REE Abundance and REE Minerals in Granitic Rocks in the Nanling Range, Jiangxi Province, Southern China, and Generation of the REE-rich Weathered Crust Deposits

Studies of Mesozoic granites associated with rare earth element (REE)-rich weathered crust deposits in southernmost Jiangxi Province indicate that they have high-K to shoshonite compositions and belong to ilmenite-series I-type granites. Of the studied rocks at 59-292 ppm of bulk REE content, the highest are seen in the biotite granites of Dingnan (358, 429 ppm) and mafic biotite granite of the Wuliting Granite (344 ppm) near the Dajishan tungsten mine, both areas where weathered-crust REE deposits occur. REE-bearing accessory minerals in these granites are mainly zircon, apatite and allanite, and REE-fluorocarbonates are common. REE enrichment occurs in the rims of apatite crystals, and in fluorocarbonates that occur along grain boundaries of and cracks in major silicate minerals, and in fluorocarbonates that replaced altered biotite. It is therefore thought that a major part of the REE content of these granites was concentrated during deuteric activity, rather than during magmatic crystallization. The crack-filling REE-fluorocarbonates could subsequently have been easily leached out and deposited in weathered crust developed during a long period of exposure.