西天山特克斯达坂一带晚古生代花岗岩类的地球化学特征及其构造意义

Geochemical characters and tectonic significance of Late Paleozoic granitoids from Tekesi Daban, Western Tianshan

依据地质学、岩石学和年代学特征,西天山特克斯达坂一带花岗岩类被解体为早石炭世库勒萨依序列和早二叠世其那尔萨依序列,其同位素年龄分别为347 Ma、291～292 Ma。通过对该花岗岩类地球化学特征的研究得出,库勒萨依序列A/CNK平均值为1,K2O/Na2O平均值为0.96,(Na2O+K2O)/Al2O3平均值为0.66,里特曼指数σ平均值为3.2,为准铝质钙碱性花岗岩;其那尔萨依序列A/CNK平均值为1.05,K2O/Na2O平均值为1.17,富钾,为过铝质碱性花岗岩。库勒萨依序列为形成于岛弧环境的钙碱性花岗岩,是古亚洲洋向北俯冲的产物;其那尔萨依序列为形成于后造山期松弛阶段的碱性花岗岩。

Granitoids of Tekesi Daban have been subdivided into two successions of the Kulesayi succession with age of 347Ma in the early Carboniferous period and the Qinaersayi succession with age of 291-292Ma in the early Permian period. By the research of geochemical features for the granitoids in this paper, some differences can be observed： the Kulesayi succession is characterized by A/ CNK=1, K2O/Na2O=0.96, （Na2O＋K2O）/Al2O3=0.66 and σ=3.2 on the average,whereas the Qinaersayi succession is characterized by A/CNK=1.05 and K2O/Na2O=1.17 on the average. The former is rich in Na2O, the latter is rich in K2O relatively. The Kulesayi succession is metaluminous rocks which is different of the latter （peraluminous granitoids）. The Kulesayi succession which belongs to the calc-alkalic rock type is formed in the island arc tectonic setting and the Qinaersayi succession which belongs to the alkalic rock type is formed in post-orogenic episode.