| 中国东南陆缘区中生代膨润土矿床同位素地球化学研究 |
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| 关键词:bentonite deposit montmorillonite isotope geochemistry continental margin of southeast China |
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| Isotope Geochemistry of Mesozoic Bentonite Deposits in Continental Margin of Southeast China |
| The Mesozoic volcanic rock region in continental margin of southeast China is one of major bentonite ore producing area in the country.The studies of isotopic geochemistry have been carried out for eight bentonite deposits from four provinces(Jiangsu,Anhui,Zhejiang and Fujian).Hydrogen,oxygen and silicon isotopes are determined for 23 montmorillonite samples,separated from the various types of bentonite ores,it is suggested that,the Na_montmorillonites have δ D values of -71‰ to -82‰ and δ 18 O values of 10.9‰ to 14.6‰ respectively, and the Ca_and Al(H)_montmorillonite have δ D values of -50‰ to-70‰ and δ 18 O values of 15.1‰ to 18.1‰ respectively, but the δ 30 Si values of three types of the montmorillonites lie in the same range of -0.3‰ to +0.3‰. The hydrogen and oxygen isotopic compositions of the Na_motmorillonites are not only obviously different from those of the Ca_or Al(H)_montmorillonites but also the mean δ D value between them,it is good corresponding to that between the Mesozoic and the present meteoric waters in the region. However, in the δ D versus δ 18 O correlogram three types of the montmorillonites all lie in the area between 35℃and 100℃ hydrothermal montmorillonite lines, and all δ 30 Si values also exhibit the characteristics of hydrothermal clay minerals. On the bases of the distinguishing of these isotopic traces above and combined with the geological characteristics of the deposits, authors suggest that the Na_bentonites of continental facies in the region belong to a result of low temperature hydrothermal alteration, but they may have be retrofitted naturally into the Ca_and/or Al(H)_bentonites by the action of present environment water in the locality. |
| XU Bu-tai,HUANG Jian-guo.1997.Isotope Geochemistry of Mesozoic Bentonite Deposits in Continental Margin of Southeast China[J].Acta Geoscientica Sinica,18(3):275-281. |
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