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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]

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]

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]

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]

Carboniferous magmatism in the Darbut region is critical for understanding the evolutionary history of the accretionary orogenesis of the West Junggar area in the Central Asian Orogenic Belt. In this paper, zircon U–Pb geochronological, whole‐rock geochemical and Sr–Nd–Pb–Hf isotopic analyses of the basalts, basaltic andesite, and dacite from the Carboniferous Tailegula Formation, Darbut region, have been performed. The magmatic zircons from basalt, basaltic andesite, and dacite yield concordia U–Pb isotope ages of 344 ± 4, 347 ± 3, and 340 ± 5 Ma, respectively, which are interpreted as the crystallization ages of these rocks. The basalts and basaltic andesite are characterized by an alkali composition; high Nb/Yb, Th/Yb, Ta/Yb, La/Sm, and Sm/Yb trace element ratios and Pb isotopic ratios; moderate (87Sr/86Sr)i ratios; low (143Nb/144Nb)i ratios; and positive εNd(t) (+0.66 − +4.73) and εHf(t) (+1.7 − +15.2) values. These characteristics indicate that the magmas were derived from mixed mantle sources, that is, enriched mantle sources and high U/Pb ratio mantle (HIMU) component sources with ≤10% partial melting of garnet and spinel lherzolite. The samples display pronounced light rare earth elements (LREEs) and incompatible element enrichment patterns with positive Nb–Ta anomalies and a high Pb content and Nb/La ratios but low (Th/Nb)N ratios and a lower degree of partial melting, implying that these rocks were formed in a continental extensional setting. Based on our results and that of previous studies, we conclude that the early Carboniferous volcanic rocks in the Darbut region formed by mantle plume or regional‐scale mantle upwelling in a continental extensional setting after closure of the Junggar 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 tectonic setting of the Alxa Tectonic Belt (ATB) during the late Palaeozoic is highly controversial. The nature and tectonic origin of the late Palaeozoic magmatism in the ATB are key to resolving the current controversy. This paper provides field, petrographic, geochemical, and zircon U‐Pb‐Hf isotopic data for the late Palaeozoic granitoids and volcanic rocks from the south‐western ATB. The granitoids display a wide range of SiO2 contents from diorite, granodiorite, to granites, with widely distributed hydrous minerals such as hornblende and biotite. They are calc‐alkaline to high‐potassium calc‐alkaline, metaluminous with an enrichment of light rare earth elements and large‐ion lithophile elements (LILE), and a depletion of high‐field‐strength elements (HFSE). The presence of mafic‐intermediate enclaves in the plutons suggests the role of crust–mantle interaction in generating the granitoids. The volcanic rocks show "block‐in‐matrix" structures in the field. They are dacite‐porphyry and rhyolite and show calc‐alkaline characteristics with an enrichment of LILE and a depletion of HFSE. Laser ablation inductively coupled plasma mass spectrometry zircon U‐Pb dating shows that the granitoids and enclaves crystallized during ~317–287 Ma and the dacite porphyry formed at ~295 Ma. Hf‐in‐zircon isotopic compositions reveal predominately positive εHf (t) values and Neoproterozoic TDMC ages for the magmatic rocks, indicating mixing between mantle‐derived magma and Precambrian basement during their genesis. The diagnostic field, geochemical data, and isotopic data imply these rocks were generated in a subduction‐related active continental margin setting. The presence of A2‐type granite indicates an extensional environment resulted from slab rollback in a retreating accretionary context can best interpret the large‐scale late Carboniferous–early Permian magmatism in the ATB. Our new data, combined with published data, imply that a large active continental margin existed in the Beishan, Alxa, and the northern margin of the North China Craton, due to the south‐dipping subduction of the Palaeo‐Asian Ocean (PAO) in the late Palaeozoic. Therefore, our data suggest that the PAO did not close until after the early Permian. [ABSTRACT FROM AUTHOR]

Subduction system in the Qilian orogenic belt experienced the variability of an active continental arc in space and time related to the subduction of the Proto‐Tethys Ocean. Zircon U–Pb geochronology and whole‐rock chemical and Sr–Nd isotopic data of mafic to intermediate dykes in the western part of the Central Qilian belt (WCQB) are used to track magma provenance from compositionally variable reservoirs in the sub‐arc mantle and constrain the magmatic evolution of the rear‐arc at 450–445 Ma. Petrological, whole‐rock chemical and zircon U–Pb dating results reveal that the studied dykes mainly comprise calc‐alkaline lamprophyre (CAL), high Mg# andesitic porphyrite (HMA) and high FeO hornblende gabbro (HFG) with crystallization ages of 447, 453 and 448 Ma, respectively. Among them, CAL and HMA have affinities in high‐K calc‐alkaline suites, high REE contents (∑REE = 131.1–202.3 ppm) with high LaN/YbN values (6.77–17.99), enriched in large‐ion lithophile elements (LILE, e.g., Rb and U), and depleted in high‐field‐strength elements (HFSE, e.g., Nb, Ta, and Ti). They also have high Th/La (0.20–0.46), Th/Nb (0.67–1.64) and Th/Yb (3.88–14.11) ratios, and relatively high whole‐rock initial 87Sr/86Sr ratios (0.707469–0.708493) and εNd(t) values (−4.7 to −3.1). Whereas, HFG is affinities in medium to high‐K calc‐alkaline suites, and has moderate rare earth elements (∑REE = 70.1–112.5 ppm) with flat REE patterns (LaN/YbN = 2.12–3.05) and exhibits enriched LILE, and Sr–Nd isotopes ((87Sr/86Sr)i = 0.713496–0.729216, εNd(t) = −2.93 to +2.04). Such typical "continental" geochemical features of the different K‐rich dykes do not result from crustal assimilation but reflect an enriched mantle source resulting from their mantle heterogeneity due to recycling of different subducted sediments. The temporal evolution of the geochemical characteristics of mafic‐intermediate dykes is consistent with an extension setting triggered by removing the thickened arc crust root in the WCQB. [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]

