内蒙大青山地区早前寒武纪高级变质岩系特征和变质动力学  

A STUDY ON CHARACTERISTICS OF EARLY PRECAMBRIAN HIGH-GRADE METAMORPHIC ROCK SERIES AND THEIR METAMOPHIC DYNAMICS

作　　者：金巍[1] 李树勋[1] 刘喜山[1] 

机构地区：[1]长春地质学院地质系,长春130061

出　　处：《岩石学报》1991年第4期27-36,共10页Acta Petrologica Sinica

基　　金：国家自然科学基金4870148

摘　　要：本文根据岩石组合、原岩建造、构造、岩浆事件,以及同位素年龄等资料的分析,认为内蒙大青山地区高级变质岩系由太古代和早元古代两个变质岩系组成。通过变质矿物组合的转变,讨论了它们的变质作用演化过程,太古代麻粒岩相变质与区域热流异常增高有关,早元古代高级变质起因于造山作用。它们是两次构造性质明显不同的麻粒岩事件。General speaking, high-grade metamorphic rock series in Daqingshan area belongs to Archaean metamorphic cycle. Recent study has discovered that the rock series consists of two parts, which are of distinct lithological characters, plutonic rock series, tectonic style and isotopic ages. These two kinds of rock series must separately belong to Archaean and Early Proterozoic eras. The Archaean high-grade metamorphic rock series is composed of layered granulite, amphibolite-plagioclase gneiss, garnetiferous quartzite (or banded iron formation), which is identical to a volcanic-sedimentary formation. Its petrochemical and geochemical features are similar to Archaean deposits. Tectonic deformation caused the layered rock series to form a series of fold and ductile shear zones. The structural trend is N-S. Plutonic rock series consists of hypersthene-bearing quartz-diorite and plagioclase granite (enderbite or charnockite), which is identical to Archaean high-Al type tonalite-trondhjemite series. Main minerals are hypersthene, diopside, sillimanite, garnet. peak metamorphic P-T is about 760～870℃, 0.95～1.09GPa. Another tonalite-trondhjemite megmatic event in late Archaean (2441～2470Ma) had set the time for high-grade metamorphic rock series. Early Proterozoic high-grade metamorphic rock series represents graphite-bearing gneiss, Al-rich gneiss, marbles and less granulites, as well as syntectonic potassium-rich granite.Lower metamorphic rocks belong to sedimentary clasolite-carbonate formation in intracontinental basin. This rock series is strongly deformed to form a series of recumbent or complex folds, ductile shear zone,and exhibits distinct E-W lineation, which is cross-cut to the Archaean rock association and structural trend.Major metamorphic minerals are cordierite, sillimanite, kyanite, garnet, hypersthene, diopside, hornblende and K-feldspar. Peak metamorphic P-T value is about 650～880℃, and 0.8～0.35GPa. The isotopic data indicate the time of metamorphism must be early Protero

关 键 词：麻粒岩 变质 动力学 太古代 元古代 

分 类 号：P588.346[天文地球—岩石学]