REE GEOCHEMICAL CHARACTERISTICS OF EPITHERMAL VEIN FLUORITE DEPOSITS IN SOUTH CHINA
Cao Junchen (Guangzhou Institute of Geochemistry, The Chinese Academy of Sciences. Guangzhou 510640)
Most fluorite deposits from Guangdong, Fujian and Jiangxi Provinces of South China occur in the endo-or exdo-contact zone of granite intrusions. The major mechanism of mineralization is vein filling (metasomatism), strictly controlled by NEstriking structures. The REE content in fluorite ranges from 100 × 10_(-6) to 200 ×10_(-6), and increases with increasing REE content of the country rock and the increasing green degree of fluorite, but decreases with the increasing intensity of alteration of the country rock and mineralization from early to late. The REE distribution pattern of fluorite inclines toward the right, which is similar to those of the biotite granite and the biotite from the granite. Fluorite is projected into near the MREE or HREE end, and the country rock near the LREE end on the REE ternary diagram. On the Moller's 'Tb/Ca-Tb/La diagram, fluorite from the granite falls into the hydrothermal field, whereas fluorite. from terrigenous carbonate rocks (in the contact zone of marine volcanic-sedimentary rocks and sedimentary carbonates)and sedimentary carbonates are projected below the field of fluorite of granite, even into the sedimentary field. Fluorite in the volcanic rocks are above the granite field. Apparently, this kind of epithermal deposit is only related to the lithology of the country rocks on the Moller's diagram. It is concluded that the epithermal vein-type fluorite deposits in South China formed after granitism. The ore-forming solution is the heated meteoric water, which constantly leached F, Ca and REE out of the country rock. By this way, the ore elements are reactivated, transported, and finally deposited in favorable sites.