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• Two phases of deformation occured in the south of the Shangdan suture zone across the Mianyuzui ductile strike-slip fault. • The metamorphic temperature of the early stage of shearing deformation is ∼ 600-700℃ and ∼ 300-500℃ for the late stage. • The subduction of the Shangdan Oceanic lithosphere was active till the Early Silurian, and subsequent collisions occurred during the Late Silurian. The Shangdan suture zone (SDSZ) subdivides the Qinling Orogenic Belt into North Qinling and South Qinling belts, marking the main tectonic boundary between the North China and South China Blocks. The Mianyuzi ductile strike-slip fault (MYZF) within the SDSZ separates the North China Block from the South China Block and contains valuable collisional information. This paper integrates the structural and geochronological data of the MYZF to investigate the Paleozoic tectonic evolution of the Qinling Orogenic Belt and the collision between the North China and South China Blocks. Two phases of deformation (D 1 -D 2a-b) are identified along the southern boundary of the SDSZ. The metamorphic temperature of mylonites is ∼ 600–700 ℃ for the early stage and ∼ 300–500 ℃ for the late stage of shearing deformation. U-Pb zircon analysis of the mylonites and diabase dike in the ductile shear reveals that zircons have major younger protolith populations at 480–460 Ma, 450–430 Ma, and 405–425 Ma, which suggests that rocks were probably derived from the North Qinling belt. The metamorphism and deformation cooling age from the MYZF have been constrained to be 339–328 Ma and 259 ± 1.6 Ma using U-Pb and 40Ar/39Ar dating. Combined with previously published data, we concluded that the subduction of the Shangdan Ocean was active until the Early Silurian and subsequent collisions occurred during the Late Silurian. Meanwhile, the shearing might have been related to the intraplate extension-exhumation during the Carboniferous-Late Permian in the Qinling Orogenic Belt. [ABSTRACT FROM AUTHOR]

• The 210–205 Ma Habake pluton was formed in a continental collision setting. • The final closure of the Paleo-Tethys in the West Kunlun orogenic belt occurred after 209 Ma. • The parent rocks of rare metal-mineralized pegmatites are all S-type granites and contain >150 ppm Li. Recent discoveries of rare metal pegmatite deposits in the West Kunlun region are believed to be related to Triassic granites. However, the tectonic background of the mineralization in this region is currently unclear. Additionally, the mineralization potential of the granite must be determined to assess whether further exploration is warranted. This paper reports whole-rock elemental and Sr-Nd isotopic compositions, and zircon U-Pb ages and Lu-Hf isotopic compositions for the Habake granitic pluton. The zircon U–Pb dating revealed that these rocks formed in the Late Triassic (210–205 Ma). The two-mica granites are strongly peraluminous high-K calc-alkaline series rocks, with initial 87Sr/86Sr ratios of 0.71294 ∼ 0.71428, εNd(t) values of −7.79 ∼ -8.15, and εHf(t) values of −1.77 ∼ −32.22; these values are similar to those of Triassic BaryanHar Group graywacke rocks. The other granites are weakly peraluminous high-K calc-alkaline series rocks, with initial 87Sr/86Sr ratios of 0.70820 ∼ 0.70823 and 0.70942 ∼ 0.71041, εNd(t) of −3.81 ∼ -4.11 and −5.33 ∼ -5.40, and εHf(t) of −0.90 to +7.02 and −1.39 to −7.68, indicating that the granodiorite and biotite granite were respectively derived from partial melting of the juvenile crust and older lower crust in continental collision stage. Our new data show that the end of the continental collision between the South Kunlun Terrane (SKT) and Tianshuihai terrane (TST) likely occurred after 209 Ma. After analysis of the ore-forming parent rocks of the rare metal pegmatites, the graywacke-derived Habake two-mica granites, has lower Li contents that too low(<150 ppm), indicating that they did not form the rare metal pegmatites. [ABSTRACT FROM AUTHOR]

• High-carbon silty dolomite is the most favorable exploration target for shale oil in Lucaogou Formation of Jimsar Sag. • TOC, microscopic pore-throat structure, and pore types are the key factors controlling the movable oil content of different lithofacies. • A new Conceptual model is given to illustrate multi-scale linkage between lithofacies, pore structure, and fluid occurrence. The heterogeneity of lithofacies is a pivotal factor influencing the shale oil potential. A comprehensive understanding of the intricate influence of rock complexity on hydrocarbon generation properties, microscopic pore-throat structure, and fluid occurrences is crucial for shale oil exploration and development. The Lucaogou Formation in the Jimsar Sag is a type of saline lacustrine shale oil, which was chosen as a research example in this paper. To unravel the causal linkage and confirm the coupling relationship between lithofacies, pores, and fluid mobility in the sedimentary sequence of saline lacustrine basins, a series of experiments were conducted. These included total organic carbon (TOC), X-ray diffraction (XRD), vitrinite reflectance (R o), Rock-Eval pyrolysis, field emission-scanning electron microscopy (FE-SEM), low-field nuclear magnetic resonance (LF-NMR), mercury intrusion porosimetry (MIP), and low-temperature nitrogen adsorption (LTN 2 A). The results revealed significant differences in pores, oiliness, and fluid mobility among the four dominant lithofacies. Employing an innovative comprehensive evaluation method, high-carbon silty dolomite manifests significant potential for hydrocarbon generation, substantial storage capacity, effective oiliness and mobility , heightened brittle mineral content, and facile fracture production. Consequently, it was the most favorable lithofacies. Furthermore, TOC, pore size, and pore types emerged as key factors influencing the movable oil content of different lithofacies. More importantly, a detailed multiscale model illustrated potential linkages across the three different scales of lithofacies associations, pores, and fluid mobility. The study's outcomes can offer enhanced guidance for accurately assessing shale oil resources, particularly in the identification of crucial "sweet spots". [ABSTRACT FROM AUTHOR]

The Qiangtang Basin is one of the largest Mesozoic petroliferous basins in China that is still unexploited for the petroleum industry. The basic geological issues and synthesis of the Qiangtang Basin related to the Tethyan evolution are still poorly understood. This volume presents 20 research papers to address the tectonic settings, basin evolution, and sedimentary environments of the Qiangtang Basin, which are key factors for a better understanding of the overall petroleum system. The Qiangtang Basin holds a Precambrian base developed in response to the Paleo-Tethys Hol Xil-Jinshajiang Ocean evolution, with enhanced sedimentary basin infilling during the opening and expansion of the Neo-Tethys Bangong-Nujiang Ocean in the Mesozoic. The Paleozoic basin framework of the Qiangtang demised as the Paleo-Tethys Ocean closed at the latest Permian, while the Early-Middle Triassic foreland basin underwent a negative basin inversion during the Late Triassic. The latter initiated a new sedimentary filling cycle of the Qiangtang Basin, which was triggered by the active extensional rifting and the onset of the bimodal volcanic eruption. Recent scientific exploratory drilling (QK-1 well) found that the Qiangtang Basin is characterized by multiple source rocks, of which the upper Triassic Bagong Formation and the lower Quse Formation exhibit the most hydrocarbon generation potential. The development of high quality and quantity source rocks in the Qiangtang Basin is ensured by regional to global-scale bottom-water anoxia and high primary productivity in the eastern Tethys realm in the Late Triassic and the Early Jurassic. The main reservoirs in the Qiangtang Basin include the Middle Jurassic reef-beach facies, the Upper Triassic carbonates, and the Lower Jurassic terrestrial clastic rocks. Two very-thick caprocks of gypsum in the Lower Jurassic and gypsum mudstones in the Middle Jurassic strata are found during the scientific drilling, which is interpreted as favorable regional-scale seals for petroleum entrapment in the Qiangtang Basin. [ABSTRACT FROM AUTHOR]

[Display omitted] • Au, Ag, Te in pyrite of the auriferous veins occur in micron-sized mineral inclusions. • Te melt is a key scavenger of Au from ore-forming fluids in the Yangwuchang deposit. • The ore-forming metals should be derived from a W-Au-rich magma system. • It has great W exploration potential at the deep part of magmatic type Au deposits. The co-mineralization of W and Au in some deposits has long been noted, yet remains debated. The Yangwuchang W-Au deposit provides an excellent opportunity for examining the genetic relationship between the mineralization of these two elements. In this paper, we present new trace elemental data for pyrite and sulfur isotopic compositions for sulfide minerals to better understand the co-mineralization of W and Au. Type 1 pyrite (Py1) is mainly hosted in the W-bearing veins and has low concentrations of Au (0.01–0.04 ppm), Ag (0.06–437 ppm), and Te (1.77–234 ppm). In contrast, type 2 Pyrite (Py2) in the auriferous veins is relatively enriched in Au (0.06–209 ppm), Ag (0.44–58610 ppm), Te (1.88–42337 ppm), and other trace elements. The concentration of Au has a positive relationship with Te but not with As, suggesting Te melt plays a significant role in scavenging Au from ore-forming fluids during mineralization. The narrow range of δ34S value (-3.17 to 3.69 ‰), combined with high Te contents and Co/Ni ratios of pyrite, indicates that the ore-forming metals may have been derived from a W-Au-rich magma. The slight negative values of δ34S in Py1 infer the localized pressure fluctuations during W mineralization. We concluded the W and Au could be both derived from one single magma system. The deep part of Au-bearing veins has great exploration potential for W mineralization. [ABSTRACT FROM AUTHOR]

