Petrological Charateristics And Geological Implications Of Archean Granulite In Northwest Heibei Province

Granulites are the important component of the crust and there are high-pressured granulites generated in many areas of phanerozoic erogenic belts on the earth. The high-pressured granulites are formed both in the convergent area such as the subduction zones and collision zones and in the spreading area such as the bottom of the island arcs. Studies on the metamorphism and PTt path of the granulites now become to be one of the most important methods to module a structural evolvement pattern of erogenic belts.Studies on the metamorphic history of the granulites on a very old platform provide us some important information of the properties, status and forming processes of the lower crust and forming mechanism of the early continent crust. Studies on the granulite facies belts in the north area of the north-China Platform are always strongly concerned by geologists.The high pressured granulite belts in the Xuanhua area of Hebei Province are very worthy of being studied. So there have been many studies conducted by us further on the base of the previous works of other people. The chemical components of the main minerals such as the garnet, clinopyroxene, orthopyroxene and plagioclase were analysed; the temperatures and pressures of the mineral of different generations are computed with appropriate thermometers and barometers. Lots of information suggest that the metamorphism process of this area are from granulite facies to amphibolite facies and the retrograded metamorphic path is basically a CW nearly isothermal decompressional evolvement trend. There are some different P-T conditions between the west and east of the southern area to the Chongli-Chicheng large fracture. The temperature experienced in the east area is higher than that of the west area; and the condition of the pressure is reversed.