南阿尔金巴什瓦克石榴橄榄岩的变质演化  

Metamorphic evolution of the Bashiwake garnet peridotite from the South Altyn Tagh

作　　者：李云帅[1,2] 张建新[2] 李胜荣[1] 于胜尧[2] 宫江华[2] 林宜慧[2] 

机构地区：[1]中国地质大学,北京100083 [2]中国地质科学院地质研究所,大陆构造与动力学国家重点实验室,北京100037

出　　处：《岩石学报》2013年第6期2073-2092,共20页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41072151、41272110);公益性行业专项基金(201011034);中国地质调查局项目(1212011120157)联合资助

摘　　要：南阿尔金巴什瓦克地区石榴橄榄岩在空间上呈透镜体状与高压基性麻粒岩和含石榴子石长英质片麻岩伴生。基于矿物共生组合关系和变质反应结构特征,并结合矿物化学详细分析以及温压条件的估算,我们将该区石榴橄榄岩的变质演化划分为3个阶段:峰期变质阶段(M1)、峰后早期退变质阶段(M2)和晚期角闪岩相-绿片岩相退变质阶段(M3)。M1阶段的矿物组合为石榴子石(Grt)+橄榄石(Ol)+斜方辉石(Opx)+单斜辉石(Cpx),所估算的温压条件为:T=891～1054℃、P=17.2～24.7kbar;M2阶段以石榴子石周围出现斜方辉石(Opx)+单斜辉石(Cpx)+尖晶石(Spl)的次生边为特征,在P=10kbar时,估算的温度条件为:T=711～796℃;M3阶段以形成角闪石(Amp)+蛇纹石(Srp)+金云母(Phl)+绿泥石(Chl)+磁铁矿(Mag)±滑石(Tlc)为特征。石榴橄榄岩具有与相邻的长英质麻粒岩和基性麻粒岩类似的P-T演化历史。结合成因矿物学和初步的地球化学特征,我们认为石榴橄榄岩的原岩可能为侵位于大陆地壳的镁铁质-超镁铁质杂岩,并在早古生代与长英质地壳物质一起俯冲,经历高压(超高压?)/高温变质作用以及随后的变质和地球动力学演化。Garnet peridotite from the Bashiwake area in the South Altyn Taghoccurs as slices or lenseswithin HP mafic granulite and garnet-bearing felsic gneiss.0n the basis of textural relationships,mineralogical data and temperature and pressure estimates, three stages of the metamorphic evolution have been identified,including peak metamorphic stage （ M1） ,decompression retrograde stage （ M2） and late amphibolite-greenschist facies retrograde stage （ M3） . Stage I isdefined by the assemblage garnet ＋ olivine ＋ orthopyroxene ＋ clinopyroxene,which formed at 891～1054℃ and 17.2 ～24. 7kbar. Stage II is an initial decompression stage, characterized by the formation of kelyphitic rims of orthopyroxene ＋ clinopyroxene ＋ aluminous spinel around garnet,yielding 711～796℃ at 10kbar. Stage III is represented by the formation of amphibole ＋ serpentine ＋ phlogopite ＋ chlorite ＋ magnetite ± talc. The P-T evolution of garnet peridotite is similar to that of the associated high pressure felsic granulite and mafic granulite. Combining with mineralogical and geochemical characteristics,we speculated that the protolith of garnet peridotite was mantle-derived mafic-ultramafic complex emplaced in the crust,whichwas subducted together with felsic crust material in the Early Paleozoic,and they shared the subsequent metamorphic and geodynamic evolution.

关 键 词：石榴橄榄岩 变质演化 巴什瓦克 南阿尔金 

分 类 号：P578.942[天文地球—矿物学] P588.34[天文地球—地质学]