Carpathian peri-Gondwanan terranes in the East Carpathians (Romania): A testimony of an Ordovician,North-African orogeny     

Ioan Balintoni  Constantin Balica 《Gondwana Research》2013,23(3):1053-1070

The eastern branch of the Romanian Carpathians – the East Carpathians – is essentially an Alpine thrust and fold belt made up in its median part by a Crystalline–Mesozoic zone. This, in turn, is built up by several Alpine nappes (top to bottom): the Wildflysch, Bucovinian, Subbucovinian and Infrabucovinian. In the basement of the Bucovinian and Subbucovinian nappes the following Variscan tectonic units have been identified (top to bottom): Rar?u, Putna, Pietrosu Bistri?ei and Rodna. The Infrabucovinian nappes comprise the Rar?u nappe only. The Alpine nappes have an eastward vergence, opposite to the Variscan ones (present coordinates). In terms of pre-Variscan terranes distribution, the Rar?u nappe involved the Bretila terrane basement and its late Paleozoic cover, Putna the Tulghe? terrane basement, Pietrosu Bistri?ei the Negri?oara terrane basement and Rodna the Rebra terrane basement. These terranes originated along northwestern Gondwana margin during some Ordovician thermotectonic events. They do not represent Cadomian terranes and we call them Carpathian-type terranes. Two igneous protoliths from Bretila terrane basement (i.e. Anie? orthogneiss and H?ghima? granitoid) yield U/Pb LA-ICP-MS zircon ages of 462 ± 3 Ma and 469.2 ± 6.5 Ma, respectively. An orthogneiss from Tulghe? terrane basement yield 462.6 ± 3.1 Ma; the Pietrosu porphyritic orthogneiss from Negri?oara terrane basement yield 461.1 ± 5.2 Ma; and the Nichita? orthogneiss from Rebra terrane basement yield 447.9 ± 2.8 Ma. All these ages suggest the magma crystallization time. Two paragneisses from the Rebra terrane basement show a detrital zircon age distribution characteristic of a NE-African provenance. Regarding the tectonic settings, the lithology of the Bretila terrane suggests a magmatic arc on a continental margin, while of the Tulghe? terrane suggests a back arc environment, and those of the Rebra and Negri?oara terranes suggest a passive continental margin. An Ordovician metamorphism of medium grade (staurolite–kyanite zone) affected the basements of Bretila, Negri?oara and Rebra terranes, whereas a low grade (chlorite to biotite zone) event affects the Tulghe? terrane. With regard to the Variscan orogeny, the existence of a Paleotethys suture is proposed within the metamorphic basement of the East Carpathians. In this interpretation, the Bretila terrane was the upper plate, the Rebra and Negri?oara terrane pair formed the lower plate and the Tulghe? terrane was a component of the suture. The Variscan thermotectonic events reflect isothermal decompression with andalusite + cordierite in the basement of the Rebra terrane and retrogression in the basement of the other terranes.  相似文献   

Effects of the orbital eccentricity on the equipotential surfaces in binary systems     

Ioan Todoran 《Astrophysics and Space Science》1993,199(2):257-263

In the frame of the elliptical restricted three-body problem, the differential equations for the motion of an infinitesimal body are established. In spite of the lack of Jacobi's integral, for fixed values of the true anomaly (v = 0°, 90°, and 180°), particular results were obtained. The pulsational character of the equipotential surfaces is evident.  相似文献   

Calpionellids and calcispheres from the upper Jurassic-lower Cretaceous deposits in the Resita-Moldova Noua zone, Southern Carpathians, Romania     

Ioan I. Bucur 《Cretaceous Research》1992,13(5-6)

An assemblage of calpionellids and calcispheres identified in five lithostratigraphic units allows the identification of eight biozones in the upper Oxfordian-Hauterivian interval. Since the biozonation according to calpionellids has already been accurately defined by Pop (1974, 1989) for the Marila Limestones and Crivina Marls, the novelty of our approach resides mainly in the extension of this biozonation to the over- and underlying lithostratigraphic units using calcispheres. The possibility of micropalaeontologically delimiting the Valea Aninei Limestones is extremely significant, since the age of these limestones has been estimated so far only by their geometrical setting in the lithostratigraphic sequence of formations in the area.  相似文献   

