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The University of Southampton
Ocean and Earth Science, National Oceanography Centre Southampton

Research project: Collisional magmatism

Currently Active: 
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The size and composition of the Earth’s continental crust is a balance between creative and destructive processes. Continental collisional zones are an important setting where new crust is created and preserved. We are carrying out a long-term study of the relative contributions of volcanic and plutonic rocks to the formation of new crust in western Anatolia.

The Aegean region lies along the western part of the Alpine-Himalayan orogenic belt, and marks the zone where the Tethyan oceans are being consumed by subduction, and following continental collision, crustal subduction and accretion occurred. This area is characterized by the presence of extensional domains in which magmatic activity generated, (1) widespread low- to high-K calc-alkaline and associated shoshonitic-ultrapotassic rocks with subduction-related geochemical affinity (orogenic magmas), which are mostly followed by, (2) Na-alkaline basaltic volcanic rocks with OIB-like intraplate affinity (anorogenic magmas) throughout the orogenic to post-orogenic phases. The geochemical characteristics of the orogenic magmas, such as high K and radiogenic Sr and high ratios of large ion lithophile elements (LILE) to high-field strength elements (HFSE), arise from multi-stage interaction of the mantle wedge with fluids/melts from subducted crustal sediments and subsequent crustal contamination processes. However, the details and origin of the crustal material, the type of metasomatism and the nature of the mantle sources remain debated. In oceanic and continental arcs, mantle metasomatism normally develops in response to chemical alteration of the mantle wedge by metasomatizing agents released from subducted oceanic crust and sediments. However, in the Alpine-Himalayan geodynamic setting, small oceanic branches were consumed by intra-oceanic subduction(s) and there were subsequent collisional events between small continental blocks (and arcs) that complicate these processes. Hence, it is suggested that the mantle domains were contaminated by fluid/melt components released from, (a) subducted oceanic assemblages and continentally-derived sediments and (b) crustal blocks or slivers subducted during collisional events.

We are investigating these processes through detailed geological fieldwork and geochemical analyses.

Total alkalis vs silica plot

Total alkalis vs silica plot for volcanic rocks form Western Anatolia.

Related research groups

Geochemistry

Key Publications

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