[Display omitted] • The activity of depression-controlling fault controlled source rock thickness and distribution. • The preservation environment and organic matter supply controlled the quality of source rocks. • The accumulation mechanism of source rocks changed with tectonic activity and climate evolution. Lacustrine source rocks have a significant oil potential and contribute to 95 % of oil reserves in China's offshore areas, Nature of these rocks is related to climate and structure and they are commonly heterogeneous. Mechanism of organic matter accumulation in these rocks has been a matter of debate. Based on Rock-Eval pyrolysis, organic petrographic examinations, gas chromatography-mass spectrometry (GC–MS) analysis, and trace elements analysis, this paper illustrates the paleoclimate, tectonic activity, paleo-productivity, and preservation conditions recorded in high-quality source rocks of the Shanan Sag. The aim is to understand the controlling factors on the deposition of these source rocks. The results indicated that the organic matter of source rocks in middle segment of the third member of the Shahejie Formation (Es 3 m) was mainly from phytoplankton (average content = 52.2 %), the development of source rocks was controlled by high paleo-productivity. The primary productivity was low during the period of the first and second members of the Shahejie Formation (Es 1-2), and the high gammacerane index, and low Pr/Ph ratios indicated that the source rocks were mostly controlled by a good reduction environment with high salinity. The source rocks of the third member of the Dongying Formation (Ed 3) were characterized by high terrestrial materials (average exinite content = 62 %) and low to moderate Pr/Ph ratios, which indicated the source rocks were affected by both paleo-productivity and preservation environment. A productivity-controlling model in Es 3 m was established along with a co-controlling model of productivity and preservation in Ed 3 , which was largely developed under the background of a warm-humid climate and strong depression-controlled fault activity. The development model of source rock in Es 1-2 can be concluded as a preservation model under a hot arid climate and weak fault activity. The development model of source rock in Es 1-2 can be concluded as a preservation model under a hot arid climate and weak fault activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • The distribution of high production wells is related to the strike-slip fault zones. • Strike-slip faults provided a place for the development and alteration of reservoirs. • Four enrichment models were established through strike-slip faults and production characteristics. • Fault size, tension segment and structural highs affected the reservoirs. Uplifiting of the central Tarim Basin has attracted great interests since the discovery of a major condensed natural gas field in Ordovician carbonate successions at a depth of > 6000 m. The formation of the large-scale hydrocarbon reservoirs in reef shoals is typically thought to be influenced by paragenetic accumulation in the karstified reservoirs. However, because of the rapid decline of natural gas/petroleum production and the complex fluid distribution in limestone reservoirs, it is difficult to clarify the controlling factors of hydrocarbon enrichment. We integrate core, seismic, well logging and production data to illustrate the relationship hydrocarbon enrichment and fault system in this paper. First, productive wells are closely associated with major strike-slip fault zones. Second, most productive blocks are distributed in a banded or block-like manner within strike-slip fault sections. Third, strike-slip fault systems do not closely control reservoir quality; however, the enrichment of natural gas is linked to the development of strike-slip fault systems. Finally, all high-productivity wells are distributed around structural highs in major strike-slip fault zones. These lines of evidence suggest that the accumulation and enrichment of hydrocarbons were closely related to strike-slip fault zones rather than kastified reservoirs. Based on this, four models for the accumulation of hydrocarbons were proposed: fault uplift, graben periphery, fault intersection and fault–karst coupling. Large-scale strike-slip fault zones, transtensional segments and local structural highs were the main factors found to be controlling hydrocarbon enrichment and high productivity. Therefore, these three conditions improved the reservoir and provided paths and places for hydrocarbon migration and accumulation. These proposed hydrocarbon accumulation models contribute to a better understanding of these fault systems and further petroleum exploration. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Tarim Craton experienced both active and passive rifting during the Cryogenian. • The rift system shows a two-tiered architecture with narrow-deep Cryogenian grabens overlain by a broad Ediacaran depression. • Both active and passive rifting are thought to have been triggered by retreating subduction in the late Neoproterozoic. The Cryogenian-early Paleozoic succession in the Tarim Craton is generally regarded as a continuous rift sequence that followed the prolonged superplume-related breakup of Rodinia. However, the rift architecture and origin of the late Neoproterozoic basin are poorly known, but these are important for the understanding of the tectonic evolution of the basin and for the evaluation of the hydrocarbon potential. This paper aims to elucidate the rift architecture, distribution, origin and evolution of the late Neoproterozoic Tarim Basin by integrating outcrop investigations with well and seismic data. The late Neoproterozoic magma-rich active rifting primarily occurred in the northeastern part of the basin, whereas other areas experienced slightly younger magma-poor passive rifting. The Ediacaran succession overlaps in the northern basement uplift to show a pre-Ediacaran unconformity occurs in the northern Tarim Craton, while a sub-Cambrian unconformity traverses the entire Tarim Craton and presents a distinct truncation in the southern basement uplift. A tiered architecture exists in which narrow, deep Cryogenian grabens are overlain by a broad Ediacaran depression. Two NE-striking rift systems developed in the northeastern and southwestern Tarim. It can be inferred from the compiled data that the late Neoproterozoic rift basin evolution in the Tarim Craton can be divided into four stages: early Cryogenian rifting, late Cryogenian fault-graben, Ediacaran intracratonic depression, and end-Ediacaran regional uplifting. These results suggest that documented Neoproterozoic retreating subduction-related slab failure/detachment processes led to both active and passive rifting, which contributed to the diverse continental rift architecture and evolution of the late Neoproterozoic Tarim Basin. [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] • In-situ elemental analyses of Fe (oxyhydr)oxides from Zhijin distinguish two types of Fe (oxyhydr)oxides. • Fe-(oxyhydr)oxides showed mainly hydrogenic origin mixed with hydrothermal origin. • Fe (oxyhydr)oxides control the enrichment of REE in francolites via Fe-redox pumping. • REEs were adsorbed by Fe (oxyhydr)oxides in oxic seawater and released in suboxic/anoxic porewaters. Marine phosphorites have shown extraordinary REE potential. Enrichment mechanisms have been investigated as yet, however, the roles of Fe/Mn (oxyhydr)oxides in REE enrichment were poorly known. In this paper, we report new data for early Cambrian phosphorites in South China with a particular focus on REE enrichment and Fe-redox cycling. Phosphorites from the Cambrian Gezhongwu occur in the upper and lower units. The phosphorites contain a large number of of Fe (oxyhydr)oxides, especially those in the upper unit. SEM and laser Raman show that Fe (oxyhydr)oxides have a gray rim and a bright core, attributed to transformation from hematite to goethite during the weathering. In-situ elemental analyses show Fe (oxyhydr)oxides have PAAS-normalized REE patterns depleted in LREE and enriched in HREE with negative to positive Eu anomalies and positive Y anomalies. However, two patterns are clearly distinguished according to Ce anomalies and these are related to the origins of Fe-(oxyhydr)oxides: hydrothermal Fe (oxyhydr)oxides with negative Ce anomalies and hydrogenic ones with positive Ce anomalies. The role of Fe (oxyhydr)oxides played in REE enrichment was controlled by Fe-redox pumping. In this process, Fe (oxyhydr)oxides adsorbed REEs in oxic water columns; after precipitating to suboxic/anoxic conditions, the absorbed REEs were released into porewater. Francolites subsequently formed and captured REEs during early diagenesis. Even though additional evidence is required, our investigations were significant in conforming the origins of Fe/Mn (oxyhydr)oxides and their role in REE enrichment in marine phosphorites. [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]

[Display omitted] • Neoproterozoic adakitic granodiorites, gabbro-diorites and high-K granites in South China. • The western Yangtze Block was an arc belt related to the oceanic slab subduction during the Neoproterozic. • The Neoproterozoic magmatism was triggered in an oceanic slab window in the western Yangtze Block. Neoproterozoic igneous rocks are widespread along the margins of the Yangtze Block and record key information on the tectonic evolution of the South China Craton. In this paper, we present a comprehensive study of zircon U-Pb ages, whole-rock geochemistry and Sr-Nd-Hf isotopes on the Neoproterozoic granodiorites, gabbro-diorites, and high-K granites in the western Yangtze Block. The granodiorites, gabbro-diorites and high-K granites were dated at 848 ± 5.3 Ma, 824 ± 5.1 Ma and 819 ± 1.5 Ma, respectively. The granodiorites have high Sr (567 ∼ 607 ppm) contents and Sr/Y (84.4 ∼ 88.0) ratios and low alkalis (Na 2 O + K 2 O = 4.3 ∼ 4.9 wt%) and Y (6.6 ∼ 7.1 ppm) and Yb (0.7 ∼ 0.9 ppm) contents, similar to typical adakitic rocks. They show low MgO (0.9 ∼ 1.3 wt%), Cr (15.2 ∼ 26.7 ppm) and Ni (3.6 ∼ 4.4 ppm) contents and positive ε Nd(t) (+1.7 to + 4.2) and ε Hf(t) (+3.0 to + 8.2) values. The parental magmas for granodiorites were generated by partial melting of thickened juvenile mafic lower crust. The gabbro-diorites are characterized by the enrichment in LREEs, significantly negative Nb, Ta and Ti anomalies, and positive ε Nd(t) (+2.2 to + 4.2) and ε Hf(t) (+5.8 to + 10.4) values. They are inferred to be derived from partial melting of lithospheric mantle modified by subduction-related fluids. The high-K granites display high Zr + Nb + Ce + Y (208 ∼ 366 ppm) and alkali (Na 2 O + K 2 O = 7.6 ∼ 8.4 wt%) contents, high 10000*Ga/Al (2.31 ∼ 2.64) ratios and zircon saturation temperatures, similar to A-type granites. We suggest that these granites were formed by the partial melting of felsic crustal materials under low pressure and high temperature conditions. The association of granodiorites, gabbro-diorites and high-K granites indicates Neoproterozoic oceanic slab subduction in the western Yangtze Block. We suggest that a subducting oceanic slab window can account for Neoproterozoic magmatism in the western Yangtze Block. [ABSTRACT FROM AUTHOR]

