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Complex exsolution microstructures in ilmenite–pyrophanite from the Garnet Codera dyke pegmatite (Central Italian Alps): an electron microscopy investigation

Published online by Cambridge University Press:  02 January 2018

Gian Carlo Capitani
Gian Carlo Capitani*
Affiliation:
Department of Earth and Environmental Sciences, University of Milano-Bicocca, P.za della Scienza, 4, 20126 Italy
*
E-mail: giancarlo.capitani@unimib.it
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Abstract

Ilmenite–pyrophanite crystals from a garnet pegmatite dyke from the Upper Codera Valley (Sondrio, Italian Alps) showing exsolutions of titanohematite and columbite-tantalite were investigated by scanning and transmission electron microscopy. The titanohematite precipitates share the same crystallographic orientation of the ilmenite-pyrophanite host, are bean-shaped when observed on sections inclined to the pinacoidal section, and are elongated when observed on sections closer to the prism section, possibly because of their discoidal shape parallel to (001). The columbite-tantalite precipitates form a hexagonal network of needles elongated along ⟨110⟩ of the ilmenite–pyrophanite and titanohematite host. The following crystallographic relationship was established: [100]Col//[001]Ilm; [001]Col//[110]Ilm; , which can be explained in terms of preservation of the oxygen close packing between the ilmenite and columbite structures. The interfaces between any two of the three different phases are coherent but show lattice strain contrast and sometimes dislocations because of their different unit-cell dimensions. On the basis of textural observations, titanohematite is supposed to exsolve first, followed by columbite-tantalite at temperatures below 500°C. The addition of MnO to the Fe2O3–FeTiO3 system is supposed to considerably influence the topology of the related T-X phase diagram and the solubility of Nb2O5 and Ta2O5 in this system.

Keywords

ilmenitepyrophanitetitanohematitecolumbitetantaliteexsolutiontransmission electron microscopy
Type
Research Article
Information
Mineralogical Magazine , Volume 81 , Issue 5 , October 2017 , pp. 1087 - 1104
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2017

