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The Jiamusi‐Khanka Massif is an important tectonic unit of the Central Asian Orogenic Belt in North‐east China. Its Late Palaeozoic tectonic properties and the timing of assembly have restricted the understanding of the tectonic evolution process at the eastern segment of the Central Asian Orogenic Belt for a long time. Based on the study of clastic rock petrology and zircon U–Pb chronology of the Early Permian Erlongshan Formation in Mishan, it is clear that the zircon age of the Early Permian Erlongshan Formation in Mishan is mainly Late Palaeozoic, with a major age peak at 300 ± 3 Ma and secondary age peaks at 356 ± 7 Ma and 475 ± 10 Ma. The provenance mainly comes from the magmatic arc source area, and Early Palaeozoic (500–420 Ma) detrital zircons mainly come from the south‐east margin of Jiamusi Massif, Late Palaeozoic (400–270 Ma) detrital zircons mainly come from the eastern margin of Jiamusi Massif and the northern margin of Khanka Massif. Among them, detrital zircons of a special age group 330–310 Ma come from the north of Khanka Massif, while 490–470 Ma detrital zircons which are common in the Early‐Middle Permian strata of Khanka Massif come from Jiamusi Massif. Combined with the evidence of petrology and palaeontology, this paper believes that the Early Permian Jiamusi Massif and Khanka Massif should be a unified Massif, that is, Jiamusi‐Khanka Massif. [ABSTRACT FROM AUTHOR]

The Ediacaran – Cambrian transition witnessed dramatic changes in the marine environment that are thought to have strongly influenced biological evolution. Previous studies have linked biological innovations to palaeo‐redox changes and suggested that increased productivity is the primary driver of the marine environment. However, the primary productivity and redox control mechanism still need to be clarified. Here, we present new organic carbon isotopes, total organic carbon contents, major elements, and trace and rare earth elements in drill‐core ZK107 from South China to reveal the continental chemical weathering, primary productivity, and redox control mechanism during the Earliest Cambrian (E‐C). Our studies have shown intense continental weathering, and primary productivity fluctuations that were supported by weathering (CIA, Rb/Al) and productivity (Babio, P) indicators. Additionally, the quantitative reconstructed productivity proxies (PP18, PP21, PP23) indicate a high primary productivity level in the E‐C ocean, surpassing that of the modern oceans. The strengthening of continental weathering mainly causes high primary productivity because it can alter the nutrient supply to the oceans. We suggest that changes in primary productivity closely associated with continental weathering are the leading cause of marine anoxia during the E‐C. This study establish a linkage between the land and marine system during the E‐C, confirming the terrestrial controls on the marine chemical changes and providing new insights into understanding the evolution of the Earth's surface changes during the Ediacaran – Cambrian transition. [ABSTRACT FROM AUTHOR]

The NE‐trending Jiangnan orogenic belt has experienced multi‐tectonic episodes since the Mesozoic separates the Yangtze Block in the north‐west from the Cathaysia Block in the south‐east. The Taqian–Fuchun thrust zone in north‐east Jiangxi Province is located in the eastern Jiangnan orogenic belt. It is considered as an essential unit to understand the geometry, kinematics and dynamics of the Mesozoic nappe structures in the eastern Jiangnan orogenic belt and an ideal region to reveal the Mesozoic tectonic evolution in South China. Here, we present new detailed structural data coupled with zircon U–Pb and apatite fission‐track dating studies, establishing a four‐stage deformation history and describing the geometry, kinematics, ages and dynamic background. The Middle–Late Triassic NW–SE compression event (D1, 243–226 Ma) is mainly characterized by regional angular unconformity between the Lower and Upper Triassic and asymmetric folding of the underlying strata. The associated regional NW–SE shortening was related to the intercontinental collision. The Middle–Late Jurassic NW–SE compression event (D2, 175–160 Ma) is characterized by the angular unconformity between the Middle Jurassic and Cretaceous and the SE‐vergent imbricate nappe structures. The shortening has been associated with the NW‐ward subduction of the Paleo‐Pacific Plate. The Late Jurassic–Cretaceous NW–SE extension event (D3, 160–67 Ma) includes the transition stage from compression to extension (160–145 Ma) and the intensive extension stage (145–67 Ma). The former is characterized by the development of the extensional detachment structures and intermediate‐acid magmatism, while the latter is characterized by the development of Cretaceous extensional sedimentary basins and A‐type granites. This extension was correlated to the slab roll‐back of the Paleo‐Pacific Plate. The Paleocene–Eocene compression event (D4, 67–35 Ma) is manifested by the thrusting of metamorphic rocks in the Shuangqiaoshan Group to the Cretaceous red beds. This shortening possibly originated from the collision between the India and Eurasian Plates. This study provides new constraints on the Mesozoic structural style and establish a reliable geochronological framework of the Mesozoic tectonic evolutions of the eastern Jiangnan orogenic belt. [ABSTRACT FROM AUTHOR]

Large‐scale magmatic activity and associated mineralization in South China are linked to the subduction of the palaeo‐Pacific Plate, although specific processes have remained controversial including the timing of subduction initiation and lithospheric extension. We present new geochemical data and zircon U–Pb and Lu–Hf isotope measurements on volcanic rocks, granites and mafic dikes from coastal south‐eastern China along the Eurasian continental margin. The biotite monzogranites show I–type granitoid affinity and fractional crystallization with zircon εHf(t) values ranging from −10.15 to +0.50, suggesting magma derivation from the melting of lower crust with the addition of juvenile crustal or mantle components. The biotite granites are typical of highly fractionated A‐type granites with εHf(t) values ranging from −3.63 to +1.35, indicating magma hybridization between anatectic granitic and mantle‐derived mafic magmas. The diabase dikes have zircon εHf(t) values ranging from −2.99 to +1.71, with high La/Nb and La/Ta ratios. This suggests derivation from partial melting of a lithospheric mantle metasomatized by fluid from a subducting–slab, with contributions of depleted asthenospheric mantle components. Our data, combined with those from previous studies, suggest that the shallow subduction of the palaeo–Pacific Plate beneath the Eurasian continent had begun by ca. ~170 Ma at least and the subduction orientation changed to oblique with respect to the continental margin. Steepening of the subduction angle likely caused a slab rollback during the Early Cretaceous, resulting in a tectonic transition from compression to extension in South China at ca. 145 Ma. [ABSTRACT FROM AUTHOR]

This paper reports two types of basalt that have different ages (Carboniferous and Permian) but occur next to each other in the northern part of the Changning–Menglian accretionary wedge, southwestern China. We use the geochronology and geochemical data to evaluate the tectonic evolution of the Palaeo‐Tethys during this period. Zircon grains from the mafic‐ultramafic rocks associated with the Permian basalts in the Xiaomengtai area yield a U–Pb age of 281 Ma and εHf(t) values from +9.2 to +12.8. The Permian mafic‐ultramafic rocks and the associated basalts are all characterized by normal mid‐ocean ridge basalt (N‐MORB)‐like chondrite‐normalized rare earth elements patterns, moderately negative Nb‐Ta anomalies in the mantle‐normalized immobile incompatible trace element patterns, and positive εNd(t) values from +4.2 to +6.5, which are consistent with the geochemical characteristics of mafic‐ultramafic rocks in supra‐subduction zone (SSZ)‐type ophiolite. On the contrary, the Carboniferous basalts, which are associated with marine carbonates, are characterized by light REE enrichments, slightly positive Nb‐Ta anomalies, and εNd(t) values from +2.8 to +4.0. These features are similar to those of typical oceanic island basalts (OIBs) worldwide. Modelling results using REEs show that the parental magmas for the Carboniferous OIBs and the Permian basalts were likely derived from mantle peridotites at the depths of garnet and spinel stability, respectively, consistent with the formation depth of these two different types of basalt globally. The occurrence of these two different types of mafic‐ultramafic rocks with significantly different ages in the same area supports the view that they are the remnants of the accreted Palaeo‐Tethys oceanic crust. The Carboniferous OIBs are considered to be parts of an OIB‐carbonate seamount chain that originally formed in the southern part of the Palaeo‐Tethys. The Permian mafic‐ultramafic rocks are regarded as fragments of SSZ‐type ophiolites that were present in the northern part of the Palaeo‐Tethys. These different pieces of oceanic crust were accreted to the Simao–Indochina continental Block by subduction between the Late Permian and the Triassic. [ABSTRACT FROM AUTHOR]

The tight sandstone reservoirs have become the focus of today's oil and gas exploration. To clarify the microscopic characteristics of the tight sandstone reservoirs of the Chang 63 deep water gravity flow origin in the Huaqing area, the Chang 63 gravity flow origin reservoirs in the study area are divided into three categories. They are the formation reservoir of sandy clastic flow (FROSF), formation reservoir of muddy debris flow deposits and turbidites (FROMT) and formation reservoir of slides and slumps (FROSS). In this study, core and logging data, thin sections, field emission scanning electron microscopy (FE‐SEM), and mercury intrusion capillary pressure (MICP) were combined to investigate the rock composition and pore‐throat characteristics of tight sandstone reservoirs with different types of gravity flow origins. The reservoir micro‐heterogeneity is also investigated in this paper. The results show that the reservoirs with different gravity flow origins are similar in lithology and are mainly composed of feldspar lithic sandstone and lithic feldspar sandstone. The pore types are mainly intergranular pores and feldspar‐dissolved pores. There are significant differences in the porosity, permeability, microscopic pore‐throat characteristics and microscopic heterogeneity of the reservoirs. From FROSF to FROMT and FROSS, the porosity, permeability, mercury inlet saturation, discharge pressure, median pressure and mercury removal efficiency gradually decrease. The tightness of the reservoir gradually increases. The storage capacity is gradually reduced. The disparity between the throat radius and pore radius gradually increases. The pore‐throat structure becomes more complex, and the microscopic heterogeneity of the reservoir gradually increases. [ABSTRACT FROM AUTHOR]

