Search

This paper presents new zircon U–Pb ages and Hf isotope data, and whole‐rock major and trace element geochemical data of Permian igneous rocks from the eastern Songnen Massif (SM) and the western Jiamusi Massif (JM), NE China, to constrain their tectonic evolution. Zircon U–Pb dating indicates that Permian magmatism within the eastern SM can be subdivided into two stages: early Permian (ca. 293 Ma) and middle to late Permian (272–257 Ma). The early Permian igneous rocks comprise a bimodal association of rhyolites, basaltic andesites, and gabbros. The middle to late Permian igneous rocks are dominated by gabbro–diorites, monzodiorites, quartz diorites, monzonites, quartz monzonites, granodiorites, monzogranites, syenogranites, and alkali feldspar granites, along with minor bodies of A‐type quartz trachytes. The Permian felsic magmas originated mainly from partial melting of a relatively juvenile lower crust, whereas the coeval mafic rocks were probably derived from partial melting of a relatively depleted lithospheric mantle that was modified by fossil subduction‐related fluids. The igneous rock associations and their geochemical features, together with data from coeval sedimentary and volcanosedimentary successions, indicate that Permian magmatism within the eastern Songnen and western Jiamusi massifs formed in an extensional environment, similar to a back‐arc setting, related to westward subduction of a Palaeo‐oceanic plate beneath the eastern margin of the Jiamusi Massif. We find no evidence for double‐sided subduction of the Mudanjiang oceanic plate during the Permian. [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]

Hainan Island is a key part of the eastern Tethyan region and contains detailed geological information that can enhance our understanding of the tectonic evolution of this region since the late Palaeozoic. In this paper, we report geochronological, geochemical, and Sr–Nd isotopic data for granitoids from Baomei and Chahe in the northern part of Hainan Island. Three new zircon U–Pb ages of 243.3 ± 1.7 Ma, 237.1 ± 5.1 Ma, and 257.0 ± 4.0 Ma were obtained for these granitoids. The late Permian Chahe granite (257 Ma) is weakly peraluminous to peraluminous, and has rare earth element patterns and Ga/Al and FeOT/MgO ratios typical of A‐type granites formed in an extensional tectonic setting. The Middle Triassic Baomei granitoids (243–237 Ma) are weakly peraluminous, and exhibit a negative correlation between P2O5 and SiO2, which is typical of I‐type granites. All the granitoids have EM II‐type‐enriched mantle Sr–Nd isotopic compositions, which indicate that they were derived from a mantle source that had experienced enrichment and metasomatism. Hainan Island was in an extensional tectonic setting from the late Permian to Middle Triassic when widespread A‐ and I‐type granites were generated. We speculate that Hainan Island was mainly affected by the Tethyan tectonic domain during the Permian–Triassic, which involved closure of the Palaeo‐Tethys Ocean, collision of the Indochina and South China blocks, and subsequent post‐collisional extension. [ABSTRACT FROM AUTHOR]

The Kelameili Ocean was one branch of the Palaeo‐Asian Ocean, the initiation and closure history of which remains elusive. Consequently, they hamper our understanding of the accretionary evolution of the southern Altaids. In this paper, we carried out field mapping and also geochronological and geochemical analyses on the Huangcaopo Group in the northern Harlik Mountains, NW China. Field investigation revealed that "block‐in‐matrix" structure develops with blocks of andesite, limestone, sandstone, and gabbro in matrices of turbidites. Combined with our recent work, our field investigation indicates that the Huangcaopo Group is the southern extension of the Kelameili accretionary complex. A gabbro block (19HAM057) was dated at 500 ± 4 Ma, its geochemical affinity was defined to be similar to arc magmatic rocks. Magmatisms represented by two gabbroic intrusions (19HAM057‐2 and 19HAM048) were dated at the latest Devonian (360 ± 5 Ma) and the latest Carboniferous (299 ± 4 Ma), respectively. Their geochemistry displays enrichments in light rare earth elements (LREE) and large ion lithophile elements (LILE), but depletions in high field strength elements (HFSE, especially Nb and Ta). And a younger gabbroic intrusion (19HAM052) yielded crystallization age of the latest Permian (254 ± 3 Ma), and its geochemistry also shows affinity to arc magmatism. The magmatism represented by the gabbro block (19HAM057) was coeval with the Zhaheba‐Aermantai ophiolite, indicating that it was the product of incipient arc magmatism following subduction initiation in the Kelameili branch of the Palaeo‐Asian Ocean. However, two episodes of gabbroic magmas (19HAM057‐2 and 19HAM048) that intruded the Kelameili accretionary complex from the latest Devonian to latest Carboniferous indicate southward rollback of the subducting Kelameili oceanic lithosphere and resulted in the development of a growing arc. Meanwhile, the youngest gabbroic intrusion (19HAM052) suggests that northward subduction of the Kelameili oceanic lithosphere may have at least lasted to the latest Permian, indicating that the closure of the Kelameili Ocean might have been later than the latest Permian, most likely in the early Triassic. Our new data provide further constraints on the initiation and closure history of the Kelameili Ocean, which shed light on the accretionary evolution of the Altaids. [ABSTRACT FROM AUTHOR]

Several Palaeozoic ophiolitic mélanges distributed in the West Junggar, Xinjiang, are remnants of the Paleo‐Asian Ocean evolution. They are important keys for studying the component, tectonic evolution, and crust–mantle interaction of the Central Asian Orogenic Belt (CAOB). This paper presents petrology, zircon U‐Pb chronology, geochemistry, and Hf isotope data of mafic rocks from the Dalabute ophiolitic mélange, West Junggar. The zircon U‐Pb chronology data of gabbro in the Dalabute ophiolitic mélange can be divided into two groups. The first group magmatic zircons yield a weighted mean age of 389.7 ± 7.7 Ma. It suggests that gabbros of the Dalabute ophiolitic mélange were formed during the period of Early‐middle Devonian, which represents the main period that the Dalabute back‐arc ocean basin expanded. The second group inherited zircons with ages ranging from 910 to 975 Ma were interpreted as Neoproterozoic materials of basement entered its magmatic source. Geochemical characteristics show that the mafic rocks from the Dalabute ophiolitic mélange can be subdivided into alkaline and tholeiite series. Whole‐rock and Hf isotopic data indicate that alkaline basalts have the signatures of typical OIB and formed in the oceanic island or seamount settings related to mantle plume, which were most likely derived from an enriched mantle source. Besides, tholeiitic rocks exhibit the features of MORB and generated in an immature back‐arc basin in the supra‐subduction zone. Their magmas originated from a depleted mantle that had been metasomatized by subduction‐related fluids and contaminated by materials with crustal nature. Therefore, Dalabute ophiolites are supposed to be generated from a back‐arc oceanic basin, which is relate to intra‐subduction and with mantle plumes developed within it. These results jointly provide convincing evidence for the evolution and property of the Dalabute ophiolite in the West Junggar and further supply reference and base for reconstruct the evolutionary history of the CAOB. [ABSTRACT FROM AUTHOR]

The Devonian volcanic rocks are widely distributed in the East Junggar (Xinjiang, NW China), preserving important magmatic records for investigating Palaeozoic tectonic evolution. The Beitashan Formation is mainly composed of pyroclastic rocks and sedimentary rocks in the lower section and intermediate–basic volcanic lava and pyroclastic rocks in the upper section. In this paper, we present geochronological, geochemical, and in situ Lu–Hf isotopic data for Beitashan Formation volcanic rocks from the East Junggar. Zircon U–Pb analyses from a basalt sample by laser ablation inductively coupled plasma mass spectrometry yielded a weighted mean age of 387.8 ± 4.5 Ma, indicating that it was generated in the Middle Devonian. The basic–intermediate volcanic rocks are tholeiitic to calc‐alkalic and are characterized by MgO (2.29–5.91 wt.%), low TiO2 (0.75–1.36 wt.%), and relatively high Al2O3 (15.82–16.73 wt.%). Furthermore, they display enrichment in light rare‐earth elements and large‐ion lithophile elements (such as Ba and Sr) and depletion in Nb, Ta, and Ti, along with slightly positive Eu anomalies (δEu = 0.83–1.15) and Ce anomalies (δCe = 1.00–1.11). In addition, in situ zircon Hf isotopic analyses from basalt samples show εHf(t) values ranging from +4.33 to +15.2, indicating a depleted mantle source with minor crustal contamination. They also show relatively low Nb/Zr (0.04–0.06), Th/Yb (0.67–3.83), and Ba/La (6.79–67.53) and high Ce/Th (7.71–18.94), Ba/Rb (21.39–294.28), and Ba/Th (31.42–486.58). The geochemical data suggest these rocks were likely derived from 10% to 30% partial melting of a garnet‐rich with minor spinel‐bearing Iherzolite depleted mantle metasomatized by slab‐derived fluids, with crustal contamination. Combined with the geological setting and previous studies, we suggest that the northern East Junggar was in a northward‐subducted island‐arc setting in the Devonian. [ABSTRACT FROM AUTHOR]

The Tianshan Belt, which lies in the southwest part of Central Asian Orogenic Belt (CAOB), is characterized by abundant ophiolites or ophiolitic mélanges, which are indicators of the existence of oceanic basin can be used for tracking the tectonic evolutionary history of the orogen. The Bindaban (BD) ophiolitic mélange is located in the Central Tianshan Belt, northwest China, which comprises mainly gabbros, diabases, basalts, basaltic lavas (greenschist), and cherts. This paper presents new zircon geochronology, whole‐rock major and trace elements, and Sr, Nd isotope data for mafic rocks in the BD ophiolitic mélanges. In the eastern part of BD ophiolitic mélanges, one normal (N)‐MORB‐type basalt has a U–Pb zircon age of 265.2 ± 1.8 Ma, and one enriched‐MORB‐type dolorite in the western part of BD ophiolitic mélanges has an age of 425.4 ± 3.9 Ma, respectively, indicating either an existing ocean basin from continental rifting to normal oceanic spreading with a long time span from late Silurian to Permain, or two separate ocean basins that formed in late Permian and late Silurian during the Paleo‐Tianshan Ocean evolution. In particular, the 265.2 ± 1.8 Ma age of N‐MORB‐type basalt from BD ophiolitic mélange suggests the youngest oceanic basin (late Permian) existed in southwest CAOB, which reveals that Paleo‐Asian Ocean might last to late Permian, therefore finally closed in or after the late Permian in the North Tianshan area. [ABSTRACT FROM AUTHOR]

