| 大鲍庄和罗河铁矿区硫同位素特征及其成因的探讨 |
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| 引用本文：.1983.Sulfur Isotope Studies Of The Dabaozhuang And Luohuo Iron Deposits With An Approach To Their Genesis[J].Mineral Deposits,2(4):26~34 |
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| Sulfur Isotope Studies Of The Dabaozhuang And Luohuo Iron Deposits With An Approach To Their Genesis |
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| Abstract:Some knowledge has been acquired concerning the δS34 values of the sulfur- bearing minerals from Dabaozhuang arid Luohuo deposits and the genesis of these two deposits: 1. TheδS34 values of sulfur-bearing minerals from both deposits spread within relatively wide limits, varying from +18.3‰ to -14‰ with a total range up t0 32.3‰. In consideration of the geological setting, the initial sulfur is supposed to be a mixture derived from both the deep-seated source arid sulfates in the crust. 2. TheδS34 values of pyritc are also dispersed within a comparatively broad range of 25‰ (from +11‰ to –-14 l‰). In cross section, they decrease gradually in the upward direction: +6.3‰ in subvolcanic rocks, +2.0‰ in massive pyrite ores, -2.5‰ in silicified rocks and -5.9‰ in tuff. In contrast, the δS34 values of anhydrite tend to increase in the same direction: +15.l‰ in the intrusive bodies and +16.1‰ in the bedded anhydrite. Such a systematic variation in theδS34 values might be primarily attributed to the thermodynamic effects of the sulfur isotopic fractionation. 3. Tuff in the lower part of the second cycle shows microlamination structure characterized by relatively clear rhythm with fossil plant observed as intercalations in it. TheδS34 values of pyrite occurring in it are also rather scattered, mostly negative, the lowest being -14‰ and the average -5.9‰. This might be referable to the important role the kinetic effects (bacteria- biotic fraction action) played as well as the thermodynamic effects of the isotopic fractionation mentioned above. 4. Decrepitation temperature measurement of pyrite from massive sulfide ore bodies or silicified rocks of Dabaozhuang indicate that temperatures reached as high as 240-250℃ near the center of the pneumato-hydrothermal activity where theδS34 values vary from +3.9 to 8.4‰. Away from the center, the formation temperatures of pyrite gradually decrease to 210-220℃ and itsδS34 values change to -1.8~ 4.5‰ accordingly. All this suggests that the volcanic pneumato-hydrothermal activity might have had an important bearing on the formation of pyrite. |
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