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本文研究了法国利木赞马尔涅克(Margnac)和法内(Fanay)矿山的沥青铀矿、黄铁矿和铀石的矿物学和化学成分。结果表明,沥青铀矿的化学组成反映出含铀溶液和脉旁围岩之间有过化学交换。用U-Pb法测出原生沥青铀矿-黄铁矿组合形成年龄为276 Ma。沥青铀矿的铀石化期间结晶出的方铅矿的铅同位素分析给出从沥青铀矿沉淀到铀石化的时间间隔为6 Ma。电子探针分析表明,热液转换或多或少地影响到所有沥青铀矿球粒,尽管形成的铀石量不多。这导致了富Si沥青铀矿的形成,并用Pb-Pb和一致线图解法获得体系年龄为270Ma。在某些样品中还发现矿物学上没被觉察出的再活化阶段,其年龄为170—175 Ma。最后,本工作确定了地热体系的寿命(20—30 Ma),据认为这个地热体系导致了二云母花岗岩的变正长岩化、沥青铀矿的沉淀及其再活化为铀石。
In this paper, the mineralogy and chemical composition of bitumen uranium ore, pyrite and uranium from the Margnac and Fanay mines in France are studied. The results show that the chemical composition of the uranium bitumen reflects the chemical exchange between the uranium-bearing solution and the surrounding vein. U-Pb method was used to measure the age of formation of primary pitch uranium ore-pyrite combination 276 Ma. Lead isotopic analysis of galena crystallized during the uranium petrochemical uranium deposit gave a time interval of 6 Ma from precipitation of uraninite to uranium. Electron probe analysis shows that hydrothermal conversion affects, to a greater or lesser extent, all pitch-bearing uranium pellets, although the amount of uranium formed is small. This led to the formation of Si rich uraninite and the age of the system was 270 Ma using Pb-Pb and consistent line diagrams. A mineralogically unrecognized reactivation stage was also found in some samples, with an age of 170-175 Ma. Finally, this work identifies the life of the geothermal system (20-30 Ma) and it is believed that this geothermal system is responsible for the metamorphism of dikematite, the precipitation of bitumen uranium and its reactivation to uranium.