Hostname: page-component-cd9895bd7-7cvxr Total loading time: 0 Render date: 2024-12-27T09:02:54.390Z Has data issue: false hasContentIssue false
  • English
  • Français

High P-T experimental metasomatism of a fluorapatite with significant britholite and fluorellestadite components: implications for LREE mobility during granulite-facies metamorphism

Published online by Cambridge University Press:  05 July 2018

D. E. Harlov ,
H.-J. Förster  and
C. Schmidt
D. E. Harlov*
Affiliation:
GeoForschungsZentrum Potsdam, Telegrafenberg, D-14473 Potsdam, Germany
H.-J. Förster
Affiliation:
Institute of Earth Sciences, University of Potsdam, P.O. Box 601553, D-14415 Potsdam, Germany
C. Schmidt
Affiliation:
Institute of Earth Sciences, University of Potsdam, P.O. Box 601553, D-14415 Potsdam, Germany
*
* E-mail: dharlov@gfz-potsdam.de
Get access Rights & Permissions [Opens in a new window]

Abstract

A LREE-, Si-, S-enriched fluorapatite with ∼7.7 wt.% LREE2O3, 5.3 wt.% SiO2 and 3.5 wt.% SO3 from the Mushugai-Khuduk REE deposit, southern Mongolia, has been experimentally metasomatized in pure H2O at 900°C and 1000 MPa. Despite the high LREE content, inclusions or rim grains of monazite did not form during fluid-induced metasomatism. Under high-contrast BSE imaging, the reacted fluorapatite presents a mottled appearance with light, moderate and dark areas and hosts large fluid inclusions containing anhydrite as the solid phase. Dark areas show moderate depletion in all the LREE. Measurable HREE such as Gd and Y remain unchanged. In the areas of intermediate brightness, Ce and, to a lesser extent, La are moderately enriched relative to the original fluorapatite. In the light areas, Ce and La display strong enrichment, whereas the other LREE, Gd and Y remain little changed. In the dark areas, depletion in LREE is matched by depletion in Si and Na, satisfying the coupled substitution reactions Si4+; + (LREE)3+ = P5+ + Ca2+ and Na+ + (LREE)3+ = 2Ca2+. In the light areas, enrichment in LREE and P is accompanied by depletion in Si, Na and S, implying operation of two different coupled substitution reactions, namely: 2P5+ = Si4+ + S6+ and 2P5+ + LREE3+ = 2S6+ + Na+. In all areas, strong enrichment in F is accompanied by strong depletion in Cl and OH. The formation of large, fluid and anhydrite-filled inclusions associated with the LREE-enriched light areas is evidence of a negative volume change, combined with additional local dissolution of the fluorapatite. This occurred during the metasomatism of the original Cl- and OH-bearing fluorapatite to a nearly pure end-member fluorapatite. Local dissolution of fluorapatite in the space now occupied by the voids, combined with element remobilization from the body of the fluorapatite as a whole, provided the Ca and S needed for the formation of anhydrite as well as the P and LREE required for the enrichment of the bright areas.

Keywords

britholitefluorellestaditefluorapatite, metasomatismexperimentalitalicLREE
Type
Research Article
Information
Mineralogical Magazine , Volume 67 , Issue 1 , February 2003 , pp. 61 - 72
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2003