[Display omitted] • A rapid cooling/exhumation event occurred in the Changle-Nan'ao Belt during the period from 80 to 70 Ma. • The Changle–Nan'ao Belt behaved as a single tectonic unit since 70 Ma. • Rifting started in the southwestern East China Sea and propagated southwards to the northeastern and then northwestern South China Sea during the Late Cretaceous-Paleogene. The East China Sea Basin is an ideal area for studying the subduction processes linked with this section of the active West Pacific continental margin. The initial rift time associated with the opening of the East China Sea Basin remains strongly controversial. This paper provides a perspective based on the apatite and zircon fission-track analyses of the Changle–Nan'ao Belt, located on the coastal mainland of eastern China. The results reveal a period of rapid exhumation of this belt, trending from 86 Ma in the north to ∼66 Ma in the south. From ∼66 Ma until the present exhumation was very slow. The data and their thermal history modeling results imply that the initial rift time of the East China Sea Basin most likely occurred at 80 – 70 Ma. The younging trend observed from the north to the south of the study area continues along the coastal margin to the northwestern margin of the South China Sea. This suggests the presence of a diachronous rift opening from the southwestern East China Sea during the Late Cretaceous southwards, and to the northwestern South China Sea during the Late Cretaceous – Paleogene. The rapid exhumation is coincident with the rapid decrease in plate velocity of the Izanagi Plate, Pacific Plate, and Neo-Tethyan and Indian Plate during the Late Cretaceous–Paleogene. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sedimentary provenances in the North Yellow Sea Basin changed in the Middle Jurassic – Early Cretaceous. • The change of sedimentary provenance was associated with the transition from compressive to extensional tectonic setting. • The transformation of tectonic regime was completed in the Early Cretaceous. During the Mesozoic, the Eastern North China Craton experienced a transformation from the compressive to extensional tectonic setting. The Middle Jurassic-Lower Cretaceous sedimentary rocks of the North Yellow Sea Basin in the Eastern North China Craton may contain information about possible changes of sources of sediments. Based on the detrital zircon U-Pb ages of sedimentary rocks and the statistics of detritus of clastic rocks, this paper deal with the provenances of these rocks from the Middle Jurassic-Early Cretaceous in the North Yellow Sea Basin. The Middle Jurassic detritus of clastic rocks were from the basement of the basin and the Sulu Orogenic Belt in the Jiaodong Peninsula. In the Late Jurassic, the detrital particles from the Jiaobei Uplift and Sulu Orogenic Belt increased, and the detritus of clastic rocks from the Liaodong Peninsula also flowed into the basin. In the Early Cretaceous, the detritus of clastic rocks from the Jiaodong Peninsula decreased, while detritus of clastic rocks from the Liaodong Peninsula dominated. The provenances of the Middle-Upper Jurassic sedimentary rocks in the basin were controlled by multiple directions, while the provenance of the Lower Cretaceous sedimentary rocks changed from multiple directions to single direction. Obviously, with the passage of time (from Middle Jurassic to Early Cretaceous), the spatial transformation of the provenances in the North Yellow Sea Basin was a response to the transformation of regional tectonic setting. In the Early Cretaceous, the Eastern North China Craton completed transformation from the Paleo-Asian tectonic domain to the marginal Pacific tectonic domain. [ABSTRACT FROM AUTHOR]

[Display omitted] • The magnetotelluric imaging of the southernmost segment of the Tanlu fault zone reveals the occurrence and extension direction of this zone. • The resistivity model shows that the Tanlu fault zone terminates at the southeast end of the Dabie orogenic belt and does not extend further to the south. • The Tanlu fault zone cannot extend further to the south due to the high-resistivity rigid crust of the South China Block. • A new model is proposed for the origin of the Tanlu fault zone. The Tanlu Fault Zone (TLFZ) is an important tectonic boundary in eastern China , and its deep structure, formation and evolution have always been the focus of earth science research. However, there is still much debate about its southward extension and formation pattern. The research on the deep structure at the southernmost end of the TLFZ is of great significance to the interpretation of these problems. This paper analyzes the magnetotelluric (MT) data at the southeast end of the Dabie orogenic belt (DOB), providing evidence for the deep structure in this area. Three MT profiles extend southwards from the south of the DOB, pass through the TLFZ, Xiangfan-Guangji fault (XGF) and Yangxin-Changzhou fault (YCF), and then reach the Jiangnan uplift (JNU). The two dimensional and three dimensional inversion of the MT data were conducted using a nonlinear conjugate gradient method, and the electrical structure images of the profiles above -60 km were obtained. The results showed that the depth of the TLFZ was about 30 km, reaching the lower crust. Its scale reduced significantly from the north to the south, not extending southwards, but westwards connecting with the XGF. It was also found that the lithospheric thickness at the northern margin of the Yangtze Block (YZB) increased significantly due to the Indosinian collisional orogeny. The connection between the TLFZ and XGF as well as the thick and high resistivity rigid lithosphere at the northern margin of the YZB effectively limited the southward extension of the TLFZ. The TLFZ stopped extending southwards at the southeast end of the DOB. With it as a fulcrum, the blocks on the eastern side of the TLFZ rapidly moved northwards during the Early Cretaceous, resulting in counterclockwise rotation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Constraints from fusulinids for the paleogeography of Changning-Menglian Belt, China. • New collections of late Carboniferous to Early Permian fusulinids from two sections. • Similar but less diverse by statistical comparison (Rarefaction) with South China. • Seamount atoll between peri -Gondwana and Cathaysia plausible for these carbonates. The Changning-Menglian Belt in western Yunnan, China, is a critical tectonic zone that preserves remnants of the Paleotethys Ocean, including limestones of possible seamount origin. Fusulinids, sensitive indices for age and paleoenvironment, are abundant in these limestones but have rarely been the subject of taxonomic study. This paper presents new fusulinid collections of middle Kasimovian (Late Carboniferous) to Artinskian (Early Permian) age from two sections located in the middle and northern parts of this belt. In the Mangyang Section, the fusulinids are grouped into the Triticites abundance zone and the Sphaeroschwagerina sphaerica range zone, while in the Anxincao Section, they comprise the S. sphaerica range zone, the Eoparafusulina interval zone and the Chalaroschwagerina solita range zone. The distinct Cathaysian affinity is indicated by the dominance of Triticites in the Late Carboniferous and Early Permian assemblages characterized by Sphaeroschwagerina, Eoparafusulina and Chalaroschwagerina. On the other hand, these fusulinids contrast sharply with coeval fusulinids in the peri -Gondwana region, which are impoverished and dominated by Eoparafusulina / Pseudofusulina. However, Early Permian fusulinids in this belt still differ from their counterparts in Cathaysian South China in terms of 1) lower diversity, as confirmed by a robust quantitative comparison (Rarefaction analysis); 2) peculiar rarity of Pseudoschwagerina. Collectively, these data imply that the studied fusulinids probably colonized marine environments far from the mid-latitude peri -Gondwana region, while detached from equatorial South China. This interpretation is consistent with the previous view that these limestones were formed on seamount atolls within the vast Paleotethys Ocean. [ABSTRACT FROM AUTHOR]

• A first quantitative study of Wuchiapingian plant-insect interactions from Cathaysia. • Nineteen damage types grouped to six functional feeding groups were identified. • Herbivore arthropods preferred the relatively abundant and more apparent foliage. • Local provincialism of plant–arthropod associations existed in Lopingian Cathaysia. • Margin-feeding culprits were one of the dominant herbivores in the Permian floras. The Permian is a pivotal time interval for the evolution of the terrestrial realm while the evolutionary dynamics of both floral and faunal turnover are poorly understood. Fossil evidence of plant–arthropod associations allows us to explore these confusions. In this paper, plant–arthropod interactions from the Wuchiapingian Qinglong plant assemblage in southwestern China are analysed. Fifty-one damage occurrences attributed to 19 damage types (DTs) from six functional feeding groups were recognised, consisting of hole feeding, margin feeding, surface feeding, piercing-and-sucking, oviposition, and galling. Although broadleaved gigantopterid laminae were less abundant than strap-shaped taeniopterid foliage, the former had more DT richness as well as DT frequency (occurrences based on presence-absence data) than those of the latter, indicating that herbivorous arthropods preferentially targeted broadleaved gigantopterid foliage and providing additional support for the apparency hypothesis. To explore the evolutionary dynamics of Permian plant–arthropod associations, data of DT community composition in the Qinglong and seven other Permian assemblages were analyzed using principal component analysis (PCA) and rank-abundance curve (RAC). PCA result shows that the Qinglong plant–arthropod associations displayed a damage-type spectrum with minimal affinity to those in the South China Kayitou and other assemblages, indicating that there was no compositional similarity of plant–arthropod associations in the Qinglong and other ecosystems. This pattern is probably related to different climatic zonation which resulted in local provincialism of plant–arthropod associations. RAC result shows that margin feeding was the dominant feeding modes during the Permian, suggesting there were a relatively high richness of margin-feeding culprits in these ecosystems. [ABSTRACT FROM AUTHOR]

[Display omitted] • Depleted continental mantles occur with different mineral chemistry and occurrence. • Mafic dikes were formed from melts via low-degree melting of asthenosphere mantles. • Orthopyroxenites were formed from reaction between SiO 2 -rich melts and peridotites. • Ophiolites were formed in a continental margin that was related to the Meso-Tethys. Whether the ophiolites in the southeast margin of the Gaoligong tectonic belt are related to subduction or rift is hotly debated. The aim of this paper is to present the geological and geochemical data of these ophiolitic blocks in order to understand the significance of these in the tectonic evolution of the Meso–Tethys. The peridotites in the ophiolites are dominantly harzburgites with high Mg# (88.7–92.2) and low Al 2 O 3 (<0.8 wt%) and CaO (<0.5 wt%) contents, and display U-shape chondrite-normalized rare-earth element patterns. However, they show two different groups of mineral chemistries and occurrences. Group I are with olivine Fo 90.6–92.3, orthopyroxene Mg# 91.0–92.6, clinopyroxene Mg# 91.1–93.3, and spinel Cr# 42.1–67.4 and Mg# 62.8–71.6. They exhumed adiabatically and were intruded by mafic dikes from the melts through low-degree melting of asthenospheric mantles and by orthopyroxenites in the Early Jurassic. Group II are with olivine Fo 89.8–95.3, orthopyroxene Mg# 91.3–94.6, and spinel Cr# 62.4–94.1 and Mg# 19.5–51.0. They underwent brittle deformation and medium- to low-temperature fluid replacement. The two group's peridotites have experienced the similar partial melting degrees and are the fragments of subcontinental lithospheric mantles. Extensive continental affinity tholeiites erupted in the Middle Jurassic, coeval with the primary spreading time of the Bangonghu–Nujiang Ocean in the central Tibet. The peridotites, mafic rocks, and marine-facies sediments represent the opening products of the Meso–Tethys in the Jurassic as ophiolites in a continental margin. [ABSTRACT FROM AUTHOR]

