Ore-forming System Of Guilinzheng-Huangshanling Doposit In Jiangnan Transitional Zone

Jiangnan transitional zone is located at between the Middle-Lower Yangtze River Valley metallogenic belt and tungsten molybdenum Tin mineralization belt of the Southern Anhui province, Jiangnan transitional zone developed intensive magmatic activity and metallogenic process. Based on the detailed geological character research, we using different analysis methods such as EPMA, LA-ICP-MS zircon U-Pb and Re-Os molybdenum dating aimed to study the metallogenic system of Guilinzheng-huangshanling deposit. Combined the results of previous researches, we discussed the petrogenesis and metallogenic process of this deposit as follows:The fertile magmas of deposit is mainly granite porphyry. The age of the zircon LA ICP-MS U-Pb dating is 126.8±1.4Ma(GLZ, n=24, MSWD=1,2) shows that the magma formed in the early Cretaceous. The geochemistry of magmas indicate that it belongs to peraluminous, high potassic-alkaline A-type granite. The porphyry composed of high SiO2 75.85%-76.82% and high alkalinity(NK/A=0.941-0.948, A/CNK=1.32-1.35, ALK=8.53%-8.82%). Depleted in LILEs(such as Sr, Ba)and HFSEs(Nb, Ta, P, Ti). This results suggests that the source of magmatic rocks is come from the lower crust, formed by the partial melting of F-rich granulite, and go through the fractional crystal process during the emplacement.The age of mineralization (Re-Os of the molybdenum) is 127.5Ma, it’s consistent with the geochronology of magmas,The Re content of molybdenum indicates that ore-forming materials are mainly derived from crust. The Guilinzheng-huangshanling skarn Mo-Pb-Zn deposit is formed in early Cretaceous. The processes of ore-forming can be divided into hydrothermal and supergene stages. It is in accordance with the typical characteristics of the skarn deposit.Through EPMA analysis of the garnet and diopside, the major element composition of garnets and diopside show the similar characteristic. Both are enriched in Al2O3 and depleted in FeO, Na2O and K2O, the characteristic indicate that the ore-forming fluids evolved from alkaline(high oxygen fugacity) to the acidic (low oxygen fugacity)environment, the value of PH gradually decrease during the precipitation of metal.The deep part of mineralization in Guilinzheng-huangshanling deposit is dominated consist of Mo, W, Zn, Fe, and the distal or shallow part mainly composed of Pb, Zn, Ag, Cu. In vertical zone gradually transfer from high-temperature minerals to low temperature minerals. The Ore-forming system is a compound system, controlled by intrusions, banded limestone strata(especially depleted As, Na2O-enriched) and the tectonism.Therefore, We divided the ore-forming process into three stages: 149-137Ma,134-119Ma and 116-110Ma respectively. This work revealed that the genesis of the Guilinzheng-Huangshanling deposit, enhanced the awareness of the diagenetic and metallogenic process of Jiangnan transitional zone, and provided a basis for the further prospecting work.