东天山康古尔塔格蛇绿岩SHRIMP年龄、Nd-Sr同位素特征及构造意义  

SHRIMP dating and Nd-Sr isotopic Tracing of Kangguertage ophiolite in eastern Tianshan,Xinjiang.

作　　者：李文铅[1,2] 马华东[1,4] 王冉[3] 王核[1] 夏斌[3] 

机构地区：[1]中国科学院广州地球化学研究所成矿动力学重点实验室,广州510640 [2]有色金属矿产地质调查中心,北京100012 [3]中国科学院边缘海地质重点实验室,中国科学院广州地球化学研究所,广州510640 [4]中国科学院边缘海地质重点实验室中国科学院广州地球化学研究所,北京100039

出　　处：《岩石学报》2008年第4期773-780,共8页Acta Petrologica Sinica

基　　金：中国科学院创新重要方向性项目(kzcx2-yw-107-03);国家十一五科技支撑项目2006BAB07B01-04联合资助.

摘　　要：通过对东天山康古尔塔格蛇绿岩中的辉长岩的SHRIMP锆石U-Pb年龄测定,得出康古尔塔格蛇绿岩形成于晚寒武世-早奥陶世(494±10Ma)。Nd-Sr同位素研究表明,康古尔塔格蛇绿岩中辉长岩、辉绿岩、玄武岩、斜长花岗岩及角斑岩的ε_(Nd)(t)值变化于+5.7～+10.5之间,与现代大洋岛弧火山岩的ε_(Nd)(t)值一致;(^(87)Sr/^(86)Sr)_i值变化于0.703475～0.704923之间,与现代典型大洋中脊新鲜玄武岩的^(87)Sr/^(86)Sr值变化范围基本一致。上述特征显示出康古尔塔格蛇绿岩与准噶尔蛇绿岩一样,属SSZ型蛇绿岩,其岩浆来自亏损上地幔,且在演化过程中没有受到陆源物质的明显混染。该蛇绿岩形成时代、源区组成结合区域地质构造等暗示康古尔塔格断裂以北地区可能属于准噶尔板块范畴。The Kangguertage ophiolite in eastern Tianshan Mountain is located in the west to Tuwu-Yandong copper ore-belt and marks the Aibihu-Kangguertage suture zone between the Hasakestan plate in the north and Tarim plate in the south. The ophiolte contact in fault with Carbonic strata and form an east-west extension of tectonic slices distributed in bilateral Kangguertage major fault. SHRIMP zircon U-Pb dating for the gabbros from Kangguertage ophiolite yields an age of 494 ± 10Ma. Nd-Sr isotopic components of the gabbros, diabases, basahs, plagioclase granites and keratophyres show the variety of εNd （t） value from ＋ 5.7 to ＋ 10.5, which are consistent with the εNd （t） value of modern oceanic island-arc volcanic rocks. The （^87 Sr/^86 Sr）i values range from 0. 703475 to 0. 704923 and slightly higher than those of typical fresh modern mid-ocean ridge basahs. Thus, the Nd-Sr isotopic characteristics indicate that the Kangguertage ophiolite belongs to SSZ-typo and are similar to the ophiolites in Zhungeer area. In addition, the magma was probably derived from a depleted upper mantle reservoir and didn＇t suffer from the contamination of the continental material. The field geotectonics, formation age and Nd-Sr isotopic component suggest that the area north of the Kangguertage major fault probably belongs to the Zhungeer plate tectonically.

关 键 词：SSZ型蛇绿岩 SHRIMP测年 Nd—Sr同位素 康古尔塔格 东天山 

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