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The Sichuan-Yunnan-Guizhou Pb-Zn metallogenic province, located in the southwestern margin of the Yangtze Block, is the most intensively developed region of carbonate-hosted Pb-Zn deposits in China. Both the number of Pb-Zn deposits/spots (more than 500) and the amount of Pb and Zn metal reserves(more than 2000×104 t)play an important role in the Pb-Zn metallogenic regions/belts of China. Although the previous research has made fruitful theoretical understanding and prospecting achievements, there has been a dispute on the source of ore-forming materials of the Pb-Zn deposits in the study area. A systematic In-situ Pb isotope analysis of galena from nine Pb-Zn deposits hosted in the Sinian(Wusihe, Chipu, Yinchanggou and Maozu deposits), Devonian (Huodehong, Maoping and Maozachang deposits) and Carboniferous(Maoping, Huize, Liangyan and Maozachang deposits)carbonate rocks was carried out. The results show that ① the In-situ Pb isotopes of galena in all deposits have an obvious linear relationship, and their Pb-Pb isochron age is about 2.5 Ga ((2 574±30)Ma); it is suggested that the sources of ore-forming metals for these deposits are the same, and the Archean-Paleoproterozoic crystalline basement rocks are the most likely major metal source; ② in the age of ore-bearing strata, the Pb isotopes gradually increase from the old (Sinian) to the new (Carboniferous); in the space of ore-bearing horizon, the Pb isotopes gradually increase from Wusihe, Chipu deposits in N(W) to Maozachang, Liangyan deposits in S(E); it is indicated that they are the evolvement products of the same ore-forming fluids in different stages, and the crystalline basement-derived and/or flowed ore-forming fluids evolve and migrate from deep to shallow, and from N(W)to S(E)on a regional scale. [ABSTRACT FROM AUTHOR]

Crystalline basement and Precambrian crustal growth of the continental massifs within the Central Asian Orogenic Belt (CAOB) are still pending problems. Our geological and geochemical investigations identified an Archean (2606 Ma) granitic pluton in the Biliya area of the Erguna Massif. The Neoarchean granitoids show high and positive in‐situ zircon ∊Hf(t) (+0.3 to +10.0), whole‐rock ∊Nd(t) (+4.8) and whole‐rock ∊Hf(t) values (+2.1). They are characterized by high Y + Ce + Zr + Nb (> 220 ppm) and Zr contents and could be classified as A‐type granites. These granitoids are characterized by high Zr saturation temperatures (TZr) (796–836°C). They were derived from partial re‐melting of juvenile mafic lower crust in an intracontinental back‐arc extensional environment. This newly identified Neoarchean granitic pluton may represent the crystalline basement of the several continent massifs within the CAOB, and their high ∊Hf(t)–∊Nd(t) values may also indicate the occurrence of lateral crustal growth events in these massifs during the Neoarchean. [ABSTRACT FROM AUTHOR]

The Dabashan nappe structural belt links the Hannan block to the west with the Huangling block to the east between Yangxian and Xiangfan. The Dabashan arc-shaped fold belt formed during late Jurassic and was superposed on earlier Triassic folds. To achieve an improved understanding of the deep tectonics of the Dabashan nappe structural belt, we processed and interpreted the gravity and magnetic data for this area using new deep reflection seismic and other geophysical data as constraints. The results show that the Sichuan basin and Daba Mountains lie between the Longmenshan and Wulingshan gravity gradient belts. The positive magnetic anomalies around Nanchong-Tongjiang-Wanyuan-Langao and around Shizhu result from the crystalline basement. Modeling of the gravity and magnetic anomalies in the Daba Mountains and the Sichuan basin shows that the crystalline basement around Nanchong-Tongjiang-Wanyuan-Langao extends to the northeast underneath the Wafangdian fault near Ziyang. The magnetic field boundary in the Zhenba-Wanyuan-Chengkou-Zhenping area is the major boundary of the Dabashan nappe thrusting above the Sichuan Basin. This boundary might be the demarcation between the south Dabashan and the north Dabashan structural elements. The low gravity anomaly between Tongjiang and Chengkou might be partly caused by thickened lower crust The local low gravity anomaly to the south of Chengkou-Wanyuan might result from Mesozoic strata of low density in the Dabashan foreland depression area. [ABSTRACT FROM AUTHOR]