Origin of vehrlitic intrusions in the Ispendere (Malatya) and Kömürhan (Elazığ) ophiolitic complex (Eastern Taurus-Turkey)

İspendere ve Kömürhan Ofiyolitik Kompleksleri ideal bir ofiyolitik istifin kabuk kesimini gösterirler. Bunlar tabana ait platonik birim, üstte izotrop gabrolar, dayk kompleksi ve volkanik birimlerden oluşur. Bu birimler, ofiyolitin kabuk kesimini oluştururlar. Tekil diyabaz daykları bütün bu birimleri keserler. Ofiyolitler, güneye doğru Orta Eosen yaşlı Maden Kompleksi üzerine tektonik olarak gelir ve kuzeyde Üst Kretase Magmatitleri tarafından genellikle tektonik olarak üzerlenirken, bazı yerlerde Kömürhan ofiyoliti ile Üst Kretase yaşlı Elazığ Magmatitleri arasında dereceli bir geçiş izlenmektedir. İspendere ve Kömürhan ofiyolitlerinin kabuk kesimlerinin incelenmesinde gabrolar içerisinde verlitik intrüzyonların varlığı gözlenmektedir. Büyük verlit intrüzyonlan ve çok sayıda verlitik siller ile dayklar gabroları keserler. İntrüzyonlar tabanda plajiyoklas içermeyen verliterden oluşmuştur. Üstte desimetre ile metre arası bir kalınlığa sahip verlit ve birkaç on metre üzerinde klinopiroksenit tabakakalarına dereceli geçişlidirler. Üste doğru İntrüzyonlar plajiyoklaslı verlit ve melanokratik gabrolara geçerler. İntrüzyonlar ve gabrolar arasındaki kontaklarda herhangi bir metamorfizma izi yoktur. Verlitik intrüzyonların iç yapısı esas olarak izotrop olup, tabakalanma göstermemektedirler. İspendere ve Kömürhan Ofiyolitlerindeki verlitik intrüzyonların petrolojik modeli, arazi ve petrografik veriler esasına dayanır. Esas ofiyolitik istifi veren okyanusal büyüme fazından sonra, ikinci evrede meydana gelen ergime verlitik intrüzyon, dayk ve sil olarak katılaşan magmayı vermektedir. Bu ikinci magmatik olay, okyanus içi dilimlenmeden hemen sonra, Üst Kretase sırasındaki yerleşme öncesi meydana gelmiştir.

İspendere (Malatya) ve Kömürhan (Elazığ) ofiyolitik komplekslerindeki (Doğu Toros-Türkiye) verlitik intrüzyonların kökeni

The Ispendere and Kömürhan Ophiolitic Complex exhibit the crustal section of an ideal ophiolitic sequence. They are composed of a basal plutonic unit, the high-level Isotropie gabbros, a dike complex and volcanic units which constitute a classical ophiolitic crustal section. The isolated diabase dikes cut all these units. They thrust towards south onto the Middle Eocene Maden Complex. The Ophiolite are thrusted by the Upper Cretaceous magmatics in the north, however, there is a gradual transition between the Kömürhan ophiolite and the Upper Cretaceous Elazığ Magmatics in some places. An important discovery in the study of the crustal section in the Ispendere and Kömürhan Ophiolite has been that of wehrlitic intrusions into the gabbros. The huge wehrlite intrusions and numerous wehrlitic sills and dikes intrude the layered and the Isotropie gabbros. The intrusions are composed of plagioclase-free wehrlites at the base. The top of the intrusions grade into a layered sequences of decimeter-to meter-thick wehrlite and clinopyroxenite layers over several ten of meters. Upward, the intrusions are followed by plagioclase wehrlite and melanocratic gabbros. The contacts between intrusions and host gabbros are lobate evoking viscous tongues. The internal structure of wehrlitic intrusions is mainly Isotropie and non-layered. A petrological model of the wehrlitic intrusions in the Ispendere and Kömürhan Ophiolite is proposed on the basis of field and petrographical data. After the oceanic accretion phase that gave rise to the main ophiolitic sequence, a second stage melting is suggested to explain the genesis of the magma which has been consolidated as wehrlitic intrusion, dikes and sills. This second magmatic episode postdates the intraoceanic detachment and took place during Upper Cretaceous times, just before abduction.

