Abstract:

Jiajika is a superlarge lithium deposit in Sichuan Province. The two-mica granite in the southern Jiajika orefield is closely related to rare metal pegmatites in space, time and origin. In this study, geochemical and hydrogen-oxygen isotope analyses of the granite were carried out to understand the rare metal metallogenic process. The results show that the Jiajika two-mica granite is S-type with high SiO₂, high-K calc-alkaline and peraluminous. The total rare earth composition of the granite is very low. The magma source of the granite may have been partial melting of the Triassic Xikang Group sandy-mudstone, and the fluid source may have been a mixture of magmatic and metamorphic water. R cluster analysis of trace elements shows that Li, Rb, Ti, W and Mn are closely related to rare metal metallogeny. Changes in the rare element contents suggest that ore-forming efficiency in the north was higher than in the south. Therefore, future prospecting work should focus on the northern part of the granite. Results of geochemistry, hydrogen-oxygen isotopes and previous studies reveal immiscibility in the diapirism of granitic magma. Pegmatitic magma segregated from the granitic magma may have concentrated the rare metals, and eventually formed the pegmatitic rare metal deposit.

Key words: two-mica granite, geochemistry, hydrogen and oxygen isotopes, rare metal, pegmatite, Jiajika