WANG Gui1, WANG Qiang1, MIAO Ai-sheng1, JIAO Yang-quan2, YI Chao3, ZHANG Kang3
(1. Geologic Party NO.208, CNNC, Baotou 014010, China;
2.China University of Geosciences, Wuhan 430074, China;
3. Beijing Research Institute of Uranium Geology, Beijing 100029, China)
Abstract: Nalinggou uranium deposit, located in northeastern of Ordos Basin, is one of the in situ leachable sandstone type uranium deposit in China. Its uranium body hosted in braided river sand body of the Zhiluo Formation, the Midde Jurassic Series, is controlled by paleo interlayer oxidation zone, occurring as tabula shape. Coffinite is the main uranium mineral with uraninite and brannerite. The CaO content of uraninite is relatively high; the content of UO2 in coffinite is relatively low; SiO2 is relatively high, and w(UO2)/ w(SiO2) (1:1.29) is far lower than normal value; brannerite are characterized by high UO2 and low TiO2. According to uranium minerals’ formation and acceleration mechanism, we obtained that Nalinggou uranium deposit belongs to acid environment at the paleo interlayer oxidation zone developmental stage, the activity of SiO2 is relatively low, and mainly generated uraninite. After the Late Eocene, oxidationwas poorly developed and the ore bearing sand body was reduced secondly. The petrogeochemical environment turned to weak alkaline, so the activity of SiO2 increased, and prompted the pre-forming uraninite transformed into coffinite. The brannerite formed with metasomatism of UO2 in uranium-bearing solution and Fe2+ in ilmenite with the action of oxidization-reduction.
Keywords: coffinite; uraninite; brannerite; formation mechanism; Nalinggou uranium deposit
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ACTA MINERALOGICA SINICA Vol. 37, No. 4, 2017, Page 461-468
