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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]

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]

This paper reports mineral and whole‐rock geochemical data (major and trace elements, Sr–Nd isotopes, and in situ plagioclase Sr‐isotope analysis) for Cenozoic volcanic rocks from Sabeto, NW Fiji, with the aim of constraining the origin of Cenozoic shoshonitic rocks found throughout Fiji. The most mafic shoshonitic lavas (absarokites) exhibit porphyritic textures and massive structure with phenocrysts of olivine (Fo = 76–78), clinopyroxene (Mg# = 73.9–80.0), and plagioclase (An = 71.9–92.1). Major element geochemical data include SiO2 = 47.31–48.46 wt%, MgO = 4.20–5.76 wt%, Mg# = 49–51, Al2O3 = 17.64–18.93 wt%, and (Na2O + K2O) = 5.12–7.01 wt%. The trace element geochemistry is typically arc like, with enrichment in the large ion lithophile elements (LILEs), the light rare earth elements (LREEs), and P, along with depletion in the heavy rare earth elements (HREEs) and high‐field‐strength elements (HFSEs; e.g., Nb, Ta, Zr, Hf, and Ti). Whole‐rock (87Sr/86Sr)i ratios and εNd(t) values vary from 0.7037 to 0.7039 and from +7.62 to +8.45, respectively. The former is near equal to the 87Sr/86Sr ratios of plagioclase phenocrysts (0.7034–07039). Based on these geochemical data and the results of previous studies, we propose that the Sabeto shoshonitic primary magma was derived from partial melting of the depleted lithospheric mantle, modified by subduction‐related fluids. The thermobarometric calculation indicates that the P–T conditions of Fiji shoshonitic magma chamber are ~1100 °C and ~2.8 GPa (~90 km depth), with an average H2O fraction of ~6 wt%. In addition, the shoshonitic melts experienced fractional crystallization of clinopyroxene, olivine, and plagioclase during magma evolution. These volcanic rocks formed in an extensional setting following collision of the Vitiaz arc and the Ontong Java Plateau during the Pliocene. [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]

Newly recognized Late Carboniferous volcanic rocks occur in Ongniud Banner on the northern margin of the Sino‐Korean palaeoplate, including rhyolite, dacite, and related volcaniclastic. The volcanic rocks have for a long time been considered to form in the Early Permian. Our new LA‐ICP‐MS U–Pb zircon dating of two rhyolite samples and one dacite sample yielded ages of 305.6 ± 1.6 Ma, 312.2 ± 2.3 Ma, and 305.3 ± 1.7 Ma, respectively, corresponding to the Late Carboniferous. The volcanic rocks are enriched in light rare earth elements (LREEs) and large‐ion lithophile elements (LILEs) and depleted in heavy rare earth elements (HREEs) and high‐field‐strength elements (HFSEs, e.g., Nb, Ta). The positive zircon εHf(t) values (+6.64 to +9.49) of the volcanic rocks and the high Mg# values (47.05–51.47) of some samples indicate the contribution of mantle materials to the sources. Integrated with geological, geochemical, and Lu–Hf isotopic studies, it is considered the volcanic rocks formed in a subduction‐related continental margin arc setting. Combined with the studies in the southeastern part of the Central Asian Orogenic Belt on the ophiolitic mélanges, magamatic belts and sedimentary environment of the Late Palaeozoic, collision‐related granites, and so on; it is suggested that the southward subduction for the eastern segment of the Palaeo‐Asian Ocean beneath the northern margin of Sino‐Korean palaeoplate was still occurring in the Late Carboniferous. [ABSTRACT FROM AUTHOR]

The Mesa Virgen Calerilla (MVC) is located in the state of Zacatecas, Mexico. The most intense volcanism, which occurred during the Eocene, formed extensive ignimbrite deposits exposed in some parts as lava spills of rhyolitic (felsic) composition. This felsic volcanism may represent much of the MVC. This study describes whole‐rock geochemistry and mineralogy data from felsic volcanic rocks in the MVC to address their petrogenesis and tectonic setting. The MVC covers a compositional spectrum ranging from trachyte, dacite, to high‐silica rhyolite. The petrography and mineral assemblages indicate that the felsic rocks are composed of K‐feldspar (sanidine), quartz, plagioclase, and biotite. The felsic volcanic rocks have a composition of 64.08–78.17 wt% (SiO2)adj, 0.14–0.69 wt% (TiO2)adj, and 0.11–0.62 wt% (MgO)adj with 12–54 Mg number [Mg# = 100 × (Mg2+/[Mg2+ + Fe2+])]. These felsic volcanic rocks showed enrichment in light rare earth elements (LREE; [La/Sm]N = 3.80–7.19), and are depleted in heavy rare earth elements [HREE; (Tb/Yb)N ratios 0.35–1.84], along with negative Ba, Nb, Sr, P, Eu, and Ti anomalies. The geochemical characteristics and petrogenetic modelling indicate that felsic volcanic rocks are derived from partial melting process of an upper‐middle continental crust. The tectono‐magmatic model and multidimensional tectonic discrimination diagram indicate that an extensional‐related setting prevails for the MVC. [ABSTRACT FROM AUTHOR]

