南阿尔金地区榴辉岩特征及意义  

Characteristics and tectonic implications of eclogites in southern Altun area

作　　者：刘永顺[1] 于海峰[1] 修群业[1] 杨俊泉[1] 李铨[1] 

机构地区：[1]中国地质调查局天津地质矿产研究所,天津300170

出　　处：《岩石矿物学杂志》2010年第2期166-174,共9页Acta Petrologica et Mineralogica

基　　金：中国地质调查局基础地质综合研究项目(200113900070);国家自然科学基金重点资助项目(40032010-C)

摘　　要：野外地质调查工作表明,阿尔金地区西起且末河到茫崖长达300km范围内的"阿尔金山岩群"中多处出露榴辉岩透镜体。榴辉岩在产状和岩石学特征上可以分为两种:第1种是中细粒结构,块状构造,退化变质较弱,围岩多与片麻状花岗岩或花岗闪长岩关系密切;第2种是细粒结构,片麻状构造,具有透入性片麻理,有明显退化变质现象,围岩多与大理岩、黑云变粒岩、石英片岩等关系密切。在分布上,榴辉岩限于古元古代"阿尔金山岩群"中,含有榴辉岩的阿尔金构造杂岩带是柴达木盆地北缘碰撞杂岩带的西延部分。Field geological survey shows that there are many eclogite lenses outcropped in the Altun Mountains Rock Group which extends for 300 km from the Qiemo River in the west to Mangya in Altun area. Eclogite can be divided into two types according to its modes of occurrence and petrologic characteristics. One is characterized by medium-fine grained texture,massive structure,no gneissosity,weak retrogressive metamorphism,and a close relation to gneissic granite or granodiorite mineral assembly of the early period is garnet ＋ omphacite ＋ quartz,and that of the late period is amphibole （or pyroxene） ＋ plagioclase ＋ quartz omphacite has remarkably different Al2O3 and FeO content,while its CaO,MgO and Na2O content is relatively stable：Al2O3 is generally 5.55%～9.50%,FeO 4.33%～7.53%,and NaO 3.05%～5.54% jadeite content is 15.39～27.49% with an average of 22.22% the end member compositions of pyroxene are between those of kyanite eclogite and gneiss eclogite Chemical composition of garnet varies a lot with ∑FeO 18.82%～30.58%,MgO 2.38%～13.67%,and CaO 4.65%～10.26%,while SiO2 and Al2O3 change insignificantly,being 35.63%～39.57% and 20.92%～23.65% respectively the average end member composition of eclogite （mostly being Mg-and Ca-rich almandine） is assigned to C type eclogite in Coleman＇s classification diagram （1965）. The other is characterized by fine-grained texture,gneissic structure,penetrative geissosity,and obvious retrogressive metamorphism,with its wall rocks mostly related to marble,biotite granulite,quartz schist etc a majority of this type of eclogite has been changed into garnet amphibolites with obvious retrogressive metamorphism the eclogite is confined to Palaeoproterozoic Altun Mountains Rock Group and is comparable to the eclogite on the nortern margin of Qaidam Basin in the aspect of either wall rock characteristics or eclogite property,suggesting similar geneses moreover,granitic gneisses as the wall rocks of eclogite have basically the same diagenetic ages[（930±42�

关 键 词：南阿尔金地区 榴辉岩 特征 

分 类 号：P588.3[天文地球—岩石学]