论文部分内容阅读
尼日利亚锡石的主要来源是冲积矿床和残积矿床,其母岩是Jos台地保罗纪碱性环形杂岩(年轻花岗岩)里的黑云母花岗岩。虽然,从伟晶岩中开采出的锡石不到总产量的5%,这些伟晶岩产于由混合岩、片麻岩、泛非(较老的)花岗岩和伟晶岩所组成的前寒武纪基底杂岩内,但随着冲积和残积型矿床储量迅速枯竭,发现新储量的任务就变得十分迫切了。本文对Jos附近Gurum地区基底杂岩中的片麻岩、混合岩、伟晶岩和细晶岩内的锡石为一重要的新矿源作了首次报道。这种锡石是由上述岩石遭受淋滤、风化作用后而富集为具有经济意义的矿体的。这类锡石通常比来自侏罗纪黑云母花岗岩的冲积型锡石粒度更细且颜色更深。这一新发现有重要的岩石成因意义和经济意义,它表明基底杂岩可能是年轻花岗岩的母岩,而且可能成为一个在尼日利亚十分重要的潜在锡石来源。
Nigerian cassiterite is mainly derived from alluvial deposits and residual deposits. Its parent rock is biotite granite in the Paleozoic alkaline ring complex (young granite) of Jos Terrace. Although cassiterite mined from pegmatites is less than 5% of the total production, these pegmatites are found in the pregranules of migmatites, gneiss, Pan-African (older) granites and pegmatites Cambrian basement complex, but with the rapid depletion of alluvial and residual deposits, the task of finding new reserves becomes more and more urgent. This paper reports for the first time a new source of cassiterite, mixed rocks, pegmatites and cassites in the apatite in the basement complexes of the Gurum area near Jos in the United States. This cassiterite is leached and weathering by these rocks and enriched into economically significant ore bodies. This type of cassiterite is usually finer and darker in color than the alluvial cassiterite from Jurassic biotite granites. This new discovery has important rock genetic and economic implications, suggesting that basement complexes may be the parent rock for young granites and could become a potential source of cassiterite in Nigeria.