scholarly journals Metamorphic Conditions of Neotethyan Meliatic Accretionary Wedge Estimated by Thermodynamic Modelling and Geothermobarometry (Inner Western Carpathians)

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1094
Author(s):  
Ondrej Nemec ◽  
Marián Putiš ◽  
Peter Bačík ◽  
Peter Ružička ◽  
Zoltán Németh
Keyword(s):  
High Pressure ◽  
Oceanic Crust ◽  
Early Cretaceous ◽  
Continental Margin ◽  
Late Jurassic ◽  
Hanging Wall ◽  
Western Carpathians ◽  
Accretionary Wedge ◽  
Metamorphic Evolution ◽  
Lower Temperature

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.

scholarly journals Origin and Age Determination of the Neotethys Meliata Basin Ophiolite Fragments in the Late Jurassic–Early Cretaceous Accretionary Wedge Mélange (Inner Western Carpathians, Slovakia)

Minerals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 652 ◽  
Author(s):  
Putiš ◽  
Soták ◽  
Li ◽  
Ondrejka ◽  
Li ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Continental Margin ◽  
Deep Water ◽  
Late Jurassic ◽  
Age Determination ◽  
Evolutionary Model ◽  
Western Carpathians ◽  
Alkaline Basalt ◽  
Accretionary Wedge ◽  
Depleted Mantle

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.

Deciphering the geodynamic evolution of the Dinaric orogen through the study of the ‘overstepping’ Cretaceous successions

2020 ◽  
Vol 157 (8) ◽  
pp. 1238-1264
Author(s):  
Giuseppe Nirta ◽  
Martin Aberhan ◽  
Valerio Bortolotti ◽  
Nicolaos Carras ◽  
Francesco Menna ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Continental Margin ◽  
Late Jurassic ◽  
Carbonate Platform ◽  
Depositional Environments ◽  
Small Scale ◽  
Large Area ◽  
Geodynamic Evolution ◽  
Sedimentary Evolution ◽  
Platform System

AbstractAlong the Dinaric–Hellenic orogen, the Late Jurassic – Early Cretaceous ophiolite obduction over the Adria continental margin was sealed by sedimentation of clastic terrestrial deposits rapidly followed by a widespread carbonate platform system since the Early Cretaceous period. These Cretaceous sediments presently crop out over areas of varying extension, from several hundred kilometre wide undeformed continuous covers to small-scale tectonic slivers involved in the tectonic stack following the latest Cretaceous–Palaeogene collision. These deposits are unconformably sedimented above the units formed by the Late Jurassic to Early Cretaceous nappe stacking above the eastern Adria continental margin. We studied these deposits in a large area between western Serbia and eastern Bosnia. In the studied area, these deposits are divided into three lithostratigraphic groups according to their age, depositional environment and type of underlying basement. The Mokra Gora Group sediments (upper Aptian–Maastrichtian) were deposited on top of previously obducted and weathered ophiolites, the Kosjerić Group (Cenomanian–Campanian) overlies composite tectonic units comprising obducted ophiolites and their underlying continental basement portions, while the Guča Group (Campanian–Maastrichtian) exclusively rests on top of continental basement. The reconstructed sedimentary evolution of these groups, together with the comparison with the syn- and post-obduction deposits at the front of the ophiolitic nappe(s) in a wider area of the internal Dinarides (e.g. Pogari Group and Bosnian flysch), allowed us to clarify the obduction mechanisms, including their tectonic context, the changes in depositional environments and the timing of depositional and tectonic events, and, in a wider view, shed light on the geodynamic evolution of the Dinaric belt.

The newest structures of the Heraclion peninsula (South-Western Crimea)

2019 ◽  
pp. 8-16
Author(s):  
M. Yu. Promyslova ◽  
G. V. Bryantseva ◽  
L. I. Demina ◽  
N. I. Kosevich
Keyword(s):  
Oceanic Crust ◽  
Coastal Zone ◽  
Early Cretaceous ◽  
Late Jurassic ◽  
Fracture Zones ◽  
The South ◽  
South Eastern ◽  
Back Arc ◽  
Geomorphological Analysis

The article presents the results of the structural-geomorphological analysis of the Heraklion peninsula of the South-Western Crimea. The Western, Central and South-Eastern segments are distinguished, differing in density and direction of fracture zones, faults, the nature of the ravine-gulch net, and the structure of the coastal zone. It is shown that neotectonic movements in the upper structural floor are most intensively manifested over the Late Jurassic-Early Cretaceous collisional suture formed when the back-arc basin with the oceanic crust was closed.

LATE JURASSIC-EARLY CRETACEOUS RIFTING ON THE SOUTHWEST AUSTRALIAN CONTINENTAL MARGIN: RESULTS FROM IODP EXPEDITION 369

2019 ◽  
Author(s):  
Dennis L. Harry ◽  
◽  
Eun Young Lee ◽  
Maria Luisa G. Tejada ◽  
Carmine C. Wainman ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Continental Margin ◽  
Late Jurassic

scholarly journals Where was the Magura Ocean?

2015 ◽  
Vol 65 (3) ◽  
pp. 319-344 ◽  
Author(s):  
Nestor Oszczypko ◽  
Andrzej Ślączka ◽  
Marta Oszczypko-Clowes ◽  
Barbara Olszewska
Keyword(s):  
Early Cretaceous ◽  
Late Cretaceous ◽  
Late Jurassic ◽  
Source Area ◽  
Western Carpathians ◽  
Sedimentary Evolution ◽  
Outer Western Carpathians ◽  
Different Parts

Abstract In the Late Jurassic to Early Cretaceous palaeogeography of the Alpine Tethys the term Ocean is used for different parts of these sedimentary areas: eg. Ligurian – Piedmont and Penninic, Magura, Pieniny, Valais and Ceahlau-Severins oceans. The Magura Ocean occupied the more northern position in the Alpine-Carpathian arc. During the Late Cretaceous–Paleogene tectono-sedimentary evolution the Magura Ocean was transformed into several (Magura, Dukla, Silesian, sub-Silesian and Skole) basins and intrabasinal source area ridges now incorporated into the Outer Western Carpathians.

Late Jurassic to early Early Cretaceous tectonic nature on the NE Asian continental margin: Constraints from Mesozoic accretionary complexes

2020 ◽  
Vol 200 ◽  
pp. 103042 ◽  
Author(s):  
Yu Li ◽  
Wen-Liang Xu ◽  
Ri-Xiang Zhu ◽  
Feng Wang ◽  
Wen-Chun Ge ◽  
...  
Keyword(s):  
Early Cretaceous ◽  
Continental Margin ◽  
Late Jurassic
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