The Genetics Of The Ore-bearing Granit Of Baizhangyan W-Mo Deposit In Qingyang Country, Anhui Province

Baizhangyan fine-grained granite is produced in the northeastern part of Jiangnan Transitional Zone, which is an important ore-bearing granite of Baizhangyan W-Mo deposit. This paper systematically studied the geological and geochemical characteristics of the ore-bearing granit of Baizhangyan W-Mo deposit and discussed the source of magmatic perogenic material, tectonic setting, petrogenesis, material resource and metallogenic mechanism of W-Mo deposit. The main achievements obtained in this paper are as follows:The Baizhangyan granite outcrops as a NE trending tongue shape with fine-grained granitic texture and massive structure. The rock mainly composed of potassium feldspar, plagioclase, quartzand and biotite.According to the geochemical characteristics, Baizhangyan granite rock can be classified into highly fractionated I-type granite. The characteristics of trace elements and Sr-Nd isotopic show that the source of the magma is derived from the low metamorphic rock in the middle and upper crust of the Yangtze Block. The magma was formed under the extensional tectonic setting during the early Cretaceous. Paritial melting and fractional crystallization had played an important role in the magma evolution mechanism.The magma source might be the metamorphic rock of the Shangxi Group in the upper crust. Lithospheric thickening and subsequent delamination in Eastern China had caused asthenosphere upwelling at Yanshanian. The magma formed from crust partial melting was raised along with the regional fault to the upper crust, therefore formed Baizhangyan fine-grained granite.The deposit was produced in the contact zone between the fine-grained granite and Latian Fromation. The main orebodies is controlled by the carbonate rocks. The orebodies are layers like in shape. Ore structure are dominated by disseminate. The major ore minerals are composed of scheelite, molybdenite, chalcopyrite. Gangue minerals assemblages of diopside, garnet, amphibole, plagioclase and quartz. Alterations in granitic rocks consists of greisenization, skarnizarion marmarization, diopsidization, chloritization and kaolinitization. According to the orebody occurrence and the ore mineral assemblage, Baizhangyan W-Mo deposit can be classified into skarn-type deposit. The ore-forming process could be divided into skarn stage and hydrothermal stage. Skarn stage could be further divided into simple skarn stage and complex hydrothermal skarn stage, and hydrothermal period could be further divided into quartz-sulfide stage and carbonate stage. W-Mo mineralization was mainly occurred in the complex hydrothermal skarn stage and quartz-sulfide stage. The formation of deposit is controlled by the magmatism of Baizhangyan fine-grained granite and hydrothermal process.