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

Mafic rocks similar to those of the Gangdese belt have been poorly reported in the Nabang area (SW Yunnan Province in SW China) of the Eastern Himalayan Syntaxis. This led to a widely-accepted assumption that Early Eocene mafic rocks are absent in Nabang. This paper reports new zircon U–Pb, Lu–Hf isotopic, whole-rock elemental and Sr–Nd isotopic data for the recently identified Tongbiguan and Jinzhuzhai metagabbroic plutons. Our data show that the two mafic plutons crystallized at 53.2 ± 0.4 Ma and 53.6 ± 0.7 Ma, respectively, with zircon in-situ ε Hf (t) values ranging from − 3.1 to + 4.9. Our data confirm the presence of Early Eocene mafic rocks in Nabang, contemporaneous with the major magmatic flare-ups of ~ 52 Ma in South Tibet. The rocks show high-K calc-alkaline basalt and basaltic andesite composition. They are characterized by subparallel spiky patterns with enrichment in LILEs, depletion in HFSEs and P–Ti negative anomalies. They show (Nb/La)n = 0.21–0.63, Ce/Pb = 2.99–9.91 and Nb/U = 5.2–14.1, along with high 87 Sr/ 86 Sr(t) ratios of 0.7061–0.7077 and ε Nd (t) values of − 3.4 to − 5.6. Such geochemical signatures are similar to those of the synchronous Dangxung gabbroic and Yangbajing ultrapotassic rocks. Their least-contaminated samples can petrogenetically be attributed to input of slab-derived fluid into the lithospheric mantle. In conjunction with other available data, the mafic suite can be geochronologically and geochemically correlated to those in South Lhasa and are probably the equivalents of the Gangdese southeastward extension. Their formation might tectonically be related to slab rollback in response to the decreasing convergence rate. The termination of the Neotethyan subduction in SW Yunnan might be later than ~ 52 Ma, identical to that in South Tibet. [ABSTRACT FROM AUTHOR]

The article examines the origin of submarine hydrothermal deposition through the petrologic and geochemical features of sediments at the Early Cambrian Niutitang Formation in South China. Information on the composition of the Niutitang Formation is given. It cites petrologic features that suggest an eruptive deposition. At the bottom of black shales, nickel-molybdenum polymetallic sulfide ores can be found in layer, bedded and lenticular forms.

[Display omitted] • The zircon and cassiterite U-Pb ages indicate that the granitic magmatism and related tin mineralization in this deposit were initiated approximately simultaneously in late Indosinian period. • The granites in this deposit are highly differentiated S-type granites derived from heterogeneous metamorphic sedimentary rocks in the crust. • A regional large-scale granitic magma intrusion and mineralization event occurred in late Indosinian (211–230 Ma) in South China. Indosinian W-Sn metallogeny associated with granites in South China has been reported in recent years by many researchers. However, the refined genetic relations between these deposits and the related granites remain unclear in most areas, and the tectonic setting of Indosinian magmatism and W-Sn mineralization are still widely controversial. The Banjiaoyuan tin deposit is located in the east vicinity of Yangmingshan pluton in the middle Nanling Range, South China. The granitic stocks in this deposit comprise two intrusive episodes, i.e., the first episode of medium-coarse-grained porphyritic tourmaline-biotite monzogranite (G1), and the second episode of micron-fine-grained tourmaline-muscovite monzogranite (G2). LA-ICP-MS zircon U-Pb dating gives weighted ages of 226.9 ± 1.6 Ma to 223.8 ± 1.9 Ma for G1, and 224.3 ± 2.0 Ma for G2, respectively. LA-MC-ICP-MS cassiterite U-Pb dating yields Tera-Wasserburg concordia age of 216.7 ± 2.4 Ma for tin mineralization. These ages indicate that both the granitic magmatism and related mineralization were initiated in the late Indosinian period. All the granites have high SiO 2 , Al 2 O 3 , P 2 O 5 contents, and low TFeO, CaO, MgO, TiO 2 contents, indicating that the granites are highly differentiated S-type granites, and furthermore, the high DI and Rb, K, U, Hf, Sm, low SI and Ba, Sr, Ti, TREE further show that the granites have undergone high extent of differentiation and evolution. High Rb/Nb and K/Nb ratios, low Nb/Ta and Zr/Hf ratios, widely varying CaO/Na 2 O ratios, low and uniform ε Nd (t) values, and dominantly negative and relatively dispersed ε Hf (t) values jointly indicate that the granites were derived from a heterogeneous mixture of calcium-poor mudstone and calcium-rich psammite (or metamorphic igneous rocks) in the crust. The known Indosinian W-Sn deposits in South China are more closely related to S-type granites than to I-type granites, suggesting that their ore-forming materials are mainly derived from the crust. In addition, individual positive ε Hf (t) values indicate that a small amount of newborn crustal components were involved in the formation of granitic magma. Compared with G1, G2 differs distinctly in petrological, chemical and isotopic characteristics, especially it is more richer in F content and contains magmatic cassiterite and wolframite crystals, suggesting that G2 have undergone higher extent of differentiation and evolution, and are much more closely related to the Sn-W mineralization than G1. The late Indosinian granites in this deposit were formed in post-collisional extensional tectonic environment, while the early Indosinian granites intruded in the Yangmingshan area were formed in syn-collision compression environment. Based on the statistics, the metallogenic ages of Indosinian W-Sn deposits in South China are between 212 and 230 Ma, and the petrogenetic ages of related granites are between 211 and 230 Ma, both age groups belong to the late Indosinian period, representing a regional large-scale granitic magma intrusion and mineralization event that initiated in post-collisional extensional tectonic environment. [ABSTRACT FROM AUTHOR]

