The Characteristics And Geological Significance Of The Triassic Granite In Alashan Engel In Inner Mongolia

Alashan region is located in the western part of Inner Mongolia autonomous region of China and is at the junction of the central Asian orogenic belt,the north China plate and the tarim plate.The magma activity in the study is frequent,the evolution time is long,the tectonic background is changeable,the rock type is complex,the ore-forming condition is superior.In this paper,engel wusu Triassic granite in alashan area was selected as the research object.The geochemical characteristics and geological significance of Triassic granites in the study area were discussed by using geochemical and structural geological methods on the basis of field geological survey and previous research results.The ngousu Triassic granite is mainly distributed in the south side of the ngousu ophiolite complex,which is an irregular rock spreading.According to the characteristics of rock field and petrography,the rock can be divided into medium and fine granitoids and medium granitoids.According to the u-pb isotopic dating of the la-icp-ms zircon,the orthogranite was formed in the early Triassic(247.7 + 3.2ma).The potassium-argon age of black mica has been obtained for 198 million years in the rocks of feldspar granite.Look from the work of geological data,this set of fine grained monzonitic granite intrusion in late Permian,fine grain adamellite and covered by the early cretaceous strata,the time should be between the late Permian to early cretaceous.The age of the Triassic is defined by reference to the predecessors and the materials obtained in this work.Geochemical analysis shows that the main body of Triassic granite shows the characteristics of calc-alkaline rock series.REE content of rare earth elements showed obvious-medium-negative europium anomaly.Cerium anomaly is not obvious and belongs to light rare earth enrichment type.It shows the characteristics of the crust resinous granite.From the perspective of constant elements and characteristic minerals,it is relatively biased towards type I granite.According to the structural discriminant diagram,the Triassic granite has the characteristics of normal arc granite with continental crust character,and the source of magma is the mixing of crust and mantle.Comprehensive analysis showed that the Triassic granites on behalf of the regional tectonic activity by ocean arc to continental arc in the late stage,both by plate collision stage of strong orogeny to plate the closed relatively calm post-tectonic uplift phase transformation process.It indicates that the Triassic alashan area has entered the stage of continental development.