LA-ICP-MS Zircon U-Pb Dating of Permian Manganese Ores in Zunyi, Guizhou Province and Mineralization Age

Abstract

The Middle Permian manganese deposit in Zunyi, northern Guizhou is one of the major manganese mining areas in South China. However, the age of this manganese deposit has not been accurately constrained. Previous studies have generally concluded that the formation of Zunyi manganese ores was linked with the early activities of the Emeishan Large Igneous Province (ELIP). In this study, we investigated the lithology and mineralization age of the Mn-bearing rocks in the study area and explored the connections between ELIP and the genesis of these rocks. Zircon samples from the Mn-bearing tuff in the Tuanxi section of Zunyi were used for zircon U-Pb chronological analysis by LA-ICP-MS method. The results constrain the deposition age of Mn-bearing rocks in Member 3 of the Maokou Formation was older than 266 ± 3 Ma, this age was closely related to the early stage of ELIP, but it was 5–10 Ma earlier than the main eruption of the Emeishan basalt. Combined with the regional paleogeography, we believe that the mantle plume activities prior to the main eruption of ELIP provided the tectonic stress, manganese source, and mineralization environment for manganese ore formation in the rift basin of the study area.