WANG Yu-fei1, WANG Zhi-lin1*, LU An-huai1, WU Lin2,3, XU De-ru4, WU Tao2,3, LONG Yong-zhen1, HUANG Zhi-long2, FAN Hong-peng2, PENG Er-ke1
(1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring (Central South University), Ministry of Education, School of Geosciences and Info-Physics, Central South University, Changsha 410083, China;
2. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550081, China;
3. University of Chinese Academy of Sciences, Beijing 100049, China;
4. State Key Laboratory of Nuclear Resources and Environment, East China University of Technology, Nanchang 330013, China)
Abstract: The karstic bauxites commonly host numerous associated critical metals such as lithium, gallium, vanadium, chromium, REE, scandium, cobalt, nickel, niobium, zirconium, and tungsten. The Maochang bauxite deposit in the central Guizhou is the largest concealed bauxite deposit in China, with a certain amount of associated critical metals of gallium, scandium, and lithium. However, associated critical metals in the pyrite have not been paid enough attention yet. In this paper, we have systematically carried out the study on the mineralogy of pyrites from various types of bauxite-bearing rocks in the Yangjiadong ore block of the Maochang deposit. The results show that those pyrites have complex textures and genesis. Two kinds of pyrites including the sedimentary one (PyⅠ) and hydrothermal one (PyⅡ) have been identified. The PyⅠ is characterized with framboid or fine-grained textures, whereas the PyⅡ occurred as veins/ veinlets or cements of breccias and can be subdivided into three generations of PyⅡ-1, PyⅡ-2 and PyⅡ-3. The rim of PyⅡ-1 grain was commonly replaced or overgrown by irregular PyⅡ-2, and these two generations of pyrites (PyⅡ-1 and PyⅡ-2) were cut by PyⅡ-3 veins or stockwork veins. The EPMA analyses show that the PyⅡ-2 has significantly higher Co (up to 9.31%) and As (up to 2.98%) contents than other generations of pyrites, and thus it is confirmed that the late hydrothermal activity could greatly contribute to the enrichment of cobalt in the PyⅡ-2. The obvious negative correlation between Co and Fe contents reflects that Co was mainly incorporated in lattice of pyrite in form of isomorphism The sharp contacts and distinct chemical compositions between PyⅡ-1 and PyⅡ-2 pyrites suggest that the Co-rich pyrite (PyⅡ-2) was mainly formed by the coupled dissolution and reprecipitation of the precursor PyⅡ-1. The discovery of Co-rich pyrite in the Maochang bauxite deposit has not only provided a new direction for the comprehensive recycling and utilization of Co in the pyrite of the Maochang mine, but also provided new direction for exploring associated critical metal types in bauxites in the central Guizhou.
Keywords: Maochang bauxite deposit; cobalt-rich pyrite; associated critical metals; central Guizhou
ACTA MINERALOGICA SINICA Vol. 41, No.4/5, 2021, page 460-474