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]

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 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]

Microbial communities regained prominence in the Cambrian after a prolonged downturn in the Neoproterozoic, but the reasons for their revival are unclear. The earliest microbialites formed during this period within the Tarim Basin are well displayed in the Xiaoerbulake Formation in the Keping area. Major, trace, rare earth element (REE) analyses were carried out using samples collected from two sections of the Xiaoerbulake Formation which present two different palaeogeographical settings, namely, the intraplatform and platform margin. The samples were divided into seven groups based on their REE + Y (yttrium) distributions. Among these, the YG3, YG4, and PG3 groups correspond to microbial boom phases. The high contents of Al and other nutrient elements (e.g., P, Ni, U, Cu, Fe, Mn) in these three groups indicate that the microbial booms are controlled by nutrient concentration of different sources. In relatively deep‐water settings, aeolian dust and suspension particles modified the seawater geochemical characteristics to form shale‐like (REE + Y)N patterns. The nutrient‐rich fine‐grained deposits were blown up by storms and released nutrients. This eutrophication ultimately promoted microbial development and is demonstrated by light rare earth element enrichment patterns. In shallow‐water environments, microbes seemed to prefer quiet conditions, with sufficient nutrients provided by fluvial influx. In contrast, excess clastic materials inputs, be they carbonate or terrigenous debris, are unfavourable to the development of microbialites. Hence, it is expected that seawater REE preserved in ancient carbonates are capable of providing information on the impacts of seawater geochemical conditions on the evolution of microbialites. [ABSTRACT FROM AUTHOR]

High‐K calc‐alkaline granitoids play a key role in understanding the formation and evolution of the continental crust. Herein, we present new laser ablation inductively coupled plasma mass spectrometry zircon U–Pb and Lu–Hf isotopic, whole‐rock geochemical and Sr–Nd isotopic data of early Jurassic high‐K calc‐alkaline granitoids in the Zhanggunagcai Range, NE China. In situ zircon U–Pb dating shows that the granodiorite‐monzogranite‐granite (GMG) suite was emplaced at ca. 192–187 Ma. They are high‐K calc‐alkaline and weakly peraluminous, similar to the geochemical characteristics of I‐type granites. The GMG suite has lower bulk‐rock initial 87Sr/86Sr ratios of 0.7037–0.7042, slightly positive εNd(t) values of +1.10 to +1.87 and highly positive zircon εHf(t) values of +5.3 to +10.9. This result suggests a major contribution of juvenile crust to the magma source. The tetrad rare earth element patterns and highly negative Eu anomalies of samples with high SiO2 contents indicate that fractional crystallization plays an important role in the genesis. Together with data in the literature, we infer that the early Jurassic granitic rocks have been formed by partial melting of juvenile arc crust associated with the westward subduction of the Paleo‐Pacific Plate. [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 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 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]

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]

Biotite is an important silicate mineral that can be used to decipher the physicochemical attributes of magmatic or hydrothermal systems. The Lizhuang rare‐earth element (REE) deposit in Sichuan Province, Southwestern China, formed from continuous magmatic‐hydrothermal processes is related to a Cenozoic carbonatite–syenite complex. Biotites are abundant in this deposit, which can be divided into two generations: generation I in intergrown with alkaline feldspar and aegirine‐augite and generation II in association with bastnäsite‐(Ce). We investigated chemical composition of the two biotite generations using electron‐microprobe(EMPA) and laser ablation–inductively coupled plasma–mass spectrometer (LA–ICP–MS) analyses to understand the development of REE mineralization. Generation I biotite has relatively high Al2O3 (10.2–12.4 wt%), TiO2 (0.49–1.85 wt%), and FeOtot (12.2–15.9 wt%), but low SiO2 (40.0–42.5 wt%) contents compared to generation II counterpart. These two generations of biotite also differ in some key trace elements. Specifically, generation I biotite has much higher concentrations of Sr (up to 234 ppm) and Ba (up to 20,796 ppm), but lower levels of Li (47.5–126 ppm) with respect to its generation II counterpart. When comparing Lizhuang biotites with those of other barren carbonatite complexes, we identified an unusual compositional trend in the generation II biotites termed as fluorphlogopite trend. This trend is marked by the continuous increase in the Mg content towards mineralization and, therefore, can serve as a diagnostic attribute in the determination of mineralized carbonatite complexes. Fluorine in biotite is an important parameter that can be used as a vector for REE exploration, because the generation II biotite presents much higher fluorine contents (2.20–4.06 wt%) than its generation I counterpart (0.87–1.59 wt%). The compositional data of the two biotite generations indicate a depletion of Fe and a progressive enrichment in Mg and F in the ore‐forming system during its evolutionary process. Physicochemical parameters estimated by biotite composition suggest that there is a trend of strongly decreasing temperature from the crystallization of generation I to generation II biotite. It is therefore concluded that temperature is a major factor favourable for REE mineralization in the Lizhuang deposit, particularly given related experimental studies. Taken together, we propose that biotite composition could serve as a proxy for REE mineralization processes and as a reliable index for REE routine exploration in a carbonatite‐related setting. [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]

