我国铝土矿中微量元素的地球化学特征

Geochemistry of Trace Elements in Bauxite of China

本文对我国铝土矿中微量元素在空间和时间上的分布特点进行了研究,还对这些元素之间的比值、与Al_2O_3之间的比值、Zr-Cr-Ga的相对含量进行了探讨,得出这些元素具区域性、时间性分布的特点,它们与铝土矿的不同物质来源及其介质环境等有关。

The contents of most trace elements, especially B, Ga and Zr, in Bauxite of China, are higher than the means of that in the Crust, but those of Cu, Ba, Rb, Sc etc. are lower. Compared with other countries, the bauxite of China is obviously richer in Zr, Ga, Sr, Ba, B, Ni, Cu, Nb, poorer in Cr, V etc.The contents of more active elements (such as B, Sr, Ba, Rb) distribute in a wide range and the frequency decreases quickly with the increase of the contents.The contents of stable Zr, Cr and Ga are nearly of normal distribution. The gibbsitic bauxite formed by weathering of basalt in south-eastern China obviously reflects the features of basalt, that is rich in Cr, Co, Sc and poor in Zr, Ni. The diasporitic bauxites formed by sedimentation in different areas also have their own features, those on Yangtzi platform rich in Ga; in southwestern Guangxi and south-eastern Yunan rich in Zr, Cr; in Kangdian axis of earth rich in V, Zr; on North China platform rich in B, Sr, Ba, Ni.From north to south the contents of V and Cr are in the tendency of increasing. The contents of trace elements in bauxite is related to basal rocks, one of the reason is that some basal rocks are the source rocks, or the two have similar mother rocks, the other is that the movement of some elements takes place due to ground water in diagenesis and supergenesis. The content of Ga in bauxite decreases with the time passing.C1 and P1 bauxite are rich in Ar, Cr and V.C2 bauxite rich in B, Zr, Sr.The contents of trace elements in Mz bauxite are low, in Kz bauxite, Cr content is very high, and those of Zr, Co and V are high. In different rocks, the ratios of pairs of trace elements or with the content of A12O3 are different because of their different geochemical properties, sources and formations of the rocks. According to the distribution of trace elements and their ratio in bauxite, compared with basal rock, it found that the gibbsitic bauxite in southeastern China inherited the feature of its mother rock (basal basalt) in trace elements, withe the relative contents of Zr, Cr, Ga, and Ga / A12O3value; the sedimentary bauxites in Xiuwen, Tuanxi and Zhangjiaquan mainly originate from their basal rock; those in Pinguo, Xiaoyi and Xinzhan mainly from Al-silicate of acient continents.