No abstract

New laser ablation-inductive coupled plasma-mass spectrometry U-Pb analyses on oscillatory-zoned zircon imply Early Miocene crystallization (18.64 ± 0.11 Ma) of the Pohorje pluton at the southeastern margin of the Eastern Alps (northern slovenia). Inherited zircon cores indicate two crustal sources: a late Variscan magmatic population (~270-290 Ma), and an early Neoproterozoic one (850-900 Ma) with juvenile Hf isotope composition close to that of depleted mantle. Initial εHf of Miocene zircon points to an additional, more juvenile source component of the Miocene magma, which could be either a juvenile Phanerozoic crust or the Miocene mantle. the new U-Pb isotope age of the Pohorje pluton seriously questions its attribution to the Oligocene age 'Periadriatic' intrusions. the new data imply a temporal coincidence with 19-15 Ma magmatism in the Pannonian basin system, more specifically in the styrian basin. K-Ar mineral-and whole rock ages from the pluton itself and cogenetic shallow intrusive dacitic rocks (~18-16 Ma), as well as zircon fission track data (17.7-15.6 Ma), gave late Early to early Middle Miocene ages, indicating rapid cooling of the pluton within about 3 Million years. Medium-grade Austroalpine metamorphics north and south of the pluton were reheated and subsequently cooled together. Outcrop-and micro scale structures record deformation of the Pohorje pluton and few related mafic and dacitic dykes under greenschist facies conditions. Part of the solidstate fabrics indicate E-W oriented stretching and vertical thinning, while steeply dipping foliation and NW-sE trending lineation are also present. the E-W oriented lineation is parallel to the direction of subsequent brittle extension, which resulted in normal faulting and tilting of the earlier ductile fabric at around the Early / Middle Miocene boundary; normal faulting was combined with strike-slip faulting. renewed N-s compression may be related to late Miocene to Quaternary dextral faulting in the area. the documented syn-cooling extensional structures and part of the strike-slip faults can be interpreted as being related to lateral extrusion of the Eastern Alps and/or to back-arc rifting in the Pannonian basin.

The Mura-Zala basin was formed due to ENE-WSW trending crustal extension in the late early and middle Miocene (~19 -11 Ma). Marine sedimentation occurred in several more or less confined depressions (half grabens), then in a unified basin. The rifting phase was probably connected to uplift and brittle-ductile deformation of metamorphic basement at the eastern part of the Pohorje and Kozjak hills. During the late Miocene thermal subsidence, deltaic to fluvial sediments were deposited.After sedimentation, the southernmost Haloze-Budafa sub-basin was inverted. Mapscale folds, reverse and strike-slip faults were originated by NNW-SSE compression during the latest Miocene(?)-Pliocene. After this folding, Karpatian sediments of the Haloze acquired magnetization. During the late(?)Pliocene to Quaternary(?), the whole Mura-Zala basin, including the folded Haloze, suffered ~30° counterclockwise rotation as a relatively rigid block. This rotation affected a wider area from Slovenia to western Hungary and northern Croatia. Kratka vsebinaMura-Zala bazen je nastal v ~asu od poznega zgodnjega do srednjega miocena (~19 -11milj. let) z raztezanjem zemeljske skorje v smeri ENE-WSW. Najprej je sedimentacija potekala v depresijah (poljarkih), zatem pa v enotnem bazenu. Rifting je verjetno spremljalo dvigovanje, razlamljanje in plasti~no deformiranje metamorfne podlage na vzhodnem delu Pohorja in na Kozjaku. Riftingu je v zgornjem miocenu sledilo termalno pogrezanje. Tedaj enotni bazen so zapolnjevali deltni in na koncu re~ni sedimenti.V najpoznej{em miocenu(?) ali pliocenu se je za~elo stiskanje bazena iz smeri NNW-SSE. Med inverzijo ju`nega dela bazena, tj. Haloze-Budafa subbazena, so nastali reverzni in zmi~ni prelomi ter gube. Po gubanju so bili karpatijski sedimenti na novo namagneteni. Zatem pa se je celotni Mura-Zala bazen od poznega(?) pliocena do kvartarja(?) zasukal za ~30° v nasprotni smeri od urinega kazalca skupaj s severno Hrva{ko, zahodno Mad`arsko in vzhodnim delom Vzhodnih Alp.

No abstract

Petrological and geochronological investigations were carried out on metamorphic rocks of the Veporic unit (Inner Western Carpathians) in northern Hungary. K/Ar and Ar/Ar data on micas and amphibole show only Alpine ages (mostly in the range of 87±95 Ma) in this basement unit. Thermobarometric calculations yield lower amphibolite facies peak conditions (ca. 550300 C and 91 kbar) for the Eoalpine metamorphic event. Complex evolution of gneissic rocks is reflected by the presence of discontinuously zoned garnets, the cores of which may represent relics of a pre-Alpine (presumably Variscan) thermal event. Zircon fission track (FT) data in the narrow range of 75±77.5 Ma indicate that this portion of the Veporic unit was emplaced to shallow crustal levels already during the Senonian time. The relative minor difference between zircon FT and K/Ar or Ar/Ar ages suggests very rapid cooling during the Late Cretaceous, most probably related to the extensional unroofing of the Veporic core complex. The obtained cooling ages do not support previous models of Tertiary uplift and exhumation of the Veporic unit along the HurbanovoDiósjeno Í Line.