西准噶尔恰达地区哈尔加乌组火山岩锆石U-Pb年代学、地球化学及地质意义

发布时间：2018-12-18 08:09

【摘要】：恰达地区的二叠系哈尔加乌组火山岩分布于唐巴勒蛇绿岩带东侧、准噶尔盆地西南缘,主要岩性为灰绿色-紫红色(气孔)(杏仁)玄武岩-玄武安山岩-安山岩。LA-ICP-MS锆石U-Pb年龄为(296.6±8.1)Ma,MSWD=7.7(93%置信度),时代属早二叠世。地球化学研究表明:该火山岩属亚碱性系列,全碱含量较高(w(Na2O+K2O)=3.95%~6.39%)且相对富钠。轻稀土(LREE)相对富集((La/Yb)N=3.49~14.66)且分馏较好((La/Sm)N值均大于1.00(1.68~3.51)),重稀土分馏较差((Gd/Yb)N=1.38~2.56)。仅部分样品有微弱的负铕异常(δEu=0.88~1.15)。微量元素具有大离子亲石元素(LILE)相对富集,高场强元素(HFSE)Nb、Ta相对亏损,Zr、Hf轻微富集的特征。综合火山岩的地球化学特征,结合相关构造判别图解及火山岩所处的区域地质背景,认为哈尔加乌组火山岩的形成背景以板内大陆环境为主,兼有部分弧火山岩的特征,形成于俯冲碰撞造山期后的区域伸展背景下,火山岩的岛弧特征是对碰撞前混染弧组分的继承。
[Abstract]:The volcanic rocks of the Permian Hargavu formation in the Chada area are distributed in the eastern side of the Tangbale ophiolite belt and in the southwest margin of Junggar Basin. The main lithology is greyish-purplish red (stomata) (almond) basalt-Black Tortoise andesite-andesite. The LA-ICP-MS zircon U-Pb age is (296.6 卤8.1) Ma,MSWD=7.7 (93% confidence), and the age belongs to early Permian. The geochemical study shows that the volcanic rocks belong to subalkaline series, and the total alkali content is relatively high (w (Na2O K _ 2O) = 3.95 ~ 6.39%) and the volcanic rocks are relatively rich in sodium. The light rare earth (LREE) is relatively enriched (La/Yb) 3.49 ~ 14.66) and the fractionation (La/Sm) N) is higher than 1.00 (1.68 ~ 3.51),). The heavy rare earth fractionation (Gd/Yb) is less than (Gd/Yb) 1.38 ~ (2. 56). Only some samples have weak negative europium anomaly (未 Eu=0.88~1.15). The trace elements are characterized by the relative enrichment of large ion lithophile element (LILE), the relative depletion of high field strength element (HFSE) Nb,Ta and the slight enrichment of Zr,Hf. Based on the geochemical characteristics of volcanic rocks and the related tectonic discriminant diagrams and the regional geological background of volcanic rocks, it is considered that the formation of volcanic rocks in the Haljiawu formation is dominated by the intraplate continental environment and has the characteristics of some arc volcanic rocks. Formed in the regional extensional setting after the subduction and collision orogenic period, the island arc characteristics of volcanic rocks are inherited from the pre-collision mixed arc composition.
【作者单位】：长安大学地球科学与资源学院;国土资源部岩浆作用成矿与找矿重点实验室;中国科学院广州地球化学研究所边缘海地质重点实验室;新疆维吾尔自治区有色地质矿产勘查院;
【基金】：国家自然科学基金项目(41273033) 新疆维吾尔自治区地质勘查基金项目(XJZBKD2008-04,XJQDZ2009-03)~~
【分类号】：P588.14;P597.3

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