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据尼日利亚地质学家J.Postor报道,最近对尼日利亚乔斯附近古龙河东岸两个前寒武纪基底杂岩的黑云母片麻岩、细晶岩、伟晶岩进行了详细研究。结果发现,这些岩石都含有锡石,平均含量分别为188.7克/吨、183.7克/吨和182.6克/吨。这些岩石受到风化和淋滤使锡石富集而具有开采价值。锡石的粒度大部分呈他形肾状,边缘呈圆凹形,是锡石在高温下形成的典型特征。这类锡石与侏罗纪黑云母花岗岩河流残积沉积物中的锡石相比,往往粒度较细(0.1～1.5毫米),颜色较黑。
According to Nigerian geologist J.Postor, the biotite gneiss, pristine and pegmatite from two Precambrian basement complexes on the eastern bank of the Gulong River near Jos in Nigeria have been studied in detail recently. The rocks were found to contain cassiterite, with average contents of 188.7 g / t, 183.7 g / t and 182.6 g / t respectively. These rocks are exploited by weathering and leaching to enrich the cassiterite. Cassiterite most of his size was kidney-shaped, the edge was round concave, cassiterite is formed at high temperatures typical features. Compared with the cassiterite in the sediments of the Jurassic biotite granite river, this type of cassiterite tends to be finer in grain size (0.1-1.5 mm) and darker in color.