东昆仑造山带大水沟中酸性侵入岩的形成时代及岩石地球化学特征

对东昆仑造山带东段大水沟一带开展锆石U-Pb测年和岩石地球化学研究。获得英云闪长岩锆石U-Pb定年为(402±2) Ma,属早泥盆世华力西期。岩石地球化学特征显示: Al饱和指数A/CNK集中在0.946~1.077之间; 轻重稀土比值LREE/HREE在2.94~18.93范围,显示轻稀土富集; δEu在0.01~0.85之间,属于Eu亏损型; δCe在0.95~1.23之间,反映出无异常—轻微富集。岩体整体显示以I型花岗岩为主的特点,结合构造环境判别图解,综合判断大水沟一带中酸性侵入岩属东昆仑东段早泥盆世后碰撞造山花岗岩。

Formation age and petrological geochemical characteristics of intermediate-acid intrusive rocks in Dashuigou of East Kunlun organic belt

The authors investigated zircon U-Pb dating and petrological geochemical characteristics in the east of East Kunlun orogenic belt. The results show that the U-Pb age of zircons in tonalite is (402±2) Ma, belonging to Early Devonian of Variscan. The petrological geochemical characteristics show that the aluminium saturation A/CNK index ranges from 0.946 to 1.077, and the ratio of light rare earth elements and heavy rare earth elements (LREE/HREE) is from 2.94 to 18.93, which indicates the enrichment of light rare earth elements. And the δEu parameter is between 0.01 and 0.85, belonging to europium depletion type. The δCe parameter is between 0.95 and 1.23, reflecting normal-slightly enrichment. Overall, the rocks are mainly by I-type granite. Combined with the tectonic discrimination diagrams, the authors concluded that intermediate-acid intrusive rocks in Dashuigou are orogenic granite formed after Early Devonian.