Constraints of Sphalerite Texture on Supernormal Ge Enrichment: A Case Study of the Zhulingou Ge-Zn Deposit, Guizhou Province, China

Germanium is one of the dominant and strategic critical metals in China, which is mainly found in Pb-Zn ores and coal deposits. In Pb-Zn ores, sphalerite is the main Ge carrier. Previous studies have shown that Ge in sphalerite is dominated by isomorphism. Although there are differences in the understanding of Ge substitution, it is generally accepted that Cu, Ag, Mn, Fe and other trace elements in sphalerite have obvious effects on Ge substitution and supernormal enrichment. The Zhulingou Ge-Zn deposit is a newly discovered medium-scale Zn (with a Zn metal reserve of more than 200, 000 tons and an average Zn grade of 6.5%) which hosts Ge metal reserve of more than 200 tons with an average Ge grade of 98×10−6). In this work, in-situ analysis of trace elements such as Ge in the main sulfides (sphalerite and pyrite) of the Zhulingou deposit was carried out. The results show that Ge mainly occurs in sphalerite (272×10−6 – 1915×10−6, mean 776×10−6), and the contents of Ge in pyrite are less than 10×10−6. However, the Ge contents in sphalerite with different mineral textures are quite different: the Ge contents of radial sphalerite (383×10−6 –1475×10−6, average 919×10−6) are higher than that of colloform zoning sphalerite (272×10−6 – 1915×10−6, mean 632×10−6). Furthermore, Fe concentrations in sphalerite with different textures are significantly different, showing that Fe contents of the radial sphalerite (858×10−6 – 15935×10−6, average 5220×10−6) are lower than those of the colloform zoning sphalerite (1201×10−6 – 30817×10−6, mean 9563×10−6), which was in contrast to the enrichment of Ge. In addition, the contents of Cu (mostly <3×10−6, maximum 52.1×10−6), Ag (<1×10−6), Mn (9.51×10−6 – 171×10−6, mean 86×10−6) are 2 – 3 orders of magnitude lower than that of Ge; except for the high Mn contents (396×10−6 – 3973×10−6, average 1173×10−6) in pyrite, the contents of Cu are less than 1×10−6, and the contents of Ag are mostly lower than the detection limit. The correlations among Ge and Mn, Fe in sphalerite with different textures are significantly different. The correlation coefficient between Ge and Fe in the radial sphalerite is high, while the correlation coefficient between Ge and Fe in the colloform zoning sphalerite is significantly low; similarly, in the radial sphalerite, the correlation degree between Ge and Mn is high, but the correlation degree between Ge and Mn in the colloform zoning sphalerite is obviously low. In addition, there is no obvious correlation between Ge and trace elements such as Cu and Ag in sphalerite with different mineral textures. Combined with the mapping analysis of Cu, Ag, Mn, and Fe, we propose that: (1) in sphalerite, trace metals such as Cu, Ag, Mn, Fe, and other trace elements may have no influence on Ge substitution and supernormal enrichment; (2) the use of correlation analysis to examine Ge substitution should be done with caution; (3) the supernormal enrichment of Ge is independent to its substitution; (4) the sphalerite mineral texture is the major controlling factor for the final Ge supernormal accumulation. This study provides a new perspective for understanding the mechanism of Ge supernormal enrichment in the Pb-Zn ores. © 2022 Science Press. All rights reserved.