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7466663 
Journal Article 
Metamorphic evolution and the composition of the protolith of plagioclase-bearing eclogite-amphibolites of the Buchim block of the Serbo-Macedonian massif, Macedonia 
Korikovsky, SP; Mircovski, V; Zakariadze, GS 
1997 
1 
Petrology
ISSN: 0869-5911
EISSN: 1531-8540 
5 
6 
534-549 
English 
WOS:A1997YK13300002 
Mineral equilibria are studied in plagioclase-bearing eclogite-amphibolites and associated garnet-clinopyroxene-amphibole-plagioclase crystalline schists of the Buchim Block of the Serbo-Macedonian Massif. The rocks contain the following stable minerals: clinopyroxene of the Aug-Na-Aug-Omp series with a Jd content from 5 to 34%, garnet with a distinct prograde zoning, hastingsite-tschermakite-pargasite hornblende, and oligoclase. It is shown that Na content in the coexisting Cpx and Pl, the presence of Pl, Hbl, Cpx, and Grt in the metabasites, and transition of the eclogites to eclogite-amphibolites, amphibolites, and crystalline schists are controlled only by the Na/Al, Ca : Al : (Mg, Fe), and (Na + Al)/(Mg + Fe) ratios in the rocks, and not by later feldspathization or amphibolization. The conditions of the prograde stage were as follows: T = 650°C, P = 12-12.5 kbar, depth 46-48 km, and the geothermal gradient was 14°C/km. Reaction textures, such as Cpx2 (0-6% Jd) + Pl2 (25-32% An) kelyphites around the omphacite and Hbl2 + Pl2 (46-73% An) rims around the garnet at its contact with Cpx1 and Hbl1 crystallized only during the late exhumation stage because of the rapid uplift under isothermal conditions or even at an inertial increase in the temperature. The effect of the (Na + Al)/(Mg + Fe) ratio in the eclogites on plagioclase presence or absence in paragenesis with Cpx + Grt, general phase equilibria in the moderate depth eclogite complexes of the plagioclase depth facies, and the boundary reaction of transition to the deeper kyanite facies of depth are considered using the example of the Buchim Block. The protolith of the eclogite-amphibolites under study is close to basalts of mid-oceanic ridges (N- and T-MORB) in composition. The magmas of this composition intruded into the thinned continental crust or sedimentary sequences covering the areas of the young oceanic crust. Copyright © 1997 by MAEe Cyrillic signK Hayκa/Interperiodica Publishing. 
Physical Sciences - Other Topics; geochemical variations, continental-crust, upper-mantle, magmas, rocks