The Jiapigou gold ore belt is located in the northeastern corner of the wedge‐shaped North China Craton and is hosted by Neoarchean basement gneiss and amphibolite, along with late Palaeozoic and Mesozoic granitoids. In this paper, whole‐rock major and trace element geochemistry together with zircon U–Pb ages and Lu–Hf isotope compositions are reported for Late Permian to Triassic igneous rocks from the gold belt. The dominant population of zircons in all these rocks shows oscillatory growth zoning in CL images, and relatively high Th/U ratios (0.10–5.23) that are indicative of a magmatic origin. Zircon U–Pb data indicate that the igneous rocks formed during two major phases: ca. 252 Ma and ca. 230–213 Ma. Geochemically, the Late Permian (ca. 252 Ma) diorites are high‐K calc‐alkaline in composition and low total Fe2O3, MgO, and CaO contents, and represented by enrichment in LILEs relative to HFSEs and HREEs, all of which are indicative of a postcollision high‐K calc‐alkaline granite affinity. In contrast, the Late Triassic (ca. 230–213 Ma) igneous rocks are mainly quartz syenite porphyries, felsites, and granodiorites, and are variable medium‐ to high‐K calc‐alkaline series and exhibit a negative Eu anomaly with A‐type affinities, indicating an extensional environment. In addition, in situ Hf isotopic analyses of zircons from four dated samples reveal that they have εHf(t) values of −3.0 to +2.2, with two‐stage model (TDM2) ages range from 964 to 1,210 Ma, indicating that they probably originated from the partial melting of a dominantly Mesoproterozoic to Neoproterozoic crustal source. On the basis of the geochemical data and regional geological investigations, we further propose that the Jiapigou gold ore belt in the Late Permian was formed in a postcollisional tectonic setting, whereas an extensional tectonic setting in the Late Triassic that caused lithospheric thinning during a postorogenic event. [ABSTRACT FROM AUTHOR]

Carboniferous volcanic rocks are widely distributed in the Junggar Basin and may provide a unique insight into the tectonic history of this basin. In this paper, we focus on the tectonic evolution of the northern Junggar Basin (NJB) using geochronological and geochemical data to establish the diachronous closure model for the Keramaili oceanic basin. The Lower Carboniferous strata in the eastern part (well WC‐1) and the Upper Carboniferous strata in the western part (well Y‐2) of the NJB are composed of a mix of compositional and rock‐type forms. These volcanic rocks are mostly high‐K assemblages characterized by high K (1.73–6.48%), high alkali (Na2O + K2O = 5.04–7.45%), and low TiO2 (0.57–1.06%). They also exhibit various REE concentrations (68.44–168.19 ppm), an enrichment of LREE (LaN/YbN = 4.54–8.09), and small negative Eu anomalies (δEu = 0.74–0.90). The depletion of HFSE and relevant tectonic setting discrimination diagrams demonstrate that these two volcanic associations were formed in a subduction‐related environment. The data also indicate that the high‐K volcanic rocks are derived from a mix of melted subducted sediments and mantle metasomatized by silica‐rich fluids. Although these two sets of volcanic rocks formed in Early and Late Carboniferous, the similar petrographic and geochemical natures suggest similar magma source and tectonic setting. Along with different regional tectonic settings in the NJB during the Carboniferous, we propose an asynchronous subduction of Keramaili oceanic basin, resulting in the inconsistent temporal and spatial distribution of Upper Carboniferous volcanic rocks in the NJB. [ABSTRACT FROM AUTHOR]

West Junggar is located at the southwest margin of the Central Asian Orogenic Belt and includes Silurian pillow basalts of the Mayilashan Formation. The petrogenesis and tectonic setting of these pillow basalts are important for the understanding of the tectonic evolution and metallogeny of the West Junggar area. This paper presents geochronological, geochemical, and whole‐rock Sr–Nd–Pb isotope data from the pillow basalts of the Mayilashan Formation. Zircon LA‐ICP‐MS U–Pb dating of a pillow basalt, which is in conformable contact with the chert, suggests that they were erupted at 437.2 ± 2.2 Ma marking the timing of generation of these rocks as Middle Silurian. Geochemically, all the pillow basalts bear the signature of ocean island basalt (OIB), and are characterized by alkaline affinity with high concentrations of TiO2 (3.28–4.12 wt.%), LILE and LREE enrichment and HREE depletion ((La/Yb)N = 5.5–7.3), with very weak Eu anomalies (Eu/Eu* = 0.96–1.06), and no obvious Nb, Ta, or Ti negative anomalies. Their Sr–Nd–Pb isotopic compositions ((87Sr/86Sr)I = 0.7037–0.7051, εNd(t) = 1.9–2.9, 206Pb/204Pbi = 17.74–18.22, 207Pb/204Pbi = 15.48–15.52, and 208Pb/204Pbi = 36.49–37.86) show Dupal‐like isotopic signature of ophiolites in the southern Paleo‐Asian Ocean. These characteristics indicate that the magmas were derived from a deep OIB reservoir, that is, a depleted but slightly heterogeneous asthenospheric mantle source with ~5–15% partial melting of garnet and spinel lherzolite. Our obtained results, in conjunction with previous published data, allow us to suggest that the alkaline pillow basalts formed in a seamount within an intraoceanic setting, where a larger number of seamounts with different ages occurred in the Paleo‐Asian Ocean. [ABSTRACT FROM AUTHOR]

This paper reports on the petrography, geochemistry, and geochronology of late Mesozoic volcanic rocks in the Wenkutu area of the northern Great Xing'an Range, North‐east China, and discusses the formation age, petrogenesis, and tectonic environment of the Manketouebo, Manitu, Baiyingaolao, and Meiletu formations. Results of Zircon U–Pb dating show that the volcanic rocks in the Wenkutu area were formed during the Early Cretaceous (Manketouebo Formation at 145 ± 1 Ma, Manitu Formation at 141.3 ± 1.7 Ma, Baiyingaolao Formation at 128.7 ± 1.1 Ma, and Meiletu Formation at 129 ± 1 Ma). The Manketouebo, Manitu, and Baiyingaolao formations are dominated by intermediate to acid volcanic rocks that belong to the high‐K calc‐alkaline series, with Eu/Eu* values of 0.38–0.84.They are enriched in light rare earth elements (LREE) and depleted in heavy rare earth elements (HREE). The Meiletu Formation is dominated by intermediate to basic volcanic rocks, belongs to the high‐K calc‐alkaline series, has Eu/Eu* values of 0.89–0.97, and is enriched in Ba, K, Th, U, La, Ce, Sr, Nd, and Hf but relatively depleted in Nb, Ta, Zr, P, and Ti, with no obvious fractionation of LREE and HREE. Results indicate that the magma of the Manketouebo, Manitu, and Baiyingaolao formations had a crustal origin, whereas the Meiletu Formation was sourced from the mantle and subsequently contaminated by crustal materials. The late Mesozoic volcanic rocks in the study area were formed during an orogenic stage, and the compressional environment was caused by subduction of the paleo‐Pacific Plate below the Asian continental plate. [ABSTRACT FROM AUTHOR]

The Eastern Yanbian area, Northeast China is tectonically located in the easternmost margin of the Xing'an Mongolian Orogenic Belt, which is a key area for providing important evidence of mineral deposits to constrain the tectonic evolution of the Paleo‐Asian Ocean. Five quartz‐vein‐type scheelite deposits have been identified in the eastern Yanbian area. These deposits are hosted within the late Palaeozoic metamorphic and granitic rocks and form under the identical hydrothermal mineralization. Zircon U–Pb ages and whole‐rock geochemistry of the ore‐hosting biotite granite and Sm–Nd ages of scheelite crystals within quartz veins are presented in this paper. Zircon U–Pb dating of the biotite granite yields a weighted mean age of 251.9 ± 2.2 Ma (mean standard weighted deviation (MSWD) = 4), and Sm–Nd dating of scheelite samples yields an isochron age of 251.7 ± 2.9 Ma (MSWD = 0.87), which constrains the scheelite mineralization in Eastern Yanbian to the late Permian. Our results, integrated with published geochronological data, indicate three periods of Phanerozoic W mineralization in Northeast China, (a) Cambrian, (b) late Permian (this work), and (c) Jurassic. Geochemical data reveal that the biotite granite is a calc‐alkaline I‐type granite, and it exhibits enrichment in large‐ion lithophile and light rare earth elements and depletion in high‐field‐strength and heavy rare earth elements (especially in Nb and Ta), consistent with the characteristics of arc magma. The subduction‐related biotite granite intrusion and quartz‐vein‐type scheelite mineralization together indicate that the Paleo‐Asian Ocean had not closed before the late Permian in the Eastern Yanbian area, and its final closure occurred in the Early‐Middle Triassic. The late Permian subduction of the Paleo‐Asian Ocean induced the partial melting of the lower crust, thus forming the magmatic arc activity and related quartz‐vein‐type scheelite mineralization, which clearly justifies the proposed tectonic–metallogenic model. [ABSTRACT FROM AUTHOR]

The Kaiyuan tectonic mélange makes up the western part of the Kaiyuan–Yanji Accretionary Complex Belt, NE China, and there has been a long‐standing controversy about its age and tectonic setting. In this paper, we present new zircon U–Pb ages and geochemical data for the mafic rocks of the Lujiapuzi Formation in the Kaiyuan tectonic mélange, and these data provide insights into the tectonic setting during the late Paleozoic and the evolutionary history of the Paleo‐Asian Ocean in the eastern segment of the Central Asian Orogenic Belt (CAOB). SHRIMP U–Pb dating of zircons from samples of albite–actinolite schist and amphibolite yielded a crystallization age of 258 ± 5.5 Ma for the protoliths, suggesting that the protoliths formed during the late Permian. The albite–actinolite schists and amphibolites have similar geochemical characteristics, and they represent metamorphosed basaltic volcanic rocks. Major, rare earth and trace element data show that the mafic rocks have a close affinity with mid‐ocean ridge basalt. REE petrogenetic modelling indicates that the primary magma was generated through the partial melting of a mixed garnet‐ and spinel‐bearing mantle source, and assimilated crustal material and underwent crystal fractionation during ascent. The geochemical features and inherited/xenocrystic zircons in the mafic samples indicate that they formed in a tectonic setting similar to the back‐arc basin. These new findings, together with other previously published data, indicate that the Paleo‐Asian Ocean still existed in the eastern segment of the CAOB during the late Permian to Early Triassic. The Kaiyuan tectonic mélange formed during the Middle Triassic, and its formation may represent the timing of final closure of the Paleo‐Asian Ocean. [ABSTRACT FROM AUTHOR]

