粤北棉花坑铀矿床蚀变花岗岩副矿物特征研究

采用电子探针等测试方法,对采自棉花坑铀矿床特富矿体蚀变花岗岩中的副矿物,特别是富铀副矿物进行研究。蚀变花岗岩中的副矿物有锆石、直氟碳钙铈矿、铀石-钍石、磷灰石、磷钇矿、褐帘石等,其中主要富铀副矿物有铀石-钍石、磷钇矿、独居石。研究表明,热液作用能使副矿物的晶体结构和成分发生改变,甚至形成新的矿物,同时使富铀副矿物释放大量的铀进入成矿流体,如磷钇矿蚀变为磷灰石、铀钍石蚀变为铅钍石、独居石可蚀变为直氟碳钙铈矿等;磷灰石、锆石、褐帘石等副矿物铀含量较低,而且在蚀变过程中,它们保持相对稳定,且晶形完好,释放的铀量少;部分蚀变锆石出现相反情况,其铀含量不降反升。研究还表明,富铀副矿物受热液作用越强,即距热液活动中心越近,铀含量的降低越明显,释放的铀就越多,从而为铀矿床的形成提供了丰富的铀源。

Compositions Study on Auxiliary Minerals in Altered Granitic Rocks of Mianhuakeng Uranium Deposit in Northern Guangdong

The Mianhuakeng Uranium Deposit is one of the most important uranium base with complex mineralization conditions. In the paper, the characteristics of minerals have been systematically studied with the electron-microprobe in altered rock of the deposit. It sees that the minerals association is Pitchblende, Zircon, Parisite, Coffinite-Thorianite, Apatite, Xenotime, Allanite in the rocks. The main uranium resource minerals are Coffinite-Thorianite, Xenotime and Monazite. It has been a great impact on those minerals by hydrothermal mineralization when the deposit was formed, but it has been tended to decrease more uranium content in the minerals when closer to the ore body. Whole the monazite has been altered to the parisite, and the xenotime was been tended to alter to apatite, but Coffinite-Thorianite was altered to plumbothorite. In this alteration process, the minerals released of a large amount of uranium into the mineral-fluid. But apatite, zircon and allanite had a low level uranium so they were not the resource minerals.