Abstract:

Baerzhe alkaline granite is composed of No. 801 and No. 802 plutons, in which the 801 pluton is a superlarge rare earth and REE mineralized alkaline granitic intrusion and the 802 pluton is a non-mineralized pluton in which REE and some rare-elements are also slightly concentrated. A comparative study of major and trace elements and isotopic geochemistry of the mineralized 801 alkaline granite and the associated barren 802 alkaline granite in Baerzhe area was carried out, and the results show that both the mineralized and barren alkaline granites are characterized by enrichment of mantle isotopes, with no significant effect of assimilation. Geochemistry of major and trace elements suggests that the primary magma of the 802 pluton experienced a higher degree of evolution than the 801 pluton, which means that the 802 pluton has further potential for rare metal exploration. Petrographic zonation, pegmatite, miarolitic cavities and fluid-melt inclusions are well developed in the 801 pluton, suggesting that a full differentiation and evolution occurred after the intrusion of the primary magma. On the contrary, the 802 pluton is characterized by a porphyry texture of shallow intrusive rock and a relatively uniform major and trace element abundance, implying rapid cooling and non-differentiation after the emplacement of the primary magma of the 802 pluton. It is obvious that high differentiation and evolution that occurred in a relatively isolated system after the intrusion of the alkaline magma was the dominant factor for the rare-earth and REE mineralization of Baerzhe alkaline granites.

Key words: Baerzhe, alkaline granite, magmatic-hydrothermal evolution, superlarge REE-Nb-Be-Zr deposit, mineralized and barren