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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]

The Zhaojinggou Nb–Ta deposit is one of large rare metal deposits newly discovered in the northern margin of the North China Craton in recent years. This paper reports petrography, petrochemistry, columbite‐group minerals U–Pb chronology study of the amazonite granitic pegmatite (AGP) exposed in this deposit, and composition of columbite‐group minerals and biotite are obtained by electron probe microanalyzer and LA‐ICP‐MS. Eighteen analyses of columbite‐group minerals yielded weighted mean 206Pb/238U age of 116.9 ± 1.4 Ma. The crystallization temperature of biotite is 630–650°C, and the oxygen fugacity is 10−17–10−18 bars. The biotite has low MgO contents and high Rb, Rb/Sr, and FeOT/(FeOT + MgO) ratios. The AGP has extremely low MgO, Cr, Co and Ni contents, with Nb/Ta ratios range from 1.63 to 9.05 and Rb/Sr ratios range from 303.30 to 648.90, and obvious 'M' type tetrad effect of rare earth element indicating that the formation of the AGP is related to crust‐derived magma. The contents of Nb2O5 and FeO decrease, while the Ta2O5 and WO3 contents, Mn# and Ta# values increase gradually from the core to the rim of columbite‐group minerals. Some columbite‐group minerals have unobvious oscillatory zoning, and some have a clear bright zoing with high Ta contents on the rim, indicating that the genesis of Zhaojinggou Nb–Ta deposit is mainly magmatic crystallization differentiation, accompanied by hydrothermal autometasomatism in the late stage. [ABSTRACT FROM AUTHOR]

This paper presents new zircon U–Pb–Hf isotopic and whole‐rock geochemical data for early Paleozoic–early Mesozoic igneous rocks from the Zhangguangcai Range, which are used to provide constraints on the petrogenesis and tectonic setting of these rocks and on the tectonic evolution of the eastern Songnen Massif. We dated five igneous rocks from the Zhangguangcai Range of the eastern Songnen Massif, namely, a late Cambrian (~489 Ma) syenogranite, a middle Silurian (~431 Ma) dacite, a Middle Triassic (~247 Ma) gabbro‐diorite and two Late Triassic (214–210 Ma) rhyolites. The late Cambrian syenogranite, middle Silurian dacite and Late Triassic rhyolites have high SiO2 and (Na2O + K2O) contents and low Mg# values. These four rocks are enriched in light rare earth elements (LREEs) and large‐ion lithophile elements (LILEs) but depleted in heavy REEs (HREEs) and high‐field‐strength elements (HFSEs). In addition, the εHf(t) values and TDM2 ages of zircons from these rocks range from −1.31 to +5.88 and from 1264 to 896 Ma, respectively. These data suggest that their primary magma was derived from partial melting of the juvenile mafic lower crust that was generated during the Mesoproterozoic–Neoproterozoic. The Middle Triassic gabbro‐diorite has low SiO2 and high MgO, Sc, Co, Cr and Ni contents and is enriched in LILEs and LREEs but depleted in HREEs and HFSEs such as Nb and Ta. Combining these features with the zircon εHf(t) values of the gabbro‐diorite, which range from +0.02 to +1.79, the primary magma of this rock is inferred to have been derived from partial melting of an isotopically depleted lithospheric mantle. The late Cambrian syenogranites and the middle Silurian dacites are weakly peraluminous and are classified as medium‐ to high‐K calc‐alkaline series, indicating that they formed in an active‐continental‐margin setting. The Middle–Late Triassic igneous rocks exhibit a bimodal igneous rock association, suggesting that they formed within an extensional environment. Combining our new results with previous findings, the early Paleozoic–early Mesozoic tectonic evolution of the eastern Songnen Massif is revealed. During the early Cambrian–early Silurian, the oceanic plate between the southern Songnen and southern Jiamusi massifs subducted westward beneath the Songnen Massif. The amalgamation between the southern Songnen and southern Jiamusi massifs occurred during the middle Silurian, and the southeastern Songnen Massif was in a post‐collisional extensional setting during the Devonian. During the late Carboniferous–Triassic, the Zhangguangcai Range was in an extensional environment, and the Mudanjiang Ocean started to open along the Jiayin–Mudanjiang Fault, separating the Songnen and Jiamusi massifs during the Middle–Late Triassic. [ABSTRACT FROM AUTHOR]