Geochemical and isotopic data for metabasic rocks in NW Yunnan constrain the nature of the mantle source beneath the East Himalayan Syntaxis during the Neotethyan subduction and the timing of initial collision between India and Asia. Our results indicate that these mafic rocks crystallized at 50–55 Ma and were metamorphosed at ~ 39 Ma, contemporaneous with magmatic flare-ups and high-grade metamorphism in South Tibet. The mafic rocks in NW Yunnan are divisible into three groups. Group 1, from Nabang, shows geochemical affinity to a MORB-like source modified by the recycled component with ε Nd (t) of + 5.1 to + 9.5 and ε Hf (t) of + 5.1 to + 11.6, and resembles back-arc basin basalt. Group 2 is mainly from Jinzhouzhai and Tongbiguan to the east of Group 1, and is marked by high Al 2 O 3 , enrichment in LILEs and depletion in HFSEs, along with negative ε Nd (t) (− 1.1 to − 5.6) and ε Hf (t) (− 4.6 to − 0.9) values. Group 2 is interpreted to have originated from the lithospheric mantle modified by input from a slab-derived component in a continental arc setting. Group 3, from Nanjingli, is located a considerable distance east from Group 1, and exhibits negative ε Nd (t) (− 6.7 to − 7.6) and ε Hf (t) (− 7.1 to − 2.2), and is inferred to be derived from the Tengchong lithospheric mantle but with limited involvement of a slab-derived component. Overall Nd–Hf isotopic compositions show a sharp decrease from Group 1 to Group 2 and then a more subdued decrease to Group 3, with the three groups corresponding to an overall spatial distribution from west to east. Our results suggest that early Eocene magmatism in NW Yunnan represents the eastward continuation of the Gangdese magmatic belt and that the Neotethyan subduction continued until ~ 50 Ma followed by the India–Asia collision. It is proposed that at least two eastward-dipping subduction zones are involved in the Neotethyan suprasubduction system prior to 55 Ma. The sudden decrease in convergence rate in the early Eocene (55–50 Ma), together with the inferred positive buoyancy of the Tengchong lithosphere, stimulated rollback of down-going slab and induced melting of heterogeneous mantle sources to result in a flare-up in magmatic activity. [ABSTRACT FROM AUTHOR]

Abstract: The amalgamation process of the Yangtze with Cathaysia Blocks has been one of the disputed issues that have attracted considerable attention due to its significance in understanding the assembly and breakup of the supercontinent Rodinia. However, it has been a matter of debate as to the tectonic nature (plume vs. subduction/collision vs. plate-rift) and timing of the amalgamation (1000Ma vs. 880Ma vs. 800Ma) along the Jiangnan domain. To evaluate the previously proposed models and to constrain the final amalgamation timing of the Yangtze with Cathaysia Blocks, this paper presents a set of integrated geochemical and geochronological data for the high-mg volcanic sequence that is bounded between the Lengjiaxi and Banxi Groups. Two andesitic samples from the volcanic sequence (Cangshuipu) were dated at 824±7Ma (CSP-35) and 822±28Ma (CSP-8) using the SIMS and SHRIMP techniques, respectively. These samples have mg-numbers ranging from 71 to 25 with SiO2 of 57.51–73.80wt%, classified as high-mg andesite and dacite. They show significant enrichment in LILEs and depletion in HFSEs with marked negative Nb–Ta, P and Ti anomalies. Their ɛ Nd(t) values range from −1.7 to −4.7 and initial 87Sr/86Sr values from 0.7051 to 0.7123. The generation of the Cangshuipu high-mg rocks might have been attributed to an interaction of the subducted sediment-derived fluid with the overlying refractory mantle. The contemporaneous dacitic rocks should be the product of the highly fractional crystallization from the high-mg andesitic magma. Integrated with the regional geology and available geochronological data, we propose that the Cangshuipu volcanic sequence might have formed in a collisional setting related to the Neoproterozoic orogenic process along the Jiangnan domain. The final amalgamation of the Yangtze with Cathaysia Blocks along the Jiangnan domain probably occurred between 815Ma and 822Ma (probably 820Ma) rather than 1000Ma, ca. 880Ma or 800Ma as previously proposed. Taking into account the subsequent development of the Nanhua rifting (probably after 815Ma), it is inferred that a plate-rift model might be a more reasonable mechanism for the Neoproterozoic tectonic evolution along the Jiangnan domain. [Copyright &y& Elsevier]