Articoli di riviste: "Crustal tectonics"

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Hawkesworth, Chris J., Peter A. Cawood e Bruno Dhuime. "Tectonics and crustal evolution". GSA Today 26, n. 09 (16 agosto 2016): 4–11. http://dx.doi.org/10.1130/gsatg272a.1.

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Mueller, D. "Plate tectonics and crustal evolution". Eos, Transactions American Geophysical Union 79, n. 18 (1998): 220. http://dx.doi.org/10.1029/98eo00164.

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Horscroft, Timothy J. "Plate tectonics and crustal evolution". Earth-Science Reviews 42, n. 4 (novembre 1997): 276–77. http://dx.doi.org/10.1016/s0012-8252(97)81863-6.

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Clemens, J. D. "Plate tectonics and crustal evolution". Journal of Structural Geology 12, n. 3 (gennaio 1990): 400–401. http://dx.doi.org/10.1016/0191-8141(90)90028-w.

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Fyfe, W. S. "Fluids, tectonics and crustal deformation". Tectonophysics 119, n. 1-4 (ottobre 1985): 29–36. http://dx.doi.org/10.1016/0040-1951(85)90031-9.

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SLEMMONS, D. B. "Crustal Extension: Continental Extensional Tectonics." Science 239, n. 4844 (4 marzo 1988): 1185. http://dx.doi.org/10.1126/science.239.4844.1185.

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Yang-shen, Shi, Yang Shu-feng, Guo Ling-zhi e Dong Huo-gen. "Crustal genesis and plate tectonics". Tectonophysics 187, n. 1-3 (febbraio 1991): 277–84. http://dx.doi.org/10.1016/0040-1951(91)90424-q.

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Singh, Vinod K. "Geology, Geomorphology and Tectonics of India: Introduction". Journal of Geoscience, Engineering, Environment, and Technology 4, n. 2-2 (25 luglio 2019): 1. http://dx.doi.org/10.25299/jgeet.2019.4.2-2.2447.

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The earth crustal growth since its formation still need in depth research is the conclusion of the three International Conferences on Precambrian Continental Growth and Tectonism, in 2005, 2009 and 2013, organised at the Institute of Earth Sciences of Bundelkhand University, Jhansi, India and its proceedings have valuable source for advance research published the great ideas and achievements from scientists (Chandra et al. 2007; Singh and Chandra, 2011 and Singh et al., 2015). Therefore, this thematic issue planned for consider of crustal growth and tectonic evolution of Indian shield which include 7 research articles on geodynamic evolution of earth, geomorphology, structural, petrologic, isotopic, tectonic, and geochemistry investigations related to the Indian shield and its economic importance (Figure 1).

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Singh, Vinod K., Ram Chandra, Asish R. Basu, Surendra P. Verma e Tapas K. Biswal. "Precambrian crustal growth and tectonics: introduction". International Geology Review 57, n. 11-12 (20 maggio 2015): v—viii. http://dx.doi.org/10.1080/00206814.2015.1029542.

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Nebel, O., F. A. Capitanio, J. F. Moyen, R. F. Weinberg, F. Clos, Y. J. Nebel-Jacobsen e P. A. Cawood. "When crust comes of age: on the chemical evolution of Archaean, felsic continental crust by crustal drip tectonics". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 376, n. 2132 (ottobre 2018): 20180103. http://dx.doi.org/10.1098/rsta.2018.0103.

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The secular evolution of the Earth's crust is marked by a profound change in average crustal chemistry between 3.2 and 2.5 Ga. A key marker for this change is the transition from Archaean sodic granitoid intrusions of the tonalite–trondhjemite–granodiorite (TTG) series to potassic (K) granitic suites, akin (but not identical) to I-type granites that today are associated with subduction zones. It remains poorly constrained as to how and why this change was initiated and if it holds clues about the geodynamic transition from a pre-plate tectonic mode, often referred to as stagnant lid, to mobile plate tectonics. Here, we combine a series of proposed mechanisms for Archaean crustal geodynamics in a single model to explain the observed change in granitoid chemistry. Numeric modelling indicates that upper mantle convection drives crustal flow and subsidence, leading to profound diversity in lithospheric thickness with thin versus thick proto-plates. When convecting asthenospheric mantle interacts with lower lithosphere, scattered crustal drips are created. Under increasing P-T conditions, partial melting of hydrated meta-basalt within these drips produces felsic melts that intrude the overlying crust to form TTG. Dome structures, in which these melts can be preserved, are a positive diapiric expression of these negative drips. Transitional TTG with elevated K mark a second evolutionary stage, and are blends of subsided and remelted older TTG forming K-rich melts and new TTG melts. Ascending TTG-derived melts from asymmetric drips interact with the asthenospheric mantle to form hot, high-Mg sanukitoid. These melts are small in volume, predominantly underplated, and their heat triggered melting of lower crustal successions to form higher-K granites. Importantly, this evolution operates as a disseminated process in space and time over hundreds of millions of years (greater than 200 Ma) in all cratons. This focused ageing of the crust implies that compiled geochemical data can only broadly reflect geodynamic changes on a global or even craton-wide scale. The observed change in crustal chemistry does mark the lead up to but not the initiation of modern-style subduction. This article is part of a discussion meeting issue ‘Earth dynamics and the development of plate tectonics’.

