| Title | OLIVINE WEBSTERITE VEINS CUTTING THE RABROVO SERPENTINITES (SOUTH MACEDONIA): NEW EVIDENCE OF THE ARC SETTING OF THE EAST VARDAR OPHIOLITES? |
| Author/s | Blažo Boev, Dejan Prelević, Milica Božović, Suzana Erić, Vladica Cvetković |
| Citation | B. Boev, D. Prelević, M. Božović, S. Erić, V. Cvetković, "OLIVINE WEBSTERITE VEINS CUTTING THE RABROVO SERPENTINITES (SOUTH MACEDONIA): NEW EVIDENCE OF THE ARC SETTING OF THE EAST VARDAR OPHIOLITES?", Contributions, Sec. Nat. Math. Biotech. Sci., MASA, ISSN 1857-9027, Vol. 34, no.1-2, 2013, pp.69-81. |
| Abstract | The study reports petrography and mineral chemistry data about an ultramafic vein that cuts the Rabrovo serpentinite (near Valandovo, Southern Macedonia). The serpentinite occurs as a block within a shearing zone of the East Vardar Zone tectonic mélange. The vein corresponds to medium-grained olivine websterite that sometimes displays cumulate-like textures. It is composed of low-Al orthopyroxene (Mg#[mol MgO*100/(MgO + FeOt )]~85, Al2O32 wt.%), clinopyroxene (Mg# = 82–86), olivine (Mg#~84) and spinel (Cr#[mol Cr2O3/(Cr2O3+Al2O3)]~0.4, which, according to geothermometric calculations, equilibrated at 750–850 ℃. Its pyroxene-rich modal composition suggests that this rock cannot represent a normal lithospheric mantle. Instead, it is supposed that it was formed via magmatic precipitations in the mantle lithosphere. In addition, the Rabrovo olivine websterite shows similar mineral chemical compositions to many other orthopyroxene-rich lithologies worldwide, which origin is commonly associated with subduction settings. Therefore, its presence is considered as additional evidence that the East Vardar ophiolites represent typical supra-subduction ophiolites. |
| Keywords | ultramafic rock; orthopyroxene; subduction; Balkan Peninsula |