Magmagenesis in a subduction-related post-collisional volcanic arc segment: the Ukrainian Carpathians   总被引：6，自引：0，他引：6  

Ioan Seghedi  Hilary Downes  Zolt  n P  cskay  Matthew F. Thirlwall  Alexandru Szak  cs  Michail Prychodko  David Mattey 《Lithos》2001,57(4):237-262

Calc-alkaline magmatism in the south-west Ukraine occurred between 13.8 and 9.1 Ma and formed an integral part of the Neogene subduction-related post-collisional Carpathian volcanic arc. Eruptions occurred contemporaneously in two parallel arcs (here termed Outer Arc and Inner Arc) in the Ukrainian part of the Carpathians. Outer Arc rocks, mainly andesites, are characterized by LILE enrichment (e.g. K and Pb), Nb depletion, low compatible trace element abundances, high ⁸⁷Sr/⁸⁶Sr, high δ¹⁸O and low ¹⁴³Nd/¹⁴⁴Nd isotopic ratios (0.7085–0.7095, 7.01–8.53, 0.51230–0.51245, respectively). Inner Arc rocks are mostly dacites and rhyolites with some basaltic and andesitic lavas. They also show low compatible element abundances but have lower ⁸⁷Sr/⁸⁶Sr, δ¹⁸O and higher ¹⁴³Nd/¹⁴⁴Nd ratios (0.7060–0.7085, 6.15–6.64, 0.5125–0.5126, respectively) than Outer Arc rocks. Both high-Nb and low-Nb lithologies are present in the Inner Arc. Based on the LILE enrichment (especially Pb), a higher fluid flux is suggested for the Outer Arc magmas compared with those of the Inner Arc.

Combined trace element and Sr–Nd–O isotopic modelling suggests that the factors which controlled the generation and evolution of magmas were complex. Compositional differences between the Inner and Outer Arcs were produced by introduction of variable proportions of slab-derived sediments and fluids into a heterogeneous mantle wedge, and by different extents of upper crustal contamination. Degrees of magmatic fractionation also differed between the two arcs. The most primitive magmas belong to the Inner Arc. Isotopic modelling shows that they can be produced by adding 3–8% subducted terrigenous flysch sediments to the local mantle wedge source. Up to 5% upper crustal contamination has been modelled for fractionated products of the Inner Arc. The geochemical features of Outer Arc rocks suggest that they were generated from mantle wedge melts similar to the Inner Arc primitive magmas, but were strongly affected by both source enrichment and upper crustal contamination. Assimilation of 10–20% bulk upper crust is required in the AFC modelling, assuming an Inner Arc parental magma. We suggest that magmagenesis is closely related to the complex geotectonic evolution of the Carpathian area. Several tectonic and kinematic factors are significant: (1) hydration of the asthenosphere during subduction and plate rollback directly related to collisional processes; (2) thermal disturbance caused by ascent of hot asthenospheric mantle during the back-arc opening of the Pannonian Basin; (3) clockwise translational movements of the Intracarpathian terranes, which facilitated eruption of the magmas.  相似文献   

Provenance of Oligocene lithic and quartz arenites of the East Carpathians: Understanding sediment routing systems on compressional basin margins     

Relu D. Roban  Mihai N. Ducea  Vlad I. Mihalcea  Ioan Munteanu  Victor Barbu  Mihaela C. Melinte-Dobrinescu  Cornel Olariu  Mihai Vlăsceanu 《Basin Research》2023,35(1):244-270

We present new sedimentological, petrographical, palaeontological and detrital zircon U–Pb data on late Oligocene–early Miocene sedimentary rocks of the thin-skinned thrust belt of East Carpathians. These data were acquired to reconstruct the sedimentary routing system for two compositionally different turbidite fans made of the regionally extensive Kliwa and Fusaru formations. On the eastern margin of the Moldavides foreland basin, large low-gradient river systems draining the East European Platform provided well-sorted quartz-rich sand forming deltas on wide shallow shelves and thick Kliwa submarine fans. Due to the westward subduction of a thinned continental plate, the western basin margin was characterized by short, steep-gradient routing systems where sediment transport to deep water was mainly through hyperpycnal flows. The Getic and Bucovinian nappes of the East Carpathians and the exhumed Cretaceous–Early Palaeogene orogenic wedge fed Fusaru fans with poorly sorted lithic sand. The Fusaru fans trend northwards in the foredeep basin having an elongate depocentre, interfingering and then overlapping on the distal part of the Kliwa depositional system due to the eastward advance of the Carpathian fold-and-thrust belt. A smaller sediment input is supplied by southern continental areas (i.e. Moesian Platform, North Dobrogea and potentially the Balkans). In general, the sandstone interfingering between distinct basin floor fan systems is less well documented because the facies would be similar and there are not many systems that have a distinct sediment provenance like Kliwa and Fusaru systems. This case study improves the understanding of regional palaeogeography and sedimentary routing systems and provides observations relevant here or elsewhere on the interfingering turbidite fan systems.  相似文献   