The Dongji epithermal Au deposit formed in the Early Cretaceous is located in the Dongkeng volcanic Basin of the South China Block. The orebodies of the deposit are mainly hosted in the Jurassic volcanic–subvolcanic rocks. Here, detailed zircon U–Pb geochronology, major‐trace elements, and fluid inclusion data of the Dongji deposit are reported. At least two epochs of magmatic activity were identified at Dongji, including the Late Jurassic rhyolitic crystal tuff lava (165.3 ± 1.8 Ma to 162.8 ± 2.6 Ma) and quartz porphyry (156.0 ± 1.9 Ma), and the Early Cretaceous dacitic crystal tuff lava (108.4 ± 5.7 Ma) and purplish‐red crystal tuff lava (98.1 ± 0.8 Ma). The Late Jurassic volcanic–subvolcanic rocks are characterized by high SiO2 content, enriched LILE (large ion lithophile element) elements, depleted HFSE (high field strength element) elements, and obvious P, Ti and Eu anomalies. These geochemical characteristics suggest that the volcanic–subvolcanic rocks were generated by partial melting of the lower crust and controlled by fractional crystallization of Ti‐bearing phases, apatite, and plagioclase. In comparison, the Early Cretaceous volcanic–subvolcanic rocks are characterized by high K contents, and arc‐like signatures (e.g., enriched Rb, Th, K, and depleted Nb, Ta, Ti), indicating a partial melting of crust–mantle interaction under an extensional tectonic setting. The ore‐bearing dacitic crystal tuff lava and the caprock of purplish‐red tuff lava constrain the timing of gold mineralization in the range of 108–98 Ma. The Au mineralization at Dongji is divided into the early stage of quartz‐pyrite association and the late main mineralization stage of quartz‐polymetallic sulfide association. The fluid inclusion microthermometry results show that the ore‐forming fluids at the early mineralization are characterized by enrichment of liquid‐rich two‐phase inclusions and CO2‐bearing aqueous inclusions. The fluids with moderate homogenization temperatures (292–382°C) and low salinities (5.4–10.0 wt% NaClequiv) were possibly exsolved from magmatic rocks. Nevertheless, fluid inclusions in the late‐stage contain liquid‐rich two‐phase inclusions and pure liquid phase inclusions. The homogenization temperatures (222–309°C) and salinities (2.4–8.3 wt% NaClequiv) of the late‐stage fluid inclusions are relatively lower than those of the early stage, probably indicating a fluid mixing of magmatic and meteoric fluids. Based on the above, we propose that fluid mixing is the key factor facilitating Au precipitation in the Dongji deposit, probably applicable to other Au deposits in the Dongkeng volcanic Basin. [ABSTRACT FROM AUTHOR]

The Wenjiaping granite, as one of the few Late Jurassic granites in the Songpan–Garzê fold belt (SGFB), can provide an important clue for comprehensively recognizing the tectonic evolution and mineralization of this belt. In this contribution, we present new age and geochemical data for this pluton to better constrain its petrogenesis and discuss the tectonic and metallogenic implications. LA‐ICP‐MS zircon U–Pb dating shows that the Wenjiaping pluton was emplaced at ~159 Ma. The granite contains minor amphibole, and exhibits slightly peraluminous characteristics (A/CNK = 1.03–1.10) and lower initial Sr–Pb isotope ratios than those of the Liwu Group, which excludes the possibility that the Wenjiaping granite was derived from partial melting of the metasedimentary rock‐dominated Liwu Group as previously suggested. Significantly, high Sr/Y (40.93–54.30), LaN/YbN (39.64–56.64), and K2O/NaO (0.77–1.11) ratios, low MgO (0.47%–0.86%) and Cr (25.1–41.3 ppm) contents, and relatively enriched Sr–Nd–Pb–Hf isotope compositions of the Wenjiaping granite are comparable to those of the Late Triassic adakitic rocks in the SGFB, indicating that they probably share a similar source. Combined with previous researches, we propose that large‐scale detachment of the Jianglang dome caused by post‐collisional lithospheric extension in the SGFB‐induced decompressional partial melting of the Precambrian basement rocks can account for the generation of the Late Jurassic Wenjiaping pluton. In addition, our results also suggest that the Wenjiaping pluton probably cannot supply abundant metal elements for the Liwu‐type Cu‐polymetallic deposits in the Jianglang dome, SGFB. [ABSTRACT FROM AUTHOR]

The Tan–Lu Fault zone (TLFZ) is the largest fault zone in eastern China and a typical and representative structure of the Circum–Pacific tectonic domain. The Late Mesozoic tectonic evolution of the TLFZ is greatly significant, since it revealed the Jurassic–Cretaceous tectonic evolution of eastern China and the subduction history of the Palaeo–Pacific Plate. However, its tectonic evolution in the Early Cretaceous remains controversial. Based on geological mapping, microstructural analysis, and LA–ICP–MS zircon U–Pb dating, we constrained the deformation history of the Feidong Segment of the TLFZ in the Early Cretaceous. Results showed that the Feidong Segment of the TLFZ experienced a strong sinistral strike–slip movement at the beginning of the Early Cretaceous (~143 Ma); it was subsequently subjected to normal faulting during the Early Cretaceous (135–102 Ma), which controlled the strong magmatic activities within the Feidong area. At the end of the Early Cretaceous (~100 Ma), a weak sinistral strike–slip movement occurred again along the TLFZ. The deformation temperatures of the two sinistral strike–slip shearing stages were 500–550°C and 400–450°C, respectively. The regional comparison indicated that the Early Cretaceous tectonic evolution of the TLFZ was actually the epitome of the contemporaneous tectonic evolution of eastern China and was the result of strain localization in the Cretaceous tectonic framework of eastern China. [ABSTRACT FROM AUTHOR]

The Saishitang deposit, located in the eastern part of the Eastern Kunlun Orogenic Belt, NW China, hosts important Cu mineralization. The ore occurs as stratiform bodies in Lower–Middle Triassic siltstone and siliceous rock and as lenticular bodies at the contacts between quartz diorite and marble. The whole‐rock geochemistry and Si–O isotopic compositions of the siliceous rocks suggest a sedimentary origin. The quartz diorite has a weighted mean zircon U–Pb age of 215.5 ± 0.9 Ma. The quartz diorite exhibits high SiO2 (63.91–69.48 wt%), Al2O3 (14.98–17.11 wt%) and Na2O (2.17–4.58 wt%) contents, with A/CNK values of 0.79–1.10, similar to those of calc‐alkaline I‐type granites. The quartz diorite exhibits weak negative Eu anomalies (δEu = 0.80–0.99), enrichment in light rare earth elements, Rb, Ba, K and Pb and depletion in heavy rare earth elements, Nb, Ta, P and Ti. The Pb isotopic compositions suggest that the skarn ore, quartz diorite and host rocks are closely correlated, reflecting a common source. By contrast, the Pb isotopic compositions of sulphide ores hosted within siltstone are heterogeneous, suggesting multiple lower‐crustal and upper‐mantle sources. By integrating our geological and geochemical data, we propose that the Saishitang deposit was formed by exhalative sedimentary mineralization in a back‐arc basin and overprinted by Indosinian skarn mineralization in a post‐collision extensional environment. [ABSTRACT FROM AUTHOR]

The drainage basin of the upper reaches of the Yellow River from Lagan Gorge to Liujia Gorge, which spans Gonghe, Guide, Jianzha, Xunhua and Linxia basins, is located in the transition zone between the Qinghai–Tibet Plateau and the Loess Plateau, northwestern China. Its evolution is controlled by the northeastward growth and uplift of the Qinghai–Tibet Plateau. To characterize and quantify the response of surface processes to deep geological mechanisms and to investigate the types of Late Cenozoic tectonic deformation in the study area and the relationship with large geological hazards, we analysed various geomorphological indicators, combined with field observations and the estimated incision rates and established a reasonable tectonic deformation model. The results demonstrate that the variations in the geomorphic indices are highly consistent with active tectonics. Higher hypsometric integral (HI), higher normalized stream length‐gradient index (SLK), higher basin asymmetry factor (AF), higher drainage basin shape (BS) and lower ratios of valley floor width to valley height (VF) indicate higher tectonic uplift rate in the Jianzha‐Xunhua basins compared to other basins where there are many giant landslides. These giant landslides occurring there can probably be correlated with the vigorous tectonic activity, thus generating a great significance in geological hazard prevention and control along the upper Yellow River. [ABSTRACT FROM AUTHOR]

Detrital zircon U–Pb ages and Lu–Hf isotopes of three metasandstone samples from the recently identified Caiziyuan‐Tongan accretionary complex (CTAC) in the southwestern Yangtze Block are presented. The detrital zircons are characterized by high Th/U ratios, oscillatory zoning, and nonabrasive crystal shapes, implying that these metasandstones in the CTAC were dominantly derived from proximal magmatic sources. The detrital zircon age spectrum shows three prominent intervals of 2.8–2.6 Ga, 2.5–2.2 Ga, and 2.1–1.7 Ga with minor dispersions between 3.8 and 2.9 Ga, matching well with those of the exposed magmatic rocks in the Yangtze Block. Two samples show consistent youngest age peaks at ~1.72 Ga, but the remaining sample has the youngest age peak at ~1.56 Ga, indicative of their differences in depositional ages. The Eoarchean zircons have negative εHf(t) values with Hadean depleted mantle two‐stage (TDM2) model ages, indicating the earliest crustal growth of the Yangtze Block in the Hadean. The Mesoarchean to Neoarchean zircons show both negative and positive εHf(t) values, suggesting a prolonged and complicated crustal reworking and growth process. By contrast, the Paleoproterozoic zircons have dominantly negative εHf(t) values, suggestive of extensive crustal reworking in response to the Nuna supercontinent assembly. Available detrital zircon TDM2 model ages from the southwestern Yangtze Block produce three prominent peaks at ~3.06 Ga, ~2.95 Ga, and ~2.84 Ga, suggesting significant crustal growth pulses in the Mesoarchean. Given that the ~1.38 Ga Caiziyuan SSZ‐type ophiolitic mélange and the complex tectonothermal evolution process, we deduce that the CTAC belt may represent a relict suture zone between micro‐blocks in the Yangtze Block and may have witnessed the Nuna breakup and subsequent Rodinia assembly. [ABSTRACT FROM AUTHOR]

