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Exsolution and hydration of pyroxenes from partially serpentinized harzburgites

Published online by Cambridge University Press:  05 July 2018

C. Viti ,
M. Mellini  and
C. Rumori
C. Viti*
Affiliation:
Dipartimento di Scienze della Terra, Università di Siena, Via Laterina 8, 53100 Siena, Italy
M. Mellini
Affiliation:
Dipartimento di Scienze della Terra, Università di Siena, Via Laterina 8, 53100 Siena, Italy
C. Rumori
Affiliation:
Dipartimento di Scienze della Terra, Università di Siena, Via Laterina 8, 53100 Siena, Italy
*
*E-mail: [email protected]
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Abstract

Ortho- and clinopyroxenes within partially-hydrated harzburgites from Elba and Val di Cecina (Italy) show lamellar exsolution textures and variable replacement by biopyriboles, talc-chlorite-serpentine mixed layers and serpentine. Chemical and geothermometric data suggest that the pyroxenes crystallized at 1240–1051°C, followed by subsolidus exsolution at slightly lower T (1145–1025°C for clinopyroxene lamellae + orthopyroxene matrix pairs and a 1033–982°C range for orthopyroxene lamellae + clinopyroxene matrix pairs).

Investigation by transmission electron microscopy of exsolved enstatite and augite reveals a multistage hydration process. The first stage (highest T, probably in the amphibole stability field) leads to the formation of biopyribole lamellae within exsolved augite, leaving the enstatite matrix unaffected. The second stage (~500–300°C) corresponds to the topotactic replacement of enstatite by layer silicates (talc + chlorite + serpentine, with (001)layer silicates parallel to (100)enstatite). Enstatite is also replaced by randomly oriented, poorly crystalline serpentine. The last hydration stage (<300°C) corresponds to the disappearence of augite and recrystallization of serpentine, leading to completely hydrated bastites with random lizardite lamellae, polygonal serpentine and minor chrysotile.

Keywords

ophioliteorthopyroxeneclinopyroxeneexsolutionserpentinizationbiopyriboles
Type
Research Article
Information
Mineralogical Magazine , Volume 69 , Issue 4 , August 2005 , pp. 491 - 507
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2005