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 Bayan Har Group in Quanshuigou area of the northern Tibetan Plateau is regionally subdivided into three litho‐stratigraphic units, namely, the upper, middle, and lower formations. In this study, we report geochemical data for the fine‐grained sandstones from the upper formation aiming to constrain their source area weathering, provenance, palaeoenvironment, and tectonic setting. The fine‐grained sandstones exhibit similar contents of SiO2 and Al2O3 relative to upper continental crust (UCC) and Post‐Archean Australian Shale and classified as wacke on log (SiO2/Al2O3)–log (Fe2O3/K2O) diagram. The trace elements are characterized by the depletion of the transition elements compared with the UCC. The chondrite‐normalized rare earth element (REE) patterns demonstrate enrichment of light REE (LREE) and depletion of heavy REE (HREE) with LREE/HREE varying from 7.99 to 10.28, as well as distinctive negative Eu anomalies (δEu = 0.63–0.73). The high index of compositional variability values indicates the fine‐grained sandstones are compositionally immature and first cycled. The low chemical index of alteration and plagioclase index of alteration values of the samples indicate the weak source weathering condition. Additionally, the characteristics of A–CN–K plot reveal that K‐metasomatism occurred after burial. A series of palaeoenvironment indexes imply that the Bayan Har Group was deposited in a oxic/suboxic marine–terrestrial transitional environment. On the basis of the newly established DF1–DF2 discrimination functions as well as other tectonic setting discrimination plots, we speculate that the Bayan Har Basin was a back‐arc basin during the Late Triassic. [ABSTRACT FROM AUTHOR]

The Ordos Basin, a large mainly non‐marine basin, is an important petroliferous basin in northern China. The Triassic Chang 9 shales, including the delta plain shale (DPS), delta front shale (DFS), and deep lake shale (DLS), are proven to be the main source rocks in the lower Yanchang Formation (LYF). This study investigates the source rock potential, palaeoenvironment, and organic matter (OM) source. According to the OM thermal maturity, abundance, and type, the shales have excellent source rock potential. The DLS has the highest quality with average TOC of 7.08%, S1 + S2 of 14.41 mg HC/g rock, and Type II1–II2. According to correlations of Rb/Sr versus Sr/Cu, the shales were mainly deposited in arid conditions. Based on the major element (S), trace elements (V, Ni, Co, Cr, U, and Th), rare earth element (Ce) concentrations, and biomarkers (Pr, Ph, dibenzofuran, fluorene, and dibenzothiophene), redox conditions for the DPS, DFS, and DLS were oxidizing, sub‐oxidizing to sub‐reducing, and reducing, respectively. The palaeosalinity was fresh‐ to brackish‐water, ascertained by the trace elements (Sr and Ba) and biomarkers (gammacerane). The water stratification was controlled by the temperature changes and the palaeosalinity differences, and the maximum water depth was ~100 m during the Chang 9 deposition. Aquatic microorganisms (e.g., algae, bacteria, and phytoplankton) were the main organic matter sources for the shales, mixed together with terrigenous plants in DPS and DFS. The DLS has the most aquatic microorganisms and has the least higher plant fragments, supported by the higher TOC (up to 14%), lowest vitrinite contents (Avg. = 14.1%), and highest liptinite contents (Avg. = 59.5%). Laterally, the DPS, DFS, and DLS were distributed successively from the lake margin to the depocentre. Vertically, the DLS, DFS, and DPS were developed successively from the bottom lake to the upper lake. The DLS was mainly formed in an environment of high‐level sapropelinite and favourable preservation conditions, and the DPS was mainly formed in an environment of high‐level terrigenous inputs and poor preservation conditions, while the DFS was mainly formed in an environment of medium‐level of sapropelinite productivity and terrigenous inputs and fair preservation conditions. The DPS and DFS were formed during both the early stage (shallow lake) and the late stage (deep lake) of the Chang 9 deposition, while the DLS was only developed in the deep lake during the late Chang 9 deposition. The high‐level sapropelinite production and favourable preservation controlled the formation of the organic‐rich shales, especially for the organic‐rich DLS. [ABSTRACT FROM AUTHOR]

Potassic magmatic rocks provide significant insights in understanding of mantle composition, evolution, and interaction with crust. Potassic magmatism along the Jinshajiang–Ailaoshan Paleo‐Tethyan suture has drawn much attention. Whereas igneous intrusion in the Simao terrane, west to Jinshajiang–Ailaoshan potassic magmatic belt has rarely been investigated. Hence, we present zircon U–Pb ages and Lu–Hf isotope and whole‐rock geochemistry for the Lianhuashan pluton. Zircon U–Pb dating from monzonite and quartz monzonite porphyry yield ages of 33.6 ± 0.2 and 33.5 ± 0.3 Ma, respectively. Monzonites are characterized by high K2O (4.93–5.16%) and K2O/Na2O (1.46–1.71), high Y (22.90–23.80 ppm), and Yb (1.87–2.21 ppm), relatively enrichment of light rare earth element (LREE). Zircons from monzonites show εHf(t) values ranging from −1.1 to +0.6 and crustal model ages (TDMC) between 1.04 and 1.15 Ga. These geochemical features suggest that parent magmas of the rocks originated from a metasomatized lithospheric mantle. Quartz monzonite porphyries are characterized by high Sr (836.00–1,529.00 ppm), Sr/Y (70.85–99.93) and La/Yb (32.31–49.83), low Y (11.80–15.60 ppm), and Yb (0.95–1.30 ppm), enrichment in LREE and depletion in heavy rare earth elements (HREE). Quartz monzonite porphyries have higher Mg#, MgO, Ni, and Cr contents than the lower crust‐derived adakite‐like rocks. It is suggested that they were derived by variable degree of mixing between lower‐crustal melts and mafic magmas. Based on petrology and geochemistry features, the following evolution process are concluded. During the Neoproterozoic, metasomatic‐enriched mantle magma resulted from the bisubduction of oceanic plate; meanwhile, the crust thickened, and juvenile lower crust formed. During late Eocene, hot asthenosphere upwelled and K‐rich mafic magmas resulted from the decompression of delamination, followed by magmatism emplacing, crystallizing, and the forming of the Lianhuashan pluton. [ABSTRACT FROM AUTHOR]

