Caucasian-Arabian Segment of Alpine-Himalayan Convergence: An Example of Continental Collision Above Mantle Plume

Abstract

The Caucasian-Arabian segment of the huge Late Cenozoic Alpine-Himalayan orogenic belt marks a zone of the indentation of the Arabian plate into the Eurasian plate. The segment is formed by two tectonic domains: (1) the NW-SE-striking Greater Caucasus (GC) at the north, represents the southern margin of East European Craton, tectonically uplifted along the Main Caucasian Fault (MCF), and (2) Caucasian-Arabian Syntaxis (CAS) at the south; the latter includes arc-like tectonic domains of the Lesser Caucasus and Eastern Anatolia, vast thrust and folded belt between Eurasian and Arabian plates. A large NS-trending positive isostatic anomaly is characterized for CAS which suggests presence of a mantle plume head beneath it. The CAS is characterized by intense Neogene-Quaternary volcanism where two different types of magmatism occur: (1) extensive basaltic plateaus, possessing geochemical characteristics of plume-related rocks, and (2) calc-alkaline volcanics, which are typical for suprasubduction settings. However, according to seismic data, there is no subduction zone beneath the GC, but some north-directed seismic zones up to 50–70 km depth are occurred beneath the CAS which, probably, can generate calc-alkaline magmas. So, we suggest that “mixed” magmatism in Caucasian-Arabian convergence considered with existence here two independent magma sources: mantle plume and “embryonic” subduction zones.