Chronology and geochemical characteristics of Late Indosinian Dengfuxian two-mica granite in eastern Hunan Province,China,and its significance

Dengfuxian granite is an Indosinian-Yanshanian multi-stage complex batholiths located in eastern Hunan Province,South China. Zircon LA-ICP-MS U-Pb dating of the Dengfuxian two-mica granite has been carried out. The results show that two samples have zircon U-Pb ages of 222. 9 ± 1. 6Ma and 224. 3 ± 2. 4Ma,respectively,demonstrating firstly the occurrence of the Late Indosinian two-mica granite in Dengfuxian batholiths. This Late Indosinian two-mica granite is strongly peraluminous with high Si and alkali contents. It is enriched in Cs,Rb,U and Pb,but depleted in Ba,Sr and Ti,and shows the similar geochemical characteristics to Indosinian strongly peraluminous granites in South China. The samples have high(87Sr /86Sr) i values( 0. 721463 ~ 0. 728115),low eNd( t) values(-11. 68 ~-11. 33) and Nd model ages of 1. 92 ~1. 95Ga. It is proposed that the Late Indosinian Dengfuxian two- mica granite would be derived from partial melting of the Paleoproterozoic crustal materials. The intrusive time of the granite is consistent with those of the Indosinian strongly peraluminous granites in South China. Based on the geochemical characteristics and regional geological features,it is considered that the late Indosinian Dengfuxian two-mica granite was formed in a post-collision extensional tectonic environment. The mineralization of the Dengfuxian tungsten deposit is genetically related to the Yanshanian granite. The Late Indosinian two-mica granite has a high content of tungsten,and might provide metals for later Yanshanian tungsten mineralization.