There are widely developed carbonate formations in the lower Palaeozoic, Ordos Basin, China. However, previous studies have paid more attention to the Ordovician formations and largely ignored the Cambrian formations, which also have a larger sediment thickness. Recently, with the continuous discovery of dolomite gas fields in the Ordovician Majiagou formation, more investigations have begun to focus on the deeper dolomite in the Cambrian Sanshanzi Formation (Є3s). This study looks into the origin of the dolomite through a combination of petrology, major–trace elements, and stable isotope and rare earth element (REE) analysis of samples from five outcrops. The results show that the main dolomite types in the study area are dolarenite (Type 1), micrite‐fine crystalline dolomite (Type 2), and medium crystalline dolomite (Type 3). The δ13C values and δ18O values of each dolomite formation are close to those of seawater‐derived dolomite and have slightly higher Na2+ concentrations, suggesting that dolomite formation is closely related to the denser seawater. The REE compositions are characterized by enrichment for light REEs and depletion for heavy REEs, exhibiting an apparent negative Eu anomaly and a slight negative Ce anomaly, indicating that the dolomites of the Є3s may form in a weak‐reduction to the weak‐oxidation environment. The total REE (ΣREE) concentrations of Type 3 dolomites are lower than other types, suggesting that those dolomites may mean that the REEs are lost during the diagenesis. Type 1 dolomite has lower MgO and CaO values and a higher Mn2+ concentration than the other two types of dolomites, indicating that Type 1 dolomite suffered the action of atmospheric fresh water. Type 2 dolomite has lower Mg and Ca values than Type 3 dolomite, suggesting that Type 3 dolomite has a higher dolomitization degree. Further study into the combined palaeogeographical background confirms the dolomitization model of the study area: Type 1 and Type 2 dolomites may have been formed by penecontemporaneous or seepage–reflux dolomitization during early‐stage diagenesis. Subsequently, stratigraphic uplift lead to the Type 1 dolomite suffering the action of atmospheric fresh water, but there was no dorag dolomitization. Type 2 dolomite became the main dolomite type by seepage–reflux dolomitization in this period. Later, Type 2 dolomite was converted into Type 3 dolomite during progressive burial. [ABSTRACT FROM AUTHOR]

The Lesser Xing'an Range in NE China is an important gold district. However, the age and genesis of Early Cretaceous magmatic rocks that are coeval with gold mineralization remain obscure. A suite of Early Cretaceous igneous rocks in a newly discovered gold deposit at Yongxin was conducted zircon U–Pb dating and Hf isotope and bulk‐rock geochemistry and Sr–Nd–Pb isotope analyses. A dacite of the Guanghua Formation and an andesite of the Longjiang Formation have zircon U–Pb ages of 111.7 ± 1.5 Ma and 119.7 ± 1.9 Ma, respectively. The dacite has zircon εHf(t) values of 5.4 to 12.0 and depleted bulk‐rock Sr–Nd–Pb isotopes ((87Sr/86Sr)i = 0.7049 to 0.7056, εNd(t) = 1.2 to 2.5, (206Pb/204Pb)i = 18.202 to 18.320). The andesite has zircon εHf(t) values of 5.6 to 13.6, (87Sr/86Sr)i of 0.7049 to 0.7051, εNd(t) of 1.0 to 1.6, and (206Pb/204Pb)i of 18.199 to 18.297. The ~120 Ma diorite porphyry and granite porphyry have zircon εHf(t) values of 3.7 to 10.0 and 3.6 to 10.2, respectively. These two units show large variations of 87Rb/86Sr ratios (<1) and similar Sr–Nd–Pb isotopes compositions. All rock units are enriched in light rare earth elements and large‐ion lithophile elements and depleted in high‐field‐strength elements. The formation of Yongxin Early Cretaceous igneous rocks was related to variable degrees of partial melting from Jurassic basalt in the lower crust with significant contribution from ancient continental materials. The low Sr/Y ratios (2–24) and negative correlations between Sr, Eu/Eu, and SiO2 indicate that magmas of the Early Cretaceous igneous rocks at Yongxin have low water content and thus have low potentiality for porphyry copper mineralization. [ABSTRACT FROM AUTHOR]

The Heyu fluorite ore district is newly discovered in the East Qinling metallogenic belt (EQMB), central China. In this district, the large Madiu fluorite deposit contains five Mesozoic granite‐hosted orebodies. The deposit may have formed at shallow depth and occurred as continuous veins controlled by a series of N‐S‐ or NE‐trending, steeply dipping faults. The fluorite mineralization can be divided into two stages (I and II). Fluid inclusions in stage I fluorite homogenized at 132.2°C to 342.5°C (peak at 170°C–210°C) with salinities of 0.18 to 4.43 wt% NaCl equiv, whilst those in stage II fluorite homogenized at 122.2°C to 305.7°C (peak at 130°C–170°C) and salinities of 0.18 to 3.71 wt% NaCl equiv. Raman spectroscopic analysis of the fluid inclusions reveals that they comprise predominantly H2O. The rare earth element (REE) characteristics indicate that the deposit is of hydrothermal origin. The δ18OH2O (−8.8‰ to −0.5‰) and δDH2O (−69.0‰ to −61.9‰) values show a subhorizontal trend, suggesting that the oxygen isotopic compositions were modified by fluid–rock interactions. Fluid inclusion and stable isotopic data suggest that the ore‐forming fluids belong to a meteoric water‐sourced, medium–low temperature, and low salinity NaCl–H2O system. Initial fluorite 87Sr/86Sr ratios (0.708879–0.709682) resemble those of the Heyu batholith. The water–rock reaction, which leached Ca from the host rock and increased the fluid pH, was likely causative to the ore precipitation. Geochemical and mineralization features suggest that the Madiu fluorite deposit is best classified as a fault‐controlled hydrothermal vein‐type fluorite deposit. The Sm–Nd isochron age of 118.9 ± 7.8 Ma and its regional age correlation suggest that the fluorite mineralization occurred under regional extension or lithospheric thinning setting and that the fluorite mineralization was an important component of the Early Cretaceous mineralization event in the EQMB. [ABSTRACT FROM AUTHOR]

