2015 GSA Annual Meeting in Baltimore, Maryland, USA (1-4 November 2015)

Paper No. 206-5
Presentation Time: 9:00 AM-6:30 PM


KHOURY, Hani Nicola, Geology, University of Jordan, Queen Rania street, P.O.Box 17167, Amman, 11942, Jordan and CLARK, Ian D., Department of Earth Sciences, University of Ottawa, Advanced Research Complex, 25 Templeton St, Ottawa, ON K1N 6N5, Canada, khouryhn@yahoo.com

Secondary yellow uranium minerals (uranyl vanadates) together with unique green smectites (Cr-rich smectite/volkonskoite) are hosted in altered varicolored marble and chalk marl/travertine, and/or calcrete/top soil (saprolite) of central Jordan. Tyuyamunite Ca(UO2)2V5+2O8•3(H2O) - strelkinite Na2(UO2)2V2O8•6(H2O) solid solution series (uranmica) are the major components and their composition reflects changes in the Ca /Na ratio of the circulating water. The Ca-end member tyuyamunite is also common in the secondary veins of the altered varicolored marble. The Na-rich member (strelkinite) is dominant in the calcrete/top soil (saprolite) and its precipitation is related to continuous evaporation during seasonal dry periods.

Tyuyamunite- strelkinite phases are intermixed with the porous fine grained matrix (>50 um to < 2 um). The uranium phases have two stages of crystallization. The earlier stage is composed of very fine crystallites (less than 1 μm) intermixed with the matrix. The coarser later stage (up to >50μm) fills pores and weakness zones. The matrix is composed of U-F-bearing aggregates of intermixed calcite, carbonate-fluorapatite, and variable amounts of clay minerals dominated by smectite (montmorillonite), gypsum, barite, halite and fluorite. The porosity of the host rock controls tyuyamunite- strelkinite distribution. The green smectite fills voids and cavities of the altered marble, chalk marl/travertine and Recent calcrete/top soil deposits.

New primary calcium uranate phases (restricted to the varicolored marble) were also identified. The calculated structural formulae were CaUO4, Ca2UO5, Ca3UO6, Ca3U2O9, Ca4UO7, Ca5UO8, and Ca6UO9. Crystallization of calcium uranate phases is the result of oxidation of U+4 at high temperature as a result of combustion of phosphorus-rich bituminous marl into U+6under high oxygen fugacity.