Study On Geological-Geochemical Characteristics And Ore Genesis Of Neidong W-Mo Polymetallic Deposit In Zhuguangshan Composite Pluton

Neidong W-Mo polymetallic deposit is located in the center of Zhuguangshan composite granite pluton which is a famous metallogenic pluton for nonferrous metal deposits in the middle segment of Nanling Mountains. This article focused on the W-Mo polymetallic deposit and closely associated Yanshanian granite intruded in the first and third episode. Based on the study of detailed field study, petrography, petrochemistry, rare earth elements, trace elements,soil geochemistry, and fluid inclusions approach aiming at characteristics and sources of ore-forming fluids, sources of ore-forming materials, ore-control factors and ore genesis. The main conclusions we got are as follow:First, Yanshanian granite intruded in the first episode has experienced a high degree of crystallization differetiation and the interaction process between fluid and rock, it is the main source of ore-forming materials and an important ore-control factor. Second, Neidong W-Mo deposit is hosted in the secondary fault of the major NE-trending fault zone, it is controlled by the fault, the regional NE-trending fault belt serve as ore-transmitting structure and its secondary fault is the major host structure. Third, the primary mineralizing fluids are of Na2SO4-NaCl-H2O type with low salinity, the ore-forming temperatures mainly vary from 200℃to 350℃, which obviously show that mineralization occured at high-medium temperature stage. Ore-formation occured in middle-shallow metallogenic environment, metallogenic pressure and metallogenic depth are estimated to be 20.6～27.7Mpa and 2.1～2.8km respectively. Fourth, based on comprehensive research on geological features of ore deposit, evidence from ore-forming fluids and wall rock alteration, Neidong W-Mo Polymetallic deposit is charactered as a middle-shallow and high-medium temperature hydrothermal fluid deposit hosted in a fault zone,and formed during the process of filling and metasomatism.