| 多宝山铜矿同位素地质特征 |
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| 引用本文：.1984.Isotope Geology Copper Of The Duobaoshan Ore Field[J].Mineral Deposits,3(1):47~57 |
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| Isotope Geology Copper Of The Duobaoshan Ore Field |
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| Abstract:The Duobaoahan copper ore field shows a regular time and spatial distribution in sulfur isotope compositions of sulfide-related especially intimately to mineralization and alceracion. The δS34 values are 0.07 in the hanging wall. -1.10 in the ore body and 0.55 in the foot wall. Vertically the 8ss4 values vary from high to low and then to high again with the depth, having the lowest value at the depth of 300m. Laterally theδS34 values of sulfides are lower than -1.0 in the ore body and higher than -1.0 on both sides of the ore body. Surrounding a center where the ore body has largest thickness, theδS34 contours show a variation halo which models the high grade copper ore body in shape and attitude. The spatial distribution pattern of sulfur isotope composition suggests that the center ofδS34 halo, which is bounded by exploration lines 66 and 74 or located from 100 to 450 m depth, seems likely to have been the center of mineralization activity. From the gradients of sulfur isotope variation, the ore-forming fluids are supposed to have come from the granodiorite porphyry and migrated toward exploration line 90. Spatially, in the direction of quartz core→potassium alteration zone→sericitization zone→propylitization zone, theδS34 values of sulfides also vary from high to low, and then to high again; in time, from the early stage to the late stage of mineralization, theδS34 values of fluids increased gradually. The precipitation temperatures calculated from sulfur isotope fractionation are in the range of 220-370℃, quite in agreement with those from the fluid inclusion determination. The sulfur isotope distribution and the estimated sulfur isotope composition of the ore-forming fluids lead to the presumption that sulfur in the ore field was probably rived from the deep portion of the crust. TheδC13 values of the carbonatization stage calcite from the Duobaoshan copper ore deposit are quite consistent with those of marble from the Duobaoshan formation, denoting that the carbon material of the carbonatization stage might have come from the adjacent carbonate rocks. TheδO18 values of hydrothermal solution in carbanatization stage are much lower than those of magmatic water, indicating the probable dilution of the hydrothermal solutions by underground water. The present Sr87/Sr86 ratios of granodiorite, granodiorite porphyry, plagioclase granite, andesite and andesite porphyry range from 0.6994 to 0.7096 whereas the initial Sr87/Sr86 values of granodiorite porphyry and plagioclae granite are 0.7054 and 0.7037 respectively, implying that all these intrusives possess identical initial Sr87/Sr86 ratio and are hence the products of the same sources formed during different stages of tectonic and magmatic activities. |
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