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Le Roy, Charlotte, e Claude Rangin. "Cenozoic crustal deformation of the offshore Burgos basin region (NE Gulf of Mexico). A new interpretation of deep penetration multichannel seismic reflection lines". Bulletin de la Société Géologique de France 179, n. 2 (15 marzo 2008): 161–74. http://dx.doi.org/10.2113/gssgfbull.179.2.161.

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Abstract Along northeastern Mexico close to the Texas-Mexico border, the Burgos basin and its extension offshore was developed and deformed from the Paleocene up to Present time. This is a key triple junction between the sub meridian dextral transtensive coastal plain of the Gulf of Mexico extending far to the south in Mexico, the NE Corsair fault zone offshore and the sinistral Rio Bravo fault zone, a reactivated segment of the Texas lineament. Offshore NE Mexico, in the main study area covered by available seismic profiles, we have evidenced below the main well known gravitational décollement level (5 to 7 s twtt → 6 to 8 km) a Cenozoic deep-rooted deformation outlined by a N010° W trending deep-seated reverse fault zone and crustal folding down to the Moho (11 s twtt → ~ 20 km). Based on extensive offshore 2D industrial multi-channel seismic reflection surveys, deep exploration wells and gravimetric data, we focus our study on the deep crustal fabric and its effects on the gravitational tectonics in the upper sedimentary layers: submeridian crustal transtensional normal faults and open folding of the identified Mesozoic basement were interpreted as Cenozoic buckling of the crust during a major phase of oblique crustal extension. This deformation has probably enhanced gravity sliding along N030° growth-faults related to salt withdrawal and halokinesis in the offshore Burgos basin. We have tentatively made a link between this crustal deformation episode and the Neogene tectonic inversion of the Laramide foredeep basin of the Sierra Madre Oriental. The latter is still affected by crustal strike slip faulting associated with basaltic volcanism observed into the gulf coastal plain. This study favours a dominant crustal Cenozoic tectonic activity along the gulf margin without any clear evidence of Mesozoic tectonic reactivation. We propose that the large gravity collapse of the gulf margin was triggered by subsequent crustal deformation.

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Sleep, Norman H. "Self-Organization of Crustal Faulting and Tectonics". International Geology Review 44, n. 1 (gennaio 2002): 83–96. http://dx.doi.org/10.2747/0020-6814.44.1.83.

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Coney, P. J., e D. L. Jones. "Accretion tectonics and crustal structure in Alaska". Tectonophysics 119, n. 1-4 (ottobre 1985): 265–83. http://dx.doi.org/10.1016/0040-1951(85)90042-3.

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Urrutia-Fucugauchi, Jaime. "Tectonics, magmatism and crustal structure of Mexico". Geofísica Internacional 32, n. 3 (1 luglio 1993): 393–96. http://dx.doi.org/10.22201/igeof.00167169p.1993.32.3.1394.

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978 / 5.000 Resultados de traducción Desde su establecimiento y posterior desarrollo en la década de 1980-1989, el Programa Internacional de Litósfera (ILP) ha sido una importante adición a la investigación internacional en ciencias de la tierra, habiendo llevado a cabo un programa ambicioso y promovido numerosas iniciativas. La creciente conciencia de los ciclos globales, los mecanismos de retroalimentación, los procesos no lineales, etc. han llevado al surgimiento de programas como el Geosfera-Biosfera (IGBP), el Cambio Global y los Programas del Sistema Terrestre. Muchos fenómenos en los diversos campos que vinculan los diversos sistemas terrestres, que anteriormente se habían estudiado como entidades separadas de la geosfera, la biosfera, la hidrosfera y la atmósfera, ahora se están investigando dentro de un marco integrado. La conjunción de ciencias terrestres, atmosféricas, oceánicas y biológicas sólidas que incluyen: geofísica, geología, geoquímica, ciencias atmosféricas, biología, ecología, ciencias ambientales, oceanografía y muchos otros campos proporcionará un paradigma global.doi: sin doi

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Korenaga, Jun. "Crustal evolution and mantle dynamics through Earth history". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 376, n. 2132 (ottobre 2018): 20170408. http://dx.doi.org/10.1098/rsta.2017.0408.

