Characteristic Of The Metamorphic Rock And The Metamorphic Function Of Precambrian, In Alatanaobao Region, Western Of Inner Mongolia

Alatanaobao region is located the western section of northern edge of North China Platform. On the study of the data of firldwork, adopting "structure - strata" and "structure-rock" new theories, new technique, new method of etc., the author studied the characteristic of metamorphic rock of Precambrian in Alatanaobao region, which included the characteristic of macroscopic geology, the type of rock, the texture and structure of rocks, paragenetic association of mineral, rock chemistry, micro element, rare earth element geochemistry and characteristic of primary rock, the metamorphic facies, the metamorphic type, and temperature-pressure condition, the mechanism of the metamorphism.In this area the Early Precambrian basement rock is consitituted of New Archean metamorphic sedimentary rocks, metamorphic igneous rocks and metamorphic basite dike that were undergone the medium-pressure regional dynamo-thermal metamorphism of high greenschist facies ～ low hornblende hornfels facies in New Archean. The characteristic of metamorphic mineral and the paragenetic association of metamorphic mineral show that the regional metamorphism corresponds to Alm zone, St zone, And-Cord zone of Baluo zone in metamorphic argillaceous rocks, and Pl-Hb zone in metabasite formation. The thermodynamics condition is P=2～6.5×10~8 Pa, T=556～628℃. Regional low temperature-dynamometamorphism, which is belonged to low greenschist facies and equal to Bi zone, Ab-Act zone, taked place in Middle Proterozoic. The thermodynamics condition is P=2～7×10~8Pa, T=350～500℃.