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References

Bedogné, F., Maurizio, R., Montrasio, A. and Sciesa, E. (1995) I Minerali della Provincia di Sondrio e della Bregaglia Grigionese: Val Bregaglia, Val Masino, Val Codera e Valle Spluga. Bettini, Sondrio, p. 300.Google Scholar
Beurlen, H., Thomas, R., Da Silva, M.R.R. and Silva, D. (2006) Manganocolumbite and cassiterite exsolution lamellae in ilmenite from the Pitombeiras pegmatite (Acari – Rio Grande do Norte) in the Borborema Pegmatitic Province, NE-Brazil. Estudos Geológicos, 16, 3–15.Google Scholar
Blake, R.L. and Hessevick, R.E. (1966) Refinement of the hematite structure. American Mineralogist, 51, 123–129.Google Scholar
Burton, B.P. (1991) The interplay of chemical and magnetic ordering. Pp. 303–321: Oxide Minerals: Petrologic and Magnetic Significance (Lindsley, D.H., editor). Reviews of Mineralogy, 25. Mineralogical Society of America, Washington, DC. CrossRefGoogle Scholar
Capitani, G.C. and Mellini, M. (2000a) The crystallisation sequence of the Campiglia M.ma skarn (Livorno, central Italy). Neues Jahrbuch für Mineralogie Monatshefte, 3, 97–115.Google Scholar
Capitani, G.C. and Mellini, M. (2000b) The johannsenite– hedenbergite complete solid solution: clinopyroxenes from the Campiglia Marittima skarn. European Journal of Mineralogy, 12, 1215–1227.CrossRefGoogle Scholar
Capitani, G.C., Oleynikov, P., Hovmoeller, S. and Mellini, M. (2006) A practical method to detect and correct for lens distortion in the TEM. Ultramicroscopy, 106, 66–74.CrossRefGoogle ScholarPubMed
Capitani, G.C., Mugnaioli, M. and Guastoni, A. (2016) What is the actual structure of samarskite-(Y)? ATEM investigation of metamict samarskite from the Garnet Codera dyke pegmatite (Central Italian Alps). American Mineralogist, 101, 1679–1690.CrossRefGoogle Scholar
Carmichael, I.S.E. (1967) The iron-titanium oxides of silicic volcanic rocks and their associated ferromagnesian silicates. Contributions to Mineralogy and Petrology, 14, 36–64.CrossRefGoogle Scholar
Černý, P. and Ercit, T.S. (1989) Mineralogy of niobium and tantalum: crystal chemical relationships, paragenetic aspects and their implications. Pp. 27–79 in: Lanthanides, Tantalum, Niobium: Mineralogy, Geochemistry, Characteristics of Primary Ore Deposits, Prospecting, Processing and Applications (Moeller, P., Cerný, P. and Saupé, F., editors). Springer, Heidelberg, Germany.CrossRefGoogle Scholar
Chakhmouradian, A.R. and Mitchell, R.H. (1999) Niobian ilmenite, hydroxylapatite, sulfatian monazite: alternative hosts for incompatible elements in calcite kimberlite from Internatsional’naya, Yakutia. The Canadian Mineralogist, 37, 1177–1189.Google Scholar
Cliff, G. and Lorimer, G.W. (1975) The quantitative analysis of thin specimens. Journal of Microscopy, 103, 203–207.CrossRefGoogle Scholar
De Michele, V. and Zezza, U. (1979) Le pegmatiti dell’Alta Val Codera (Sondrio) nell’area di Punta Trubinasca. Atti della Società italiana di scienze naturali e del Museo civico di storia naturale di Milano, 120, 180–194.Google Scholar
Ercit, T.S. Wise, M.A. and Černý, P. (1995) Compositional and structural systematics of the columbite group. American Mineralogist, 80, 613–619.CrossRefGoogle Scholar
Evans, B.W., Scaillet, B. and Kuehner, S.M. (2006) Experimental determination of coexisting irontitanium oxides in the systems FeTiAlO, FeTiAlMgO, FeTiAlMnO, and FeTiAlMgMnO at 800 and 900°C, 1-4 kbar, and relatively high oxygen fugacity. Contributions to Mineralogy and Petrology, 152, 149–167.CrossRefGoogle Scholar
Garanin, V.K., Kudryavtseva, G.P. and Lapin, A.V. (1980) Typical features of ilmenite from kimberlites, alkaliultrabasic intrusions, and carbonatites. International Geology Review, 21, 1025–1050.CrossRefGoogle Scholar
Gaspar, J.C. and Wyllie, P.J. (1983) Ilmenite (high Mg, Mn, Nb) in the carbonatites from the Jacupiranga Complex, Brazil. American Mineralogist, 68, 960–971.Google Scholar
Guastoni, A., Pennacchioni, G., Pozzi, G., Fioretti, A.M. and Walter, J.M. (2014) Tertiary pegmatite dykes of the Central Alps. The Canadian Mineralogist, 52, 641–669.CrossRefGoogle Scholar
Lindsley, D.H. (1991) Experimental studies of oxide minerals. Pp. 69–106 in: Oxide Minerals: Petrologic and Magnetic Significance (Lindsley, D.H., editor). Reviews in Mineralogy, 25. Mineralogical Society of America, Washington DC.CrossRefGoogle Scholar
