Occurrence Characteristics And Origin Analysis Of Corundum From Fuping, Hebei Province

Natural corundum formed in alumina-rich, silica-poor geochemical background, representing the formation environment of high temperature, and it has great implications for understanding origin of corundum. Corundums which reach to gem grade could be used as ruby and sapphire. Both of them belong to five most precious gemstones, including diamond, emerald and cat’s eye. As a kind of precious gemstone, it has great economic value. However, the data of Fuping corundum is relatively scarce, the previous research of this area is not deep, the understanding of corundum’s origin is still confused. Therefore, it is necessary to carry out research for the occurrence characteristics and origin of corundum from Fuping. This kind of research has implications for prospecting and mining of corundum deposits.The lithologies of corundum-bearing rocks observed in Fuping area are mainly granitic migmatites and sillimanite migmatites. Corundum-bearing rocks are mainly composed of dark matrix and light-colored veins. The dark matrix is granular blastic texture and gneissic structure(radial structure). In the light-colored veins, corundum and feldspar are coarse grained granite texture and block structure. The significant feature of corundum-bearing rocks is augen structure and feldspar content is very high, which almost surrounded the entire corundum crystal.According to the characteristics of petrography and geochemistry, corundum deposits in Fuping area belong to the origin of anatectic migmatite. The formation of corundum deposits mainly experienced regional metamorphism, migmatization and retrograde metamorphism three stages, and the formation of corundums are mainly in the first two stages. Corundums(generation I) formed in regional metamorphism are too small to reach the gem corundum size. The stage of migmatization formed corundum(generation II)-bearing light veins. This stage of corundums are large and could reach the standard of gem grade particle size. Corundum formation mechanism of this area is discussed in this paper. It is considered that gneisses formed aluminum-rich magma and crystallized in the process of migmatization. However, in different area, the composition difference of aluminum-rich magma is the main reason for the difference of mineral assemblages. In Taohua and Wangjiazhuang Village, the temperature of corundum deposits formed at the range of 600~730 ℃and the pressure ranged from 0.3 to 1.0 Gpa. The temperature of corundum deposit in Mailing area formed at the range of 484~700℃,and the pressure ranged from 0.1 to 0.8 Gpa.. All of them are high amphibolites facies-granulite facies.By the study of gemological characteristics and quality evaluation, corundums in Fuping area have the potential for gem exploitation. However, how to difine the market price of corundum needs the further research and discussion.