REGIONAL METAMORPHISM OF THE DETRITIC ROCKS IN ORTAKÖY (AKSARAY) AREA

Yıl 2000, Cilt: 122 Sayı: 122, 31 - 39, 01.03.2000

Kerim Koçak

Öz

The detritic rocks of Ortaköy area were undergone a regional
metamorphism which caused development of the paragenesis: sillimanite +
plagioclase (An 0.43) +
orthoclase + quartz + biotite (Ann 0.08, Phl0.012) + garnet
(Alm 0.80-0.83, prP 0.10- 0.08 Sp 0.048-047 Grs 0.048-0.045).By geothermobarometers of garnet-biotite and
garnet-aliiminosilicate-quartz-plagioclase, the regional metamorphism
conditions were determined as P= 3.3±0,36 kb and T=~600°C. The garnet has
inverse mineralogical zoning due to homogenisation or exchange reaction between
garnet and matrix. Decreasing of grossulerite content in the garnet towards its
rim, and occurence of andalusite, chlorite and sericite show that P-T
conditions in Ortaköy area follows a clockwise path in P-T-t trajectory.

Anahtar Kelimeler

-

Kaynakça

• Aranovich, L.Y.A. and Podlesskii, K.K., 1980, The garnet- plagioclase barometer: Doklady, Earth Science Sections, 251, 101-103.
• Ataman, G., 1972, A study on the radiometric age of Cefalikdağ, one of the granite-granadiorite bodies outcropping on the south-east Ankara, Hacettepe Science and Engineering Journal, 2, 44-49 (in Turkish).
• Bayhan, H., 1990, Mineralogical, petrographic and geo- chemical study of the Ortaköy granitoid (east of Salt Lake) located within the 1st Turkish National Geotraverse, TÜBİTAK Project No, TBAG-841, 68pp (unpublished-in Turkish).
• Bhattacharya, A.; Mohanty, L.; Maji, A.; Sen, S.K., and Raith, M., 1992, Non-ideal mixing in the phlogo- pite-annite binary; constraints from experimental data on Mg-Fe partitioning and a reformulation of the biotite-garnet geothermometer: Contr. Min. Pet., 111,87-93.
• Bird. G.W. and Fawcett. J.J., 1973, Stability relations of Mg-chlorite-muscovite and quartz between 5 and 10 kb water pressure: J.Pet., 14. 415-425.
• Blackburn, W.H., 1969, Zoned and unzoned garnets from the Grenville gneiss around Gananoque, Ontario: Can. Min., 9, 691-698.
• Carmichael, D.M., 1969, On the mechanism of prograde metamorphic reactions in quartz-bearing pelitic rocks; Con.Min.Pet., 20, 244-267.
• Chinner. G.A., 1961, The origian of sillimanite in Glen Clova: Angus. J. Pet., 2. 213-23.
• Dasgupta, S.; Sengupta, P.; Guha, D. and Fukuoka, M., 1991, A refined garnet-biotite Fe-Mg exchange geothermometer and its application in amphibo- lites and granulites: Contr. Min. Pet., 109, 130- 137.
• Drop, G.T.R., 1987, A general equation for estimating Fe3+ concentrations in ferromagnesian silicates and oxides from microprobe analyses, using stoi- chiometric criteria: Min.Mag., 51, 431-450.
• Erkan, Y, 1975, Orta Anadolu Masifinin güneybatısında (Kırşehir bölgesinde) etkili rejyonal metamorfiz- manın petrolojik incelenmesi: HÜ. Yer Bilimleri Enst., Doçentlik Tezi. Ankara, 147 s., (unpub- lished).
• ,1976, Kırşehir çevresindeki rejyonal metamorfik bölgede saptanan izogradlar ve bunların petrolojik yorumlanmaları:Yer bilimleri, 2, 23-54.
• ,1977, Orta Anadolu masifinin güneybatısında (Kırşehir bölgesinde) etkili rejyonal metamorfizma ile amfibol minerallerinin bileşimi arasındaki ilişki-ler: Yer bilimleri, 3/1,41-46.
• Erkan, Y. and Ataman, G., 1981, Orta Anadolu masifinin (Kırşehir yöresi) metamorfizma yaşı üzerine K/Ar yöntemi ile bir inceleme: T.J.K. 35. Bilimsel ve Teknik Kurultayı bildiri özetleri, 33.
• Evans, B.W. and Guidotti, 1966, The sillimanite-potash feldspar isograd in western Maine: USA, Cont. Min.Pet., 12, 25-62.
• Ferry, J.M. and Spear, F.S., 1978, Experimental calibration of the partition of Fe and Mg between biotite and garnet: Contr. Min. Pet., 66: 113-117.
• Ghent, E.D., 1976, Plagioclase - garnet - AI2SiO5 - quartz: a potential geothermometer - geobarometer: Am.Min.,61, 710-714.
• Göncüoğlu, N.C., 1977, Geologie des weslichen Niğde- Massivs, PhD thesis, Rheinischen Friedrich- Wilhelms-Uni., Bon, 180. ; Toprak, G.M.K.; Kuşçu, I.; Erler, A. and Olgun E., 1991, Geology of the western part of the Central Anatolian Massif, Part 1: southern part, Middle Eeastern Technical University (METU) Turkish Petroleum Corporation (TPAO) project Report, 140 pp, (unpublished-in Turkish).
• Grant, J. and Weiblen, P.W., 1971, Retrograde zoning ingarnet near the second sillimanite isograd: Am.J.Sci., 270, 281-296.
