The LA-ICP-MS Zircon U-Pb Dating, Geology And Geochemistry, Tectonic Setting Of Several Important Intrusions From The North Part Of The Western Stage Of West Qinling And Their Relationship With Mineralization

Western Qinling orogenic belt is an important geological unit in China and the belt has undertaken a long and complicated geological tectonic evolution. Granite magmatism developed in the north part of west segment of western Qinling mountain area which is one of the important polymetallic deposits. The study on chronology, geochemistry and tectonic environment of the granite magmatism in north area of Western Qinling show theoretical and practical significance for understanding the tectonic evolution of western Qinling in Mesozoic and guiding the deployment of regional geological prospecting work.Previous researches about granite magmatism in Western Qinling are mainly focused in the east segment, but the study on granite in the west area is a little deficient. By the researth on chronology, major and trace elements, and isotope geochemistry of important granitic intrusions in study area, this paper set up the temporal and spatial evolution framework of granite, discuss the tectonic setting and petrogenesis, analyze the relationship between granite and mineralization, and provide information for the deployment of regional geological prospecting work. Five groups of LA-ICPMS zircon U-Pb dating data of granite in study area have been got. Combined with previous research achievements, we consider that the granite magmatic activity began from 264Ma, the latest period of middle Permian about 200Ma. The large-scale movement of magma occurred between early Triassic and late Triassic.The study on petrology and geochemical of 5 important intrusions show that there mainly are middle-acid intrusions and mostly granodiorite, monzogranite, granite and alkali feldspar granite in the west segment of Western Qinling. The most intrusions show the characteristics of Adakite, some Himalaya type. The Hf isotope data suggests that the granite has crust source including Paleoproterozoic crust and Proterozoic crust. Based on previous isotope researches, we consider that the basement of Western Qinling indicate the tectonic attribute of Yangzi block.The characteristics of Adakite and Himalaya-type show that the granite formed when crust became thicken. Combined with regional geology, we consider that in Triassic period the Western Qinling area are in continental stacking orogeny stage. There are continent- continent collision and overlay stage in late Permian- Triassic period, continental crust became thicken and partial melting, then formed granite magmatism with characteristics of Adakite and Himalaya-type.This paper points that the formation of gold-copper polymetallic mineralization related closely to the Adakite and Himalaya-type granite in Western Qinling. The enrichment mechanism of gold-copper et al has been analyzed. Combined with mineralization pattern analysis, the idea of carring out work plan around the prospecting in Adakite and Himalaya-type granite in study area has been proposed.