Meta-igneous rocks of the West-Carpathian basement, Slovakia: indicators of Early Paleozoic extension and shortening events

The paper reviews the main West-Carpathian Early Paleozoic metamorphosed originally sedimentary-magmatic complexes, dated by SHRIMP on zircons, as indicators of crustal extension and shortening events. Igneous precursors of a Layered Amphibolite. Complex (LAC) - fractionated upper mantle gabbros to diorites, dated at 503 +/- 4 and 492 +/- 4 Ma from the North-Veporic, or 480 +/- 5 and 450 +/- 6 Ma from the Tatric basement are contemporaneous with subaluminous to metaluminous I-type (507 +/- 4 Ma, the South-Veporic basement), peraluminous S-type (497 +/- 4 Ma, the South-Veporic basement; 516 +/- 7, 485 +/- 6 and 462 +/- 6 Ma, the North-Veporic basement; 497 +/- 6, 472 +/- 6 and 450 +/- 6 Ma, the Tatric basement), alkaline A-type (511 +/- 6 Ma, South-Veporic basement) granitic orthogneisses and calcalkaline rhyolitic (482 +/- 6 Ma) and dacitic (476 +/- 7 Ma) metavolcanics (Gemeric basement), indicating a magmatic immature back arc setting. The ages point to Middle/Late Cambrian, Early and Late Ordovician magmatic phases, coeval with the extension in the northern Gondwana margin. Separation of an inferred Avalonian and/or Galatian terranes distal continental ribbon corresponds with the opening of a Medio-European Basin. A 430-390 Ma dated MP/HP metamorphic event, recorded in the LAC and associated orthogneisses, occurred in the area of thinned immature back arc basin crust due to closure of the Medio-European Basin. Thus a distal Gondwana continental ribbon north of this basin could be an eastward lateral pendant of Armorica, derived from Galatian terrane. Metaophiolites of the Pernek Group (a metagabbrodolerite dated at 371 +/- 4 Ma) in the Tatric basement, analogous to island-arc tholeiites and back-arc basin basalts, indicate a back-arc basin setting north of a 430-390 Ma old northward dipping subduction/collision zone, dividing the northward drifting western Galatian terrane microplate from the Gondwana margin. Some metabasites of the Gemeric basement might indicate Late Devonian to Mississippian opening of a peri-Gondwanan Paleotethyan oceanic basin: a 383 +/- 3 Ma old remelted metagabbro (482 +/- 9 Ma) from the Klatov gneiss-amphibolite complex, ca. 385 Ma old porphyritic metabasite of the Zlatnik ophiolite complex, as well as a 350 +/- 5 Ma old HP metabasite as tectonic fragment within the Rakovec Group. The closure of Devonian-Mississippian basins, accompanied by medium-pressure (the Pernek Group) to high-pressure (blueschist to eclogitic tectonic fragments in greenschist facies rocks of the Rakovec Group) metamorphism, occurred in late Carboniferous to early Permian, when Paleotethyan realm complexes accreted to a Galatian terrane microplate, the latter represented by the older and the higher-grade Tatric and Veporic basement complexes.