A corrected 3-D SPH method for breaking tsunami wave modelling     

Jinsong Xie  Ioan Nistor  Tad Murty 《Natural Hazards》2012,60(1):81-100

A 3-D large eddy simulation model that was first transformed to smoothed particle hydrodynamics (LES-SPH)-based model was employed to study breaking tsunami waves in this paper. LES-SPH is a gridless (or mesh-free), purely Lagrangian particle approach which is capable of tracking the free surface of violent deformation with fragmentation in an easy and accurate way. The Smagorinsky closure model is used to simulate the turbulence due to its simplicity and effectiveness. The Sub-Particle Scale scheme, plus the link-list algorithm, is applied to reduce the demand of computational power. The computational results show that the 3-D LES-SPH model can capture well the breaking wave characteristics. Spatial evolution features of breaking wave are presented and visualized. The detailed mechanisms of turbulence transport and vorticity dynamics are demonstrated as well. This application also presents an example to validate the SPH model.  相似文献   

Guest editorial: Paleotsunami     

Arun Kumar  Ioan Nistor 《Natural Hazards》2012,63(1):1-3

  相似文献   

Short-lived eruptive episodes during the construction of a Na-alkalic basaltic field (Perşani Mountains,SE Transylvania,Romania)     

Ioan Seghedi  Răzvan-Gabriel Popa  Cristian G. Panaiotu  Alexandru Szakács  Zoltán Pécskay 《Bulletin of Volcanology》2016,78(10):69

  相似文献   

Numerical modelling of coastal inundation from Cascadia Subduction Zone tsunamis and implications for coastal communities on western Vancouver Island,Canada     

Takabatake  Tomoyuki  St-Germain  Philippe  Nistor  Ioan  Stolle  Jacob  Shibayama  Tomoya 《Natural Hazards》2019,98(1):267-291

Natural Hazards - In the present study, numerical simulations were conducted to estimate the spatio-temporal characteristics of tsunami inundation for municipalities on Vancouver Island, Canada, as...  相似文献   

Multi‐kilometre long pathway of geofluids migration: Clues concerning an ophiolite serpentinization setting possibly responsible for the inferred abiotic provenance of methane in thermal water outflows of the South‐West Carpathians (Romania)     

Horia Mitrofan  Constantin Marin  Florina Chitea  Nicoleta Cadicheanu  Ioan Povar&#x;  Alin Tudorache  Daniela Elena Ioni&#x;&#x;  Mirela‐Adriana Anghelache 《地学学报》2021,33(1):56-73

Methane occurrences displaying signatures of a possible abiotic origin had previously been reported in the South‐West Carpathians (Romania). Such an accumulation, at Tisovi?a, was intercepted by a well drilled in an ophiolitic rocks massif, whereas in two other localities—situated tens of kilometres faraway—the concerned methane is released via thermal groundwater outflows that are apparently not associated with any ultramafic products. By using groundwater ionic compositions, corroborated with previously published isotopic (¹³C‐CH₄, ²H‐CH₄, ³He/⁴He) and molecular gas analyses, we assessed in more detail the conjectured abiotic provenance of methane, and quantitatively investigated the hypothesis of a progressive mixing between two, abiotic and thermogenic, methane end‐members. The corresponding geofluids behaviour was modelled by hypothesizing a “concealed” ophiolite serpentinization setting (largely similar to that at Tisovi?a), whose abiotic methane production was “diverted” towards remote discharges at ground surface, via a ~20‐km‐long flowpath supposedly generated by recently operating extensional tectonics.  相似文献