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Research on the mineralogical and geochemical characteristics of altered end-Guadalupian basaltic volcanoclastic rocks can increase the understanding of the alteration history of the overlying stratabound Nb(Ta)-Zr(Hf)-REY-Ga mineralization in the Late Permian coal-bearing sequences. In this paper, based on petrographic observations in addition to XRD, XRF, and ICP-MS analyses, we present and discuss in detail the relationships between primary and secondary minerals and outline the distribution of major and trace element chemistry in the middle/Late Permian basaltic volcaniclastics from the ELIP's zone, western Guizhou, southwest China. The primary clastic suite consists of plagioclase-group minerals, clinopyroxenes, feldspathoids, spinels, and basaltic glasses. Fragments of mafic and, less commonly, felsic and alkaline volcanic rocks are minor components of the studied samples. The alteration products are represented by various chlorite-group minerals (including abundant chamosite), quartz, calcite, albite, analcime, barite, and pyrite, along with relatively minor amounts of titanite, sanidine, magnetite, rutile, and copiapite. The mineralogical and geochemical characteristics of the studied volcaniclastics provide strong evidence correlating them with the high-Ti basalt group, widely distributed within the inner Emeishan large igneous province (ELIP) and coeval rift zone of the middle and outer ELIP. After deposition, the volcaniclastics reacted with complex solutions including heated meteoric waters and were periodically infiltrated by seawater and ascending hydrothermal fluids. As a result, the primary volcanic rocks partly lost alkalis, titanium, silica, and most of the trace elements. These elements, especially the incompatible elements, were probably enriched in the overlying tuffaceous and coal-bearing sequences in the middle and outer ELIP. • Primary and secondary minerals of Emeishan basaltic volcaniclastics were presented. • The volcaniclastics reacted with complex solutions from various sources. • The primary volcanic partly lost alkalis, Ti, Si, and most of the trace elements. • The lost elements were probably enriched in the overlying sediments. [ABSTRACT FROM AUTHOR]

This paper studies the mineralization process and the ore-forming setting of the Kantian fluorite deposit in South China through the zircon U-Pb chronology, quartz Rb-Sr dating, whole rock geochemistry, H-O isotope and fluid inclusions. A mineralization model for the Kantian fluorite deposit is proposed as follows: The subduction of the Pacific plate during the late mid-Jurassic and late Jurassic led to the formation of several fault zones. As the subduction gradually decelerated and eventually ceased, continental extension and lithosphere thinning occurred, accompanied by upwelling of the asthenosphere. This asthenosphere upwelling facilitated melting of the lithospheric mantle, resulting in the ascent of magma into the lower crust. Consequently, the intrusion of magma into the lower crust caused substantial heat, triggering partial melting of the lower crust. The molten material then ascended along faults, generating a significant quantity of granites. During the Early Cretaceous period, the Yanshan cycle witnessed another notable phase of magmatic activity. The residual magmatic hydrothermal fluid from this period served as a source of heating, while the pre-existing fault structures provided favorable pathways and storage space. Atmospheric precipitation infiltrated into the depth along these faults, and the deep-seated residual magmatic hydrothermal fluid heated the infiltrated atmospheric water, inducing cyclic upwelling. The upward migration of hydrothermal fluid continuously extracted Ca and F elements from the granites. Ongoing interaction between the fluid and the surrounding rocks led to changes in pH, coupled with alterations in temperature and pressure, ultimately resulting in the precipitation of fluorite with associated alteration zones in the surrounding rocks. [Display omitted] • Ca and F element in the fluorite were derived through the surrounding rocks. • The ore-forming fluids belong to the NaCl-H 2 O system and exhibit characteristics of medium–low temperature, low salinity, and low density, and were derived from meteoric water. • The intrusion age of surrounding rock in Kantian fluorite deposit was 159.4 ± 2.2 Ma, and the ore-forming of fluorite was 135.6 ± 0.7 Ma. • The tectonic setting responsible for the diagenesis and mineralization processes is believed to be an intracontinental stretching environment associated with the subduction of the Pacific plate. The Yanshanian events have led to the development of South China as a unique granite province globally. Within South Jiangxi, numerous metallic and non-metallic deposits have a close association with Mesozoic granite formations. The Kantian fluorite deposit, a newly discovered non-metallic deposit in southern Jiangxi Province, is one such deposit that is linked to Mesozoic granites. The orebody at the Kantian fluorite deposit is identified as occurring in veined structures within the silicification fracture zone of Mesozoic granites, with strict control exerted by fault systems. Fluorite ore can be classified into two categories based on the amount of quartz and fluorite. The first category is the fluorite quartz type, which has a higher amount of quartz than fluorite. The second category is quartz fluorite type, which has more fluorite than quartz. Among these two categories, the quartz fluorite type is precipitated during the primary mineralization stage. Through the analysis of fluid inclusions within the fluorite, it was determined that the homogenization temperature is relatively low, ranging from 133 to 236℃. The fluid inclusions also display low salinity (0.18–3.39 wt% NaCl eqv.) and low density (0.75–0.96 g/cm3). Laser Raman spectroscopy revealed that the primary components of the fluid inclusions are H 2 O, with minor C 3 H 6. Isotope analysis indicated δD VSMOW values of fluorite ranging from −61.9 ‰ to −54.8 ‰ (average −59.8 ‰), while δ18O VSMOW values varied from 1.3 ‰ to 3.1 ‰ (average 2.0 ‰). This study presents chronological, petrological and geochemical data that suggest several processes. The metallogenic age is 135.6 ± 0.7 Ma. The mineralizing fluids were identified to the NaCl-H 2 O system, with heated meteoric water identified as the primary source; The ore-forming materials originated from the granite, and water–rock interactions are proposed as the primary mechanism for fluorite precipitation. Based on a tectonic setting characterized by stretching, which is closely linked to the subduction of the Pacific plate, we proposed a model for the Kantian fluorite deposit. [ABSTRACT FROM AUTHOR]

The Permian Pingdiquan Formation (P 2 p) in Shishugou Sag, Junggar Basin, Northwest China, is a typical example of mixed sedimentary strata formed in a saline lacustrine environment, characterized by complex lithological assemblages and extensive distribution of organic-rich source rocks. To further investigate the differences in oil-source contribution and hydrocarbon generation characteristics of source rocks with different lithologies, studying the difference of their geochemical characteristics and the formation mechanism of organic-rich source rocks is the top priority. Based on a comprehensive analysis of lithologic types, geochemical characteristics, and hydrocarbon generation potential of source rocks using organic petrology, molecular geochemistry and element geochemistry, this paper reveals the formation background and organic matter enrichment mechanism of the P 2 p organic-rich source rocks. The results show that the mixed sedimentary rocks of the P 2 p were deposited under relatively arid and saline lacustrine conditions. Paleoclimatic conditions tended to be more arid and hydrothermal activity became more frequent during the sedimentation process from mudstone, dolomitic mudstone to argillaceous dolomite. Consequently, the water column salinity elevated, leading to an increased proportion of salt-tolerant green algae and slight salt-tolerant cyanobacteria compared to salt-intolerant algae. Frequent changes in paleoclimate and hydrothermal activity control the interbedding deposition of mudstone, dolomitic mudstone and argillaceous dolomite, and the resulting salinity fluctuations contribute to variations in the proportion of salt-tolerant and intolerant algae in source rocks with different lithologies. Furthermore, the source rocks within the mixed sedimentary strata (mudstone, dolomitic mudstone and argillaceous dolomite) all exhibit substantial hydrocarbon generation potential, and there exists heterogeneity among source rocks of the same lithology. The key factor influencing the development of these organic-rich source rocks is the enhancement of palaeoproductivity driven by volcanic activity. Additionally, the water stratification caused by saline water promotes anoxic water columns, also contributing to organic matter enrichment in the source rocks. • The paleoclimate and hydrothermal activity control the lithology and its composition. • The water column salinity controls the variation of algal composition in source rocks. • Volcanic activity promotes organic-rich source rock by controlling paleoproductivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • The paleoclimatic conditions during deposition control the development of gray sandstone in the red beds. • The uranium mineralization in the red beds exhibits a certain correlation with the inorganic redox reactions involving iron. • Some dark mudstones in the red beds undergo a significant uranium pre-enrichment during deposition. • The climatic alternations lead to a weak reducing capacity in the red beds, with uranium mineralization occurring in the interior of the basin. The search for uranium deposits in the red beds is currently a hotspot in China's sandstone-type uranium exploration efforts. The typical occurrence of uranium deposits is within gray sandstone layers amidst the red beds, where the distribution of these gray sand bodies dictates the presence of uranium deposits. Hence, delving into the genesis of gray sandstone within the red beds proves beneficial for both uranium exploration and unraveling the ore-forming mechanisms. However, there is currently significant controversy surrounding the genesis of gray sandstone in the red beds. This paper focuses on the typical uranium deposit in the red beds—the HLJ-DL uranium deposit in the southwestern part of the Songliao Basin. It investigates the genesis of gray sandstone within uranium-bearing rock series and its relationship with uranium mineralization. The lithology of representative drill cores, including the red sandstone for comparative study, is methodically examined, along with their elemental geochemistry as well as carbon and oxygen isotope characteristics. The petrological characteristics suggest that both the gray and red sandstone share similar compositions of clastic particles, indicating minimal influence of the source rock on the sandstone color. The gray sandstone displays comparable TOC content (averaging around 0.05 %) and δ18O PDB values (averaging around −16 ‰) to the red sandstone. However, it exhibits relatively higher δ13C PDB values (averaging −0.26 ‰), whereas the average δ13C PDB value for the red beds is −1.61 ‰. The data indicate that the gray sandstone is less affected by hydrothermal or hydrocarbon fluids. Compared to the red sandstone, which has relatively higher Cu/Al values (averaging 1.09) and Fe3+/Fe2+ ratios (averaging 3.37), the gray sandstone exhibits low Cu/Al values (averaging 0.44) and a low Fe3+/Fe2+ ratio (averaging 0.36), suggesting its formation in a relatively reducing environment. The reducing conditions necessary for the formation of gray sandstone may stem from the climate becoming relatively warm and humid, irrespective of whether it originates from the original sedimentary environment or is induced by the reducing pore water discharged from dark mudstones. The chemical weathering index of fine-grained sediments indicates that, the gray sandstones were commonly configured in relatively humid-warm climate with fairly low dissolved oxygen content in the bottom water. Additionally, the deposition of the uranium-bearing rock series experienced alternating climatic changes, rather than consistently being in a humid-warm climate. This resulted in the sand bodies with low TOC content, insufficient reducing potential, and uranium mineralization primarily occurring in the interior of the basin. Organic matter has a relatively weak control over uranium mineralization, whereas uranium mineralization shows a certain correlation with iron reduction. The ore-forming fluid was uranium-rich oxygenated atmospheric water. Dark-colored mudstones, formed under humid-warm climatic condition, contain relatively high TOC contents (avg. 0.43 %) and exhibit a strong reducing capacity. The reducing pore water in dark-colored mudstones excreted into the adjacent sandstones under compaction during the early diagenesis, is able to serve as a vital reducing agent in later-stage uranium mineralization. Additionally, certain dark-colored mudstones with high uranium content (up to 944 ppm) undergo significant uranium pre-enrichment, providing a partial uranium source for uranium mineralization. [ABSTRACT FROM AUTHOR]

