Discussion On The Yanshan Epoch Rock Characteristics And Ore-forming Background In Zhejiang Kaihua Region

Kaihua area located in Zhejiang west hollow zone between the Yangtze and Cathaysian plate, where the area Tectonic-magmatic activity is strong in Yanshan epoch. In this paper mainly research in selecting from Kaihua area Tongcun, Lishanling, Shuangyuanlin, Shangsanzhi, Tianjingwu granite porphyry,which formed in Yanshan epoch. By geochemical, LA-ICPMS, ESR Etc, studying the geological background in Yanshan epoch, and comparing with Adjacent areas with large porphyry porphyry ore deposits to evaluate the potential mineralization. Achieved the following understanding:Tongcun, Shuangyuanlin, Shangsanzhi, Tianjingwu pluton belong to Potassium calc-alkaline granite. Lishanling belong to peraluminous Potassium calc-alkaline granite.the pluton devide two class:one represented by Tongcun, including Shuangyuanlin, Shangsanzhi, Tianjingwu pluton, REE patterns figure with the same graph melt-type porphyry (I type), Trace elements is similar to the "island arc" environment rock characteristics; The other represented by Lishangling pluton, REE was "Seagull"-typeIs what is a typical type granites of crustal re-melted, trace elements character indicate from the crust,belong to S-type granite.Tongcun, Lishanling, Shangsanzhi pluton LA-ICPMS Zircon U-Pb dating determine Tongcun pluton Intrusion time in 168-165 Ma; Lishanling pluton Intrusion time in 144.3-135.7 Ma; Shangsanzhi pluton Intrusion time in 155.8 Ma. Zhejiang West Kaihua area Yanshanian pluton Intrusion main time in Mesozoic Jurassic, part in early upper Cretaceous.Early Yanshan epoch,Cathaysian and Yangtze plate revive, Collision and extrusion–orogen, Cathaysian plate thrust above the Yangtze plate, caused the crustal thickening and magmatism strongly. Tongcun, Shuangyuanlin, Shangsanzhi, Tianjingwu pluton response to the collision between Cathaysian and Yangtze plate in early Yanshan epoch. late Yanshan epoch, into extensional intraplate evolution after post-orogen, structural transformed, from the compression belt to stretching, mantle upwelling, magmatic activity still strong period.Lishanling pluton is responsed to after intraplate evolution after post-orogen.Using ESR dating method test quartz vein in tongcun profile, combined with stress field and Geological background Analysis. Kaihua area has a strong tectonic -magmatic activity in the late Yanshan (about 100-120 Ma). Cracks were formed in the Cretaceous (100-120 Ma), while hydrothermal activity,filled with quartz vein.Comparing with the neighboring metallogenic belt in northeastern Jiangxi and southern Anhui belts mineralized porphyry,Tongcun, Lishanling, Shangsanzhi pluton Metallogenic potential reach the size of northeastern Jiangxi.