engleski

Nd-Sm AGE OF FELDSPAR ECLOGITES FROM THE EASTERN MACADONIA

The research has been focused on amphibolite bodies in the eastern Macedonia, nearby vilage Koševo, between Štip and Radoviš. The locality has been extensively investigated for the presence of porphiritic copper mineralization in the Bučim block (mine is placed about 5 km toward the south). Eclogite has been reported for the first time in the block by Denkovski & al. (1983, 1984). Later on the occurrence was investigated in more details by several authors (Mirčovski, 1991; Mirčovski 1989; Mirčovski 1990/91; Mirčovski & al., 1997; Korikovsky & al., 1997). Occurrence of eclogite-amphibolite within the Bučim block is structurally placed between Vardar zone and Serbo-Macedonian masiff. It is about 20 km long and about 8 to 12 km wide. There are different oppinions that Bučim block is a part of Vardar zone as well that it is a part of Serbo-Macedonian masiff. In the sorroundings of investigated rocks there are mixed Precambrian, Paleozioc and Tertiary rocks. Precambrian rocks are represented by various types of gneisses, eclogite amphibolite and various amphibolites. Paleozoic rocks are represented by diabase (SE of Koševo) which cuts amphibole-biotite gneiss. Tertiary rocks are represented by trahite and trachyteryolite dykes cutting muscovite-biotite gneiss. Eclogite-amphibolite is named in accordance to proposed nomenclature for this type of rocks (Carswell, 1990). It is possible to distinguish prograde and retrograde phase of metamorphism in the rocks. Peak of prograde metamorphism is estimated to be at 650º C and 12 to 12.5 Kbar. Retrograde phase begun with slight increase of temperature to about 700º C and significant decreasing the pressure to about 4 to 4.5 Kbar (Mirčovski 1990/91;). Eclogite-amphibolite is medium grained, dark green rock built of omphacite, diopside, garnet, two generations of amphibole (tschermakite-pargasite-hastingsite), two generations of plagioclase feldspars (prograde, 12 to 27 mol% An; retrograde, 46 to 73 mol% An), zoisite, quartz, rutile and titanite (there is sometimes corrona of titanite around rutile). It is possible to conclude that metamorfic peak of prograde phase determined on the basis of Sm/Nd method was T=260ą49 Ma (with starting εNd=-0.3) achieved during Upper Permian and it could be interpret as the latest phase of Hercynian orogenesis.

Feldspar eclogite; Nd-Sm isotopic age; Koševo; Macedonia

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