The Study On Mineralogical Characteristics Of REE-Nb-Fe Ore Within Carbonatites-Alkaline Complexes Based On MLA

Bayan Obo REE-Nb-Fe ore deposit is closely related with carbonatites and alkline-rocks. Bayan Obo REE-Nb-Fe ore deposit is located in the north margin of the North China plate as well as adjacent to the Central Asian orogenic belt. Major ore body of Bayan Obo deposit exists in dolostone of H8, others exist in K-rich slate of H9, Na-rich rocks and carbonatite dykes. Ore bodies contain main ore body, east ore body, west ore body and Dongjielegele ore body and etc. Types of ores contain Magnetite-type REE ore, Silicate-type Nb-REE ore, Dolomite-type Nb-REE ore, and a small amount of carbonatite-dyke-type Nb-REE ore.On the basis of field investigation and combined with previous research data, this thesis takes three major types of primary REE-Nb-Fe ores-Magnetite-type REE ore, Silicate-type Nb-REE ore(including aegirine-type Nb-REE ore and arfvedsonites-type Nb-REE ore)and Dolomite-type Nb-REE ore of Bayan Obo deposit as research object. With the help of MLA(Mineral Liberation Analyser) and optical microscope, we make a research on ores’ mineralogical characteristics which focus on occurrence state of useful elements of primary ores.1. Magnetite-type REE ore. Ore minerals of this type of ore are iron minerals and REE minerals. Magnetite is the mainly iron mineral which is coarse-grained and rich in iron. REE mainly exsits in bastnaesites which is of low content and scattered in ore. Magnetite is the main object of overall utilization in magnetite-type REE ore.2. Silicate-type Nb-REE ore, including aegirine-type Nb-REE ore and arfvedsonites-type Nb-REE ore.Aegirine-type Nb-REE ore have complicated mineral species and its ore minerals are REE-minerals and Nb-minerals. REE-minerals contain monazite, bastnaesite and parasite, which are of high content and coarse-grained. Nb-minerals are fersmite and columbite, which are of low content and fine-grained. There are also some other valuable elements such as Sc and Th in his type of ore which can be comprehensively utilized.Arfvedsonite-type Nb-REE ore is rich in REE and its ore minerals are REE-minerals and Nb-minerals. REE mainly exsits in parasite and monazite as well as a small amount of REE exsits in apatites. Nb of ore mainly exsits in pyrochlorite, Sr-pyrochlorite, parisite and monazite. Parisite and monazite are of high content and coarse-grained as well as pyrochlorite and Sr-pyrochlorite are of low content and fine-grained.3. Dolomite-type REE ore. Ore minerals of this type of ore are REE minerals. Major of REE minerals is bastnaesite which is rich REE and a small amount of REE exsit in monazite. Bastnaesites are of high content and coarse-grained.Based on comprehensive analysis, this thesis the metallogenesis of Bayan Obo deposit into two stages. Early stage of syndepositional mineralization(~1325Ma) and late stage of metamorphic fluid superposition(~450Ma). The former is main mineralization stage and the latter is activation and recrystallization of minerals which improve processibility of ores.