Vietnam Journal of Earth Sciences, 40(2), 208-219, Doi:
208
(VAST)
Vietnam Academy of Science and Technology
Vietnam Journal of Earth Sciences
http://www.vjs.ac.vn/index.php/jse
Formation of secondary nonsulfide
zinc ore in Cho Dien
Pb - Zn deposits
Nguyen Thi Lien, Nguyen Van Pho
Institute of Geological Sciences, (VAST), 84 Chua Lang, Dong Da, Hanoi, Vietnam
Received 13
November
2017; Received in revised form 28March 2018; Accepted 30May2018
ABSTRACT
In
Viet Nam, non-sulfide zinc ore in the Cho Dien deposit has been exploited for a long time. Up to the
present, zinc ore remains the major exploited ore in Cho Dien. There are numerous studies of Pb-Zn ore in Cho
Dien. However, most of the studies have dedicated only to description of mineralogical and chemical composi-
tion of Pb-Zn ore. There has been no publication on this non-sulfide zinc ore. Based on the mineralogical stu-
dies, 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 zinc ore in the Cho Dien deposit. Strong
weathering process makes the upper part of ore bodies completely oxidized. Difference in geochemical beha-
vior of lead (Pb) and zinc (Zn) in the oxidation process of Pb-Zn ore is the reason to form non-sulfide zinc ore
in the Cho Dien deposit. Oxidation of primary Pb-Zn ore is mainly sphalerite, pyrite, galena minerals which
creates a low pH environment and transforms of zinc from immobile (sphalerite - ZnS) to mobile (Zn
2+
) and
retained in solution under acid pH conditions whereas lead has the tendency to form soluble minerals (angle-
site, cerussite). The acid neutralization actions of the surrounding rocks make zinc precipitate, to form second-
ary non-sulfide zinc minerals.
Keywords: Non-sulfide zinc ore; Cho DienPb-Zn ore; secondary zinc ore.
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