[Display omitted] • The genesis of Jurassic igneous rocks in the Yanbian area was related to the subduction of the Paleo-Pacific Plate. • The Paleo-Pacific Plate started subduction beneath the Eurasian continent at the Early Jurassic. • Slab tear occurred at the Late Jurassic and this was followed by oblique subduction of the Paleo-Pacific Plate. It is widely accepted that the subduction of the Paleo-Pacific Plate beneath the Eurasian continent began during the early Mesozoic; however, the details of the subduction process remain uncertain. This paper presents new zircon U–Pb–Hf and whole-rock geochemical data for Jurassic intrusive rocks from the Yanbian area of NE China to provide a better understanding of the subduction history of the Paleo-Pacific Plate. Zircon U–Pb dating results reveal that three stages of Jurassic magmatism are recorded in the Yanbian area, namely, Early Jurassic (188–179 Ma), Middle Jurassic (172–163 Ma), and Late Jurassic (158–156 Ma). Early Jurassic intrusive rocks from the Yanbian area are predominantly calc-alkaline gabbro, gabbro-diorite, quartz monzonite, granodiorite, and syenogranite. These geochemical features and rock associations are indicative of formation in an active continental margin setting related to the initial subduction of the Paleo-Pacific Plate beneath the Eurasian continent. The Early Jurassic granitoids were formed mainly by the partial melting of heterogeneous lower crust. The Middle Jurassic granitoids are geochemically similar to adakites and have ε Hf (t) values of + 2.0 to + 10.1. These rocks are inferred to have been derived from magmas generated by the partial melting of thickened juvenile lower-crustal material. Their formation was related to the subduction of the Paleo-Pacific Plate. Late Jurassic adakites in the Yanbian area formed in a compressional tectonic setting. Their negative ε Hf (t) values (−17.2 to − 8.6) and T DM2 ages (2025–1552 Ma) indicate that the primary magma was derived from the partial melting of ancient continental crust. Combining our data with the distribution of Late Jurassic igneous rocks in the NE Asian continental margin and the northward migration of Jurassic accretionary complexes along the margin, we conclude that the subduction of the Paleo-Pacific Plate beneath the Eurasian continent during the Late Jurassic–earliest Early Cretaceous had a low angle of obliquity. [ABSTRACT FROM AUTHOR]

[Display omitted] • Middle Permian adakite, arc granitoids and high fractionated granite in the northern Qaidam Block have been identified. • Various magma sources contributed to the occurrence of these granitoids in the northern Qaidam Block. • The northern Qaidam Block was an active continental arc during the Middle Permian. • A five-stage model of subduction slab roll-back and subduction zone retreat for late Late Paleozoic to Early Mesozoic tectonic evolution of the northern Qaidam Block. Origin and tectonic setting of late Late Paleozoic to Early Mesozoic igneous rocks in the northern Qaidam Block (NQ) have long been a matter of debate. In this paper, we report new zircon U-Pb ages and Hf isotopic compositions and bulk rock major and trace elemental compositions for granitoids of the Yanchangbeishan area in the NQ. The granodiorite, tonalite, granodiorite, and syenogranite yielded zircon U-Pb ages of 271.9 Ma, 262.0 Ma, 272.4 Ma and 261.3 Ma, respectively, corresponding to ε Hf (t) values are 13.04–14.32, 8.14–10.77, 8.66–11.88, and 8.22–10.43, respectively. These granitoids are compositionally I-type granites and exhibit varying degrees of enrichment in Rb, Th, U, and K, and depletion in Nb, Ta, and Ti. According to field relationships, petrology, geochronology, and geochemistry, the granitoid types can be divided into three groups: (1) ca. 272 Ma granodiorites, which are formed through partial melting of metagreywackes and amphibolites derived from depleted mantle; (2) ca. 262 Ma tonalite, which represents a typical high-silica adakite derived from partial melting of subducted oceanic crust during the evolution of depleted mantle; and (3) ca. 261 Ma syenogranite, which is formed by the partial melting and high-degree fractional crystallization of mixed crustal materials. Considering our findings and the regional geological background, we propose a five-stage tectonic evolution model of subduction slab roll-back and subduction zone retreat for the late Late Paleozoic to Early Mesozoic of NQ. [ABSTRACT FROM AUTHOR]

Abstract: Geochemical data used in this paper to identify geochemical signatures associated with Fe mineralization in eastern Tianshan mineral district, China are compositional data. In order to eliminate the spurious relationships between compositions, isometric logratio (ilr) transformation is currently employed to deal with the closure effects. The opened geochemical data are further analyzed by principal component analysis. By back-transforming to the clr space, PCA results of ilr transformed data with geological meanings of their counterparts assist in recognition of spatial distributions of both intermediate-felsic igneous rocks and fault systems in the study area. In comparison with log-transformed geochemical data, the ilr transformed ones are theoretically reasonable to apply standard statistics. In addition, multivariate outliers are identified to investigate their associations with the formation of these two geological features. At the end, this paper suggests that the ilr transformation is necessary to be applied routinely before applying statistical treatments to raw geochemical data. [Copyright &y& Elsevier]

This paper presents new zircon U Pb ages and Hf isotope data, and whole-rock geochemical and Sr Nd isotopic data, for lamprophyres in the western Shandong area of China. These data provide new insights into the nature of the lithospheric mantle beneath the eastern North China Craton (NCC) during the Early Cretaceous. The lamprophyres are divided into low-Ti (TiO 2 < 1.1 wt%; Ti/Y < 270) and high-Ti (TiO 2 > 2 wt%; Ti/Y > 370) suites, where the Xiaya and Jingziyu minettes are defined as low-Ti lamprophyres and the Jingziyu pyroxene lamprophyres are defined as high-Ti lamprophyres. The igneous zircons yield weighted-mean ages of 126, 132, and 130 Ma for the low- and high-Ti lamprophyres, respectively, indicating these units formed during the Early Cretaceous. The inherited zircons within the Xiaya and Jingziyu minettes define six (2517, 1852, 725, 375, 276, and 236 Ma) and two (2523 and 462 Ma) main age populations, respectively. In comparison, the inherited zircons from the Jingziyu pyroxene lamprophyres yield two main age populations (2523 and 1848 Ma). The low-Ti lamprophyres are enriched in the light rare earth elements (LREE) and large-ion lithophile elements (LILE), depleted in the heavy REE (HREE) and high-field-strength elements (HFSE), and have small negative Eu anomalies. In comparison, the high-Ti lamprophyres are enriched in the LREE but are slightly depleted in the HFSE. The low-Ti lamprophyres also have high 87Sr/86Sr(t) ratios (0.7121–0.7123), low ε Nd (t) values (−18.81 to −18.62), and contain igneous zircons with relatively high ε Hf (t) values (generally between −9.94 and −3.36). In comparison, the high-Ti lamprophyres have 87Sr/86Sr(t) ratios of 0.7066–0.7068, ε Nd (t) values from −5.01 to −4.64, and contain igneous zircons with ε Hf (t) values from −11.77 to −8.50. These data indicate the low-Ti lamprophyres formed from primary magmas generated by the partial melting of an enriched region of the lithospheric mantle that was previously strongly modified jointly by subduction breakoff of the downgoing Yangtze Craton basement material and delamination of the lower continental crust within the NCC. In comparison, the magmas that formed the high-Ti lamprophyres were generated by the partial melting of an enriched region of the lithospheric mantle that was weakly modified by interaction with the lower continental crust of the NCC. Both the low- and high-Ti lamprophyres formed in an extensional tectonic environment during lithospheric thinning, and the presence of these two suites of lamprophyres indicates that lithospheric thinning of the eastern NCC peaked during the Early Cretaceous. • Low- and high-Ti lamprophyres in the western Shandong area formed during the Early Cretaceous. • These lamprophyres indicate that peak lithospheric thinning of the eastern NCC occurred during the Early Cretaceous. • Delamination was an important process during the destruction of the NCC. [ABSTRACT FROM AUTHOR]

Highlights • There are sanukitoids and anatectic granites in the Bundelkhand Craton. • U-Pb zircon dating of a sanukitoid yielded a crystallization age of 2577 ± 16 Ma. • Sanukitoids are derived from a crustal source. • Sanukitoids and anatectic granites formed in a subduction-collision environment. Abstract In this paper, we present in situ zircon U–Pb ages as well as whole-rock elemental and Sm-Nd isotopic compositions for late Archean sanukitoids of the Bundelkhand Craton, India. The LA–ICP–MS zircon U–Pb dating results of the sanukitoids (s.l.) indicate that these rocks were emplaced at 2577 ± 16 Ma, with inherited zircon at an age of 2644 ± 25 Ma, and are coeval with high-K anatectic granites (2544–2583 Ma). The sanukitoids (s.l.) are characterized by high-alumina (15–16 wt.%), Mg# (27–50) and TiO 2 (0.31–0.87 wt.%). They have a strongly enriched signature in terms of incompatible trace elements (LREEs and LILE) pointing to a subduction-related or crustal source. The high-K anatectic granites are characterized by Al 2 O 3 (12–15 wt.%), Mg# (13–39) and TiO 2 (0.06–0.8 wt.%); they have enriched and variable concentrations of LILEs and REEs; and negative Eu anomalies (Eu/Eu* = 0.15–0.93). The whole-rock ε Nd (t) values (−3.64 to −1.66) indicate a crustal component. These isotopic and geochemical characteristics indicate that the sanukitoid plutons originated from the mixing of metasomatized mantle melts with anatectic melts and were followed by homogenization at shallow levels of emplacement, whereas the high-K anatectic granites indicate reworking of the pre-existing TTG crust during the cratonic stabilization ca. 2.5 Ga. This interpretation suggests a temporal evolution from TTG-domination through sanukitoids (s.l.) to anatectic leucogranites by an internal reworking of the continental crust, involving subduction-collision environments in the late Archean era. Such magmatic events and tectonics during the late-Archean in the Bundelkhand Craton resemble other Archean cratons, such as the Dharwar, North China, Karelian, Superior Province, Pilbara, Kaapvaal and Amazonian. [ABSTRACT FROM AUTHOR]

• The Jinchang gold-rich porphyry deposit has experienced two mineralization phases. • It includes early Au–Cu (∼114 Ma) and late Au-only mineralization (103–101 Ma). • Jinchang deposit was formed by the subduction roll-back of the Paleo-Pacific Plate. Whether multiple mineralization styles in porphyry deposits are the result of one or multiple pulses of magmatism is unknown. In this paper, we present new age and geochemical data on the Jinchang porphyry gold-copper (Au-Cu) deposit, an important deposit in NE China and in the eastern Central Asian Orogenic Belt (CAOB). Field geological study suggests that both the mineralization and ore-causative magmatism at Jinchang are multiphase. LA-ICP-MS zircon U-Pb dating of the monzogranite ore host yielded 197 ± 1 Ma, which is considerably older than the ore-causative monzonite (115 ± 3 Ma) and granodiorite (107 ± 2 Ma). Molybdenite Re–Os dating on the breccia pipe-hosted Au-Cu ores yielded a well-defined isochron age of 114 ± 3 Ma, coeval to the monzonite emplacement. The Au-Cu mineralization was followed by another phase of crypto-explosive breccia pipe-hosted, disseminated/vein-type Au mineralization. This Au-only mineralization phase was auriferous pyrite Re–Os dated to be 103–101 Ma, coeval to the granodiorite emplacement. Geochemically, the monzonite and granodiorite are enriched in LILEs and LREEs, but depleted in HFSEs and HREEs. The ore-causative rocks are I-type and display continental arc geochemical affinities. We suggest that the monzonite and granodiorite were generated in an intracontinental extensional setting, probably caused by the Early Cretaceous subduction roll-back of the Paleo-Pacific Plate. [ABSTRACT FROM AUTHOR]