This study aims to investigate the significance of the geochemical differences and the factors that control the geochemistry of two major types of coal‐bearing stratum claystones (sedimentary kaolinitic claystone [SK‐claystone] and tonstein). The SK‐claystone and tonstein derived from the Taiyuan Formation of the Upper Carboniferous coal‐bearing strata in the Datong Coalfield of North China have been comprehensively analysed using X‐ray powder diffractometer, scanning electron microscopy, X‐ray fluorescence, and inductively coupled plasma mass spectrometry. The results showed that the SK‐claystones and tonsteins exhibit similar SiO2 content; however, the content of Al2O3 in tonsteins is higher than that in SK‐claystones, whereas the TFe2O3 and K2O content in tonsteins are lower than those in SK‐claystones. These findings are consistent with the mineral composition analysis of the samples. The SK‐claystones and tonsteins have different parent rocks, as shown by the Al2O3/TiO2 ratios, diagram of Zr/TiO2 versus Nb/Y, and chondrite‐normalized rare earth element patterns. The palaeosalinity indexes (B/Ga and Sr/Ba) and palaeoredox proxies (Mo and U enrichment factors as well as U/Th ratios) indicate that both SK‐claystones and tonsteins were formed in freshwater suboxic–oxic environments. The kaolinite in SK‐claystones and tonsteins is formed via the deposition or crystallization of aluminium‐rich weathering products and alteration of volcanic ash, respectively. In summary, the different parent rocks and diagenetic processes are the main factors differentiating the geochemical characteristics of the two types of claystones. Our study links the different types of elemental enrichment features to the geological genesis of the two types of claystones, indicating that the trace elemental enrichment characteristics can be used as indicators for distinguishing the SK‐claystone and tonstein in the Datong Coalfield as well as other similar coalfields. [ABSTRACT FROM AUTHOR]

The Mashan Complex of the Jiamusi Massif was traditionally considered as the oldest stratigraphic sequence in eastern NE China. However, the metamorphic degree of the Mashan Complex is different in different areas, which can be divided into Jixi–Mishan–Hulin granulite facies belt and Luobei–Huanan–Mudanjiang amphibolite facies belt. Here, we investigated the Mashan Complex in the Yilan area and present lots of new petrological, mineral chemical, geochemical, and U–Pb geochronological data, in addition to phase equilibria modelling, to constrain the timing of metamorphism, P–T conditions, and the P–T path of the Mashan Complex, and furthermore to deduce the crustal evolution of the Jiamusi Massif. The protoliths of the Mashan Complex in the Yilan area are greywackes and felsic sandstones, whose provenance is dominantly felsic rocks formed from a continental island arc. Petrographic observations, traditional thermobarometry, and quantitative phase equilibria modelling of the studied samples reveal P–T conditions from M2 to M3 of ~7.2 kbar/760–800°C and 4.5–5.0 kbar/585–610°C, respectively, which together define a clockwise P–T path involving decompressional cooling (M3) that followed the peak granulite‐facies metamorphism (M2). It reveals essential information related to the collision orogeny and post‐collision process. Zircon U–Pb dating of two felsic rocks yielded the peak of the granulite‐facies metamorphism in the Yilan area of the Jiamusi Massif that might have occurred at ~500 Ma. The overall deposition of the metamorphic rocks was later than ~760 Ma and that most of the detrital materials came from late Mesoproterozoic and early Neoproterozoic source rocks. [ABSTRACT FROM AUTHOR]

As one of the most important energy sources in the world today, shale gas has attracted extensive research. Numerous scholars agreed that the organic matter (OM) pores in shale provide the main space which benefits effective gas occurrence. However, the connectivity provided by OM pores is more important in the development process than their reservoir properties. A comprehensive portrayal of the 3D connectivity of the OM pores is elaborated in this study. The Lower Silurian Longmaxi shale samples were selected as the research subject. The shale samples are subjected to focused ion beam scanning electron microscope, helium ion microscope observation experiments, 2D microscopic characterization of OM pores, and 3D segmentation extraction. The results indicate that the connectivity of shale is mainly contributed by OM pores. The OM pores have the advantageous structural characteristics of large number per unit area, evenly distributed, regular pore morphology, and large pore size relative to the mineral matrix pores. The OM pores structure in shale is complex with a network structure of small pores nested in large pores, which can increase the adsorption capacity of gas. Besides, the small pores nested in large pores can act as a throat to significantly improve the connectivity. OM pores in the pyrobitumen are interconnected in 3D space, providing the main channels for gas percolation in the shale reservoir. [ABSTRACT FROM AUTHOR]

Late Mesozoic granites are present throughout the Jiaodong Peninsula in eastern China, but the petrogenesis of these granites, the magma sources, and the geodynamic setting of the magmatism remain unclear. This paper presents new zircon U–Pb geochronological and Lu–Hf isotopic and whole‐rock geochemical data for the Late Jurassic Queshan pluton in the Shandong Peninsula, an area that represents the boundary between the Jiaobei and Sulu ultrahigh‐pressure (UHP) terranes. Laser ablation–inductively coupled plasma–mass spectrometry zircon U–Pb dating yields Late Jurassic ages from 158 ± 1 to 153 ± 1 Ma for the pluton in addition to a small number of inherited zircons that yield ages that cluster at 2410, 1831–1776, 750, and 209–202 Ma. Zircons from different samples have similar 176Hf/177Hf values (0.281926–0.282255) and variably negative εHf (t) values that range from −26.5 to −15.1 (weighted mean of −22.9 ± 0.9). The corresponding two‐stage Hf model ages range from 2,869 to 2,154 Ma, with a weighted mean value of 2,645 ± 54 Ma. These data indicate that the magmas that formed the Queshan pluton were derived from multiple sources, including the lower crust of the North China (NCC) and Yangtze (YC) cratons, as well as collision‐related alkaline rocks. The whole‐rock geochemical compositions of the samples indicate that the granites are weakly peraluminous, are high‐K and calc‐alkaline with I‐type affinities, and have high contents of Sr, low contents of Y and Yb, high (La/Yb)N and Sr/Y values, and positive Eu anomalies (δEu = 1.20–1.65), indicating an adakitic affinity. This indicates that the Queshan granites formed from magmas generated by partial melting of a thickened region of the crust (>50 km) associated with eclogite, garnet amphibolite, or amphibolite residual material. The genesis of the Late Jurassic granites are also likely to have been influenced by the collisional orogeny between the NCC and YC and continued subduction of the Izanagi Plate. Thickening of the lower crust associated with this continental collisional event occurred before the magmatism, with further compression and thickening of the lower crust caused by the low‐angle subduction of the Izanagi Plate beneath northeastern China being the main geodynamic driver of the formation of the granites in this region. [ABSTRACT FROM AUTHOR]

Terrestrial red beds are extensively developed in the Upper Jurassic of the Sichuan Basin, southern China, where few fossils have been documented. Recently, abundant silicified wood specimens were found in the central Sichuan Basin, but no plant foliage fossils have been recorded from the same strata. Here, we report the first leafy shoot fossils collected from the red beds of the Upper Jurassic Penglaizhen Formation in Shehong City, central Sichuan Basin. Based on careful comparisons with potential Mesozoic conifer fossils, they were assigned to Pagiophyllum, an extinct conifer taxon of the family Cheirolepidicaceae. The generic classification agreed with the palaeovegetation features of the Penglaizhen Formation which were represented by gymnosperms of Araucariaceae (Agathoxylon‐type wood) and Cheirolepidiaceae (Brachyoxylon‐type wood). The non‐coexistence between the leafy shoot fossil and the petrified wood depicted a unique process of fossil preservation, which may be related to the palaeo‐flood events in this area. The palaeoclimate background during the Late Jurassic of Shehong was suggested to be a hot and semi‐arid or arid condition, supported by the Classopollis‐dominated (75–90%) pollen assemblage from the Penglaizhen Formation. The fossil foliage was collected from lacustrine or fluvial sediments. This suggests that the rainy season is a key factor in the development of regional lakes or rivers and flood events, which offered a suitable local environment for plant growth and helped construct a more complex ecological system, allowing a variety of creatures to survive in the central Sichuan Basin area. [ABSTRACT FROM AUTHOR]

The Chaqiabeishan area of the Quanji Massif in NW China is characterized by extensive Li‐rich pegmatites and granites of various ages. In this study, the major and trace element compositions, U–Pb zircon ages, and zircon Hf isotopic compositions of the granites were investigated, including the Garideng porphyritic monzogranite, the Gongkaxiuma monzogranite, and the Narong granitic porphyry. Precise U–Pb zircon dating revealed that these three granites were emplaced at approximately 468, 444, and 245 Ma, respectively. The geologic and geochemical data indicate that the Garideng porphyritic monzogranite and the Narong granitic porphyry are two I‐type granites, and the Gongkaxiuma monzogranite is an A2‐type granite. Based on the Hf isotopes and geochemical data, the Garideng porphyritic monzogranite and the Narong granitic porphyry were derived from partial melting of the relatively deep and relatively shallow juvenile mantle‐derived mafic lower crust, respectively, while the Gongkaxiuma monzogranite was derived from partial melting of the granulitic metamorphic basement. Moreover, tectonically, the Garideng porphyritic monzogranite represents the northward subduction of the South Qilian oceanic plate from 500 to 440 Ma. The Gongkaxiuma monzogranite represents the closure of the South Qilian Ocean by ~440 Ma, and the Narong granitic porphyry represents the Late Permian to Middle Triassic southward subduction of the Zongwulong oceanic plate under the Quanji Massif. [ABSTRACT FROM AUTHOR]

In the Yangtze Block, the Early Cambrian Niutitang Formation is mainly composed of mudstone, shale, and carbonates which are important for investigating the depositional environment and evolution of the Early Cambrian rocks. The Niutitang Formation in the study area has a greater geologic interest due to its polymetallic beds, depositional age, variation in environmental conditions, Cambrian explosion, organic matter (OM) enrichment, algal boom, etc. This research represents the sedimentary geochemistry of the Early Cambrian Niutitang Formation to reconstruct the palaeo‐depositional environment and to evaluate the OM enrichment mechanism by means of total organic carbon (TOC), biomarkers, carbon isotopes, mineralogy, scanning electron microscope, etc. Based on the variation in TOC content, the Niutitang Formation is divided into three parts (upper, middle, and lower). The majority of the samples from the middle part of the Niutitang Formation exhibit an excellent source of hydrocarbon (TOC > 4.0 wt%) relative to the upper and the lower part. The lighter carbon isotopic composition (<−30.7%) in these sediments reveals the presence of the I‐amorphous kerogen group. Moreover, these lighter δ13Corg values suggest the presence of type‐I oil‐prone kerogen. Saturated hydrocarbon in these rocks showed the dominance of short‐chain n‐alkanes maximizing at C18. The predominance of these n‐alkanes represents that the OM is chiefly derived from algal/bacterial input. Similarly, the dissymmetric V shape of C27‐C28‐C29 steranes with a predominance of C27 and the higher values of ∑nC21−/∑nC22+ in all three parts reflects that the OM in these rocks is chiefly originated from the lower aquatic marine organisms. Based on the Pr/Ph ratio, it is predicted that the middle part of the Niutitang Formation was deposited in extreme anoxic conditions (Pr/Ph < 0.5), whereas the upper and lower parts were deposited in relatively less anoxic conditions. Some biomarkers have more stable stereochemistry, which cannot be affected by diagenetic processes. These stable configurations are utilized to measure the maturity of OM, that is, Ts/(Ts + Tm), C29ββ/(ββ + αα), C29αα20S/(20S + 20R) steranes, and homohopane C31 22S/(22S + 22R). These geochemical indices reveal that the Early Cambrian Niutitang Formation in the studied area is mature to the post‐mature in the gas generation phase. Moreover, the hydrothermal fluids rich in metallic elements (e.g., Mo, Zn, V, and U) from the deeper part of the Earth owing to elongational forces among Yangtze and Cathaysian plates over Early Cambrian time entered the oceanic basin via remnant features (fissure and cracks) and through upwelling phenomena interacted with shelf sediments. At the ocean's surface, these nutrient‐rich fluids enhanced the breeding and evolution of marine life (bio‐productivity), which created hypoxic water conditions suitable for the preservation of OM in these rocks. [ABSTRACT FROM AUTHOR]