[Display omitted] • Late Neoproterozoic ophiolite fragments were discovered in the Irshi area. • The early Paleozoic crust of the middle Great Xing'an Range is an orogenic belt. • Neoproterozoic–early Paleozoic lateral crustal growth occurred in the eastern CAOB. The tectonic affinity of the middle segment of the Great Xing'an Range (GXR) in NE China has become one of the focus issues about the Paleozoic crustal division and tectonic evolution of the eastern segment of the Central Asian Orogenic Belt. In this paper, we identified some ophiolite fragments from the early Paleozoic strata in the Irshi area of the middle segment of the GXR, which was previously thought to be the interior of the Precambrian Xing'an block. These ophiolite fragments and the surrounding deformed clastic rocks together constitute the Irshi ophiolite mélange (IOM). Zircon U-Pb dating reveals that the ophiolites formed during 603–608 Ma, which indicates that there was an oceanic basin during the late Neoproterozoic. The geochemical composition suggests that the ophiolites were formed in a back-arc setting. The youngest group of detrital zircons in the matrix ranges from 435 Ma to 480 Ma. In addition, the IOM was covered unconformably by late Silurian and Devonian strata, and it was thus likely emplaced during the early–middle Silurian. The identification of the IOM eliminated the possibility that the middle segment of the GXR was an independent Precambrian continental block. The spatial–temporal distribution of Proterozoic–early Paleozoic ophiolite, metamorphic complexes, and magmatic and sedimentary rocks in the middle segments of the GXR indicates that the tectonic affinity of the late Neoproterozoic–early Paleozoic crust in this area is an accretionary orogenic belt. The continuous subduction of the Paleo-Asian Ocean was responsible for the formation of the orogenic belt. [ABSTRACT FROM AUTHOR]

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]

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]

• We propose a method combining neural network and transfer learning for China. • This method has better performance on PGA and PGV prediction than baseline models. • Robust on-site instrumental intensity prediction at 3 s after P-wave arrival. • High percentage of successful alarms for the area nearby the epicenter. China is a seismically active country. Rapidly and accurately predicting instrumental seismic intensity at recording sites is important for China to mitigate earthquake disasters. According to the peak ground acceleration (PGA) and peak ground velocity (PGV) at recording stations, instrumental seismic intensity for China is measured. Here, for the robust and rapid on-site instrumental seismic intensity prediction, we propose a method combining recurrent neural network (RNN) and transfer learning to predict on-site PGA and PGV for China. For the same test dataset from China, our results indicate that at 3 s after P-wave arrival, the RNN models using transfer learning have better performance on PGA and PGV prediction than the baseline models, which include traditional methods based on the single parameter and RNN models without using transfer learning. Additionally, according to the predicted PGA and PGV of the RNN models using transfer learning, we statistically analyze the alarm performance based on the predicted on-site instrumental seismic intensity. Meanwhile, according to the proposed method in this paper, we test five destructive earthquake events (M ≥ 6.6) occurred in China. The results show that at 3 s after the P-wave arrival, the predicted instrumental seismic intensity is almost consistent with the observed instrumental seismic intensity, the predicted instrumental seismic intensity error is mainly within ± 1, and the mean absolute error is 0.78. Meanwhile, for the area near the epicenter, the percentage of successful alarms reaches 90%, and the percentage of false alarms is 0%. [ABSTRACT FROM AUTHOR]

[Display omitted] • The connectivity of shales can be estimated effectively based on percolation theory through analyzing sorption hysteresis. • The connectivity of shales is mainly influenced by the TOC content. • The maturity and illite content are controlling factors for the percolation cluster length of shales. Pore connectivity is a key parameter affecting the hydrocarbon yield of shale reservoirs, and a quantitative study on it is helpful to evaluate the exploration and development potential of shale gas. In this paper, the shales from the Jurassic Yangxia and Kezilenur Formations in the Kuqa Depression, Tarim Basin, China, were taken as an example, and organic petrography analysis, X-ray diffraction analysis, field emission scanning electron microscope (FE-SEM), gas adsorption and helium pycnometry were carried out to determine their petrological, organic geochemical characteristics and pore distribution features. A method for estimating the connectivity of shale with isotherm adsorption curves of a H3 hysteresis loop was established and used to characterize the connectivity of shale pores. The results show that the total pore volume of shale ranges from 2.479 × 10-3 to 20.379 × 10-3 cm3/g, and the specific surface area (SSA) ranges from 1.222 cm2/g to 12.668 cm2/g. The samples' coordination number (Z) is between 1.215 and 3.064, and the percolation cluster length (L) is between 2.429 and 3.859. Shale with more micropores or higher TOC has a larger Z value, indicating that organic matter pores and micropores have better connectivity. There is no correlation between Z and T max , meaning that the effect of maturity on Z is insignificant. The impact of TOC on the L value is also not substantial. Besides, T max and illite content show a negative correlation with L, indicating that the high maturity and illite content impede the development of the percolation cluster. [ABSTRACT FROM AUTHOR]

• The sedimentary environment transitioned from clastic shore-shelf of the lower Ediacaran to carbonate platform to mixed shelf of the upper Ediacaran except for the glaciogenic Hangelchaok Formation. • The Ediacaran slop break belt was first identified along the west and south margins of the Manjar sag. • High-quality source rocks and karstic dolostone in Ediacaran indicate great potential for hydrocarbon exploration. The Late Neoproterozoic was an important period for the breakup of Rodinia and the assembly of Gondwana. The Neoproterozoic succession developed under the extensional setting is critical for understanding the early tectono-sedimentary evolution of the Tarim Basin and possibly exhibits considerable hydrocarbon potential. In this paper, the stratigraphic correlation of the Ediacaran is conducted across the whole Tarim Basin, based on the latest wells, seismic data and field investigations. The paleogeographic distribution and hydrocarbon potential of the Ediacaran are thoroughly discussed. The Lower Ediacaran succession is mainly distributed in northern and southwestern Tarim Basin and marginal outcrop areas, but absent in the whole Central Rise. With sea level rising, the Upper Ediacaran succession gradually moved toward Central Rise with the exception of the Tazhong Uplift and the eastern Bachu Uplift. During Early Ediacaran, depositional environment in the Tarim Basin was mainly clastic shore-shelf, with a large denuded region extending from Bachu-Tazhong Uplift to Tadong Uplift. The range of the erosional area gradually diminished during Late Ediacaran. Accordingly, the Tarim Basin was dominated by carbonate platform and mixed shelf. Slope break belt between carbonate platform and mixed shelf was identified around the Manjar sag for the first time. The Ediacaran black mudstone and shale in northeastern and southwestern Tarim, which formed in deep-water environment and have relatively high values of TOC (mostly ranging from 0.3% to 1.2%), can serve as high-quality source rocks. The Upper Ediacaran dolostones altered by paleokarst could be potential reservoir rocks. Our research findings, combining with previous geological results, suggest that the Ediacaran succession in Tarim Basin has great potential for hydrocarbon exploration. [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]

[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]

[Display omitted] • Triassic medium-grade metamorphism is recognized in Hainan Island, the eastern Paleo-Tethyan tectonic domain. • Amphibolite-facies metamorphism of the Mulantou Metamorphic Complex took place at ca. 250–235 Ma. • Peak metamorphic conditions reached 717–771 °C and 4.4–5.8 kbar, equivalent to a geothermal gradient of approximately 30 °C/km. • Mulantou Triassic amphibolite facies metamorphism resulted from collision between the South China and Indochina blocks after closure of the Paleo-Tethys. The Permian-Triassic tectonic evolution of Southeast Asia has long been a subject of considerable debate. Hainan Island in China is located at the junction of the South China and Indochina blocks adjacent to the Pacific (Philippine) Plate. Studies of metamorphic complexes in Hainan Island may shed lights on the Permian-Triassic tectono-thermal events of the eastern Paleo-Tethys. Among these complexes, the newly recognized Mulantou Metamorphic Complex is sporadically exposed in northeastern Hainan Island provides evidence for above-mentioned issues. In this paper, we present the result of a combined petrological and geochronological study of paragneisses in this complex. The paragneisses consist mainly of biotite, plagioclase, quartz, and rutile/ilmenite, with or without garnet, sillimanite, and muscovite. Textural relationships, mineral compositions, and thermobarometric calculations show that these paragneisses record peak metamorphic P − T conditions of 720–770 ℃ and 4.4–5.8 kbar. Zircon and monazite U − Pb dating by laser ablation–inductively coupled plasma–mass spectrometry indicates that metamorphism occurred at 250–235 Ma. Integrating published geochronological, geochemical, and structural data of Hainan Island and along the Jinshajiang − Ailaoshan − Song Ma suture zone, we infer that the Triassic amphibolite-facies metamorphism of the Mulantou Metamorphic Complex resulted from collision between the South China and Indochina blocks after closure of the Paleo-Tethys. [ABSTRACT FROM AUTHOR]