Abstract This paper uses coal-measure shales from Carboniferous-Permian in Yushe-Wuxiang Block as an example to study the physical properties of transitional coal measure shales, including geochemical properties (e.g. total organic carbon content (TOC), organic matter maturity and hydrocarbon generation potential); mineral composition determined by X-ray diffraction (XRD) and pore structure characteristics determined by gas adsorption methods. The results indicated that the transitional coal measure shales in Yushe-Wuxiang area mostly comprise type III kerogen and are mostly in the over-mature stage, with shales in the range of 1.86%–3.36% R o. The TOC of transitional shales varied significantly, ranging from 0.10% to 34.37%. Clay minerals and quartz are major minerals in transitional shales, while the predominant clay minerals are illite-smectite mixed clay (I/S) and kaolinite. The total pore volume (TPV) and pore specific surface area (SSA) of investigated mud shales varies from 0.0071 to 0.023 cm3/g and 8.4059–18.2888 m2/g, respectively. The transitional shales mostly provide mesopores and macropores, whereas the micropores provide the main SSA. The TOC content has a distinct effect on the porosity and micropores volume but contributes little to the TPV and volumes of macropores and mesopores. Clay minerals are positively correlated with porosity, TPV and volumes of each class of pores, while quartz has an opposite effect. In the over-maturity stage, the increase of organic matter maturity will inhibit the development level of pores in shale. For the coal measure shales, I/S and illite contribute most to the pore development. Highlights • TOC is positively correlated with porosity and micropore volume. • Clay minerals are positively correlated with pore volumes. • Quartz inhibits the development level of transitional coal measure shales. • The development and evolution of pores was mainly attributed to the presence of I/S and illite. [ABSTRACT FROM AUTHOR]

Abstract: Principal component analysis (PCA) is frequently used in geosciences for information extraction. In many applications, masking PCA has been used to create subsets of samples or sub-areas to enhance the effect of the main objects of interest. In this paper we suggest how the representativeness of samples or pixels can be quantified using a fuzzy membership function based on fuzzy set theory. In this new method, the relative importance of pixels or samples can be taken into account using a multivariate statistical method such as PCA. A Fuzzy Masking PCA is proposed and implemented in GeoDAS GIS on the basis of a spatially weighted PCA (SWPCA). This paper introduces the mathematical treatment of the fuzzy masking PCA and follows a case study of identifying the locations of intrusive bodies from geochemical data in the Gejiu mineral district in Yunnan, China. Power-law functions based on the inverse distance from mapped felsic intrusions are applied as weighting functions in FMPCA. The results indicate that fuzzy mask PCA increases the signal-noise ratio of the component representing igneous intrusions and decreases the influence of sedimentary rocks. The areas delineated as potential areas for new intrusions (including buried intrusions) are valuable guides for Sn mineral prospecting. [Copyright &y& Elsevier]

This introduction outlines the papers collected in the special issue "Evolution and metallogeny of the Sanjiang arc-back arc basin system in the Eastern Tethys." The papers focus on scientific issues from Paleozoic to Cenozoic evolution and metallogeny of the Sanjiang arc-back arc basin system in the Eastern Tethys concerning tectonics, petrology, geochemistry, geochronology and mineral deposits. An evolution and metallogeny of the Sanjiang arc-back arc basin system in the Eastern Tethys is briefly introduced. [ABSTRACT FROM AUTHOR]

In this paper, we present zircon U Pb dating, elemental geochemistry, and Sr–Nd–Hf isotopic compositions for Late Carboniferous intrusive rocks in the northern Great Xing'an Range, northeast China. We decipher the mechanisms which triggered lithospheric thinning under microblock-microblock collision and provide a new perspective on the Late Paleozoic evolution of the eastern Central Asian Orogenic Belt. Zircon U Pb dating indicates that Jifeng gabbroic diorites and Xinlin granites were formed during a short time interval at 322–321 Ma, whereas the Xinlin gabbros were crystallized at 300 ± 2 Ma. The Jifeng gabbroic diorites exhibit typical arc characteristics, depleted in HFSEs and enriched in Pb and have positive ε Nd (t) (+1.88 to +2.00) and ε Hf (t) (+6.6 to +10.7) values, suggesting they originated from the partial melting of depleted lithospheric mantle modified by slab fluids. The Xinlin gabbros belong to alkaline series and are characterized by the enrichment in HFSEs with positive Nb and Ta anomalies and depleted Nd Hf isotopic compositions (zircon ε Hf (t) = +12.5 to +18.9, whole rock ε Nd (t) = +8.0 to +8.1). High Nb concentrations and low La/Nb (0.81–0.83) and La/Ta (12.50–14.61) ratios of the Xinlin gabbros indicate an origin from a depleted asthenospheric mantle. The Xinlin granites have high-K calc-alkaline compositions, belonging to I-type granites. These granites have positive ε Hf (t) values (+0.2 to +15.1) and juvenile two-stage model ages (1314–506 Ma) with low Sr and high Yb contents, indicating they were formed by the partial melting of a juvenile lower crust under low-pressure conditions. These data, together with the temporal and spatial distribution and the geochemistry characteristics of the Carboniferous igneous rocks in the Great Xing'an Range, suggest that the amalgamation between the Erguna–Xing'an and Songnen blocks occurred before the Late Carboniferous. The occurrence of asthenospheric mantle-derived mafic rocks indicates localized thinning process of lithosphere. Late Carboniferous magmatism on the Erguna–Xing'an Block attributed to dripping or piece removal of the lithosphere due to asthenospheric fluctuation triggered by slab break-off. • Lithospheric and asthenospheric sources of mafic rocks represent the different stage of post-collisional magmatism. • The amalgamation of the Xing'an and Songnen blocks occurred before late Early Carboniferous. • Lithospheric dripping triggered by slab break-off generated the planar Late Carboniferous post-collisional magmatism. [ABSTRACT FROM AUTHOR]

There have been recent breakthroughs in exploration for tin (Sn) and silver (Ag) mineral resources in the Southern Great Xing'an Range, making this region a world-class Sn and Ag metallogenic area. However, thick surface coverage and hidden deposits make exploration difficult, and conventional geological and geochemical prospecting methods have severely limited efficacy. In order to further extract geological and geochemical information on the basis of the existing research, to serve the regional mineral exploration, the knowledge-driven CoDA method is used to identify geochemical associations for inferring matallogenic information. Meanwhile, the fractal C-A model is used to determine geochemical anomalies, the catchment basin geochemical method is used to delineate anomaly boundary. Especially, the data-driven CoDA method is employed for comparison analysis with the knowledge-driven one. As a result, seven groups of compositional balances are proposed and verified, and geological bodies closely related to Sn and Ag mineralization are identified. These occurred in Dashizhai Formation strata, being calcareous rocks and granites, especially A-type granite, which is most closely related to mineralization. Meanwhile, Sn and Ag mineralization areas were identified and found to be consistent with known deposits. Finally, this paper proposes a novel model of regional porphyry Sn–Cu metallogenic systems and delineates exploration targets for Ag–Zn–Pb–Cu deposits and Sn–polymetallic deposits based on the analysis of catchment basins. • Meaningful geochemical associations are gained from knowledge- driven CoDA. • Using geochemical associations to infer ore-bearing strata, granite, calcareous rocks and mineralization • Catchment basin division for geochemistry is useful for regional metallogenic prediction. • Regional metallogenic model is proposed. [ABSTRACT FROM AUTHOR]

The Permian-Triassic transitional interval exposed well at Kangjiaping section, northwestern Hunan, South China, contains microbialites, oolitic and oncolitic limestones intercalated with vermiculate micritic limestones in the Lower Triassic overlying the uppermost Permian bioclastic limestones, which provides an excellent opportunity to study the environmental changes after the end-Permian mass extinction (EPME) and the origins and environmental significance of these various anomalous sediments. In this paper, we describe in detail the petrographic and geochemical characteristics of these anomalous sediments, together with the reconstruction of the marine environment after the EPME. The continental margin weathering was significantly enhanced after the EPME, indicated by the higher concentrations of terrigenous minerals, Th, Sc, Sr, and rare earth elements in the Lower Triassic carbonates than in the uppermost Permian bioclastic limestones. Indicators such as V/(V + Ni) and Ni/Co ratios suggest that the oxygen content of shallow seawater significantly decreased after the EPME. While, most samples from the Kangjiaping section preserve a negative cerium anomaly, indicating the shallow seawater was still oxygenated both before and after the EPME. In addition, the abnormally rapid carbonate precipitation rate indicates a supersaturation state with respect to calcium carbonate in the shallow seawater after the EPME, but the depth and salinity of seawater and climate indicated by different microfacies are still different. Under the setting of a rapid transgression after the EPME, the microbialites first deposited on the platform with the exclusion of grazers at the beginning of the Early Triassic, followed by the oncolites formed when the climate turned humid with a relative sea-level rise. The oolites were primarily deposited in an arid climate with a relative sea-level fall, and the salinity and hydrodynamics of seawater controlled the ooids' grain sizes. In contrast, the (vermiculate) micritic limestones were mainly formed in a humid climate with a relative sea-level rising and more terrigenous inputs. Therefore, the periodic relative sea-level fluctuation and arid-humid climate alternations play a vital role in the evolution and repeat stacking of various microfacies in the Kangjiaping section. • First integrated study of the PTB interval at Kangjiaping section that focuses on petrography and geochemistry and their implication for environmental change. • Marine environment following the end-Permian mass extinction was assessed. • Depositional environment of various anomalous sediments and the controlling factors for their evolution were clarified. • The sedimentary process and depositional model of the Permian-Triassic boundary interval at the Kangjiaping section were re-established. [ABSTRACT FROM AUTHOR]

This introduction outlines the papers collected in the special issue "Mesozoic magmatism and mineralization in Southeastern China". These papers focus on the spatiotemporal distributions, petrogenesis, geochronology, mineralization and tectonic settings of the Mesozoic granitic rocks in SE China, and they represent the new research progress and further understanding on the granitic magmatism and associated mineralization. After the overview of the all papers, we propose the insights for future studies on the granitoids and associated mineralization in SE China. [ABSTRACT FROM AUTHOR]

The Huanren skarn Cu–Zn deposit is located in southeastern Liaoning on the eastern edge of the North China Craton (NCC). In this paper, we present a study on the geochronologic, geochemical and Sr–Nd–Hf and S isotopic data for the magmatic rocks and sulfide minerals exposed in the deposit. Laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) dating of zircon grains from two mining pits in the monzodiorite yields ages of 128.2 ± 1.1 Ma and 128.6 ± 1.5 Ma; these results indicate that the magmatism in the Huanren Cu–Zn deposit might have occurred in the Early Cretaceous. Geochemically, the Huanren monzodiorite belongs to the high-K calc-alkaline and shoshonitic series, is enriched in Rb, Ba, and K and is depleted in Nb, Ta, and Ti. The rocks also have relatively high ( 87 Sr/ 86 Sr) i (0.7091–0.7099) and low εNd(t) (−13.2 to − 10.3) and εHf(t) values (−14.3 to − 7.8). The Sr–Nd–Hf isotopic data for the monzodiorite indicate that the magma may be derived from mixed sources of the crust and mantle. The δ 34 S values of chalcopyrite, galena and pyrite range from 4.4‰ to 5.8‰, with an average of 5.1‰, indicating that the sulfur in the deposit was mainly derived from a magmatic source. The Huanren Cu–Zn deposit resulted from the magmatism and mineralization induced by the rollback of the Paleo-Pacific Plate. [ABSTRACT FROM AUTHOR]

