Search results for "Tectonic"
showing 10 items of 470 documents
Slab-triggered wet upwellings produce large volumes of melt: Insights into the destruction of the North China Craton
2018
Abstract Cratons have remained stable for billions of years, despite of ongoing mantle convection and plate tectonics. The North China Craton (NCC), however, is abnormal, as it has experienced a destruction event during the Mesozoic and Cenozoic which was accompanied by extensive magmatism. Several lines of evidence suggest that the (Paleo-)Pacific plate played an important role in this event. Yet, the geodynamic link between subduction and craton destruction remains poorly understood, and it is unclear why there is no systematic spatial and temporal variation of magmatism related to subduction. Here, we perform 2-D petrological-thermomechanical simulations to investigate the influence of s…
Cretaceous tectonic evolution of the Sava-Klepa Massif, Republic of North Macedonia – Results from calcite twin based automated paleostress analysis
2019
Abstract The Sava-Klepa Massif represents an approximately 5 × 2 km sized fault-bounded block of dominantly basaltic rocks located within the Sava-Zone, an important suture zone between the Eurasian (Europe) and Gondwana (Adria) continental plates in the Balkans. Its nature and tectonic evolution is controversial: It is either interpreted as a remnant of the youngest Tethyan oceanic realm left behind after the main closure in the Late Jurassic or as the delimiter of a diffuse tectonic boundary between Adria and Europe, which had already collided in the Late Jurassic and was dominantly controlled by transtensional tectonics during Cretaceous times. In order to strengthen one or the other mod…
A free plate surface and weak oceanic crust produce single-sided subduction on Earth
2012
[1] Earth’s lithosphere is characterized by the relative movement of almost rigid plates as part of global mantle convection. Subduction zones on present-day Earth are strongly asymmetric features composed of an overriding plate above a subducting plate that sinks into the mantle. While global self-consistent numerical models of mantle convection have reproduced some aspects of plate tectonics, the assumptions behind these models do not allow for realistic single-sided subduction. Here we demonstrate that the asymmetry of subduction results from two major features of terrestrial plates: (1) the presence of a free deformable upper surface and (2) the presence of weak hydrated crust atop subd…
Tectonics and seismicity of the Tindari Fault System, southern Italy: Crustal deformations at the transition between ongoing contractional and extens…
2006
[1] The Tindari Fault System (southern Tyrrhenian Sea, Italy) is a regional zone of brittle deformation located at the transition between ongoing contractional and extensional crustal compartments and lying above the western edge of a narrow subducting slab. Onshore structural data, an offshore seismic reflection profile, and earthquake data are analyzed to constrain the present geometry of the Tindari Fault System and its tectonic evolution since Neogene, including the present seismicity. Results show that this zone of deformation consists of a broad NNW trending system of faults including sets of right-lateral, left-lateral, and extensional faults as well as early strike-slip faults rewor…
Fluid escape structures in the north Sicily continental margin
2014
Abstract High resolution and multichannel seismic profiles coupled with multibeam echosounder (seafloor relief) data, acquired along the northern Sicily continental margin (southern Tyrrhenian Sea), document the occurrence of mound and pockmark features, revealing fluid escape processes. Along this margin, morphology of the high-gradient continental slope is irregular due to the presence of structural highs, slope failures and canyons, and is interrupted by flat areas at a mean depth of 1500 m. Seismostratigraphic analysis tools and methods were used to identify fluid escape structures and to work out a classification on the basis of their morpho-acoustic characteristics. The detailed 3D ba…
The effects of post-orogenic extension on different scales: an example from the Apennine-Maghrebide fold-and-thrust belt, SW Sicily
2003
Many structures produced under one single deformation regime, namely extensional, contractional or strike-slip, exhibit remarkable geometrical analogies when analysed at different scales. By contrast, field examples that illustrate the scale effects on structures resulting from superimposed deformations, which were produced under different tectonic regimes, are rare. Yet the change from contraction to extension is known to occur often in the most thickened portions of the continental crust. The Apennine–Maghrebide fold-and-thrust belt of Sicily shows many examples of post-orogenic extensional deformations. Composite structures, resulting from late normal faults that offset folds and thrusts…
Interference between shallow and deep-seated structures in the Sicilian fold and thrust belt.
2010
Abstract: The fold and thrust belt in western Sicily is characterized by the presence and interference of shallow and deep-seated compressional structures, which were generated and developed at different structural levels. The shallow structures consist of imbricated thrusts and asymmetric folds, with a typical wavelength of 2 km, involving relatively thin deep-water units. These units are superimposed on thick platform carbonate units, along a wide and originally almost flat floor thrust. The axial trend of the folds is variable, as multi-phase folding often occurred, producing a characteristic interference pattern, reflecting continuous variations of the apparent transport direction durin…
Exhumation of high-pressure granulites and the role of lower crustal advection in the North China Craton near Datong
1997
Granulites in the Datong-Huai'an area of North China are characterized by high P-T assemblages (14 16 kbar, -9OOY) that underwent decompression cooling to -7 kbar and -800°C during a 250&2400 Ma tectonic event. Nearly all structures in the grantilites developed during the retrograde exhumation history, and can be subdivided into: (1) the stratigraphically lower, 'lower structural domain' that is characterized by complex folding with 55-10 km wide domes surrounded by concentric troughs, preserving concentric lineation patterns; and (2) the stratigraphically higher 'upper structural domain' that is characterized by a planar gneissic foliation, upright folds and a constant, shallowly SW-plungi…
Focused and diffuse effluxes of CO2 from mud volcanoes and mofettes south of Mt. Etna (Italy).
2007
Abstract Several sites with anomalous emissions of carbon dioxide were investigated in the region south of Mt. Etna volcano in order to assess the types of emission (focused and/or diffuse), their surface extension and the total output of CO 2 . Most of the studied emissions are located on the southwest boundary of Mt. Etna, near the town of Paterno. They consist of three mud volcanoes (known as Salinelle), one spring with bubbling gas (Acqua Grassa) and one area of diffuse degassing (Pescheria). Another site (Naftia Lake) with remarkable gas emissions (bubbling gas into a lake as well as adjacent areas of diffuse soil degassing) is located further southwest of Mt. Etna in an area of extinc…
Rejuvenation and erosion of the cratonic lithosphere
2008
Cratons are ancient continental nuclei that have resisted significant fragmentation for almost two billion years. Yet, many cratons also experience phases of instability in the form of erosion and rejuvenation of their thick lithospheric mantle keels. Melting governed by redox processes as well as small-scale convection play a key role in triggering such instability. Cratons are the ancient cores of continents, characterized by tectonic inactivity, a thick mantle lithosphere and low heat flow. Although stable as tectonically independent units for at least the past 2 billion years, cratons have experienced episodic rejuvenation events throughout their history. The lower part of the lithosphe…