摘要
本文报道了白云鄂博矿区Ｈ９变质岩富钾板岩、暗色板岩和变质基性火山岩的ＳｍＮｄ年龄数据，讨论了上述变质岩的成因及与稀土矿床成矿关系。
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.
关键词
变质岩
钐
钕
同位素年龄
矿床成矿
bentonite deposit montmorillonite isotope geochemistry continental margin
of southeast China
