Lala Fe-Oxide-Cu-Au-U-REE ore deposit, Sichuan China - An example of superimposed mineralization

Lala Fe-Oxide-Cu-Au-U-REE deposit, classified as a massive sulifide deposit before, is located in Sichuan province, China. Lala district is situated near the western margin of Ynagtze block. The deposit is hosted in a Proterozoic unit, named Hekou Group, which is composed of metavolcanic and metasedimentary rocks. The metavolcanics consist of spilite, keratophyre, keratophyre volcaniclastic rock, with subsidiary co-genetic intrusive rocks. The metasedimentary rocks are comprised of magnetic quartzite, mica schist and marble. The LaLa deposit appears to have the form of a large lens. The ore bodies strike west northwest and dip at approximately 30° to south. The LaLa deposit contains a resource of about 200 Mt, including 0.9% Cu, 0.026% Mo, 0.02% Co, 0.25% RE2O3, 0.49ppm Au, 1.89ppm Ag. The deposit is mainly comprised of magnetite, chacopyrite, pyrite, minor bornit, molybdenite, apatite-bearing REE, cobaltite, pyrrhotite, and trace native gold, native silver, chalcocite, with rare telluride. Gangue minerals include albite, carbonate, biotite, quartz, fluorite, hongbland, sericite, almandine, and K-feldspar, with minor chlorite and tourmaline. According to the texture of the minerals, it is suggested that some of them were formed in regional metamorphism but the others formed in hydrothermal process. The hydrothermal mineralization has been determinated by Re-Os molybdenite. Four samples give the model ages: 1001 ± 1Ma, 1005 ± 1Ma, 928 ± 1Ma, and 983 ± 1Ma, respectively. These data demonstrate that the hydrothermal mineralization occurred at ∼ 1000Ma. The age of the metamorphic mineralization is 1200Ma using whole rock Rb-Sr dating of muscovite schist.