• First documentation of the Pagoda Positive Carbon Excursion (PPCE) on Upper Yangtze Platform. • Astronomical tuning of 3 sections yielded similar PPCE durations of 4.0 ± 0.3 Myr. • PPCE is coeval with regional transgression-highstand and oscillating climate. The continuous and well exposed sections of the Upper Ordovician on the Upper Yangtze Platform were surveyed and sampled for δ13C and δ18O isotope and conodont fossils. The geochem-stratigraphic work in the Pagoda Formation has resulted in the recognition of a positive δ13C excursion, the Pagoda Positive δ13C Excursion (PPCE). The PPCE is a distinctive positive excursion occurring in the Middle-Late Katian, consists of three minor excursions ranging from 1.5 ‰ to 3 ‰, which has been identified in all the study sections on the Upper Yangtze Platform. The PPCE interval ranges through the conodont Hamarodus brevirameus and Protopandeordus inscrulptus conodont zones in ascending order, which indicates that the PPCE develops in the Middle-Late Katian of the Late Ordovician, while the Guttenberg δ13C Excursion (GICE) in the Baltoscandia and America extended from the Late Sandbian to the Early Katian. Spectral analysis of high-resolution magnetic susceptibility (MS) logs for the four study sections shows consistent wavelengths of ca. 2.0, 0.5, 0.18 and 0.15 m. The outcrop depth-series were tuned using 405-kyr long-eccentricity cycles and the astronomical tuning yields the duration of 3.7 to 4.4 myr for the PPCE event in different sections. This is the first documentation of the PPCE event on the Upper Yangtze Platform according to the geochemo-bio-cyclostratigraphy evidences, being identified within all portions of this platform in South China. It revised the previous description of the positive δ13C excursion of the Pagoda Formation on the Upper Yangtze Platform. The trigger of the PPCE was also briefly discussed in this paper. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Alubaogeshan intrusion formed at ca. 134 Ma and belongs to transitional I–A 2 -type granite. • The Alubaogeshan intrusion was formed by partial melting of a Neoproterozoic juvenile crust. • The syenogranite porphyry evolved from the porphyritic monzogranite. • Fluid–melt interaction is crucial for W mineralization. • The magma evolutionary degree influences the size of the Sn–polymetallic deposits in the SGXR. The Alubaogeshan intrusion, consisting of porphyritic monzogranite in the central part and syenogranite porphyry in the edge, is genetically related to the Maodeng–Xiaogushan Sn–polymetallic deposit. This paper aims to investigate the genetic link between these two granite phases and the relationship between magma evolution and Sn mineralization. LA-ICP-MS zircon U–Pb dating of the porphyritic monzogranite and syenogranite porphyry yielded ages of 134 ± 1.0 Ma and 133 ± 0.5 Ma, respectively. The Alubaogeshan intrusion has high SiO 2 and total alkali (Na 2 O + K 2 O) contents, with low Al 2 O 3 , Fe 2 O 3 , FeO, and MgO contents, belonging to high-K calc-alkaline metaluminous–weakly peraluminous granites. Chondrite-normalized rare earth element (REE) patterns are characterized by light REE enrichment and heavy REE depletion, with extremely negative Eu anomalies. In addition, the intrusion was also enriched in Rb, Th, U, K, Zr, Hf, and light REE and strongly depleted in Ba, Sr, P, and Ti. Mineralogical and geochemical characteristics, together with high zircon saturation temperature, indicate that the Alubaogeshan intrusion belongs to transitional I–A 2 -type granites. Compared with the porphyritic monzogranite, the syenogranite porphyry reveals higher SiO 2 content and lower TiO 2 , Al 2 O 3 , Fe 2 O 3 , FeO, CaO, MgO, and P 2 O 5 contents, with more obvious negative anomalies of Eu, Ba, Sr, P, and Ti. The temporal and spatial relationship and geochemical characteristics of the two rocks indicate that the syenogranite porphyry evolved from the porphyritic monzogranite. The modeling results show that the fractional crystallization of amphibole, plagioclase, K-feldspar, biotite, apatite, monazite, and allanite occurred during the magma evolution. The granitic magma differentiation plays a key role in the formation of the Maodeng–Xiaogushan Sn–polymetallic deposit. The ε Hf (t) values of zircon range from 2.58 to 7.08, and the two-stage Hf model ages range from 619 Ma to 850 Ma, implying that the Alubaogeshan intrusion was predominantly derived from partial melting of a Neoproterozoic juvenile crust. The TE 1,3 values of the ore-related granites from W–(Sn) deposits are generally higher than 1.1, suggesting that fluid–melt interaction is crucial for W mineralization. The degree of magmatic evolution is one of the controlling factors for the size of Sn–polymetallic deposits in the southern Great Xing′an Range. [ABSTRACT FROM AUTHOR]

The age of the giant Uragen sandstone-hosted Pb-Zn deposit in the western margin of the Tarim Basin in Northwest China has long been questioned due to the general paucity of minerals unequivocally linked to Pb-Zn deposition that can be precisely dated using conventional radiogenic isotopic techniques. This paper describes the petrographic characteristics of Pb-Zn ores and presents the results of in situ calcite U–Pb analysis using laser ablation sector field inductively coupled plasma mass spectrometry (LA-ICP-MS) for this deposit. Calcite from the early, main and late ore-forming stages yielded low intercept ages of 11.80 ± 0.4 Ma, 10.9 ± 0.3 Ma and 10.6 ± 0.2 Ma, respectively, which constrain the Uragen Pb-Zn mineralization to the Late Miocene. Combined with the existing isotopic ages in the region, these new ages lead us to propose that the Uragen deposit formed during two hydrothermal episodes. The first refers to the oil-gas migration that occurred during the Middle Eocene to Early Miocene, which may be associated with the India–Eurasia collision and subsequent activity of the Main Pamir Thrust. The second refers to the Pb-Zn mineralization that occurred in the Late Miocene, which may be associated with the activity of the foreland thrust fault belt of South Tianshan and the Pamir Frontal Thrust (PFT). This study demonstrates the potential of using LA-ICP–MS U–Pb dating on calcite to constrain the ages of sandstone-hosted Pb-Zn deposits. [ABSTRACT FROM AUTHOR]

• A clockwise P–T path was established for Chachahe eclogites in North Qaidam UHP belt, NW China. • The Chachahe eclogites experienced a 1.92 Ga metamorphic event prior to eclogitization at ∼ 450 Ma. • Overriding plate material can enter subduction channel via tectonic erosion and be carried to mantle depths of ≥ 85 km. Although numerical modelling and marine seismic data show that overriding plate material can enter subduction channel and even recycle to mantle, and finally contribute to mantle heterogeneity and arc magmas, protoliths of the majority of high pressure (HP) and ultrahigh pressure (UHP) metamorphic rocks on the earth's surface originate from the subducting plate. Whether overriding plate material can enter subduction channel and their fate in subduction channel remain enigmas. The North Qaidam UHP Metamorphic Belt (NQUB), located in northwestern China, was formed by north-dipping subduction of the Qaidam Block beneath the Quanji block in the Early Paleozoic. In this paper, we report that some eclogites in Chachahe area, NQUB experienced a 1.92 Ga low-grade metamorphism prior to eclogitization at ∼ 450 Ma. This Paleoproterozoic metamorphic event is not reported in the subducted Qaidam Block but widespread in the overriding Quanji Block, indicating that protoliths of Chachahe eclogites originated from the overriding plate. A clockwise P–T path from 12 kbar/520 °C to near UHP conditions of 25.5 kbar/690 °C, followed by isothermal decompression, was estimated for the Early Paleozoic metamorphism using a combination of garnet major and trace element zoning, phase equilibrium modelling and thermobarometry. This P–T path pattern is similar to other eclogites in this area, protoliths of which originated from the subducted plate. These results clearly show that overriding plate material can enter subduction channel and be carried to mantle depths of at least 85 km and exhume fast along subduction channel with other slices from subducted slab. [ABSTRACT FROM AUTHOR]

[Display omitted] • Clockwise P–T evolution is recorded by the South Altyn Tagh felsic gneiss. • The felsic gneiss was exhumed from eclogite-facies to granulite-facies within 20 Myr. • HP–HT eclogite-facies records were preserved in the weakly deformed felsic gneiss. • The HP mineralogical records were further eliminated by the strong deformation. Felsic gneisses are usually the dominant rock types in most high-pressure (HP) and ultrahigh-pressure (UHP) terranes, although their peak metamorphic conditions and complete P–T paths are rarely known. This lack of knowledge is attributed to the high variance of mineral assemblages at HP/UHP conditions of the felsic gneisses, or to the effects of retrograde-related overprinting. Thus, it is difficult to distinguish whether felsic gneisses underwent HP/UHP metamorphism. In this paper, we focus on the felsic gneiss that has been previously documented as having formed under HP granulite-facies metamorphism with peak P–T of > 1.15 GPa and > 860 °C from the Danshuiquan locality in the South Altyn HP – UHP belt. The Danshuiquan felsic gneiss is strongly deformed and is spatially associated with weakly deformed garnet-rich felsic gneiss. On the basis of detailed microstructure observations on mineral assemblages and phase equilibria modelling, three stages of metamorphic evolution for the weakly deformed garnet-rich felsic gneiss are identified. The first stage is represented by garnet cores, revealing a prograde P–T path from 1.5 GPa/750 °C to 2.1 GPa/900 °C. The second stage is characterized by garnet mantles with multiphase inclusions, defining HP eclogite-facies metamorphic conditions of 2.2–2.6 GPa/950–1100 °C. The third stage is represented by the composition of garnet rims, biotite, and plagioclase, suggesting an HP granulite to amphibolite facies decompression cooling process to 1.1–1.3 GPa/710–770 °C. In contrast, the strongly deformed felsic gneiss just records a deformation-related decompression process from 1.1 to 1.2 GPa/750–760 °C to 0.87–0.98 GPa/760–770 °C, and finally to 0.83 GPa/740 °C. Zircon U–Pb dating yields c. 920 Ma protolith ages, c. 500 Ma eclogite-facies ages, and c. 480 Ma granulite to amphibolite facies retrograde ages for the Danshuiquan felsic gneisses. Our results show that the Danshuiquan felsic gneisses underwent a similar metamorphic evolution process to that of Yinggelisayi HP–UHP rocks in the eastern segment of the South Altyn Tagh. Most HP mineralogical records tend to be eliminated by the strong deformation at crustal depths (∼30 km), meaning that the peak metamorphic conditions of the studied felsic rocks in UHP metamorphic terranes are previously underestimated. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Mikengshan-Qingxixiang-Yanbei igneous rocks were formed at 145–134 Ma. • The Yanbei Sn-bearing granite porphyries were derived from ancient crustal rocks. • Reduced redox state and ancient crustal sources benefit for Sn mineralization. A world-class Sn province in South China contains granite- and porphyry-related Sn deposits. In this paper, we investigate the source of Sn, based on a study of Early Cretaceous (145–134 Ma) ore-barren granites and granite porphyries, ore-barren rhyolites, and Sn-bearing granite porphyries in the Mikengshan (MKS)–Qingxixiang (QXX)–Yanbei (YB) area of South China. The ore-barren rhyolites have enriched whole-rock Nd and zircon Hf isotopic compositions [ε Nd (t) = − 9.1 to − 10.5; ε Hf (t) = − 5.9 to − 13.8]. The ore-barren granites and granite porphyries have A-type granite characteristics and less enriched Nd–Hf isotopic compositions [ε Nd (t) = − 4.9 to − 3.2; ε Hf (t) = − 6.0 to + 1.7] than the ore-barren rhyolites. The Sn-bearing granite porphyries have similar rare earth element and trace element patterns to the ore-barren rhyolites. In addition, they have similar Nd but less enriched Hf isotopic compositions [ε Nd (t) = − 8.9; ε Hf (t) = − 3.3 to + 0.4] compared with the ore-barren rhyolites. The average ΔFMQ values of the studied volcanic (–0.50) and intrusive (–0.21) rocks indicate reduced condition during magma evolution. We suggest that the ore-barren rhyolites were likely derived by partial melting of Paleoproterozoic to Mesoproterozoic crustal metasedimentary rocks and that the Sn-bearing granite porphyries were possibly formed by partial melting of Paleoproterozoic metasomatized mantle-derived crustal rocks. Whereas, the ore-barren granites and granite porphyries were likely generated by partial melting of a hybridized source consisting of ancient and late Mesozoic juvenile crustal rocks. We propose that the reduced redox state and ancient crustal sources played an important role for Sn mineralization in the MKS–QXX–YB area. [ABSTRACT FROM AUTHOR]

