新疆柯坪地区上泥盆统克孜尔塔格组砂岩物源分析及其大地构造意义

Provenance and Tectonic Significance of the Sandstone in Devonian Keziertage Formation in Keping,Xinjiang

对柯坪地区克孜尔塔格组岩石地球化学特征的分析表明,其稳定元素(Al_2O_3,Fe_2O_3,MnO)明显多于不稳定元素(MgO,K_2O,Na_2O),显示岩石经过了较远的搬运。轻稀土元素相对富集,重稀土元素亏损,具明显的Eu异常。主量、微量元素综合分析表明,其构造背景为被动大陆边缘,其物源主要来自成熟的大陆石英质物源区,少量来自花岗岩源区。碎屑锆石的U-Pb年龄明显存在4个区间:550~400,1 050~750,1 800~1 550,2 550~2 400 Ma,反映了塔里木地区的4次构造热事件。基于地球化学特征及碎屑锆石测年结果的分析表明,克孜尔塔格组主要物源区为塔北隆起的前寒武纪基底和早古生代岩浆岩。

The analyses of lithogeochemical characteristics of the sandstone in Keziertage Formation at Keping,Xinjiang show that the stable elements（Al2O3 ,Fe2O3 ,MnO） are more than the unstable elements （MgO,K2O,Na2O）. This illustrates that the sandstone must have gone through a distant transportation. There are more light rare earth elements than heavy rare earth elements, and Eu is obviously anomal. The comprehensive geochemical analyses suggest that the tectonic setting is apassive continental margin. The main provenance region is the mellow quartzi^erous provenance, with a few from the granite area. The zir- con U-Pb dating indicates that the rock ages are grouped in 550--400 Ma,1 050-750 Ma,1 800-1 550 Ma and 2 550-2 400 Ma, which are responses of four tectonothermal events in Tarim area. According to re- suits of geochemical characteristics and zircon U-Pb ages, the main provenance region is Precambrian base- ment and Early Palaeozoic Era igneous rock in the north Tarim uplift.