The North Tianshan in NW China is a key to understanding the accretionary history of the southern Altaids. However, the tectonic setting of the North Tianshan in the Carboniferous‐Permian is debatable, and its amalgamation history is ambiguous. We report new data on the field relations, geochronology and geochemistry of Carboniferous–Jurassic volcanic rocks and sedimentary rocks from the Shichang area in order to constrain the late Palaeozoic–Early Mesozoic tectonic evolution of the North Tianshan. New LA‐ICP‐MS zircon U–Pb dates demonstrate that the Carboniferous–Permian stratigraphy is a tectonic imbrication of Carboniferous–Permian rocks and Carboniferous volcanic rocks were emplaced in Permian volcano‐sedimentary rocks. The 311 ± 2 Ma volcanic rocks are calc‐alkaline, enriched in Light Rare Earth Elements and large‐ion lithophile elements, depleted in high‐field‐strength elements, and have low initial 87Sr/86Sr ratios with positive εNd(t)(+0.3 to +8.6)values. The geochemical‐isotopic data suggest the volcanic rocks were generated in an intra‐oceanic island arc. The turbidite samples 18SC02 (~267 Ma to ~349 Ma) and 18SC09 (~299 Ma to ~369 Ma) have a relatively narrow age range with no Devonian or Precambrian peaks. Our detrital zircon data suggest the presence of a so far unrecognized intra‐oceanic arc, which was isolated from the main Yili‐Central Tianshan and Mosuowan arcs in the Shichang area of the North Tianshan during the Late Carboniferous to Permian. The compiled detrital zircon data from Carboniferous to Jurassic indicates that the North Tianshan intra‐oceanic arc was probably amalgamated with the Mosuowan arc by the Early Triassic, and then accreted to the Yili‐Central Tianshan arc by the Middle‐Late Triassic, as revealed by the changes of zircon provenance of Carboniferous, Permian, Triassic and Jurassic sedimentary rocks. All integrated data suggest that the southern Altaids most likely formed by processes of multiple subduction–accretion and convergence similar to that in the ongoing southwest Pacific. [ABSTRACT FROM AUTHOR]

Xierqu is a skarn Fe–Cu deposit associated with porphyritic diorite, in the Kalatag district of eastern Tianshan, China. The diorite yields a sensitive high‐resolution ion microprobe U–Pb zircon date of 391 ± 3 Ma interpreted as its age of emplacement. Major element geochemistry shows that the diorite is a calc‐alkaline assaying 16.7–19 wt.% of Al2O3, with Mg# values of 56.8–67.1, and Al2O3/(CaO + Na2O + K2O) (A/CNK) values of 0.55–0.94. Trace element characteristics of the diorite show that it is enriched in Ba, K, and Sr and depleted in Nb, Ta, and Ti, with a positive Eu (1.18–1.44) anomaly and high Sr/Y and La/Yb ratios. Sr–Nd isotopic analyses yielded positive εNd(t) values ranging from 7.1 to 9.8 with low initial 87Sr/86Sr ratios of 0.703806 to 0.703856. These geochemical and isotopic characteristics indicate that the diorite is adakite‐like emplaced in an island‐arc setting and resulted from partial melting of subducted oceanic crust in a mantle wedge during the Devonian. [ABSTRACT FROM AUTHOR]

The Jiamusi Block is an important tectonic unit in the Chinese segment of the CAOB. Its eastern margin became an active continental margin in the period of Late Carboniferous. However, the tectonic affinity of this section has not been resolved yet. The Early Permian andesites within the Erlongshan Formation in the eastern Jiamusi Block provide a critical record for the active continental margin setting. Precise LA‐ICP‐MS U–Pb zircon dating on four andesite samples gave ages of 280 ± 3 Ma, 282 ± 3 Ma, 286 ± 4, and 284 ± 2 Ma, respectively, defining an Early Permian age for the crystallization of the andesites. The andesites have medium‐K and calc‐alkaline compositions, with variable SiO2 (54.70–57.46 wt%), TiO2 (0.87–1.12 wt%), TFe2O3 (6.52–8.13 wt%), MgO (2.62–3.33 wt%), Al2O3 (15.96–17.83 wt%), Na2O (3.28–4.10 wt%), and K2O (1.16–1.95 wt%) contents. They are relatively enriched in LREEs ((La/Yb)N = 5.0–7.1) and LILEs (e.g., Ba, Th, Sr, and U), deleted in HREEs and HFSEs (e.g., Nb, Ta, Zr, and Y) and have weak or no Eu anomalies (Eu/Eu* = 0.87–1.02). These geochemical features indicate that the andesites within the Erlongshan Formation originated from an active continental margin setting, and their magma source was produced by partial melting of a mantle material that had been metasomatized by subduction‐related melts and subsequently underwent the removal of mafic minerals and accumulation of plagioclase. Integrated with previous studies on the igneous and sedimentary rocks, we thus propose that the Jiamusi Block was in an active continental margin setting in the period of the Late Carboniferous to Early Permian (310–280 Ma), and it is more likely related to the subduction of the Mongol‐Okhotsk Ocean. [ABSTRACT FROM AUTHOR]