The Kelameili suture located between the eastern Tianshan Junggar Plate and the Harlik island arc in east Tianshan. This suture is well known as identifying the Kelameili ophiolite and the Tucker Takezale ophiolitic melange. This paper first reports a new discovery of the Shihuiyao ophiolite, which is 70 km away from the Takezale ophiolitic mélange to the east. It is mainly composed of the variable serpentinized peridotite, metagabbro, and minor siliceous rocks. The serpentinite and gabbros are characterized by high content of Al2O3 and normal mid‐ocean ridge basalt (N‐MORB)‐type rare earth element compositions. These rocks also show a typical characteristic of origin of island arc setting with depletion of high‐field strength element (HFSE) and enrichment of large‐ion lithophile element (LILE). The LA‐ICP‐MS dating of zircon grains from gabbros gave a weighted mean 206Pb/238U age of 352 Ma, which was interpreted to represent the age of the Kelameili Ocean. This paper provided an important constraint on the tectonic evolution of the Kelameili Ocean. [ABSTRACT FROM AUTHOR]

The Lower Jurassic clastic rocks in the Qiangtang Basin, northern Tibet, are generally regarded as the early sediments of the new Mesozoic Qiangtang Basin (Late Triassic to Early Cretaceous). However, little attention has been paid to the palaeoenvironment, provenance, and tectonic setting of this unit. The QZ‐16 well, located in the east of the northern Qiangtang Basin, firstly recovered the Lower Jurassic strata (Quemo Co Formation) in the Qiangtang Basin. In this paper, the whole‐rock major‐trace elemental characteristics of 34 mudstone samples and detrital zircon geochronology of one sandstone, collected from the Quemo Co Formation of the QZ‐16 well, are reported in order to infer the palaeoenvironment, provenance, and tectonic setting. Quemo Co mudstones are dominated by SiO2 and Al2O3, while Fe2O3, CaO, K2O, and MgO are the second most abundant oxides. They are generally characterized by high REE concentrations, enrichment in light rare earth elements (LREEs), marked negative Eu and Ce anomalies. The REE contents of the mudstones are mainly controlled by terrigenous detrital minerals input. The Lower Jurassic mudstones have relatively high chemical index of alteration (79.1–83.6) values, indicating moderate to high degree of chemical weathering conditions of the source area. Sr/Ba and Rb/K ratios reflect that the marine transgression impact was limited and the mudstones were generally deposited in a brackish water environment. Major, trace, and REE contents indicate that the mudstones were mainly derived from intermediate igneous rocks with subordinate felsic igneous rocks. Prominent age peaks at ca. 200 ~ 400 Ma, 700 ~ 970 Ma, 1,700 ~ 1,900 Ma, and 2,100 ~ 2,700 Ma of the detrital zircon grains suggest that the Lower Jurassic clastic rocks were derived from the Central Qiangtang and Songpan–Ganzi complex. Moreover, tectonic discrimination diagrams based on major and trace elements show that the source of the Lower Jurassic sediments were most likely derived from a collision tectonic setting. [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 new zircon U–Pb ages and Hf isotopic compositions of felsic units of the Abor volcanic rocks (AVR) of Eastern Himalayan Syntaxis (EHS), Northeast India, and discusses their relationship to the Kerguelen plume activity. The AVR are bimodal and predominantly constituted by mafic rocks with minor felsic units. Mafic volcanics are identified as basalt and basaltic andesite with light rare earth elements (LREE) enriched and slightly depleted heavy rare earth elements (HREE) pattern without Eu anomalies. Low concentrations of LILE, high contents of Fe2O3, and other incompatible trace elements ratios reflect enriched nature of these mafic volcanics. Felsic volcanic rocks are dacitic to rhyolitic in composition, which have high REE content, high LREE/HREE, and pronounced negative Eu anomalies. Enriched LREE, high Th/Nb, Ce/Nb ratios, and variations in Rb/Zr, K/Rb, La/Sm ratios with negative anomalies of Ba, Nb, Sr, P, Ti in felsic rocks suggest substantial contribution of crustal contamination at the time of eruption. Zircons from felsic units yield an average U–Pb age of ~132 Ma and unradiogenic (ƐHf(t) < 0) Hf isotope values of −7.0 to −13.3 with model ages between 1.5 and 2.1 Ga, suggesting old crustal assimilation in their genesis. The AVR were emplaced in the continental rift tectonic setting, and depth of the magma source is confirmed as near spinel stability zone. The AVR are positively comparable with other flood basalts that were formed due to the Kerguelen plume activity. Therefore, our combined new geochemical and geochronological data show that the AVR were emplaced at early stage (~132 Ma) of eastern Gondwana breakup due to outbreak of the Kerguelen plume. This study thus supports the idea of the Kerguelen plume affecting a large area of Eastern India, Western Australia, and Antarctica during early stage of Gondwana breakup. [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 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]

