U-Pb ZIRCON AGES OF DIORITIC AND TRONDHJEMITIC ROCKS FROM A LAYERED AMPHIBOLITIC COMPLEX CROSSCUT BY GRANITE VEIN (VEPORIC BASEMENT, WESTERN CARPATHIANS)

Year, pages: 2001, 49 - 60

The complex of Ky-Grt paragneisses, granitic to tonalitic orthogneisses, migmatitic gneisses and homogeneous to layered amphibolites was intruded by dioritic-gabbroic more or less concordant dykes and sills during the syn-metamorphic extension in the host regional metamorphic rocks. They now have the character of dioritic orthogneisses. The whole lithological sequence was then structurally unified during the late-metamorphic cooling and exhumation within the deep-crustal shear zone. The dioritic orthogneisses bear the features of pre-metamorphic compositional layering into cumulate-like hornblendite(±Px), gabbro-diorite, tonalite to trondhjemite. Magmatic layering has been transformed to subsolidus high-temperature layering along the extensional meso-shear bands filled with leucotonalitic melt seggregates crosscutting former magmatic structures at acute to medium angles. A new ductile strain relocalization enhanced mechanical differentiation of dark and felsic minerals into often isoclinally folded layers, with the crystallographic preferred orientation fabrics of amphibole, plagioclase and quartz indicating a layer parallel shear. The U-Pb zircon age of porphyric metadiorites 346±1 Ma (Early Carboniferous) is related to their magmatic emplacement, immediately followed by the high-temperature mylonitization. We also dated zircon of metatrondhjemitic orthogneiss from the layered amphibolite. An upper intercept age 514±24 Ma (Late Cambrian) is interpreted as dating the magmatic compositional differentiation of a gabbro-dioritic complex into cumulate-like hornblenditic, gabbrodioritic, tonalitic to trondhjemitic layers, which is an inherited feature in layered amphibolites (with blastic textures). The lower intercept age 348±31 Ma (Early Carboniferous) obviously reflects the time of regional-metamorphic event and formation of layered amphibolites. The whole composite (VZP-CB) structural complex is crosscut by plagiogranite-aplitic veins dated 233±4 Ma (Early Triassic).

Putis, M., B. Kotov, A., P. Korikovsky, S., B. Salnikova, E., Z. Yakovleva, S., G. Berezhnaya, N., P. Kovach, V., V. Plotkina, J. 2001. U-Pb ZIRCON AGES OF DIORITIC AND TRONDHJEMITIC ROCKS FROM A LAYERED AMPHIBOLITIC COMPLEX CROSSCUT BY GRANITE VEIN (VEPORIC BASEMENT, WESTERN CARPATHIANS). In Geologica Carpathica, vol. 52, no.1, pp. 49-60. 1335-0552.

Putis, M., B. Kotov, A., P. Korikovsky, S., B. Salnikova, E., Z. Yakovleva, S., G. Berezhnaya, N., P. Kovach, V., V. Plotkina, J. (2001). U-Pb ZIRCON AGES OF DIORITIC AND TRONDHJEMITIC ROCKS FROM A LAYERED AMPHIBOLITIC COMPLEX CROSSCUT BY GRANITE VEIN (VEPORIC BASEMENT, WESTERN CARPATHIANS). Geologica Carpathica, 52(1), 49-60. 1335-0552.