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Resolving the modes of mantle convection through Earth history, i.e. when plate tectonics started and what kind of mantle dynamics reigned before, is essential to the understanding of the evolution of the whole Earth system, because plate tectonics influences almost all aspects of modern geological processes. This is a challenging problem because plate tectonics continuously rejuvenates Earth's surface on a time scale of about 100 Myr, destroying evidence for its past operation. It thus becomes essential to exploit indirect evidence preserved in the buoyant continental crust, part of which has survived over billions of years. This contribution starts with an in-depth review of existing models for continental growth. Growth models proposed so far can be categorized into three types: crust-based, mantle-based and other less direct inferences, and the first two types are particularly important as their difference reflects the extent of crustal recycling, which can be related to subduction. Then, a theoretical basis for a change in the mode of mantle convection in the Precambrian is reviewed, along with a critical appraisal of some popular notions for early Earth dynamics. By combining available geological and geochemical observations with geodynamical considerations, a tentative hypothesis is presented for the evolution of mantle dynamics and its relation to surface environment; the early onset of plate tectonics and gradual mantle hydration are responsible not only for the formation of continental crust but also for its preservation as well as its emergence above sea level. Our current understanding of various material properties and elementary processes is still too premature to build a testable, quantitative model for this hypothesis, but such modelling efforts could potentially transform the nature of the data-starved early Earth research by quantifying the extent of preservation bias.This article is part of a discussion meeting issue ‘Earth dynamics and the development of plate tectonics’.

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Mohan, M. Ram, Ajay Dev Asokan e Simon A. Wilde. "Crustal growth of the Eastern Dharwar Craton: a Neoarchean collisional orogeny?" Geological Society, London, Special Publications 489, n. 1 (11 dicembre 2019): 51–77. http://dx.doi.org/10.1144/sp489-2019-108.

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AbstractThe Eastern Dharwar Craton (EDC) is predominantly made of Neoarchean potassic granitoids with subordinate linear greenstone belts. Available geochemical and isotopic systematics of these granitoids suggest variations in the source and petrogenetic mechanisms. By compiling the available geochemical data, these granitoids can be classified into four groups, namely: TTGs (tonalite–trondhjemite–granodiorite); sanukitoids; biotite and two-mica granites; and hybrid granites. This classification scheme is in line with the global classification of Neoarchean granites, and enables the sources and petrogenetic mechanisms of these variants to be distinguished. Available geochemical, isotopic and geochronological datasets of these granitoids are integrated and the existing tectonic models for the Neoarchean EDC are reviewed. The variability of the EDC granitoids is ascribed to crustal reworking associated with the collision of two continental blocks. The tectonomagmatic evolution of the EDC is analogous to the development of the Himalayan Orogeny. Based on the evolutionary history of the Dharwar Craton, it can be concluded that convergent margin tectonics were operational in the Indian Shield from at least c. 3.3 Ga and continued into the Phanerozoic. However, the nature and style of plate tectonics could be different with time.

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Castellanos, Jorge C., Jonathan Perry-Houts, Robert W. Clayton, YoungHee Kim, A. Christian Stanciu, Bart Niday e Eugene Humphreys. "Seismic anisotropy reveals crustal flow driven by mantle vertical loading in the Pacific NW". Science Advances 6, n. 28 (luglio 2020): eabb0476. http://dx.doi.org/10.1126/sciadv.abb0476.

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Buoyancy anomalies within Earth’s mantle create large convective currents that are thought to control the evolution of the lithosphere. While tectonic plate motions provide evidence for this relation, the mechanism by which mantle processes influence near-surface tectonics remains elusive. Here, we present an azimuthal anisotropy model for the Pacific Northwest crust that strongly correlates with high-velocity structures in the underlying mantle but shows no association with the regional mantle flow field. We suggest that the crustal anisotropy is decoupled from horizontal basal tractions and, instead, created by upper mantle vertical loading, which generates pressure gradients that drive channelized flow in the mid-lower crust. We then demonstrate the interplay between mantle heterogeneities and lithosphere dynamics by predicting the viscous crustal flow that is driven by local buoyancy sources within the upper mantle. Our findings reveal how mantle vertical load distribution can actively control crustal deformation on a scale of several hundred kilometers.

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Keller, C. Brenhin, e T. Mark Harrison. "Constraining crustal silica on ancient Earth". Proceedings of the National Academy of Sciences 117, n. 35 (17 agosto 2020): 21101–7. http://dx.doi.org/10.1073/pnas.2009431117.

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Accurately quantifying the composition of continental crust on Hadean and Archean Earth is critical to our understanding of the physiography, tectonics, and climate of our planet at the dawn of life. One longstanding paradigm involves the growth of a relatively mafic planetary crust over the first 1 to 2 billion years of Earth history, implying a lack of modern plate tectonics and a paucity of subaerial crust, and consequently lacking an efficient mechanism to regulate climate. Others have proposed a more uniformitarian view in which Archean and Hadean continents were only slightly more mafic than at present. Apart from complications in assessing early crustal composition introduced by crustal preservation and sampling biases, effects such as the secular cooling of Earth’s mantle and the biologically driven oxidation of Earth’s atmosphere have not been fully investigated. We find that the former complicates efforts to infer crustal silica from compatible or incompatible element abundances, while the latter undermines estimates of crustal silica content inferred from terrigenous sediments. Accounting for these complications, we find that the data are most parsimoniously explained by a model with nearly constant crustal silica since at least the early Archean.

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Heron, Philip J., Russell N. Pysklywec e Randell Stephenson. "Exploring the theory of plate tectonics: the role of mantle lithosphere structure". Geological Society, London, Special Publications 470, n. 1 (1 marzo 2018): 137–55. http://dx.doi.org/10.1144/sp470.7.

