Geochemical Characteristics And Tectonic Setting Of The Pingshi And Shadi Granitoid Pluton In The Gannan Region

The Gannan region is located in the southeast of the Cathaysia orogenic belt-east section of Nanling uplift belt.Magmatic activities are frequent in this area,and different types of magmatic rocks formed in the Cambrian-Silurian,DevonianMiddle Triassic,Late Triassic-Cretaceous and other geological periods.The magmatic rocks in the study area belong to the famous Luoxiao-Zhuguang batholith,and the research degree is higher.The study area is located in the eastern part of Nanling metallogenic belt,where yanshanian magmatic activity is the main metallogenic period.In the genesis of granites,S-type crust source granite is the main part,with the I-type crust-mantle source granite and the A-type non-orogenic granite.The study of granite in south China has been a long time,and it is a theoretical place for the study of granite in China.Compared with the study of yanshanian granitoids in south China,the study of Caledonian granitoids are relatively weak,and its tectonic setting is divided.This article selected two representative plutons,including Pingshi and Shadi as the research object,working in a detailed field geological,geochemical and LA-ICP-MS zircon U-Pb in research,on the basis of the study area to differentiate the era of granite,the genesis of granites,tectonic setting and other issues were discussed.The study area,using zircon U-Pb dating Pingshi pluton,two groups of granite can be measured crystallization age 457.1±3.9 Ma(MSWD = 0.0019)and 456.6±3.8 Ma(MSWD = 0.29),on behalf of the formation of the rock era,belongs to the Late Ordovician,the caledonian period magmatic activity product.Pingshi granites are characterized by high silicon,rich alkali and aluminum,and are mainly of aluminum,which is a series of high potassium calcium and alkali.The granites in Pingshi pluton have a large variation range,which belongs to the rich light rare earth type,and has the characteristic of weak-negative Europium.The high-field strength elements Ba,Th,Zr and Hf in the granites in Pingshi have the characteristics of crust source granite.The pluton is mostly aluminum S-type granite,which is the product of the melting of the shallow parts of the crust.Pingshi granite,the collisional orogenic granite is dominated,with the characteristics of collision and post-collision.The pluton has the s-type granite of the collisional orogeny,and the tectonic setting belongs to the late orogenic period.And the three groups of the Shadi granite is 433.3±7.4Ma(MSWD=0.089),431.3±3.7Ma(MSWD=0.110)and 427.9±4.6Ma(MSWD=0.0074),representing the formation of the pluton,which belongs to the Early Silurian,and is the product of the magmatic activity in caledonian stage.In the Shadi pluton,the acidity level is higher,which has the characteristics of high silicon,potassium rich and aluminum rich.The main characteristics of the main elements of Shadi granite are stronger than aluminum,which is a high potassium calc-alkali series.The rare earth elements of the Shadi granite have a large variation range,which belongs to the rich light rare earth type,with the abnormal characteristics of Europium.The relative enrichment of U,Nb,Zr,Hf and other elements has the characteristics of crust source granite.The Shadi pluton is mostly aluminum S-type granite,which is the product of the melting of the shallow parts of the crust.Shidi granite,the collisional orogenic granite is dominated,with the characteristics of collision and post-collision.The Shadi pluton pluton has the post-collision or post-orogenic environment of the pluton.