Petrogenesis and tectonic implications of the intermediate-acid plutons in Shatanjiao ore-field, Tongling, Anhui

The Tongling area of Anhui Province is a famous copper-gold polymetallic ore concentration area dominated by skarn and porphyry type deposits in China. The widely exposed intermediate-acid intrusive rocks in the area are closely related to mineralization. The Shatanjiao ore-field is located in the eastern part of the ore concentration area. The Shatanjiao, Guihuachong and Yaojialing rock bodies and their copper, gold and zinc deposits of different scales and mineralization types are exposed. Rock bodies play an important role in controlling mineralization. On the basis of previous studies, a detailed studies on petrography, geochemistry and zircon U-Pb chronology for Shatanjiao, Yaojialing and Guihuachong plutons in the ore-field were carried out in order to find out the petrogenesis of these plutons and their forming tectonic setting. Geochemically, the three plutons have a metaluminous characteristics, all of which belong to high-potassium calc-alkline series Ⅰ-type granites with depletion in HREE, Nb, Ta, and enrichment in LREE, Rb, Th, and slightly negative Eu anomaly. The zircon U-Pb age of the Yaojialing pluton is 140.4-140.9Ma, while the Shatanjiao pluton formed relatively earlier (141.4-144.1 Ma), and the Guihuachong pluton formed later (138.3Ma). Combined with the regional geology, we infer that these plutons in the ore-field were emplaced in the early Cretaceous extended environment, which is crystallized from a mixed magma between a differentiated basaltic magma derived from the enriched mantle and a felsic magma from the partial melting of crustal fusible component.