Geochemical Characteristics and Tectonic Setting of Late Varisian Period in Alashan Block
|Course||Mineral prospecting and exploration|
|Keywords||LA-ICP-MS U-Pb zircon age Granitoids of middle-late Varisian period geochemistry teconic setting Alashan region|
Granitoids are widespread in Alashan block, and their genesis and tectonic setting have been an issue hot debate at the present time. LA-ICP-MS U-Pb zircon age and ICP-MS are reported for geochronology and geochemistry of the granitoids there,to reasearch combining previous understanding and group’s research results,then discuss geochemical characteristics and tectonic setting of middle-late Varisian period granitoids in Alashan block and have achieved some recognition.Zircon U-Pb dating of the six spotted magmatogenic diorite-granite from the region was performed, yielding the 273.3±3.9Ma,272.6±3.4Ma,273.5±4.2Ma,250.8±3.3Ma,272.6±7.4 Ma,272.0±9.0Ma, suggesting the Crystallization age and that invading in the Late Early Permain.geochemical characteristics show that the Zongnaihill-shalazhahill plutons and Niuquan bayannuoergong plutons geochemical basic similar. Geochemical characteristics indicate that main rock type is granitoid, monzonite and dioritoid, A/CNK present that the granite has metaluminous-rich potassium, with shoshonitic to Kcalc-alkaline and high-Kcalc-alkaline. In the trace element primitive mantle normalized spider diagrams, Ba, Ta, Nb, Sr, Y, Tb negative anomalies clearly display. The REE distribu- tion curves are of right inclinnation, which indicates LREE enrichment and the deficiency of HREE, very few sample display negative Eu anomalies...The granite is product of the tectonic transition from compression to introplate extension,it fromed in post-collisonal environment.