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Mechanism of Saleeite Formation at the Koongarra Secondary Ore Deposit

Published online by Cambridge University Press:  15 February 2011

Takashi Murakami ,
Hiroshi Isobe ,
Toshihiko Ohnuki ,
Tsutomu Sato ,
Nobuyuki Yanase  and
Junko Kiyoshige
Takashi Murakami
Affiliation:
Mineralogical Inst., Univ. of Tokyo, Bunkyo-ku, Tokyo 113, Japan
Hiroshi Isobe
Affiliation:
Environmental Geochemistry Lab., JAERI, Tokai, Ibaraki, 319-11, Japan
Toshihiko Ohnuki
Affiliation:
Environmental Geochemistry Lab., JAERI, Tokai, Ibaraki, 319-11, Japan
Tsutomu Sato
Affiliation:
Environmental Geochemistry Lab., JAERI, Tokai, Ibaraki, 319-11, Japan
Nobuyuki Yanase
Affiliation:
Environmental Geochemistry Lab., JAERI, Tokai, Ibaraki, 319-11, Japan
Junko Kiyoshige
Affiliation:
Dept. of Earth Sciences, Ehime Univ., Matsuyama, Ehime 790, Japan
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Abstract

Rock samples in the secondary ore deposit at Koongarra, Australia, were examined mineralogically to clarify the formation mechanism of saléeite (Mg(UO2)2(PO4)2.10H2O), a major secondary uranium mineral in the secondary ore deposit. Sklodowskite (MgSi2U2O11.7H2O) veinlets, present upstream of the ore deposit, are partially replaced by saléeite. Most grains of apatite (Ca5(P04)3F), an accessory mineral of the host rock, are also replaced by saléeite. Thermodynamic calculations by EQ3NR showed that the present Koongarra ground waters are undersaturated with respect to saléeite and also suggested that saléeite can be precipitated under the condition of higher U or P concentrations. Such conditions can be created at the reaction interfaces of dissolving sklodowskite, which releases U, or dissolving apatite, which releases P. The present study indicates that saléeite is formed by local microscale saturation upstream of the secondary ore deposit, which is different from the formation mechanism of saléeite downstream of the ore deposit, where saléeite microcrystals of 1 – 20 nm in size form by catalysis on iron minerals, the weathering products of the host rock.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 412: Symposium V – Scientific Basis for Nuclear Waste Management XIX , 1995 , 809
Copyright
Copyright © Materials Research Society 1996

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