GAO Zhi-wu1, SU Yan2*, LI Yu-hua3, DENG Ming-guo2, LIU Feng-xiang3, GENG Qi-wei2
(1. Zunyi Normal College, Zunyi 563006, China;
2. Kunming University of Science and Technology, Kunming 650093, China;
3. No.209 Geological Team of Yunnan Nuclear Industry, Kunming 650031, China)
Abstract: The Fangyangshan deposit, discovered firstly in recent years, is a Cu-rich characterized Cu-Pb-Zn polymetallic deposit in the Zhenkang ore-concentration area in the Western Yunnan. Two mineralization periods have been determined based on the detailed study of geological features of the deposit in this paper. They are the hydrothermal period of Fe-Zn mineralization and superimposed transformation period of Cu-Pb-Zn mineralization. The hydrothermal mineralization period can be furtherly divided to three phases including Phase I (quartz-dolomite-pyrite-arsenopyrite), Phase II (quartz-calcite-sphalerite-chlorite), and Phase Ⅲ (quartz-fluorite-pyrrhotite-chalcopyrite). The research on geochemical characteristics of rare earth elements of various metal sulfides and gangue minerals in each stage of the hydrothermal mineralization period and of the superimposed transformation period shows that the Phase Ⅰ pyrite, Phase Ⅱ sphalerite, Phase Ⅱ calcite, and Phase Ⅲ chalcopyrite all have the characteristic LREE-enriched "right-inclined" REE distribution patterns with obviously negative Eu anomalies. However, the calcite, sphalerite, and galena of the superimposed transformation epoch have "right-inclined" REE patterns with positive Eu anomalies. The above characteristics indicate that the environment of hydrothermal metallogenic period is reduced, while that of the superimposed transformation period is oxidized. The source of ore-forming materials for the two mineralization periods could be related to the stratum. The Y/Ho values of metal sulfides in the Fangyangshan Pb-Zn-Cu polymetallic deposit are relatively concentrated. The ranges of Y/Ho values for the Phase I pyrite (23.86－28.95), Phase II sphalerite (23.75－31.33), Phase III chalcopyrite (25.42－26.70) of the hydrothermal mineralization period, and galena (29.2－29.63) and sphalerite (23.75－31.33) of the superimposed transformation period are basically changed in the range of regional granite (24.58－29.63). The ranges of Y/Ho values for gangue mineral calcites of the hydrothermal metallogenic Phase II (32.76－40.06) and the superimposed transformation period (32.67－36.54) are similar to that of the eastern China continental crust (20－35). Therefore, it is believed that mineralization fluids of both the hydrothermal and the superimposed transformation mineralization periods could be mainly sourced from the similar deep magmatic hydrothermal fluids while the upper crustal fluid could be involved in the formation of calcite.
Keywords: the Fangyangshan deposit; mineral rare earth element; source of ore-forming fluids; mineralization environments; Baoshan block
ACTA MINERALOGICA SINICA Vol. 41, No.1, 2021, page 45-56