| 其他摘要 | Geology and geochemistry studies were carried out on several typical veined copper deposits in Lanping-Simao basin, Yunnan, China. The ores fabric, mineral association and its zoned law and mineral sequence of crystallization were recognized by detailed observation both in field and in microscope and SEM. The composition of tetrahedrites was analysed to understand its distribution of tetrahedrites was analysed to understand its distribution characteristics in time and space, which showed that tennantites [Cu_(12) (As>0.5, Sb<0.5)_4S_(13)] are dominant as compared with tetrahedrites [Cu_(12)(As<0.5, Sb>0.5)_4S_(13)] and the transit of tennantites to tetrhedrites exists in this area from the south to north of the basin as well as from the lower to upper to deposits, both the tetrahedrite of higher Sb and Ag content and lower Sb and Ag content might crystallized earlier. Studies of association, REE and inclusion of the vein minerals indicated that the ore-forming fluid was characterized oxidation, neutral to weakly alkaline, moderate to high salinity and moderate to low temperature. Combining with the evidences of trace elements, REE and H, O, Pb, Sr, S, C isotopes of the deposits, this paper further revealed that water in ore-forming fluid might mainly derive from metometric water and ore-forming metal (Cu, Ag, Pb, Zn, As, Sb, Fe, REE), organic carbon (C) and mineralizer (CO_2, CH_4, H_2S etal.) might mainly derive from the deep. The dissolution experiment of tetrahedrites indicated that temperature (T) and PH of solution are two main controlled factors for Cu, Zn, Fe, As, Sb to transport and precipitate together, and these elements are mainly carried by carbonate complex under condition of low temperature, on which a precipitated model for tetrahedrite was present. The immersing experiment of rocks showed that volcanic rock (basalt) might provided some ore-forming materials in Jinman area. Based on the studies above and comparison with marine sedex deposits a genetic view of terrestrial sedex was presented and a new type of copper deposit was defined. Two important and possibly general new knowledge have also been acquired through this work: 1) The hypabyssal veined deposits underground may be the main existing form of terrestrial sede. 2) The harsh terms (especially temperature and PH) necessary for Cu, Zn, Fe, As, Sb to transport together is the main cause for tetrahedrite often slightly present in hydrothermal deposits. |
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