The Upper Devonian Shetianqiao Formation mudstones are considered to be the most petroliferous shale gas source rocks in the Shaoyang Sag of Xiangzhong Depression in China. These Shetianqiao dark mudstones have been collected systematically to investigate their geochemical characteristics by analysing their major elements, trace elements, and rare earth elements (REEs), in order to reveal their provenance, palaeoenvironment and tectonic setting. The results show that the total REEs content (ΣREE) of dark mudstone is 34.22–246.62 ppm (average 131.66 ppm) and characterized by low ΣREE, light rare earth element (LREE) enrichments, negative Eu anomalies, and minor negative Ce anomalies. The normalized distribution pattern of REE, Eu anomaly, as well as discrimination diagrams of trace elements and REEs, are applied to explain the source rock types and properties of Shetianqiao mudstones. The results indicate that the sediments have a weak sedimentary recycling and mainly originated from the upper continental crust, and the source rocks of the black mudstones are mainly constituted by felsic granite. The Ce anomaly, Th/U, V/Sc, V/Cr, and V/(Ni + V) ratios of the dark mudstones suggest a long‐term oxidizing depositional environment interrupted by a short period of a dysoxic/anoxic depositional environment in the middle section of the formation. This short period corresponds to a dramatic marine transgression with relatively high TOC. The La/Ce, LaN/SmN, Ce anomaly, and normalized REE distribution pattern characteristics indicate that the depositional process of the Shetianqiao mudstones has consistently been influenced by the regional upwelling hydrothermal activities. The chemical index of alteration (CIA) and Al2O3‐(CaO* + Na2O)‐K2O triangular plot reveal that a warm and humid climate with moderate chemical weathering in the source areas of the Shetianqiao mudstones occurred during the deposition. The ratio of major elements, trace elements, and REEs are used to analyse the tectonic setting of the depositional area which suggests that the source area is dominated by continental island arc tectonic setting. Combined with the previous regional studies, it is concluded that the continental island arc granite formed by plate collisions in the Caledonian stage constitutes the main source of the Shaoyang Sag during the Shetianqiao period. The depositional environment was not stable due to the lasting influence of deep hydrothermal activities. The upwelling currents controlled by hydrothermal activity transport nutrients to the study area, resulting in the formation of organic‐rich mudstones. [ABSTRACT FROM AUTHOR]

New zircon U–Pb age data, Hf isotopes, whole‐rock major and trace elements, and Sr–Nd isotopic data for Early–Middle Triassic intrusive rocks from the Jiawula and Tsagenbulagen area in the southern part of the Erguna Massif provide valuable constraints on the southward subduction of the Mongolia–Okhostk Ocean lithosphere. The Jiawula–Tsagenbulagen granitoids mainly consist of granodiorite, quartz monzonite, and biotite granite. These granitoids, long believed to be mainly Late Jurassic–Early Cretaceous (ca. 150–139 Ma) and minor Permian (ca. 278 Ma and 254–253 Ma), are newly found to contain a latest Early Triassic to Middle Triassic generation (zircon U–Pb age: ca. 248–244 Ma). Geochemically, the Early to Middle Triassic granitoids are characterized by high SiO2 (74–77 wt.%) and Al2O3 (12.2–15.95 wt.%), low Mg# values (12.98–37.32), and variable Na2O/K2O ratios (0.62–1.75). They are metaluminous to peraluminous and belong to the high‐K calc‐alkaline series. Moreover, they show enrichment in light rare earth elements and large‐ion lithophile elements and depletion in heavy rare earth elements and high‐field‐strength elements (e.g., Nb, Ta, and Ti). They have an increased amount of SiO2/Al2O3 but lower V/Th ratios and negative correlations between V/Th and SiO2/Al2O3 ratios, indicating that the magmas experienced various degrees of biotite and/or plagioclase fractional crystallization. Their whole‐rock εNd(t) and zircon εHf(t) values ranged from +1.07 to +4.15 and from +0.5 to +2.9, respectively, indicating that the primary magmas were probably generated by partial melting of juvenile crustal material with the help of mantle‐derived mafic magmas. These magmas subsequently underwent fractional crystallization, magma mixing, and a small amount of crustal contamination during their emplacement. The geochemical characteristics of these Early–Middle Triassic intrusive rocks have affinities with intrusive rocks from active continental margin settings. Therefore, we conclude that the Early–Middle Triassic magmatism in the Erguna Massif was generated within an Andean‐type arc setting related to the southwards subduction of the Mongol–Okhotsk oceanic plate beneath the Erguna Massif. We summarized previous age data of the Early to Late Triassic magmatic rocks from Erguna and Central Mongolia and identified arc setting granites and post‐orogenic granites. Thus, a tectonic evolutionary model was proposed for the geological observations in the Erguna and Central Mongolia massifs, involving the Triassic continuous southward subduction in the Erguna Massif and the Late Triassic slab‐rollback and back‐arc basin extension in the south‐eastern Central Mongolia Massif. [ABSTRACT FROM AUTHOR]

The recently discovered Bulage Pb–Zn deposit is located in the central part of the Erlianhot–Dongwuqi Metallogenic Belt (eastern Central Asian Orogenic Belt) in Inner Mongolia, China. The ore bodies of the deposit are hosted in alkali feldspar granite and in dacitic crystal tuff within Unit 2 of the Carboniferous Baoligaomiao Formation. The Bulage deposit is a low to moderate temperature hydrothermal vein‐type deposit and is controlled by fractures. The hydrothermal mineralization can be divided into three stages: early (quartz + specularite ± magnetite), middle (quartz + sphalerite + galena ± chalcopyrite ± pyrite), and late (calcite ± quartz + sphalerite + galena). The deposit contains liquid‐rich two‐phase (VL‐type) and pure‐liquid (L‐type) fluid inclusions. The initial ore‐forming fluids are attributed to the low to moderate temperature and low salinity of a NaCl–H2O system. Hydrogen and oxygen isotopic compositions of quartz and calcite indicate that the ore‐forming fluids were dominated by meteoric water with minor contributions of magmatic water. The quartz diorite, monzonite porphyry, and alkali feldspar granite in the deposit yield LA–ICP–MS zircon U–Pb ages of 305–300 Ma. These high‐K calc‐alkaline I‐type granitoids are enriched in large‐ion lithophile elements (LILEs; e.g., Rb, Cs, and K) and light rare earth elements (LREEs) and are depleted in high‐field‐strength elements (HFSEs; e.g., Nb, Ta, and Ti) and heavy rare earth elements (HREEs). The primary magma of these granitoids was derived from the partial melting of lower crust. The parental magma of the quartz diorite may have provided part of the ore‐forming material and acted as a heat source for mineralization. Therefore, we infer that the Bulage Pb–Zn deposit was formed as a result of the southward subduction of the Paleo–Asian Ocean beneath the North China Craton during the Late Carboniferous. [ABSTRACT FROM AUTHOR]

