新疆西准噶尔萨尔托海地区英安岩锆石U-Pb年龄及其对达拉布特蛇绿岩侵位时限的约束  

LA-ICP-MS U-Pb Zircon Age of Dacite in Tailegula Formation and Their Constraints on Emplacement of Darbut Ophiolite in West Junggar

作　　者：赵磊[1] 何国琦[2] ZHAO Lei HE Guoqi(Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037 The Key Laboratory of Orogenic Belts and Crustal Evolution （MOE）, School of Earth and Space Sciences, Peking University, Beijing 100871)

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]造山带与地壳演化教育部重点实验室,北京大学地球与空间科学学院,北京100871

出　　处：《北京大学学报（自然科学版）》2016年第5期871-880,共10页Acta Scientiarum Naturalium Universitatis Pekinensis

基　　金：国家自然科学基金(41202159);国家国际科技合作专项(2010DFB23390);中国地质调查局项目(12120115070301)资助

摘　　要：新疆西准噶尔达拉布特蛇绿岩在其北东段萨尔托海地区被下石炭统火山岩-沉积岩不整合覆盖。对这套沉积-火山岩系中的英安岩进行LA-ICP-MS锆石U-Pb定年,获得^(206)Pb/^(238)U加权平均年龄为349±2 Ma(早石炭世杜内期)。英安岩REE分配型式具有轻稀土富集、重稀土相对平坦、Eu负异常明显的特点。微量元素原始地幔标准化图解中,所有样品的标准化丰度都随着元素不相容性的增加而增大。与经典的弧英安岩以及埃达克火山岩相比,太勒古拉组英安岩Sr含量平均值为195μg/g,Sr/Y平均值为5.2,La/Yb平均值为4.6,远小于经典的弧英安岩和埃达克岩。结合太勒古拉组变形、变质微弱的特点,认为早石炭世英安岩形成于板内裂谷环境,且在早石炭世之前达拉布特蛇绿岩已经就位。The Darbut ophiolite in West Junggar is covered unconformably by sedimentary-volcanic series of Tailegula Formation in Sartohay region. LA-ICP-MS U-Pb dating on zircons from dacite gives the ^206pb/^238U weighted mean age of 349±2 Ma, indicating that the Tailegula Formation was formed in Tournaisian of Early Carboniferous. The dacites show right-oriented linear REE patterns with LREE enrichment and negative Eu anomaly. In trace element primitive mantle normalized diagram, the standardized abundance of all samples increase as rising of the element incompatibility. The average Sr, Sr/Y, and La/Yb of dacites in Tailegula Formation are 195 μg/g, 5.2 and 4.6, respectively, much less than those of classic arc dacites and adakites. Combined with low-grade deformation and metamorphism, the dacites in Tailegula Formation are suggested to erupt in rift environment.

关 键 词：西准噶尔 达拉布特蛇绿岩 太勒古拉组 英安岩 锆石U-PB年龄 裂谷 

分 类 号：P587[天文地球—岩石学] P597.3[天文地球—地质学]