The Early Precambrian magmatism in the Archean–Palaeoproterozoic basement Yudongzi Complex is critical for understanding the early crustal formation and evolutionary history of the Yangtze Block in the South China Craton. In this paper, combined zircon UPb geochronological, zircon Hf isotopic, and whole‐rock geochemical studies are carried out on the granitoid gneisses from the Yudongzi Complex, north‐western Yangtze Block. The magmatic zircons from the granitoid gneiss yield a UPb upper intercept age of 2,477±18 Ma, interpreted as the crystallization age of the granitoid gneiss. The granitoid gneiss samples are characterized by high Al2O3 contents, moderate to high Sr/Y, (La/Yb)N and Na2O/K2O ratios, no obvious Eu and Sr anomalies, and depleted Nb, Ta, and Ti values that are similar to those of Archean trondhjemite–tonalite–granodiorite (TTG) suites, indicating that the investigated rocks belonging to TTG‐series rocks. They display pronounced enriched‐LREE patterns with high La/Yb values and relatively high Zr/Sm and Eu/Eu* but low Nb/Ta and Dy/Yb ratios, implying that these rocks were formed by partial melting within amphibolite‐facies conditions with mainly residual amphibole, garnet, and accessory rutile in the magma source. These rocks also display apparently low MgO, Mg#, Ni, and Cr contents, suggesting derivation from partial melting of thickened ancient lower crust. Zircon εHf(t) values from the granitoid gneiss sample vary from −10.1 to −6.9 with TDM2 of ca. 3.59–3.40 Ga, what demonstrates their crustal source nature as well. Thus, taking all these factors together, we propose that the ca. 2.48 Ga granitoid gneisses in the Yudongzi Complex might have been produced by partial melting of ancient crust material under amphibolite‐facies conditions, with primarily residual assemblages of amphibole, garnet, and attached rutile. Taking together our new data and such from previous studies, the Yangtze Block has been probably involved into a significant reworking of ancient crust event during the Early Palaeoproterozoic time. [ABSTRACT FROM AUTHOR]

The Late Palaeozoic Solonker‐Xar Moron‐Changchun‐Yanji Suture (SXCYS) is considered to mark the location of the final closure of the Paleo‐Asian Ocean, which separated the North China Craton to the south and the amalgamated blocks to the north in Northeast China. There has always been controversy about its eastern extension in Northeast China and the final closure time of the Paleo‐Asian Ocean. To explore this issue, we collected gabbro and quartz‐diorite samples in the Hunchun area for the genesis of mafic magma and age dating, and five groups of Permian to Triassic sandstones belonging to both sides of the potential suture locations in the middle and east Jilin Province for the provenance analysis to discuss the final closure time of the Paleo‐Asian Ocean and the possible positions of the eastward termination of the SXCYS. The gabbro reveals a Middle Permian concordia average age of 266.9 ± 5.2 Ma, and the quartz diorite reveals a Late Permian Concordia average age of 258.8 ± 4.8 Ma. Lithological and geochemical analysis reveal the two rock samples belong to low‐K arc tholeiites from the oceanic island and calk‐alkaline volcanics from the active continental margin, respectively, which implies that during the middle to late Permian, the SW margin of the Jiamusi–Khanka Block (JB) continuously experienced the subduction process from the Paleo‐Asian Ocean Plate. The final closure time of the Paleo‐Asian Ocean should be later than the Late Permian. Meanwhile, four groups of sandstone from the east Jilin reveal typically Jiamusi–Mongolia Block (JMB) provenance features, with age components of ~500 Ma, ~0.9–1.5 Ga implying that the Wangqing, Hunchun, Kaishantun area belongs to the northern part of the SXCYS from late Early Permian to Middle Triassic, with youngest age components of 288.2 ± 2.8, 275.5 ± 1.8, 250 ± 1.7, and 244.9 ± 1.7 Ma, respectively. The late Early Permian sandstone from the middle Jilin reveals the youngest age component of 273.8 ± 3.4 Ma and the age component of 487 ± 3 Ma also revealing JMB feature. Comparing to previous studies, we propose that the Paleo‐Asian Ocean finally closed during Middle to Late Triassic. A possible ENE fault separates the eastern extension of SXCYS into two parts, which means the possible position of the eastward extension of the SXCYS should go along the Wangqing‐Kaishantun with NNW direction in the west, Hunchun‐Laoheishan with NW direction in the east. [ABSTRACT FROM AUTHOR]

Volatile element abundance is a crucial factor triggering mineralization and controlling the enrichment of molybdenum in porphyry deposits. The Chalukou deposit is the largest porphyry Mo deposit in NE China, with an average grade of 0.087% Mo. In this contribution, we present petrology, bulk geochemistry, zircon U–Pb geochronology and Lu–Hf isotopes, and apatite geochemistry for the Chalukou deposit. The intrusive rocks include pre‐mineralization monzogranite, syn‐mineralization quartz porphyry, fine‐grained porphyry and granite porphyry, and post‐mineralization monzogranite and feldspar porphyry. These granitoids are metaluminous to peraluminous, and belong to alkali‐calcic to calc‐alkalic series. Zircon εHf(t) values of granitoids range from +0.2 to +5.7 with corresponding Hf crustal model ages of 805–1170 Ma, indicating a Mesoproterozoic juvenile crustal source modified by mantle‐derived magma. They are characterized by logf(O2) of −16.1 to −9.4, with an average of −12.5, ΔFMQ of +0.8 to +7.9, with an average of +4.5, showing a relatively high oxidation state for the syn‐mineralization magma. The apatites in quartz porphyry have the highest F contents, ranging from 3.61 to 4.62 wt%. At Chalukou, F‐rich magma is conducive to the convection of magma and promotes the efficient separation of differentiation magma, making the magmatic‐hydrothermal fluid circulate many times, eventually resulting in the accumulation of ore‐forming materials on the top of the magma chamber and gradually aggravating mineral enrichment processes. [ABSTRACT FROM AUTHOR]

Petrography and geochemical data of the Late Cretaceous clastic rocks in the northern Songliao Basin were used to infer the provenance and chemical weathering history. Petrographic data indicates that the composition of the sandstones is mainly quartz (34.48–50.43%), feldspars (14.16%–24.07%) and lithic fragments (33.91%–45.9%). Similar REE patterns and trace element ratios suggest that both the sandstones (LaCN/YbCN = 12.97; Eu/Eu* = 0.81; Th/Sc = 1.10) and mudstones (LaCN/YbCN = 10.02; Eu/Eu* = 0.71; Th/Sc = 1.10) were derived from a similar source area with felsic volcanic rocks as dominant contributors. The main provenance area is probably the eastern Zhangguangcai Range, the north‐eastern Lesser Xing'an Range and the south‐eastern Songliao Basin. A modelled mixture composed of 65% granodiorite in the Lesser Xing'an Range, 30% granite in Zhangguangcai Range and 5% epidiorite in the south‐eastern Songliao Basin, can be interpreted as the potential source compositions for the clastic sediments. This conclusion is reinforced by the major element of geochemistry composition and sandstone petrography. Relatively low Chemical Index of Alteration (CIA) values in mudstones (48.14–69.26) and sandstones (50.78–59.96) indicate mild chemical weathering conditions in the source area. The chemical weathering history suggests that a cold and arid climate prevailed during the Late Cretaceous. [ABSTRACT FROM AUTHOR]

The Suolong gold deposit is in the eastern part of the Min‐Li metallogenic belt within the West Qinling Orogen. It is hosted in Lower Permian sandstone and siltstone. The gold mineralization is fault‐ and joint‐controlled. Four hydrothermal stages of mineralization, including the sulphide‐quartz stage, the arsenian pyrite‐quartz stage, the polymetallic sulphide‐quartz‐carbonate stage and the sulphide‐carbonate stage, were identified. Here we report results from fluid inclusion studies and C‐H‐O‐S‐Pb isotopes to get insight into the characteristics of mineralization and ore genesis. Fluid inclusion results indicate that the ore‐forming temperatures and salinities were in the range from 135 to 419°C and 0.18 to 15.27 wt.%, respectively. The δ34S values of pyrite, arsenopyrite and pyrrhotite varied in the 5.3‰–11.4‰ range, suggesting that sulphur originated from stratum sulphur. Lead isotopic compositions of sulphide (206Pb/204Pb = 18.344–18.418, 207Pb/204Pb = 15.628–15.701, 208Pb/204Pb = 38.508–38.743) indicate an upper crust source for Pb. The δ18OH2O‐SMOW and δDSMOW values range from 1.01‰ to 10.31‰ and −116.0‰ to −29.2‰, respectively, indicating that metamorphic water was the source of ore‐forming fluids. The δ13CPDB values (−11.4 to −2.1‰) show that the carbon in the ore‐forming fluids originated predominantly from a deep source. Our data suggest that the Suolong gold deposit is an orogenic gold deposit related to the subduction of an oceanic plate along the Mianlue belt. [ABSTRACT FROM AUTHOR]

The Shaolang River metallogenic belt in Inner Mongolia is one of the main lead‐zinc polymetallic belt on the northern margin of the North China Plate. The granodiorites, which are closely coexisting with lead‐zinc veins in deposit, are extensively developed. Previous geochronological research results show that the dikes and veins in the metallogenic belt belong to the products of magmatic hydrothermal activity in the middle Yanshanian, so the genesis of the metallogenic belt deposit is generally considered to be a hydrothermal vein type deposit related to sub‐volcanic dikes. We obtained zircon LA‐ICP‐MS U–Pb ages and Hf isotopic compositions of granodiorites, which are widely distributed in the deposit and were considered to be closely connected with the genesis of the deposits. The zircon U–Pb ages are 419.4 ± 1.4 Ma and 424.5 ± 4.1 Ma for the granodiorites, respectively, and they formed in the late Silurian. The geological and geochemical data indicate that the granodiorites are consistent with the geochemical characteristics of typical adakite. All εHf(t) values of the granodiorites are minus, on the zircon Hf isotope age diagram, εHf(t) are below the evolution curve of chondrite. The two‐stage model ages (tDM2) are 2.45 ~ 2.79 Ga and 1.87 ~ 2.29 Ga, respectively, showing rock‐forming materials mainly derived from the Paleoproterozoic and earlier crustal partial melting, and there may have been mantle‐derived magma underplating of the lower crust. Combining with the previous regional research, it is concluded that the granodiorites were formed during the extinction of the island arc under the background of subduction of the Paleo‐Asian Ocean and North China Craton. Because of the 125 ~ 170 Ma metallogenic age, we concluded that the granodiorites in the ore areas have no obvious relationship with the deposit genesis. However, it provided the advantageous space for the formation of the lead‐zinc veins, it can be regarded as an important prospecting indicator in metallogenic belt. [ABSTRACT FROM AUTHOR]