___

Aktaş G. and Robertson A.H.F., 1990. Tectonic evolution of the Tethys suture zone in S.E. Turken: Evidence from the petrology and geochemistry of Late Cretaceous ans Middle Eocene extrusives. In. Symp. On ophiolite genesis and evolution of oceanic lithosphere, Geol. Soc, London, Special Publ., 311-328.
Benn K. and Laurent R., 1987. Intrusive suite documented in the Troodos ophiolite plutonic complex, Cyprus. Geology, 15: 821-824.
Benn K., Nicolas A. and Reuber I., 1988. Mantle-crust transition zone and origin of wehrlitic magmas: Evidence from the Oman ophiolite: Tectonophysics, v.151, 75-85.
Beyarslan M., 1996. Kömürhan Ofiyolit Birimi'nin Petrografik ve Petrolojik İncelenmesi. F.Ü. Fen Blimleri Enst. Doktora Tezi (yayımlanmamış). 103pp.
Beyarslan M., 1991.1 spendere (Kale -Malatya) Ofiyolitler'nin Petrografik Özellikleri : F.Ü. Fen Bilimleri Enst. Yüksek Lisans Tezi (yayımlanmamış), 57 pp.
Beyarslan M. and Bingöl A.F., 2000. Petrology of a supra- subduction zone ophiolite (Kömürhan-Elazığ-TURKEY). Canadian Journal of Earth Sciences. Canada. 37:1411-1424.
Bingöl A.F., 1986. Petrographic and petrologique characteristics of the Guleman ophiolite (Eastern Taurus-Turken). Geosound, 13114, 41-57.
Boudier F. and Coleman R.G., 1981. Cross section through the peridotite in the Semail ophiolite, southeastern Oman mountains. J. Geophys. Res., 86: 2573-,2592.
Boudier F.,Bouchez J.L., Nicolas A., Cannat M., Ceuleneer G., Misseri M. and Montigny R., 1985. Kinematics of oceanic thrusting in the oman ophiolite: model of plate convergence. Earth Planet. Sci. Lett., 75:215-222.
Boudier F., Ceuleneer G., and Nicolas A., 1988. Shear zones, thrusts and related magmatism in the Oman ophiolite: Initiation of thrusting on an oceanic ridge: Tectonophysics, v.151,275-296.
Dahl R., Juteau T., Boudier F., Nicolas A., Bouchez J.L. and Crambert S., 1983. Ophiolite des nappes de Semail (Oman): nouvelles donnes de terrain sur les parties plutoniques superieures des massifs de Rustaq etide Nakhl. Sci. Geol. Soc. Bull., Strasb., 36:35-59.
Dilek Y., Moores E.M. and Ramsden T.W., 1990. Tectonic evolution of the Troodos ophiolite within the Tethyan framework. Tectonics, 9: 811-823.
Dilek Y., Thy P., Moores E.M., Delaloye M. and Karson J.W., 1991. A magmatic extension and tectonic denudation in the Kızıldag Ophiolite, South Turkey: Implications for the evolution of Neotethyan oceanic crust. In: T.J. Peters et al. (Editors) Ophiolite. Ophiolite Genesis and the Evolution of Oceanic Lithosphere, Kluwer, Dordrecht, pp. 458-500.
Ernewein M. and Whitechurch H., 1986. Les intrusions ultrabasiques de la sequence crustale de I'ophiolite d'Oman: un evenement temoin de V extinction d' une zone d'accretion oceanique? C.R. Acad. Sci. Paris, Ser. 2, 303:379-384.
Ernewein M., Pflumio C, and Whitechurch H., 1988. The death of an accretion zone as evidenced by the magmatic history of the Sumail ophiolite (Oman): Tectonophysics, v 151,247-274.
Juteau T., Beurrier M., Dahi R., and Nehlig P., 1988. Segmentation at a fossil spreading axis: The plutonic sequence of the Wadi Haymiliyah area (Haylayn Block, Sumail Nappe, Oman): Tectonophysics, Vİ51,167-197.
Lytwyn J.N. and Casey J.F., 1993. The geochemistry and petrogenesis of volcanics and sheeted dikes from the Hatay (Kızıldağ) ophiolite, Southern Turken: Possible formation with the Troodos ophiolite, Cyprus, along fore-arc spreading centers: Tectonophysics, v.223, 237-272.
Nicolas A.,1989. Structures of Ophiolite and dynamics of oceanic lithosphere : Dordrect, Netherlands, Kluwer, 367pp.
Pallister J.S. and Hopson C.A., 1981. Samail ophiolite plutonic suite: field relations, phase variation, cryptic variation and layering, and a model of a spreading ridge magma chamber. J. Geophys. Res., 86:2593-2644.
Pearce J.A., Lippard S.J. And Roberts S., 1984. Characteristics and tectonics significance of supra-sub auction zone ophiolites. Geol. Soc. London, Special Publication, 16, 77-94.
Penrose Conference Participants, 1972. Ophiolites. Geotimes, 17,24-25.
Rabinowicz M., Ceuleneer G. and Nicolas A., 1987. Melt segregation and flow in mantle diapirs below spreading centers: evidence from the Oman ophiolite. J. Geophys. Res., 92: 3475-3486.
Robertson A.H.F., 1994. Role of the tectonic fades concept in orogenic analysis and its application to Tethys in the Eastern Mediterranean Region. Earth Science Reviews 37,139-213.
Robertson A.H.F., 1998. 54. Mesozoic-Tertiary Tectonic Evolution of The Easternmost Mediteranean Area: Integration of Marine and Land Evidence. Proceedings of the Ocean Drilling Program, Scientific Results, Vol. 160. 723-782.
Yazgan E., 1983. A geotraverse between the Arabian platforme and the Munzur nappes. Int. Symp. on he Geology of the Taurus Belt, Ankara. Field Guide Book, Excursion V.