柴达木盆地北缘早古生代高压—超高压变质带中发现典型超高压矿物——柯石英  

Discovery of Coesite in the North Qaidam Early Paleozoic Ultrahigh-high Pressure (UHP-HP) Metamorphic Belt, NW China

作　　者：杨经绥[1] 宋述光 许志琴[1] 吴才来[1] 史仁灯[1] 张建新[1] 李海兵[1] 万渝生[1] 刘焰[1] 邱海峻 刘福来[1] Shigenori Maruyama 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]东京工业大学地球行星系

出　　处：《地质学报》2001年第2期175-179,共5页Acta Geologica Sinica

基　　金：国家基金重点(编号49732070);国家重点基础研究发展规划(G1998040800);国家地质调查项目(DKD2001003);原地质矿产部"九万"重大某础项目(编号9501106)资助成果

摘　　要：从都兰北带榴辉岩的片麻岩围岩的锆石中发现了柯石英包裹体和石墨包裹体,说明该超高压带的峰期变质作用已达柯石英稳定区间(>2.8GPa)但小于金刚石的稳定区间(<3.5GPa),从而确定了柴达木盆地北缘存在早古生代超高压变质作用和陆-陆碰撞作用,为中国中部存在一条横贯东西的早古生代(大致500～400Ma)高压超高压变质带的推断提供了新的关键性证据。Coesite was discovered as inclusions in zircon separates from gneiss associated with a large eclogite body in the North Belt of the Qaidam UHP terrane. Some graphite inclusions also found. This finding confirms our previous suggestion that the North Qaidam UHP terrane was recrystallized at p below the diamond stability field based on several lines of evidence such as polycrystalline K-feldspar and quartz inclusions in eclogitic garnet, quartz lamellae in omphacite and p-t estimates for both eclogite and garnet peridotite. The occurrence of coesite inclusions in zircon suggests in-situ UHP metamorphism. This UHP terrane, along with the Altun e-clogite of 504 Ma, and those to the east of Qilian Mts, in the North Qingling, Tongbai and North Dabie regions, recorded the Early Paleozoic collision between the Sino-Korean and Yangtze plates. This UHP belt could extend to further west to the similar age Kokchetav UHP belt in Kazakastan.

关 键 词：超高压变质带 柯石英 柴达木盆地 榴辉岩 早古生代 包裹体 

分 类 号：P544.4[天文地球—构造地质学]