ANTARCTIC PENINSULA CONTINENTAL MAGNESIAN ANDESITES - INDICATORS OF RIDGE TRENCH INTERACTION DURING GONDWANA BREAK-UP

Subduction of young, hot oceanic lithosphere and a major episode of lithospheric extension have been considered as key tectonomagmatic factors in the genesis of 'Setouchi-type' continental magnesian andesites. We present data on a new discovery of such andesites from the northern part of the Antarctic Peninsula and propose that subduction of newly created oceanic lithosphere occurred along the proto-Pacific margin of Antarctica during the Middle Jurassic. Continental magnesian andesite magmatism was contemporaneous with the early stages of Gondwana break-up and we suggest that subduction of young, hot oceanic lithosphere and ridge-trench interaction may have contributed to the disintegration of Gondwana by thermally weakening the lithosphere and developing a broad, linear extensional zone along the proto-Pacific margin.