We present LA‐ICP‐MS zircon U–Pb dating, geochemical data for the Late Devonian–Early Carboniferous volcanic rocks in the Aksu River area, western end of the East Kunlun Orogen, with an aim to constrain the ages, petrogenesis, and tectonic setting of volcanic rocks and to comprehend the Late Devonian–Early Carboniferous tectonic evolution of the north branch of the Paleo‐Tethys Ocean. The Late Devonian–Early Carboniferous volcanic rocks are mostly composed of andesite and rhyolite. The new U–Pb ages show that the volcanic rocks formed in the Late Devonian–Early Carboniferous with ages of ca. 364–343 Ma. The volcanic rocks are classified as calc‐alkaline series. All of the volcanic rocks are characterized by enrichment in large‐ion lithophile elements (e.g., Rb, Ba, U, Sr, and K) and light rare earth elements and depletion in some high‐field‐strength elements (e.g., Nb, Ta, P, and Ti). The andesite samples have relatively high La/Nb (1.66–3.63) but low La/Ba (0.05–0.23) ratios, indicating the mantle source could be depleted mantle, and it had been metasomatized before partial melting. The rhyolite samples have low Nb/Ta and Zr/Hf ratios and Cr, Ni, and Co contents, which indicate that the material source was mainly crust derived and has experienced fractional crystallization process. Combined with our zircon U–Pb dating, geochemical data and geological field investigation, the tectonic setting of the Late Devonian–Early Carboniferous volcanic rocks is possibly related to the subduction process. Furthermore, the Paleo‐Tethys oceanic crust between the Bayan Har and East Kunlun‐Qaidam terrane northward subducted beneath the East Kunlun‐Qaidam terrane in the Late Devonian–Early Carboniferous, and the north branch of the Paleo‐Tethys Ocean between the Bayan Har and East Kunlun‐Qaidam terrane opening event should be earlier than this time (~364 Ma). [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]

The Beina Pb–Zn–(Ag) deposit is a newly discovered deposit situated in the southern Lhasa terrane, Tibet. LA‐ICP‐MS U–Pb dating for the ore‐bearing rhyolite porphyry indicates that it was emplaced at 64.6 Ma. The Beina rhyolite porphyry displays high SiO2 (74.31–76.52 wt%), K2O + Na2O (6.99–8.05 wt%), and A/CNK (0.97–1.33), similar to the peraluminous S‐type granites related to Pb–Zn–(Ag) mineralization in the central Lhasa terrane. The Beina rhyolite porphyry is strongly depleted in Nb, Ta, Ti, P, Sr, and Ba, enriched in Rb, K, Th, U, and Pb, enriched in light rare earth elements (LREEs), slightly depleted in heavy rare earth elements (HREEs) (LaN/YbN = 6.52–9.28), and has moderate negative Eu anomalies (δEu = 0.38–0.48), showing an arc affinity. It also shows high CaO/Na2O ratios (0.21–0.73), low Rb/Ba (0.30–0.46), and Rb/Sr ratios (1.17–4.01), indicating that it was mainly derived from partial melting of a clay‐poor, plagioclase‐rich metapsammitic source. The samples have relatively high 87Sr/86Sr(i) (0.7084–0.7092) and Pb isotopes (206Pb/204Pb = 18.61–18.74, 207Pb/204Pb = 15.65–15.68, 208Pb/204Pb = 38.99–39.14) and low εNd(t) (−8.6 to −7.2) and εHf(t) (−8.6 to −4.8) values, yielding ancient two‐stage Nd model ages (1,459–1,569 Ma) and two‐stage Hf model ages (1,433–1,684 Ma), respectively. The Beina rhyolite porphyry was formed at relatively high temperatures (average 817°C) according to zircon saturation thermometer. These results reveal that Beina rhyolite porphyry was generated by partial melting of ancient crustal materials (dominated by metapsammite) heated by mantle‐derived magma during rollback of the Neo‐Tethyan oceanic slab. In addition, our research suggests that both I‐ and S‐type granites related to Pb–Zn mineralization are believed to exist in the Lhasa terrane. Similar to the central Lhasa terrane, the middle segment of the southern Lhasa terrane (83°E–87°E) is also an ancient block, large‐scaled silicic volcanic rocks of the Linzizong Group, and coeval plutons are widely exposed and several Pb–Zn deposits have recently been discovered in the Nuocang–Chazi area. All these facts indicate that there is a great potential for prospecting of intrusions‐related Pb–Zn deposits in the middle segment of the southern Lhasa terrane. [ABSTRACT FROM AUTHOR]