The Genetic Relationship Between Yanshanian Granites And Tungsten-Tin Polymetallic Mineralizatio In Nanshan Area, Shixing County, Guangdong Province

The Nanshan granite pluton is located in the north of the Guidong composite granite pluton,a most representative granite pluton in Shixing county, north of Guangdong province, and in the south of the Beitou composite granite pluton. The north Guangdong area, where the Nanshan pluton is situated, is an mineralized area in China. This academic degree paper focuses the Nanshan tungsten-molybdenum polymetallic deposit and Nanshan granites as the host rocks of the deposit, to discuss lithogenesis mechanism and tectonic environment during the formation of the pluton, then to expounds the genetic relationship between Nanshan granite pluton and tungsten-tin polymetallic mineralization, based on the study of isotope age and geochemical characteristics of the host rocks.The Yanshanian granites are widely exposed in the Nanshan mineralized region. The Nanshan pluton mainly consists of fine-granied granites, two-mica monzogranites and middle porphyritic biotite granites. The SHRIMP zircon U-Pb age is 158.1±1.8Ma. The lithogeochemical features of Nanshan Yanshanian granites show that they exhibit high Si and alkali,strongly-peraluminous,low Ca and Mg,high TFeO/MgO and low CaO/Na2O, belonging to the aluminum alkaline granites. In trace element compositions, the granites are enriched in high strength field elements of Zr,Y,U,Nb, and depleted in Ba,Sr,Ti, indicative of a consistency with aluminum A-type granites. REE patterns are nearly horizontally V-shaped characteristic of A-type granites, with a stong depletion of Eu, indicating the magma experienced a strong crystallization differentation. Thus, the present study considers that the Nanshan granites are belongto H-type granites,which were formed by upwelling partial melting of the pelite and less clay-derived meet contaminated by the mantle-derived material in the condition of transition from relative compression to extenion.Nanshan tungsten-tin polymetallic deposit is a "multi-type" composite deposit. Mineralization types are mainly divided into three types,i.e. granite type tungsten-molybdenum,skarn type tin polymetallic and quartz vein type tungsten-molybdenum mineralizations. In terms of spatial distribution, granite type ore bodies are mainly controlled by the granites formed in the second intrusion and the third intrusion of the second phase of the Early Yanshanian movement,and occurred in the ore-forming granites and inner contact zone between ganites and their surrounding rocks;quartz vein type ore bodies are occurred in the inner contact and exocontact zones in the dome of the pluton, and controlled by joints and cracks produced during emplacement of the by granitic magma skarn type ore bodies are occurred in oxidized skarns and garnet-diopside skarns, which show a stratified occurrence,and obviously controlled by contact zone of the pluton.Ore-bearing granites in the Nanshan mineralized area belong to high differentational H-type granites. The consistency between lithogenesis age and metallogenic age also suggests a close relationship between lithogenesis and mineralization. To sum up, Nanshan granites provided metallogenic material,thermal source,hydrothermal fluid for mineralization, and represented as the minerogenetic parent rocks of the Nanshan tungsten-molybdenum polymetallic deposit. Basing on the characteristics of evolution of Nanshan granites and features of the deposit, this paper testified systematically relationship between Yanshanian granite pluton-related tungsten-tin polymetallic deposit in the Nanshan area,in which skarn type,quartz vein type are formed (controlled by joints and cracks) and granite type tungsten tin polymetallic ore bodis from top to bottom in the granite pluton.