Cenozoic crustal evolution and mantle dynamics of post-collisional magmatism in western Anatolia


Dilek Y., Altunkaynak S.

INTERNATIONAL GEOLOGY REVIEW, cilt.49, ss.431-453, 2007 (SCI İndekslerine Giren Dergi) identifier identifier

  • Cilt numarası: 49 Konu: 5
  • Basım Tarihi: 2007
  • Doi Numarası: 10.2747/0020-6814.49.5.431
  • Dergi Adı: INTERNATIONAL GEOLOGY REVIEW
  • Sayfa Sayıları: ss.431-453

Özet

Post-collisional magmatism in western Anatolia followed a continental collision event in the Early Eocene, and occurred in discrete pulses that appear to have propagated from north to south over Lime. The first episode occurred during the Eocene and Oligo-Miocene and was subalkaline in nature, producing medium- to high-K cale-alkaline granitoids and mafic to felsic volcanic rocks. Partial melting and assimilation-fractional crystallization of enriched subcontinental lithospheric mantle-derived magma(s) were important processes in the genesis and evolution of the parental magmas, which experienced decreasing subduction influence and increasing crustal contamination through the Early Eocene-Early Miocene. This magmatic episode coincided with continued regional compression and development of a thick orogenic crust, and was influenced by an influx of asthenospheric heat and melts provided by lithospheric slab break-off. Extensional tectonics replaced the regional compression by the Middle Miocene, following the initial collapse of the western Anatolian orogenic welt, and resulted in the development of metamorphic core complexes and horst-graben structures. The second main episode of magmatism occurred during the Middle Miocene (16-14 Ma) and produced mildly alkaline rocks that show a decreasing amount of crustal contamination and subduction influence through time. Although melting of a subdue[ ion-modified lithospheric mantle continued, an asthenospherie mantle-derived melt contribution played a major role in the generation of these mildly alkaline magmas. The inferred asthenospheric melt contribution was a result of delamination of the lowermost part of the lithospheric mantle and/or partial convective removal of the sub-continental lithospheric mantle (SCLM). The third episode of post-collisional magmatism started around similar to 12 Ma and continued through the Late Quaternary. The main melt source for this phase carried no subduction component and was generated by the decompressional melting of asthenospheric mantle, which flowed in beneath the attenuated continental lithosphere in the Aegean extensional province. Lithospheric-seale extensional fault systems acted as natural conduits for the transport of uncontaminated alkaline magmas to the surface. Post-collisional magmatism in western Anatolia thus displays compositionally distinct episodes controlled by slab break-off, lithospheric delamination, and asthenospheric upwelling and decompressional melting, reflecting the geodynamic evolution of the eastern Mediterranean region throughout the Cenozoic. These events and ihe associated processes in the mantle took place primarily in response to the plate tectonic evolution of the region and collectively constitute a time-progressive template for the mode and nature of the post-collisional magmatism common to most alpine-style orogenic belts.