Formation of secondary non-sulfide zinc ore in Cho Dien Pb-Zn deposits

Abstract

Non-sulfide zinc ore in the Cho Dien deposit has been exploited for a long time and remains the major exploited ore in Cho Dien. There are numerous studies of Cho Dien Pb-Zn ore, however, many of the studies have dedicated to description of mineralogical and chemical compositions. Built on the mineralogical studies and the content of Pb and Zn in groundwater determined by reflective microscope, SEM, EPMA and ICP-MS methods, the study explained the formation of secondary non-sulfide zine ore in the Cho Dien deposit. The upper part of ore bodies was weathered and completely oxidized. Difference in geochemical behavior of lead (Pb) and zine (Zn) in the oxidation process of Pb-Zn ore led to the formation of non-sulfide zinc ore in the Cho Dien deposit. Oxidation of primary Pb-Zn ore minerals such as sphalerite, pyrite and galena creates a low pH environment and transforms zinc from immobile (sphalerite - ZnS) to mobile (Zn2+)and is retained in solution under low(acidic) pH conditions; whereas lead has the tendency to form soluble minerals (anglesite, cerussite). The acid neutralization of the surrounding rockcauseszinc to precipitate to form secondary non-sulfide zinc minerals.