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AbstractThis review of the role of the mantle lithosphere in plate tectonic processes collates a wide range of recent studies from seismology and numerical modelling. A continually growing catalogue of deep geophysical imaging has illuminated the mantle lithosphere and generated new interpretations of how the lithosphere evolves. We review current ideas about the role of continental mantle lithosphere in plate tectonic processes. Evidence seems to be growing that scarring in the continental mantle lithosphere is ubiquitous, which implies a reassessment of the widely held view that it is the inheritance of crustal structure only (rather than the lithosphere as a whole) that is most important in the conventional theory of plate tectonics (e.g. the Wilson cycle). Recent studies have interpreted mantle lithosphere heterogeneities to be pre-existing structures and, as such, linked to the Wilson cycle and inheritance. We consider the current fundamental questions in the role of the mantle lithosphere in causing tectonic deformation, reviewing recent results and highlighting the potential of the deep lithosphere in infiltrating every aspect of plate tectonics processes.

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Phillips, Thomas B., Christopher A. L. Jackson, Rebecca E. Bell e Oliver B. Duffy. "Oblique reactivation of lithosphere-scale lineaments controls rift physiography – the upper-crustal expression of the Sorgenfrei–Tornquist Zone, offshore southern Norway". Solid Earth 9, n. 2 (9 aprile 2018): 403–29. http://dx.doi.org/10.5194/se-9-403-2018.

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Abstract. Pre-existing structures within sub-crustal lithosphere may localise stresses during subsequent tectonic events, resulting in complex fault systems at upper-crustal levels. As these sub-crustal structures are difficult to resolve at great depths, the evolution of kinematically and perhaps geometrically linked upper-crustal fault populations can offer insights into their deformation history, including when and how they reactivate and accommodate stresses during later tectonic events. In this study, we use borehole-constrained 2-D and 3-D seismic reflection data to investigate the structural development of the Farsund Basin, offshore southern Norway. We use throw–length (T-x) analysis and fault displacement backstripping techniques to determine the geometric and kinematic evolution of N–S- and E–W-striking upper-crustal fault populations during the multiphase evolution of the Farsund Basin. N–S-striking faults were active during the Triassic, prior to a period of sinistral strike-slip activity along E–W-striking faults during the Early Jurassic, which represented a hitherto undocumented phase of activity in this area. These E–W-striking upper-crustal faults are later obliquely reactivated under a dextral stress regime during the Early Cretaceous, with new faults also propagating away from pre-existing ones, representing a switch to a predominantly dextral sense of motion. The E–W faults within the Farsund Basin are interpreted to extend through the crust to the Moho and link with the Sorgenfrei–Tornquist Zone, a lithosphere-scale lineament, identified within the sub-crustal lithosphere, that extends > 1000 km across central Europe. Based on this geometric linkage, we infer that the E–W-striking faults represent the upper-crustal component of the Sorgenfrei–Tornquist Zone and that the Sorgenfrei–Tornquist Zone represents a long-lived lithosphere-scale lineament that is periodically reactivated throughout its protracted geological history. The upper-crustal component of the lineament is reactivated in a range of tectonic styles, including both sinistral and dextral strike-slip motions, with the geometry and kinematics of these faults often inconsistent with what may otherwise be inferred from regional tectonics alone. Understanding these different styles of reactivation not only allows us to better understand the influence of sub-crustal lithospheric structure on rifting but also offers insights into the prevailing stress field during regional tectonic events.

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Dey, Sukanta, e Jean-François Moyen. "Archean granitoids of India: windows into early Earth tectonics – an introduction". Geological Society, London, Special Publications 489, n. 1 (2020): 1–13. http://dx.doi.org/10.1144/sp489-2020-155.

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AbstractGranitoids form the dominant component of Archean cratons. They are generated by partial melting of diverse crustal and mantle sources and subsequent differentiation of the primary magmas, and are formed through a variety of geodynamic processes. Granitoids, therefore, are important archives for early Earth lithospheric evolution. Peninsular India comprises five cratonic blocks bordered by mobile belts. The cratons that stabilized during the Paleoarchean–Mesoarchean (Singhbhum and Western Dharwar) recorded mostly diapirism or sagduction tectonics. Conversely, cratons that stabilized during the late Neoarchean (Eastern Dharwar, Bundelkhand, Bastar and Aravalli) show evidence consistent with terrane accretion–collision in a convergent setting. Thus, the Indian cratons provide testimony to a transition from a dominantly pre-plate tectonic regime in the Paleoarchean–Mesoarchean to a plate-tectonic-like regime in the late Neoarchean. Despite this diversity, all five cratons had a similar petrological evolution with a long period (250–850 myr) of episodic tonalite–trondhjemite–granodiorite (TTG) magmatism followed by a shorter period (30–100 myr) of granitoid diversification (sanukitoid, K-rich anatectic granite and A-type granite) with signatures of input from both mantle and crust. The contributions of this Special Publication cover diverse granitoid-related themes, highlighting the potential of Indian cratons in addressing global issues of Archean crustal evolution.

