Abstract
Metamorphic evolution of an accretionary wedge can be constrained by a reconstructed P–T conditions of the oceanic and continental margin fragments. This paper deals with the metamorphic overprinting of the Inner Western Carpathians (IWC) Meliatic Triassic–Jurassic paleotectonic units after the closure of the Neotethyan Meliata Basin. Medium to high-pressure and lower temperature conditions were estimated by Perple_X pseudosection modelling, combined with garnet–phengite, calcite–dolomite and chlorite thermometers and chlorite–phengite and phengite barometers. The Late Jurassic subductional burial to a maximum 50 km depth was estimated from the Bôrka Unit continental margin fragments at 520 °C and 1.55 GPa. This is compatible with the metamorphic peak garnet–glaucophane–phengite assemblage of blueschist facies in metabasites. The Jaklovce Unit oceanic fragments were subducted to maximum 35–40 km at 390–420 °C and 1.1–1.3 GPa. Metabasalts and metadolerites contain winchite, riebeckite, actinolite, chlorite, albite, epidote and phengite. A glaucophane-bearing metabasalt recorded an intra-oceanic subduction in blueschist-facies conditions. Rare amphibolite-facies metabasalts of this unit indicate the base of an inferred oceanic crust sliver obducted onto the continental margin wedge. The Meliata Unit oceanic/continental margin flysch calciclastic and siliciclastic metasediments suggest the burial to approximately 15–20 km at 250–350 °C and 0.4–0.6 GPa. This is indicated by a newly formed albite, K-feldspar, illite–phengite and chlorite associated with quartz and/or calcite and dolomite in these rocks. Magnesio-hastingsite to magnesio-hornblende bearing metagabbro with newly formed metamorphic magnesio-riebeckite and actinolite is an inferred detached Meliatic block tectonically emplaced in a Permian salinar mélange in the Silica Nappe hanging wall. Reconstructed P–T paths indicate variable metamorphic conditions from the medium-pressure to high-pressure subduction of the Bôrka and Jaklovce units to the Meliata Unit shallow burial in an accretionary wedge during Late Jurassic to Early Cretaceous Meliaticum evolution. Mélange blocks of Meliaticum incorporate different juxtaposed Meliatic paleotectonic units exposed in nappe outliers overlying the IWC Gemeric and Veporic superunits.
Highlights
The subduction-related accretionary wedges [1] have variable metamorphic P–T conditions of the oceanic and continental margin fragments [2,3,4,5,6,7]
The field investigation was focused on the collection of representative Triassic and Jurassic rock-types of the Meliatic continental and oceanic margin [48]
The mineral element compositions were measured by electron probe microanalysis (EPMA) on a Cameca SX–100 electron microprobe at the State Geological Institute of Dionýz Štúr in Bratislava, and by JEOL Super-probe JXA 8100 at the Earth Science Institute of the Slovak Academy of Sciences in Banská Bystrica
Summary
The subduction-related accretionary wedges [1] have variable metamorphic P–T conditions of the oceanic and continental margin fragments [2,3,4,5,6,7]. Minerals 2020, 10, x FOR PEER REVIEW. MineraTlsh2e02s0u, 1b0d, 1u0c9t4ion-related accretionary wedges [1] have variable metamorphic P–T conditio2nosf o50f the oceanic and continental margin fragments [2,3,4,5,6,7]. The high-pressure rocks in orogenic bbeellttss aarree rreelliiaabbllee mmaarrkkeerrss ooffppaalleeoossuubbdduuccttiioonn zzoonneess. RReeccoonnssttrruucctteedd PP––TT ccoonnddiittiioonnss pprroovviiddee uusseeffuull iinnffoorrmmaattiioonn oonn tthhee bbuurriiaall ddeepptthhss ooff tthhee oorriiggiinnaall ppaalleeootteeccttoonniiccuunniittssiinnaannaaccccrreettiioonnaarryywweeddggee. Rogenic wedge was proposed by [15].
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