WEI Jia, CHEN You-liang, CHANG Dan
(Key Laboratory of Applied Nuclear Techniques in Geosciences, Chengdu University of Technology, Chengdu 610059, China)

Abstract: Silicalites is one of the most important ore-bearing rocks in the ore-bearing strata of the Zoige uranium orefield. This research shows that the average value of SiO2 is 95.72%. There are almost no terrigenous argillaceous sediment present. The average ratio of Al/(Al+Fe+Mn) is 0.21. The Al-Fe-Mn diagram and Al2O3-SiO2 diagram show the silicalites has hydrothermal sedimentary characteristics. The averages ratio of MnO/TiO2 is 5.23, indicating the silicalites may have been formed in a deep sea basin environment. The average ratio of MgO/Al2O3 is up to 0.94, indicating formation in water with high-salinity depositional environment. With respect to trace elements, the ratio of Th/U and Sr/Ba are both far lower than 1. In North American standardized REE curve most silicalites deposits have negative Ce anomalies and positive Eu anomalies both indicating the a hydrothermal origin. The value of d30Si of the silicalites and quartz veins range from -0.1% to +0.5%, also indicating a hydrothermal origin. Comprehensive studies have shown that silicalites in the ore-bearing strata in the Zoige uranium orefield have a hydrothermal origin. The average value of uranium is 10.96×10-6, and the average value of thorium is 0.53×10-6. The Th/U ratio is only 0.06, indicating the enriched uranium deposited construction. The high uranium content of silicalites and the extremely low Th/U ratio are very favourable to uranium mineralization. Consequently, the silicalites formed by hydrothermal sedimentary has laid a good foundation for late uranium metallogenic mineralization.

Key words: silicalites; hydrothermal origin; carbonate-siliceous-pelitic uranium deposits; the Zoige uranium orefield

E-mail: chenyouliang09@cdut.cn

ACTA MINERALOGICA SINICA Vol. 34, No. 4, 2014, Page 566-572