[Display omitted] • The shale gas resource potential of the Longmaxi Formation was evaluated by using mud gas isotope logging technology. • The reservoir properties of shale were evaluated based on gas isotope fractionation effects. • The shale gas in the Changning area belongs to late kerogen cracking gas. • The lower part of the Longmaxi Formation has a better shale gas exploration potential. The Longmaxi Formation in the Sichuan Basin is one of the most important shale gas producing formations in China. Previous studies of shale gas were mostly carried out on based on laboratory analyses and did not provide effective guidelines for shale gas exploration. In this paper, we present a large amount of carbon isotopic data from mud gas isotope logging and rock-cutting headspace gas in wellsites. The δ13C 1 values showed a significant decrease at the bottom of the Longmaxi Formation. The δ13C 1 and δ13C 2 values in the Changning area were observed to be heavier than those in the Weiyuan and Jiaoshiba areas. The second half of the N216H27-3 horizontal well had obvious outgassing and carbon isotope fractionation effects. This indicates that the bottom of the Longmaxi Formation has better shale gas exploration potential. The shale gas of the Longmaxi Formation in the Changning area belongs to late kerogen cracking gas, where exploration prospects are poorer than those in the Weiyuan and Jiaoshiba areas. There were more oil cracking gas resources and better reservoir conditions at the end of the N216H27-3 horizontal well; therefore, drilling should be continued at this site. [ABSTRACT FROM AUTHOR]

[Display omitted] • The depositional age of the Xiufeng Formation was estimated as 159 Ma. • The Mohe Formation has a bidirectional provenance from 150 Ma. • The tectonic setting transformed from compression to extension during 135–128 Ma. • A series of E-W and NE-SW-trending normal faults occurred since the Early Barremian. • The final closure of the Mongol-Okhotsk Ocean has been limited to 150–135 Ma. The Mohe basin is located to the south of the eastern Mongol–Okhotsk suture belt and contains critical stratigraphic records and thrust-nappe structures for understanding the closure of the eastern Mongol–Okhotsk Ocean. This paper discusses the formation ages, provenance, and tectonic setting of the Xiufeng and Mohe formations, and further reveals the timing of the final closure of the Mongol–Okhotsk Ocean and the tectonic evolution of the Mohe basin. The weighted mean 206Pb/238U ages for the youngest zircon of these samples indicate that the maximum depositional ages of the Xiufeng, Mohe and Tamulangou Formations were conservatively estimated at 159 Ma, 150 Ma and 128 Ma, respectively. From Late Triassic to Late Jurassic (150 Ma), the Mongol-Okhotsk Ocean was consumed by bidirectional subduction expressed by subduction under the Siberian Craton and the Erguna Block, respectively. The intense subduction led to the compression of the continental arc and the basement uplift of the Erguna Block, which provided abundant clastic sediments to the Xiufeng-Ershierzhan Formations. During the Late Jurassic-Valanginian (150–135 Ma), the Mongol-Okhotsk Ocean closed rapidly, which finally caused the collision between the Erguna Block and the Siberian Craton. Meanwhile, the southern margin of the Siberian Craton was uplifted and started furnishing sediments into the Mohe-Kaikukang Formations, which may have a bidirectional provenance. The subsequent crustal shortening associated with collision between the Erguna Block and the Siberian Craton led to nappe structures, syn‐collisional folds, and nearly N-S-trending reverse and oblique-slip faults occurred along the northwestern margin of the Mohe basin. Between 135 and 128 Ma, the Mohe basin entered the stage of tectonic setting transformation, which is the crucial period for the Mohe basin to transform from compression to extension. Since the Early Barremian (ca. 128 Ma), the compressional environment was transformed into a post-orogenic extensional tectonic environment, and a series of nearly E-W and NE-SW-trending normal faults occurred, which might have been controlled by the slab rollback of the Paleo-Pacific Plate and detachment of the Mongol-Okhotsk oceanic plate after the closure of the Mongol-Okhotsk Ocean. [ABSTRACT FROM AUTHOR]

[Display omitted] • Both granodiorites and monzogranites of the Mopanshan pluton are coeval and formed at ca. 820 Ma. • They were generated by mixing of metasomatized mantle-derived magmas and ancient crust-derived melts. • The adakitic signatures of the Mopanshan pluton were caused by hornblende-dominated fractional crystallization. • The Neoproterozoic magmatic event was due to the intensive crust-mantle interaction in a back-arc extension setting. Crust- and/or mantle-derived igneous rocks in the Neoproterozoic continental magmatic arc along the western Yangtze Block (South China) have been extensively studied, but the crust-mantle interaction that might have been involved in the formation of these rocks was poorly understood. In this paper, we present an integrated study on petrology, whole-rock compositions, in-situ plagioclase Sr and zircon U-Pb-Hf isotopes for granodiorites and monzogranites from the Neoproterozoic Mopanshan pluton in the western Yangtze Block. Our objective is to provide vital constraint on the magma mixing process in the formation of these rocks. The new LA-ICP-MS zircon U-Pb dating results reveal that both granodiorites and monzogranites of the Mopanshan pluton were coeval and formed at ca. 820 Ma. They are calc-alkaline to high-K calc-alkaline (SiO 2 = 66.06–70.30 wt%, K 2 O = 2.24–3.34 wt%) and metaluminous to slightly peraluminous (A/CNK = 0.99–1.10) rocks, and characterized by middle-upper crustal trace element patterns (e.g., enrichment in Rb, K, Th, U, and Pb, and depletion in Nb, Ta, Sr, and Ti). The magma mixing process is supported by following ample evidence, including (1) the disequilibrium mineral textures and an abruptly increased An values (up to 60) as well as significant decrease of (87Sr/86Sr) i ratios from core to rim in plagioclase crystals, (2) higher Mg# values (45–50 > 40) than those of experimental melts from basalts at the same silica contents, (3) positive and negative whole-rock εNd(t) (–0.72 to + 1.01) values as well as variable whole-rock (87Sr/86Sr) i (0.702778–0.705404) and zircon εHf(t) (+1.76 to + 7.72) values. The special geochemical characteristics and element modeling support that the Mopanshan pluton was generated by magma mixing of ancient crust-derived melts and relatively mafic melts from metasomatized mantle source. The adakitic signatures observed in the Mopanshan pluton were attributed to subsequent hornblende-dominant intra-crustal fractional crystallization, rather than derived from a thickened lower crust source. In combination with regional geology and our compilation for Nd-Hf isotopes of Neoproterozoic igneous rocks, the Mopanshan pluton is magmatic response of intensive crust-mantle interaction induced by underplating of voluminous mantle-derived magma in a back-arc extension setting. This research highlights that the crust-mantle interaction is significant for the petrological and geochemical diversity of Neoproterozoic granitoids from the western Yangtze Block. [ABSTRACT FROM AUTHOR]