Haggerty, S.E. (1991) Oxide texture – a mini-atlas. Pp. 129–219 in: Oxide Minerals: Petrologic and Magnetic Significance (Lindsley, D.H., editor). Reviews in Mineralogy, 25. Mineralogical Society of America, Washington DC.CrossRefGoogle Scholar
Harrison, R.J. and Becker, U. (2001) Magnetic ordering in solid solutions. European Mineralogical Union Notes in Mineralogy, 3, 349–383.Google Scholar
Hirtopanu, P., Fairhurst, R.J. and Jakab, G. (2015) Niobian rutile and its associations at Jolotca, Ditrau Alkaline Intrusive Massif, East Carpathians, Romania. Proceedings of the Romanian Academy, Series B, 17, 39–55.Google Scholar
Kasama, T., Golla, U. and Putnis, A. (2003) High resolution and energy filtered TEM of the interface between hematite and ilmenite exsolution lamellae: relevance to the origin of lamellar magnetism. American Mineralogist, 88, 1190–1196.CrossRefGoogle Scholar
Kasama, T., McEnroe, S.A., Ozaki, N., Kogure, T. and Putnis, A. (2004) Effects of nanoscale exsolution in hematite–ilmenite on the acquisition of stable natural remanent magnetization. Earth and Planetary Science Letters, 224, 461–475.CrossRefGoogle Scholar
Mazzullo, L.J., Dixon, S.A. and Lindsley, D.H. (1975) T-fO2 relationships in Mn-bearing Fe-Ti oxides. Geological Society of America, Abstracts Program, 7, 1192.Google Scholar
McEnroe, S.A., Harrison, R.J., Robinson, P., Golla, U. and Jercinovic, M.J. (2001) Effect of fine-scale microstructures in titanohematite on the acquisition and stability of natural remanent magnetization in granulite facies metamorphic rocks, southwest Sweden: implications for crustal magnetism. Journal of Geophysical Research, 106(B12), 30523–30546.CrossRefGoogle Scholar
McEnroe, S.A., Harrison, R.J., Robinson, P. and Langenhorst, F. (2002) Nanoscale haematite–ilmenite lamellae in massive ilmenite rock: an example of lamellar magnetism with implications for planetary magnetic anomalies. Geophysical Journal International, 151, 890–912.CrossRefGoogle Scholar
McEnroe, S.A., Langenhorst, F., Robinson, P., Bromiley, G.D. and Shaw, C.S.J. (2004) What is magnetic in the lower crust? Earth and Planetary Science Letters, 226, 175–192.CrossRefGoogle Scholar
Mitchell, D.R.G. (2015) Development of an ellipse fitting method with which to analyse selected area electron diffraction patterns. Ultramicroscopy, 160, 140–145.CrossRefGoogle ScholarPubMed
Mitchell, R.H. and Liferovich, R.P. (2004) Ecandrewsitezincian pyrophanite from lujavrite, Pilansberg alkaline complex, South Africa. The Canadian Mineralogist, 42, 1169–1178.CrossRefGoogle Scholar
Mitchell, R.H., Scott-Smith, B.H. and, Larsen, L.M. (1999) Mineralogy of ultramafic dikes from the Sarfartoq, Sisimiut and Maniitsoq areas, West Greenland. Proceedings of the VII International Kimberlite Conference, 2, 574–583.Google Scholar
Mugnaioli, E., Capitani, G.C., Nieto, F. and Mellini, M. (2009) Accurate and precise lattice parameters by selected area electron diffraction in the transmission electron microscope. American Mineralogist, 94, 793–800.CrossRefGoogle Scholar
Robinson, P., Harrison, R.J., McEnroe, S.A. and Hargraves, R.B. (2002) Lamellar magnetism in the haematite–ilmenite series as an explanation for strong remanent magnetization. Nature, 418, 517–520.CrossRefGoogle ScholarPubMed
Robinson, P., Harrison, R.J., McEnroe, S.A. and Hargraves, R.B. (2004) Nature and origin of lamellar magnetism in the hematite–ilmenite series. American Mineralogist, 89, 725–747.CrossRefGoogle Scholar
Tarantino, S.C., Zema, M., Capitani, G.C., Scavini, M., Ghigna, P., Brunelli, M. and Carpenter, M.A. (2011) Rhombic-shaped nanodomains in columbite driven by contrasting cation order. American Mineralogist, 96, 374–382.CrossRefGoogle Scholar
Uher, P., Černý, P., Chapman, R., Határ, J. and Miko, O. (1998) Evolution of Nb,Ta-oxide minerals in the Prašivá granitic pegmatites, Slovakia. I. Primary Fe, Ti-rich assemblage. The Canadian Mineralogist, 36, 525–534.Google Scholar
Wu, X., Qin, S. and Dubrovinsky, L. (2010) Structural characterization of the FeTiO3–MnTiO3 solid solution. Journal of Solid State Chemistry, 183, 2483–2489.CrossRefGoogle Scholar
Zaccarini, F., Garuti, G., Ortiz-Suarez, A. and Carugno-Duran, A. (2004) The paragenesis of pyrophanite from Sierra de Comechingones, Córdoba, Argentina. The Canadian Mineralogist, 42, 155–168.CrossRefGoogle Scholar