中国首例铁氧化物铜金铀稀土型矿床的厘定及其成矿演化

Lala Fe-Oxide-Cu-Au-U-REE Ore Deposit, Sichuan China- An Example of Superimposed Mineralization

通过对拉拉矿床矿物共生组合、矿物生成顺序、矿石特征的研究,发现其矿石矿物以磁铁矿为主,铁和铜的硫化物次之,并含有大量稀土矿物和自然金。拉拉矿床至少经历了两期成矿作用:早期为区域变质成矿作用,晚期为热液成矿作用。早期形成Fe REE P矿化,晚期为Cu Mo Au Co (U)矿化。根据这些特征,首次指出该矿床属于铁氧化物 铜 金 铀 稀土型矿床,而不是以往所称的块状硫化物型铜矿。

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% RE2O3, 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. And the age of the metamorphic mineralization is 1200Ma of the whole rock RbSr dating of muscovite schist. 