Primary enrichment and epigenetic magmatic-hydrothermal reactivation caused a new type of stratiform Cu-Co deposits in the Jianglang Dome, Eastern Tibetan Plateau

Stratiform/stratabound Cu-Co deposits are commonly associated with the leaching of basinal brines and synorogenic metamorphic fluids. However, significant magmatichydrothermal examples hosted by fertile metasedimentary rocks are lacking. Here, we present integrated geochronological and isotopic data from stratiform Cu-Co deposits in the Jianglang Dome, which was intruded by ca. 164 Ma granitic plutons. Chalcopyrite separates yielded two Re-Os isochron ages of 562 Ma and 161.8 Ma, as well as contrasting initial 187Os/188Os ratios of 0.311 and 2.766. Extracted from cupriferous quartz vein, hydrothermal zircon rims produced a weighted mean 206Pb/238U age of 158.5 Ma, and epsilon Hf(t) values of between -6.3 and -22.3. Metamorphic monazites in twomica quartz schist defined a weighted mean 206Pb/238U age of 193.0 Ma, with epsilon Nd(t) values ranging from -14.1 to -14.7, and are attributed to ca. 204-190 Ma peak metamorphism in the Songpan-Ganze orogen. Also, sulfide minerals have positive delta 34SV-CDT values of 4.8%0-9.3%0, which are compatible with those of host rocks (3.1%0-13.0%0) and granitic plutons (7.3%0-9.6%0). All of these age and isotopic constraints confirm two-staged formation of ca. 550 Ma syngenetic enrichment overprinted by ca. 160 Ma epigenetic mineralization, with the latest Neoproterozoic rock units contributing significantly to ca. 164-158.5 Ma magmatic-hydrothermal mineralization, which shows no synorogenic or metamorphic affinities. Together, our findings indicate a superimposed genetic model, and a new type of granitic intrusion-related, metalliferous siliciclastic metasedimentary rock-hosted stratiform Cu-Co deposit. Furthermore, analogous domes, where leachable basement rocks and a fluid-driving magmatic-hydrothermal system are present, may prove to be novel targets for future exploration.