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

Andreeva, I.A., Kovalenko, V.I. and Naumov, V.B. (2001) Silicate, silicate-salt and salt magmas of the alkaline carbonatite-bearing complex Mushugai- Khuduk in Southern Mongolia: evidence of melt inclusions. ECROFI XVI Abstract Volume, Porto, pp. 3—5.Google Scholar
Burt, D.M. (1989) Compositional and phase relations among rare earth element minerals. Pp. 259—307 in: Geochemistry and Mineralogy of Rare Earth Elements (Lipin, B.R. and McKay, G.A., editors). Reviews in Mineralogy, 21. Mineralogical Society of America, Washington, D.C.Google Scholar
Comodi, P., Liu, Y., Stoppa, F. and Wolley, A.R. (1999) A multi-method analysis of Si-, S- and REE-rich apatite from a new find of kalsilite-bearing leucitite (Abruzzi, Italy). Mineralogical Magazine, 63, 661—672CrossRefGoogle Scholar
Fleet, M.E. and Pan, Y. (1995) Site preference of rare earth elements in fluorapatite. American Mineralogist, 80, 329—335CrossRefGoogle Scholar
Fleet, M.E., Liu, X. and Pan, Y. (2000) Rare-earth elements in chlorapatite [Ca10(PO4)6Cl2: uptake, site preference and degradation of monoclinic structure. American Mineralogist, 85, 1437—1446CrossRefGoogle Scholar
Gierke, R. (1996) Formation of rare earth minerals in hydrothermal systems. Pp. 105—150 in: Rare Earth Minerals. Chemistry, Origin and Ore Deposits (Jones, A.P., Wall, F. and Williams, C.T., editors). The Mineralogical Society Series, 7. Chapman & Hall, London.Google Scholar
Harlov, D.E. and H-J., Förster (2002) High-grade fluid metasomatism on both a local and regional scale: the Seward Peninsula, Alaska and the Val Strona di Omegna, Ivrea-Verbano zone, northern Italy. Part II: Phosphate mineral chemistry. Journal of Petrology, 43, 801—824CrossRefGoogle Scholar
Harlov, D.E. and Förster, H.J. (2003) Fluid-induced nucleation of (Y + REE)-phosphate minerals in apatite: Nature and experiment. Part II. Fluorapatite. American Mineralogist (in press).CrossRefGoogle Scholar
Harlov, D.E. and Milke, R. (2002) Stability of corundum + quartz relative to kyanite and sillimanite at high temperature and pressure. American Mineralogist , 87, 424—432CrossRefGoogle Scholar
Harlov, D.E., Förster, H.J. and Nijland, T.G. (2002a) Fluid-induced nucleation of (Y + REE)-phosphate minerals in apatite: Nature and experiment. Part I. Chlorapatite. American Mineralogist, 87, 245—261CrossRefGoogle Scholar
Harlov, D.E., Andersson, U.B., Förster, H.J., J.O., Nystrom, Dulski, P. and Broman, C. (2002b) Apatite- monazite relations in the Kiirunavaara magnetite- apatite ore, northern Sweden. Chemical Geology , 191, 47—72.CrossRefGoogle Scholar
Johannes, W. (1973) Eine vereinfachte Piston-Zylinder- Apparatur hoher Genauigkeit. Neues Jahrbuch fur Mineralogie Monatshefte, 337—351.Google Scholar
Johannes, W., Bell, P.M., Mao, H.K., Boettcher, A.L., Chipman, D.W., Hays, J.F., Newton, R.C. and Siefert, F. (1971) An interlaboratory comparison of piston-cylinder pressure calibration using the albite- breakdown reaction. Contributions to Mineralogy and Petrology, 32, 24—38CrossRefGoogle Scholar
Kempe, U. and Götze, J. (2002) Cathodoluminescence (CL) behaviour and crystal chemistry of apatite from rare-metal deposits. Mineralogical Magazine , 66, 135—156CrossRefGoogle Scholar
Oberti, R., Ottolini, L., Della Ventura, G. and Parodi, G.C. (2001) On the symmetry and crystal chemistry ofbritholite: new structural and microanalytical data. American Mineralogist, 86, 1066—1075CrossRefGoogle Scholar
Pan, Y., Fleet, M.E. and Macrae, N.D. (1993) Oriented monazite inclusions in apatite porphyroblasts from the Hemlo gold deposit, Ontario, Canada. Mineralogical Magazine , 57, 697—707.CrossRefGoogle Scholar
Putnis, A. (2002) Mineral replacement reactions: from macroscopic observations to microscopic mechanisms. Mineralogical Magazine , 66, 689—708CrossRefGoogle Scholar
Rundqvist, I.K., Baskina, V.A. and Ontoev, D.O. (1995) Mushugay-Khuduk REE-Fe-F deposit in Southern Mongolia. Global Tectonics and Metallogeny, 5, 41—51.CrossRefGoogle Scholar
Samoilov, V.S. and Kovalenko, V.I. (1983) Alkaline rock-carbonatite complexes of Mongolia (in Russian). Nauka, Moscow, 200 pp.Google Scholar
Strunz, H. and Nickel, E.H. (2001) Strunz Mineralogical Tables, Chemical-Structural Mineral Classification System, 9th edition. Schweizerbartsche Verlagsbuch- handlung, Stuttgart, 870 pp.Google Scholar