Inspiration from the age of Baoerhantu Group and metamorphic zircon age of middle early middle Triassic in the northern Damao Banner,Inner Mongolia
This paper is the result of rock geochemistry.[Objective]The Baoerhantu Group is mainly distributed in the northern region of Damao Banner and is a key area for studying the early Paleozoic tectonic evolution of the ancient Asian Ocean.[Methods]This article conducts petrological,geochemical,isotopic geochemical and chronological studies on the basic volcanic rocks in the Baoerhan map of Damaoqi area,in order to explore their formation age and diagenesis.[Results]The LA-ICP-MS zircon U-Pb diagenetic age of the gneiss like plagioclase amphibolite in the Baoerhantu group was 495±2.0 Ma,while metamorphic zircon ages of 242.3±1.1 Ma and 249±3 Ma were obtained in the amphibolite greenstone and plagioclase amphibolite,respectively.[Conclusions]The geochemical characteristics of the gneiss like plagioclase amphibolite are characterized by enrichment of large ion lithophilic elements such as Rb and Th,and depletion of high field strength elements such as Nb,Ta,P,and Ti,indicating that the Baoerhantu Group had volcanic eruptions during the Cambrian(ε3),and its formation is related to the subduction of the ancient Asian Ocean from north to south.The hornblende epidote and plagioclase hornblende exhibit MORB type geochemical characteristics,and the captured zircons contain both the ancient recycled continental crust material of the North China Plate and the newly formed basic lower crust material of the Paleozoic era,which can limit the closure of the ancient Asian Ocean to be earlier than 249 Ma.
万方数据
维普