The West Qinling Orogenic Belt (WQOB) is a major portion of the Qinling‐Dabie‐Sulu Orogen and holds essential information for understanding the protracted evolution of the north‐eastern branch of the Paleo‐Tethys in East Asia. In this study, we report our petrological, geochemical, and geochronological study on the five Triassic granitoid plutons of West Qinling with emphasis on the poorly studied Jiaochangba pluton with zircon U–Pb ages of 217.5 ± 1.6 Ma and 215.2 ± 1.2 Ma. The new data and the existing data on the other four plutons support the view that the West Qinling granitoids represent a magmatic response to the continental collision of the Yangtze Block (YB) with the North China Craton (NCC) in the Triassic. Like the other four plutons, the Jiaochangba pluton shows strong light rare earth element (REE) enrichment and weak heavy REE depletion ([La/Sm]N ≈ 7.14 ± 1.89; [Sm/Yb]N ≈ 4.63 ± 1.85) with varying negative Eu anomalies (Eu/Eu* ≈ 0.65 ± 0.20). In the N‐MORB normalized diagram, all the samples show relative enrichment in Rb, Pb, U, and K with negative Nb, Ta, P, and Ti anomalies, resembling those of the model continental crust. The Jiaochangba pluton has relatively lower (87Sr/86Sr)i (0.7062 to 0.7081), higher εNd(t) (−6.91 to −2.09), and εHf(t) (−5.57 to −0.14) than mature continental crust, which are consistent with their source being dominated by lower crust with significant mantle contributions. Mantle‐derived melt, which formed from partial melting of mantle wedge peridotite facilitated by dehydration of the subducted/subducting Mianlue ocean crust, provide the required heat for the crustal melting while also contributing to the compositions of these granitoids. Evolution of such parental magmas in open system crustal magma chambers with continued evolution/replenishment and crustal contamination and assimilation give rise to the observed petrological and geochemical characteristics of these granitoids. [ABSTRACT FROM AUTHOR]

The Derbur lead–zinc deposit is located in the Derbugan metallogenic belt in the north‐western portion of the Mesozoic Hailaer‐Genhe volcanic basin in the northern Great Xing'an Range. This deposit occurs in the Middle Jurassic intermediate–mafic volcanic rocks of the Tamulangou Formation and is spatially and temporally associated with acidic pyroclastic rocks. The host rocks are bedded trachyandesite and rhyolitic lithic‐crystal tuffs, and basaltic‐andesitic aplite veins are associated with the ore body. Because the deposit is a hypabyssal low‐temperature hydrothermal Pb–Zn deposit associated with volcanism, to determine the precise petrogenesis of the volcanic rocks, this study analysed the zircon U–Pb ages of the trachyandesite and rhyolitic lithic‐crystal tuffs, the Sr–Nd–Pb isotopic geochemistry of the trachyandesite and basaltic‐andesitic aplite, and the whole‐rock geochemistry of all three rock types. The results showed that the trachyandesite and basaltic‐andesitic aplite belong to the shoshonitic series and have similar whole‐rock and isotopic geochemical characteristics, including enrichments in large‐ion lithophile elements and light rare earth elements and depletions in high‐field‐strength elements. They also have low initial 87Sr/86Sr values of 0.705007–0.705240 and εNd(t) values of +0.6 to +1.7, with model ages (TDM) of 699–883 Ma. The ratios of 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb vary from 18.438 to 18.476, 15.570 to 15.577, and 38.254 to 38.320, respectively, with μ values of 9.40–9.41. In contrast, the rhyolitic lithic‐crystal tuffs are characterized by high SiO2 contents (73.44–79.48 wt.%); low Al2O3 (11.36–12.53 wt.%), TiO2 (0.14–0.18 wt.%), and K2O + Na2O (3.48–3.89 wt.%, Na2O ≤ K2O) contents; and low Mg# values (0.17–0.41), indicating that they belong to the calc–alkaline series. Additionally, they have relatively low REE contents and strong Sr depletions. LA‐ICP‐MS zircon U–Pb dating of the trachyandesite and rhyolitic lithic‐crystal tuffs indicates that their ages are 167.0 ± 2.0 Ma and 164.8 ± 1.6 Ma, respectively. We conclude that the trachyandesite and the basaltic‐andesitic aplite were derived from the partial melting of lower crustal material assimilated by a depleted lithospheric mantle that was subsequently metasomatized by subducted slab‐derived fluids. The rhyolitic lithic‐crystal tuffs likely originated from the partial melting of accreted lower crust. In summary, because the acidic volcanism was accompanied by increasingly felsic volcanism, bimodal volcanic rocks were produced. Among volcanogenic deposits, bimodal volcanic rocks are the most favourable ore‐hosting rocks, and ore‐forming materials were contributed by the magmatic system. These processes created conditions conducive to the formation of large‐scale Ag, Pb, and Zn mineralization in this area. [ABSTRACT FROM AUTHOR]

