Geological features of dark enclaves in REE-bearing granites in eastern Nanling: an example from the Pitou rock mass

On the basis of field geological survey and indoor integrated study, this study analyzed the geological features of dark enclaves from the REE-bearing granites in weathering crust infiltration deposits in eastern Nanling. A large amount of dark enclaves in the rock mass is found to occur in platy and linear structures, and consists of quartz, pyroxene and plagioclase with typical gabbro texture. The dark enclaves are low in Si, K and Na, and high in Ca, Al, Mg, Fe, Ti and Mn, belonging to sub-alkaline-aluminum unsaturated type; enriched in U, U, La, Pr, Nd, Sm, Dy and depleted in Nb, Sr, Zr, Hf, Ti. The total REE content of dark enclaves is lower than that of host bearing granite, with obvious negative Ce and Eu anomalies. All these characteristics suggest that the protolith may originate from the early mafic rocks related to differentiation and evolution of Pitou rock mass in early Yanshanian. Comparison with dark enclaves of granites in the Nanling area will help search for rare earth deposits and rare metal deposits.