Geochemical Characteristics And Resource-Environmental Assessment Of The Dexing Cu Mine Tailings In Jiangxi Province Of China

It has been acknowledge that numerous mine tailings are characterized by re-exploitation and environmental pollution. Dexing copper mine is the biggest copper mine in China, with the biggest tailing dam in Asia. The tailing samples were collected by drilling in 1# tailing dam in Dexing. The multi-element analytical scheme were applied , for example XRF, ICPES, ICPMS, AAS, AFS. The tailing size is deterimed by laser grain sizes analytical instrument, and the mineral form is deterined by X-ray powder diffractometry testing. Sequential extraction method is used for analysis of occurance of the elements in tailing. Based on heavy metal elements testing of surface water, stream sediment and soil around tailing dam, the characteristics of the spatial distribution of elements in tailing dam with the environmental impacts are discussed in this article. The conclusions obtained are listed as follows:（1）The major particles of the tailing are silty, with quartz and sericite as the main minerals, while the content of metal mineral is less than 1%. The distribution of elements is largely depended on the sorting process of minerals . Along the direction of the tailings discharge, the elements can be divided into 3 zone: （S、Cu、Fe、Mo、Ag、Cr）�'（SiO₂、Au、Hg）�'（Al₂O₃、Tl）.（2） During the supergene geochemical process, the sulfide was weathered to be oxided,which led the significant decrease of the pyrite content, with the loss of Ca and C in tailing. Meanwhile sericite changed into illite and. Because the enviroment of Dexing tailing dam is alkaline-deoxidation, and most of heavy metal elements are major in the form of sulphides, these indicate that the supergene geochemical process is not strong.（3） Cu and As in Dexing 1# tailing dam are harmful to enviroment to a certain extent. Heavy metal elements are occurred as water-soluble, adsorbed-exchangable and Fe-Mn oxide, and these forms of elements are active, which easily migrated into the surrounding environment. The proportions of active Cu, As, Pb and Cd are 15.8%, 36.2%, 23.3% and 29.3%, with total amounts of 5,258t, 126t, 58t and 1t , respectively, in tailing dam Moreover heavy metals have great potential harm in tailing dam, and the redox environment must been pay close attention to prevent the sudden release of heavy metal.（4）Cu content in tailing ranges from 0.06% to 0.19%, with an average of 0.11% . The Cu metal potential resource of the Dexing 1# tailing dam is estimated to be 33,429t. Content of Sericite ranges from 30.9% to 38%, with an average of 34.1% on average. There are about 10.23Mt Sericite can be recovered.（5） Surface water, stream sediment and soil around tailing dam are all polluted by heavy metals. Along the flow direction, heavy metals were transmited from tailing dam to envrionment, which was transferred by soild particles and enriched in stream sediments. The heavy metal pollution around the tailing dam is increased by time, and the heavy metal elements are more active in soil.