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Spatial and temporal variation in Late Cenozoic back-arc volcanic rocks, Aegean Sea region

Publication Date
DOI: 10.1016/0040-1951(89)90186-8
  • Chemistry
  • Earth Science


Abstract The Aegean Sea and adjacent areas comprise thinned continental crust forming an extensional back-arc basin behind the South Aegean Arc. In this back-arc region are many small volcanic centres, with a wide range of volcanic products. This Late Miocene to Quaternary volcanism is volumetrically minor, in contrast to the voluminous igneous activity of the South Aegean Arc. The age and major and trace element geochemistry of these back-arc volcanic rocks are reviewed from the literature: where necessary, new geochemical analysis have been made. Five magma types are recognised: continental alkaline basalts; sodic basalts with incompatible element enrichment and Nb depletion; trachytes; shoshonites; and calc-alkaline andesites. All but the continental alkaline basalts appear geochemically related to subduction processes. There is a regular distribution of rock types in time and space: the subduction-related rocks occur in a broad arc between the modern South Aegean Arc and the Early to Middle Miocene volcanicity of the central Aegean region. Sodic basalts occur in the most inboard regions, and are later than the trachytes. Shoshonites and calc-alkaline magmas occur in the most outboard regions. This back-arc volcanism occurs only in areas of abundant shallow seismicity. However, areas of extension and seismicity in the northeast Aegean, distant from the subducting slab, lack volcanoes. With the exception of the continental alkaline basalts, the magmas are derived only from mantle influenced by the aseismic part of the Hellenic subduction slab between 200 and 400 km depth. Back-arc extension, associated with rotation of the Aegean microplate and strike-slip motion on the North Anatolian Fault system, has created a fault system allowing these magmas to reach the surface. Analogous processes may be common in the final stages of closure of ancient orogens.

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