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Capitanio, F. A., O. Nebel, P. A. Cawood, R. F. Weinberg e P. Chowdhury. "Reconciling thermal regimes and tectonics of the early Earth". Geology 47, n. 10 (20 agosto 2019): 923–27. http://dx.doi.org/10.1130/g46239.1.

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Abstract Thermomechanical models of mantle convection and melting in an inferred hotter Archean Earth show the emergence of pressure-temperature (P-T) regimes that resemble present-day plate tectonic environments yet developed within a non–plate tectonics regime. The models’ P-T gradients are compatible with those inferred from evolving tonalite-trondhjemite-granodiorite series rocks and the paired metamorphic belt record, supporting the feasibility of divergent and convergent tectonics within a mobilized, yet laterally continuous, lithospheric lid. “Hot” P-T gradients of 10–20 °C km–1 form along asymmetric lithospheric drips, then migrate to areas of deep lithospheric downwelling within ∼300–500 m.y., where they are overprinted by high-pressure warm and, later, cold geothermal signatures, up to ∼8 °C km–1. Comparisons with the crustal production and reworking record suggest that this regime emerged in the Hadean.

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Valenti, Vera, Raimondo Catalano, Pingsheng Wei e Shujiang Wang. "Layered lower crust and mantle reflectivity as imaged by a re-processed crustal seismic profile from Sicily in the central Mediterranean". Bulletin de la Société Géologique de France 186, n. 4-5 (1 luglio 2015): 257–72. http://dx.doi.org/10.2113/gssgfbull.186.4-5.257.

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Abstract Though Sicily is a key area for understanding the central Mediterranean tectonics, a number of questions on its dynamics remains open due to the lack of detailed data on the lithospheric structure. Deep reflectivity images of the African lithosphere, beneath Sicily, have been derived from the re-processing of the crustal seismic reflection stack (SI.RI.PRO. Project). Of specific interest was the imaging, beneath central-southern Sicily, of a thinned crust with a reflective, “layered” pattern for the lower crust that differs from the one, thicker and sub-transparent, of the northern-central sector. Brittle deformation in the upper crystalline crust along a low-angle normal fault and sub-horizontal sub-Moho events are the main features, spatially associated with the “layered”, attenuated lower crust. Geological implications, which are related to the above-mentioned crustal characters, that allow us to suppose two combined hypotheses (the first suggesting that the crustal features derive from the effects of Permian and Mesozoic rifting cycles, the second connecting the crustal thinning to the latest Pliocene-Pleistocene volcanic activity and tectonics), are here discussed. The imaging of the Moho patterns and the crustal/sub-crustal reflectivity characteristics, here illustrated for the first time, could provide constraints for the geodynamic processes governing this area where an interaction between African and Tyrrhenian European plates occurs.

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Elliott, J. R., M. de Michele e H. K. Gupta. "Earth Observation for Crustal Tectonics and Earthquake Hazards". Surveys in Geophysics 41, n. 6 (28 agosto 2020): 1355–89. http://dx.doi.org/10.1007/s10712-020-09608-2.

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Abstract In this paper, we illustrate some of the current methods for the exploitation of data from Earth Observing satellites to measure and understand earthquakes and shallow crustal tectonics. The aim of applying such methods to Earth Observation data is to improve our knowledge of the active fault sources that generate earthquake shaking hazards. We provide examples of the use of Earth Observation, including the measurement and modelling of earthquake deformation processes and the earthquake cycle using both radar and optical imagery. We also highlight the importance of combining these orbiting satellite datasets with airborne, in situ and ground-based geophysical measurements to fully characterise the spatial and timescale of temporal scales of the triggering of earthquakes from an example of surface water loading. Finally, we conclude with an outlook on the anticipated shift from the more established method of observing earthquakes to the systematic measurement of the longer-term accumulation of crustal strain.

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Monger, James W. H. "Canadian Cordilleran tectonics: from geosynclines to crustal collage". Canadian Journal of Earth Sciences 30, n. 2 (1 febbraio 1993): 209–31. http://dx.doi.org/10.1139/e93-019.

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The major contributions by the Geological Survey of Canada in the Canadian Cordillera—systematic mapping and definition of the regional geological framework—led directly to tectonic syntheses that attempted to explain its origin. From the late 1800's until the 1960's, Cordilleran mountain building was viewed as the end result of geosynclinal deposition. Early workers felt that a connection existed between mountain building and the Pacific basin, but its nature was never clear because little was known about ocean basins and their relationships to continental margins. In the 1950's, the nature of the oceanic lithosphere and ocean–continent relationships became better known; the knowledge led to formulation of the plate-tectonic hypothesis in the 1960's, a time fortuitously coinciding with completion, by the Survey, of most of the regional geological mapping (scale 1: 250 000). Geosynclinal rock units were reinterpreted in terms of their possible modern analogues (oceanic, island-arc, continental shelf – slope assemblages) and paleontological and paleomagnetic studies were used to support a mobilistic view of Cordilleran paleogeography, rather than the relatively fixed paleogeography tacitly assumed in earlier interpretations. In contrast with deterministic geosynclinal theory, it was recognized that plate-tectonic processes applied over a long time have enormous potential to create disorder; the result is an orogenic collage to be analyzed as a series of time – space events each of whose geodynamic settings may have been very different from one another. This aspect is especially important in the long-lived Cordillera, which was initiated as a continent–ocean boundary in latest Proterozoic time, evolved through the entire Phanerozoic, and today is a convergent-transform continen – ocean plate margin. Interactions between various oceanic plates and the North American plate, shown by the Cordilleran record of accretionary complexes, as well as results of possible arc–continent collisions and continental margin arc magmatism, formed new continental crust.

