西天山特克斯达坂地区库勒萨依斑岩地球化学特征及构造意义

Geochemical Character and Tectonic Significance of the Kulesayi Porphyry in Tekesi Daban,Western Tianshan

O型埃达克岩是洋壳板片俯）十消减的关键证据。库勒萨依斑岩体里特曼指数（δ）平均值为3．05，属于钙碱性系列岛弧浅成岩。w（SiO2）为57．06％～70．74％，具高w（Al2O3）、w（Na2O）、w（Sr）和相对富集LREE，低w（MgO）、w（Y）、w（Yb），强烈亏损HREE的特征。w（Na2O）／w（K2O）〉1，w（Sr）／w（Y）平均为50．95，d（Eu）正异常，属典型O型埃达克岩。岩石化学和元素地球化学图解均印证其形成于岛弧环境，是天山洋在俯冲过程中，俯冲到一定深度后发生部分熔融，上侵形成的O型埃达克岩，这一结论为西天山早石炭世末期的板块俯冲、大洋板片消减等演化提供了重要的佐证。

O-type adakite is the key evidence of oceanic plate subduction. Kulesayi porphyry series are calcalkaline hypabyssal rocks, with δ averaged at 3.05,SiO2 ranging from 57.06% to 70. 74%. They are rich in Al2O3, Na2O, Sr and LREE, poor in MgO, Y, Yb and HREE with Na2O/K2O more than 1 and an average Sr/Y of 50.95. These rocks also have positive Eu anomaly. All the characteristics are in agreement with those of typical O-type adakite rocks. Their diagrams of petrochemistry and element geochemistry indicate that these rocks are formed in island arc environment. They are the products of partial melting of subducted Tianshan oceanic crust during the early Carboniferous. This provides important evidence for the evolution of plate subduction of West Tianshan in the end of the Early Carboniferous. The recognition of adakite rocks in this area provides significant information to improve native metallogenic disciplinarian and a guide for future prospecting in western Tianshan.