A review of the intracontinental porphyry deposits in the Middle-Lower Yangtze River Valley metallogenic belt, Eastern China

Abstract

The Middle-Lower Yangtze River Valley Metallogenic Belt (MLYB) is one of the most important metallogenic belts in eastern China, and contains many important porphyry deposits. These deposits include the Tongshankou Cu-Mo, Jiguanzui Cu-Au, Chengmengshan Cu-Mo, Wushan Cu-Mo, Fengshandong Cu-Au, Dingjiashan Cu, Yangjishan Au, Shaxi Cu-Au, Dongguashan Cu-Au, Shujiadian Cu and Anjishan Cu deposits, etc. In this review, we summarize the geological characteristics (including the stratigraphy, structure, ore-bearing porphyry types, vein characteristics and wall rock alteration), metallogenic ages and petro-geochemistry of representative porphyry deposits in the MLYB. We conclude that porphyritic magmatism and metallogeny have occurred in three stages. The Early (ca. 149–135 Ma) and Late (ca. 123–105 Ma) stages comprise mainly porphyry-skarn mineralization, whereas the Middle (ca. 133–125 Ma) stage comprises porphyry mineralization. Ore-bearing porphyries in the MLYB are the high-K calc-alkaline to calc-alkaline series, with the majority possess adakitic geochemical signature. The ore-bearing porphyries with adakitic signature may have originated from magma mixing, produced by the delamination of enriched lithospheric mantle and partial melting of the thickened lower crust. The enriched mantle-derived mafic melts component are very important for generating fertile magma, and the δ34S and δ18O values suggest that ore-forming materials were magma-derived. Compared with porphyry deposits in typical magmatic arc settings, porphyry deposits in the MLYB do not contain advanced argillic lithocaps or high- to intermediate-sulfidation systems, and the magmatic- and ore-forming material sources are also very different.