The Characteristics Of Qushenla Group's Volcanic Rocks And Tectonic Significance In Zanzongcuo,Shuanghu County,Tibet

Formation and evolution of the Himalayan-Tibetan orogenic system has long been one of the international geological studies of the hot issues.The Tibetan Plateau has experienced the subduction of Tethyan oceanic lithosphere(involving the Proto-Tethys,Paleo-Tethys Neo-Tethys)and the India-Asia continental collision,in the processes of which widespread magmatic activities occurred.Study Bangongcuo – Nujiang suture zone which widespread Mesozoic magmatism forunderstanding the formation of the entire Tibetan plateau has important implications.Based on double lake county in Tibet with great mistake area to collect to "pull volcanic rocks as the research object,combined with previous studies in the region,to the group with field observations of rock,the microscopic petrography mineral identification,the main trace element geochemical testing,zircon age testing research,discusses the class Qushenla group volcanic rock formation and class male lake nujiang suture zone of tectonic evolution history.In this paper,we study Qushenla group volcanic rocks in south of Shuanghu county,Tibet is mainly a series of neutral volcanic rock is given priority to,acidic volcanic rock in The Times of including different colors of andesitic porphyrite,rough surface andesite,dacite,rock assemblage;Mineral composition of amphibole,plagioclase,quartz,etc.The set of combination of geochemical characteristics of rocks in the acidic volcanic rock.Trace element analysis indicates that the group of rock has the characteristics of island arc volcanic rocks,enrichment of large ion lithophile elements,loss of high field strength elements.The REE chondrite standardized distribution shown in the diagram to the right curve,the Eu is abnormal.Zircon age to detect the acidic volcanic rock in the era of emplacement is about 115 Ma.Thus provides the Mesozoic class and nujiang oceanic basin in the south to cut evidence of the subduction.