Cassiterite U-Pb dating of the lower Cretaceous Yanbei tin porphyry district in the Mikengshan volcanic basin, SE China

The Yanbei tin porphyry district with a total resource of about 250,000 t Sn is hosted in the Lower Cretaceous Mikengshan volcanic basin in the southeastern part of the Nanling Range. There are several tin deposits of greisen, stockwork and vein styles associated to the intrusive center of the 8 x 8 km large Mikengshan volcanoplutonic complex. LA-ICP-MS U-Pb dating of cassiterite yielded ages of 130.4 +/- 4.0 Ma, 132.0 +/- 1.5 Ma and 133.5 +/- 1.7 Ma for the Yanbei deposit, 135.9 +/- 1.5 Ma and 136.7 +/- 1.4 Ma for the Taoxiba deposit, and 135.1 +/- 4.0 Ma for the Kuangbei deposit. These data overlap within error and indicate that the three deposits belong to a same tin mineral system. Combined with the previous geochronological data, we propose a scenario for the porphyry tin mineral system in the Mikengshan basin. Dacitic to rhyolitic volcanic and subvolcanic rocks formed at ca. 140 Ma, and were shallowly intruded by highly evolved magmas which released magmatic-hydrothermal fluids to form veinlet-disseminated and greisen ore in the granitic rocks, and more distal stockwork and vein tin mineralization in the volcanic and subvolcanic envelope. The porphyry tin deposits in the Mikengshan volcanic basin are part of the 145-135 Ma tin metallogenic event in South China. The Early Cretaceous volcanic basins in the eastern part of the Nanling Range are promising targets for tin exploration.