The Compostela area is located in the western Trans‐Mexican Volcanic Belt, which consists of volcanic rocks that produced during the Pliocene to Recent volcanism. In this paper, we present petrography, whole‐rock major‐ and trace‐element concentrations, Ar–Ar ages, and Sr–Nd isotopic data of volcanic rocks from the Compostela area in the south of the city of Tepic, Nayarit, Mexico. These volcanic rocks are of intermediate composition and belong to the transitional series: basaltic trachyandesites [52.72–53.94 wt% SiO2; 0.69–2.53 wt% MgO] and subalkaline series: low‐Si [55.11–60.94 wt% SiO2; 0.79–2.74 wt% MgO] and high‐Si [61.60–62.71 wt% SiO2; 0.36–0.80 wt% MgO] andesites. The 40Ar/39Ar dating of two basaltic trachyandesites yields plateau ages of 1.05 ± 0.15 Ma and 1.07 ± 0.17 Ma and the andesites yielded a plateau age of 2.42 ± 0.36 Ma. These results indicate that the studied rocks were formed during the Pleistocene in two discrete episodes. The basaltic trachyandesites show enriched light rare earth elements patterns relative to high rare earth elements [(La/Yb)N = 5.81–8.07] with negligible Eu anomalies. The andesites display enriched large‐ion lithophile elements (Ba, K) with anomalies of Nb (Th/Ce) and Ti in the three groups identified in the subalkaline series. The basaltic trachyandesites appear in a tight cluster of initial 87Sr/86Sr ratios (0.703519–0.703882) as compared to the basaltic andesite 87Sr/86Sr (0.704073) and positive ɛNd(t) values of +5.6 to +3.4, respectively, indicating that the basaltic trachyandesites were derived from intermediate magmas from a shallow mantle source. Geochemical modelling reveals that both basaltic trachyandesite and andesite rocks were derived by a process of crystal fractionation accompanied by assimilation of crustal rocks at the lower or middle level. Geochemical ratios and multidimensional discrimination diagrams, combined with the cross‐section of the subduction zone indicates that basaltic trachyandesites were generated from a rift and/or Ocean Island Basalt‐type source, whereas andesites were generated from a slab‐derived source in a subduction environment. [ABSTRACT FROM AUTHOR]

Due to the lack of corresponding magmatic records, the timing of the opening of the Yarlung–Tsangpo Neo‐Tethyan Ocean remains controversial. The Middle Permian Luerma igneous complex, which is situated in the western Gangdese magmatic belt of the southern Lhasa subterrane, western Tibet, can be divided into four or more rock types, including foid gabbro, amphibole gabbro, monzogabbro, and pyroxene‐bearing monzodiorite. Through zircon U–Pb dating using laser ablation–inductively coupled plasma–mass spectrometry, the age of the Luerma igneous complex is determined to be ~261 Ma. The complex is rich in titanium, iron, magnesium, and total alkalis, with medium to high levels of calcium, potassium and aluminium, as well as low levels of silicon. Therefore, it is classified as a shoshonite–latite rock series. The complex is relatively enriched in light rare earth elements and high‐field‐strength elements, without obvious Eu and Ce anomalies. These rocks exhibit relatively low (87Sr/86Sr)i values, high εNd(t) values, and high εHf(t) values. The geochemical and isotopic characteristics indicate that the magmas are derived from partial melting of the upper mantle in an intraplate tectonic environment. The new data presented here provide supplementary evidence for the initial rifting of the Lhasa terrane from the northern margin of Gondwana during the Middle Permian. These data also confirm that the opening of the Yarlung–Tsangpo Neo‐Tethyan Ocean occurred in the Middle Permian. [ABSTRACT FROM AUTHOR]

A large volume of Early Cretaceous volcanic rocks are exposed in the central Lhasa subterrane, which are essential for models developed for understanding the evolution of Lhasa Terrane. However, the petrogenesis and geodynamic background of these rocks are still in debate. In this paper, we carried out a detailed study on the volcanic rocks of the Zenong Group, including andesite, dacite, and rhyolite from the Coqen area in the central Lhasa subterrane. Zircons from one dacitic tuff yields an age of 115.3 ± 1.1 Ma. All the rocks are enriched in light rare earth elements (LREEs), Th, U, and Pb and depleted in high field strength elements (HFSEs, e.g. Nb, Ta, P, and Ti). The dacite and rhyolite samples are high-K calc-alkaline to shoshonitic and are metaluminous to peraluminous. These felsic samples are characterized by negative ƐNd(t) (−8.9 to −2.1) and ƐHf(t) (−8.1 to −5.6) and have high radiogenic Pb isotopic composition (206Pb/204Pb = 18.6287-19.5578, 207Pb/204Pb = 15.7161-15.7720, and 208Pb/204Pb = 39.1440-40.6253). Particularly, a negative correlation between the ƐNd(t) values and SiO2 contents can be observed in these dacites and rhyolites. Meanwhile, the andesites exhibit similar Sr-Nd-Pb isotopic compositions to dacites and rhyolites (ƐNd(t) = −4.3; 206Pb/204Pb = 18.7119-18.8575, 207Pb/204Pb = 15.7159-15.7203, and 208Pb/204Pb = 39.2944-39.6036). Our new data indicate that different geochemical reservoirs are involved in generating the ca. 115 Ma magmatism in the central Lhasa subterrane. It is likely that dacites and rhyolites are derived from the magma mixing between the ancient basement-derived melts and mantle-derived melts with varying degrees of partial melting. The andesites might originate from partial melting of an ancient lithospheric mantle that have been metasomatized by fluids and/or melts derived from the Tethyan oceanic slab. Our results, together with recent studies, suggest that the Zenong Group volcanic rocks in the Coqen area may represent the magmatic responses to the break-off of the southward subduction of the Bangong-Nujiang Tethyan oceanic slab. [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]

