摘要
本文重点分析了我国几个典型铝土矿床中硬铝石,勃姆石、三水铝石和高岭石的氢、氧同位素组成,在δD-δ^(18)O图上标定了硬铝石线。研究表明,高岭石为源自古凤化壳的碎屑矿物;黔中地区古大气降水的δD值为-30—-45‰左右;含Ti、Fe泥微晶硬铝石和无Ti、Fe亮晶硬铝石的δ^(18)O、δD值显著不同,具不同的成因特征。这些为华南晚古生代位于低纬度地区和黔中、豫西硬铝石铝土矿是典型的多因复成矿床的认识提供了稳定同位素证据。
With the help of X-ray diffraction, transmission electron microscope (H-800) and many other detecting methods, the authors determined the purity of samples. Isotopic results have been corrected and diaspore line on the δ_(18)O-δD diagram has bees marked. Hydrogen and oxygen isotopic compositions of diaspore, boehmite, gibbsite and kaolinite in a few typical bauxite deposits in China are analysed.The study indicates that the coexisting water of gibbsites in the Pinggo and Changpu deposits exhibits the characteristics of recent meteoric water. Coexisting water in boehmite (δD:-35.3‰～-42.2‰) in central Guizhou also shows the features of meteoric watter, but its δD values are higher than those of recent meteoric water in this area. Kaolinites in Palaeozoic bauxite deposits (δ_(18)O:17.0‰～20.5‰) are mainly derived from terrigenous fragments of the weathering paleocrust and have not suffered from the influence of regional metamorphism. δD values of paleo- meteoric water in central Guizhon are approximately-30‰～-45‰, which indicates that South China was in the low-latitude zone with a hot and wet climate during the late Palaeozoic. According to the compositions of H and O isotopes, diaspores can be divided into two categories. One is micrites with Ti and Fe and high δM values (δ_(18)O: 16.5‰, δD: -80.3‰); the other is spars without Ti and Fe and with low δM values (δ_(18)O: 1.84‰, δD: -189.9‰). The coexisting waters both show the features of meteoric water, but belong to the products of different stages and different mineralizations. The former with high δM values was mainly produced by dehydrated recrystallication of gibbsites in weathering paleocrust, while the latter with low δM values was produced by strong hydrothermal remoulding of bauxite by groundwater derived from meteoric source. The H and O isotope compositions reveal the nature of laterication of initial bauxite and polygenetic compound features of diaspore bauxite.
出处
《地质论评》
CAS
CSCD
北大核心
1989年第1期21-29,共9页
Geological Review
