Dating granulite-facies structures and the exhumation of lower crust in the Moldanubian Zone of the Bohemian Massif

• Published in: International journal of earth sciences : Geologische Rundschau Vol. 91; no. 3; pp. 373 - 385
• Main Authors: Svojtka, M., Košler, J., Venera, Z.
• Format: Journal Article
• Language: English
• Published: Berlin Springer Nature B.V 01-05-2002
• Subjects: Deformation; Evolution; Geophysics; Granite; Metamorphism
• ISSN: 1437-3254; 1437-3262
• DOI: 10.1007/s00531-001-0230-2

Deformation of granulite-facies rocks in the Moldanubian Zone of the southern Bohemian Massif is expressed in two intersecting planar fabrics - steeply disposed (S^sub 1^) and flat-laying (S^sub 2^) - which correspond to two deformation stages (D^sub 1^) and (D^sub 2^). The existing Sm-Nd garnet ages from banded granulite gneisses, new U-Pb zircon data from deformed granite intrusions within the granulite gneisses, and the P-T and field structural relations constrain the ages and P-T conditions of the two deformation phases. The early deformation (D^sub 1^) was associated with a HP-HT metamorphic stage with a minimum age of ca. 354 Ma which was followed by a near-isothermal decompression. A concordant U-Pb zircon age of 318±1 Ma dates the emplacement of intrusions of deformed granite into the granulite gneisses and constrains deformation phase (D^sub 2^). This phase was associated with an LP-HT metamorphism dated in the region at ca. 340-330 Ma. The available structural and isotopic data indicate that granulites in the southern Bohemian Massif were exhumed from lower to middle crust during compression. The structural relations and P-T-t data for the studied granulites are consistent with their exhumation by near-vertical extrusion of the softened orogenic root.[PUBLICATION ABSTRACT]