In this study, textural relations coupled with mineral chemistry of hydrothermal magnetite, fluorapatite, monazite and allanite from the Mohuldih uranium deposit in the Singhbhum Shear Zone (SSZ) is used to characterize the nature of the fluid during various events of alteration and uranium precipitation. These minerals have two distinct textural types, the earlier of which are coeval with the uraninite mineralization. The later type formed during subsequent hydrothermal overprint as a result of coupled dissolution‐reprecipitation of earlier fluorapatite and mobilization of light rare earth elements. Uranium‐lead dating of texturally‐constrained hydrothermal monazite grains yields two major concordant age clusters at 1855 ± 7 Ma and 963 ± 10 Ma and several discordant analyses. Two spot analyses furnish concordant ages of 1656 ± 33 Ma and 1438 ± 35 Ma that are identical within error of the 207Pb/206Pb ages (1628–1643 Ma and ca. 1392 Ma) of several discordant data points. Similar ages have been reported by other studies from the rocks of the SSZ and are therefore considered to be geologically meaningful. The oldest age of ca. 1855 Ma obtained from the texturally early core regions of monazite corresponds to the earliest stage of uraninite mineralization. The two main alteration types can be interpreted based on the known metamorphic events in the SSZ. A combination of high‐temperature calcic iron ± sodic and high‐temperature potassic iron alteration accompanied the M1 metamorphic event and the low‐temperature silicification/K‐Al alteration during the M2 metamorphic event. A comparative study between our data on magnetite and fluorapatite compositions with those from global iron oxide‐Cu‐gold (IOCG) and iron oxide‐apatite deposits classifies Mohuldih as an IOCG‐type deposit. [ABSTRACT FROM AUTHOR]

To date, the evolutionary history of the Proto‐Tethys Ocean that separated the Gondwana and Laurasia continents remains ambiguous. The Changning‐Menglian Suture Zone assumingly represents the Proto‐ and Palaeo‐Tethys suture in the Sanjiang area (the Yunnan Province, southwestern China). The Palaeozoic Proto‐Tethys Ocean in the Manxin area in the southmost Changning‐Menglian Suture Zone is widely recognized, but the timing and formation mechanism of the Manxin ophiolitic mélange are poorly understood. In this study, we present petrographical, geochronological and geochemical data of the Manxin ophiolitic mélange situated in the Changning‐Menglian Suture Zone. We found that this ophiolitic mélange is composed of pillow basalt, metamorphic gabbro, diabase dike, and altered peridotite. The mafic rocks could be divided into two groups based on geochemical characteristics: (1) Mid‐ocean ridge basalt (MORB) [formed at 446.0 ± 3.2 Ma and exhibiting depleted light rare earth element (LREE) patterns and high ƐNd(t) (+5.7 to +8.4)] Trace element and isotope analyses indicated that the MORB was derived from a spinel‐facies depleted mantle. (2) Ocean island basalt (OIB) [crystallized at 460.2 ± 6.0 Ma]. ƐNd(t) (+5.7) and significant enrichments in large‐ion lithophile element (LILE) and light rare earth element (LREE) were identified, while the trace element and isotope systematics suggested that the OIB rocks originated from partial melting of the garnet‐spinel lherzolite mantle. Overall, we clearly constrained the timing and nature of the Manxin ophiolitic mélange using the proposed data, thus further supporting the notion that the Manxin ophiolites represent remnants of the Proto‐Tethys Ocean. [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]

