Confirmation of the age,geochemical characteristics of Late Carboniferous rhyolite in Laoyemiao area,eastern Junggar,and their geological significance
East Junggar is an important part of the Central Asian Orogenic Belt(CAOB).In this paper,we study the petrological,geochemical characteristics and zircon U-Pb ages of the rhyolite exposed in Laoyemiao area of East Junggar,to discuss its petrogenesis and tectonic environment.Based on our research,the Laoyemiao rhyolite has the characteristics of high silicon,high potassium,riched in alkali,deficiency in Ca,P,Fe,Mg and Ti.It is riched in large ion lithophile elements(LILE)Rb,K,Th,Nb,Ta and high field strength element(HFSE)Zr,Hf;relatively poored in Ba,Sr,P,Ti.The enrichment of light rare earth elements(LREE)is obvious,and the internal fractionation of LREE is relatively strong.The internal fractionation of heavy rare earth elements(HREE)is weak,and the Eu negative anomaly is strong(δEu=0.12～0.65),showing a right-dipping seagull type.The average zircon saturation temperature is 878℃ and belongs to high temperature granite;the formation pressure is＜0.8 GPa and the depth is＜30 km.Similar to the typical A-type granite,the genetic type belongs to the A2-type rhyolite,which is produced in the post-collision environment.LA-ICP-MS zircon U-Pb dating shows that it formed at 311.6±3.1 Ma,belonging to the Late Carboniferous and the strata belongs to Batamayineishan Formation.Based on the data and regional geological features of the paper,the Laoyemiao area has been planted into the Siberian plate in the Late Carboniferous,and entered the transitional period of post-orogenic conversion into the plate.The lateral growth of the crust in the area was ended.However,due to the large amount of mantle-derived magma underplating,the area is still in vertical expansion.
East JunggarLaoyemiao areaA2-type rhyolitepost-orogenic environmentzircon U-Pb datingLate Carboniferous
万方数据
维普