The Banjing tungsten deposit, which has been discovered recently, is located in the northernmost part of the Dabu pluton, southern Jiangxi Province, China. In this study, zircon LA‐ICP‐MS U–Pb dating of the fine‐grained porphyritic biotite granite indicate that it was formed in the early Yanshanian (159.4 ± 2.5 Ma–161.6 ± 0.8 Ma). Whole‐rock geochemical studies have shown the fine‐grained porphyritic biotite granite has SiO2 of 75.82%–76.84%, Al2O3 12.50%–12.87%, MgO 0.07%–0.20%, and CaO 0.64%–1.09%, with A/CNK of 1.017–1.038. It has a total rare earth elements content of 93.9–118.9 ppm with strong negative Eu anomalies (δEu = 0.021–0.081). The biotite granite is enriched in Rb, Th, U, Nd and depleted in Ba, Sr, Nb, Ti. These data suggest the Dabu pluton belongs to S‐type granite. This pluton has ISr of 0.71212–0.72929 and εNd(t) from −9.60 to −10.62 with Nd model ages concentrated in 1732–1838 Ma. These isotopic data in combination with zircon Hf isotopes suggest the biotite granite originated from partial melting of the Middle Proterozoic metamorphic supracrustal rocks in South China, with a minor contribution from juvenile crust. Meanwhile, this study has obtained Re–Os isochron ages of the intrusion‐related and quartz vein‐type molybdenum mineralization are 156.3 ± 2.7 Ma and 157.0 ± 1.1 Ma in the Banjing tungsten deposit, respectively. Sericite from the greisen‐type tungsten‐molybdenum ore has an 40Ar–39Ar plateau age of 156.4 ± 1.0 Ma, interpreted as the formation age of this deposit. Collectively, the Banjing tungsten deposit is considered as a product of the early Yanshanian large‐scale peak mineralization in South China, which was formed in an extensional intracontinental environment caused by the subduction of the Palaeo‐Pacific Plate. [ABSTRACT FROM AUTHOR]

The Bayan Obo–Duolun–Chifeng–Kaiyuan (BDCK) Fault is considered the boundary between the North China Craton (NCC) and Central Asian Orogenic Belt (CAOB). However, the site of this boundary from Duolun to Chifeng and Kaiyuan remains highly controversial. Here, we present an integrated study of petrology, whole‐rock geochemistry, and zircon U–Pb and Sr–Nd–Hf isotope compositions for tonalites and amphibolites in the Bainaimiao arc belt (BAB) to better constrain the northern NCC margin. The tonalites are similar to NCC tonalite–trondhjemite–granodiorites (TTGs), characterized by relatively high Na2O/K2O and Sr/Y ratios and fractionated rare earth element (REE) patterns, with high light REE (LREE) but low heavy REE (HREE) concentrations. Laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) zircon U–Pb dating yields formation ages of 2599–2674 Ma, with a weighted average of 2649.6 ± 3.7 Ma. The εHf(t) values (3.5–7.5), two‐stage model ages (2673–2793 Ma), whole‐rock positive εNd(t) values (1.3–1.9), and two‐stage model ages (2841–2880 Ma) suggest that the Neoarchean tonalites likely originated from remelting of thickened Meso‐Neoarchean mafic crust. LA–ICP–MS U–Pb isotope data reveal that the amphibolites formed at ~2610 Ma. They have high‐Fe tholeiitic compositions and are close to normal mid‐ocean ridge basalt (N‐MORB)‐like rocks, indicating that they were generated from partial melting of the depleted mantle. The existence of Neoarchean basement rocks, combined with seismic and isotope data, suggests that the Jiefangyingzi area is part of the Trans‐North China Orogen (TNCO) in the NCC rather than part of the CAOB and that the northern boundary of the NCC in Chifeng is located north to the Jiefangyingzi area. [ABSTRACT FROM AUTHOR]

The Pushi area of South‐west China features a large area of purple soil that formed by the weathering of Cretaceous terrigenous clastic rocks. In this study, four vertical profiles of the purple soil (P1, P2, P3, and P4) derived from different pedogenic parent rocks were investigated. Specifically, the chemical weathering intensity and element migration, enrichment, and differentiation characteristics were analysed and the influencing factors of chemical weathering were explored. According to the discrimination map of major and trace elements and content characteristics of rare earth elements, the soil profiles are controlled by complex chemical weathering processes. Various geochemical parameters and indicators exhibited good correlation, and the chemical weathering intensity of the profiles followed the order P1 (mudstone) > P3 (silty mudstone) > P4 (argillaceous siltstone) > P2 (sandstone). The overall chemical weathering intensity of argillaceous rocks was slightly higher than that of sandstone, and the four profiles generally reflected medium to strong chemical weathering. The migration, enrichment, and differentiation characteristics of geochemical elements were found to be mainly affected by different chemical weathering intensities and stages, followed by leaching deposition. The chemical weathering characteristics varied for the four profiles with different pedogenic parent rocks, which could be mainly attributed to internal factors such as the lithology of the pedogenic parent rock and external topographic factors such as altitude. [ABSTRACT FROM AUTHOR]

New LA‐ICP‐MS zircon U–Pb geochronology, whole‐rock geochemistry and Hf isotopic data have been studied on the Taipingtun granite porphyry to determine its petrogenesis and constrain the tectonic setting of the central Great Xing'an Range, northeastern China, during the Early Cretaceous. The results of zircon U–Pb dating suggest that the Taipingtun granite porphyry was emplaced during the Early Cretaceous (122–123 Ma). Geochemically, the granite porphyries have high contents of SiO2 (75.76–78.66 wt%) and (K2O + Na2O) (7.14–8.29 wt%), and low Al2O3 (11.09–12.81 wt%) and CaO (0.15–0.29 wt%), indicating peraluminous and high‐K calc‐alkaline features. Additionally, these rocks are characterized by strong Th, U, K, and Rb enrichment; Ba, Sr, P and Ti depletion; high Ga/Al ratios (10,000*Ga/Al = 2.60–4.92) and negative Eu anomalies (δEu = 0.02–0.13). According to the zircon saturation thermometer results, zircon saturation temperatures range from 756 to 959°C with an average of 823°C, displaying high magmatic temperature for the parental magma. Based on these geochemical characteristics, it can be reasonably inferred that the initial composition of the Taipingtun granite porphyry melts exhibited an A‐type magmatic affinity. Furthermore, zircon grains within the Taipingtun granite porphyry have εHf(t) values of 7.12 to 10.99 and TDM2 model ages of 476–726 Ma. The Ba/La (average 3.89), Nd/Th (average 2.25), Zr/Hf (average 22.55), Ti/Zr (average 2.96) and Rb/Sr (average 4.21) values display the characteristics of crust‐derived magmas. Moreover, these rocks have obviously negative Eu anomalies (average 0.13) and relatively high Y (average 37.83 ppm) and Yb (average 4.15 ppm) contents, suggesting the magmas are generated in a low‐pressure environment. Thus, we consider the primary magmas of the Taipingtun granite porphyry may have been predominantly derived from the partial melting of juvenile crustal rocks at low pressure. Combined with the regional geological data, we suggest that the Taipingtun granite porphyry was formed in an extensional tectonic environment, and possibly related to the subducted Palaeo‐Pacific Ocean Plate in the Early Cretaceous. [ABSTRACT FROM AUTHOR]

The Kalatag area contains many intrusive rocks of Late Ordovician to Permian age and hosts polymetallic deposits that are associated with magmatism. It is a key area for revealing the nature and genesis of the Palaeozoic rocks in East Tianshan. The intrusive rocks of different periods preserve useful information regarding the tectonomagmatic history of the Kalatag area. Zircon U–Pb geochronological, Hf isotopic, Sr–Nd isotopic, and whole‐rock geochemical analyses are reported for the intrusions from the Meiling ore district, Yudai ore district, and Kalatag pluton to reveal their petrogenesis and geodynamic setting. The LA–ICP–MS zircon U–Pb analyses suggest that the quartz diorite from the Kalatag pluton formed at 420–432 Ma, and the quartz diorite porphyry from the Yudai ore district formed at 436–439 Ma. The zircons from the quartz diorite and quartz diorite porphyry mainly yield high εHf(t) values (12.2–16.2) and very young Hf model ages (TDM = 0.41–0.56 Ga; TDMC = 0.49–0.56 Ga), which are consistent with a depleted mantle origin. The geochemical characteristics of the granites and quartz diorites from the Kalatag pluton and diorite porphyry from the Meiling ore district exhibit typical subduction‐related features such as enrichment in LILEs and LREEs and depletion in HFSEs. These diorites have moderate Mg# (30–47), positive εNd(t) values (4.2–5.6), and young Nd model ages (0.62–0.83 Ga), which are consistent with a depleted mantle origin that is accompanied by limited crustal assimilation. Based on the regional geology and geochemical evidence and previous studies, the Ordovician–Carboniferous rocks from the Kalatag area are considered to have formed in an island‐arc setting and were probably formed by a subduction event. [ABSTRACT FROM AUTHOR]

The Dabie Orogen constitutes the eastern part of the Qinling‐Tongbai‐Hong'an‐Dabie orogenic belt, however, whether it has involved into the early Palaeozoic subduction–related event as well‐recorded in the western part is still in debate. This study provides new petrological, geochronological and geochemical data for the Beilou and Mafan plutons in the Dabie‐Hong'an orogens. The Beilou pluton is dominated by granite, some of which have been strongly deformed to form mylonites. The Beilou pluton was emplaced at ca. 490 and ca. 450 Ma, whereas the Mafan pluton was emplaced at 450–430 Ma. The whole‐rock major‐ and trace‐element analyses results indicate that both plutons are depleted in high‐field‐strength elements and heavy rare earth elements. The Beilou pluton also has positive whole‐rock εNd(t) values and generally positive zircon εHf(t) values, whereas all but one of the Mafan pluton samples yield positive whole‐rock εNd(t) and consistently positive zircon εHf(t) values. All of the samples have low (87Sr/86Sr)i ratios. These data indicate that these plutons are formed from magmas generated by the partial melting of metasomatized mantle wedge material with minor additions of crustal materials, representing arc magmatic rocks associated with subduction. Detailed detrital zircon dating of flysch sequences of the Foziling Group within the Dabie Orogen indicates that the early Palaeozoic magmatic rocks had once been distributed in the whole Orogen, although only the Beilou pluton now is exposed in the western Dabie Orogen. [ABSTRACT FROM AUTHOR]

