西准噶尔克拉玛依蛇绿混杂岩中的石榴角闪岩  

Garnet amphibolite found in Keramay ophiolitic mélange,western Junggar NW China

作　　者：陈博[1] 朱永峰[1] 魏少妮[1] 徐新[2] 

机构地区：[1]北京大学地球与空间科学学院,造山带与地壳演化教育部重点实验室,北京100871 [2]新疆自然资源与生态环境研究中心,乌鲁木齐830000

出　　处：《岩石学报》2008年第5期1034-1040,共7页Acta Petrologica Sinica

基　　金：国家科技支撑计划重点项目资助(编号:2006BAB07B08)

摘　　要：本文报道在准噶尔地区发现的石榴角闪岩,该岩石产在克拉玛依蛇绿混杂岩带的百口泉地区。石榴角闪岩主要由钙质角闪石、富钠斜长石和黝帘石组成,含少量钛铁矿、绿帘石、绿泥石、榍石、石榴石、普通辉石、金红石、磷灰石、钠长石、石英和锆石。石榴石中常包裹磷灰石、金红石、钛铁矿、石英和锆石。黝帘石+富钠斜长石组合中出现少量钙铝榴石残余。百口泉石榴角闪岩中石榴石的化学组成特征以及其中出现的金红石—钛铁矿—磷灰石—石英—锆石包体组合说明,该岩石不是异剥钙榴岩退变质的产物,而是榴辉岩退变的产物(辅助证据包括二辉橄榄岩中发育的辉石出溶结构和辉石塑性变形特征)。百口泉石榴角闪岩至少记录了四个阶段:石榴石—单斜辉石—金红石—磷灰石—石英—锆石组成的阶段Ⅰ(可能为榴辉岩相),普通辉石—钛铁矿—磷灰石—角闪石组成的退变阶段Ⅱ,角闪石—斜长石—榍石—钛铁矿构成的阶段Ⅲ(角闪岩相),以及绿帘石—石英—绿泥石构成的绿片岩相变质阶段Ⅳ。尽管上述演化历史存在一些不确定性,石榴角闪岩的发现为深入研究西准噶尔地区古生代洋壳俯冲带的性质及其演化过程提供了新的物质基础。Here we report the discovery of garnet amphibolite in the Keramay ophiolitic melange, western Junggar （north Xinjiang, NW China ）. The discovered garnet amphibolite, coexisting with amphibolite and greenschist, mainly consists of Tschermakite- magnesio-homblende and the assemblage of zoisite ＋ Na-rich plagioclase with minor amounts of garnet, clinopyroxene, rutile, apatite, ilmenite, titanite, epidote, chlorite, quartz and zircon. Garnet usually contains abundant apatite, futile, ilmenite, quartz and zircon inclusions. Studies on the peridotite from Baijiantan ophiolite melange have demonstrated that the mantle rocks came from depths of 〉 90km （Zhu and Xu, 2007 ）. Both the Baikouquan and Baijiantan regions belong to the Keramay ophiolite melange and they are located closely （Ca. 20km）. Present petrographic observations demonstrate that the mineral assemblage formed in eclogite phase is garnet clinopyroxene （omphacite？）-rutile-apatite-quartz-zircon. Zoisite-Na-rich-plagioclase-clinopyroxene-ilmenite formed during retrograde metamorphism stage, followed by the formation of Tschermakite-magnesiohornblende epidote titanite in amphibolite facies. The last stage of the retrograde metamorphism was recorded by the epidote-chlorite-quartz in greensehist facies.

关 键 词：蛇绿岩 石榴角闪岩 克拉玛依 西准噶尔 新疆 

分 类 号：P588.1[天文地球—岩石学] P588.3[天文地球—地质学]