Metamorphic sole in the northernmost part of the Vardar Zone Western Branch (Village Tejići, Mt. Povlen, Western Serbia)

The geodynamic evolution of the Mesozoic ophiolites within Dinarides and Vardar zone is of special scientific interest. According to the available data these two ophiolites show both similarities and differences especially in their age, mineralogy and composition, including weakly- or well-developed metamorphic sole at their base. Ophiolites in the Tejići village consist a minor part of the Tethyan (Mediterranean) ophiolites situated in the northernmost part of the Vardar Zone Western Branch - a relic of the marginal basin but since Middle Jurassic a large oceanic realm which existed from the Upper Triassic to the Upper Cretaceous (Maastrichtian), i.e. the most important oceanic area of the Alpine-Mediterranean region after the closing of the main Vardar Ocean. It comprises ultramafic rocks (harzburgites and subordinated lherzolites) with typical tectonite fabric, gabbros, diabases, pillow lavas together with volcanic breccias and subordinated tuffaceous sediments that were tectonically emplaced to their present position during the late Upper Jurassic. The ophiolites itself are tectonically overlain by the Upper Cretaceous limestones. High-grade metamorphic rocks (amphibolite ± garnet and epidote-bearing amphibolite) occur at the base of the ophiolite sequence and are followed by medium- to low-grade metamorphic rocks represented either with blocks of augen gneisses or outcrops of garnet micaschist, chlorite micaschists and biotite (±chlorite)-epidote (±calcite) schists and subordinate calcshists and phyllites. Average P–T conditions of 630-680 °C and ca. 6±1.5 kbar were obtained for amphibolites and about 435-550 °C and 4.5 ±0.5 kbar for micaschist. In general, these rocks are characterized by greenschist to amphibolite facies mineral assemblages. Their protolith are basic igneous rocks, their volcanoclastic and rarely sedimentary (clastic) rocks. All mafic metamorphic rocks display moderate enrichment in light REE that could be ascribed to pre-metamorphic basalt-seawater interaction. The presence of metaclastic rocks probably indicates the site of emplacement close to a major landmass, which is in agreement with amygdales in pillow basalts and the absence of deep water sediments. Bulk-rock chemistry of the amphibolites and other primary basic rocks show two different geochemical affinities: tholeiitic (Nb/Y=0.07–0.18), and alkaline (Nb/Y=1.77–3.48). REE patterns and trace element discrimination diagrams suggest that possible protoliths for the first were tholeiitic island arc basalts and for the second group within-plate alkali basalts. The metamorphic rocks were formed between 160-150 Ma ago when their protoliths were overthrusted by hot ultramafic slab reflecting the time of the beginning of compression i.e. closing stages of the ocean basin. The age of these metamorphic sole rocks is very close to the age obtained for the sole rocks in Zlatibor (Dinaride Ophiolite belt), the amphibolites at the Rogozna Mt. (Western Vardar ophiolite belt), as well as with the Ar/Ar ages obtained for the Albanian amphibolite soles (165-175 Ma) and slightly younger than the sole rocks in Brezovica (over 170 Ma).