祁连西段龚岔口地区榴闪岩的高压变质作用及其地质意义  

HIGH-PRESSURE METAMORPHISM OF GRANET-BEARING AMPHIBOLITE IN THEGONGCHAKOU REGION, WESTERN QILIAN MORNTAINS AND ITS GEOLOGICAL IMPLICATION

作　　者：苏建平[1] 胡能高[2] 付国民[2] 

机构地区：[1]甘肃省地质调查院 [2]长安大学,陕西西安710054

出　　处：《矿物学报》2004年第4期391-397,共7页Acta Mineralogica Sinica

基　　金：国家自然科学基金重大项目(90102003);祁连西段1:250000区域遥感调查项目(DK0002019)

摘　　要：在中祁连中新元古代的被动陆缘与野马南山构造单元结合部位的构造混杂岩带中发现了榴闪岩,对榴闪岩的岩石组合及其主要矿物进行了研究,认为该变质带是在约381～404℃和0.88～1.60GPa的低温高压变质条件下形成,结合区域地质背景资料分析,认为龚岔口低温高压变质带的产出构造环境可能是在祁连加里东期洋盆封闭过程中,中祁连陆块与火山弧碰撞,陆块前缘被俯冲下插带到很深的环境中,形成榴闪岩之后,在俯冲带后退的后续构造伸展和隆起过程中上升折返至浅处形成。该高压变质带的发现对于深入研究祁连造山带的构造演化具有重要的意义。In the tectonic hybrid rock belt located at the conjuncture of the middle Qilian Middle and Neo-Proterozoic passive margin and the Yemanabshan tectonic unit, a granet-amphibolite enclave was found for the first time. A detailed study has been conducted to investigate its outcropping characteristics, rock assemblage, lithology, mineralogy, geological background and microprobe analyses indicated that the metamorphic belt was formed at the temperature of 381-40　4℃ and pressure of 0.88-1.60 GPa, belonging　to high-pressure and low-temperature metamorphic rocks. By combining the regionally　geological setting, it is suggested　that the forming environment　may be related to the subduction and collision of microplate and island arc in the period of Caledonian. So the discovery　of the high-pressure metamorphic　belt is of great　tectonic significance　for lucubrating the Qilian orogen.

关 键 词：高压变质带 地质意义 构造混杂岩带 加里东期 中新元古代 俯冲 被动陆缘 GP 发现 封闭 

分 类 号：P588[天文地球—岩石学] P542[天文地球—地质学]