Recognition of deformation events documented in Neoproterozoic sedimentary sequences of the Jiangnan Orogen is critical in understanding the tectonic evolution of South China. In this contribution, we present new field based structural observations, microstructural analysis, and geochronological data for the Sibao and Danzhou groups in the southwestern Jiangnan Orogen of northern Guangxi, South China. Integrating the new information with previously published structural and geochronological data, we have identified three major deformation events. The earliest event generated E–W‐trending high‐angle tight linear and overturned isoclinal folds in the Sibao Group with their fold axial planes dipping to the south. This shortening event occurred in the mid‐Neoproterozoic time (840–800 Ma) and was associated with the orogenic collision between the Yangtze and Cathaysian blocks in South China. The angular unconformity between Sibao and Danzhou groups provides strong evidence for the collision. The second deformation event produced the large‐scale NNE–SSW‐striking ductile shear zones in the region. It also overprinted the pre‐existing E–W‐trending folds, refolded the Sibao Group, and generated the large‐scale NNE–SSW‐trending open folds in the overlying Danzhou Group and the west‐dipping cleavage within both groups. The second event occurred during the early Palaeozoic time (460–410 Ma) as a result of a WNW–ESE‐oriented intracontinental shortening process. The latest deformation event generated slight crenulation cleavage in the Sibao Group, some folds in the marble units of the Danzhou Group, and normal‐sense shearing along the pre‐existing NNE–SSW‐striking shear zones, all of which are the result of a NW–SE‐directed crustal extension during the late Palaeozoic (410–350 Ma) Kwangsian (Caledonian) orogenic collapse. [ABSTRACT FROM AUTHOR]

In this study, we conducted sandstone petrography analyses and determined detrital zircon U–Pb ages and Hf isotopes for sandstones collected at different stratigraphic levels of the lowest strata of the Laiyang Group. All results nearly point to an evolutionary trend for the source regions of the strata. The detrital zircon U–Pb results reveal multiple age groups at 140–123 Ma, 810–700 Ma, and 2,500–1,750 Ma, but variable age proportions for two sandstones (19LY‐01Z and ‐05Z) collected at lowermost and middle levels of strata, respectively, but only one unimodal age mode at ca. 1,850 Ma for the uppermost sandstone 19LY‐09Z. Provenance analysis illustrates that the lower strata likely include two source regions, including the Jiaobei Terrane and the Sulu orogen, whereas the upper strata appeared to have one dominant source region (i.e., Jiaobei Terrane). Framework modes of sandstones display that lower samples contain more metamorphic lithic fragments, which corresponds to the recycled orogenic field in the Q‐F‐L diagram, while middle‐upper samples are enriched in feldspars but deficient in lithics and plot in the basement uplift field of the Q‐F‐L diagram. This compositional variation reflects an evolution of the source regions from the Sulu Orogen to the Jiaobei Terrane, completely consistent with the observation of an increase in the amount of detrital zircons sourced from the Jiaobei Terrane, but decreasing detrital zircons from the Sulu Orogen in an upward order. This shift in the provenance of sediments reflects two tectonic events including exhumation of the Sulu Orogen to the surface before sedimentation of the Laiyang Group, and a rapid uplift of the Jiaobei Terrane after ca. 125 Ma following removal of lithospheric mantle. [ABSTRACT FROM AUTHOR]

There are various sedimentary structures developed in the black shales of the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation in Luzhou area, southern Sichuan Basin, southwestern China. In order to evaluate the controlling effects of sedimentary structures on the key parameters of shale reservoir properties, collected classification of sedimentary structures, scanning electron microscope observation, analysis of shale fabric and porosity characteristics, low‐pressure nitrogen adsorption, methane isothermal adsorption, and conventional triaxial compression test were carried out based on shale samples from Wells A‐H1, B‐H1, C‐H1 and D‐H1 in the study area. The sedimentary structures recorded in these shales are categorized into five types: homogeneous bedding, weak horizontal bedding, strong horizontal bedding, discontinuous ripple bedding, and gravel‐bearing massive bedding. In general, the palaeo‐hydrodynamics and oxygen content of water columns were weak when homogeneous bedding shale was deposited. The organic matter is the most abundant and the total organic carbon content is up to 4.01% on average. The average quartz content is 43.5%, and the brittleness index is the highest. The porosity and adsorption capacity were the highest, with an average of 4.57% and 79.5 scf/ton, respectively. Combined with its mechanical properties of low Poisson's ratio and high Young's modulus, homogeneous bedding sedimentary structure is associated with the shale units possessing the highest organic matter abundance, the strongest reservoir property, and the best fracability, which is the priority target for exploration and development of the Wufeng to lower Longmaxi Formation in the Sichuan Basin, southwestern China. [ABSTRACT FROM AUTHOR]

Shipu volcanic area is located at the east of the Jiangshan‐Shaoxing Fault zone, an important part of the Mesozoic volcanic belt in the coastal south‐east China, which provides an excellent opportunity to study the origin of rarely outcropped and coexisting bimodal volcanic rocks and bimodal dyke swarms. Two stages of bimodal volcanic rocks and dyke swarms yield zircon U–Pb ages of ca. 118–121 Ma and ca. 95–93 Ma, respectively. Both bimodal magmatic rocks show enrichment in LILEs and LREEs, but depletion in HFSEs. Basalts of the early‐stage bimodal volcanism have whole‐rock (87Sr/86Sr)i ratio of 0.71121, εNd(t) value of −8.0, and zircon εHf(t) values of −19.3 to −11.7, while the contemporaneous rhyolites show whole‐rock (87Sr/86Sr)i ratios of 0.71023 to 0.71106, εNd(t) values of −7.5 to −6.6 and zircon εHf(t) values of −15.3 to −7.6 with TDMC of 0.96–2.11 Ga. Basaltic dykes of the late‐stage bimodal volcanism have whole‐rock (87Sr/86Sr)i ratios of 0.70898 to 0.70908, εNd(t) values of −5.8 to −5.7 and zircon εHf(t) values of −10.5 to 2.9, while coexisting rhyolitic dykes display whole‐rock (87Sr/86Sr)i ratios of 0.69618 to 0.71172, εNd(t) values of −3.1 to −3.0 and zircon εHf(t) values of −9.2 to 11.9 with TDMC of 0.37–1.71 Ga. These features suggest that the early‐stage basalts could be derived from partial melting of an enriched lithospheric mantle metasomatized by slab‐derived fluids, and its corresponding felsic end‐member is the product of partial melting of Proterozoic middle‐lower crust due to underplating of basaltic magmas with minor addition of mantle materials. As for the late‐stage bimodal volcanism, the basaltic dykes are also derived from an enriched mantle similar to the early‐stage counterpart. However, the rhyolitic dykes mainly originated from partial melting of ancient lower crustal materials with abundant input from the depleted mantle. As a whole, two stages of bimodal magmatism in Shipu area provide direct constraints on regional tectonic transition from an extensional arc setting to a back‐arc setting. [ABSTRACT FROM AUTHOR]

Abundant iron deposits characterized by stratified orebodies have recently been discovered in the Taxkorgan Terrane, West Kunlun Orogenic Belt, China. Of these deposits, the Zankan iron deposit was the first to be discovered and has the largest estimated tonnage. However, the iron mineralization types for this deposit and others in this area are uncertain, mainly because of the apparent conflict between their typical banded architecture and Cambrian ages. In this study, in situ sulfur isotopic and trace‐element compositions of pyrite, including that in orebodies coexisting with magnetite (Py(o)), pyrite veinlets in strata (Py(v)), and rhyolite and magnetite veins cross‐cutting rhyolite (Py(r)), were conducted to ascertain the genesis of the Zankan deposit. Our results reveal that the pyrite in Zankan deposit has marked positive δ34S values (17.20‰–29.86‰). In addition, Py(o) has low Co/Ni ratios, which are distinct to Py(r) and Py(v), meaning that they belong to typical marine chemical precipitates and magmatic–hydrothermal pyrite, respectively. The coexistence of pyrite and magnetite suggests that the Zankan iron deposit was precipitated in a euxinic basin. Together, our results suggest that seawater sulfate concentrations were low, and the scale and sulfur isotopic compositions of this euxinic basin were most likely dominated by changes in sea level eustacy, which controlled the proportions of seawater and riverine inputs. Comparison with typical Precambrian banded iron formations (BIFs) suggests that the Zankan iron deposit belongs to a unique class of Cambrian BIFs that were controlled predominantly by basins in a shelf environment with locally anoxic conditions. [ABSTRACT FROM AUTHOR]

This study presents new integrated stratigraphic, sedimentary, and geochronological data for Silurian to Devonian sedimentary rocks in the central North Qilian Belt (NQB), NW China. These data constrain the timing and processes involved in the Palaeozoic tectonic transition from compression to extension in the NQB. This study indicates that the Angzanggou Formation probably formed in a foreland basin setting during 439–430 Ma compression associated with the closure of the North Qilian Ocean. The terrestrial sedimentary rocks overlying the formation were most likely deposited in a superimposed basin at 409–388 Ma as a result of the post‐orogenic extension of the NQB, an event that involved initial post‐orogenic extension‐related sedimentation. Silurian–Devonian sediments were derived from multiple sources, including the NQB, Central Qilian Block (CQB), and Alxa and Dunhuang blocks. Convergence between the CQB and the Alxa Block propagated westward, leading to the scissor‐like closure of the North Qilian Ocean during the Middle to Late Silurian and the oblique docking and collision of these two blocks. This is evidenced by a lack of middle–upper Silurian sedimentary rocks in the middle and eastern NQB compared with the well‐developed and well‐preserved sedimentary strata in the western segment. Devonian retrogradation and intracontinental extension‐related magmatism in the NQB also provide evidence of long‐lived tectonic extension of the lithosphere. Combining these new data with previously published data for the NQB and the wider region suggests that the Devonian terrestrial strata were deposited in a post‐orogenic extensional setting similar to that in the North Qaidam and East Kunlun belts, indicating that the Palaeozoic large‐scale tectonic transition from compression to extension in these three belts most likely started during the Early Devonian. [ABSTRACT FROM AUTHOR]

