Hostname: page-component-78c5997874-8bhkd Total loading time: 0 Render date: 2024-11-10T06:39:16.180Z Has data issue: false hasContentIssue false
  • English
  • Français

Thorium in crandallite-group minerals: an example from a Devonian bauxite deposit, Timan, Russia

Published online by Cambridge University Press:  05 July 2018

L. E. Mordberg
L. E. Mordberg*
Affiliation:
Russian Research Geological Institute (VSEGEI), Sredny Pr. 74, St Petersburg 199106, Russia
*
E-mail: leonid_mordberg@vsegi.ru
Get access Rights & Permissions [Opens in a new window]

Abstract

A Th-rich mineral of the crandallite group has been investigated from the weathering profile of the Schugorsk bauxite deposit, Timan, Russia. It occurs within thin (up to 0.5 mm) organic-rich veinlets together with ‘leucoxene’ in the form of small shapeless grains which vary in size from 1—2 mm to 60—70 mm. Rare grains disseminated among boehmite crystals were also found. Microprobe analyses determined that the ThO2 content can be as high as 18 wt.%. The mineral composition is intermediate between crandallite CaAl3H(PO4)2(OH)6, goyazite SrAl3H(PO4)2(OH)6, Th-crandallite and svanbergite SrAl3PO4SO4(OH)6 in the beudantite group.

Comparatively high contents of Fe and Si and a very high positive Th and Fe content correlation (r = +0.98) suggest that the formula of the hypothetical Th-bearing end-member is ThFe3(PO4,SiO4)2(OH)6 with Th and Si substituting for REE and Prespectively (woodhouseite-type substitution). Another possible substitution is Th4+ + Ca2+ ⇋ 2REE3+ (florencite-type). A deficiency of cations in the X site can be explained by either the presence of carbon, undetectable by microprobe, in the crystal lattice or a lack of X-site cations due to radiation damage induced by Th. Some excess of cations in the B site (Al and Fe3+) can be explained by the presence of very small boehmite and hematite inclusions on the crandallite grain surfaces. Th-rich crandallite may be the result of alteration of an unidentified silicate mineral from the parent rock with a composition close to the simplified formula Fe2+ThSiO4(OH)2.

Keywords

bauxiteweatheringcrandallitewoodhouseitegoyazitesvanbergiteflorencitethoriumDevonianTimanRussia
Type
Research Article
Information
Mineralogical Magazine , Volume 68 , Issue 3 , June 2004 , pp. 489 - 497
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2004

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

Bárdossy, Gy. (1982) Karst Bauxites. Bauxite Deposits on Carbonate Rocks. Elsevier, Amsterdam, 441 pp.Google Scholar
Beneslavsky, S.I. (1974) Mineralogy of Bauxites, 2nd edition. Nedra, Moscow, 133 pp. (in Russian).Google Scholar
Blount, A.M. (1974) The crystal structure of crandallite. American Mineralogist, 59, 41–47.Google Scholar
Burt, D.M. (1989) Compositional and phase relations among rare earth minerals. Pp. 259–308 in: Geochemistry and Mineralogy of Rare Earth Elements (Lipin, B.R. and McKay, G.R., editors). Reviews in Mineralogy, 21. Mineralogical Society of America, Washington D.C.CrossRefGoogle Scholar
Dill, H.G. (2001) The geology of aluminium phosphates and sulphates of the alunite group minerals: a review. Earth-Science Reviews, 53, 35–93.CrossRefGoogle Scholar
Gaines, R.V., Skinner, H.C.W., Foord, E.E. and Mason, B. (1997) Dana's New Mineralogy: The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana, 8th edition. J. Wiley & Sons, New York, 1819 pp.Google Scholar
Huminicki, D.M.C. and Hawthorne, F.C. (2002) The crystal chemistry of the phosphate minerals. Pp. 123–254. in: Phosphates – Geochemical, Geobiological and Materials Importance (Kohn, M.L., Rakovan, J. and Hughes, J.M., editors). Reviews in Mineralogy & Geochemistry, 48. Mineralogical Society of America, Washington D.C.CrossRefGoogle Scholar
Kato, T. (1971) The crystal structures of goyazite and woodhouseite. Neues Jahrbuch für Mineralogie Monatshefte, 241–247.Google Scholar
Kato, T. (1990) The crystal structure of florencite. Neues Jahrbuch für Mineralogie Monatshefte, 227–231.Google Scholar
Kolitsch, U., Tieking, E.R.T., Slade, P.G., Taylor, M.R. and Pring, A. (1999) Hinsdallite and plumbogummite, their atomic arrangements and disordered lead sites. European Journal of Mineralogy, 11, 513–520.CrossRefGoogle Scholar
Likhachev, V.V. (1993) Rare-metal Bauxite-bearing Weathering Crust of the Middle Timan. Komi Nauchnu zentr UrO RAN, Syktyvkar, Russia, 224 pp. (in Russian).Google Scholar
Mordberg, L.E., Stanley, C.J. and Germann, K. (2000) Rare earth element anomalies in crandallite group minerals from the Schugorsk bauxite deposit, Timan, Russia. European Journal of Mineralogy, 12, 1229–1243.CrossRefGoogle Scholar
Mordberg, L.E., Stanley, C.J. and Germann, K. (2001) Mineralogy and geochemistry of trace elements in bauxites: the Devonian Timan deposit, Russia. Mineralogical Magazine, 65, 81–101.CrossRefGoogle Scholar
Nriagu, J.O. (1984) Phosphate Minerals: their properties and general mode of occurrence. Pp. 1–136 in: Phosphate Minerals (Nriagu, J.O. and Moore, P.B., editors). Springer-Verlag, Berlin.CrossRefGoogle Scholar
Radoslovich, E.W. (1982) Refinement of gorceixite structure in Cm. Neues Jahrbuch für Mineralogie Monatshefte, 446–464.Google Scholar
Schwab, R.G., Götz, C., Herold, H. and Oliveira, N.P. de (1990) Compounds of crandallite type: Synthesis and properties of pure Rare Earth Element-phosphates. Neues Jahrbuch für Mineralogie Monatshefte, 241–254.Google Scholar
Schwab, R.G., Götz, C., Herold, H. and Oliveira, N.P. de (1993) Compounds of crandallite type: Thermodynamics properties of Ca-, Sr-, Ba-, Pb-, La-, Ce- to Gd-phosphates and -arsenates. Neues Jahrbuch für Mineralogie Monatshefte, 551–568.Google Scholar
Van Wambeke, L. (1971) The problem of cation deficiencies in some phosphates due to alteration processes. American Mineralogist, 56, 1366–1384.Google Scholar