Petrology and evolution of the Brezovica ultramafic massif, Serbia

The tectonomagmatic history of ultramafic rocks in the Brezovica massif (Serbia) involved two separate magmatic stages, as inferred from the mineral and bulk-rock chemistry data and thermal history of the peridotites. In the first stage, a suite of spinel harzburgites was formed during partial melting of the mantle and segregation of tholeiitic melts. During the second stage, these spinel harzburgites were repeatedly heated and affected by percolating melt. This process formed dunites and refractory spinel harzburgites during melt-harzburgite interaction, The melt that segregated from these rocks during the second magmatic stage was of high-Ca boninite affinity. Both magmatic stages occurred in a suprasubduction geodynamic setting at a relatively deep level (25-28 km). In its present position the Brezovica massif has been interpreted as a relic of a suprasubduction-type oceanic lithosphere derived from the Central Dinaridic-Mirdita ocean basin. During eastward emplacement of the Brezovica massif over the underlying olistostrome, the ultramafic rocks were cooled to temperatures around 735 +/- 20 degrees C.