This study reports the Neotethyan Meliata Basin ophiolite fragments in the Late Jurassic–Early Cretaceous accretionary wedge mélange in the southern part of the Inner Western Carpathians (IWC). Here we present new lithostratigraphical, petrographical, geochemical, and geochronological data obtained from the mélange blocks used to reconstruct the Meliaticum paleotectonic zones in a tentative evolutionary model of this accretionary wedge. The Dobšiná mélange block continental margin carbonatic and siliciclastic sediments have calc-alkaline basalt intercalations. The basalt Concordia age dated to 245.5 ± 3.3 Ma by U–Pb SIMS on zircon most likely indicates the pre-oceanic advanced early Middle Triassic continental rifting stage. The evolving marginal oceanic crust is composed of Middle to Upper Triassic cherty shales to radiolarites. The detrital zircon U–Pb SIMS Concordia ages of 247 ± 4 Ma and 243 ± 4 Ma from a cherty shale, and the xenocryst zircon population Concordia age of 266 ± 3 Ma from a 0.5 m thick “normal” mid-ocean ridge (N-MOR) basalt layer in this cherty shale reveal the connection of the oceanic basin to the adjacent rifting continental margin. The chertified reddish limestone transition to radiolarite indicates syn-rift basin deepening. Upwards, regular alternating N-MOR basalts and radiolarites are often disturbed by peperite breccia horizons. The Nd isotope values of these basalts (εNd₂₄₀ = 7–8) are consistent with their chondrite normalized rare earth element (REE) patterns and indicate a depleted mantle source. The Triassic ophiolitic suite also comprises rare ocean island (OI) basalts (εNd₂₄₀ = 5) and serpentinized subduction unrelated peridotites. The Middle to Late Jurassic shortening and southward intra-oceanic and continental margin subduction at approximately 170–150 Ma enhanced the formation of the trench-like Jurassic flysch succession which preceded the closure of the Meliata Basin. The flysch sediments form a mélange matrix of olistolithic unsubducted, obducted, and MP–HP/LT metamorphosed exhumed blocks of the Triassic to Lower Jurassic successions. Blocks of peridotites, rodingites, blueschists, greenschists, rare amphibolites, deep-water shaly sediments and shallow- to deep-water carbonates are typical members of the mélange. The Meliatic accretionary wedge mélange nappe outliers were incorporated in the IWC orogenic wedge in the late Early Cretaceous according to metamorphic rutile U–Pb SIMS ages of 100 ± 10 Ma determined from a Jaklovce metabasalt.

Permian biotite leucogranites to granite porphyries and rhyolites form small intrusions in several Alpine tectonic units in the Western Carpathians and the Pannonian region (Slovakia and Hungary). Their A-type signature is inferred from main- and trace-element geochemistry, with high K, Rb, Y, REE, Zr, Th, Nb, Fe/Mg and Ga/Al, low Al, Mg, Ca, P, Sr, V and strong negative Eu-anomaly. This geochemical signature is further supported by the mineralogy comprising local hypersolvus alkali feldspars, annitic biotite and the presence and composition of HFSE accessory minerals. The δ¹⁸O values measured for zircon (mean value 8.3 ‰ ± 0.36) may be explained by the melting of igneous material of crustal origin and/or mantle basalts which interacted with low-temperature fluids. The in-situ SHRIMP U–Pb isotope dating of zircon from the granites highlights two different periods of magmatic crystallisation and pluton emplacement: the older 281 ± 3 Ma Cisuralian age in the southern part, Velence Hills in the Pannonian region (Transdanubian Unit) and younger Guadalupian ages in the northern part, the West-Carpathian area: 262 ± 4 Ma (Turčok, Gemeric Unit), 267 ± 2 Ma (Hrončok, Veporic Unit) and 264 ± 3 Ma (Upohlav, granitic pebbles in Cretaceous conglomerates of the Pieniny Klippen Belt). The ~ 280 to 260-Ma interval is simultaneous with post-orogenic or anorogenic, rift-related and mainly alkaline (A-type) magmatism on the broader European scale. Our study documents a close relationship between the Permian continental rifting and the Neotethyan Meliatic oceanic basin opening in the Middle Triassic. The A-type granites originated from the partial melting of the ancient lower crustal quartzo-feldspatic rocks with the possible contribution of meta-basic material from the mantle in an extensional tectonic regime consistent with disintegration of the Pangea supercontinent during the Permian–Triassic period.

The Dinaride Ophiolite Belt formed from the Jurassic part of the Neotethys. The investigated Ozren ophiolite complex in Bosnia and Herzegovina consists of peridotites, plagioclase peridotites, plagiogranites, troctolites and other gabbroic rocks, and fewer basalts. Lherzolites and harzburgites contain corroded ortho- and clinopyroxene1 porphyroclasts enclosed in the olivine matrix. The boundaries between olivine aggregates and pyroxene1 and spinel1 are infilled by medium-grained undeformed aggregates of clinopyroxene2, less orthopyroxene2, spinel2, and often clinopyroxene3-spinel3 symplectites. These textures indicate the final crystallization of peridotite in subsolidus conditions. Partial dissolution of deformed pyroxene1 porphyroclasts and coarse-grained spinel1 most likely occurred due to their reaction with the rest melt present in the grain boundaries. The Al decrease from pyroxene1 to pyroxene2 and 3, or the Cr decrease and Al increase from spinel1 to spinel2 and 3 is characteristic. Peridotites are associated with inferred remnants of a gabbro-dolerite layer, whereas basalts and radiolarites occur as rare dm-size fragments in an ophiolitic breccia. Troctolites display interstitial crystallization of plagioclase, clinopyroxene, less Na-Ti-rich amphiboles, and phlogopite in the olivine-spinel matrix, indicating the replacive character of impregnating melt within the dunite layers. Clinopyroxene-plagioclase-ilmenite-±amphibole gabbroic and fewer basaltic dykes in peridotites formed due to subridge extension, mantle thinning, and the deeper mantle melting. Iron-enriched olivines occur in the peridotite-dyke interfaces and troctolites. Hydrated ultramafics and mafics contain amphiboles, biotite, phlogopite, clinozoisite, epidote, and chlorite aggregates. Estimated magmatic to subsolidus T from peridotite two-pyroxene thermometry are 1000–850 °C, for the spinel facies. Ca-in-orthopyroxene1 thermometry provided T of 1028–1068 °C, and Ca-in-orthopyroxene2 thermometry gave 909–961 °C at estimated P of 1.1–0.9 GPa. However, the gabbroic dyke magmatic crystallization T was constrained to 1200–1100 °C at P of 0.45–0.15 GPa by single clinopyroxene thermobarometry. The obtained P–T conditions constrained the deeper mantle environment for the formation of peridotites than troctolites and crosscutting dykes. The ophiolitic thrust-sheet hanging wall conditions in an obduction-related accretionary wedge were estimated from amphibolites at 620 °C and 0.85 GPa by Ti-in-amphibole thermometry and amphibole-plagioclase thermobarometry. 300 °C and 0.5 GPa were determined from an exhumation shear zone using a combination of chlorite thermometry and Si-in-phengite barometry.