Contrasting compositions and densities of fluid inclusions were revealed in siderite-barite intergrowths of the Drozˇdiak polymetallic vein hosted in Variscan basement of the Gemeric unit (Central European Carpathians). Primary two-phase aqueous inclusions in siderite homogenized between 101 and 165°C, total salinity ranged between 18 and 27 wt%, and CaCl 2 ⁄ (NaCl + CaCl 2 ) weight ratios were fixed at 0.1-0.3. By contrast, mono-and two-phase aqueous inclusions in barite exhibited total salinities between 2 and 22 wt%, and the CaCl 2 ⁄ NaCl ratios ranged from NaCl-to CaCl 2 -dominated compositions. The aqueous inclusions in barite were closely associated with very high-density (0.55-0.745 g cm )3 ) nitrogen inclusions, in some cases containing up to 16 mol.% CO 2 . Crystallization P-T conditions of siderite (175-210°C, 1.2-1.7 kbar) constrained by the vertical oxygen isotope gradient along the studied vein, isochores of fluid inclusions and the K ⁄ Na exchange thermometer corresponded to minimal palaeodepths between 4.3 and 6.3 km, assuming lithostatic load and average crust density of 2.75 g cm )3 . Maximum fluid pressure during barite crystallization attained 3.6-4.4 kbar at 200-300°C, and the most dense nitrogen inclusions maintained without decrepitation the residual internal pressure of 2.2 kbar at 25°C. Contrasting fluid compositions, increasing depths of burial ($4-14 km) and decreasing thermal gradients ($40-15°C km )1 ) during initial mineralization stages of the Drozˇdiak vein reflect Alpine orogenic processes, rather than an incipient Permian rifting suggested in previous metallogenetic models. Siderite crystallized at rising P-T in a closed, rock-buffered hydrothermal system developed in the Variscan basement during the north-vergent Cretaceous thrusting and thickening of the Gemeric crustal wedge. Variable salinities of the barite-hosted inclusions reflect a fluid mixing in open hydrothermal system, and re-equilibration textures (lengths of decrepitation cracks proportional to fluid inclusion sizes) correspond to retrograde crystallization trajectory coincidental with transpression or unroofing. Maximum recorded fluid pressures indicate $12-km-thick pile of imbricated nappe units accumulated over the Gemeric basement during the Cretaceous collision.

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 Klátov gneiss-amphibolite complex, ca. 385 Ma old porphyritic metabasite of the Zlatník 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. Les roches orthodérivées du socle de la chaîne des Carpates occidentales (Slovaquie), témoins des événements extensifs et compressifs du Paléozoïque inférieurMots-clés. -Roches orthodérivées, Extension, Raccourcissement (compression), Paléozoïque inférieur, Carpates occidentales, Marge gondwanienne. Résumé. -Cet ar...

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Three small bodies of amphibolites and associated graphitic gneisses from the Suchý and Malá Magura Mountains (Tatric Megaunit, central Western Carpathians) have been studied by petrographic and geochemical methods. Isolated, fault-bounded bodies first hundreds of meters in size are located in the complex of the Early Paleozoic paragneisses and migmatites intruded by the Lower Carboniferous granitoid rocks. Amphibolites (locally actinolite schists) were formed from effusive basalts, dolerites or isotropic gabbros hydrothermally altered and veined before the regional metamorphic transformation. Distribution of the trace elements relatively immobile during the metamorphic alteration (HFSE, REE, Cr, V, Sc) is similar to E-MORB type in the Malá Magura Mountain or to N-MORB/E-MORB types in the Suchý Mountain. Graphitic gneisses to metacherts are rich in silica (up to 88 wt. %) and C tot , poor in other major element contents and display negative Ce-anomaly, enrichment in HREE, V, Cr and U. They were probably originally deposited as non-carbonate and silica-rich deep-sea sediments in anoxic conditions. The oceanic provenance of amphibolites and related graphitic gneisses clearly indicates their oceanic crust affinity and identity with the uppermost part of the ophiolite sequence. Ophiolite bodies from the Suchý and Malá Magura Mountains are supposed to be relic fault blocks identical with the Upper Devonian Pernek Group which represents a Variscan ophiolite nappe preserved to large extent in the Malé Karpaty Mountains located in the Tatric Megaunit further to the southwest. All these ophiolite relics are vestiges of the original ophiolite suture created by oceanic closure in the Lower Carboniferous.

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