Organic-rich shale deposited in a marine-continental transitional facies was well developed in the upper Yangtze area during the Late Permian. It is considered to contain a large amount of shale hydrocarbon resources. This paper takes the Upper Permian Longtan shale in the central Guizhou uplift as an example to characterize the transitional shale reservoir. Based on organic geochemistry data, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM) observation, the geochemical characteristics of this transitional shale were systematically studied and the shale gas potential was investigated. The results indicate that the Longtan shale has fair to good hydrocarbon potential with high total organic carbon (TOC) and contains type III gas-prone organic matter. Its high thermal maturity favors the generation of gas (Ro, 1.10%–2.74%). XRD analyses show that the mineral components of the transitional shale are dominated by high clay content (58.7 wt%). The clay minerals are dominated by illite (44%) and mixed illite/smectite (43%). SEM observation shows that intra-particle pores, inter-particle pores and microfracture were well developed in the Longtan shale, which can provide reservoir space for the accumulation of shale gas. Organic matter pores appear rare due to its organic type. In summary, the Longtan shale has high organic content, high maturation, and high gas content, all of which demonstrate its great potential as a shale-gas resource. But the high clay content of the Longtan shale may be a challenge to shale-gas production. [ABSTRACT FROM AUTHOR]

Due to the strong variations in the distribution of the sedimentary strata, the degree of denudation of carbonate strata is not consistent across the different regions. In the Huanglong ore field, the carbonate strata hosting the Longqiao ore body is relatively stable, and its protolith comprises dolomitic limestone and dolomitic marlstone, whereas the lithology of that hosting the Mabianshan ore body shift from Fe-Mn bearing dolomite and dolomite to dolomitic limestone and marlstone in the extension direction of the ore body. The content of Al, Si, Mg, Mn and Ca in the carbonate strata in Mabianshan varies more greatly in this direction. [Display omitted] • The Mabianshan and Longqiao deposits in Luzong volcanic basin had different heat sources. • The protolith of Mabianshan magnetite ore body varies greatly in the content of Al, Si, Mg, Mn, and Ca. • The complex protolith lithology of magnetite results in tracing fluid source using Si, Al, Mg, and Mn hard to effectively. The composition of host rocks is essential in determining the composition of hydrothermal magnetite formed via fluid-rock interactions in skarn deposits. The HuangLong ore field in the Luzong volcanic basin, Eastern China, hosts several stratabound iron (Fe) skarn deposits, including Mabianshan and Longqiao. In this paper, we analyse the composition of different lithologies of carbonate strata and trace element concentrations in magnetite from Mabianshan, which has complex lithology carbonate strata, and compare it with magnetite from Longqiao, which has uniform lithology carbonate strata. The objective is to investigate the influence of lithology variation on magnetite trace elements and enhance the indicative significance of magnetite trace elements in prospecting and exploration. Our results demonstrate that the lithology of ore-bearing carbonate strata varies greatly due to inversion and different degrees of denudation in the ore field, resulting in variations of Al, Si, Mg, Mn, and Ca in the protolith across different areas. The alteration mineral assemblage of the Mabianshan deposit primarily included epidote, chlorite, and magnetite, while only a few diopside-magnetite relatively high-temperature assemblages developed in the southeastern part of the deposit. Moreover, higher concentrations of Ti and V in magnetite samples from the southeastern area of the deposit suggest that the heat sources related to Fe mineralization may be located there. Compared with the regular spatial variations of Mg, Mn, Al, and Si in the magnetite from Longqiao, the magnetite from Mabianshan does not show evident spatial variations due to the complex lithology of the magnetite protolith in different regions. The protolith lithology of magnetite from Longqiao is relatively stable, mainly dolomitic limestone. However, the protolith lithology of magnetite from Mabianshan is complex and includes dolomitic marlstone, dolomitic limestone, dolomite, and Fe-Mn bearing dolomite, resulting in a significant increase of Si, Al, Mg, and Mn in magnetite. Therefore, it is difficult to effectively trace the temporal-spatial evolution of the hydrothermal fluids using these elements in magnetite. Special attention should be paid to the uniformity of the protolith lithology of the ore when using these elements in magnetite to trace the fluid source. [ABSTRACT FROM AUTHOR]

The Late Paleozoic sedimentary environment in the southern Great Xing'an Range in Northeast (NE) China, and the timing of the final closure of the Paleo Asian Ocean between the North China Craton and combined NE China blocks have been controversial for a long time, affecting and restricting the exploration and development of new area and new strata in the North Area in China. In order to reconstruct the structural-sedimentary evolution history of the southern Great Xing'an Range during the Middle to Late Permian, and to explore the closure time of the Paleo Asian Ocean (Eastern Segment), in this paper, the sedimentary characteristics and tectonic background of the Middle–Late Permian sedimentary rocks from well MKD1 are systematically analyzed by using elemental and organic geochemistry methods. The results show that the Middle Permian sedimentary records in well MKD1 show typical marine sediments, while the Late Permian sediments change significantly to clastic rocks deposited in the marine–continental transitional environment. The provenances of the Middle Permian rocks are mainly intermediate and felsic igneous rocks from continental active margin and oceanic island arc tectonic setting, related to the northern accretion complex, and the Songnen Block and partially arc magmatic rock. The source materials of the Late Permian rocks are mainly felsic rocks and some intermediate igneous rocks from the continental arc and active margin, related to the northern accretion complex, the arc magmatic rock and the Songnen Block. Depositional discontinuity after the Late Permian, regional lackness of the Early Triassic strata, sedimentary environment variation, tectonic setting and provenance location discrimination of the Middle–Late Permian rocks comprehensively reveal that the Paleo Asian Ocean (Eastern Segment) possibly closed in the late Late Permian. Finally, we propose a structural-sedimentary evolution pattern of the southern Great Xing'an Range during the Middle to Late Permian. • The elemental and organic geochemistry method was synthetically applied. • The provenance of an oceanic island arc is discovered in the sedimentary rocks. • The closure time of the Paleo Asian Ocean is determined as late Late Permian. • The structural-sedimentary evolution model in the Middle–Late Permian is proposed. [ABSTRACT FROM AUTHOR]

Integrating multi-source geoscience information (such as geology, geophysics, geochemistry, and remote sensing) using GIS mapping is one of the key topics and frontiers in quantitative geosciences for mineral exploration. GIS prospective mapping and three-dimensional (3D) modeling can be used not only to extract exploration criteria and delineate metallogenetic targets but also to provide important information for the quantitative assessment of mineral resources. This paper uses the Shangnan district of Shaanxi province (China) as a case study area. GIS mapping and potential granite-hydrothermal uranium targeting were conducted in the study area combining weights of evidence (WofE) and concentration-area (C-A) fractal methods with multi-source geoscience information. 3D deposit-scale modeling using GOCAD software was performed to validate the shapes and features of the potential targets at the subsurface. The research results show that: (1) the known deposits have potential zones at depth, and the 3D geological models can delineate surface or subsurface ore-forming features, which can be used to analyze the uncertainty of the shape and feature of prospectivity mapping at the subsurface; (2) single geochemistry anomalies or remote sensing anomalies at the surface require combining the depth exploration criteria of geophysics to identify potential targets; and (3) the single or sparse exploration criteria zone with few mineralization spots at the surface has high uncertainty in terms of the exploration target. [ABSTRACT FROM AUTHOR]

This paper investigates the mineralogy and geochemistry of four coal beds (WJB-6, WJB-7, FHS-23 and FHS-27 Coals) of the Late Permian in the Zhina Coalfield, western Guizhou Province, China. The investigated coals reach the semianthracite -anthracite coal rank and have super-low to low ash yields. The sulfur contents vary considerably through coal sections and are mostly in the range of medium-high sulfur coal. The mineral assemblage present in the FHS-23 and FHS-27 Coals is mainly made up of pyrite and rectorite; the WJB-6 and WJB-7 Coals have different mineralogy, with kaolinite and rectorite dominant in the former as well as quartz and rectorite in the latter. These coals contain high concentrations of Nb and Ta, but Li is only enriched in the WJB-6 Coal. Rectorite and anatase in these coals are important hosting phases of Nb and Ta while kaolinite, and to a lesser extent chamosite in the WJB-6 Coal, are dominant carriers for the elevated Li concentration. The terrigenous material input, the marine influence and the effect of circulating hydrothermal solution are the pivotal geological factors causing geochemical anomalies in coals investigated. The high-sulfur coals were subjected to an enhanced marine influence in the depositional environment, as well as to a higher terrigenous influx, when compared with the medium-sulfur and low-sulfur coals, resulting in higher concentrations of S-Fe-As-Mo-U-Hg in the former coals than in the latter ones. The anomalous enrichment of Nb and Ta in these coals, as well as of Li in the WJB-6 Coal, is the result of the contributions from ascending hydrothermal solutions, although source rocks (e.g., high-Ti basalt) may provide relatively high background abundances of Nb, Ta and Li. [ABSTRACT FROM AUTHOR]

Rare metals in coal deposits have attracted much attention in recent years because of their potential economic significance. This paper reports the abundance and enrichment origin of rare metals in the Late Permian coals (K1 and K2 Coals) of the Moxinpo Coalfield, Chongqing, southwestern China. The K1 Coal is characterized by highly-elevated concentrations of U-Re-V-Cr-Se and Nb(Ta)-Zr(Hf)-REE assemblages; the latter assemblage is also enriched in the K2 Coal. The high temperature ash (815 °C) of the K1 Coal is enriched in V, Cr, Se, Re, U and REE; the ash of the K2 Coal, and also the floor strata of each seam, are enriched in REE, potentially making all of the units economically viable sources for these elements. The minerals in the K1 Coal are mainly represented by kaolinite, illite and mixed-layer illite/smectite, and pyrite, while the minerals in the K2 Coal consist mainly of kaolinite and tobelite [(NH 4 ,K)Al 2 (AlSi 3 O 10 )(OH) 2 ]. Authigenic roscoelite [K(V 3 + ,Al) 2 (AlSi 3 O 10 )(OH) 2 ] is commonly observed in the K1 Coal under the SEM, and was probably formed by interaction of kaolinite with V derived from permeating U-Re-V-Cr-Se-rich solutions during early diagenesis. The tobelite enriched in the K2 Coal was formed by reaction between kaolinite already present in the coal and NH 4 + derived from decomposition of the organic matter during hydrothermal alteration at a relatively high temperature. The mafic tuffs directly underlying the K1 Coal and containing limestone residual breccias not only served as the substrate for coal accumulation but also as the source of sediment from the uplifted areas around the coal basin. The latter is indicated by low Al 2 O 3 /TiO 2 ratios (from 10.09 to 14.24), positive Eu anomalies enrichment of medium rare earths (relative to upper continental crust), and detrital calcite of terrigenous origin. The highly-elevated concentrations of U-Re-V-Cr-Se assemblages in the coal were derived from exfiltrational hydrothermal solutions and were then deposited in a euxinic environment. The terrigenous materials in the K2 Coal, however, were derived from felsic-intermediate rocks at the top of the Kangdian Upland, although the elevated concentrations of Nb(Ta)-Zr(Hf)-REE assemblages are attributed to the input of hydrothermal solutions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Gold and As contents in pyrite from Carlin-type Au deposits may be coupled or decoupled. • High As contents in pyrite favor Au incorporation, but are not solely responsible for Au enrichment. • The variable evolution of ore-forming fluids in the Youjiang Basin led to the various relationships of Au and As in pyrite. • Gold precipitation was controlled by the extrinsic fluid conditions and microscopic reactions at the fluid–mineral interface. The low-temperature geochemistry of gold (Au) and arsenic (As) in pyrite from Carlin-type Au deposits is significant for understanding the enrichment mechanisms of Au in pyrite, but remains poorly understood due to the complex processes that lead to the precipitation of micron-scale pyrite grains. This paper concerns the geochemical behaviors of Au and As during the precipitation of pyrite from six Carlin-type Au deposits (the Nibao, Shuiyindong, Banqi, Jinya, Yata, and Zimudang deposits), southwest China. These deposits are located in different locations and ore-bearing horizons of the Youjiang Basin. Arsenian pyrite and/or arsenopyrite are the dominant Au-bearing minerals. Gold-bearing pyrite grains are typically zoned (core, intermediate, and rim), with multiple, oscillatory banded sub-zones. In situ analysis demonstrates that invisible Au exists mainly as cationic Au+ in the growth zones of pyrite. Gold and As are positively correlated (i.e., coupled) in the Nibao and Shuiyindong deposits, negatively correlated in the Banqi, Jinya, and Yata deposits, and poorly correlated in the Zimudang deposit. Arsenic and S substitution in pyrite and the presence of a reduced fluid promoted the incorporation of Au, resulting in the coupling of Au and As. The Au precipitation was affected by changes in the physicochemical conditions of the hydrothermal systems, independent of the As concentration, resulting in decoupling of Au and As. As such, invisible Au precipitation is controlled by the extrinsic physicochemical conditions of the ore-forming fluids and microscopic reactions at the fluid–mineral interface, and also the episodic incursion of Au-rich hydrothermal fluids. High As contents in pyrite favor Au incorporation, but are not solely responsible for Au enrichment. Gold and As contents in pyrite in Carlin-type Au deposits may be coupled or decoupled. [ABSTRACT FROM AUTHOR]

