| 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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| 引用本文：徐步台,黄建国.1997.中国东南陆缘区中生代膨润土矿床同位素地球化学研究[J].地球学报,18(3):275-281. |
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| 中文摘要:本文列述了８个膨润土矿床的２３个不同属性蒙脱石的氢、氧和硅同位素分析结果。其中，钠基蒙脱石δＤ值为－７１‰～－８０‰和δ１８Ｏ值为１０．９‰～１４．６‰；钙基或铝（氢）基蒙脱石δＤ值为－５０‰～－７０‰和δ１８Ｏ值为１５．１‰～１８．１‰；它们的δ３０Ｓｉ值－０．３‰～＋０．３‰。通过这些同位素示踪判别并结合矿床地质特征，提出了该区中生代陆相膨润土属低温热液蚀变成因及其在现代（近代）环境水的再作用下天然改型过程的新的同位素证据。 |
| 中文关键词:膨润土矿床 蒙脱石 同位素地球化学 中国东南陆缘区 |
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| Isotope Geochemistry of Mesozoic Bentonite Deposits in Continental Margin of Southeast China |
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| Abstract: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. |
| keywords:bentonite deposit montmorillonite isotope geochemistry continental margin of southeast China |
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