The Middle Permian black shales from the eastern Junggar Basin of northern Xinjiang, north‐west China are one of the richest and thickest lacustrine hydrocarbon source rocks in China. The palaeoenvironmental settings and controlling factors of organic matter accumulation along the margins of the Middle Permian lacustrine basin remain unclear, although the same works have been undertaken in the centre of the Middle Permian lacustrine basins. Here, we performed a combination of mineralogical and geochemical analyses on the black shales of the Middle Permian Pingdiquan Formation from the eastern margin areas of the Junggar Basin. The results show that the Pingdiquan Formation black shales in the study areas are organic‐rich, with total organic carbon (TOC) contents of 0.74–17.61 wt% (avg. 5.81 wt%). Salinity proxies including Sr/Ba and Rb/K ratios, combined with traces of gypsum and halite in a few samples, suggest brackish to saline water conditions. Palaeoclimate proxies indicate a warm‐humid environment during the deposition of the Pingdiquan Formation black shales. The redox proxies V/(V + Ni), V/Cr and U/Th ratios, and Eu and Ce anomalies together indicate dysoxic‐anoxic conditions of lake water. Strong positive correlations between palaeoproductivity proxies (P/Al, Ni/Al, Cu/Al, and Zn/Al) and TOC contents imply that palaeoproductivity may have played an essential role in organic matter accumulation during the deposition of the black shales. In contrast, negative correlations between terrestrial detrital input proxies (Al and Ti) and TOC contents indicate that terrestrial detrital input may have acted as a diluent to organic matter accumulation. Additionally, although the correlation between redox proxies [V/(V + Ni) and U/Th] and TOC contents is not straightforward, dysoxic‐anoxic conditions of lake water are an essential prerequisite for organic matter accumulation in the Pingdiquan Formation black shales. [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]

Ophiolite provides key information on subduction–accretion processes along convergent plate margins. The Wunuer ophiolite in the Great Xing'an Range of NE China was considered to be an accreted fragment of the Palaeo‐Oceanic Plate. Based on field investigation, we evaluate the petrotectonic assemblages, geochemical features, and formation age of the ophiolite, which comprises gabbro, diabase, metabasalt, and radiolarian bedded chert with serpentinized amphibole‐pyroxene peridotites. Zircon U–Pb dating shows ages of 346 ± 6 Ma and 341 ± 6 Ma suggesting the timing of formation of the ophiolite as Early Carboniferous. The ophiolitic mafic rocks in Wunuer can be divided into two types based on their geochemical features. Type I is characterized by high Ti and low Al, with weakly negative Nb‐Ta and positive Pb anomalies and low light rare earth elements (LREE). These rocks display MORB‐like features, and correspond to partial melting product of depleted mantle. Type II has low Ti, high Al, notably negative Nb‐Ta and positive Pb anomalies, and is obviously enriched in LREE, large‐ion lithophile elements (LILE), and depleted in high‐field‐strength elements (HFSE), characterized by IAB‐like features, and may be formed by partial melting of more depleted mantle, which was strongly metasomatized by subduction fluids, resulted in high LILE/HFSE. The two types of ophiolites belong to SSZ type, obviously influenced by subduction, and their tectonic setting is inferred to be within a spreading ridge in a back‐arc basin. Combined with regional geological background, the Wunuer ophiolite probably represents a shrinking ocean basin and may be the late product of the long‐term and mature back‐arc basin, related to the terminal stage of ridge spreading within the back‐arc basin. [ABSTRACT FROM AUTHOR]

The Neoproterozoic granites along the western margin of the Yangtze Block are crucial for understanding the evolution of the Rodinia supercontinent and crust–mantle interaction. Based on a regional geological survey, this study analyses the zircon U–Pb geochronology, Lu–Hf isotope, whole‐rock Sr–Nd isotopes, and geochemistry of the Maoniushan granites along the western margin of the Yangtze Block and discusses the Neoproterozoic tectonic evolution history of the Mianning–Maoniushan belt. The results show that the Maoniushan granites belong to calc‐alkaline weak peraluminous monzogranite. The granites are enriched in large‐ion lithophile elements (i.e., Rb, Sr, Cs, and Ba) but relatively depleted in high‐field‐ strength elements (i.e., Nb, Ta, U, and Th). The zircon saturation temperature (TZr) ranges from 628 to 766°C, and the weighted average 206Pb/238U ages of zircon range from 771 ± 30 to 759 ± 26 Ma. The εHf(t) values range from −2.0 to +7.2, with TDM2 model ages ranging from 1,797 to 1,208 Ma. The whole‐rock Sr–Nd isotopic data show (87Sr/86Sr)i ratios of 0.7039–0.7093, and the εNd(t) values range from +1.25 to +1.76 with TDM2 model ages ranging from 1,303 to 1,344 Ma. These findings indicate the presence of deep Mesoproterozoic crustal materials in the source area. The Maoniushan monzogranites belong to I‐type granite, which is formed by the partial melting of the basic rocks and pelites in the ancient lower crust due to the metasomatism of fluids from the subducted oceanic crust. The Maoniushan monzogranites may be formed in the process of transformation from regional thickening to thinning under the oceanic crust subduction setting. [ABSTRACT FROM AUTHOR]

The Guide Basin, located in the West Qinling orogen of central China, is a typical geothermal field. However, the granodiorites occurring in the Zhacanggou area have been poorly restricted. Herein, we report new isotopic compositions of whole‐rock major‐trace elements, zircon U–Pb, and Lu–Hf, on the host granodiorites and their microgranular enclaves (MEs) in the Zhacanggou area. Zircon U–Pb dating for the host rocks (porphyritic granodiorite and granodiorite) revealed ages of 230.5 ± 1.4 Ma and 229.0 ± 1.6 Ma, similar to those (230.5 ± 1.5 Ma and 231.4 ± 1.4 Ma) of the MEs. Zircon Hf isotope analyses for the granodiorite and MEs yielded εHf(t) values from −11.0 to −1.5 and from −7.8 to −0.7, with corresponding TDM2 ages of 1,355–1,959 and 1,304–1,755, respectively. The MEs possess plagioclase phenocrysts, acicular apatites, and chilled borders. They were characterized by relatively low SiO2 (58.39–65.24 wt%) and high Cr, Ni, and MgO contents, leading to relatively high Mg# values (44–59) and low Sr/Y (14.23–19.84) ratios. The host granodioritic rocks show similar adakitic geochemical characteristics with SiO2 = 64.23–68.57 wt%, MgO = 1.29–2.22 wt%, Mg# = 48–53, Sr = 340–596 ppm, Y = 11.3–13.7 ppm, Sr/Y = 28.39–47.89, and no obvious Eu anomalies. These geochemical and isotopic data, combined with the mineralogical features, indicate that the granodiorites in the Zhacanggou area were produced by the mixing of high‐Mg# melts originating from an enriched lithospheric mantle source, and felsic magmas deriving by the partial melting of the normal lower continental crust with the tectonic regime transition from a syn‐collision to a post‐collision setting. [ABSTRACT FROM AUTHOR]

The Kamust sandstone‐hosted uranium deposit was recently discovered within the Middle Jurassic Toutunhe Formation of the eastern Junggar Basin. In this study, polarizing microscope and scanning electron microscope observation, electron microprobe analysis, and laser ablation inductively coupled plasma mass spectrometry measurement were carried out to define the petrology, mineralogy, and geochemistry of these sandstone‐hosted uranium ores. In addition, sulphur isotope signatures for the associated ore‐stage pyrites and the ore‐forming age were determined. The results show that the mineralized sandstones, which exhibit excellent reducibility with abundant organic matter and pyrites, are characterized by the secondary accumulation of uranium and are slightly enriched in rare earth elements (REE) and light REE (LREE). The uranium deposits are mainly composed of a large amount of uraninite, followed by some coffinites and uranium‐bearing titanium minerals and very few sorptive uranium‐bearing materials. Uranium minerals primarily exist within the interior and edge of clastic particles in colloidal, dispersed, and vein form, and some are closely interweaved with the colloidal and framboidal pyrites and carbonaceous detritus. Both uraninite and coffinite are strongly enriched in REE and LREE, as determined by in situ trace element measurements. Moreover, the δ34S values of the associated ore‐stage pyrites mostly range from −41.66 to −19.33‰, indicating biological origin, and light 32S demonstrates the relatively low‐temperature and open‐system mineralization processes related to the microbial anaerobic action on the organic matter. One of the δ34S values (6.88‰) is possibly caused by Rayleigh isotope fractionation due to the utilization of residual heavy 34S in the relatively later closed‐like mineralization system. The ore‐reforming ages of 27 ± 3.2 Ma, 22.4 ± 3.9 Ma, and 21.3 ± 2.3 Ma were obtained by U–Pb isotopic dating combined with U–Ra balance correction, corresponding to the rapid uplift event caused by the remote effect of the collision between the Indian and Eurasian plates at the end of the Palaeogene. In conjunction with the tectonic–sedimentary evolution of the study region, a four‐stage ore‐forming model for the Middle Jurassic Toutunhe Formation is preliminarily constructed: ① Development of ore‐bearing strata, ② initiation of the mineralization stage from the Late Jurassic to the Early Cretaceous, ③ deep burial by lacustrine and flood mudstone from the Cretaceous to the Palaeogene, and ④ the superimposed ore‐forming stage during the Neogene. These research results provide significant benefits for further uranium prospecting and in situ leach process mining in this basin. [ABSTRACT FROM AUTHOR]