[Display omitted] • The independent selenides coexisting with tellurides and sulfides were discovered for the first time in the Zhaishang gold deposit. • The ore-forming materials leached from the underlying Paleozoic strata, and were affected by Indosinian magmatism. • The mineral paragenetic association shows that the redox conditions have changed from reduction to oxidation during the fluid evolution process. • The sulfur, tellurium and selenium fugacity of hydrothermal fluid of the main metallogenic stage is estimated in this paper. The Zhaishang gold deposit is characterized by Au–Sb–W paragenetic association, hosted in the Middle Devonian strata and Lower Permian strata of the Western Qinling Orogen, Central China; also found in in the mining area is a small carbonatized diorite porphyrite. Besides common sulfides, such as pyrite, arsenopyrite and chalcopyrite, some specific telluride and selenide minerals were found, and especially the first discovery of independent selenides. The assemblage pyrrhotite–arsenianpyrite–arsenopyrite suggests a relatively reducing environment for mineralization during stage II. However, the occurrence of selenides (clausthalite, tiemannite) and sulfates (barite and gypsum) represents a change of redox conditions from reduction to oxidation in stage III. On this basis, combined with the study of fluid inclusions and thermodynamic data, we evaluated the physicochemical conditions of the main metallogenic stages. the sulfur fugacity (log f S 2) did not change significantly from stage II to stage III, the selenium fugacity (log f Se 2) values were constrained to have been ≤ -13.7 in stage II, ranged from −14.8 to −9.8 in stage III, and the tellurium fugacity (log f Te 2) ranged from −14.0 to −11.2 in stage III. Moreover, the He–Ar–Pb isotopic values of sulfides suggest that ore-forming materials were dominantly of stratigraphic source but with important additions of magmatically derived hydrothermal fluid during Indosinian period. Water-rock reaction and ore-forming fluid mixed with magmatically-derived hydrothermal fluid were likely the dominant mechanisms of precipitation. Meanwhile, boiling likely played a certain role in the deposition of selenides and tellurides. [ABSTRACT FROM AUTHOR]

• River sediments in the eastern and western Fujian have distinct source rock compositions. • Indosinian magmatic rocks predominantly originated from the Proterozoic crust. • Yanshanian magmatic rocks originated from both the DM (Depleted Mantle) and Proterozoic crust. • The middle Zhenghe-Dabu Fault predominantly account for geochemical heterogeneity of river sediments. The Cathaysia Block is featured by intense tectonic activities and magmatic intrusions during the Mesozoic, and its geochemical evolution might greatly imprint the river sediment compositions in southeast China. This paper presents a comprehensive synthesis of data from petrology, U-Pb geochronology, and geochemistry of both river sediments and plutons in Fujian Province, and aims to reveal the constraints of Mesozoic geochemical heterogeneity and geochronology of the Northeast Cathaysia Block on local river sediment geochemistry. The Fujian terrane and relating river systems can be divided into western and eastern parts with the boundary of the Zhenghe-Dabu Fault. The sediments of eastern rivers are characterized by heavy minerals derived from granites and two major U-Pb age groups (90–110 Ma and 120–150 Ma) of detrital zircons. However, the sediments of western rivers are featured by heavy minerals from the Precambrian rocks and have seven zircon U-Pb age groups (from 90 Ma to 3.0 Ga). The Indonesian magmatic rocks predominantly originated from the Proterozoic crust, with less contribution from the depleted mantle, which are much different from the Yanshanian A-type granites and gabbros in the eastern terrane. We infer that the middle part of Zhenghe-Dabu Fault formed in the Jingningian Period primarily caused geochemical and geochronological heterogeneity of the Northeast Cathaysia Block, which further determined the totally different sediment compositions between the western and eastern Fujian rivers. [ABSTRACT FROM AUTHOR]

This paper presents the distribution of total phosphorus (P), inorganic P (IP) and organic P in sediment cores from Sishili Bay, China. Their concentrations (μmol g − 1 ) ranged from 15.04 to 21.59, 12.43 to 18.27 and 0.15 to 5.11, respectively, showing 87.6–96.9% of TP is IP. The distribution of the fractionation of IP , obtained by a sequential extraction technique, was 1.9–3.2% for soluble and loosely bound P (Ex-P), 8.5–13.1% for Al-bound from (Al-P), 7.4–9.5% for Fe-bound P (Fe-P), 5.0–12.4% for reductant-soluble P (Oc-P), 9.7–15.6% for CaCO 3 -bound P (ACa-P) and 45.9–54.6% for detritus P (Det-P). The P distribution and concentration was consistent with other Chinese coastal seas. No significant difference was found for the sedimentary P forms between scallop cultivation area and background area, indicating that shellfish aquaculture did not have significant effect on the depositional environment in the studied area, at least in case of P. [ABSTRACT FROM AUTHOR]

This introduction outlines the papers collected in the special issue "Geology of China and Adjacent Regions". The papers focus on scientific issues from Archean to Cenozoic geology in the areas including Northwest Pacific to western Central Orogenic Belt concerning tectonics, geophysics, petrology, geochemistry, mineral deposit, and energy resources. A tectonic framework of China and adjacent regions is briefly introduced. [ABSTRACT FROM AUTHOR]

[Display omitted] • The source areas of the sediments experienced weak to medium chemical weathering. • Elemental diagrams indicate that the shales were primarily from igneous rocks. • Sediments in the southeast part were sourced in the tectonically active Dianqian and Xuefeng Uplifts. • Sediments of the northwest area were transported from the passive margin setting. Organic-rich shales of the Lower Silurian Longmaxi Formation have produced commercial amounts of natural gas. The nature of the paleoclimate and tectonic setting of the provenance region from which these deposits were derived remains the topic of debate. This paper describes the results of a multi-faceted geochemical investigation of 46 samples of the Longmaxi Formation of the Upper Yangtze Platform. Chemical Index of Alteration (CIA) values of the analyzed samples indicate that parent rock experienced relatively weak to medium chemical weathering prior to deposition. Th/Sc, and Zr/Sc ratios suggest that the sediment shed from the provenance area experienced three kinds of different recycling and sorting trend. Variations of Index of Compositional Variability (ICV) and K 2 O/Al 2 O 3 ratios suggest that the sediment source shifted over paleogeographic locations. The Al 2 O 3 -(CaO*+Na 2 O)-K 2 O triangular diagram, Th/Sc and Th/Yb ratios, and Al 2 O 3 -TiO 2 , TiO 2 -Zr, and La/Th-Hf bivariate diagrams suggest that the sediment was primarily derived from felsic and intermediate igneous rocks. High- and low-silica multidimensional diagrams and discriminant function-based multidimensional diagrams indicate an active tectonic setting for the sediments in the south and east of the Upper Yangtze Platform and a passive continental margin setting for the sediments in the north part. Also they illustrate that the sediments in the central and west part were sourced in both an active tectonic setting and a passive continental margin. Variation of multiple geochemical proxies provide new insight into temporal and spatial variations of the provenance, climate, and tectonic setting from which sediment of the Longmaxi Formation were derived. [ABSTRACT FROM AUTHOR]

Under the influence of glacial-interglacial climate change and regional tectonic activities in the Quaternary, the sedimentary environments of the Bohai Sea changed greatly, providing significant information on transgression-regression events, East Asian monsoon changes and regional tectonic activities. This study analyzed the sedimentological characteristics of the BH1302 core (water depth of 12.3 m, length of 70.2 m) in the southern Bohai Sea based on grain size, foraminiferal assemblages, carbon and oxygen isotopes in foraminiferal shells and element geochemistry, and established a chronological framework based on AMS 14C, optically stimulated luminescence dating and Oxcal age-depth model using Bayesian modeling. The results showed that three interglacial transgressions and one interstadial transgression were revealed in BH1302 since the late Quaternary, corresponding to marine isotope stages (MIS) 7, 5, 3 and 1, and three subinterglacial transgressions were further identified during MIS 7. The sedimentary environments of Laizhou Bay transitioned from an estuary environment dominated by rivers to a neritic environment dominated by marine conditions because of subsidence of the Miaodao uplift in late MIS 7.1. Three subinterstadial transgressions occurred in both MIS5 with two subinterstadial in MIS 3, and the highstand sea level of MIS 3 reached approximately −18 ∼ −21 m. Under the influence of sea level fluctuations and the East Asian monsoon, the sedimentary environments of MIS 1 can be divided into a low salinity tidal-flat environment (12.0–7.0 kyr BP), a low salinity neritic environment (7.0–4.5 kyr BP) and a modern neritic environment (∼4.5 kyr BP). • The isotopes in the foraminifera shells have good indications to the impact of freshwater input on the neritic environments. • Except for 4 interglacial transgressions, the paper further identifies 3 sub-interglacial transgressions in the MIS7 period. [ABSTRACT FROM AUTHOR]