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Gapais, Denis, Jean-Pierre Brun, Charles Gumiaux, Florence Cagnard, Gilles Ruffet e Christian Le Carlier De Veslud. "Extensional tectonics in the Hercynian Armorican belt (France). An overview". Bulletin de la Société Géologique de France 186, n. 2-3 (2015): 117–29. http://dx.doi.org/10.2113/gssgfbull.186.2-3.117.

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Abstract A synthesis of existing geological, structural and geophysical data shows that the south Armorican Hercynian belt was marked by syn-convergence crustal thinning and dextral wrenching that were in part coeval in late Carboniferous times. Our kinematic model is further supported by new structural data and 40Ar/39Ar ages on synkinematic leucogranites. Extension and strike-slip followed earlier crustal thickening and exhumation of high-pressure metamorphic units in late Devonian-early Carboniferous times. Crustal extension led to the development of core complexes cored by migmatites and crust-derived granite laccoliths. At this time, the South Armorican shear zone acted as a transfer zone separating the extending domain of South Brittany from the non-extending domain of Central Brittany submitted to dextral wrenching. The overall structural pattern and attached kinematics are compared with recent numerical models and illustrated by a 3D interpretative model that integrates geological and deep seismic reflection data (ARMOR 2 profile).

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Rangin, Claude, Xavier Le Pichon, Juventino Martinez-Reyes e Mario Aranda-Garcia. "GRAVITY TECTONICS AND PLATE MOTIONS". Bulletin de la Société Géologique de France 179, n. 2 (15 marzo 2008): 107–16. http://dx.doi.org/10.2113/gssgfbull.179.2.107.

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Abstract This is an introduction to the series of papers presented in this volume that concerns the Cenozoic tectonics of the western margin of the Gulf of Mexico, from Texas in the north to the Veracruz area into the south. These combined offshore-onshore structural studies investigate the links between surperficial gravity slidings and deep crustal flow within the complex geodynamic framework of Mexico, located at the junction between the North America, Carribean and Pacific plates (including the earlier Farallon plate).

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28

Jolivet, Laurent, Thierry Baudin, Sylvain Calassou, Sébastien Chevrot, Mary Ford, Benoit Issautier, Eric Lasseur et al. "Geodynamic evolution of a wide plate boundary in the Western Mediterranean, near-field versus far-field interactions". BSGF - Earth Sciences Bulletin 192 (2021): 48. http://dx.doi.org/10.1051/bsgf/2021043.

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The present-day tectonic setting of the Western Mediterranean region, from the Pyrénées to the Betics and from the Alps to the Atlas, results from a complex 3-D geodynamic evolution involving the interactions between the Africa, Eurasia and Iberia plates and asthenospheric mantle dynamics underneath. In this paper, we review the main tectonic events recorded in this region since the Early Cretaceous and discuss the respective effects of far-field and near-field contributions, in order to unravel the origin of forces controlling crustal deformation. The respective contributions of mantle-scale, plate-scale and local processes in the succession of tectonic stages are discussed. Three periods can be distinguished: (1) the first period (Tethyan Tectonics), from 110 to 35 Ma, spans the main evolution of the Pyrenean orogen and the early evolution of the Betics, from rifting to maximum shortening. The rifting between Iberia and Europe and the subsequent progressive formation of new compressional plate boundaries in the Pyrénées and the Betics, as well as the compression recorded all the way to the North Sea, are placed in the large-scale framework of the African and Eurasian plates carried by large-scale mantle convection; (2) the second period (Mediterranean Tectonics), from 32 to 8 Ma, corresponds to a first-order change in subduction dynamics. It is most typically Mediterranean with a dominant contribution of slab retreat and associated mantle flow in crustal deformation. Mountain building and back-arc basin opening are controlled by retreating and tearing slabs and associated mantle flow at depth. The 3-D interactions between the different pieces of retreating slabs are complex and the crust accommodates the mantle flow underneath in various ways, including the formation of metamorphic core complexes and transfer fault zones; (3) the third period (Late-Mediterranean Tectonics) runs from 8 Ma to the Present. It corresponds to a new drastic change in the tectonic regime characterized by the resumption of N-S compression along the southern plate boundary and a propagation of compression toward the north. The respective effects of stress transmission through the lithospheric stress-guide and lithosphere-asthenosphere interactions are discussed throughout this period.