This study provides relevant data on the granodiorite in southern Zhuguangshan, South China Block (SCB), including mineralogical information, zircon U–Pb ages, zircon Hf isotope data, whole‐rock geochemical data, and Sr–Nd–Pb isotopic data. These data indicate that the granodiorite in southern Zhuguangshan crystallized at approximately 448.7 Ma. The hornblende and micas of the granodiorites are magnesio‐hornblende and Mg‐rich biotite, respectively. The granodiorite samples are characterized by relatively high SiO2 contents of 61.72–66.19 wt.%, K2O contents of 3.77–5.18 wt.%, Na2O contents of 2.42–3.16 wt.%, low FeOT contents of 3.93–5.79 wt.%, and relatively high MgO contents of 1.78–2.55 wt.%, with Mg# values (molar Mg/[Mg + Fe] × 100) of 43–50. The contents of rare earth elements (REEs) in the granodiorite specimens are 166–283 ppm, and the REEs show both a chondrite‐normalized REE pattern that inclines rightward and slightly negative Eu anomalies (0.62–0.90). The Fuxi granodiorite is rich in large‐ion lithophile elements (LILEs; Rb, Th, U, and K) but is depleted in high‐field‐strength elements (HFSEs; Nb, Ta, and Ti). All the samples have similar Sr–Nd–Pb and zircon Hf isotopic compositions and have a (87Sr/86Sr)i ratio of 0.707319–0.710888, a (143Nd/144Nd)i ratio of 0.511705–0.511760, a (206Pb/204Pb)t ratio of 17.918–18.459, a (207Pb/204Pb)t ratio of 15.711–15.813, and a (208Pb/204Pb)t ratio of 37.953–38.563. The εNd(t) and εHf(t) values range from −7.12 to −5.88 and from −9.81 to −4.45, respectively, with corresponding two‐stage Nd model ages of 1.66–1.76 Ga and two‐stage Hf model ages of 1.55–1.78 Ga. These findings indicate that the granodiorite is magnesian andesite and that the magmas are derived from a mixture of crustal and mantle materials. Based on these findings in combination with previous research results, it can be concluded that the mantle beneath the Cathaysia Block was moderately depleted during the Early Palaeozoic and that Early Palaeozoic magmatism may be related to Early Palaeozoic oceanic crust subduction. [ABSTRACT FROM AUTHOR]

The mineralization in this area is more closely related to the shoshonitic Niuxinshan meddling complex (NIC), which helps to depict concurrent edge magmatism metallogeny. In the present investigation, new geochronological and geochemical data are combined with previously disseminated isotopic data from granitic rocks in the NIC to establish the situation of the region's structural setting change and determine its bearing on territorial metallogeny. The new geochronological data suggest that structural change could have occurred between 155 and 185 Ma. The granitic rocks of the NIC can be geochemically divided into two groups. The geochemical signature of one group displays high rare earth element (REE) designs with irrelevant Eu anomalies, lower Yb, higher Sr, and negative Nb–Ta–Ti (NTT) abnormalities, demonstrating a volcanic‐curve climate with a thickened outside layer in a focalized setting. The other group has level REE designs with obvious regrettable Eu anomalies, higher Yb, lower Sr, and moderate NTT anomalies, indicating an intra‐plate extensional climate with a decreasing outside. According to geochronologic and isotopic data, the mineralization is Late Jurassic (155 Ma). This has been deciphered to be hereditarily associated with the crystallization of the complex's shallow crustal‐sourced bits. In addition, a structural model is presented that provides a possible explanation for the abundant polymetallic mineralization that occurs in the northern margin of the NCC after 155 Ma. [ABSTRACT FROM AUTHOR]