The Daye district in eastern China is featured by numerous granitoid intrusions of Early Cretaceous ages that intrude Paleozoic to Early Triassic marine carbonate and clastic rocks. Several dozen skarn Cu-Fe-Au deposits occur along the intrusive contact zones of the Echeng, Tieshan, Jinshandian, Lingxiang, Tongshankou and Tonglushan intrusions. However, no economic skarn mineralization has been recognized in other intrusions and whether or not these intrusions are metal fertile remain unresolved. In this paper, we use whole-rock and mineral (zircon, apatite and amphibole) geochemistry to provide significant new insights into the petrogenesis and metal fertility of the Yinzu granitoid pluton. The Yinzu pluton mainly consists of quartz diorite and diorite phases that have zircon U-Pb ages of 148.4 ± 1 Ma and 146.6 ± 1.6 Ma, respectively. Whole-rock Sr-Nd isotopic compositions ((87Sr/86Sr) i = 0.70635 to 0.70741; ε Nd (t) = −8.74 to −3.73) and zircon hafnium isotopes (ε Hf (t) = −9.1 to −4.8) overlap with values of the Cu-fertile Tongshankou and Tonglushan granitoids, implying a common enriched lithospheric mantle source. The whole-rock geochemical data suggest that both the diorite and quartz diorite have experienced variable degrees of fractional crystallization of olivine, amphibole, titanite and magnetite. The Ce4+/Ce3+ ratios (16–445) and oxygen fugacity (log f O 2) calculated using trace element concentrations of zircon (ΔFMQ = +0.2 to +2.4) suggest that both intrusive phases crystalized from oxidized melts similar to Cu-fertile magmas in the world, with the quartz diorite being well comparable to the Tongshankou and Tonglushan granitoids. Based on available melt-apatite partitioning models, the estimated S and Cl contents for the magmas parental to the Yinzu pluton are akin to those of the Cu-fertile granitoids in the Daye district. Rocks of the Yinzu pluton display high apatite Sr/Y (0.38–3.01) and Eu/Eu* (0.35–0.71) ratios as well as high zircon Eu/Eu* (0.51–0.86) and 10000*(Eu/Eu*)/Y (2–27) ratios, indicating significant fractionation of amphibole with limited plagioclase fractionation and high magmatic water contents (>4 wt% H 2 O). This view is consistent with the calculated melt H 2 O content of 4.3–6.1 wt% based on the amphibole compositions. Collectively, results presented here indicate that magmas generating the Yinzu pluton are hydrous, oxidized and S-rich, characters similar to the Cu-fertile granitoids in Daye and elsewhere. Thus, the Yinzu pluton is considered to be Cu-(Au) fertile. This consideration is partially supported by occurrences of several vein-type Cu prospects within and disseminated Au ores in Silurian clastic sedimentary rocks immediately to the southeast of this pluton. Based on the regional metallogeny and results of this study, we suggest that the Yinzu pluton is a promising target of future Cu-(Au) exploration. • Zircon and apatite record magma volatile compositions and oxygen fugacity. • Zircon and apatite are useful tools in evaluating magma fertility. • Yinzu pluton is hydrous, oxidized and S-rich. • Yinzu pluton is a promising target of future exploration. [ABSTRACT FROM AUTHOR]

Hydrothermal sedimentation occurred in the Triassic Yanchang Formation, Ordos Basin, China. However, their macroscopic features at the scale of the stratum and hydrothermal sources still lack correlational research. This paper performed element geochemical study on a large number of core samples collected from the Yanchang Formation of a new drilling well located in the south Ordos Basin. The SiO 2 /(K 2 O + Na 2 O) vs. MnO/TiO 2 crossplot and Fe vs. Mn vs. (Cu + Co + Ni) × 10 ternary diagram demonstrate that the Yanchang stratum in the study area has, in general, hydrothermal components. The Al/(Al + Fe + Mn) and (Fe + Mn)/Ti ratios of the core samples range from 0.34 to 0.84 and 4.81 to 50.54, averaging 0.66 and 10.67, respectively, indicating that the stratum is a set of atypical hydrothermal sedimentation with much terrigenous input. Data analysis shows that the hydrothermal source in the study area was from the deep North Qinling Orogen around the south margin of the basin, where some active tectonic and volcanic activities took place, rather than from the relatively stable internal basin. Early Indosinian movement and volcanic activities activated basement faults around the southern margin of the basin, providing vents for the deep hydrothermal fluid upwelling. The hydrothermal indicators suggest that the study area experienced 4 episodes of relatively stronger hydrothermal activity, namely during the Chang 10, Chang 9–1, Chang 7–3 and Chang 6–2 periods. We also propose a new hydrothermal sedimentation model of hydrothermal fluids overflowing from basin margin faults, for the Yanchang Formation, which is reported here for the first time. [ABSTRACT FROM AUTHOR]

In recent years mineral exploration has concentrated on concealed deposits in regolith-covered terrains. In China, the regolith-covered landscapes mainly include desert windblown sand basins, desert peneplains, semi-arid grassland, loess plateaus, forestry land, alluvial plains and laterite terrains. These diverse regolith-covered areas represent geochemical challenges for mineral exploration in China. This paper provides an overview of recent progress on mechanisms of metal dispersion from the buried ore deposits through the transported cover to the surface and penetrating geochemical methods to detect the anomalies. Case studies show that, in arid and semi-arid desert sand-covered terrains, sampling of fine-fraction (− 120 mesh, < 0.125 mm) clay-rich horizon soil is cost-effective for regional geochemical surveys for sandstone-type uranium, gold, and base metal deposits. Fine-fraction sampling, selective-leaching and overburden drilling geochemical methods can effectively indicate the 210 gold ore body at Jinwozi goldfield. In alluvium-covered terrains, fine-grained soil sampling (− 200 mesh, < 0.074 mm) combined with selective leaching geochemistry shows clear ring-shaped anomalies of Cu and Ni over the Zhouan concealed Cu–Ni deposit. In laterite-covered terrains, the anomalies determined by the fine-fraction soils and selective leaching of absorbed metals on coatings of Fe–Mn oxides coincide well with the concealed deposit over the Yueyang ore deposits at the Zijin Au–Cu–Ag field. Nanoparticles of hexagonal crystals mainly native copper, gold and alloys of Cu–Fe, Cu–Fe–Mn, Cu–Ti, and Cu–Au were observed in gases, soils and ores using a transmission electron microscope (TEM). The findings imply that nanoparticles of gold and copper may migrate through the transported cover to the surface. Uranium is converted to uranyl ions [UO 2 2 + ] under oxidizing conditions when migrating from ore bodies to the surface. The uranyl ions are absorbed on clay minerals, because clay layers have a net negative charge, which needs to be balanced by interlayer cations. Nanoparticles of Au and Cu and ion complexes of U are more readily absorbed onto fine fractions of soils containing clays, colloids, oxides and organic matters. Thus, fine-grained soils enriched with clays, oxides and colloids are useful media for regional geochemical surveys in regolith-covered terrains and in sedimentary basins. Fine-fraction soil sampling combined with selective leaching geochemistry is effective for finding concealed ore bodies in detailed surveys. Penetrating geochemistry at surface sampling provides cost-effective mineral exploration methods for delineation of regional and local targets in transported cover terrains. [ABSTRACT FROM AUTHOR]

Organic-rich shales spanning in age from Pre-Cambrian to Quaternary were widely deposited in China. This paper elaborates the geology and unique characteristics of emerging and potential hydrocarbon-bearing shales in China. The Pre-Cambrian Sinian Doushantuo to Silurian black marine shales in the intra-shelf low to slope environments were accumulated in South China and Tarim Platform in Northwest China. These marine shales with maturity (Ro) of 1.3–5% are in dry gas window. During Carboniferous to Permian, the shales associated with coal and sandstones were mainly deposited in coastal swamp transitional setting in north China, NE China, NW China and Yangtze platform in South China. These transitional shales are generally clay rich and are potential gas-bearing reservoirs. Since Middle Permian, the lacustrine shales with total carbon content (TOC) up to 30% and Ro mainly in oil window are widely distributed in all the producing basins in China. The lacustrine shales usually have more clay mineral content than marine shales and are characterized by rapid facies change and are interbedded with carbonates and sandstone. The high quality shale reservoir with high TOC, hydrocarbon content and brittle minerals content is usually located at transgressive systems tract (TST) to early highstand systems tract (EHST) interval deposited in anoxic depositional setting. Recent commercial shale gas production from the Silurian Longmaxi marine shale in the southeastern Sichuan Basin, preliminary tight oil production associated with lacustrine hydrocarbon-bearing shale intervals and hydrocarbon shows from many other shales have proven the hydrocarbon-bearing shales in China are emerging and potential shale gas and tight (shale) oil plays. Tectonic movements could have breached the early hydrocarbon accumulation in shales and tectonically stable areas are suggested to be favorable prospects for China shale plays exploration and production. [ABSTRACT FROM AUTHOR]

The tectonic setting of the late Paleoproterozoic suite of anorthosite, mangerite, charnockite and alkali-feldspar granite (AMCG) on the northern margin of the North China Craton (NCC) is controversial. This paper reports on the petrology, geochronology and geochemistry of the Beibaiqi, Beipuzi and Shibalitai mangerites in the Longhua area and the Shinao mangerite in the Jianping area. Zircon U–Pb dating reveals that these mangerites formed 1768–1725 Ma, similar to the other lithologies (1753–1673 Ma) of the AMCG suite on the northern margin of the NCC. The mangerites have intermediate SiO 2 contents (57.2–66.8 wt.%) and high K 2 O (4.04–7.05 wt.%) and Na 2 O (3.75–5.50 wt.%) contents, which belong to alkaline series rocks. They are enriched in light rare-earth elements (REEs) and large-ion lithophile elements (LILEs) of Rb, Ba and K, and they are depleted in heavy REEs and the high field-strength elements (HFSEs) of Th, U, Nb, Ta, Ti and P. The zircon ɛ Hf ( t ) values of these mangerites are negative (−8.3 to −1.7), with depleted mantle model ages ( T DM ) and average crustal two-stage modal ages ( T 2DM ) from 2250 Ma to 2533 Ma and 2573 Ma to 2959 Ma, respectively. These geochemical characteristics suggest that these mangerites originated from the early Precambrian lower crust of the NCC. Compared with the mangerites, the other lithologies of the AMCG suite display different evolutionary trends of their major elements and different distribution patterns of their REEs and trace elements, indicating that those lithologies were not formed through fractional crystallization by the same primary magma. The anorthosites share similar distribution patterns of REEs and trace elements and zircon Hf isotopic composition with associated norites. The data suggest that the anorthosites were formed by noritic magmas through fractional crystallization at the base of the lower crust. The alkali-granites and rapakivi granites display the geochemical features of A-type granites, and might have originated from partial melting of the mid-upper crust. Combined with regional geological data, these findings suggest that the AMCG suite occurred in a post-collisional/post-orogenic extensional setting rather than an anorogenic continental rift setting. [ABSTRACT FROM AUTHOR]

Ammonian illite is observed to be presented in the intra-seam coal partings of the Permo-Carboniferous coal seams from the Qinshui Coalfield, North China. This paper provides new insights into its geochemical and mineralogical characteristics, as well as the factors influencing its formation and its nitrogen isotope ratios. The interlayer cations of ammonian illite in the samples presented in this study were dominated by NH 4 + with a certain amount of K + and distributed homogeneously in each illite layer. Ammonian illite has an NH 4 + /(NH 4 + + K + ) ratio of 0.87 on average, with a basal spacing (d 001 , 10.267 Å on average) greater than those of potassian illite and muscovite, but lower than that of tobelite. The average stoichiometric formula of the ammonian illite was inferred as (NH 40.67 ,K 0.11 )(Al 1.90 ,Fe 0.06 ,Mg 0.04 )(Al 0.68 ,Si 3.32 )O 10 (OH) 2 , and the average Si/Al IV ratio (4.88) was found to be higher than that of tobelite. This indicates that the conversion of ammonian illite to tobelite includes the expulsion of Si from the tetrahedral sheets and the incorporation of Al into the octahedral and tetrahedral sheets. The d 005 is influenced not only by the NH 4 + /(NH 4 + + K + ) ratio but also, to some extent, by the entrance of Al IV into tetrahedral sites. It is inferred that the ammonian illite was formed by the incorporation of Si into pre-existing kaolinite during diagenesis, and that its formation was influenced not only by the diagenetic temperature but also by the depositional environment. Brackish water favors the formation of ammonian illite during deposition. The NH 4 + of the ammonian illite was mainly derived from pyrrolic (N-5) and pyridinic (N-6) nitrogen groups at the margins of the coal's carbon matrix during diagenesis. On average, it has a δ 15 N value of + 8.0‰, much higher than that of total coal nitrogen (+ 3.9‰ on average). This is related mainly to the higher δ 15 N values of N-5 and N-6 than the quaternary nitrogen group (N-Q) within the carbon matrix. [ABSTRACT FROM AUTHOR]

