LU Jia1,2, FANG Wei-xuan1,2,3*, WANG Tong-rong2, SUN Zi-jian2, GUO Yu-qian3, SONG Li-hong3
(1. Kunming University of Science and Technology, Kunming 650093, China; 2. Beijing Institute of Geology for Mineral Resources, Beijing 100012, China; 3. China Non-Ferrous Metals Resource Geological Survey, Beijing 100012, China)
Abstract: Iron lava, diabase, gabbro diabase, volcanic breccia and volcanic agglomerate together to form subvolcanic rock from Yinmin iron-copper area in Yunnan Province, China. Lithological zoning is obvious. Hydrothermal alteration is closely related to mineralization. Electron microprobe analyses of biotite and chlorite in various lithology of subvolcanic complex rock are conducted. Biotite is considered as the magnesia biotite; most of them are rebalanced biotite, its temperature is 505－590 ℃, lgf(O2)=-12.4－-5.25, p=116－226 MPa, h=4.27－8.37 km, instructed to high temperature and strong oxidizing environment. Chlorite is considered as pycnochlorite, prochlorite, sheridanite, and pennine, its temperature is 170－235 ℃, lgf(O2)=-12.4－-5.25, lgf(S2)=-13.34－-2.50, instructed to mid-low temperature and highly reduced environment. Mineral occurrence, mineral assemblages and geochemical characteristics show that two minerals are characterized by multi-sourced and multi-stage. Biotite alteration represents the main metallogenic period of iron ore; chlorite alteration represents the main metallogenic period of copper ore. Tectono-magmatic thermal events form the later high－low temperature alkaline and strong reducing fluid, the ore deposit has been clearly superimposed and transformed. These factors suggest that subvolcanic complex rock is feed system for metallogenic element in iron-copper deposit for a long period of time.
Keywords: mineral chemistry; biotite and chlorite; copper-iron deposit; subvolcanic complex rock; Yunnan Province
E-mail: fangweixuan@tom.com
ACTA MINERALOGICA SINICA Vol. 37, No. 5, 2017, Page 576-587