Cenozoic tectono‐magmatism in Iran is widely considered to be related to subduction of the Neo‐Tethys Ocean. We employed whole‐rock and mineral geochemistry and isotopic data of intrusive rocks from Tafresh, central Urumieh‐Dokhtar magmatic arc, to evaluate the role of the mantle in magmatism, to assess the timing of emplacement, and to interpret the tectonic setting. Rock compositions range from gabbro or gabbro‐diorite (plagioclase + pyroxene ± olivine), to diorite (plagioclase + amphibole ± pyroxene), to granodiorite (quartz + plagioclase + K‐feldspar + amphibole + biotite), exhibiting high‐alumina calc‐alkaline affinity. Major oxide and trace element variations vary systematically from less to more evolved rocks suggesting a major role for fractional crystallization processes. Zircon LA‐ICP‐MS U–Pb ages of major rock types are in the range of 24–19 Ma, whereas those of gabbroic dikes are ~17.5 Ma. ԐNd values range between −1.8 and 3.7, and (87Sr/86Sr)i is narrowly restricted to 0.705–0.706, suggesting a common mantle source. The enrichment in light rare earth element (REE) enrichment and flat heavy REE patterns couple depletion of Nb–Ta–Ti indicate that subducting oceanic crust had interacted with the overlying mantle wedge. High‐alumina, mid‐Mg# Tafresh plutonic rocks formed from hydrous melts from which Ca‐pyroxene and magnetite crystallized earlier than plagioclase, whereas late‐crystallizing zircon nucleated while magma traversed through lithospheric mantle and Cadomian crust. Modelling of isotope and incompatible‐element patterns suggests the contribution of no more than ~5% molten sediment or other crustal components in Tafresh magma, at a developmental stage before most plagioclase and amphibole had crystallized. The Miocene Tafresh plutons originated during the final stages of subduction, before the collision between the Arabian and Eurasian plates. [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 metamorphosed Sadegh‐Abad granite from the north Shahrekord Metamorphic Complex (NSMC) of Sanandaj‐Sirjan Zone in west Iran shows evidence of ductile deformation. The augen to banded mylonitic granite (orthogneiss) involves sharp contacts with other rock units, including high‐grade metamorphic rocks, such as eclogite, amphibolite, and garnet amphibolite as well as schists. U–Pb zircon dating reveals that the crystallization of the granitic magma occurred at 568 ± 14 Ma (Late Neoproterozoic, Ediacaran). The Sadegh‐Abad mylonitic granite comprises high SiO2 (67–78 wt.%) and Na2O (3.23–7.79 wt.%) contents and low CaO (0.73–1.61 wt.%) and variable K2O concentrations (0.08–4.6 wt.%). The chondrite‐normalized REE diagram shows enrichment in LREE relative to HREE (Ce/Yb)N = 1.90 to 6.12), a negative Eu anomaly (Eu/Eu* = 0.10–0.66), and nearly flat HREE patterns (Tb/Yb)N = 0.94–1.44). These are interpreted to have originated from a continental crustal source. This is further supported by the high concentration of the alkali elements, U, Th, Rb, and the high 87Sr/86Sr(i) isotopic ratios (0.7086 to 0.7163). The lower HREEs abundances, negative Eu anomalies, and the low contents of mafic minerals may infer that partial melting of continental crust has taken place in low‐pressure conditions within the plagioclase stability field, possibly of pre‐existing calc‐alkaline bodies in the lower continental crust. The charge of heating probably occurred via the injection of mafic magmas into the tonalitic and granodioritic continental crust. [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 geochronology of tuffaceous sandstone and elemental geochemistry of mudstones in the Lower Permian Zhanjin Formation (well QZ‐5) in the Central Qiangtang Basin were studied to determine their depositional age, provenance, tectonic setting, and depositional conditions. Twenty‐six synchronous igneous zircons from tuffaceous sandstone at 596.5 m have a weighted average U–Pb age of 292.5 ± 2.5 Ma, tentatively constraining the sedimentary age of the Zhanjin Formation to the Early Permian. Low SiO2/Al2O3 and Th/Sc ratios indicate a low sedimentary recycling and compositional maturity for the source area of the Zhanjin Formation mudstones. The low Al2O3/TiO2, moderate‐high Fe2O3/Al2O3, high TiO2/Fe2O3, low‐moderate TiO2/Zr, and moderate Co/Th ratios combined with post‐Archean Australian shale‐normalized rare earth element distributions imply that the provenance of the Zhanjin Formation mudstones was mainly from the mixed mafic and felsic sources that is composed of basalt and rhyolite exposed in the Central Qiangtang Basin. The tectonic discrimination plots, low Fe2O3/TiO2, (La/Ce)N, and high Al2O3/(Al2O3 + Fe2O3) ratios reveal that the studied mudstones mostly formed in rift settings, consistent with the geologic evolutionary history of the Early Permian Qiangtang Basin. Trace element ratios (V/Cr and Cu/Zn), enrichment factors (MoEF), and δCe values combined with sedimentary features indicate that almost all the studied mudstones were deposited in an open marine environment along the continental margin, and were associated with oxic and dysoxic water columns. [ABSTRACT FROM AUTHOR]

The Mogok metamorphic belt (MMB) in central Myanmar is well known for its complex tectonics, magmatism, and metamorphism in the framework of Tethyan subduction and India–Asia collision. It is also world renowned due to the gemstone‐class rubies and sapphires. Identification and discrimination of those petrological units in this region therefore are important for understanding the gemstone mineralization. Ultramafic massifs also crop out together with the gemstone‐bearing metamorphic rocks in the MMB. It is still poorly constrained about their origin (i.e., mantle peridotites of Jurassic–Cretaceous ophiolites or cumulate rocks) and their relationship with the gemstone generation. Here, we report petrological and geochemical data for the Mogok ultramafic rocks. Petrographic observations show that they have typical cumulate textures, with a crystallization order of olivine/spinel‐orthopyroxene‐clinopyroxene. They have low whole‐rock Al2O3 and CaO, and extremely high spinel Cr# (=Cr/[Cr + Al]; up to 0.86). Clinopyroxenes of these rocks show light rare earth element enriched patterns when normalized to CI chondrite. The results suggest that the Mogok ultramafic rocks have different compositions, both whole‐rock and mineral, from mantle peridotites of Myanmar ophiolites, such as the Kalaymyo and Myitkyina ophiolites, but resemble typical Alaskan‐type ultramafic cumulates. Therefore, the Mogok ultramafic rocks are cumulates generated by high‐pressure crystallization of hydrous arc melts, probably during the subduction of the Tethyan oceanic slab. We argue that the emplacement of these arc melts may have provided additional heat for the earlier magmatic rocks and regional high‐temperature metamorphism, although there is a need to further constrain the ages of these rocks. This, along with magmatism and metamorphism during post‐collisional extension, probably collectively contributed to the generation of world‐class coloured gemstone mineralization. [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]