Early Jurassic Kaoshan medium‐ and fine‐grained syenogranites emplaced along the Yitong–Shulan Fault Zone in the southern part the Zhangguangcai Range, central Jilin Province, intruded Middle Triassic granitoids and Carboniferous‐Devonian intrusive rocks. They have medium‐ and fine‐grained textures and contain K‐feldspar, quartz, plagioclase, and biotite. They are peraluminous (A/CNK = 1.13–1.20) and have high values of SiO2 (74.60–75.82 wt%), total alkalis (Na2O + K2O = 8.28–9.18 wt%), light rare earth elements (20.89–56.14 ppm), large‐ion lithophile elements, and FeO/MgO = 2.78–5.93. In contrast, they feature low values of CaO (0.40–0.49 wt%), TiO2 (0.05–0.14 wt%), P2O5 (0.02–0.04 wt%), Sr (24.20–62.59 ppm), heavy rare earth elements (5.14–11.80 ppm), high‐field‐strength elements, and δEu (0.41–0.76), and the calculated zircon saturation temperatures (Tzr) range from 804 to 870°C, all of which are similar to the geochemical signatures of anorogenic A1‐type granites. Zircon U–Pb geochronology analyses from the medium‐ and fine‐grained syenogranites yield concordia ages of 193.18 ± 0.95 Ma (MSWD = 6.7, n = 18) and 190.29 ± 0.92 Ma (MSWD = 8.7, n = 17), respectively, and belong to the Early Jurassic Sinemurian stage. In situ Hf isotope analyses of dated zircons yield εHf(t) values ranging from +17.0 to +9.7 and Hf model ages (TDMC) of 225–614 Ma. Their whole‐rock (87Sr/86Sr)i (0.704740–0.704133) and εNd(t) values (+2.8 to +0.2) are similar to those of many coeval A2‐type granites in this region, and they form an A‐type granite assemblage. Consequently, the Kaoshan medium‐ and fine‐grained syenogranites were probably derived from partial melting of juvenile lower crust and might be related to the subduction of the Palaeo‐Pacific Plate. [ABSTRACT FROM AUTHOR]

The southern Jiangxi Province is an important part of the fluorite mineralization belt in South China. Fluorite ore bodies are primarily in the contact zone between the Devonian Huitong granitic complex and the Late Cretaceous Ganzhou Formation, controlled by the NE‐trending faults. Zircon U–Pb dating of the Huitong granitic complex yields emplacement ages of 410.7 ± 1.4 Ma and 400.7 ± 4.6 Ma, while the Sm–Nd dating of the fluorite yields an isochron age of 94 ± 2 Ma, suggesting that the Huitong granitic complex is the host rock. Fluid inclusions in the fluorite show low homogenization temperatures (136–207°C), salinities (1.23–3.87 wt% NaCl), and densities (0.87–0.95 g/cm3), suggesting that the ore‐forming fluid is an NaCl‐H2O system of low temperature, salinity, and density. Raman spectroscopy showed that the fluid phase is dominated by water. The δDVSMOW values of the fluid inclusions in the Tongda fluorite ranged between −59.5 and −55.2‰, while the δ18OVSMOW values of the fluorite ranged from −7.2 to −5.6‰. Collectively, the ore‐forming fluid is dominated by meteoric water, possibly with a minor contribution of hydrothermal fluid. Both the interaction with host rocks and the cooling of hydrothermal fluids are the likely mechanisms of underlaying fluorite precipitation at low temperatures. The mineralization occurred in extensional faults during the Late Cretaceous related to the subduction of the Palaeo‐Pacific Oceanic Plate. [ABSTRACT FROM AUTHOR]

A large number of fossil woods were preserved in the Permian–Triassic sequences in the Junggar Basin of Xinjiang Uygur Autonomous Region. These wood fossils provide a lot of palaeoenvironmental information of the Junggar Basin during the Permian–Triassic transition. Here, we describe the fossil woods collected from the base of the Olenekian Shaofanggou Formation in Dalongkou Anticline. Anatomically, these wood remains closely resemble Junggaropitys dalongkouensis, but they lack growth rings and rays are higher. Thus, we suggest identifying them as J. cf. dalongkouensis. The growth pattern shows that J. cf. dalongkouensis is evergreen and developed under warm and humid environments. However, the data of geochemistry, palaeosol and certain sedimentary features reveal a dry climate. Thus, we speculate that the Olenekian Junggar Basin contained gallery forests in the arid environment. [ABSTRACT FROM AUTHOR]

The depositional environment and sediment provenance of the third member of Palaeogene Shahejie Formation (Es3) in the Nanpu Sag of the Bohai Bay Basin, eastern China, are reconstructed by analysing trace element and rare earth element (REE), and the formation mechanism of organic‐matter‐rich shales of the same member is also evaluated. These results show that the terrigenous detrital supply in the Nanpu Sag was relatively sufficient during the Es3 interval, and the total REE contents range from 148.23 to 319.28 ppm, close to or higher than that of the upper crust. The Sr concentrations are 214.22–525.54 ppm and the Sr/Ba ratios are 0.31–0.74, which represent the coexistence of fresh, brackish, and saline waters during the Es3 interval. The V/(V + Ni) ratios of 0.71–0.82, Th/U ratios of 0.82–4.05, and positive δCe anomaly confirm that the water column was suboxic condition, with moderate stratification during the Es3 interval. Comparison of REE behaviours suggests that the Es3 sediments were primarily derived from Yanshanian granites at the Yanshanian fold belt at the active continental margin. The development of organic‐matter‐rich shales in the Es3 member in the Nanpu Sag was closely related to major palaeoenvironmental and palaeogeographical variations in that time, which can be summarized: (a) suitable palaeosalinity as well as sufficient nutrients in water column contributed to the boom of various planktonic algae, improving the production efficiency of aquatic organic matter; (b) suboxic water column slowed down the degradation of oxygen‐sensitive materials during the burial process, enhancing the preservation efficiency of aquatic organic matter. [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]

The West Qinling Orogen, which forms the western part of the Qinling Orogenic Belt, is characterized by the voluminous distribution of Triassic granitoids. Here, we investigate the Baguashan monzogranite which hosts numerous mafic microgranular enclaves (MMEs). We present zircon U–Pb–Hf and whole‐rock geochemical as well as Sr–Nd isotopic data of the monzogranites and MMEs with a view to gain insights on the petrogenesis and geodynamic setting. Zircon LA‐ICP‐MS U–Pb dating yields ages of 219.0 ± 1.7 Ma and 219.5 ± 1.6 Ma for the MMEs, and 214.2 ± 1.3 Ma for the host monzogranite, suggesting formation from coeval magmas. The host monzogranites show high SiO2, Rb, Ba, and Th contents, but low TiO2, MgO, P2O5 values, with A/CNK of <1.1. Zircon grains from monzogranites show εHf(t) values in the range of −6.3 to +3.2 with corresponding two‐stage Hf model ages (TDM2) of 1.39–2.25 Ga. The MMEs are mostly elliptical or spherical in shape and have lower SiO2 and Th contents, but higher MgO, TiO2, and CaO, and εHf(t) values ranging from −6.1 to +5.7 with TDM2 of 1.17–2.23 Ga. The Sr–Nd isotopic data for MMEs and monzogranites show (87Sr/86Sr)i ratios ranging from 0.7059 to 0.7069 and low εNd(t) values ranging from −6.07 to −4.18, suggesting a crustal origin. Based on the relatively homogeneous Sr–Nd–Hf isotopic compositions, we suggest that the MMEs represent magma mixing, and the mafic magma injected into the felsic magma chamber was probably derived by the reworking of mafic lower crust with a contribution of juvenile materials. We propose a model involving delamination of thickened lower crust below the West Qinling Orogen after the collision between the North China Block and the South China Block in the Late Triassic. Subsequently, the lower crust was partially melted by the heat input from the upwelling asthenosphere and produced the mafic magma. Partial melting of the ancient metamorphic rocks generated the granitic magma. The interaction of mafic and felsic magmas occurred within a post‐collisional tectonic setting in the Late Triassic. [ABSTRACT FROM AUTHOR]

The geochemical differences of magmatic rocks can be influenced by melt source and magmatic processes, including partial melting, fractional crystallization and magma mixing. New whole‐rock geochemical analyses, zircon U–Pb ages and Hf‐isotope data on granitoids from the Qingshanbao complex in the Longshoushan belt highlight a significant Late Ordovician–Early Silurian magmatic episode during the collision between the Alxa and Qilian‐Qaidam blocks, in which magma mixing was a fundamental process. The Qingshanbao complex comprises K‐feldspar granite, granodiorite and diorite emplaced coevally from 442 to 433 Ma. They exhibit peraluminous to metaluminous I‐type features, are enriched in large‐ion lithophile elements (LILEs) and light rare earth elements (LREEs) and depleted in high‐field‐strength elements (HFSEs). Chondrite‐normalized REE patterns are fractionated (LaN/YbN = 10.2–34.9) with weakly negative Eu anomalies (Eu/Eu* = 0.66–0.94). The 176Lu/177Hf zircon two‐stage model ages (TDM2) and the εHf(t) on zircons extracted from the K‐feldspar granite (1613–2,316 Ma, εHf(t) = −14.4 to −3.0) and granodiorite (1640–2015 Ma, εHf(t) = −9.6 to −3.6) suggest they were formed by the mixing of melts produced by the melting of Mesoproterozoic crustal materials, most likely meta‐basic rocks from the Longshoushan Group, and to a lesser extent mantle materials. In contrast, zircons in the diorite yield TDM2 ages ranging from 964 to 1767 Ma and εHf(t) values of −5.5 to 7.1, implying melting of depleted mantle rocks with subordinate participation of lower crust materials. We suggest that the Qingshanbao complex was emplaced when the North Qilian area was in a transitional stage from a compressional to an extensional environment as early as approximately 442 Ma. [ABSTRACT FROM AUTHOR]

The Tulaergen magmatic Ni–Cu deposit is related to mafic‐ultramafic rocks of the Central Asian Orogenic Belt. The ore‐host rocks are lherzolite and websterite and the major ore types are net‐textured and sparsely disseminated ores. The disseminated ores host high‐Fo (82–85) olivine and hornblende with low‐Al contents, high‐rare earth element (REE) abundances and negative Eu anomalies. The net‐textured mineralized lherzolite contains low‐Fo (74–82) olivine and high‐Al hornblende, the latter characterized by low REE concentrations and no Eu anomaly. The contrasting composition of olivine and hornblende suggests two stages of magmatism. In situ analysis of pentlandite, chalcopyrite and pyrrhotite shows that platinum‐group elements contents in sulphides are low. Contrasting Ni, Co, Se, Ag, Cd, and Pb contents in sulphides from net‐textured and in disseminated ores also supports two pulses of magmas, each with a distinct chemical composition. High‐Mg basaltic magma characterized the first stage, followed by a second‐stage less basic magma with a high H2O content. Whole‐rock Sr and Nd isotopic signatures suggest that about 4–6% crustal materials were added to the depleted mantle source. The fractional crystallization of olivine and crustal contamination play important roles in sulphur segregation at Tulaergen based on sulphur content at sulphide saturation modelling. Injection of magma enriched in H2O further enhanced sulphide aggregation and deposit forming. It is proposed that two pulses of magma injections occurred at the Tulaergen deposit, with the products of the first pulse settling at the base, and of the second one with dense mineralization laying at the top of the deposit. [ABSTRACT FROM AUTHOR]