A set of nodular limestones was developed in the first member of the Middle Permian Maokou Formation (denoted as the Mao‐1 member) in the south‐eastern Sichuan Basin, south‐west China. Borehole coring has shown excellent signals of oil and gas from the Mao‐1 member carbonates, and many drilling wells have obtained industrial‐level gas flow. To assess the natural gas exploration potential of the Mao‐1 member in this area, sedimentary characteristics of drilling cores are described, and the formation mechanism of natural gas reservoir and its key controlling factors are also evaluated using data obtained from field geological survey, core observation, and laboratory experimental analysis. On this basis, the process of natural gas accumulation and evolution is examined. The results show that the Mao‐1 member nodular limestone comprises abundant marls and packstone to wackestone, and they were deposited in a lower part of the carbonate ramp setting. The marls exhibit rather high organic‐matter abundance and hydrocarbon generation capacity. Natural gas is mostly enriched in the marls developed talc diagenetic shrinkage pores and a certain number of organic‐matter pores, and their reservoir properties are much better than that of packstone‐wackestone. The natural gas in the Mao‐1 member is mainly self‐generated oil pyrolysis gas. The gas reservoir is characterized by the co‐existence of source rocks and reservoir, a lithology‐controlled reservoir, and a structure‐fracture‐controlled enrichment mechanism. Organic‐matter‐rich marl constitutes the material basis for natural gas accumulation. Talc diagenetic shrinkage pores provide storage space for natural gas. Preservation conditions are the key to natural gas accumulation, and natural fractures are beneficial to high gas production. The gas reservoir is characterized by early intraformational enrichment and late interformational adjustment. The finding of the nodular limestone gas reservoir of the Mao‐1 member provides new insights into unconventional gas exploration in the Sichuan Basin, and shows great potential for increasing natural gas reserves and production in China. [ABSTRACT FROM AUTHOR]

The Matouniu gold polymetallic deposit in the Eastern Hebei Province (Jidong) in the northern margin of the North China Craton (NCC) is a skarn‐type ore deposit. Geochemical data, zircon U–Pb, and Hf isotope analysis of the mineralization‐related dioritic porphyrite and C–O–S–Pb isotopes from the deposit were used to investigate the origin, magmatic evolution, mineralization, and tectonic setting of the Matouniu gold polymetallic deposit. Zircon U–Pb dating reveals an emplacement age of 146.7 ± 1.1 Ma, indicating that the magmatism and mineralization occurred during the Late Jurassic. Geochemical, Hf, and Pb isotopic compositions indicate that the dioritic porphyrite was formed by the partial melting of the ancient mafic lower crust, leaving behind residual plagioclase, amphibole, and garnet, with traces of mantle material involvement. The S and Pb isotopic compositions revealed that both the ore‐forming materials and the dioritic porphyrite were derived from a deep‐seated magmatic source, which mainly originated from the lower crust, with minor input from the mantle. The C–O isotopic compositions suggest that the early ore‐forming fluids had a mainly deep‐seated magmatic source with minor meteoric water involvement, and were accompanied by continuous meteoric water involvement and water‐rock interaction during the fluid migration. The Matouniu gold polymetallic deposit and Late Jurassic dioritic porphyrite associated with skarn mineralization formed under geodynamics involved a compressional regime that was associated with the continuous subduction of the Palaeo‐Pacific Plate beneath the East Asia Plate. [ABSTRACT FROM AUTHOR]

Apatite fission track (AFT) sampled from Helan Mountain, of the western Ordos Basin, North China shows that the study area located in the western part of the North China Craton (NCC) has undergone four‐stage exhumation since Mesozoic time, that is, Late Jurassic to Early Cretaceous, Late Cretaceous, Early Cenozoic, and post‐late Miocene. Helan Mountain had slowly uplifted and eroded from the Late Jurassic to the beginning of the Cenozoic. The intensive deformation within NCC is attributable dynamically to the gently angular subduction of the Pacific Plate under the Eurasian Plate (EP). Helan Mountain has undergone sinistral strike‐slipping with a 60‐km maximum displacement caused by the collision of the southeast margin of EP during the Late Cretaceous. The Early Cenozoic tectonic event in the study area is respondent to collision between the Indian Plate and Eurasian Plate, whereas, the post‐late Miocene event is likely related to the eastward extension of Tibet Plateau. Based on the available AFT ages, the partial annealing zone for the palaeo‐Helan Mountain is ascertained to elevation ~1,200 m to ~2,100 m. The tectonic events occurring from Mesozoic to Cenozoic in Helan Mountain is directly related to the plate margin tectonism and representative for the intracontinental deformation of Eurasian Plate convergence. The sandstone‐type uranium deposits in the western margin thrust belt of Ordos Basin are related to the Late Jurassic to Early Cretaceous and Late Cretaceous exhumation events. Immediately after the host rock, the Zhiluo Formation sedimentation during the Middle Jurassic, the Late Jurassic ~ Late Cretaceous exhumations resulted in north–south‐trending anticlines, synclines, and thrust faults; meanwhile, the Zhiluo Formation was uplifted to the surface and infiltrated by uranium‐bearing oxidized fluids originated from the Helan Mountain. Uranium deposits were formed in both east and west limbs of folds. Finally, uranium mineralization ceased since the Cenozoic because the Yinchuan and Hetao faulted grabens have separated the Helan Mountain provenance from the western margin thrust belt. [ABSTRACT FROM AUTHOR]

Abundant well‐preserved microbially induced sedimentary structures (MISS) are exposed in the Xinji Formation, the earliest Cambrian sedimentary unit in North China. The MISS herein are categorized into microbial mat growth structure (wrinkle structures and mat biolaminites) and microbial mat destruction structure (sand cracks and 'Manchuriophycus' structures). The MISS developed on the surface of thick quartz sandstones, as well as the lithologic interface between thin sandstone and mudstone. Most of the sand cracks lack the direct evidence of microbial activities, whereas the mat biolaminites that consist of filamentous mica, clay minerals, and quartz grains may record the in situ microbial mats. The Xinji Formation deposited along with the Cambrian explosion when biodiversity and abundance of metazoan stayed relatively low. Besides, the intermittently exposed tidal flats are not the ideal place for early life, which exacerbated the ecological vacuum therein. The massive occurrence of the MISS in the siliciclastic rocks of the Xinji Formation indicated that the tidal flat setting during this period was still beneficial for accumulations of microbial mat because of the deficient grazing metazoans and weak bioturbation. [ABSTRACT FROM AUTHOR]

Cretaceous syntectonic growth strata in terrigenous basins in Southeast China have scarcely been reported in previous studies. This work focusses on the growth strata of the Early Cretaceous red beds in the East Yangtze Block (EYB), especially in the Huangshan Basin in southern Anhui Province, to help determine the Late Mesozoic tectonic domain and the precise timing of the initiation of extensional tectonics in Southeast China. Field observations show that the dip angles of the red conglomerate‐bearing sandstones from the lower part of the Huizhou Fm. vary from 49° to gentle dips towards the basin centre and that the visible and estimated thickness within a single bed increases slightly downward from the upper to the lower part. These characteristics indicate that the sedimentary area of the Early Cretaceous Huizhou Formation (Fm.) has undergone an extensional process with the expansion and deepening of the sedimentary basin by rotation of the border surface (limb) and thus deposited the extension growth strata simultaneously with (or closely after) the 139 Ma Shiling volcanic activity. Caused by a NW‐SE‐oriented extensional stress field since ca. 140 Ma, a model in which NE‐SW‐oriented tectonic lines transform to E‐W‐trending tectono‐magmatic belts by intersecting and inheriting the previous E‐W‐trending tectonic fabrics is established in the present work. Consequently, these phenomena are influenced by Palaeo‐Pacific Plate rollback and the inheritance of a structural framework from the regional basement strata and deformation series. [ABSTRACT FROM AUTHOR]

Aprotodon is an extinct genus of the family Rhinocerotidae with a peculiar morphology that is mainly embodied in the wide mandibular symphysis and a pair of prominent second low incisors. The genus once lived on the vast grasslands of Asia, from Pakistan, and Kazakhstan to China, during the Late Eocene to the Early Miocene. The scarcity and incompleteness of the record, however, make the morphological characteristics of Aprotodon rather perplexing. Here, we report on a better mandible fossil with an intact second right incisor from the Xianshuihe Formation from the Early Miocene age (approximately 21–20 Ma) in the Lanzhou Basin, Gansu Province, China. Several important features, notably the elongated strongly curved tusk‐like incisors and mandibular symphysis, which widens sharply in the anterior part of the mandible, support attribution to A. lanzhouensis. Compared with previous specimens, the material described here is distinct in the lack of p1, horizontal ramus, and the ventral morphology of the mandible symphysis. Based on the new fossil specimen, we provide new material for the understanding of this extinct peculiar rhinoceros. [ABSTRACT FROM AUTHOR]

The Junggar Basin is one of the largest and most petroliferous superimposed petroleum basins in China. This study focussed on the characteristics of the unconformity between the Jurassic and Cretaceous (J/K) and its influence on hydrocarbon accumulation in the Yongjin area, Junggar Basin. Based on the seismic reflection characteristics and wireline well logging response, we identified the structure of the unconformity, which consists of three layers: the basal conglomerate layer, weathered clay layer, and semi‐leached layer. Geochemical studies show that the crude oils of the Lower Cretaceous Qingshuihe (K1q) Formation in the Yongjin area are mainly derived from Permian source rocks and partly from Cretaceous source rocks. The abnormally high value of acoustic time and the low value of resistivity of mudstone indicate that the overpressure condition is pervasive in the Yongjin area and may act as the driving force for the vertical migration of hydrocarbon‐containing palaeo‐fluids. The poor sealing ability of the weathered clay layer of the unconformity between the Jurassic and Cretaceous (J/K) and the high abnormal overpressure indicate that the petroleum from Permian source rocks may break through the sealing of the weathered clay layer and migrate upward to the Cretaceous conglomerate to accumulate. In addition, the combination of faults, sheet sand bodies, and unconformities constitutes a three‐dimensional petroleum migration pathway. The evolution of the Che‐Mo palaeo‐uplift also affected the formation of source rocks and petroleum migration. Accordingly, the hydrocarbon accumulation model of the Cretaceous in the Yongjin area indicated that Late Palaeogene is the first accumulation period. Permian source rocks have entered a mature to high‐mature stage, where a large amount of generated oil and gas migrated along faults and unconformities and accumulated in the braided river channel sand bodies of the K1q Formation. The second accumulation period was the Neogene. The basin experienced a regional tilt leading to a south‐inclined stratum. The oil and gas migrated upwards along the Late Hercynian deep reverse fault (Carboniferous–Permian) and then passed through the shallow faults and migrated to the bottom sandstone of Cretaceous reservoirs. [ABSTRACT FROM AUTHOR]

