Hostname: page-component-848d4c4894-mwx4w Total loading time: 0 Render date: 2024-06-30T01:34:57.450Z Has data issue: false hasContentIssue false

Uranoan thorite in lithophysal rhyolite–Topaz Mountain, Utah, USA

Published online by Cambridge University Press:  05 July 2018

Eugene E. Foord
Affiliation:
US Geological Survey, Box 25046, DFC, MS 905, Denver, Colorado 80225
Robert R. Cobban
Affiliation:
Department of Geology, Denver Museum of Natural History, City Park, Denver, Colorado 80205
Isabelle K. Brownfield
Affiliation:
US Geological Survey, Box 25046, DFC, MS 916, Denver, Colorado 80225

Abstract

Uranoan thorite crystals have been found occurring as a sparse constituent in lithophysae in 6.1 to 6.8 Ma alkali rhyolite flows at Thomas Mountain, Utah, USA. The crystals are associated with sandidine, quartz, topaz, hematite, magnetite, and calcite; they are leek to dark grass green, transparent, well-formed, euhedral prisms, showing development of forms {100}, {101}, and {111}. The mineral is both optically isotropic, with a refractive index of 1.86(1), and X-ray amorphous, indicating its metamict state. Electron microprobe analysis yields: SiO2 17.3, ThO2 56.8, UO2 25.4, total 99.5%, and a structural formula of (Th0.72U0.31)Σ1.03Si0.97O4.

This appears to be the first reported occurrence of thorite in volcanic rocks of rhyolitic composition, and may account for part or all of the Th reported in alkali rhyolites and so-called ‘topaz-rhyolites’ of the western USA.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1985

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Adams, J. W. (1953) U.S. Geol. Surv. Bull. 928-D, 95-119.Google Scholar
Bonshtedt-Kupletskaya, E. M., and Smolyaninova, N. N., eds. (1972) Minerals 3, part 1, 127-40 (in Russian).Google Scholar
Burt, D. M., Sheridan, M. F., Bikun, J. V., and Christiansen, E. H. (1982) Econ. Geol. 77, 1818-36.CrossRefGoogle Scholar
Desborough, G. A., and Mihalik, P. (1980) U.S. Geol Surv. Open-File Rept. 80-661, 16 pp.Google Scholar
Frondel, C. (1953) Am. Mineral. 38, 1007-18.Google Scholar
Fuchs, L. H., and Geberg, E. (1958) Ibid. 43, 243-8.Google Scholar
Hentschel, G. (1982) Mainzer Geowiss. Mitt. 8790 (in German).Google Scholar
Lindsey, D. L. (1979) U.S. Geol. Surv. Misc. Inv. Map 1-1176, 1:62 500.Google Scholar
Maras, A. (1982) Period. Mineral. 51, 233-7 (in Italian).Google Scholar
Mumpton, F. A., and Roy, R. (1961) Geochim. Cosmochim. Acta, 21, 217-38.CrossRefGoogle Scholar
Rankama, K., and Sahama, Th. G. (1950) Geochemistry. Univ. of Chicago Press.Google Scholar
Ream, L. R. (1979) Mineral. Rec. 10, 261-78.Google Scholar
Speer, J. A. (1980) Reviews in Mineralogy, 5, 113-35.Google Scholar
Staatz, M. H., and Carr, W. J. (1964) U.S. Geol. Surv. Prof. Paper 415, 188 pp.Google Scholar
Urunbaev, K. U. (1970) Zap. Vses. Mineral. Obshch. 23, 146-51.(in Russian).Google Scholar
Yang, M., and Li, Y. (1980) Uranothorite discovered in rare earth, niobium, iron deposits at Bayan Obo, Inner Mongolia, China. Kexue Tongbao, 25, 594-6.Google Scholar