西准噶尔庙尔沟后碰撞花岗岩微量元素和Nd-Sr同位素特征及成因

TRACE ELEMENT AND Nd-Sr ISOTOPE CHARACTERISTICS OF THE POST-COLLISIONAL GRANITOIDS FROM MIAOERGOU WEST JUNGGAR, AND IMPLICATION FOR PETROGENESIS

西准噶尔庙尔沟岩体主要包括钾长石花岗岩、角闪二长花岗岩和花岗闪长岩.它们有着相似的同位素和微量元素地球化学特性.Ⅰsr(300 Ma)=0.704 0~0.704 5,而εNd(T)=+6.6^+8.4.模式年龄(TDM)大约分布在0.37~0.62 Ga,时间上和早古生代岛弧建造和洋壳的形成时间大致吻合.庙尔沟地区后碰撞花岗岩的特征,反应其源区是来自亏损地幔,可能是早古生代期间形成的洋壳和岛弧建造.西准噶尔地区的基底是年轻的地壳,古老地壳即使有也非常有限.

Rock types of the post-collisional granitoids in Miaoergou, West Junggar, include K-feldspar granite, hornblende monzogranite and granodiorite. These rock types show similar geochemical and isotopic characteristics, with Isr(300 Ma) = 0.7040 ~ 0.7045,εNd(T) = +6.6 ~ +8.4. Nd model ages calculated for these rocks range from 0.37 Ga to 0.62 Ga, which are broadly consistent with the forming ages of the early Paleozoic oceanic crust and arc systems in West Junggar. The geochemical and isotopic features of the Miaoergou post-collisional granitoids indicated that their source material was derived from a depleted mantle, probably, the oceanic crust and arc systems produced in the early Paleozoic. Our new data suggest that the basement of West Junggar is dominated by juvenile crust (younger than 600 Ma), and old continental crust is minor, if there are any.