The Eastern Carpathians “ophiolites” (Romania): Remnants of a Triassic ocean

Abstract

Mesozoic ophiolitic and related rocks in the Eastern Carpathians occur in three areas, from north to south: Rarău, Hăghimaş and Perşani Mts. They are found as blocks ranging from few metres to a few kilometers in size and as centimetre-sized in breccias, most likely embedded in the Late Barremian–Early Albian Wildflysch formation. Compositionally, they range from lherzolites and harzburgites to mafics such as FeTi gabbros, dolerites, basalts, and to andesites. The volcanics comprise highly-depleted basalts/andesites to enriched-type mid-ocean ridge basalts; additionally they include ocean island basalts and calc-alkaline basalts/andesites and trachytes. Based on paleontological evidence, their age is Middle to ?Late Triassic. They can be clearly compared with remnants of the Meliata–Hallstatt Ocean in the Western Carpathians, but do not match the Jurassic ophiolites and island arc volcanics in the Mureş Zone of the Southern Apuseni Mts. We propose a Triassic ocean connected with the Meliata–Hallstatt Ocean, between (a) the Bucovinian/Sub-Bucovinian continental crust, (b) the Infrabucovinian and finally (c) the Northern Apuseni microcontinents. This ocean closed in the Late Triassic to Early Jurassic causing close juxtaposition of all three microcontinents. An ophiolite complex together with ocean island basalts and calc-alkaline basalts/andesites remained from this ocean and was subsequently eroded and transported as blocks of different size into the Lower Cretaceous Wildflysch basin, together with blocks and clasts of limestones similar to the Mesozoic sedimentary sequences in the Northern Apuseni realm. The Wildflysch formation was thrust as an independent unit during the Albian over the Bucovinian Nappe in the Eastern Carpathians and the Northern Apuseni continental crust, respectively.