| There are huge amount of peridotites included by the basalts coming from the earth mantle in Damaping area located in Hebei where is famous for the mantle's rocks in China. The samples from the earth mantle afford us large amount of information about composition, feature and evolution courses of the new era mantle's rocks in the north China.Based on the survey on the spot and rock samples collection in Damaping, and depended on the scientific experiment like X-Ray fraction analysis, EPMA and microscope analysis, I make the systematic reaseach for the features of the rocks and minerals included in Damaping areas, and I found some special circle-structured minerals in the rocks.According to the analysis of the figures by the Mg# versus related oxides contained in the basalts, the basalt from there was thought as the a part of the melt rocks rising from the earth mantle. However, the peridotite includings of the area are the complex rock composed by the olivine, pyroxene and spinel mineral by the microscope analysis and the major mineral is the olivine.The olivine from the peridotite contain the high Mg# ,but the olivines crystalled in magma contain the low Mg#. The pyroxene is characterized by the high Cr# and the low Al by the EPMA, which imply that the peridotite in this area came from the transional mantle rock which had been experiencing highly-extent melting.The center part of the circle-structured olivine is characterized on the high MgO,which came from the peridotite.The edge of the circle-structured olivine is characterized on the high FeO, which is crystalled in the magma.The principle of the 3 layers'mineral is similar to the form of the circle-structured olivine. It was caused by fast chemical reaction between the minerals from the mantle rocks and the magma, and it explained the menthod of evolution courses of mantle rocks.The balanced temperature meatured by the two geothermometer is about 910℃~1027℃, the pressure range is about 1.25~2.46GPa,which is in deep by 80km.
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