WESTERN EXTENSION OF THE SEVAN-AKERA SUTURE ZONE (ERZINCAN-ERZURUM REGION, TURKEY): COMPARISION OF NEW DATA CONCERNING ORIGIN, STRUCTURE AND TECTONIC EVOLUTION BETWEEN SEVAN-AKERA AND ERZINCAN SUTURE ZONES
Résumé
In order to better understand the tectonic evolution of the Sevan-Akera suture zone, particularly its connection westward into the Ankara-Erzincan suture, field observations and sampling were carried out on the Erzincan suture zone (near Erzincan). The goal of this study is to solve the problem of linking both odbucted ophiolitic domains. As in Armenia, the structures in Turkey are complex and have been reworked and reactivated because of post-obduction collision stages. Still, field investigations have been able to evidence that (1) ophiolites are thursted above the margin of the Taurides to the SE, near Hınıs. Futhermore, (2) these ophiolites overthrust a lowgrade metamorphic unit characterized by volcanites, volcanoclastics and reef limestones, in the Erzincan area. In addition, (3) these ophiolites are overthrusted by the Pontides margin which imply a suture zone farther north of the Erzincan and Akale areas. Ordinarily, the Erzincan suture zone is placed between the metamorphic unit and the Taurides platform, characterized by a tectonic mélange containing blocks of oceanic crust which may include some eclogite slices (observed by G. Topuz). We believe that the metamorphic unit could originate from an island arc setting. These observations illustrate a similar context to that which has been observed in Armenia limited to the North by the Sevan-Akera suture, specifically from north to south: (1) The ophiolites were underthrusted below the Pontides margin, (2) the ophiolite body is found overthrusting a metamorphic unit potentially derived from an intra-oceanic arc and (3) the ophiolites were thrusted to the south upon the Taurides continental domain. The question of having a single obducted ophiolite body in the three places is posed. In addition, the study of the Erzincan suture brings new insights on the possibility of the presence of an expected intra-oceanic island arc under the obducted ophiolite domain.
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