• Guidotti, C.V. and Dyar, M.D., 1991, Ferric iron in meta- morphic biotite and its petrologic and crystallo- chemical implications: Am.Min., 76, 161-175.
• Güleç, N., 1993, Ağaçören granitoyidinden jeokronolojik bulgular: Hacettepe Üniversitesinde yer bilim- lerinin 25. Yıl sempozyumu, s. 49-50.
• Hodges K.V. and Spear, F.S., 1982, Geothermometry, geo- barometry and the AI2SiO5 triple point at Mt. Moosilauke, New Hampshire: Am.Min., 67, 1118-34.
• and Crowley, P.D., 1985, Error estimation and empirical geothermobarometry for pelitic systems: Am. Min., 70, 702-709.
• Holdaway, M.J., 1971, Stability of andalusite and the alu- minum silicate phase diagram, Am. J. Sci., 271, 97-131.
• and Mukhopadhway. B., 1993 a, A reevaluation of the stability relations of andalusite: Thermochemi- cal data and phase diagram for the aluminium sil- icates. Am.Min., 78, 298-315.
• and , 1993 b, Geothermobarometry in pelitic schists: A rapidly evolving field: Am.Min., 78, 681-693.
• Kerrick, D.M., 1987, Fibrolite in contact aureoles of Donegal, Ireland, Am.Min., 72, 240-254.
• Koçak, K., 1993, The petrology and geochemistry of the Ortaköy area, Central Turkey, PhD thesis, Glasgow Uni., Scotland, 280 (unpublished).
• and Leake, B.E., 1994, The petrology of the Ortaköy district and its ophiolite at the western edge of the Middle Anatolian Massif, Turkey, Jour. A. Earth Sciences, 18/2, 163-174.
• Kozial, A.M. and Newton, R.C., 1988, Redetermination of the garnet breakdown reaction and improvement of the plagioclase-garnet-AI2SiO5-quartz geo- barometer: Am.Min., 73, 216-23.
• Kertz, R., 1959, Chemical study of garnet, biotite and horn- blende from gneisses of Soutwestern Quebec, with emphasis on the distribution of elements in coexisting minerals, Journal of Geo., 67, 371-402.
• , 1964, Analysis of equilibrium in garnet-biotite-sil- limanite gneisses from Quebec, Journal of Pet., 5, 1-20.
• Loomis, T.P., 1975, Reaction zoning of garnet: Contr. Min. Pet., 52, 285-305.
• Newton, R.C. and Haselton, H.T., 1981, Thermodynamic calibration of the garnet-plagioclase-AI SiO - quartz geobarometer: Newton, R.C., Navrotsky, A. and Wood, B.J. (Ed), Thermodynamics of Minerals and melts, Springer-Varlag de, New York, 131-147.
• Perchuk, L.L. and Lavrent'eva, I.V., 1983, Experimental investigation of exchange equilibria in the system cordierite-garnet-biotite: Saxena, S.K. (Ed), Kinetics and equilibrium in mineral reactions: Advances in Physical Geochemistry, New York, Springer-Verlag de, 3, 199-239.
• Powell, R. and Holland, T.J.B., 1988, An internally consis- tent dataset with uncertainties and correlations: 3. Applications to geobarometry, worked examples and a computer program: J.Met.Geo., 6, 173-204.
• Reinhardt, J., 1992, Low pressure, high temperature meta- morphism in a compressional tectonic setting: Mary Kathleen Fold Belt, northeastern Australia, Geo.Mag., 129,41-57.
• Richardson, S.W.; Gillbert, M.C. and Bell, P.M., 1969, Experimental determination of kyanite-andalusite and andalusite-sillimanite equilibria: The alumini- um silicate triple point, Am.J.Sci., 267, 259-272.
• Seymen, i., 1981, Kaman (Kırşehir) dolayında Kırşehir masifinin stratigrafisi ve metamorfizmasi: TJK Bült., 24/2, 7-14.
• , 1984, Kırşehir masifi metamorfitlerinin jeolojik evrimi: T.J.K. Ketin Sempozyumu, 133-148.
• Thompson, A.B., 1976, Mineral reactions in pelitic rocks: I Prediction of P-T-X (Fe, Mg) phase relations, II Calculation of some P-T-X (Fe, Mg) phase rela- tions, Am.J.Sci., 276: 401-454.
• Tolluoğlu, A.Ü., 1986, Orta Anadolu masifinin güney- batısında (Kırşehir yöresinde) Petrografik ve petrotektonik incelemeler: H.Ü. Fen Bilimleri Enstitüsü, Doktora Tezi, Ankara, 237 s., 8 Ek. (unpublished).
• , 1987, Orta Anadolu masifi metamorfitlerinin (Kırşehir kuzeybatısı) petroğrafik özellikleri: Doğa Bilim, Derg., Müh. ve Çevre, 11/3, 344-361.
• Türeli, T.K., 1991, Geology, petrography and geochemistry of Ekecikdağ plutonic rocks (Aksaray region- Central Anatolia), PhD., Thesis, Middle Eastern Technical University, Ankara, 194p.
• Vielzeuf, D. and Bovine. P., 1984; An algorithm for the con- struction of petrogenetic grids-Application to some equilibria in granulitic paragneisses, Am.J.Sci., 284,760-791.
• Whitney, D.L. and Dilek, Y., 1997, Core complex develop- ment in central Anatolia: Geology 25, 1023-1026.
• and , 1998, Metamorphism during crustal thickening and extension in central Anatolia: the Niğde metamorphic core complex. Journal of trology 39, 1385-1403.