The Elashan magmatic belt is located at the eastern margin of the East Kunlun orogenic belt (E‐KOB) in northwestern China, where voluminous magmatism occurred during the Late Permian to Late Triassic. Mid‐Triassic volcanism produced the Xilikete Formation, which shows a geochemistry similar to that of highly fractionated I‐type (HFI) volcanic rocks. These rocks are characterized by high SiO2 (73.82–74.97 wt%), differentiation index (DI; 91.01–94.69), and alkalis (e.g., high K2O + Na2O, with K2O/Na2O ratios greater than 1.0) and by enrichment in some large‐ ion lithophile elements (LILEs; e.g., Rb, K, and Pb) and depletion in other LILEs (e.g., Ba and Sr) as well as some high‐field‐strength elements (HFSEs; e.g., Nb, Ta, and Ti); these features confirm that they are HFI volcanic rocks. Zircon U–Pb ages indicate that the volcanic rocks were emplaced at ~239 Ma. These zircons have εHf(t) values ranging from −2.26 to +0.36, with two‐stage model ages (TDM2) of 1,441–1,221 Ma, indicating a magma source that involved partial melting of Mesoproterozoic lower crust accompanied by a minor juvenile mantle component. The ~240 Ma magmatism in the E‐KOB was probably developed in response to subduction of the Palaeo‐Tethys oceanic plate. Previous studies indicate that a tectonic transformation from subduction to continental collision occurred at ~240 Ma. Combining these data with regional geological observations, we conclude that the Daheba volcanic rocks formed in an active continental margin setting related to the subduction of the Palaeo‐Tethys oceanic plate beneath the E‐KOB. [ABSTRACT FROM AUTHOR]

We present in‐situ zircon laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) U–Pb ages, whole‐rock geochemistry, and Sr–Nd–Pb–Hf isotopes of the Mugagangri monzogranite in the southern margin of the Qiangtang Block, Tibet, western China. The zircons yield a U–Pb age of ca. 123 Ma. The hornblende‐bearing monzogranite shows metaluminous to weak peraluminous and high‐K calc‐alkaline characteristics exemplified by high silica (SiO2 = 67.57–70.57 wt%), high aluminium (Al2O3 = 14.68–15.78 wt%), high potassium (K2O = 4.00–5.14 wt%), high alkali (K2O + Na2O = 7.88–8.62 wt%), and low calcium contents (CaO = 1.72–2.17 wt%), with the aluminium saturation index (A/CNK) ranging from 0.98 to 1.09, suggesting that the Mugagangri monzogranite is a metaluminous to weak peraluminous I‐type high‐K calc‐alkaline granite. Geochemically, similar to the arc magmas, the monzogranite is enriched in large‐ion lithophile elements, and relatively depleted in high‐field‐strength elements. The monzogranite displays relatively high (87Sr/86Sr)i values (0.70972–0.71240), uniform εNd(t) values (−2.24 to −3.40), variable zircon εHf(t) values (−14.1 to +8.0), and high radiogenic Pb isotopic values (206Pb/204Pb = 18.588–18.790, 207Pb/204Pb = 15.616–15.642, and 208Pb/204Pb = 38.838–39.053). These geochemical characteristics indicate that the monzogranite was derived from a mixed source comprising ancient crustal and mantle materials, and experienced fractional crystallization during emplacement. We propose that the parental magma of the Mugagangri monzogranite was most likely generated during northward subduction of the Bangong Co‐Nujiang Meso‐Tethys Ocean. [ABSTRACT FROM AUTHOR]

Numerous granitoid suites exposed in the Qilian orogen, NE Tibetan Plateau preserve important records of the tectonic evolution of this orogen. Here we present zircon U–Pb, zircon rare earth elements (REEs), and whole‐rock geochemical and Sr–Nd–Hf isotopic data on Niuxinshan granitoids in the North Qilian orogen, with a view to constrain their petrogenesis and timing of emplacement, as well as to gain new insights into the Early Palaeozoic tectonic evolution of the Qilian orogen. Zircon U–Pb data show multiple concordant ages of ~517, 455–425, 397–389, and 351–319 Ma for syenogranite, and ages of ~758 and 724 Ma together with some scattered Early Mesozoic discordant ages for porphyritic granite, suggesting episodic magmatism from Neoproterozoic to Early Mesozoic. Zircon ∑REEs range from 276.43 to 4,582.32 ppm, and are characterized by depletion of light REEs (LREEs) and enrichment heavy REEs (HREEs) with negative Eu anomalies, indicating a mixture of magmatic and hydrothermal zircons. Whole‐rock geochemical data show similar variation of LREEs, large‐ion lithophile elements (LILEs), HREEs, and high‐field‐strength elements (HFSEs) with zircon REEs, with Eu, Ba, P, and Ti negative anomalies and Rb, U, and Pb positive anomalies. Based on their formation ages, two groups of granitoids are identified. Group I rocks (Early Palaeozoic) are represented by I‐type granites whereas Group II rocks (Early Mesozoic) are of S‐type. Whole‐rock Sr–Nd–Hf isotopes display (87Sr/86Sr)i ratios of 0.707085–0.709591, εNd(t) values of −5.3 to −2.3, εHf(t) values of −2.2 to 0, and two‐stage model (Nd and Hf) ages of 1.6–1.4 Ga for Group I rocks, and of 0.728156–0.734113, −9.4 to −9.3, −10.6 to −6.9, and 2.1–1.9 Ga for Group II rocks. Accordingly, we infer that the magma for Group I was sourced from the partial melting of basaltic protoliths in the mafic lower crust and underwent fractional crystallization. Group II was derived from metasedimentary protoliths through reworking of ancient Palaeoproterozoic crustal components. Integrating the results from this study with those from previous studies on Niuxinshan granitoids, we argue that the southward subduction model of the North Qilian Ocean beneath the Qilian Block during the Early Palaeozoic might be a more reasonable scenario. However, the Early Mesozoic magmatic event reported here remains equivocal in the North Qilian orogen. [ABSTRACT FROM AUTHOR]

The Ayishan Group in the Lajishan area is sandwiched between the South Qilian Belt and the Qilian Block, which is transitionally interpreted to represent the products of the post‐collision setting or the continental marginal arc during the Early Ordovician or Silurian and is associated with the evolution of the Proto‐Tethyan Ocean. While the detailed information about the age, geochemistry, and tectonic setting of the Ayishan Group is lacking, our geological mapping and analyses demonstrates that the Ayishan Group consists of andesites, rhyolites, ignimbrites, sandstones, and conglomerates, which unconformably overlies the Cambrian–Ordovician arc‐ophiolite complex. Zircon U–Pb dating of the rhyolites demonstrated that the Ayishan Group formed between 447 and 442 Ma and is Late Ordovician. Geochemical analyses demonstrated that rhyolites have high and variable SiO2 contents of 69.6–76.5 wt% and an aluminium saturation index (A/CNK) of 0.85–1.45, belonging to calc‐alkaline to high K calc‐alkaline series. They are subdivided into two subtypes of high‐Sr/Y rhyolites (HSRs) and normal rhyolites (NRs) based on the geochemical characteristics. The HSRs show lower total rare earth elements (34.77–62.78 ppm), lower Yb (0.19–0.21 ppm) and Y (1.77–1.99 ppm) contents, and relatively higher Sr contents (159–193 ppm), compared with NRs, and with positive Eu anomalies. Both subtypes exhibit extremely high whole‐rock δ18O values of 12.63–13.21‰, but various initial 87Sr/86Sr ratios and εNd(t) values, indicating a dominant origin of terrigenous sediments and the HSRs exhibit a more terrestrial composition than the NRs. Various magma sources further caused the assorted residual phase leading to the different geochemistry between the HSRs and the NRs. Combined with the previous data, these results imply that the rhyolites of the Ayishan Group were produced in the process of the amalgamation of the Qilian Block with the Qaidam Block during the Late Ordovician, which further indicated that the Proto‐Tethyan Ocean closed 450 Ma ago. [ABSTRACT FROM AUTHOR]

Laser ablation–inductively coupled plasma–mass spectrometry zircon U–Pb ages indicate that the Shaziling pluton in the Jiuyishan area, Ningyuan County, Hunan Province crystallised at 151.9 ± 1.1 to 154.1 ± 1.2 Ma, indicating that it was emplaced during the Late Jurassic. The Shaziling pluton is metaluminous to peraluminous (A/CNK = 0.93–1.09), and has high silica and alkali contents, low Ca and Mg contents, and K2O/Na2O and FeO*/MgO ratios of 1.37–2.65 (mean = 1.80) and 5.43–15.33 (mean = 7.14), respectively. The total rare earth element (REE) content varies from 186.75 to 413.17 ppm, and the pluton is enriched in light REEs and shows negative Eu anomalies (0.095–0.224). It is enriched in the large‐ion lithophile elements Rb and Th, and depleted in Ni, Cr, Eu, Ti, V, P, and Sr. The pluton yields Ga/Al ratios of 245–582 ppm (mean = 350 ppm) and Zr + Nb + Ce + Y contents of 256.8–630.7 ppm (mean = 441.95 ppm), similar to A‐type granites. The Shaziling pluton has a high initial 87Sr/86Sr ratio (Sri = 0.71603–0.71817), and low εNd(t) (−6.8 to −7.4) and εHf(t) (4.8 to −14.2) values. The granitic magmas were produced by partial melting of crustal material, along with a mantle contribution. The Nd and Hf model ages are 1546–1498 and 1756–1061 Ma, respectively, suggesting that the source rocks separated from the mantle reservoir during the Mesoproterozoic. The Shaziling pluton was formed in an intracontinental extensional environment related to subduction. [ABSTRACT FROM AUTHOR]