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29

Uchide, Takahiko. "Focal mechanisms of small earthquakes beneath the Japanese islands based on first-motion polarities picked using deep learning". Geophysical Journal International 223, n. 3 (26 agosto 2020): 1658–71. http://dx.doi.org/10.1093/gji/ggaa401.

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SUMMARY Knowledge of crustal stress fields is essential for understanding tectonics and earthquake generation. One approach for estimating the crustal stress field is based on the focal mechanisms of earthquakes. This study investigated the focal mechanisms of approximately 110 000 microearthquakes in the area of the Japanese islands that occurred at a depth shallower than 20 km, based on the first-motion polarities picked by a simple neural network model. The model was first trained using a data set of mainly moderate to large earthquakes throughout Japan. Following on, the model was re-trained using a data set of microearthquakes in two regions of Japan. The threshold of the confidence score from the neural network model was chosen to maximize the overall quality of the focal mechanism solutions. The P- and T-axes of the numerous focal mechanism solutions provided more detailed distributions of the crustal stress field. For example, in the Chugoku region, small differences were observed in the trend of P-axes azimuths between the northern and southern areas, spatially corresponding to geodetic observations. The results of this study are useful for revealing the crustal stress field, and, as such, for assessing past and current tectonic activities and potential future earthquake generation.

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30

Thybo, Hans. "Crustal structure and tectonic evolution of the Tornquist Fan region as revealed by geophysical methods". Bulletin of the Geological Society of Denmark 46 (3 maggio 1999): 145–60. http://dx.doi.org/10.37570/bgsd-1999-46-12.

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Crustal structure derived primarily from geophysical investigations reveals features that may be related to the complex tectonic evolution of the Tornquist Fan region. This northwestwards widening splay of Late Carboniferous – Early Permian fault zones in the Danish region emanates from the Teisseyre-Tornquist Zone in northern Poland. Seismic reflections and velocity anomalies image collisional fault zones that formed during the Proterozoic and Palaeozoic amalgamation of the crust. Re-equilibration of Moho appears to have taken place before late Palaeozoic rifting and magmatism initiated the main phase of basin formation that continued into the Mesozoic. The resulting, strong Moho topography, with variation between depths of 26 and 48 km, has been practically “frozen in” since then, although the late Cretaceous – early Cenozoic inversion tectonics may have formed a crustal keel underneath part of the Sorgenfrei-Tornquist Zone which cuts across the Proterozoic crust of the Tornquist Fan region.

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31

Dessa, Jean-Xavier, Marie-Odile Beslier, Laure Schenini, Nicolas Chamot-Rooke, Nicolà Corradi, Matthias Delescluse, Jacques Déverchère et al. "Seismic Exploration of the Deep Structure and Seismogenic Faults in the Ligurian Sea by Joint Multi Channel and Ocean Bottom Seismic Acquisitions: Preliminary Results of the SEFASILS Cruise". Geosciences 10, n. 3 (18 marzo 2020): 108. http://dx.doi.org/10.3390/geosciences10030108.

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The north Ligurian margin is a complex geological area in many ways. It has witnessed several phases of highly contrasting deformation styles, at both crustal scale and that of shallower cover tectonics, simultaneously or in quick succession, and with significant spatial variability. This complex interplay is mirrored in the resulting intricate structures that make it hard to identify active faults responsible for both, the significant seismicity observed, and the tectonic inversion undergone by the margin, identified at longer time scales on morphostructural grounds. We present here the first preliminary results of the leg 1 of SEFASILS cruise, conducted in 2018 offshore Monaco, in an effort to answer these questions by means of modern deep seismic acquisitions, using multichannel reflection and wide-angle sea-bottom records. Some first interpretations are provided and point towards an active basement deformation that focuses at the limits between main crustal domains.

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32

Yang, Chengwei, Chenghu Wang, Mingruo Jiao, Yujiang Li e Pu Wang. "Multisource stress data constraints on Cretaceous—present regional tectonic stress field evolution in the southern Jinzhou area, North China Craton". Journal of Geophysics and Engineering 18, n. 6 (dicembre 2021): 1007–21. http://dx.doi.org/10.1093/jge/gxab068.

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Abstract Regional tectonic stress fields are key crustal stress elements that drive tectonic movements and are associated with regional tectonics and geological resources. Regional tectonic stress field evolution of the Jinzhou area, located in the eastern block of the North China Craton (NCC), may provide a deeper understanding of tectonics of western Liaoning and the NCC. This work conducted borehole television, hydraulic fracturing and focal mechanism solutions to invert the paleo and present regional tectonic stress fields. Four groups of tensile fracture in the southern Jinzhou area were identified via borehole television, and their azimuths were NNW–SSE, NWW–SEE, nearly W–E and NE–SW in temporal order representing four stages of extensional tectonic events. Hydraulic fracturing and focal mechanism solutions showed that the stress status was normal fault and strike-slip, revealing that the southern Jinzhou area is undergoing NEE–SWW-oriented compression and nearly N–S-oriented extension in accordance with the strike-slip mechanism. From the Early Cretaceous to the present, the direction of the regional extensional stress in the southern Jinzhou area has evolved counterclockwise and sequentially from NNW–SSE to NWW–SEE, W–E, NE–SW and nearly N–S, and the regional tectonic mechanism has transited from extension to extension-strike-slip to strike-slip, leading to the current tectonic framework.

