Geological Characteristics And Tectonic Attribute Of The Middle Proterozoic Metamorphic Rock Series In The Northern Margin Of The Qaidam Basin

Tectonic belt of northern margin of Qaidam Basin is one with a long evolutionaryhistory, subduction and collision of different continental blocks,which experiences differentlevels of structural deformation superimposed.This article select Paleoproterozoic which ineasternmost of northern margin of Qaidam Basin as research object, In order to theory of platetectonics and continental dynamics as the guiding ideology,Through the combination ofstructural geology,metamorphic petrology,structural analysis study, petrology andgeochemistryof research methods,conduct surveys and studies on metamorphic rocks whichexposed in easternmost of northern margin of Qaidam Basin,I make major progress andunderstanding of the following:1, through research and studies, to be presented to Dakendaban’s new division scheme: nowPaleoproterozoic is divided into three petrofabric, namely gneiss petrofabric（Pt₁D1_）, schistpetrofabric（Pt₁D₂）, marble petrofabric（Pt₁D₃）, Parts of Small temple group and Bayshingspecial gneiss rock mass of Mesoproterozoic was placed under Dakendaban group,the southside of Dakendaban group set aside Cambrian-Ordovician subsets under Tanjianshan group.2, through the cross-sectional studies, petrology and mineralogy comprehensive study dividedthe Paleoproterozoic Dakendaban group metamorphic facies, metamorphic belt,metamorphism and mineral assemblages in the study area can be divided into north and southtwo distinct metamorphic facies. South metamorphic gneisses with which mineral assemblageof biotite+sillimanite+K-feldspar+cordierite+garnet, sillimanite metamorphic belt is+K-feldspar zone; plagioclase amphibolite mineral assemblages symbiotic angle amphibole+tremolite+plagioclase+biotite, amphibole how color, metamorphic belt is amphibole-plagioclase zone, a high amphibolite facies. North gneiss symbiosis with mineral assemblagesgarnet+kyanite+biotite+muscovite+plagioclase, metamorphic belt of kyanite zone, is alow amphibolite facies: plagioclase amphibolite mineral assemblages as muscovite+biotite+sillimanite+plagioclase, metamorphic belt is sillimanite zone are amphibole-plagioclasebelt. Dakendaban important group of metamorphic minerals are garnet, biotite, muscovite,plagioclase, K-feldspar, hornblende, and quartz.3, through detailed field research and laboratory study, Paleoproterozoic metamorphic rocksof early replacement and overlay structure strong foliation developed a variety of constructionand a variety of small folds （BEDDING recumbent folds, closed with oblique folds androotless hook folds）; late developmental cleavage, cleavage folds and wrinkles lineation,medium-sized and other thick-relief folds. 4, through the Paleoproterozoic Dakendaban geochemical study group to restore the originalrock properties to determine the properties of the original rock structure and form in which theoriginal rock tectonic background. Dakendaban group gneiss original sedimentary rocks andargillaceous sandstone; leptynite main category protolith sandstone, some volcanic rocks;schists protolith subject to felsic volcanic rocks; plagioclase amphibolite category of primarymafic volcanic rocks. Dakendaban environmental groups should be formed continental crustextensional rift trough environment.