Abstract The paper "Enrichment of Bi-Be-Mo-Cd-Pb-Nb-Ga, REEs and Y in the Permian coals of the Huainan Coalfield, Anhui, China" by Munir et al. (2018) provides new data on the geochemical compositions of the late Paleozoic coals from five different mines in the Huainan Coalfield, China, as well as proximate analyses, vitrinite reflectance measurements, maceral contents, and mineralogical constituents. A critical examination, however, suggests that a large proportion of the reported data are questionable, and also that references cited at a number of points are either improper or incomplete. [ABSTRACT FROM AUTHOR]

The volcanic rock system of the Miaoling Formation contains the main ore-bearing rocks of two volcanogenic massive sulfide (VMS)-type deposits in the Yanbian area of NE China. Investigation of the VRSMF is needed to better understand the formation of these VMS-type deposits and the tectonic evolution of the Yanbian area. To determine the petrogenesis, material sources, and formation age of the VRSMF, and elucidate its late Paleozoic tectonic evolution and metallogenic significance, this paper presents new petrological, geochronological, geochemical, whole-rock Sr–Nd and in situ zircon Hf isotopic data for the VRSMF. The VRSMF is composed of marine carbonate, intermediate–felsic volcanic rocks (andesite–trachyandesite–dacite) and pyroclastic rocks. Laser-ablation–inductively coupled plasma–mass spectrometry zircon U–Pb dating gives an eruption age of ca. 265 Ma for the pyroclastic rocks in the VRSMF. These rocks are classified as low- to medium-K calc-alkaline series. They are characterized by enrichments in large-ion lithophile elements (e.g., K, Rb, and Ba) and light rare earth elements, and depletions in high field-strength elements (e.g., Nb, Ta, and Ti) and heavy rare earth elements, showing affinity to igneous rocks formed in arc-related tectonic settings. These features, together with homogeneous zircon ε Hf (t) values of 10.9–15.7 and depleted Sr–Nd isotopic compositions [ε Nd (t) values of 2.4–5.0], suggest that the parental magma was derived from the partial melting of depleted mantle that had been metasomatized by subduction-related fluids. These results, along with findings of regional geological investigations, suggest that the formation of the VRSMF was related to subduction of the Paleo-Asian oceanic plate during the middle Permian. The VMS-type mineralization in the Hongtaiping and Dongfengnanshan deposits is interpreted to have formed in a bimodal–felsic setting in a back-arc extensional tectonic environment. [ABSTRACT FROM AUTHOR]

Catchment/floodplain sediment geochemical datasets from three continental-scale geochemical projects in Australia (AU), China (CH) and Europe (EU) were studied by comparing sample media, sample preparation, elements determined, analytical methods, detection limits and proportions of reportable values, and certified reference materials used. Twenty six elements (Ba, Ce, Co, Cr, Cu, Mo, Nb, Ni, Pb, Rb, Sr, Th, V, Y, Zn, Zr, Al 2 O 3 , CaO, K 2 O, MgO, MnO, Na 2 O, P 2 O 5 , SiO 2 , Fe 2 O 3 (total), TiO 2 ) were considered comparable among the 35 determined by all three projects, according to the criteria for global comparability of elements proposed in this paper. The median concentrations of all elements (except Co, Y, Zr, SiO 2 and TiO 2 ) in the three datasets increase in the following order: AU < EU ≤ CH, and the median CH/EU ratios for all elements range from 0.98 to 1.94, while the median CH/AU and EU/AU ratios for elements, such as CaO, Na 2 O, MgO and Zn are generally greater than 2 (and up to 7), which could be explained partly by protracted weathering in Australia, and partly by the smaller grain size fraction analysed of the CH dataset (< 1 mm) compared to AU and EU (< 2 mm). In conclusion, a unified sample medium should be collected and unified sample preparation techniques should be followed. Key elements related to mineral resources and the environment should be determined and international or exchanged internal standard materials inserted in new national or global geochemical mapping projects in order to generate globally comparable datasets for establishing global geochemical baselines. [ABSTRACT FROM AUTHOR]

The barite deposits hosted in early Cambrian black shales in South China are a classic example of sediment-hosted stratiform barite deposits, and their origin is controversial. In this paper, we address the origin of these deposits by a comprehensive integrated study of mineralogy and geochemistry, based on a case study of the Dahebian deposit in Tianzhu County, Guizhou Province, which contains the largest global reserve of barite. Particular attention was paid to a comparison between ore and non-ore horizons, as this has not been fully addressed previously. The results indicate that the ore horizon is dominated by barite with intergrown hyalophane, quartz and pyrite. The hyalophane is zoned, implying hydrothermal activity. In contrast, the non-ore horizons contain minor amounts of granular barite and are free of hyalophane, suggesting that these horizons experienced weaker hydrothermal activity. The contrasting trace and rare earth element compositions of the ore and non-ore samples indicate dilution of complex geochemistry with multiple ore-forming processes and materials during barite mineralization. The barite mineralization was rapid, as demonstrated by the relatively low terrigenous input in the ore samples compared with the non-ore samples. The ore samples have positive Eu anomalies (>3.0), indicative of hydrothermal activity during mineralization. Organic geochemical analyses provide evidence of the development of abundant organic matter and hydrothermal activity. The sulphur isotopic values (δ 34 S) of the ore samples show an enrichment relative to contemporaneous early Cambrian seawater and substantial variation (+36.7‰ to +43.8‰), indicative of sulphur derived from seawater that was affected by sulphate-reducing bacteria and hydrothermal activity in a restricted marine environment. To summarize, the barite deposit in the Dahebian site was most likely formed in a generally restricted and reducing marine basin environment with rapid sedimentation during a period of hydrothermal activity. These results have general implications for the future study of other black-shale-hosted deposits worldwide. [ABSTRACT FROM AUTHOR]

The Awulale metallogenic belt (AMB) of the western Tianshan (NW China) includes Late Carboniferous (ca. 320 Ma) ore-bearing volcanic rocks of the Dahalajunshan Formation. The petrogenesis and tectonic setting of these volcanic rocks are important for the understanding of the tectonic evolution and metallogeny of the western Tianshan. This paper presents new major and trace elements and Sr–Nd–Pb isotope data from the Dahalajunshan volcanic rocks, which are mainly calc-alkaline basaltic trachy-andesite and trachy-andesite with subordinate basalt, trachy-basalt and rhyolite. The variations of major and trace elements in the mafic and intermediate volcanic rocks indicate the fractionation of pyroxene and magnetite or hornblende, magnetite, apatite and plagioclase, respectively, during their petrogenesis. The Dahalajunshan volcanic rocks have similar primitive mantle-normalized diagrams and chondrite-normalized rare-earth element (REE) patterns suggesting their similar mantle source(s). They are characterized by enrichment in large ion lithophile elements (LILEs) and light REEs (LREEs), depletion in heavy REEs (La N /Yb N ≈ 2.80 to 9.59) and high field strength elements (HFSEs) and ε Nd ( t ) ranging from + 1.2 to + 6.0 at 86 Sr/ 87 Sr ( t ) = 0.7047–0.7063 and 206 Pb/ 204 Pb i = 17.49–18.19. Both the geochemical and isotopic data indicate that the volcanic rocks were probably derived by low-degree melting of sub-arc lithospheric mantle modified by fluids in a continental arc setting. Our obtained results, in conjunction with previous published data, allow us to suggest that the southward subduction of Junggar oceanic crust continued until the Late Carboniferous and was followed by a tectonic shift from continental arc to post-collisional extension environment. [ABSTRACT FROM AUTHOR]

The Dabie orogen is among the most famous continent–continent collisional orogenic belts in the world, and is characterized by intensive post-collisional extension, magmatism and Mo mineralization. However, the genetic links between the mineralization and the geodynamic evolution of the orogen remain unresolved. In this paper, the Yaochong Mo deposit and its associated granitic stocks were investigated to elucidate this issue. Our new zircon U–Pb ages yielded an Early Cretaceous age (133.3 ± 1.3 Ma) for the Yaochong granite, and our molybdenite Re–Os dating gave a similar age (135 ± 1 Ma) for the Mo deposit. The Yaochong stock is characterized by high silica and alkali but low Mg, Fe and Ca. It is enriched in light rare earth elements (LREEs) and large ion lithophile elements (LILEs: Rb, K, Th and U), but strongly depleted in heavy REEs, and high field strength elements (HFSEs: Nb, Ta, Ti and Y). The Yaochong granite has initial 87 Sr/ 86 Sr ratios of 0.7087–0.7096, and Pb isotopic ratios of ( 206 Pb/ 204 Pb) i = 16.599–16.704, ( 207 Pb/ 204 Pb) i = 15.170–15.618 and ( 208 Pb/ 204 Pb) i = 36.376–38.248. The granite has ε Nd ( t ) of −18.0 to −16.3 and ε Hf ( t ) values of −26.5 to −20.0. All these data indicate that the Yaochong granite is a high-K calc-alkaline fractionated I-type granite, and may have originated from partial melting of the thickened Yangtze continental crust. The Mo ores also show low radiogenic Pb isotopes similar to the Yaochong stock. Medium Re content in molybdenite (21.8–74.8 ppm) also suggests that the ore-forming materials were derived from the thickened lower crust with possibly minor mixing with the mantle. Similar to the Eastern Dabie orogen, the thickened crust beneath the Western Dabie orogen may also have experienced tectonic collapse, which may have exerted fundamental geodynamic controls on the two-stage Mo mineralization in the region. [ABSTRACT FROM AUTHOR]

Catchment/floodplain sediment geochemical datasets from three continental-scale geochemical projects in Australia (AU), China (CH) and Europe (EU) were studied by comparing sample media, sample preparation, elements determined, analytical methods, detection limits and proportions of reportable values, and certified reference materials used. Twenty six elements (Ba, Ce, Co, Cr, Cu, Mo, Nb, Ni, Pb, Rb, Sr, Th, V, Y, Zn, Zr, Al 2 O 3 , CaO, K 2 O, MgO, MnO, Na 2 O, P 2 O 5 , SiO 2 , Fe 2 O 3 (total), TiO 2 ) were considered comparable among the 35 determined by all three projects, according to the criteria for global comparability of elements proposed in this paper. The median concentrations of all elements (except Co, Y, Zr, SiO 2 and TiO 2 ) in the three datasets increase in the following order: AU < EU ≤ CH, and the median CH/EU ratios for all elements range from 0.98 to 1.94, while the median CH/AU and EU/AU ratios for elements, such as CaO, Na 2 O, MgO and Zn are generally greater than 2 (and up to 7), which could be explained partly by protracted weathering in Australia, and partly by the smaller grain size fraction analysed of the CH dataset (< 1 mm) compared to AU and EU (< 2 mm). In conclusion, a unified sample medium should be collected and unified sample preparation techniques should be followed. Key elements related to mineral resources and the environment should be determined and international or exchanged internal standard materials inserted in new national or global geochemical mapping projects in order to generate globally comparable datasets for establishing global geochemical baselines. [ABSTRACT FROM AUTHOR]

