塔里木北缘Rodinia超大陆聚合事件——来自新元古代早期花岗岩成因的证据

Rodinia Supercontinent Convergence Event in the Northern Margin of Tarim:Evidence from the Genesis of Early Neoproterozoic Granites

对塔里木板块拼入Rodinia超大陆聚合时限进行限定,报道塔里木板块北缘库鲁克塔格隆起奥依库如克岩体花岗闪长岩的年代学、岩石学、地球化学和锆石Hf同位素特征。花岗闪长岩的LA-ICP-MS锆石U-Pb年龄为(855±29)Ma,为新元古代早期岩浆作用产物。全岩化学组成上,该岩石为准铝质-弱过铝质、钙碱性系列"I"型花岗岩,轻重稀土元素分馏显著,基本无Eu异常,富集Rb,Ba,K,Sr等大离子亲石元素,亏损P,Ti,Nb,Ta等高场强元素。锆石Hf同位素分析结果显示:锆石εHf(t)值为-15.12^-11.52;二阶段模式年龄TDM2=2.46~2.66 Ga。研究表明,奥依库如克岩体形成于板块俯冲消减环境,指示Rodinia超大陆的汇聚。

In order to define the time limit for transcontinental polymerization of the Tarim plate into Rodinia,this paper reports the geochronology,petrology,geochemistry and Hf isotopic characteristics of the granodiorite of the oykuluke massif in the Kuruktag uplift on the northern margin of the Tarim plate.The LA-ICP-MS zircon U-Pb age of granodiorite is 855±29 Ma,which is the product of early Neoproterozoic magmatism.In terms of the chemical composition of the whole rock,the rock is quasi aluminous weak peraluminous,calc alkaline series I-type granite,with significant fractionation of light and light rare earth elements,basically no Eu anomaly,enrichment of Rb,Ba,K,Sr and other large ion lithophile elements,and loss of P,Ti,NB,Ta and other high field strength elements.The results of Hf isotopic analysis of zircon show that theεHf(t)value of zircon is-15.12 to-11.52,and the two-stage model age(TDM2)is 2.46 to 2.66 Ga.This study shows that the oykuruke massif should be formed in the subduction environment of the plate,indicating the convergence of Rodinia supercontinent.