The world‐class Rongna Cu(Au) deposit, located in the Duolong mining district, is the first epithermal‐porphyry deposit along the Bangong–Nujiang metallogenic belt. The acidic spring developed in the centre of the Rongna Deposit and its basin has a high amount of heavy metals. Therefore, metal elements (Cu, Pb, Zn, Cd, As, Cr and Hg), pH, SO42− of the Rongna River and the composition of its supergene minerals are studied to discuss the environmental influence and provide a theoretical basis for the comprehensive utilization and environmental management of the Rongna Deposit. The result shows that there are eight kinds of supergene minerals: natrojarosite, hexahydrite, tamarugite, anhydrite, pickeringite, bloedite, gypsum and naujakasite, among which, naujakasite is discovered for the first time in China. The material sources of these sulphate minerals and acidic water are from the sulphate in the ores that experience the leaching process and oxidation. The spring is severely acidified, whose pH values are 2.70–3.08, the single pollution index of Cr, Cd, Pb, Hg and As are less than 1, but the index of Cu and Zn exceed the Class III National Water Standard by about twice, showing a mild pollution, its comprehensive pollution index values 0.8 ~ (<2.5), showing good quality. The pH of Rongna River water values are 7.70–7.92, the single pollution index is less than 1, indicating no pollution, and the comprehensive pollution index is less than 0.8, indicating good quality. However, considering the vulnerable ecological environment in Tibet, the acidic spring still needs manual intervention. An open‐air reservoir can be built upstream of the acidic spring, and the pollutants can precipitate by natural evaporation and then be recycled. [ABSTRACT FROM AUTHOR]

Gabbro–granite complexes provide vital constraints on magmatism mechanisms, crust–mantle interaction processes, and regional tectonics. The petrogenesis and tectonic setting of Early Permian igneous rocks in the southeastern Central Asian Orogenic Belt have long been controversial. In this study, the Early Permian Wulajitu gabbro–granite complex in Xilinhot, Inner Mongolia was selected as a research object and an integrated study was conducted using field occurrence, petrology, zircon U–Pb ages, whole‐rock geochemistry, and in situ zircon Hf isotopes. The Wulajitu gabbro–granite complex consists of gabbro and syenogranite with crystallization ages of 277 ± 1 Ma and 274 ± 2 Ma, respectively, belonging to the Early Permian. Their SiO2 contents vary in the range from 43.07–51.60 wt% and 70.30–75.52 wt%, respectively, and exhibit a gap of 51.60–70.30 wt%, displaying a typical bimodal geochemical distribution. The gabbros are low‐K tholeiitic–calc‐alkaline series rocks that are enriched in large‐ion lithophile elements (e.g., Ba, K, and Sr), depleted in high‐field‐strength elements (e.g., Nb and Ta), and have positive εHf (t) values from +9.3 to +13.2, indicating that they likely originated from partial melting of depleted mantle modified by subduction slab fluids. The syenogranites are aluminous A‐type granites characterized by high SiO2 and K2O + Na2O; low Al2O3, CaO, and MgO; depletion in Ba, Nb, Ta, Sr, P, and Ti; enrichment in Rb, Th, U, K, Zr, and Hf; as well as a seagull‐type rare‐earth element distribution pattern with strongly negative Eu anomalies (Eu/Eu* = 0.30–0.52). They show homogeneous zircon Hf isotopic compositions (positive εHf (t) values from +11.4 to +13.7). All these geochemical signatures suggest that the syenogranites were generated from partial melting of juvenile crust under high temperature and low pressure. The Wulajitu gabbro–granite complex most likely formed in a back‐arc spreading basin. Such an extensional regime was closely related to asthenospheric mantle upwelling caused by the rollback of the subducted Palaeo‐Asian Ocean slab in the Early Permian. [ABSTRACT FROM AUTHOR]

The recent discovery of the Anyue gas field, with huge reserves, has great potential for ultradeep gas production in carbonate reservoirs. Previous exploration and exploitation of Member IV of the Dengying Formation in the Gaoshiti–Moxi area deposited during the Late Ediacaran have provided useful insight into palaeo‐gas reservoirs, and geological significance of the Precambrian microbial carbonate strata. In this study, the depositional sequence architecture has been established and typical environments from Member IV of the Dengying Formation in the Gaoshiti–Moxi area have been reconstructed through detailed sedimentological analysis of cores, petrophysical data, well‐logging data and seismic interpretation. One third‐order sequence was identified, which is subdivided into seven fourth‐order sequences and 18–19 fifth‐order sequences. The third‐order sequence is bounded by denudation surfaces or onlap surfaces, and composed of transgressive system tracts and highstand system tracts. The fourth‐order sequences are bounded by instantaneously exposed punctuated surfaces or lithology and lithofacies transition surfaces, featured by specific lithological cycles, such as 'lower microcrystalline dolomite, middle intraclastic dolomite and sparry thrombolite, and upper intraclastic dolomite', 'middle–lower sparry thrombolite and upper microcrystalline dolomite and sparry thrombolite', 'lower micritic thrombolite, middle micritic dolomite, and upper sparry thrombolite and laminites', and 'lower microcrystalline dolomite, middle intraclastic dolomite and argillaceous or micritic dolomite, and upper intraclastic dolomite'. The sequence characteristics reveal that periodic high‐frequency sea‐level change and palaeogeomorphology are controlling factors affecting sequence development, which lay a significant foundation for reservoir development. During the depositional period, a tidal flat on a restricted carbonate platform is well‐developed, allowing the identification of 16 microfacies, 13 microfacies associations, and 6 seismic facies. Inter‐lower tidal flats are widely developed with band‐shaped mound–bank complex, microbial mound, and shoal on the platform margin. On the inner platform, patchy microbial mounds, mound–flat combinations, and inter‐shoal/microbial mounds are developed in the Gaoshiti area, whereas patchy shoals and shoal–flat combinations are developed in the Moxi area. During the early depositional period of Member IV of the Dengying Formation, the microbial mounds and shoals were developed on the platform margin. The dolomitic flat and inter‐shoal/microbial mounds are mainly developed on the inner platform with little microbial mound and shoal deposition. During the late depositional period of Member IV of the Dengying Formation, large‐scale microbial mounds and shoals are sustainably and stably developed on the platform margin; enlarged dolomitic flat, patchy microbial mounds, and patchy shoals are predominantly developed in the platform interior with inter‐shoal/microbial mounds dying out. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt (CAOB) is one of the largest accretionary orogenic collages in the world with prominent juvenile crust addition, where the southernmost margin of the CAOB located is one hot topic in the international studies. The Dunhuang Block located to the south of the Beishan Orogen is a key position for outlining the tectonic framework of the south margin of the CAOB. However, at present, the tectonic attribution of the Dunhuang Block is still controversial. In this paper, we focus on the origins and protoliths of the meta‐mafic rocks from the Hongliuxia complex in the southern Dunhuang Block for determining the tectonic attribution of the Dunhuang Block. In the field, the meta‐mafic rocks are mainly exposed as tectonic blocks within the metasedimentary rocks displaying the "block‐in‐matrix" fabrics or as tectonic slices juxtaposed by faults. Geochemically, the meta‐mafic rocks could be divided into three groups based on the rare earth elements (REE) and trace elements: the group 1 samples are depleted in the LREE relative to HREE and show flat HREE patterns, similar to the mid‐oceanic ridge basalt; the group 2 samples show flat REE patterns without obvious differentiation between the LREE and HREE, like the oceanic plateau basalt; the group 3 samples are enriched in LREE relative to LREE, and have negative Nb, Ta, and Ti anomalies, similar to the island arc basalt. Conclusively, the protoliths of the meta‐mafic rocks dominantly belong to the oceanic plate components. They were metamorphosed during Early Silurian to Middle Devonian in different depths of the subduction zone documented in previous studies. So, we suggest the Hongliuxia complex is an exhumed Palaeozoic subduction–accretion complex (SAC) formed during the oceanic plate subduction. This result confirms the Palaeozoic subduction event occurred in the Dunhuang region and indicates that the Dunhuang Block is a Palaeozoic Orogen rather than a part of Precambrian continent block. Considering the regional geology context, we speculate the Dunhuang Orogen belongs to the southernmost margin of the CAOB. [ABSTRACT FROM AUTHOR]

As a major tectonic unit along the southwestern rim of the Central Qilian Belt, the Lajishan region plays an important role in the amalgamation of continental plates in the Qilian Orogenic Belt. In this study, zircon laser ablation inductively coupled plasma mass spectrometry for U–Pb dating and Hf isotope analysis, as well as geochemical analysis of intermediate‐acid intrusive rocks from the Lajishan area were conducted. Results show that formation ages of the intermediate‐acid intrusive rocks are 438–452 Ma. Whole‐rock geochemistry results show that the diorite and monzodiorite are metaluminous, low‐ to medium‐K series, and characterized by obvious Nb, Ta, and Ti depletions as well as large‐ion lithophile element and light rare earth element enrichments. The εHf(t) values of zircons from monodiorite range from +2.71 to +10.59 and the two‐stage model ages range from 751 to 1,253 Ma. A large transversal span of εHf(t) values suggests that the source of depleted mantle was mixed with a small amount of older crustal material. The diorite and monzodiorite show a covariant relationship between εHf(t) values and Th/U ratios, which imply the existence of source heterogeneity. The diorites and monzodiorites were most likely produced in an arc setting. The granites are low K in composition and metaluminous to weakly peraluminous. In view of obvious Nb, Ta, and Ti depletions as well as large‐ion lithophile element and light rare earth element enrichments, parent magmas of the granites are suggested to have formed with the participation of crustal source materials. The εHf(t) values of zircons from granite range from +5.82 to +8.90, and the two‐stage model ages range from 861 to 1,057 Ma, indicating that magmas of the granites were mainly derived from partial melting of depleted mantle or juvenile thickened lower crust. The granites were most likely produced in an arc setting and share a similar source with the diorite and monzodiorite. Correlation between major oxides and SiO2 show that during the formation of the three kinds of rocks, crystallization and differentiation both played important roles. Combined with published data from the Central Qilian Belt and its vicinity, our results conclude that the northward subduction of oceanic crust contributed to the formation of an Early Palaeozoic subduction–accretion system in the Lajishan region. This model reveals a tectonic–magmatic thermal event and provides important insights into the tectonic evolution process in the Qilian region, as well as the Central Orogenic Belt during the Early Palaeozoic. [ABSTRACT FROM AUTHOR]

