Recurrent granite-related mineralization along former Tethys sutures in southwestern China

Abstract

The sutures of the Paleo-Tethys, Meso-Tethys, and Neo-Tethys oceans in southwestern China host many major porphyry- and/or granite-related mineral deposits. We compile age and geochemical data from these deposits. The age data show that most of these deposits are not related to the formation of the sutures, but to their later tectonic reactivation. For instance, intrusion-related deposits along fault zones in the Sanjiang area, which represent the suture of the former Paleo-Tethys Ocean, fall in one of the four age groups: 239–206 Ma, 182–162 Ma, 126–70 Ma, and 53–32 Ma. The oldest group of major porphyry- and/or granite-related deposits in the Sanjiang zone is related to the subduction and closure of the Paleo-Tethys Ocean, whereas younger deposits formed during the reactivation of Paleo-Tethys sutures during the closure of the Meso-Tethys and the Neo-Tethys oceans and during the India–Asia collision. Different types of coeval porphyry- and/or granite-related deposits occur along different segments of the same crustal-scale structure and are related to different types of intrusions: Cu (Mo), CuAu, Au, and Mo (Cu) porphyry or skarn deposits are associated with relatively oxidized rocks that were derived from the melting of subduction-modified mantle with variable contributions from the crust and WMo and SnW deposits are related to highly evolved, reduced porphyries and/or granites that originated from partial melting of metasedimentary rocks. Although the inventory of sedimentary source rocks along the sutures is controlled by the geological development before the suture formed, the later reactivation of the suture determines which source rocks become available for melting and, thus, which type of mineralization may form along different reactivated segments.