Coincidence of gabbro and granulite formation and their implication for Variscan HT metamorphism in the Moldanubian Zone (Bohemian Massif), example from the Kutná Hora Complex

0462061 - GLÚ 2017 RIV NL eng J - Článek v odborném periodiku
Faryad, S. W. - Kachlík, V. - Sláma, Jiří - Jedlička, R.
Coincidence of gabbro and granulite formation and their implication for Variscan HT metamorphism in the Moldanubian Zone (Bohemian Massif), example from the Kutná Hora Complex.
Lithos. Roč. 264, 1 October (2016), s. 56-69. ISSN 0024-4937. E-ISSN 1872-6143
Institucionální podpora: RVO:67985831
Klíčová slova: spinel-bearing gabbro * Variscan age * granulite * heat source
Kód oboru RIV: DB - Geologie a mineralogie
Impakt faktor: 3.677, rok: 2016

Leucocratic metagabbro and amphibolite from a mafic–ultramafic body within migmatite and granulite in the Kutná Hora Complex were investigated. The mafic–ultramafic rocks show amphibolite facies metamorphism, but in the central part of the body some metagabbro preserves cumulus and intercumulus plagioclase,
clinopyroxene and spinel. Spinel forms inclusions in both clinopyroxene and plagioclase and shows various degree of embayment structure, thatwas probably a result of reactionwith melt duringmagmatic crystallization. In the metagabbro, garnet forms coronae around clinopyroxene at the contacts with plagioclase. Amphibolite contains garnetwith prograde zoning and plagioclase. Phase relations of igneous and metamorphic minerals indicate thatmagmatic crystallization and subsequent metamorphismoccurred as a result of isobaric cooling at a depth of 30–35 km. U–Pb dating on zircon fromleucogabbro yielded a Variscan age (337.7±2Ma) that is similar or close to the age of granulite facies metamorphism (ca 340 Ma) in the Moldanubian Zone. Based on the calculated PT conditions and age data, both the mafic–ultramafic body and surrounding granulite shared the sameexhumation path fromtheir middle–lower crustal position at the end of Variscan orogeny. The coincidence ofmafic–ultramafic intrusives and granulite–amphibolite facies metamorphismis explained by lithospheric upwelling beneath the
Moldanubian Zone that occurred due to slab break-off during the final stages of subduction of the Moldanubian plate beneath the Teplá Barrandian Block. The model also addresses questions about the preservation of minerals and/or their compositions from the early metamorphic history of the rocks subjected to ultradeep subduction and subsequent granulite facies metamorphism.
Trvalý link: http://hdl.handle.net/11104/0261602