[Display omitted] • In-situ Sr-Nd-O isotopic analyses of minerals are employed to constrain the nature of primary magmas in the Weishan syenite-(carbonatite) complex. • Both lithospheric and asthenospheric mantle have contributed to the generation of the Weishan complex. • Involvement of asthenosphere-derived components may play an important role in the enrichment of REE in the Weishan complex. Carbonatite-alkaline complexes are commonly derived from the mantle. However, whether the source is lithospheric or asthenospheric mantle remains debated. In order to better understand this issue, this paper conducts a Sr-Nd-O isotopic study on the Early Cretaceous, Weishan REE-rich syenite-(carbonatite) complex, Northern China. Two types of apatite are identified from the Weishan complex, namely magmatic and xenocrystic apatite. In-situ Sr-Nd isotopic analyses on magmatic apatite yielded (87Sr/86Sr) i from 0.70690 to 0.70719, and ε Nd (t) from −7.6 to −8.8. The pristine calcite from carbonatite has similar (87Sr/86Sr) i (0.70727–0.70739) with magmatic apatite. In-situ oxygen isotopic analyses on zircon yielded δ18O VSMOW (‰) from 5.9 to 6.7 ‰. Previous studies reveal that coeval, mantle lithosphere-derived rocks in the region have more enriched Sr (87Sr/86Sr i greater than 0.709) and Nd [ε Nd (t) 〈 −1 2] isotopes than the Weishan complex; whereas the asthenosphere-derived rocks in the region are characterized by depleted Sr-Nd isotopes (87Sr/86Sr i < 0.706; ε Nd (t) greater than 0) and low δ18O VSMOW values (mostly < 5.4 ‰). It is well known that Northern China experienced destruction in the Early Mesozoic, which was accompanied with asthenosphere upwelling along trans -lithosphere faults. Considering that the Weishan complex locates adjacent to the trans -lithosphere Tanlu fault, generation of the complex may be related to asthenosphere-lithosphere interaction. Notably, the Weishan complex differs from coeval REE-barren carbonatites in that its source involved asthenosphere-derived components; hence, involvement of asthenosphere-derived components may be important for the formation of such a REE-rich complex. In general, this study highlights the importance of lithosphere-asthenosphere interaction in supplying necessary heat and materials for the generation of the Weishan complex. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Ediacaran-Cambrian boundary interval at Pingyin in South China records a deepwater euxinia. • Expanded deepwater euxinia occurred in the Nanhua Basin during the Ediacaran-Cambrian transition. • The expanded deepwater euxinia probably resulted in the extinction of Ediacaran fauna. Global anoxia of shallow seawater during the Ediacaran–Cambrian (EC) transition has been interpreted as being caused by the upwelling of H 2 S-bearing deep seawater. This hypothesis implies the possible widespread occurrence of H 2 S-rich deep seawater during the EC transition. However, due to a lack of detailed investigation of environmental information recorded across the EC boundary (ECB) at deep-water facies sections, the occurrence of widespread H 2 S-rich deep seawater in paleo-basins during the EC transition is uncertain. The Pingyin section in South China is a deep-water-facies section for which the position of the ECB has been constrained by high-precision zircon chemical abrasion–isotope dilution–thermal ionization mass spectrometry U–Pb ages. Therefore, this section is a favourable site for obtaining information about deep seawater during the EC transition. In this paper, we present redox sensitive element (RSE) concentrations and Fe speciation of cherts from this section to study the redox condition of deep seawater recorded in the ECB at Pingyin. The results show dramatic differences of redox proxies in the cherts in the ECB from those underlying ones. The enrichment factors of U, V and Mo of the underlying samples are 2.08–6.89, 0.82–1.52 and 3.36–7.32, much lower than those of cherts in the ECB which are 16.52, 3.65 and 48.60, respectively. The underlying samples have Th/U ratios of 0.69–2.29, much higher than the cherts in the ECB with Th/U ratios of <0.30. The V/(V + Ni) ratios of most of the samples below the ECB are <0.84, whereas those of the samples at the ECB are >0.84. The Ce/Ce* values of the chert samples show an upward-decreasing trend below the ECB, but change to an increasing tendency immediately above the boundary. Almost all of the chert samples from the topmost Liuchapo Formation have Fe HR /Fe T ratios of >0.38. The Fe PY /Fe HR ratios of the samples underlying the ECB are lower than 0.80, whereas those of the samples around the ECB are higher than 0.80. These various indicators show that the ECB at Pingyin records an ancient deep-water redox turnover from anoxic ferruginous to sulphidic conditions. Combining the new findings with previous data, we conclude that the ECB in South China records the extensification of euxinia in deep water of the investigated paleo-basin. This event, which may have been global in extent, could have had a profound influence on early marine life and was likely a major cause of Ediacaran faunal extinction. [ABSTRACT FROM AUTHOR]

• Grain assemblages in shale establish a key starting condition for diagenetic pathway. • There are four origins of quartz and two origins of organic matter in marine shale. • Cementation and mechanical compaction make a significant reduction of porosity. • Shale with different lithfacies has differences in pore types. • Authigenic quartz cementation made porosity reduction but enhanced the brittleness. This paper considers possible impacts of mineralogy and organic matter contents and assemblages on the diagenetic history, pore structure, and brittleness of the Ordovician-Silurian Wufeng Formation and Longmaxi Formation (Northwestern Hunan, upper Yangtze Platform) of South China. Multiple analytical approaches, including X-ray diffraction, scanning electron microscopy, cathodoluminescence, and X-ray mapping, were utilized to identify favorable shale gas intervals. Analyzed shale samples of the Wufeng-Longmaxi succession are dominated by such extrabasinal components as quartz, K-feldspar, albite, lithic fragments, and K-rich and Mg-rich clay minerals. Subordinate components include siliceous tests and organic particles. Authigenic minerals present as grain replacements and pore-fillings include quartz, illite, pyrite, and carbonate minerals. Depositional and diagenetic organic matter, which are discriminated petrographically, are present in the studied deposits. Wufeng Formation samples are enriched in organic matter (mainly of diagenetic origin) and authigenic quartz. The dominant types of porosity of the Wufeng samples include pores hosted by organic particles and interparticle pores between authigenic quartz crystals. The precipitation of authigenic quartz appears to have been the principal means of porosity reduction and enhanced the brittleness of the shale. Analyzed samples of the Longmaxi Formation are dominated by extrabasinal grains and lesser authigenic minerals. Reduction of depositional porosity of these deposits appears to have been largely the result of physical compaction. Thus, extensive authigenic quartz cementation and thermal maturation of organic matter of the Wufeng Formation likely enhanced the reservoir capacity and fracturing ability of these deposits relative to the overlying Longmaxi Formation. This understanding is especially relevant to shale gas exploration and production considerations of organic-rich fine-grained sediments of similar sedimentological background. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pore and throat structure can be characterized separately by XCT scanning. • Chlorite and illite produced most of the intercrystalline pores in tight sandstone. • Chlorite coatings are effective in preserving the large primary pore-throat. • The densification was completed by cementation instead of compaction. • Tight sandstone with high chlorite is the best quality reservoir in the Ordos Basin. As an important part of tight sandstone, authigenic clay minerals and carbonate cements have a strong influence on the densify of tight sandstone, but the details of these effects on pores and throats need be further clarified. The Ordos Basin is the second-largest sedimentary basin in China with the highest annual oil output and is characterized by tight sandstone. In this paper, the thin section, HPMI, XCT scanning and fluid inclusion homogenization temperature were combined to study the densification process of the tight sandstone in the Ordos Basin. The results show that early chlorite coating can effectively reduce further damage to the pore-throat space. But the pore-lining chlorite and illite led to reduce of the radius of intercrystalline micropores to <1 μm. After mechanical compaction, authigenic illite and the late ferrocalcite and ferrodolomite cements continued to grow and eventually complete the densification. Authigenic clay minerals and carbonate cements played contrasting role on evolving of pores and throats: tight sandstone with high chlorite showed obvious "right peak" PSD and TSD in XCT scanning with the largest number of throats, formed the best-quality reservoir; tight sandstone with high carbonate cement suggesting flat "right peak" TSD and increased the average length of throats; tight sandstone with high illite showed flat and "left shift" PSD and obvious "bimodal" TSD with the fewest number of throats, and formed the worst-quality reservoir. [ABSTRACT FROM AUTHOR]

[Display omitted] • The western Ordos Basin has excellent potential to form sandstone-type uranium deposits. • The search for uranium reservoirs should focus on the northwest of the Ordos Basin. • Regions where intermediate-acid rocks are present are ideal targets for uranium exploration. • Tracking along the provenance supply direction is an effective method for uranium exploration. The Middle Jurassic Zhiluo Formation is the main uranium-bearing sequence in the western Ordos Basin, northern China. Provenance studies of clastic rocks in the Zhiluo Formation are important to provide guidelines for uranium exploration. In this paper, we describe the sandstones from the Zhiluo Formation and report their bulk rock elemental compositions by using samples that were collected from the Lingwu area, western Ordos Basin. Our main objective is to provide constraints on the provenance of the sandstones and thus new insights into uranium exploration. The results show that the sources of the Zhiluo Formation sandstones have TTG (trondhjemite-tonalite-granodiorite) attributes and mainly consist of magmatic arc orogenic belts that were mixed with continental blocks and recycled orogenic belt materials. The paleocurrent measurements that average 144° suggest that the provenance supply direction of the sandstones is from northwest to southeast. Combined with the regional tectonic settings, it can be inferred that the sandstone provenance was mainly provided by the Xingmeng Orogenic Belt, while the Alxa Block and Helan Mountain complex rocks also contributed. Our research might provide a crucial reference for predicting the locations of potential uranium reservoirs, i.e., the search for uranium mineralization should target the northwest of the Ordos Basin, especially near regions where intermediate-acid rocks are present. This information is integrated into a predictive model in which tracking along the provenance supply directions of clastic sediments is an efficient method for conducting uranium exploration in a sedimentary basin. [ABSTRACT FROM AUTHOR]

[Display omitted] • An integrated method was used to examine the ground fissure. • The strike of the YJZ-MGD ground fissure was parallel to the basin edge. • The YJZ-MGD ground fissure showing a synsedimentary structure feature. • Tectonic activity and groundwater exploitation jointly drive of the ground fissure. The Yangjiazhuang-Maguduo ground fissure, which is in front of the Luoyun Mountain on the western margin of the Linfen Basin, is a typical ground fissure that developed in the transition zone between the basin and mountain. In this paper, the developmental characteristics and mechanisms of the ground fissure in the transition zone between the basin and mountain under the action of fault activity and pumping were studied and analyzed through ground investigation, engineering geological mapping, trenching and geophysical exploration. The investigation and research confirmed that the strike of the ground fissure is parallel to the Luoyun Mountain piedmont fault and the ground surface has both horizontal extension and vertical offset. Trench result shows that the plane of the superficial part of the ground fissure is rough, which is typical tensile failure; the plane of the ground fissure under the bottom of the trench is smooth and mainly displaying shear deformation, and meanwhile the vertical offset of the stratum increases with depth showing synsedimentary structural characteristics. Shallow geophysical results reveal that the ground fissure is a manifestation of the Luoyun Mountain piedmont fault. Research suggests that deep tectonic activity caused pre-existing faults in the Luoyun Mountain piedmont to be in a continuous tensile shear state, which enhanced their activity and caused the pre-existing faults to extend to the surface, forming the ground fissure in the hanging wall of the fault. Continuous groundwater overexploitation led to the consolidation and settlement of the hanging wall of the Luoyun Mountain piedmont fault, which increased the differential settlement on both sides of the Luoyun Mountain piedmont fault, thus intensifying the movement speed of the Yangjiazhuang-Maguduo ground fissure and forming the present ground fissure. The development characteristics and formation mechanism of the Yangjiazhuang-Maguduo ground fissure provide not only an important reference for studying ground fissures in basin-mountain transition zones, but also guidance for the prevention and mitigation of such geological disasters. [ABSTRACT FROM AUTHOR]