This paper reports a geochemical study on the major and trace elements and Pb–Sr isotopes of a weathering profile developed in the Lower Cambrian black shales in central Hunan (China). Six weathering horizons were identified and sampled vertically throughout the profile. The chemical composition of the profile consists of variable concentrations of the major elements Fe 2 O 3 , FeO, MnO, MgO, CaO, Na 2 O, and P 2 O 5 and of less variable concentrations of SiO 2 , TiO 2 , Al 2 O 3 , and K 2 O. The chemical change caused by weathering is estimated by mass-balance calculations, and the results show that the element mobility is characterised by substantial loss of SiO 2 , FeO, CaO, K 2 O, Na 2 O, LOI, Cr, V, Ba, Cs, Rb, Sr, U, and Th, and moderate loss of Al 2 O 3 , MgO, Fe 2 O 3 , Ni, Cu, Pb, Tl, Sn, Sc, Ge and REE (Y). The high field strength elements TiO 2 , Sn, Sc, U, Ga, Ge, Zr, Hf, Nb, and Ta were immobile during weathering. The chemical changes and the Pb–Sr isotopic data suggest that four types of chemical reactions occurred: the oxidation of sulphide minerals (e.g., pyrite) and organic carbon (OS), the dissolution of less resistant clinochlore-Ia, calcite, and P-bearing minerals (DL), the dissolution of detrital albite and microcline (DA), and the transformation of clay (TC) minerals (e.g., muscovite and illite–smectite). These chemical reactions then led to two stages of geochemical processes, an early stage of chemical differentiation and a later stage of chemical homogenisation. The chemical differentiation dominated by the OS, DL, and DA reactions, led to the leaching of mobile elements (e.g., MgO, Na 2 O, K 2 O, P 2 O 5 , Sr, and REE) and the redistribution of some less mobile elements (e.g., SiO 2 and Al 2 O 3 ). In contrast, the chemical homogenisation, which was caused by TC reactions, led to the leaching of both mobile and less mobile elements from the system and ultimately transformed the weathered black shales into soil. Soils derived from black shales in South China might result from the above two geochemical processes. [ABSTRACT FROM AUTHOR]

Identifying the composition of the recycled materials in the lithospheric mantle is crucial for establishing links between mantle geochemical 'reservoirs' and deep mantle geodynamic processes. However, studies that focus on deep mantle processes under multiple subduction tectonic regimes have been absent. In this paper, we present 40Ar/39Ar age, whole-rock geochemical, and Sr–Nd–Pb–Hf isotope, zircon Hf-O isotope, and in situ plagioclase Pb isotope data for Mesozoic mafic–intermediate volcanic rocks in the northern Great Xing'an Range, northeast China. These and published data are used to constrain the deep processes that occurred in the lithospheric mantle during the Mesozoic, in the context of the evolution of the Mongol–Okhotsk Ocean and whether subduction of the Paleo-Pacific Plate affected the formation of volcanic rocks in the western part of northeast China. The Mesozoic mafic–intermediate volcanic rocks in the northern Great Xing'an Range can be divided into three stages: Early Jurassic (~180 Ma), Late Jurassic (~155 Ma), and late Early Cretaceous (~120 Ma). These rocks are mainly basalt, basaltic andesite, andesite, and trachyandesite. The Mesozoic mafic–intermediate volcanic rocks have SiO 2 = 47.34–60.00 wt%, TFe 2 O 3 = 4.73–11.63 wt%, and Mg# = 26–66, belong to the medium- to high-K calc-alkaline series, exhibit enrichment in light rare earth elements and large-ion lithophile elements, exhibit depletions in heavy rare earth elements and high-field-strength elements (e.g., Nb and Ta), and have no obvious Eu anomalies. These geochemical features are similar to those of arc igneous rocks. Relative to mid-ocean ridge basalts, these mafic–intermediate volcanic rocks exhibit more radiogenic Sr-Pb and less radiogenic Nd-Hf isotopic compositions. The Th/Yb (1.47–3.43) and (Hf/Sm) PM (0.80–1.15) ratios of the Early Jurassic mafic–intermediate volcanic rocks are much lower than those of the Late Jurassic mafic–intermediate volcanic rocks (Th/Yb = 4.31–5.25; (Hf/Sm) PM = 1.49–2.60), whereas the late Early Cretaceous igneous rocks exhibit large variations in these ratios (Th/Yb = 0.37–14.8; (Hf/Sm) PM = 0.59–2.14). The above features show that: (1) the primary magmas of the mafic–intermediate volcanic rocks were mainly derived by partial melting of depleted lithospheric mantle; (2) the lithospheric mantle was mainly metasomatized by sediment-derived fluids related to subduction of the Mongol–Okhotsk oceanic plate during the Early Jurassic, whereas the mantle source was mainly modified by sediment-derived melts triggered by the collapse of thickened lithosphere after closure of the Mongol–Okhotsk Ocean in the Late Jurassic; and (3) sediment-derived fluids associated with subduction of the Paleo-Pacific Plate caused further enrichment of the lithospheric mantle in the western part of northeast China during the late Early Cretaceous. • J 1 , J 3 and K 1 mafic magmas were derived by melting of depleted lithospheric mantle. • J 1 lithospheric mantle was modified by the Mongol-Okhotsk slab-derived fluid. • J 3 lithospheric mantle was modified by the Mongol-Okhotsk slab sediment-derived melt. • K 1 lithospheric mantle was re-modified by the Paleo-Pacific slab-derived fluid. [ABSTRACT FROM AUTHOR]

Assessment of the synchroneity between the Siberian Traps and the Permo-Triassic boundary (PTB) mass extinction has led to the proposition that the Siberian flood volcanism was responsible for the severest biotic crisis in the Phanerozoic. However, recent studies suggest that the Siberian Traps may have postdated the main extinction horizon. In this paper, we demonstrate, using stratigraphy, a time and intensity coincidence between PTB volcanic ash and the main extinction horizon. Geochemistry of the PTB volcanic ashes in five sections in South China indicates that they were derived from continental magmatic arc. Zircons extracted from the PTB volcanic ashes have negative εHf(t) (- 12.9 to - 2.0) and δ18O (6.8 to 10.9‰), consistent with an acidic volcanism and a crustal-derived origin, and therefore exclude a genetic link between the PTB mass extinction and the Siberian Traps. On the basis of spatial variation in the number of the PTB volcanic ash layers and the thickness of the ash layers in South China, we propose that the PTB volcanic ash may be related to Paleo-Tethys continental arc magmatism in the Kunlun area. Ignimbrite flare-up related to rapid plate subduction during the final assemblage of the Pangea super-continent may have generated a volcanic winter, which eventually triggered the collapse of ecosystem and ultimately mass extinction at the end of the Permian. The Siberian Traps may have been responsible for a greenhouse effect and so have been responsible for both a second pulse of the extinction event and Early Triassic ecological evolution. [ABSTRACT FROM AUTHOR]

Voluminous and discrete early Paleozoic bimodal magmatic suites are thought to be the result of post-collisional extension following the amalgamation of East Kunlun and Altyn Tagh. In this paper, four representative magmatic units were studied for their geochemical fingerprint in conjunction with geochronological studies. The 467-445 Ma Mangya mafic suite shows E-MORB type rare earth element (REE) patterns that are the result of asthenospheric interaction with a metasomatized subcontinental lithosphere. High-K calc-alkaline granodiorites, intruded at ca. 450 Ma, are characterized by high Mg#, the least fractionated REE pattern without an Eu anomaly, as well as high Sr and low Rb/Sr ratio. We interpret these geochemical signals to result from lower crustal melting of garnet amphibolite at pressures between 16 and 22 kbar. A 430-420 Ma A-type granite is interpreted to result from the melting of metaigneous rocks at middle to lower crustal depths. Lastly, a late magmatic pulse occurs between 400 and 380 Ma and is represented by the Alk granite. The Alk granite is interpreted to be a product of metapelite melts and is associated with a smaller volume of mafic melts. U-Pb zircon geochronology of Paleozoic igneous rocks of the Qimantagh-South Altyn reveals that most of the magmatic episodes are either coeval with, or post, extensional deformation. This phase of extension is supported by the exhumation of HP/UHP metamorphic rocks and crustal anatexis. Collectively, the evolutionary stages documented in this study correspond to a succession of post-collisional, postorogenic and, ultimately, within plate magmatic episodes. The overall features support orogenic collapse via removal of a thickened lithospheric root beneath the East Kunlun-Altyn Tagh collisional orogen during early Paleozoic. [ABSTRACT FROM AUTHOR]

Abstract: The Yimin Ge-coal deposit, located in the Yimin coalfield, Inner Mongolia, is the third largest Ge-rich coal deposit in China just after the Lincang and Wulantuga Ge-coal deposits. Based on the coal and non-coal samples recently collected from the Wumuchang coal mining district in the Yimin Ge-coal deposit, this paper reports some new data on the mineralogical and geochemical characteristics of the Yimin high-Ge coals, and provides some new evidence for the possible mode of Ge enrichment in the Yimin coals. Mineralogical analyses were performed by means of Powder X-ray diffraction (XRD). Major and trace element concentrations were determined by inductively coupled plasma atomic-emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS), respectively. Element affinities were determined by Pearson's correlation analysis. The studied coals fall within the coal rank between sub-bituminous A and high volatile bituminous C, with relatively high moisture content, high volatile matter yield and low to medium ash yield. Quartz and kaolinite are the main mineral matters in the Yimin coals, with small amounts of pyrite and traces of microcline. Common pyrite and As-bearing pyrite occurring in the Yimin coals show an epigenetic origin. The epigenetic precipitation of kaolinite, quartz and As-rich pyrite (with Ge, and other trace elements) in the Yimin coal fractures may be caused by activities of both hydrothermal and low temperature fluids. Compared to common Chinese and worldwide coals, the Yimin coals are markedly enriched in Ge (43mg/kg), As (155mg/kg), and W (9.84mg/kg) and slightly enriched in Pb (22mg/kg) and Hg (0.24mg/kg). Most of the elements (e.g. Al, K, Sc, Ti, V, Cu, Ga, Sn, Th and REEs) in the studied coals present an aluminosilicate affinity as deduced from their obvious positive correlation with Al and ash yields. High correlation coefficients of As and Hg with Fe and S indicate a sulfide affinity of these elements in the Yimin coals. Germanium, B, Mo, and W in the studied coals show an organic affinity and a partial sulfur affinity as deduced from their negative correlation with Al and positive correlation with S, respectively. The preliminary and possible model for Ge enrichment in the Yimin Ge-coal deposit was that Ge was carried by hydrothermal fluids and then these fluids were incorporated in the water existing in the upper porous conglomerates and percolate in the top of the coal seam, where Ge was trapped by organic matter and finally enriched in an early diagenetic stage (humification–gelification). [Copyright &y& Elsevier]

Abstract: This paper provides a history of the development of exploration geochemistry in China. Over the past 60years, geochemists in China have made great efforts to develop geochemical exploration methods to cover large areas and even all of China or the whole world, as well as to more elements with emphasis on high sensitivity and accuracy. The new innovative exploration concept and strategies established by the Chinese geochemists have greatly contributed to discoveries of the mineral deposits and to the environmental regulations. [Copyright &y& Elsevier]