The typical wells in Liaoxi Uplift were selected to conduct studies on high‐frequency sequences and their correspondences with the Milankovitch Cycles in Dongying Formation based on integrated analysis of wireline logs and sieve residue logs. The results of well JZ‐E show that 37 ultra‐short‐term cycles, 13 short‐term cycles, 8 mid‐term cycles, and 5 long‐term cycles are identified. Meanwhile, the correspondences between high‐frequency sequences and the Milankovitch Cycles in Dongying Formation were analysed based on GR curve of well JZ‐E and MATLAB procedure. The correspondences indicate that the Milankovitch Cycles are well preserved in Dongying Formation. The thickness of long‐period cycles caused by eccentricity ranges from 2.7963 to 3.9965 m. The thickness of mid‐term cycles caused by obliquity ranges from 1.5081 to 2.1126 m. The thickness of short‐period cycles caused by precessions ranges from 0.5791 to 1.1269 m. There is a good consistency between high‐frequency sequences and the Milankovitch Cycles in Dongying Formation. The mid‐term cycle, short‐term cycle, and ultra‐short‐term cycle of high‐frequency sequence correspond, respectively, to long‐period eccentricity, short‐period eccentricity, and precession cycle of the Milankovitch Cycles. Lacustrine fluctuations caused by the change in Earth's orbit play a major role in controlling high‐frequency sequences. [ABSTRACT FROM AUTHOR]

The Gucheng area, located in the east of the Tarim Basin, is one of the important gas exploration targets, and the Upper Cambrian dolostone is the main pay layer. The dolostone is considered to be altered by hydrothermal fluids, but the hydrothermal altering degrees are still unclear. In this study we report the petrography and in situ trace elemental data, and try to discuss the hydrothermal fluids and their impact on the Upper Cambrian dolostones. Based on the petrography and CL properties, five types of dolomites are identified. MD1 and MD2 are the matrix dolomites. The crystal size of MD1 range from approximately 30 to 100 μm, while the MD2 is larger than 200 μm. Cement dolomite (CD) occurring only in vugs and fractures is subdivided into three types depending on the CL properties. CD‐zone1 is the core of CD with dull CL colours. CD‐zone2 comprises a bright red CL colour zone and a dull CL colour zone, and CD‐zone3 is the rim of CD dolomite with bright red CL colours. MD2 and CD‐zone1 show light rare earth elements (LREE) depletion, middle rare earth elements (MREE) enrichment and negative Eu anomalies. The REEY patterns of CD‐zone3 dolomite are marked by LREE enrichment and positive Eu anomalies. CD‐zone2 is the transitional mineral phase that shows slightly LREE depletion and negative Eu anomalies. The REEY patterns of CD‐zone1 suggest that CD‐zone1 is likely formed by local redistribution of older dolomites in a closed system. The REEY patterns of CD‐zone3 may indicate a magmatic associated hydrothermal fluid. Based on the petrography and in situ trace elemental data, the Permian magmatic fluid, which is recorded in CD‐zone2 and CD‐zone3 dolomites, may be only limited within fractures, while unlikely significantly altered the matrix dolomite in the Upper Cambrian. [ABSTRACT FROM AUTHOR]

The Kunyushan granitic complex in the Jiaodong Peninsula, East China, is located in the northeast part of the Sulu UHP metamorphic belt. It is the transition belt of the North China Craton and Sulu UHP metamorphic belt. Field relationship and dating results revealed five intrusive phases of the Kunyushan granitic complex were modified into gneissic fine‐grained garnet‐bearing monzogranite (G1), gneissic medium‐ to fine‐grained monzogranite (G2), medium‐ to coarse‐grained monzogranite (G3), medium‐grained monzogranite (G4), and porphyritic coarse‐ to medium‐grained monzogranite (G5). All these phases have similar rock assemblages of peraluminous, calc‐alkaline, I‐type monzogranites. The monzogranites had primitive mantle‐normalized patterns enriched in light rare earth elements (LREE) and lithophile elements (Sr, Ba, and Rb), but depleted in heavy rare earth elements (HREE) and high‐field‐strength elements (Nb, P, and Ti). LA‐ICP‐MS zircon U–Pb dating shows that the crystallization age of the Kunyushan granitic complex extends at least from 157.7–142.0 Ma. The weighted average ages of G1‐G5 were 145.6 ± 1.9 Ma, 145.8 ± 0.5 Ma, 147.2 ± 0.7 Ma, 154.2 ± 0.6 Ma, and 155.0 ± 0.7 Ma, respectively. G5 to G1, from the middle to the edge shows a trend of gradually becoming younger. Zircon grains from different phases have similar 176Hf/177Hf values from 0.281917 to 0.282298, and εHf(t) values from −27.6 to −14.0, with a weighted average of −22.6 ± 0.5, typical of crustal‐derived origin. The corresponding two‐stage model ages TCDM are from 2,910 to 2,066 Ma, with a weighted average of 2,603 ± 31 Ma. Hf–Sr–Nd–Pb isotopes and inherited zircons suggest that the parental magma of the Kunyushan granitic complex was derived from melting of basement rocks of the North China Craton and the Yangtze Craton. The magmatism presumably took place under the background of subduction and back‐arc extension of the Palaeo‐Pacific plate. We infer that the Kunyushan granitic complex was produced by partial melting of the thickened lower crust, through delamination of the thickened lower crust during the Late Jurassic. This magmatic event may mark the beginning of the extensive Mesozoic thinning of the lithosphere in East China. [ABSTRACT FROM AUTHOR]

The timing and mechanism of the closure of the Palaeo‐Asian Ocean are problematic and controversial. To help resolve these problems, we report geochronological, geochemical, and isotopic data from mid‐Triassic adakitic intrusions in the Eastern Tianshan, NW China. U–Pb dating shows that the adakitic intrusions formed at 243–234 Ma. These mid‐Triassic adakitic intrusions are characterized by high Sr/Y and La/Yb ratios, low Yb and Y, and positive εNd (t) (+3.12 − +4.71) and low (87Sr/86Sr)i (0.703956–0.704487) values. However, they have high K and low A/NK values (1.16–1.71), relatively low MgO (0.43–1.81 wt%) contents, and Mg# (44–61), low abundances of compatible elements (Cr = 4.09–16.69 ppm, Ni = 2.02–8.03 ppm), which are different from the typical slab‐melting adakites. These features indicate that they were derived from the partial melting of the relatively depleted thickened lower crust. Our new geochronological, geochemical, and isotopic data integrated with the established amalgamation of nearby arcs lead us to conclude that the adakitic intrusions were most likely generated by partial melting of the tectonically thickened (>40 km) juvenile Dananhu intra‐oceanic arc and, therefore, the Kanguer branch of the Palaeo‐Asian Ocean closed since ca. 234 Ma. [ABSTRACT FROM AUTHOR]

The tight sandstones reservoir of the second member of the Xujiahe Formation (Xu2 member) is gradually becoming the main reservoir for natural gas exploration and exploitation in the Western Sichuan Basin. The tight sandstone is normally deeply buried, where it is controlled by complex diagenetic processes. To gain insights into reservoir exploration of the Xu2 member, the diagenetic history and the impacts of diagenesis on reservoir quality were established using several experimental methods. The sandstones were found to be mainly litharenite, sublitharenite, and feldspathic litharenite. The reservoir quality was characterized by low porosity (3.4% on average), low permeability (0.17 mD on average), low pore throat radius, and high displacement pressure. The tight sandstones experienced a series of significant diagenetic processes, including mechanical compaction, early dissolution, and precipitation of carbonate and siliceous cements during eodiagenesis. They also underwent chemical compaction, late dissolution, and transformation of clay minerals during mesodiagenesis. The silica cementation mainly resulted from chemical compaction, feldspar dissolution, and the transformation of clay minerals. A higher degree of compaction has a vital role in destroying most of the primary pores. Cementation had a significant impact on reducing the porosity and permeability, although chlorite preserved primary pores by slowing the compaction. This study aimed to provide a comprehensive insight into diagenesis and its impact on the reservoir quality of deeply buried sandstone, and provide insights into reservoir exploration and development in deeply buried tight sandstones. [ABSTRACT FROM AUTHOR]

The enrichment mechanism and process of shale oil are key issues in the studies on shale oil. To date, a variety of methods have been applied to describe the characteristics of typical shale oil reservoirs and reveal the potential influencing factors on marine and freshwater continental shale. However, geological characteristics and influencing mechanism of saline lake shale oil reservoirs remain poorly understood. Here, we report our investigation on the petrological, organic geochemical, and pore structure characteristics of the 10th cyclothem of the third member (Eq3410) of the saline lake–formed Qianjiang Formation in Jianghan Basin using X‐ray fluorescence spectroscopy, X‐ray diffraction, field emission scanning electron microscopy, low‐temperature nitrogen adsorption, and high‐pressure mercury intrusion. The shales of Eq3410 contain high average carbonate contents (45.53%) and clay minerals (20.89%), as well as anisometric glauberite, quartz, feldspar, rock salt, and pyrite. The main lithofacies are dolomitic mudstone, argillaceous dolomite, and calcareous mudstone. The shale samples tested yield total organic carbon (TOC) and S1 + S2 values of 1.94 wt% and 10.46 mg HC/g rock, respectively, and are primarily types II1 and II2 kerogen with thermal maturities between 0.5 and 1.0%. The abundance of organic matter in calcareous mudstone and dolomitic mudstone facies of the Eq3410 shales was relatively high. Inorganic pores are the dominant pore types, including intercrystalline pores within the carbonate and clay minerals, while mesopores and macropores contribute most to the pore volume. Better pore structures exist in argillaceous dolomite and dolomitic mudstone facies, and their characteristics are mainly affected by the compositions of dolomite, clay minerals, and glauberite and, thus, the TOC and oil contents of the shale oil reservoir. [ABSTRACT FROM AUTHOR]