Early Neoproterozoic granites rarely outcrop in the Qilian Orogenic Belt (QOB) at the north‐eastern margin of the Qinghai–Tibet Plateau; however, they are vital to understanding the Precambrian evolution of the QOB. Thus, we present an integrated study, comprising petrology, geochronology, and whole‐rock geochemistry of two Early Neoproterozoic granitic plutons (Baihuagou and Yamacha plutons) in the eastern Qilian Block (QB). The results provide three key findings. First, their magma emplacement age is ca. 900 Ma (i.e., 918 Ma for Baihuagou and 910 Ma for Yamacha), and the two plutons have similar high‐K calc‐alkaline, strongly peraluminous characteristics, with slight enrichment in light rare earth elements; weak negative Eu anomalies; enrichment in large‐ion lithophile elements (e.g., K, Th, Ba, and Rb); strong depletion in Ti; and weak depletion in Nb, Ta, and, Sr. These characteristics indicate that the granites from these plutons are S‐type granites. Second, the two‐mica granite and gneissic granite samples may have been formed by partial melting of ancient crustal material (mainly psammitic rocks), with contributions from a meta‐igneous component, under high‐temperature and low‐pressure conditions. Third, new data from this study, combined with previously reported dates, indicate a continental margin arc setting for the QB during the Early Neoproterozoic (ca. 900 Ma). [ABSTRACT FROM AUTHOR]

Detailed petrological, whole‐rock geochemical, and zircon Hf isotopic researches were conducted on the Late Carboniferous–Triassic sedimentary rocks in the Bogda region to evaluate the effects of weathering, sorting, and alteration, as well as to understand their provenance and tectonic setting. These rocks show variable major element compositions, but most are generally similar to post‐Archean Australian shales. The relatively narrow range of TiO2–Zr variation and good correlation between Th/Sc and Zr/Sc signify no obvious sorting and recycling of the sedimentary rocks. The relatively high index of compositional variability (0.8–3.1) and low chemical index of alteration values (44.4–76.4) of the sedimentary rocks indicate that they are immature and probably undergo weak to moderate chemical weathering. In the chondrite‐normalized diagrams, almost all the samples are distinguished by moderately enriched light rare earth element and flat heavy rare earth element patterns with negative Eu anomalies (Eu/Eu* = 0.5–0.8). In conjunction with their Th/Sc, Zr/Sc, La/Th, Zr/Al2O3, TiO2/Zr, Co/Th, and La/Sc ratios, we infer that the major sources of these sedimentary rocks were the intermediate–acidic igneous rocks from the North Tianshan and Yili–Central Tianshan. Combining the orientation of the Bogda region in the Palaeozoic that was roughly perpendicular to the Tianshan and/or East Junggar orogens with the sedimentologic, petrologic, and tectonic researches, we suggest that the Bogda region was a rift basin that occurs at high angles to the orogenic belt. On the other hand, the zircons from these sediments have minor Precambrian grains (<0.2%), positive εHf(t) values (mostly +7.1–+15.0) and young 2‐stage Hf model ages (major peak <1,000 Ma), suggesting that a juvenile continental crust exists as the basement of the Junggar Basin. The geochemical data reveal weakly to moderately weathering of the source, compositionally immature and poorly sorted.The rift model appears as the most likely geodynamic interpretation of the Bogda region.The juvenile continental crust exists as the basement of the Junggar Basin. [ABSTRACT FROM AUTHOR]

We present new zircon U–Pb ages, geochemical data on the Late Palaeozoic volcanic rocks of the Suji and Dahongshan formations, which are exposed in the Plate Marginal Orogenic Belt along the northern margin of the North China Craton. Our aim is to constrain the petrogenesis, tectonic setting of volcanic rocks, and to address the late stage tectonic evolution of the Paleo‐Asian Ocean. Lithologically, the Suji and Dahongshan formations present the main rock association with basaltic andesite, andesite, dacite, rhyolite, and tuff. New zircon U–Pb dating results suggest that the volcanic rocks formed during 280–261 Ma and 277–267 Ma, respectively. Geochemically, these volcanic rocks belong to the low‐K tholeiitic to high‐K calc‐alkaline series and are characterized by highly enriched light rare earth elements, K, Rb, Ba; depleted Nb, Ta, Ti; and highly negative Eu anomalies, very similar to that of the continental arc magmatism. These data, together with geological field investigations, suggest that the Early Permian volcanic rocks from Suji and Dahongshan formations were related to southward flat subduction of the Paleo‐Asian Ocean beneath the northern margin of the North China Craton. Therefore, these volcanic rocks were interpreted as Andean‐style continental margin arc magmatism. This also indicates that the final collision between the North China Craton and the Siberian Craton did not occur until the Early Permian. [ABSTRACT FROM AUTHOR]

In order to evaluate rare earth elements (REEs) as a potential proxy for solid bitumen classification, we employed traditional correlation approaches, such as carbon isotopes and V/(V + Ni) ratios, to infer the source rocks of Sinian-Cambrian reservoir solid bitumens in the Sichuan Basin and analyse solid bitumens for their REE compositions by inductively coupled plasma-mass spectrometry. Our data suggested that Sinian-Cambrian reservoir solid bitumens were primarily sourced from the lower Cambrian shales deposited under anoxic-euxinic conditions. REE and their associated parameters seemed to be more sensitive to classify solid bitumens than traditional correlation approaches. REE concentrations played a dominant role and fractionation degree between light and heavy REE and played a secondary role in solid bitumen classification. REE concentration and pattern in solid bitumens might be controlled by two processes, including inheritance from source rocks and water-rock interaction. The major factor controlling REE concentrations in solid bitumens was the type of organic matter of source rocks. Authigenic minerals in solid bitumens formed by water-rock interaction appeared to have little influence on REE compositions of solid bitumens because of their trace contents. Overall, REE could be used as a novel complementary approach to solid bitumen classification in complicated petroleum systems. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]