Mineral Phases in the Edige Ophiolite Body

Yıl 1990, Cilt: 110 Sayı: 110, 61 - 75, 01.03.1990

Ayla Tankut Naci M. Sayın

Öz

Ediğe ophiolite body contains upper mantle and a part of crustal sequences, as a remnant of an oceanic lithosphere
slice. The upper mantle sequence is composed of the primary assemblages of: olivin+ orthopyroxene + clinopyroxene + chromium
spinel, in the tectonite ultramafics;and olivine + clinopyroxene + orthopyroxene in the cumulate ultramafics. The crustal sequence
is characterized by the phases of: Plagioclase + clinopyroxene + olivin + orthopyroxene. Amphibole + serpentine + chlorite +
prehnite + pumpellyite + sphene are the common secondary phases. The pyroxenes of the cumulate rocks are characterized by
high Mg and very low contents of Na,K and Al. The plagioclase composition in the lovver level gabbros range from An40 to An90
The amount of amphibole development and albitization increase with stratigraphic height that, in the upper level gabbros the
pyroxenes are almost completely replaced by amphibole and all the plagioclases are albite. Chromites of the tectonites are of podiform
type. All the evidences suggest that the mineral assemblages in various rock types of the Ediğe ophiolite body are similar
to the corresponding rocks of the oceanic lithosphere. Minerals of the cumulates suggest direct crystallization from spreading
ridge magma. They have undergone metamorphic reconstitution correlated with ocean floor metamorphism.

Anahtar Kelimeler

-

Kaynakça

• Burns, L.E., 1985, The border Ranges ultramafic and mafic complex, southcentral Alaska : cumulate fractionates of island-arc volcanics: Can. J. Earth Sci., 22, 1020-1038.
• Coleman, R.G., 1977, Ophiolites : ancient oceanic lithosphere? : Springer-Verlag, 229, New York, Ny.
• Deer, W.A.; Hovie, R.A. and Zussman, J., 1963, Rock forming minerals : Longmans Press, 5 vol., London.
• Dickey, J. SJr., 1975, A hypothesis of origin for podiform chromite deposits : Geochim. Cosmochim. Acta, 39, 1061-1074.
• Elton, D. and Scarfe, C.M., 1983, Highpressure phase equilibria of a high-magnesia basalt and the genesis of primary oceanic basalts : Am.Mineral.
• — ; Casey, D.F. and Komor, S., 1984, Cryptic mineral-chemistry variations in a detailed traverse through the cumulate ultramafic rocks of the North Arm Mountain massif of the Bay of Islands ophiolite, New foundlend : Gass, I.G., Lippard, S.J. and Shelton, A.W., eds., Ophiolites and oceanic lithosphere, 83-97, London.
• Hopson, C.A.; Coleman, R.G.; Gregory, R.T., Pallister, J.S. and Bailey, E.H., 1981, Geologic section through the Semail ophiolite and associated rocks along a Muscat-ibra transect, southeastern Oman Mountains: J. Geophys. Res. 86, 2527-2544.
• Malpas, J. and Langdon, G., 1984, Petrology of the Upper Pillow Lava suite, Troodos ophiolite, Cyprus : Gass, I.G., Lippard, SJ. and Shelton, A.W., eds., Ophiolites and oceanic lithosphere, 155-167, London.
• Poldervaart, A. and Hess, H.H., 1951, Pyroxenes in the crystallization of basaltic magma: Jour. Geol., 59, 472-489.
• Prinz, M.; Keil, K.; Green, J.A.; Bonatti, E. and Honnorez, J., 1976, Ultramafic and mafic dredge samples from the equatorial mid-Atlantic ridge and fracture zones : Journal of Geophysical Research, 81, 4087-4103.
• Stakes, D.S.; Taylor, H.P., Jr and Fisher, R.L., 1985, Oxygenisotope and geochemical characterization of hydrothermal alteration in ophiolite complexes and modern oceanic crust : Gass, I.G., Lippard, SJ. and Shelton, A.W., eds., Ophiolites and oceanic lithosphere, 199-213, London.
• Stevens, R.E., 1944, Composition of some chromites of the western Hemisphere : Am.Miner., 29, 1-34.
• Tankut, A.T.and Gorton,M.P.,(in press),Geochemistry of a mafic-ultramafic body in the Ankara melange, Anatolia, Turkey : Evidences for a fragment of oceanic lithosphere Moores, E., ed., Proc.Symposium, Troodos 87, Ophiolites and oceanic lithosphere ,
• and Saym.M.N., 1989, Edige ultramafik kütlesi: Turkish Journal of Engineering and Environmental Sciences; 13/2,229-244.
• Thayer, T.P., 1964, Principal Features and origin of podiform chromite deposits and some observations on the Guleman-Soridag District, Turkey : Econ.Geol., 59-8, 1497-1524.
• Thy, P., 1987, Petrogenic implications of mineral crystallization trends of Troodos cumulates, Cyprus: Geol.Mag., 124 (1), 1-11.