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 origin of high Ba‐Sr magmatic suites with adakitic features has remained controversial, although they provide important clues on the evolution of continental lithosphere. Here, we present petrological, geochemical, zircon U–Pb and Lu‐Hf data from an Early Cretaceous volcanic suite of andesitic‐dacitic composition in the Laiyuan complex of the central North China Craton, with a view to gain insights on the magma source, petrogenesis, and tectonic implications. The volcanic suite represented by rocks of andesitic‐dacitic composition shows enrichment in light rare earth elements (LREE) and large‐ion lithophile elements (LILE), and depletion in high‐field‐strength elements (HFSE) with no obvious Eu anomalies. They also show typical adakitic features such as high Sr/Y and La/Yb ratios, as well as high Ba‐Sr concentrations. Zircon U–Pb geochronology indicates that these rocks were formed in Early Cretaceous during 131 to 127 Ma, with εHf(t) values ranging from −23.5 to −19.4, suggesting enriched lithospheric mantle source. The geochemical and isotopic data show that the enriched lithospheric mantle source experienced fluid‐related subduction metasomatism. The distinct geochemical features of these identified in our study including high Ba‐Sr concentrations and adakitic affinities were not only inherited from their magma source, but are also a result of fractional crystallization during magma evolution including amphibole‐dominated fractional crystallization at depth and limited plagioclase removal. The volcanism in the Taihang Mountains occurred under extensional regime triggered by the subduction and rollback of the Paleo‐Pacific slab during Late Jurassic to Early Cretaceous and consequent thermal‐mechanical erosion of the lithospheric mantle. [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]

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 Tekturmas ophiolite belt of central Kazakhstan is located in the western Central Asian Orogenic Belt. It consists of three structural‐formational zones: Tekturmas (centre), Bazarbai (north), and Sarysui (south). The Tekturmas zone includes igneous and sedimentary rocks of Karamurun, Tekturmas, and Sarytau formations, which are dominated by volcanogenic, deep sea, and clastic deposits, respectively. The Bazarbai zone consists of Kuzek and Basarbai formations dominated, respectively, by basaltic and sedimentary rocks. The Sarysui zone includes terrigenous Airtau and olistostromic Ermek formations. The age of sedimentary rocks was constrained by microfossils. The igneous rocks of the Karamurun and Bazarbai formations are alkaline and subalkaline basalt/dolerite, andesibasalt, and andesite. There are three main groups of rocks: high‐Ti, mid‐Ti, and low‐Ti. The high‐Ti Karamurun volcanics and low‐Ti Bazarbai are variably enriched in light rare earth element (LREE) showing LREE enriched (high‐Ti) and LREE flat (low‐Ti) REE patterns. The high‐Ti group shows enrichment in Nb, Th, Zr, and Sm compared with the low‐Ti group. The low‐Ti group is special for the Nb troughs in primitive mantle‐normalized multi‐element diagrams, which are typical of supra‐subduction settings. Both groups yielded positive εNd values, although the averages are 4.6 and 7.5 for the high‐ and low‐Ti rocks, respectively. The geochemical features suggest formation of the igneous rocks in oceanic and supra‐subduction (intra‐oceanic arc) settings. The geological and geochemical features of the Tekturmas ophiolite belt accord well with the tectonic emplacement of ophiolites and formation of accretionary complex at a Pacific‐type convergent margin similar to those of the western Pacific. [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 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]

