Mineralogical characteristics of the granitoid exposed in the Nanling Scientific Drill Hole and implications for magmatism and mineralization in the Yinkeng orefield, Southern Jiangxi Province

The Nanling Scientific Drilling-1 (SP-NLSD-1), a subproject of the SinoProbe Program called "Deep Exploration Technology and Experimentation", is situated at the Yinkeng orefield in the junction of Nanling and Wuyi Mountain metallogenic belts. The drilling project, with footage of 2967.83 meters, revealed rhyolite, granodiorite porphyry, granite porphyry and pyroxene diorite porphyry. The magmatic rocks are mainly composed of quartz, plagioclase, potassium feldspar, biotite, amphibole and some accessory minerals, with chloritization, carbonatization and muscovitization. Potassium feldspar is dominated by orthose. Plagioclases are different in granodiorite and granite porphyry. Andesines and albites are dominant in granodiorite porphyry and granite porphyry, respectively. Most of the biotites are eastonites. Derived from biotites, muscovites in granodiorite porphyry have low Al^VI and Fe/(Fe+Mg) values, while muscovites in granite porphyry have high values. Apatites are rich in F and Cl, and garnet belongs to grossularite. Chlorites are prochlorites and pycnochlorites. The chemical composition of biotite suggests that granodiorite porphyry was formed by magma derived from mixture of crust and mantle with relatively high oxygen fugacity, and had undergone magma mixing during the evolution. Granodiorite porphyry, granite porphyry, and pyroxene diorite porphyry crystallized at temperatures of 810-922℃, 764-819℃, 742-747℃, respectively. Comprehensive study suggests that granodiorite porphyry exposed in the Nanling Scientific Drill Hole is similar to granites related to Cu(-Mo)-Pb-Zn-Au-Ag deposits in Nanling region. The granodiorite porphyry is the ore-forming magmatite of Ag-Au-Pb-Zn-Cu mineralization and Niuxingba-Liumukeng deposit. The relationship between W-Bi-U mineralization and magmatism needs further research.