东昆仑中西段分水岭北地区早三叠世中酸性侵入岩地质特征及成因探讨

Study on Geological Characteristics and Genesis of Early Triassic Intermediate-acid Intrusive Rocks in the North of Watershed in Middle and West Section of East Kunlun

摘要:

东昆仑中西段分水岭地区分布有大量的早三叠世中酸性侵入岩，其岩性组合为浅灰白色中粗粒花岗闪长岩—似斑状花岗闪长岩—闪长岩。早三叠世中—酸性侵入岩中常量元素具有铝质花岗岩、钙碱性系列岩浆岩的特征；微量元素地球化学特征显示岩石具有火山弧花岗岩特点；稀土元素地球化学特征显示轻稀土元素相对富集、重稀土元素相对亏损、轻重稀土分馏较明显。岩石学和地球化学特征表明，研究区早三叠世中酸性侵入岩可能为俯冲作用下火山弧环境中的产物。

Abstract:

A large amount of early Triassic intermediate-acid intrusive rocks distribute in watershed area in middle and west section of east Kunlun. Its lithological association are light gray white medium-coarse granodiorite—porphyritic granodiorite—diorite. The constant elements of early Triassic intermediate-acid intrusive rocks have the characteristics of aluminous granite and calcium alkaline series magmatic rocks; while geochemical characteristics of the trace elements show the characteristics of volcanic granites. The geochemical characteristics show the enrichment of rare earth elements, the loss of heavy rare earth elements, and obvious fractionation of light and heavy rare earth elements. As showed by petrology and geochemical characteristics, it is indicated that early Triassic intermediate-acid intrusive rocks may be the products of the subduction in volcanic arc environment in the study area.