The Maden Complex, SE Turkey: evolution of a Neotethyan active margin

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Abstract
Summary: In this paper we describe and interpret a critical segment of a Tethyan suture zone in SE Turkey dominated by a major nappe pile which, from the structural top downwards, consists of the following units: first, the Elazıǧ-Palu nappe , a major Upper Cretaceous volcanic arc complex and cover related to subduction of a southern strand of the Mesozoic Tethys. The arc rocks are regionally underlain by metamorphic rocks of the Bitlis-Pütürge nappe, but in the area studied this is absent and the next unit is the Hazar-Guleman nappe , which consists of a sliced ophiolitic assemblage of presumed Upper Cretaceous age unconformably overlain by a relatively undeformed succession of Palaeogene red beds (Ceffan Formation), flysch (Simaki Formation) and both pelagic and redeposited neritic limestones (Gehroz Formation). This nappe is cut by the South Anatolian transform fault . Below it the Kıllan Imbricate Unit consists of imbricated Upper Cretaceous ophiolitic and other mafic extrusives (Killan Group) associated with, and locally unconformably overlain by, Palaeocene and Eocene rocks ranging from deep sea sediments to sedimentary melange and detached blocks, with minor volcanics. Towards the sole-thrust the Killan Imbricate Unit is mostly tectonic melange. Below, are the autochthonous and para-autochthonous successions of the Arabian foreland , including ophiolitic olistostrome of latest Cretaceous age (Koçali Complex). Our Hazar-Guleman nappe and the Killan Imbricate Unit together constitute the Maden Complex . We also report on a distinctive assemblage of Middle Eocene mafic extrusives and interbedded deep water sediments further east along the suture zone ( Karadere Formation ), and briefly summarise implications for economic sulphide mineralization in the area. We interpret the suture zone in terms of formation of a Mesozoic ocean basin followed by northward subduction. The Karadere Formation further east would in one possible model have formed by rifting of the fore-arc, possibly related to oblique convergence in the Middle Eocene. In an alternative model the Neo-Tethys had essentially closed by the latest Cretaceous facilitating ophiolite emplacement over both the northern active margin and the former passive southern margin. In this case the Killan Imbricate Unit would be related to tightening of the suture and the Karadere Formation to renewed rifting controlled by strike-slip faulting. In both models continental collision was well advanced by the Miocene with flysch and sedimentary melange deposition (Lice and Çüngüş Formations), followed by translation along the South Anatolian transform fault.