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References

Anselmi, B., Mellini, M. and Viti, C. (2000) Chlorine in the Elba, Monti Livornesi and Murlo serpentinites: evidence for sea-water interaction. European Journal of Mineralogy, 12, 137—146.CrossRefGoogle Scholar
Baronnet, A. and Belluso, E. (2002) Microstructures of the silicates: key information about mineral reactions and a link with the Earth and material sciences. Mineralogical Magazine, 66, 709–732.CrossRefGoogle Scholar
Baronnet, A. and Boudier, F. (2001) Microstructural and microchemical aspects of serpentinization. In Eleventh Annual V. M. Goldschmidt Conference, abstract # 3382. LPI contribution N° 1088, Lunar and Planetary Institute, Houston (CD-ROM)Google Scholar
Baronnet, A. and Boudier, F. (2003) Processus de serpentinization paléo-oceanique de la harzburgite de l'Oman. Journées thématiques ‘Serpentines', Bulletin de Liaison S.F.M.C, 15, 3–4. 33–34.Google Scholar
Berndt, M.E., Allen, D.E. and Seyfried, W.E. Jr (1996) Reduction of CO2 during serpentinization of olivine at 300°C and 500 bar. Geology, 24, 351–354.2.3.CO;2>CrossRefGoogle Scholar
Brizi, E. and Mellini, M. (1992) Kinetical modelling of exsolution textures in igneous pyroxenes. Acta Vulcanologica, 2, 87–93.Google Scholar
Buseck, P.R. and Veblen, D.R. (1981) Defects in minerals as observed with high-resolution transmission electron microscopy. Bulletin de Mineralogie, 104, 249–260.CrossRefGoogle Scholar
Champness, P.E. and Lorimer, G.V. (1973) Precipitation (exsolution) in an orthopyroxene. Journal of Material Science, 8, 467–474.CrossRefGoogle Scholar
Champness, P.E. and Lorimer, G.V. (1974) A direct lattice-resolution study of precipitation (exsolution) in orthopyroxene. Philosophical Magazine, 30, 357–366.CrossRefGoogle Scholar
Cressey, B.A. (1979) Electron microscopy of serpentine textures. The Canadian Mineralogist, 17, 741–756.Google Scholar
Dungan, M.A. (1979) A microprobe study of antigorite and some serpentine polymorphs. The Canadian Mineralogist, 17, 771–784.Google Scholar
Eggleton, R.A. and Boland, J.N. (1982) Weathering of enstatite to talc through a sequence of transitional phases. Clays and Clay Minerals, 30, 1–20.CrossRefGoogle Scholar
Evans, B.W., Johannes, W., Oterdoom, H. and Trommsdorff, V. (1976) Stability of chrysotile and antigorite in the serpentine multisystem. Schweizerische Mineralogische und Petrographische Mitteilungen, 56, 79–93.Google Scholar
Ferraris, C., Folco, L. and Mellini, M. (2003) Sigmoidal exsolution by internal shear stress in pyroxenes from chondritic meteorites. Physics and Chemistry of Minerals, 30, 503–510.CrossRefGoogle Scholar
Feuer, H., Schröpfer, L. and Fuess, H. (1991) Microstructures and thermal behaviour of igneous pyroxenes. Pp. 105—125 in: Equilibrium and Kinetics in Contact Metamorphism (Voll, G., Töpel, J., Pattison, D.R.M. and Seifert, F., editors). Springer-Verlag, Heidelberg, GermanyCrossRefGoogle Scholar
Johannes, W. (1968) Experimental investigation of the reaction forsterite + H2O = serpentine + brucite. Contributions to Mineralogy and Petrology, 19, 309–315.CrossRefGoogle Scholar
Le Gleuher, M., Kenneth, I.T., Veblen, D.R., Noack, Y. and Amouric, M. (1990) Serpentinization of enstatite from Pernes, France: reaction microstructures and the role of system openness. American Mineralogist, 75, 813–821.Google Scholar
Lindsley, D.H. (1983) Pyroxene thermometry. American Mineralogist, 68, 477–493.Google Scholar
Martin, B. and Fyfe, W.S. (1970) Some experimental and theoretical observations on the kinetics of hydration reactions with particular reference to serpentinization. Chemical Geology, 6, 185–202.CrossRefGoogle Scholar
Mével, C. (2003) Serpentinization of abyssal peridotites at mid-ocean ridges. Comptes Rendu Géoscience, 335, 825–852.CrossRefGoogle Scholar
Michael, P.J. (1988) The concentration, behaviour and storage of H2O in the sub-oceanic upper-mantle: implications for mantle matasomatism. Geochimica et Cosmochimica Acta, 52, 555—566.CrossRefGoogle Scholar
Moore, K.T., Veblen, D.R. and Hove, J.M. (2001) Calcium segregation anthiphase boundary in pigeonite. American Mineralogist, 86, 1314–1318.CrossRefGoogle Scholar
Nakajima, Y. and Ribbe, P.H. (1981) Texture and structural interpretation of the alteration of pyroxene to order biopyriboles. Contributions to Mineralogy and Petrology, 78, 230–239.CrossRefGoogle Scholar
Nord, G.L. (1980) The composition, structure and stability of Guinier-Preston zones in lunar and terrestrial orthopyroxene. Physics and Chemistry of Minerals, 6, 109–120.CrossRefGoogle Scholar
Rampone, E., Bottazzi, P. and Ottolini, L. (1991) Complementary Ti and Zr anomalies in ortho-pyroxene and clinopyroxene from mantle peridotites. Nature, 354, 518–520.CrossRefGoogle Scholar
Rumori, C., Mellini, M. and Viti, C. (2004) Oriented, not-topotactic olivine → serpentine replacement in mesh-textured, serpentinized peridotites. European Journal of Mineralogy, 16, 731–741.CrossRefGoogle Scholar
Veblen, D.R. and Buseck, P.R. (1980) Microstructures and reaction mechanisms in biopyriboles. American Mineralogist, 65, 599–623.Google Scholar
Veblen, D.R. and Buseck, P.R. (1981) Hydrous pyriboles and sheet silicates in pyroxenes and uralites: intergrowth microstructures and reaction mechanisms. American Mineralogist, 66, 1107–1134.Google Scholar
Viti, C. and Mellini, M. (1998) Mesh textures and bastites in the Elba retrograde serpentinites. European Journal of Mineralogy, 10, 1341 — 1359.CrossRefGoogle Scholar
Wicks, F.J. (1986) Lizardite and its parent enstatite: a study by X-ray diffraction and transmission electron micro-scopy. The Canadian Mineralogist, 24, 775—788.Google Scholar
Wicks, FJ. and Whittaker, E.J. (1977) Serpentine textures and serpentinization. The Canadian Mineralogist, 15, 459–488.Google Scholar