genesis type of granite is a primary controlling factor for uranium-production capacity of granites. The Daguzhai granit, which is an S-type granite, has the greatest uranium-production capacity. There is a need for further study to determine the underlying reasons for the genesis type controlling uranium-production capacity of granite.

An Early Jurassic (∼196 Ma, laser ablation multiple-collector ICP-MS zircon U-Pb ages) suite of diabase dikes and sills has been identified within the Late Triassic Langjiexue Group, part of the Tethyan sedimentary sequence that is composed of shale and fine-grained sandstone. More primitive rocks (MgO > 8.0 wt%) from this suite are characterized by mid-ocean ridge basalt–like rare earth element distribution patterns and isotope (Sr and Nd) compositions, as well as relatively high contents of mantle-compatible elements (e.g., Cr, Ni, and Co), which indicates that they were derived from partial melting of depleted mantle. Younger (∼140 Ma) mafic magmatism in the region has been proposed to represent the initial breakup of the eastern Gondwana continent and the opening of the Indian Ocean. We propose that the ∼196 Ma diabases developed in a continental extension setting and represent the products of melting of depleted mantle within or on the margin of the Neo-Tethyan Ocean. [ABSTRACT FROM AUTHOR]

Tectonic affinity between the Qaidam‐Qilian Block and the Western Qinling Block is an outstanding issue that has not been fully understood. Detrital zircon U–Pb dating and Hf isotope data for the Precambrian and Permian–Triassic strata around the Gonghe Basin area in both the Western Qinling and Qaidam‐Qilian blocks were studied. Detrital zircons from Precambrian strata range in age from Archean to Late Neoproterozoic, with age peaks at ~2.7–2.5, ~1.8–1.6, and ~0.95–0.75 Ga. Except for Precambrian age groups, Early Palaeozoic (550–500 Ma and ~450 Ma) and Late Palaeozoic–Triassic (~250 Ma) age peaks were also detected in the Triassic strata. The juvenile accreted crustal materials were detected at 1.85–1.5 Ga and over ~2.5 Ga based on zircon Hf isotope studies. Different Precambrian and Triassic strata in both the Western Qinling Block and the Qaidam‐Qilian Block show parallel age distribution patterns and Hf isotopes. A Qaidam‐Qilian source contributed to the majority of detritus in Precambrian strata. Besides sources from the Qaidam‐Qilian Block, Late Permian intrusions around the Gonghe Basin area also provided inputs for the Triassic strata. Detrital zircon studies show a strong connection of the Qaidam‐Qilian Block and the majority of detritus in the Gonghe Basin area of the Western Qinling Block. Tectonomagmatic and provenances comparison of the Western Qinling and Qaidam‐Qilian blocks are supportive of their tectonic continuity at least in three stages, that is, in the Precambrian, Middle Palaeozoic, and Permian to Early Triassic. [ABSTRACT FROM AUTHOR]

The modern Tianshan Mountains and their surrounding basins have mainly been shaped by the far field effects of the Cenozoic India-Asia collision. However, precollision topographic evolution of the Tianshan Mountains and its impacts on the Junggar and Turpan Basins remain unclear due to the scarcity of data. Detrital zircon U-Pb dating of 14 new and 23 published samples from Permian to Neogene strata in the northern Western Tianshan Mountains, northern and southern Bogda Mountains and Central Turpan Basin, are combined with sedimentary characteristics (lithofacies, petrofacies and paleocurrent data) to investigate the temporal and spatial changes in sediment provenances. Based on the age characteristics of the source rocks in the Tianshan Mountains, the detrital zircons are divided into three groups: pre-Carboniferous zircons, mainly from the Central Tianshan Mountains; Carboniferous to Permian zircons, mainly from the North Tianshan and Bogda Mountains; and Mesozoic zircons, mainly from syn-depositional volcanic activity. The topographic evolution of the Tianshan Mountains and their relation to the Junggar and Turpan Basins can be generally divided into six stages. (1) Positive-relief Tianshan and Bogda Mountains and a rifted marine basin formed during the Early Permian to early Middle Permian following late Carboniferous orogenesis, as evidenced by interbedded alluvial fan conglomerates and postcollisional extension-related volcanic rocks along the basin margins, by marine deposits far from the basin margins and by the predominance of Carboniferous to Permian detrital zircons. (2) Fluvial to lacustrine deposits in the modern southern Junggar and Turpan Basins are characterized by abundant pre-Carboniferous zircons and consistently northward-flowing paleocurrents, indicating the submergence of the Bogda Mountains and a contiguous Junggar-Turpan continental depression basin during the late Middle Permian to the Triassic. (3) The Bogda Mountains began to uplift in the Early Jurassic, resulting in opposing paleocurrent directions, a sudden increase in sedimentary lithic detritus and the dominance of Carboniferous to Permian detrital zircons along the southern and northern margins of this range. (4) In contrast to the uplift of the Bogda Mountains, the other parts of the Tianshan Mountains experienced gradual peneplanation from the Early Jurassic to the Middle Jurassic, as confirmed by widespread fluvial to lacustrine deposits, even inside the modern Tianshan Mountains, and by the dominance of pre-Carboniferous detrital zircons. (5) The dominance of Carboniferous to Permian zircons in the southern Junggar Basin suggests the West Tianshan Mountains were uplifted during the Late Jurassic, while the dominance of pre-Carboniferous zircons in the Central Turpan Basin indicates continuous peneplanation in the Eastern Tianshan Mountains. (6) The initial shape of the Tianshan Mountains-Junggar Basin-Turpan Basin system was constructed in the Late Jurassic but was modified in the Cenozoic by the India-Asia collision, resulting in much higher Western Tianshan and Bogda Mountains, low Eastern Tianshan Mountains and well-developed foreland basins. These Cenozoic changes were recorded by the rapid cooling of apatites, the dominance of Carboniferous to Permian zircons in the southern Junggar Basin and northern Turpan Basin, and the dominance of pre-Carboniferous zircons in the Central Turpan Basin. Unlabelled Image • Rifted marine Junggar and Turpan Basins from Early Permian to early Middle Permian • A contiguous Junggar-Turpan continental basin from late Middle Permian to Triassic • Positive Bogda Mountains and isolated Junggar and Turpan Basins from Early Jurassic • Divergence in the topography of the Tianshan Mountains started from Late Jurassic [ABSTRACT FROM AUTHOR]