[Display omitted] • The 97 Ma I-A transitional Shengsi granites comprise two phases by crystal-melt separation. • Medium-grained phase (MGP) represents the cumulate with less melts extracted. • Fine-grained phase (FGP) shows variable and depleted middle rare earth elements. • FGP is formed by fractional crystallization of titanite + plagioclase + zircon. • FGP represents the melt extracted from a crystal mush, leaving the residue forming MGP. The intrinsic mechanism on geochemical diversity of high-silica (>70 wt% SiO 2) granites (HSGs) still remains unclear. In this paper, we focus on the magmatic differentiation of the Shengsi Pluton at the northeastern tip of SE China by an integrated study of geochronology, whole-rock geochemistry and mineral chemistry of zircon and apatite. The Shengsi granites crystallized at ca. 97 Ma, and can be divided into early medium-grained phase (MGP) and late fine-grained phase (FGP). The FGP granites have higher SiO 2 (75.0–77.1 wt%) contents and lower amount of plagioclase, apatite and titanite. The MGP granites likely represent the primary granitic melts and they show transitional geochemical features between I- and A-type granites. In contrast, the FGP granites may represent the melts differentiated from the MGP magma mush and they are characterized by continuously varied to strongly depleted middle rare earth elements (MREEs). Geochemical modeling demonstrates that the varied REEs of the FGP granites are likely controlled by the crystallization/accumulation of titanite, plagioclase and minor zircon during magmatic differentiation. Such a crystal fractionation process in HSGs could be explained by slow "crystal settling" (mainly titanite) in crystal mush induced by dripping solid–liquid mixtures from the magma roof. This work exemplifies the effective crystal fractionation of >70 wt% SiO 2 melts to generate >75 wt% SiO 2 melts in the present coastal area of SE China, and it also highlights the role of slow settling of early crystallized minerals in crystal mush on geochemical diversity of HSGs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reflux seepage, burial and hydrothermal types of dolomite in the Cambrian Sanshanzi Formation are petrographically and geochemically identified. • Reflux seepage dolomitization was formed by high-salinity and Mg2+-enriched fluid penetrates downward into the limestone, and the dolomite has low δ 13C, high Sr and low Mn contents. • Burial dolomitization was due to the limestone deeply buried during the diagenetic stage and formed under a high-temperature and pressure environment. • Hydrothermal dolomitization occurred during Mg2+-rich hydrothermal fluid invaded, and the dolomite characterized by saddle dolomite with a positive δ Eu anomaly, and a low δ 18O value. The Cambrian Sanshanzi Formation is an important dolomite horizon in the Ordos Basin of northern China, and is well exposed in the western part of that basin. This paper focuses on the petrography and geochemistry of dolomites in this formation with an aim to provide a better understanding of their genesis. Reflux seepage, burial, and hydrothermal dolomites are identified in the Sa nshanzi Formation. Reflux seepage dolomites include dolomitic grainstone and powder crystal dolomite, and have high Sr and low Mn contents, a high CaO/MgO ratio and low δ 13 C values, and the reflux seepage dolomitization was formed by high-salinity and Mg2+-enriched fluid penetrates downward into the limestone. Burial dolomites are the main type of dolomite distributed through the Sanshanzi Formation. Burial dolomites are composed of fine- to coarse-crystal dolomite and have low Sr and high Mn contents, a low CaO/MgO ratio, and high δ 13C values. The features of high salinity, strong reducibility and negative δ 18O values indicate the burial dolomites formed under high-temperature and high-pressure conditions, the burial dolomitization was due to the limestone deeply buried during the later diagenetic stage. Hydrothermal dolomites are mainly characterized by saddle dolomite features, a positive δ Eu anomaly, and low δ 18O values, and the hydrothermal dolomitization occurred during Mg2+-rich hydrothermal fluid invaded. The reflux seepage and hydrothermal dolomite developed in local areas, with the hydrothermal dolomite affected by the distribution of faults. [ABSTRACT FROM AUTHOR]

The prolonged complex geological evolutionary history of the South China Block is documented in a well-preserved rock record that comprises an Archean to Neoproterozoic crystalline basement (metamorphosed igneous and sedimentary rocks) and Phanerozoic supracrustal rocks. Some global Precambrian tectonic events, such as the formation and breakup of the Columbia and Rodinia supercontinents are also represented in the region. Here we present an outline of potential contributions to the proposed special issue of the Journal of Asian Earth Sciences on "Precambrian tectonothermal events and crustal evolution of South China". A total of 13 papers primarily focus on the Precambrian geological events in the South China Block encompassing magmatism, sedimentation, and geodynamics. The new data included in the special issue would provide an update on the crustal evolution of the South China Block, and its implication on an improved understanding of the global events. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Zhugongtang deposit belongs to MVT deposits formed in an orogenic thrust belt. • Ores were deposited from low-temperature, low f O 2 and weakly acidic basinal brine. • H 2 S was sourced from synchronous seawater sulfates in ore-hosting sedimentary rocks. • Metals were derived from a mixed source of basement and country rocks. • Sulfide precipitation was triggered by mixing between two different fluids. The Sichuan-Yunan-Guizhou triangle region contains numerous economically important carbonate-hosted Zn-Pb deposits that occur in the Late Indosinian thrust and fold system rather than foreland basin. In this paper, we investigate the thrust-controlled Zhugongtang deposit (>30.0 Mt ores @ 6.76 wt% Zn and 2.27 wt% Pb) as a case study, using ore deposit geology, in-situ trace elements and isotopes in sulfides, to provide new insights into the ore genesis of the MVT deposits in the thrust belts. The sulfide orebody is structurally controlled by a kilometer-scale thrust system and occurs as open-space fillings, vein or replacement structures. Trace elements in pyrite show a low concentration of Co, Ni, Tl and Se, suggesting that the sulfides were formed under low-temperature (100–250 °C) and slightly reduced conditions. The δ13C PDB values (−7.53 to +1.73‰) in calcite lie between the marine carbonate rocks and sedimentary organic matter, and the calculated δ18O fluid values (+3.40 to +13.36‰) are different from that of marine carbonate rocks but partly overlap with the basinal brines. Such C-O isotope signature indicates that the carbon was mainly derived from the host rocks (limestone) with additional contribution from organic carbon. The oxygen isotope values suggest mixing of the basinal brine and the limestone. The δ34S values of sulfides within Permian strata (+12.2 to +15.3‰) and Devonian strata (+18.5 to +23.8‰) are similar to the coeval seawater sulfate within the ore-hosting strata, respectively. This indicates that the reduced sulfur is originated from evaporative sulfate within host rocks by thermo-chemical reduction in the near-close system. In-situ Pb isotopic ratios of galena (206Pb/204Pb = 18.566–18.758, 207Pb/204Pb = 15.757–15.769 and 208Pb/204Pb = 39.061–39.366) are comparable with the Proterozoic basement and the country rocks, indicating the mineralizing metals were mainly derived from basement rocks and partly extracted from country rocks via fluid-rock interaction. Regional geological evidence indicates the timing of Zn-Pb mineralization of Zhugongtang is Late Triassic to Early Jurassic and related to the Indosinian orogeny. Overall, the newly obtained trace element and isotopic data together with geological evidence suggest that the Zhugongtang deposit is an MVT deposit formed in the orogenic thrust belt and that fluid mixing was critical for the ore formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The eastern Songnen Massif of the eastern CAOB has undergone Late Permian (260–251 Ma) regional metamorphism. • The metamorphic conditions were under lower amphibolite facies with P = 5.5–7.1 kbar and T = 592–630 °C. • This medium-pressure metamorphic event was collision-related and marks the final closure of the eastern Paleo-Asian Ocean. The nature of late Paleozoic metamorphism in the eastern Central Asian Orogenic Belt (CAOB) is controversial. This paper reports mineral chemistry, petrological, and zircon and titanite U–Pb age data for representative rocks in the Dongfengshan Group from the eastern margin of the Songnen Massif. We use these data to determine the rock associations, P–T conditions, and timing of metamorphism. The P–T conditions were estimated from 54 mineral pairs in representative rocks, including garnet–biotite schist, garnet–two-mica schist, garnet–biotite–plagioclase gneiss, and garnet amphibolite, and indicate the Dongfengshan Group experienced metamorphism at P = 5.5–7.1 kbar and T = 592–630 °C (i.e., a geothermal gradient ranging from 25 to 30 °C/km) under medium-pressure lower amphibolite-facies conditions. The biotite–plagioclase gneiss and garnet amphibolite yielded titanite U–Pb ages of 251 and 260 Ma, respectively, which are interpreted to represent the regional metamorphic age (260–251 Ma). The consistency of these dates and ages of metamorphic rims in zircons from a biotite plagiogneiss (252 Ma) confirm that medium-pressure metamorphism occurred in the late Permian rather than the Neoproterozoic, as assumed previously. Based on metamorphic, magmatic, stratigraphic, and paleontological constraints, as well as the regional tectonic history, we propose that late Permian medium-pressure metamorphism in the Dongfengshan Group occurred during the collision and amalgamation of the Siberian and North China cratons following the final closure of the eastern Paleo-Asian Ocean. [ABSTRACT FROM AUTHOR]