GT4-1

Adakitic signature and its geotectonic significance for the volcanic and intrusive rocks where present (with special regard to the Southeast European Mountain belts - from Eastern Alps to westernmost Turkey)
Conveners: Jean-Francois Moyen, Herve Martin,  Anca Dobrescu,  Ioan Seghedi, Orhan Karsli

This session is a good occasion to continue the debate on adakites and rocks with adakitic signature. The geochemical characteristics of adakites (SiO2 ≥56 wt %, Al2O3 ≥15 wt %, high Na2O contents (3.5-7.5 wt.%), Mg# ~0.5, Sr >400 ppm, Y ≤18 ppm, Yb <1.9 ppm, Sr/Y ≥20, La/Yb >20 and 87Sr/86Sr <0.7045) have been exceptionally encountered, seeming to be strictly related to the slab melting model in which garnet plays the dominant role in high pressure conditions.
The adakitic signature (high Sr/Y and La/Yb ratios) is noticed in more volcanic and intrusive rocks of different geotectonic settings all over the world. These rocks can reflect a range of processes yielding high pressure melts of different sources in diverse situations like underplated mafic rocks (in continental arcs), delaminated crust (in collisional settings), etc.


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