Formation and geodynamic implication of the Early Yanshanian granites associated with W-Sn mineralization in the Nanling range, South China: an overview

摘要

The Nanling range (Nanling) is characterized by intense and widespread Mesozoic magmatism related large-scale W-Sn mineralization. A summary of geochemistry, geochronology, and petrogenesis for the W-Sn-bearing granites has been carried out in this study. A series of rock- and ore-forming ages in Nanling indicate that the W-Sn mineralization is closely related to the Early Yanshanian granitic magmatism both in temporal and spatial dimensions (165-150Ma). Geochemical features show that both of the W- and Sn-bearing granites, which mainly belong to highly fractionated I-type granites with a few A-type granites, are characterized by high contents of SiO2, Al2O3, Na2O, and K2O; enrichment in Rb, Th, U, Zr, Hf, and REE; depletion in Sr, Ba, P, and Ti; and high ratios of A/CNK. Furthermore, the different Sr-Nd-Hf isotopic compositions indicate that they are mainly originated from the partial melting of the Precambrian basement rocks of the Cathaysia Block at low oxygen fugacity, and the estimated temperatures for the tungsten-bearing and tin-bearing granites are ca. 700 degrees C and ca. 800 degrees C, respectively. The model of the mantle-crust interaction exhibits that different percentages of mantle-derived magma were likely involved in the generation of the tin-bearing granites and tungsten-bearing granites. In combination with previous studies, we propose that these granites in Nanling were emplaced in an extensional setting, as a response to the break-off and roll-back of the subducted Palaeo-Pacific Plate during 175-150Ma.