Iron, Cu and Zn stable isotope systems are applied in constraining a variety of geochemical and environmental processes. Secondary reference materials have been developed by the Institute of Geology, Chinese Academy of Geological Sciences (CAGS), in collaboration with other participating laboratories, comprising three solutions (CAGS‐Fe, CAGS‐Cu and CAGS‐Zn) and one basalt (CAGS‐Basalt). These materials exhibit sufficient homogeneity and stability for application in Fe, Cu and Zn isotopic ratio determinations. Reference values were determined by inter‐laboratory analytical comparisons involving up to eight participating laboratories employing MC‐ICP‐MS techniques, based on the unweighted means of submitted results. Isotopic compositions are reported in per mil notation, based on reference materials IRMM‐014 for Fe, NIST SRM 976 for Cu and IRMM‐3702 for Zn. Respective reference values of CAGS‐Fe, CAGS‐Cu and CAGS‐Zn solutions are as follows: δ56Fe = 0.83 ± 0.07 and δ57Fe = 1.20 ± 0.13, δ65Cu = 0.57 ± 0.06, and δ66Zn = −0.79 ± 0.12 and δ68Zn = −1.65 ± 0.24, respectively. Those of CAGS‐Basalt are δ56Fe = 0.15 ± 0.07, δ57Fe = 0.22 ± 0.10, δ65Cu = 0.12 ± 0.08, δ66Zn = 0.17 ± 0.13, and δ68Zn = 0.34 ± 0.26 (2s). Key Points: Three reference solutions (CAGS‐Fe, CAGS‐Cu and CAGS‐Zn) and one basalt reference material (CAGSR) for calibrating Fe, Cu and Zn isotope ratio measurements have been developed.CAGS‐Fe, CAGS‐Cu, CAGS‐Zn and CAGSR show sufficient homogeneity and stability.Recommended reference values were determined by inter‐laboratory comparison of results from participating laboratories. [ABSTRACT FROM AUTHOR]

The concentrations and isotopic geochemistry of Li are potentially useful geochemical tracers of geological processes. To fully utilize Li isotopes as geochemical tracers, it is necessary to characterize the Li isotopic compositions of the various geological reservoirs. However, the Li isotopic composition of the juvenile lower crust is currently poorly constrained. Given that lithospheric architecture of the Tibetan Plateau includes Indian upper/lower crust, Tibetan upper/lower crust and juvenile lower crust, it is necessary to determine the Li isotopic composition for each geological endmember underneath southern Tibet. Among them, the juvenile lower crust was formed directly by underplating of mantle-derived basaltic magma, which is likely to be the critical factor to control the Cu-Au mineralization in southern Tibet and is responsible for crustal thickening beneath southern Tibet. Here, we report the Li concentration and isotopic composition of the juvenile lower crust in southern Tibet. Based on whole-rock major element, trace element, and Sr–Nd–Pb isotopic data, we infer that the Yeba basalts and Gangdese gabbros were derived from partial melting of metasomatized lithospheric mantle, and have compositions similar to the juvenile lower crust. In contrast, the Dianzhong andesites and Gangdese diorites originated from partial melting of the juvenile lower crust. Therefore, these units may be considered representative of the juvenile lower crust. The juvenile lower crust has Li concentrations of 7.1–37.2 ppm (mean = 15.4 ppm), consistent with the Li concentration for the lower crust (13 ppm). Li isotopic compositions (δ 7 Li) vary from +0.8‰ to +6.6‰ (mean = 3.0‰), similar to values for the EMI/EMII mantle. The Li isotopic compositions of the analyzed samples were not significantly affected by alteration, metamorphism, crustal assimilation, or magmatic differentiation, and therefore represent the isotopic compositions of the juvenile lower crust. The Li systematics of the juvenile lower crust may be attributed to partial melting of subcontinental lithospheric mantle that has undergone metasomatism by Li-rich fluids derived from subducted oceanic crust and marine sediments. Our study also demonstrates near-identical Li isotopic compositions for juvenile lower crust and metasomatized lithospheric mantle, resulting from the lack of Li isotope fractionation during basalt generation and differentiation. [ABSTRACT FROM AUTHOR]