High arsenic coals related to sedimentary rock-hosted gold deposition in southwestern Guizhou Province, People`s Republic of China

Abstract

The rural population of southwestern Guizhou Province, China uses locally derived coal for domestic heating, cooking, and drying of various food stuffs by un-vented stoves. Coal became the dominant fuel source after deforestation earlier this century. Approximately 40 years ago, symptoms of arsenic poisoning, in some cases extreme, appeared in isolated, rural populations. More than 3,000 cases of arsenosis have been documented, whereas the affected population exceeds 10,000. Chemical analyses show that selected coals are extremely enriched in As and contain high concentrations of other trace elements deleterious to health. Southwestern Guizhou Province is underlain by an extensive thickness of Upper Paleozoic and Lower Mesozoic sedimentary rocks. The Permian, although aerially much less extensive, contains coal-bearing argillaceous sedimentary rocks of the Longtan Formation. The predominantly rural population in this mountainous region obtains most of their coal from many, very small mines operated locally. Southwestern Guizhou Province is also the site of extensive, mostly small-scale, gold mining from discontinuous sedimentary rock-hosted, Carlin-type gold deposits. Gold is currently being mined from areas that contact high-arsenic coals. The structural complexity of the area as well as the gold-As- rich coal association suggests that coal zones containing high As are probably as irregular andmore » discontinuous as the gold deposits. The local public health officials have instituted a program of testing the coal being mined for its high As concentration. A collaborative study between the US Geological Survey and the Key Laboratory of Environmental Geochemistry in Guiyang, Chinese Academy of Science is investigating the origin, occurrence, and distribution of arsenic in these coals. The goal is to be able to understand the petrogenesis in order to be able to predict and delineate arsenic-rich coals or zones.« less