新疆东天山白石泉铜镍矿床基性-超基性岩体锆石U-Pb同位素年龄、地球化学特征及其对古亚洲洋闭合时限的制约  

Zircon U-Pb age and the geochemistry of the Baishiquan mafic-ultramafic complex in the Eastern Tianshan,Xinjiang province:constraints on the closure of the Paleo-Asian Ocean.

作　　者：毛启贵[1] 肖文交[1] 韩春明[1] 孙敏[2] 袁超[3] 闫臻[1] 李继亮[1] 雍拥[1] 张继恩[1] 

机构地区：[1]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室 [2]香港大学地球科学系 [3]中国科学院广州地球化学研究所,广州510640

出　　处：《岩石学报》2006年第1期153-162,共10页Acta Petrologica Sinica

基　　金：国家重点基础研究发展规划项目(2001CB409801);国家自然科学基金项目(40172080);香港研究基金项目(HKU7840/04P)联合资助.

摘　　要：白石泉铜镍硫化物矿床位于中天山北缘,阿齐库都克-沙泉子断裂带南侧,产于同源侵入基性-超基性复式岩体中。采用锆石激光剥蚀法(LA-ICP-MS)获得矿化辉长岩中锆石U-Pb年龄为281．2±0．9Ma。辉长岩和橄榄岩的地球化学数据表明白石泉含矿杂岩体具高Mg特征。岩石富集大离子亲石元素(Rb、Ba、K、Sr)、LREE和高场强元素(U、Pb),而具有Ce负异常和亏损高场强元素(Th、Nb、Ta、Zr、Hf)的特征。这些表明白石泉含矿杂岩体具有幔源特征和岛弧岩浆特征。结合对白石泉岩体地质特征和区域地质背景的综合分析,本文推断白石泉岩体形成于岛弧环境或活动陆缘环境,即早二叠世期间在东天山地区还存在俯冲作用,因而古亚洲洋至少应在早二叠世晚期或以后才闭合。The Baishiquan Cu-Ni sulfide deposit is located in the northern part of the Center Tianshan Massif, south of the Aqikuduke-Shaquanzi fault of the Eastern Tianshan Mountains. Ore-body was formed by the magmas and lay within the mafic-ultramafic complex. Zircons from the mineralized gabbro of the orefield yield a crystallization age of 281.2 ± 0.9Ma. These gabbro and peridotites of the Baishiquan mafic-ultramafic complex have high Mg content. With enriched LILE （Rb,Ba,K,Sr）, LREE and HFSE （U.Pb）, these rocks have negative Ce anomalies and depleted HIFE （Th. Nb, Ta.Ti ）. These data indicate that the Baishiquan complex has the characters of mange-derived and arc island magmas. Combined with analyses of the geological and tectonic characters of the Baishiquan complex, we conclude that the Baishiquan complex was formed in an island setting or active margin. This indicates that a subduction event was reasonable in the Eastern Tianshan Mountains in the Early Permian, thus the Paleo-Asian Ocean did not close until the later Early Permian.

关 键 词：白石泉 铜镍矿床 基性-超基性岩体 锆石定年 早二叠世岛弧 中天山 

分 类 号：P597.3[天文地球—地球化学] P588.125[天文地球—地质学]