Abstract:

Caledonian intrusive rock body is newly discovered in the Maerzheng region in the south area of East  Kunlun. Based on zircon U-Pb dating，the age is determined to be Early Ordovician. The lithology is composed of some tonalite, a few of anorthosite and dioriteporphyry. According to research on petrologic and geochemical characteristics of intrusive rocks, the content of Na₂O is much richer than that of K₂O in basic and acid rocks, which shows characteristics of rich Na. The content of  Al₂O₃ s from 13.21% to 16.03%, and increases gradually from basic rocks to acid rocks. The content of Al₂O₃ is higher than the total content of K₂O, Na₂O, and CaO， showing that the rock belongs to an aluminium saturation type. The rock body is characterized by obvious fractionation of REE, enrichment of LREE，weak nagative Eu anomaly (δEu values are 0.61-0.94); the rock body is characterized by richment of Ba, Th, Zr and depletion of Nb. The lithologic combinations show the  characteristics of representative TTG. Combining with the geotectonic environment map of granite in the Maerzheng region, the intrusive rock body formed as a result of Tethys ocean subduction from south to north in Early Ordovician. The age of Maerzheng Formation in Earlymiddle Permian is redefined to be Early Ordovician according to the age of the intrusive rock body and field investigation.

Key words: granite, geochemistry, tectonic environment, Maerzheng