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HYDROTHERMAL STABILITY STUDIES OF THE ZIRCON-THORITE GROUP

Journal Article · · Geochim. et Cosmochim. Acta
The stability relations among minerals of the zirconthorite group and the effect of related oxides on them have been studied under both "dry" and hydrothermal conditions. The problem of "hydrous" zircons and its relation to the metamict state has been investigated both experimentally and theoretically. From the data it appears that hydrous zircons and thorites do not involve OH- substitution for O/sup 2-/ with omission of Si/sup 4+/, but rather are formed by strong water adsorption in metamictized zircon and thorite. The phase equilibrium involved in the thorite-huttonite polymorphism has been studied and it is concluded that hut tonite is the only stable polymorph of ThSiO/sub 4/. Zircon dissociates at 1550 plus or minus 50 deg C to ZrO/sub 2/ + SiO/sub 2/. The Alkemade triangles in the ternary systems ZrO/sub 2/ - ThO/sub 2/ - SiO/sub 2/ and ZrO/sub 2/ - UO/sub 2/ - SiO/sub 2/ have been determined and a not- impossible diagram is presented for the system ThO/sub 2/ - UO/sub 2/ - SiO/sub 2/ . The extent of solid solution between ZrSiO/sub 4/ - ThSiO/sub 4/, ZrSiO/sub 4/ "USiO/sub 4/" and ThSiO/sub 4/ - "USiO4" is discussed in connection with the composition of natural zircon and thorite. The application of the experimental data to natural mineral assemblages is discussed. (auth)
Research Organization:
Pennsylvania State Univ., University Park
Sponsoring Organization:
USDOE
NSA Number:
NSA-15-011334
OSTI ID:
4080924
Journal Information:
Geochim. et Cosmochim. Acta, Journal Name: Geochim. et Cosmochim. Acta Vol. Vol: 21
Country of Publication:
Country unknown/Code not available
Language:
English