摘要
利用LA-ICPMS和LA-MC-ICPMS技术,对卡鲁安-阿祖拜伟晶岩田中4条伟晶岩脉以及哈龙岩体中锆石U-Pb定年、铪同位素组成进行了研究。研究显示,卡鲁安矿区805、806、807号脉的形成时代分别为(216.0±2.6)Ma、(223.7±1.8)Ma和(221±15)Ma,属三叠纪岩浆活动的产物。对于库卡拉盖650号脉,锆石U-Pb定年结果显示,它由形成时代为(227.9±2.6)Ma的早期钠长石伟晶岩与形成时代为(211.3±2.4)Ma的晚期锂辉石-钠长石-锂云母伟晶岩2期伟晶岩构成。哈龙岩体形成时代为400.9~403.3 Ma,由于伟晶岩与哈龙岩体之间存在形成时代上的差异(170 Ma以上),预示着它们之间不具成因上的联系。卡鲁安矿区伟晶岩脉中锆石显示较小的正εHf(t)值(+0.65^+2.50)和较大的模式年龄TDM2(1090~1213 Ma),相似于可可托海3号脉、柯鲁木特112号脉中锆石的铪同位素组成,指示伟晶岩由陆-陆碰撞体制伸展背景下的加厚地壳物质减压熔融所形成。
Zircon U-Pb dating and Hf isotopes of four pegmaites from the Kaluan-Azubai pegmatite mining area were carried out by LA-ICPMS and LA-MC-ICPMS in this paper. The formation ages of pegmatites, numbered 805, 806 and 807 in the Kaluan mining area, were determined to be （216.0±2.6） Ma, （223.7±1.8） Ma and （221±15） Ma, respectively, i.e. products of Triassic magmatic activities. For the Kukalagai No.650 pegmatite, zircon U-Pb dating shows that it made up of two stages of pegmatites, that is, the early albite pegmatite （227.9±2.6） Ma and the late spodumene-albite-lepidolite pegmatite （211.3±2.4） Ma. The intrusive age of Halong granite is in the range of 400.9–403.3 Ma, as the products of Devonian magmatic activities. As large gaps in their formation age （〉170 Ma） between pegmatites and Halong granites, it indicates that pegmatites from the Kaluan mining area have no genetic relationship with the Halong granite. Zircons from the pegmatites of Kaluan mining area have lower positiveεHf（t） values （＋0.65– ＋2.50）, with TDM2 model ages of 1090–1213 Ma, similar to zircon Hf isotopes of the Keketuohai No.3 pegmatite and the Kelumute No.112 pegmatite, indicating that the pegmatites were created by crust＆amp;nbsp;thickening and decompression melting in a post-collision tectonic setting.
出处
《地球化学》
CAS
CSCD
北大核心
2015年第1期9-26,共18页
Geochimica
基金
国家自然科学基金(41372104)
新疆有色金属工业(集团)有限责任公司科研项目(2011YSKY-02)
中国科学院地球化学研究所矿床地球化学国家重点实验室开放课题资助基金(2008012)