Granitoids and their mafic microgranular enclaves (MMEs) provide important insights into magmatic activity and tectonic evolution associated with accretionary orogens. Here we investigate the origin of Middle Triassic granodiorites and MMEs in the central segment of the eastern Kunlun Orogen (EKLO) in NW China, which is an important region to evaluate the history of closure of the Paleo–Tethys, through zircon U–Pb geochronology, major and trace element geochemistry, and Sr–Nd–Hf isotopes. Zircon U–Pb ages indicate the coeval formation of granodiorites and their MMEs during the Anisian (ca. 245 Ma). The granodiorites are calc‐alkaline and metaluminous with high SiO2 contents and Mg# values. They are characterized by enrichment of LREEs and LILEs, and depletion of Nb, Ta, and Ti. Their Sr–Nd –Hf isotopic compositions indicate that the magmas were derived from enriched mantle and Paleoproterozoic basement. The monzodioritic‐dioritic MMEs exhibit low SiO2 contents and high Al2O3 and MgO with high Mg# values, enrichment in LREEs and LILEs, and depletion in HFSEs with negative Nb, Ta, Ti, and P. In contrast, the gabbroic MMEs show higher Mg# values and Cr contents. Both types of MMEs have Sr–Nd–Hf isotopic compositions similar to the host granodiorites, and originated from mixing of lower crust‐ and enriched mantle‐derived magmas. The mantle‐derived sources were metasomatized by slab‐derived melts. The Middle Permian to Middle Triassic magmatism, metamorphism, sedimentation, and tectonics in the EKLO suggest northward subduction of the Paleo–Tethys Ocean as represented by the A'nyemaqen Ocean. The magma mixing that generated the Anisian granodiorites and MMEs was likely associated with slab break‐off of the Paleo–Tethys Ocean. The formation of the Anisian magmatic rocks in the EKLO suggest that the cessation of subduction of the Paleo–Tethys Ocean and onset of collision took place during the late stage of Middle Triassic. [ABSTRACT FROM AUTHOR]

The Liaoshang gold deposit in the Jiaodong area of the Shandong Province is best known for its super‐large size. Situated on the north‐eastern margin of the Jiaolai Basin, it forms a part of the Jiaobei terrane of the North China Block. Approximately 20 ore bodies within the Liaoshang gold deposit have been explored; of these, four are structurally controlled gold‐bearing pyrite–dolomite vein‐type deposits. These ore bodies lie in an NE‐trending altered fracture zone and are characterized by their thickness and high‐grade ores. The wall rocks of the ore bodies consist of Paleoproterozoic Jingshan Group metamorphic rocks and Mesozoic granites. Gold is hosted mainly in pyrite and dolomite. The ore is divided into two subtypes—the dominant pyrite–dolomite vein subtype and the subordinate altered rock subtype which contains pyrite and dolomite. Fluid inclusions within dolomite indicate that the main metallogenic period was dominated by a CO2–NaCl–H2O fluid system that had low‐moderate salinity, low density, high abundance of CO2, and a small amount of N2. The ore formed at 81‐ to 94‐MPa pressure and between 2.97‐ and 3.24‐km depth. Research on the S, Pb, C, O, and He–Ar isotopes in the gold‐bearing minerals suggests that the ore‐forming material was mainly crustal in origin, with some degree of crust–mantle mixing. The application of Rb–Sr isotope analysis to gold‐bearing pyrite yields a metallogenic age of 105.5 ± 9 Ma. The Sm–Nd isotope analysis of dolomite yields an age of 104.8 ± 5.1 Ma. We propose that gold mineralization in the Jiaodong area occurred in two phases: the early Early Cretaceous for gold deposits in the north‐west and the late Early Cretaceous for gold deposits in the east. [ABSTRACT FROM AUTHOR]

The Shihu quartz vein‐type gold deposit in the central North China Craton occurs within Neoarchean TTG (tonalite‐trondhjemite‐granodiorite) gneisses and shows spatial relationship with quartz diorite porphyry. The occurrence of the ore body is controlled by the N‐S fracture. Primary mineral assemblage of the ore body is composed of quartz, calcite, and base‐metal sulphides, including pyrite, galena, sphalerite, chalcopyrite, and pyrrhotite. Eight pyrite samples from veins of the main mineralization stage yield an isochron age of 129 ± 3 Ma (MSWD = 1.6), coinciding with the major Early Cretaceous magmatic event, and associated lithospheric thinning recognized in the NCC. The (87Sr/86Sr)i values of the pyrite (0.7102 ± 0.0006) are lower than the continental crust mean value (0.719) and higher than that of the mantle initial ratio (0.707), suggesting mixed crust–mantle source for the metallogenic components. Three types of hydrothermal pyrite from the early to major ore‐forming stages were identified in the quartz vein, including Py(I) as disseminated euhedral grains, Py (II) as dense bulks, and Py (III) as intergrowth with base‐metal sulphides. Electron microprobe analysis of the pyrite grains indicates a trend from S‐deficient to S‐enriched and from Fe‐enriched to Fe‐deficient stages, suggesting an increase in sulphur fugacity and reducing conditions. The arsenic in pyrite shows decrease against increasing Au during Stages II and III, implying that As is not the only trigger of gold precipitation, but electrochemical‐geochemical barrier played a major role in the formation of the ore. The Co and Ni concentrations, as well as Co/Ni ratios in pyrite, are relatively high, which provide an additional clue to the link with the regional magmatic event. Combined with the textural features, we propose a wider potential for gold exploration in this region, linking the mineralization with a major transitional tectonic regime. [ABSTRACT FROM AUTHOR]

The Shihu quartz vein‐type gold deposit, the largest gold deposit in the central North China Craton, occurs within wall rocks of Neoarchean TTG (tonalite–trondhjemite–granodiorite) gneiss and shows a close relationship with the early Cretaceous Mapeng granitoid pluton and various intermediate–mafic dykes. The occurrence, morphology, composition, and precipitation mechanism of the Au–Ag minerals are short of research, which is the purpose of this study. The primary mineral assemblage of orebody contains quartz, calcite, and base‐metal sulphides including pyrite, galena, sphalerite, chalcopyrite, and minor pyrrhotite and enargite. The Au–Ag minerals can be classified into three distinct types, namely, (a) quartz‐hosted, (b) pyrite‐hosted, and (c) base‐metal sulphidehosted, corresponding to formation sequence. Electron microprobe analysis indicates that these Au–Ag minerals show fineness (=Au/[Au + Ag] × 1,000) ranging from 976 to 366 with an average of 667 and are rich in Bi, Te, and Hg while deficient of Cu, As, and Se. Bismuth and tellurium in the Au–Ag minerals show a linear relationship with Au, whereas in the coexisted sulphides are almost below detection limits. We suggest that Bi and Te fundamentally influenced the transportation, enrichment, and precipitation of gold as scavengers to concentrate and deposit gold at the location with an "appropriate distance" from magma. Phase analyses of native bismuth and Bi–Te minerals included in pyrite, reported for the first time in Shihu Gold deposit, imply that the gold precipitation witnessed the ore‐forming fluid evolution with log fTe2 decreasing from approximately −11 to approximately −15 and log fS2 increasing from approximately −13 to more than −11. Mineralogical mapping with the fineness of Au–Ag minerals (fineness contours) suggest that the ore‐forming fluids came from the deep earth beneath the north of the mining area with excellent gold potential, which has been verified by later drilling. [ABSTRACT FROM AUTHOR]

New LA–ICP–MS zircon U–Pb geochronology, whole‐rock major and trace element geochemistry data, and petrographic observations are presented for three granitic dykes in the Changlingzi area of NE China. These data provide precise age and petrogenesis information with respect to the late Palaeozoic–Mesozoic intrusions in the area, which further constrain the geodynamic evolution of the southern Great Xing'an Range. Our zircon U–Pb data denote that the felsic dykes were emplaced during the Late Permian (~254 Ma) and Late Jurassic (143–142 Ma). Geochemically, the Late Permian monzonite porphyries are characterized by high Al2O3 (16.52–16.92 wt%) and Sr (490–579 ppm) contents and low Yb (0.52–0.57 ppm), Y (5.7–6.3 ppm), and heavy rare earth element (HREE) contents, which indicate an adakitic affinity. The Late Jurassic felsic dykes are characterized by high FeOt/MgO (8.2–11.9) and Ga/Al (3.3–3.8) ratios, high zircon saturation temperatures (888–929°C), and remarkable negative Eu (Eu/Eu* = 0.25–0.42) anomalies, indicating they are akin to A‐type granites. The Late Permian adakitic magma resulted from the partial melting of thickened lower crust, and was formed during collisional orogenesis related to subduction of Palaeo‐Asian Ocean crust. The Late Jurassic A‐type magmas were probably generated by the partial melting of amphibolite‐facies lower crustal materials. The melting occurred in response to the upwelling of asthenospheric material caused by collapse of thickened crust, due to gravitational instability during closure of the Mongol–Okhotsk Ocean. Subsequently, the latest stage of magmatic activity in this area and elsewhere in NE China was controlled mainly by subduction of Palaeo‐Pacific Ocean crust. [ABSTRACT FROM AUTHOR]

The Fukang Sag hosts prolific Jurassic lacustrine source rocks, which include the Badaowan (J1b), Sangonghe (J1s), and Xishanyao (J2x) formations in the Junggar Basin. Depositional conditions were reconstructed based on various major and trace element proxies for the East Fukang Sag during the Jurassic. The palaeowater depth in the sag was shallow and did not display a great change during the deposition of the J1b, J1s, and J2x formations, as indicated by lithological composition and the widespread ripple cross‐beddings. The oxic to dysoxic and fresh‐water conditions were postulated to prevail in the sag during the deposition of these source rocks, as revealed by concentrations of salinity‐ and redox‐sensitive trace elements [i.e., V/Cr, Ni/Co, (Cu+Mo)/Zn, Sr/Ba ratios, and Sr, Mn, Ga contents] derived from the source rocks. The seasonal salinity stratification superposed on preexisting thermal stratification led to the appearance of the chemocline in the J1b Formation. The palaeoclimate regime was humid and warm during the depositions of the J1b and the upper J1s formations, and warmer and drier during the deposition of the lower J1s Formation, but the palaeoclimate gradually became semi‐arid and semi‐cold during the deposition of the upper J2x Formation, as implied by various proxies (i.e., Sr/Cu ratio, C‐value, and CIA value). Despite the fact that the oxic to dysoxic conditions were not conducive for organic matter (OM) preservation, the significantly moderate‐high palaeoproductivity (suggested by, i.e., Ba content and Ba/Al ratio), which was promoted by a suitable supply of nutrient from terrestrial inputs in the shallow water was the controlling factorfor the OM accumulation on the margin of the sag, but the low OM concentration was controlled by the palaeoredox conditions in the central area, which was far from the OM input source [suggested by the relationship between total organic carbon content and stable carbon isotope composition of OM (δ13Corg)]. The analyses based on Rock‐Eval pyrolysis, maceral composition, C/N ratio of isolated kerogen, and δ13Corg value showing the OM was derived from terrestrial higher plants with C3 plants (type III kerogen) are consistent with the palaeoenvironmental analysis. [ABSTRACT FROM AUTHOR]