While Archean buried hill fractured reservoirs have been found for the first time in the BZ19‐6 Block of the Bozhong Sag in the Bohai Bay Basin, the mechanisms driving their creation and evolution are not well known for low degree of exploration. Using core data, image logs, and our knowledge of the regional geology, we characterized the features and explored the formation mechanisms of these fractures. Our core samples captured two types of fractures: high‐angle shear fractures and low‐ to moderate‐angle tensile fractures. Based on the cross‐cutting relationships, four distinct sets of fractures formed at different stages and related to different tectonic events. The first fracture set (Set I) is high‐angle shear fractures having an E‐W orientation, partially filled by calcite, and was formed by transpressive processes in the Early Yanshanian. The second fracture set (Set II) is characterized by moderate angles, partially filled by asphalt and calcite with variable orientations and a more mesh‐like appearance, formed in an extensional environment in the middle Yanshanian. During transpressive activities in the Late Yanshanian, the high‐angle shear fractures of the third fracture set (Set III) formed with NW‐SE orientations and partially filled by asphalt. The fourth fracture set (Set IV), which occurred in the Early Himalayan, involves high‐angle shear fractures that is oriented in the NE‐SW direction and only part of them are filled by clay minerals. Macroscopic fracture features, orientations, and distribution patterns can significantly alter the nature of a reservoir; the fractures in Set I (E‐W‐oriented) and III (NW‐SE‐oriented) are typically the widest (excluded fills), and they tend to have the greatest impact on the overall reservoir permeability. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) record a large amount of geological information, and serve as a good geological indicator that can effectively predict the palaeoclimate, palaeoenvironment, and palaeotectonic evolution of the sedimentary rocks. The REEs and major elements of 94 marine shale samples obtained from the Late Ordovician to the Early Silurian at Shuanghe (SH) and Qiliao (QL) sections in Sichuan Basin were analysed in this study. Results showed that the major elements of Al2O3, K2O, and TiO2 were mainly controlled by clay minerals associated with terrigenous detrital, but the SiO2 and Na2O were not influenced by clay minerals. In addition, ΣREE values obtained at Shuanghe and Qiliao sections during the Late Ordovician–Early Silurian were close to those of North American Shale (NASC) composites (173.2 ug/g). REEs were characterized by light rare earth elements enrichment, but heavy rare earth elements depletion. Furthermore, the NASC‐normalized REE patterns were similar with a little difference at Shuanghe and Qiliao sections. The following conclusions were drawn by studying REE indicators associated with source, redox condition and the mechanism of organic matter enrichment: (a) ΣREE showed strong positive correlations with TiO2, Al2O3, K2O, and Na2O, but exhibited relatively poor correlations with Fe2O3 and P2O5. These results suggested that REEs in the marine shale mainly occurred in clay minerals, but also were influenced by pyrite, phosphates, and other minerals. (b) Ce/Ce* showed that marine shale during the Late Ordovician–Early Silurian was mainly deposited under anoxic condition in Sichuan Basin and the reduction intensity at Qiliao section was stronger than Shuanghe section. (c) The diagram between La/Yb and ΣREE and the Ce/Ce* values indicated that the detrital minerals in the marine shale were mainly derived from the sedimentary rocks and deposited in the same continental margin environment with a complex composition. (d) The controlling factors of organic matter enrichment were different at Shuanghe and Qiliao sections and the depositional environment controlled the organic matter accumulation and preservation of the organic‐rich marine shale. [ABSTRACT FROM AUTHOR]

The north–north‐east‐trending (NNE) shear zones, which are defined by the Jiekou shear zone and Huangmao shear zone, are located in the eastern Jiangnan Orogen. This article provides kinematics, geochronological data, and dynamics on the Jiekou and Huangmao shear zones and serves as a reference for understanding the tectonic evolution in the South China Block during the Early Palaeozoic orogeny. All shearing signatures show that the Huangmao shear zone is dextral, and the Jiekou shear zone is sinistral. Both shear zones have certain genetic connections. The rocks from the Jiekou and Huangmao shear zones are metamorphosed and deformed into protomylonite and mylonite. Results of the deformation fabrics of feldspar and quartz and quartz c‐axis fabric analysis indicate that the ductile deformation temperatures of the Jiekou shear zone sinistral shearing are ~400–500°C. Dextral shearing with medium–high temperature (450–550°C) is mainly recorded in the Huangmao shear zone. In combination with the previous geochronology, NNE‐trending sinistral and dextral shearing in the eastern Jiangnan Orogen occurred at 465–430 Ma, coeval with the Early Palaeozoic orogeny. Therefore, the geodynamics of the NNE‐trending shear zones is related to a major strain transformation from NW to WNW, which is remotely affected by the intracontinental convergence of Yangtze and Cathaysia blocks during the Early Palaeozoic orogeny. [ABSTRACT FROM AUTHOR]

Open oceanic and coastal marine sedimentary rocks provide abundant valuable records of Cretaceous greenhouse climates, but limited information is available regarding the Cretaceous continental climate regimes. This study presents a palynological report from the middle Zhidan Group based on the ZK1046 drillcore in the southwestern Ordos Basin of central China. A total of 52 types of palynomorphs including 15 genera of spores (20 species) and 24 genera of gymnosperm pollen (34 species) were recognized in the palynological assemblages. Upwards from the base, the palynomorph assemblages in the ZK1046 drill core were not very diverse. They were dominated by bisaccates and proto‐saccate pollen (around 80%), followed by some fern spores and a low content of Classopollis (below 10%). The overall characteristics of the palynomorph assemblages and some biostratigraphically significant palynomorph genera, such as Ephedripites, Jugella, and Rugubivesiculites, suggest that the middle Zhidan Group dates from the middle Early Cretaceous (probably Hauterivian). Vegetation reconstruction points to conifer‐dominated forests with subordinate pteridophyte, Taxodiaceae, and a few Cheirolepidiaceae plants, indicating a relatively stable, cold, and slightly humid environment. This climatic condition was a likely response to the relatively cool global climate during the middle Early Cretaceous. [ABSTRACT FROM AUTHOR]

The south‐east margin of the Xing'an–Mongolian Orogenic Belt (SM‐XMOB) is a tectonic junction that is characterized by widespread Late Palaeozoic to Early Mesozoic igneous rocks. To determine the tectonic settings and provide new constraints on the regional tectonic evolution, petrological, geochronological, geochemical, and Hf isotope analyses have been conducted on the Permian volcanic rocks along the SM‐XMOB. Zircon U–Pb geochronological data indicate that these rocks were formed at 271.4 ± 3.2 Ma and 268.3 ± 3.2 Ma during the Early–Middle Permian. Geochemical results suggest that the volcanic rock samples have 61.5–66.4 wt% SiO2 and 0.98–1.71 wt% MgO, and belong to the calc‐alkaline series, suggesting an affinity with fractionated I‐type granite. They also exhibit positive zircon εHf (t) values ranging from + 8.6 to + 14.7, indicating that the primary magmas were dominantly derived from partial melting of Early Palaeozoic juvenile lower crustal. These volcanic rocks show an enrichment in large‐ion lithophile elements (LILEs; e.g., Rb, Th, and U) and depletion in high‐field‐strength elements (HFSEs; e.g., Nb, Ta, Ti, and P), similar to that from an active continental margin setting. We therefore propose that the widespread Permian volcanic rocks in the SM‐XMOB were closely associated with the southward subduction of the Palaeo‐Asian Ocean (PAO) Plate to the lithosphere beneath the XMOB, and that the PAO had not closed prior to the Middle Permian in the SM‐XMOB. [ABSTRACT FROM AUTHOR]

Internal structures of the pluton may provide key information on magma emplacement mechanism and the relationship with regional tectonics. We present a case study on the Late Triassic Gaoqiao pluton from South Qinling Belt, which was emplaced under a syn‐collisional setting. Multi‐approaches including zircon U–Pb geochronology, field and microstructural observations, anisotropy of magnetic susceptibility analysis was conducted to reconstruct the growth process of the pluton and to investigate the internal structures. Zircon U–Pb geochronology reveals that the pluton is a composite intrusion which was constructed by two successive units with distinct ages (~220 and ~210 Ma). Field observations show that the Gaoqiao pluton and its country rocks recorded abundant evidences of syn‐plutonic deformations, indicating a syn‐tectonic emplacement. Microstructural observations show that the internal fabrics were mainly acquired during the stage from magma flow to high‐T solid‐state deformation. The fabric distributions display 'onion‐skin' patterns on the pluton scale, which are characterized by zoned foliations and lineations. Combined with the syn‐collisional convergence setting, we propose a tectonic‐controlled incremental growth model for the pluton, in which the pluton was successively constructed by the Fujiahe unit and the Hetaoping unit, and the emplacement process of the pluton was controlled by the regional deformation with sinistral transpressional kinematics. Furthermore, the internal fabric patterns of the Gaoqiao pluton were probably formed by tectonic‐controlled helical magma flow, which appears to be common in fabric formation of many other plutons with similar features. [ABSTRACT FROM AUTHOR]

As the largest inland basin in the northeastern Tibetan Plateau, Qaidam Basin has traditionally been thought of as the key region to study the Cenozoic climatic changes in the plateau; however, the information from a palaeobotanic respect is still lacking because of the paucity of the fossil plants. Fossil fruits and foliage of Ailanthus (Simaroubaceae) are reported from the Oligocene Shangganchaigou Formation in the northwestern Qaidam Basin, Qinghai Province, China. All the characters suggest that the fossil materials should be assigned to A. confucii, which is one widely distributed fossil species in the Cenozoic, regarded as the analogue of extant A. altissima. Current materials represent the first fossil record of Simaroubaceae in the northern Tibetan Plateau. Based on the climate requirements of the living A. altissima, the ranges of mean annual temperature (MAT) and mean annual precipitation (MAP) reflected by current fossils from Qaidamare 6.9–17.0°C, and 376–1,383 mm, respectively, compared with the current climate at the fossil site with MAT of −1.03°C and MAP of 60.5 mm. The results indicate that the climate conditions of the fossil site during the Early Oligocene were much warmer and more humid than that of the current. We hereby suggest the warm and moist air could approach the northwestern Qaidam and to accommodate the ecological environment in Early Oligocene. [ABSTRACT FROM AUTHOR]