(ca. 180 Ma) up to the Lower Cretaceous (ca. 120 Ma). During its opening stage, through a spreading process, an ocean floor trondhjemitic rock-series, consisting of granophyres, plagiogranites and plagiaplites, associated with tonalites and quartz-diorites, was formed. These rocks form parallel dykes in a sheeted dyke complex and occur as dykes cutting the gabbro bodies. The closing of the ocean was determined by a bilateral subduction process acting along an Andean-type and a Mariana-type subduction planes. Within the Mariana-type subduction trench, extending from Drocea to the Trascău Mountains, island arc bimodal volcanism manifested itself, engendering a second trondhjemitic rock-series, represented by quartz-keratophyres, rhyolites, dacites and trachytes. The common geochemical features of the two different sources of the trondhjemitic rock-series consist in their high contents of SiO₂ and Na₂O, and low contents of K₂O, CaO and MgO.
Copyright © 2011 Published by Ed. Univ. „Al. I. Cuza” Iași. All rights reserved.

Mureş Ocean, ocean floor trondhjemites, island arc trondhjemites, geochemistry