Genetic relationship between the Emeishan plume and the bauxite deposits in Western Guangxi, China: Constraints from U–Pb and Lu–Hf isotopes of the detrital zircons in bauxite ores

Abstract

The formation processes and alumina sources of the large and super-large bauxite deposits that have developed in West Guangxi in the Yangtze Block have been debated for a long time. SHRIMP zircon U–Pb dates, combined with in situ Hf isotopic data of the detrital zircons from Permian bauxite ores in the Western Guangxi province, China, provide new constraints on the genesis of the bauxites in West Guangxi. U–Pb dating ages of the detrital zircons cluster around 256 Ma and 261 Ma; this is consistent with the emplacement age of the Emeishan plume. Thus, it has been determined that the detrital zircons come from magmatic rocks related to the Emeishan plume and that the Emeishan plume has significant control on the formation of bauxites. In addition, this work presents new evidence for the evolution of the Emeishan plume. Most of the ε Hf(T) values of the zircons around 256 Ma and 261 Ma are negative, varying widely from −1.3 to −16.1. This data indicates the melting of Yangtze Block basement rocks and the mixing of magmas generated both from the mantle and from the crust occurred at the periphery of the plume in the main phase of Emeishan LIP magmatism. This study verified that the plume-induced uplift exposed carbonates, as well as the mafic and felsic rocks generated by the Emeishan plume to long periods of intense weathering under humid tropical conditions. The weathering remnants of the high-alumina magmatic rocks and carbonates were deposited on, or transported to, the paleokarst surface and converted to bauxites.