Environmental geochemistry of the waste rock dump in the Taojiang manganese deposit, Hunan, China

Major element, rare-earth element (REE), trace element and heavy metal geochemical analyses were performed on the waste rock dump of the Taojiang manganese deposit. Field observations and analysis indicate that the main materials of the waste rock dump are the host rock Middle Ordovician black shale and primary carbonate manganese ore. The waste rocks contain heavy metals such as Cu, Pb, Zn, Cr, Tl, Sb and U. They are subaerially exposed to weathering and disintegration, resulting in leaching and removal of Sc, V, Cr, U, Cd, Th and other heavy metallic elements. These elements show the features of migration to different degrees and, among these, V, Cd and U show the strongest mobility. Additionally, it is evident that Ni, Cu, Zn, Pb, Tl and Sb in black shale are also leached. These heavy metallic elements, such as Cd and Tl, have very strong toxicity. When they enter the mining area and are accumulated continuously, they can exert serious influence on the environment. So great attention should be paid to the waste rock dumps as the pollution sources of heavy metals distributed in the area.