Petrological, geochemical, and zircon U–Pb geochronological features of Archean ultramafic–mafic complexes formed in subduction‐related settings provide significant insights into mantle source and geodynamic processes associated with subduction–accretion‐collision events in the early Earth. Here, we investigate a suite of serpentinized dunite, dunite, pyroxenite, and clinopyroxenite from an ultramafic complex along the collisional suture between the Western Dharwar Craton (WDC) and the Central Dharwar Craton (CDC) in southern India. We present petrology, mineral chemistry, zircon U–Pb geochronology, rare earth element (REE), Lu–Hf isotopes, and whole‐rock geochemistry including major, trace element, and platinum‐group element (PGE) data with a view to investigate the magmatic and metasomatic processes in the subduction zone. Mineral chemistry data from chromite associated with the serpentinised ultramafic rocks show distinct characteristics of arc‐related melt. Zircon U–Pb data from the ultramafic suite define different age populations, with the oldest ages at 2.9 Ga, and the dominant age population showing a range of 2.8–2.6 Ga. The early Paleoproterozoic (ca. 2.4 Ga) metamorphic age is considered to mark the timing of collision of the two WDC and CDC. Zircon REE patterns suggest the involvement continental crust components in the magma source. Zircon Lu–Hf analysis yields both positive and negative εHf(t) values from −3.9 to 1.5 with Hf‐depleted model ages (TDM) of 3,041–3,366 Ma for serpentinised dunite and −0.2–2.0 and 2,833–2,995 Ma for pyroxenite, suggesting that the magma was sourced from depleted mantle and was contaminated with the ancient continental crust. Geochemical data show low MgO/SiO2 values and elevated Al2O3/TiO2 ratios, implying subduction‐related setting. The serpentinized dunites and dunites show mild LREE enrichment over HREE, with relatively higher abundance of LILE (Ba, Sr) and depletion in HFSE (Nb, Zr), suggesting fluid–rock interaction, melt impregnation, and refertilization processes. The PGE data suggest olivine, chromite, and sulphide fractionations associated with subduction processes. Our study on the Mesoarchean to Neoarchean ultramafic complex provides important insights to reconstruct the history of the crust–mantle interaction in an Archean suprasubduction zone mantle wedge. [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]

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]

A number of Late Mesozoic (ca. 130 Ma) A‐type granitic plutons have been identified in Southeast (SE) China. The Lingshan pluton, located in the Gan‐Hang Belt, is a typical one which is mainly composed of coarse‐grained biotite monzogranite in the pluton centre and medium‐ to coarse‐grained syenogranite on the margin. Zircons from three representative samples show U–Pb ages of 132.0 ± 1.3, 134.4 ± 2.1, and 133.0 ± 1.9 Ma, respectively, indicating that the Lingshan pluton were formed in the Early Cretaceous. The Lingshan granites display typical A‐type affinities, with high SiO2, K2O, Na2O + K2O, rare earth element (REE) and high field strength element (HFSE) contents, high Ga/Al and Fe# [FeOT/(FeOT + MgO)] ratios and Zr + Nb + Ce + Y contents, and apparent depletion of Ba, Sr, Ti, and Eu. The calculated zircon saturation temperatures (TZr) are high, ranging from 841 to 966 °C (mean of 886 °C). The εHf (t) values and TDM2 (Hf) of the Lingshan granites mainly vary from −3.0 to 0.2 and 1.18 to 1.38 Ga, respectively. Consistently, the εNd(t) values vary from −3.9 to −2.8 and TDM2 (Nd) range from 1.16 to 1.26 Ga. These isotopic data indicate that the Lingshan granites were likely to be generated by partial melting of Mesoproterozoic metamorphic basement rocks with the involvement of a certain amount of mantle‐derived materials. Subsequent fractional crystallization processes were also suggested during subsequent magma evolution. We propose that the ca. 130 Ma Lingshan granites together with other coetaneous A‐type granitic rocks from adjacent region indicate a back‐arc extensional setting in SE China during Early Cretaceous. The extension event might be caused by the rollback of paleo‐Pacific Plate which results in upwelling of the asthenosphere and subsequently induces a high degree partial melting of Mesoproterozoic basement sedimentary material, to generate the A‐type granitic plutons along the Gan‐Hang Belt. [ABSTRACT FROM AUTHOR]

Geochemical and zircon U–Pb age data on granites of the Chitrial area, situated at the NE part of the Eastern Dharwar Craton, are presented to elucidate their petrogenesis, time(s) of emplacement, and role in crust formation. Based on field and geochemical characters, these granites are classified as alkali feldspar/monzo‐granite. Whole‐rock data of selected samples show evolved calc‐alkaline and peraluminous characters with high SiO2, K2O, large‐ion lithophile element, and light rare earth elements (LREE), depleted heavy rare earth elements (HREE) and strongly negative Eu anomaly. One sample shows slightly different character with low SiO2, enriched light rare earth elements, and depleted heavy rare earth elements without Eu anomaly. Geochemical analyses suggest that the rocks are S‐type granite with syn‐collisional and volcanic arc signatures. These granites define a coherent trend favouring low pressure crystallization of the magma. U–Pb zircon data show that the crystallization ages of the granites vary within 2514 ± 10 to 2525 ± 24 Ma. The geodynamic evolution of the Eastern Dharwar Craton is discussed wherein subduction and deep burial of sediment is envisaged to cause partial melting and granite genesis in the craton. [ABSTRACT FROM AUTHOR]