LATE PROTEROZOIC-EARLY CAMBRIAN TERRANES IN THE BASEMENT OF MOESIA AND SURROUNDING ALPINE BELTS

Geological, geochronological and geochemical evidence suggest that several distinct parts of the Neoproterozoic orogen developed at the active margin of Gondwana are preserved in the basement of the Alpine fold belts of the South Carpathians and the Balkans and in the Moesian block they surround. They represent remnants of a Pan-African (Cadomian) volcanic arc and its marginal backarc basin. A segment of a Neoproterozoic foreland basin is preserved along the northern margin of Moesia.

Remnants of an Cadomian ophiolite complex exposed in the basement of the Danubian Nappes from South Carpathians show a more complete ophiolitic stratigraphy in the Tisovita-Iuti complex (South Banat, Romania) and Deli Iovan Massif (Serbia), where upper mantle, cumulate and upper plutonic and effusive sections are preserved. Their mineralogical and chemical characters resemble ophiolite complexes generated in ocean basins associated with arc systems formed at fast- to intermediate-spreading centres. In the Tcherny Vrach massif (Bulgaria) only cumulate, sheeted dykes and pillow lava units are recognized.

The basement of the Alpine Danubian Nappes in the South Carpathians is made of two types of terranes. The dominantly metabasitic suite (Dragsan type terranes) represents Pan-African island arc metavolcanics. Late accretion of these oceanic rocks to a continent is marked by emplacement of late-kinematic high K calc-alkaline granitoids, while the amphibolite facies metamorphism occurred consequently to subduction of the arc complex. The metasedimentary successions (Lainici-Paius type terranes), with HT-LP regional metamorphism, are intruded by a Neoproterozoic calc-alkaline and alkali-calcic plutons.

Midfan and distal turbidites of the Neoproterozoic-Early Cambrian Histria Formation, exposed in an tectonic block of Moesia, accumulated in the inner part of a foreland basin floored by continental crust. Located north of a northward vergent Neoproterozoic thrust wedge, the basin was sourced by a southerly located continental margin dominated by active volcanic arcs. The southerly located active continental margin was probably the northern coast of Gondwana and its volcanic arc.