摘要
左权变质杂岩位于华北克拉通中部造山带的中南段,赞皇变质杂岩西南。两杂岩区出露的早元古代——晚太古代变质岩石类型主要有:长英质片麻岩、黑云斜长片麻岩、斜长角闪岩、石榴角闪岩、云母片岩和长石石英岩等。通过详细地野外地质调查、岩相学以及地球化学研究发现,左权变质杂岩与赞皇变质杂岩有类似的地球化学性质,其中,长英质片麻岩、黑云斜长片麻岩和角闪岩的原岩均有正、有副,按原岩性质可分为变质沉积岩、变质花岗质岩石和变质基性岩三类。变质沉积岩的原岩为粘土岩或杂砂岩,物源以上地壳的长英质成分为主,REE配分型式与PAAS以及上地壳平均成分类似,原岩在形成过程中经历了中——低等程度的风化作用,沉积背景为有演化岛弧发育的活动大陆边缘;变质花岗质岩石的原岩为中酸性侵入岩,形成于大陆边缘弧环境,与变质沉积岩呈侵入接触关系;变质基性岩的原岩是拉斑——钙碱玄武质岩石,其稀土总量较低、轻稀土轻微富集,地壳混染作用明显,总体形成环境类似于现代大陆边缘的岛弧构造环境。基于以上地球化学特征推测左权——赞皇变质杂岩形成于典型碰撞造山环境,卷入了华北克拉通东部陆块和西部陆块之间的俯冲——碰撞过程。
The Zuoquan metamorphic complex is located at the central-southern segment of the nearly NS-striking Trans-North China Orogen, in the southwest of the Zanhuang metamorphic complex. Felsic gneiss, biotite-plagioclase gneiss, amphibolite, mica schist and quartzite are the main and important types of metamorphic rocks in Paleoproterozoic-Late Archean. These metamorphic rocks were carefully studied through field investigations, petrographical and geochemical research. It was found that the geochemical characteristics of the rocks exposed both in the Zuoquan and Zanhuang areas were similar. Three types of protoliths of felsic gneiss, biotite-plagioclase gneiss and amphibolite were recognized： meta-sedimentary rocks, meta-granitic rocks and meta-basites. The meta-sedimentary rocks were originally sedimentary mudstones or graywackes coming mainly from upper crustal felsic rocks. REE distribution patterns of the rocks are similar to those of the PAAS and averaged upper-crustal compositions. Provenance of the mudstones or graywackes was weakly to moderately weathered and possibly formed in an active continental margin with the beginning of an island arc. The protoliths of meta-granitic rocks intrusive contact with meta-sedimentary rocks were intermediate-acidity intrusive rocks, and formed in a continental marginal arc environment. Protoliths of meta-basites were possibly calc-alkaline and tholeiitic rocks with lower ΣREE, weakly enrichment of LREE and visible crustal contamination characteristics. These rocks were formed in volcanic arcs within continental margin comparable to the present-day continental margin. It was inferred that the Zuoquan metamorphic complex and the Zanhuang metamorphic complex were involved in the subduction-collision process of the Eastern Block and the Western Block to form the coherent basement of the North China Craton along the Trans-North China Orogen.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2013年第2期533-550,共18页
Acta Petrologica Sinica
基金
科技部973项目(2012CB416603)
国家自然科学基金项目(41102120
40725007)
中国地质调查局地质调查工作项目(1212011120150)
中国地质科学院地质研究所基本科研业务费专项资金(J1117)联合资助
关键词
地球化学
构造判别
赞皇
左权
中部带
华北克拉通
Geochemistry
Tectonic discrimination
Zanhuang
Zuoquan
Trans-North China Orogen
North China Craton
