tectonic metamorphism
1.Based on the detailed studies of the basic problems such as the tectonic Framework,tectonic deformation,tectonic metamorphism,the chronology of magmatic,activity,dynamo-thermal,the attribution of the tectonic region,the author recovers the process of tectonic evolution of the Altai geosynclinal orogenic belt.
2.The third stage ( M3:170-180Ma) is characterized by the formation of tectonic breccia and mylonites in response to the brittle and ductile-brittle deformation related to the uplift. The matrix of the tectonites containing chlorite, actinolite and calcite indicates the greenschist facies of metamorphism.
3.Based on the volcanic and sedimentary formation, metamorphism and migmatization, geochemistry, magmatism, structural stratigraphy and isotope age determination the primary event of Early Precambrian is divided into three tectonic stages, which consist of three volcano-sedimentary cycles and six orogenies.
4.And the authors also yielded the metamorphism age of 2518±5 Ma in Caiyu body and 2508±5 Ma in Dashan body, similar to that obtained in other igneous in the complex, so the age may represent a very important metamorphic-tectonic event in the Late Archaean in this area.
5.On that basis,combined with the differences in rock association,metamorphism and deformation,depositional setting,and isotope age data,the original Qiergustao(Tengger)Formation is further disintegrated into the Upper Devonian Tengger Formation(senso stricto),Upper Carboniferous Qiergustao Formation(senso stricto)and Houxia Formation and Lower Permian Aerbasayi Formation,and their ranges of distribution are mapped and the tectonic framework of the area is redefined.
6.The recent progress, new discoveries, new data of the regional geological survey during the 8th 5-year plan in Shaanxi, are disscussed in this paper, which include the classification of precambrian metamorphism rocks and rock group, stratigraphic establishment of Phanero zoic eon, paleontology and new data of isotopic age determination, intrusive rock lineage unit establishment, metamorphic plutonic mass and tectonic of orgenic belt, new methods of regional survey and inforrnation application.
