ZHANG Bang-tong, WU Jun-qi, LING Hon-fei, CHEN Pei-rong
(State Key Laboratory for Mineral Deposits Research , School of Earth Sciences, Nanjing University, Nanjing 210093, China)

Fig. Micro-grained uraninite in biotite from Fucheng granite pluton.

Abstract: Based on microscopic observation and electron microprobe analysis, the micro-grained uraninites in biotite, muscovite and plagioclase from the Fucheng strongly peraluminous granite pluton in southern Jingxi province, China were determinated. According to the mineral assemblage of the Fucheng pluton and the composition and U-Pb age of the uraninites, it is confirmed that these uraninites are attributed to primary genesis. Moreover, by using nuclei-induced fission-track method, some scatterred densely distributed fission-track spots in muscovite detector were found, which might indicate existence of uranium as independent mineral phase in rock-forming minerals. This mineral phase might be the nuclei of super-micro-grained uraninite. The chemical bond energy theory on forming U-O coordination polyhedra with increasing degree of Si-O polymerization in granite melt is proved by the existence of primary uraninite in granite. On the other hand, the primary uraninite can also be used as an important geochemical criterion for uranium metallogenetic capacity of uranium-bearing granite.

Key words: uraninite; granite; nuclei-induced; fission-track; chemical bond; Fucheng; Jingxi province

E-mail:zhangbt@nju.edu.cn

ACTA MINERALOGICA SINICA Vol. 31, No. 2, 2011, Page 166-172