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33

Bercovici, David, Gerald Schubert e Yanick Ricard. "Abrupt tectonics and rapid slab detachment with grain damage". Proceedings of the National Academy of Sciences 112, n. 5 (20 gennaio 2015): 1287–91. http://dx.doi.org/10.1073/pnas.1415473112.

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A simple model for necking and detachment of subducting slabs is developed to include the coupling between grain-sensitive rheology and grain-size evolution with damage. Necking is triggered by thickened buoyant crust entrained into a subduction zone, in which case grain damage accelerates necking and allows for relatively rapid slab detachment, i.e., within 1 My, depending on the size of the crustal plug. Thick continental crustal plugs can cause rapid necking while smaller plugs characteristic of ocean plateaux cause slower necking; oceanic lithosphere with normal or slightly thickened crust subducts without necking. The model potentially explains how large plateaux or continental crust drawn into subduction zones can cause slab loss and rapid changes in plate motion and/or induce abrupt continental rebound.

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34

Brückl, E., M. Behm, K. Decker, M. Grad, A. Guterch, G. R. Keller e H. Thybo. "Crustal structure and active tectonics in the Eastern Alps". Tectonics 29, n. 2 (aprile 2010): n/a. http://dx.doi.org/10.1029/2009tc002491.

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35

Zelt, C. A., e D. J. White. "Crustal structure and tectonics of the southeastern Canadian Cordillera". Journal of Geophysical Research: Solid Earth 100, B12 (10 dicembre 1995): 24255–73. http://dx.doi.org/10.1029/95jb02632.

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36

Hashimoto, Manabu, e David D. Jackson. "Plate tectonics and crustal deformation around the Japanese Islands". Journal of Geophysical Research 98, B9 (1993): 16149. http://dx.doi.org/10.1029/93jb00444.

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37

Hall, Robert. "Australia–SE Asia collision: plate tectonics and crustal flow". Geological Society, London, Special Publications 355, n. 1 (2011): 75–109. http://dx.doi.org/10.1144/sp355.5.

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38

Sakellariou, D., J. Mascle e V. Lykousis. "Strike slip tectonics and transtensional deformation in the Aegean region and the Hellenic arc: Preliminary results". Bulletin of the Geological Society of Greece 47, n. 2 (24 gennaio 2017): 647. http://dx.doi.org/10.12681/bgsg.11098.

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Recently acquired offshore seismic and swath bathymetry data from the Hellenic Arc, the Ionian Sea and the South and North Aegean Sea, including the Hellenic Volcanic Arc and the Cyclades plateau, along with geological and tectonic data from Plio-Quaternary basins exposed on the Hellenic Arc indicate that strike slip tectonics has played a major role in the southwestward extension of the Aegean crustal block, the development of the offshore neotectonic basins and the spatial distribution of the volcanic activity along the Volcanic Arc. Transtensional deformation, accommodated by (sinistral or dextral) strike slip zones and related extensional structures, prevail throughout Plio-Quaternary, since the North Anatolian Fault broke westwards into the North Aegean. Incipient collision of the Hellenic Forearc south of Crete with the Libyan promontory and consequent lateral escape tectonics led to the segmentation of the Hellenic Arc in distinct blocks, which move southwestwards independently from each other and are bounded by strike slip faults.

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39

Gasparo Morticelli, Maurizio, Vera Valenti, Raimondo Catalano, Attilio Sulli, Mauro Agate, Giuseppe Avellone, Cinzia Albanese, Luca Basilone e Calogero Gugliotta. "Deep controls on foreland basin system evolution along the Sicilian fold and thrust belt". Bulletin de la Société Géologique de France 186, n. 4-5 (1 luglio 2015): 273–90. http://dx.doi.org/10.2113/gssgfbull.186.4-5.273.

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Abstract Neogene-Quaternary wedge-top-basins arose during the Sicilian fold and thrust belt (FTB) build-up. The infilling sedimentary successions are: i) middle-upper Miocene silicoclastics succession, accommodated on top of the accreted Sicilide and Numidian flysch nappes; ii) upper Miocene-lower Pliocene deepening-upwards sediments unconformably overlying the inner Meso-Cenozoic deep-water, Imerese and Sicanian thrust units; iii) Upper Pliocene-Quaternary coastal-open shelf deposits unconformably covering (in the outer sector of the FTB) a tectonic stack (Gela thrust system). These successions are characterized by a basal unconformity on the deformed substrate believed to be the depositional interface common both to the coeval wedge-top and foredeep basins. The tectono-sedimentary evolution of the syn-tectonic basins was controlled by the progressive deepening of the structural levels, which were active during the growing of the FTB. The palinspastic restoration of a crustal geological transect in central Sicily points to: i) the occurrence of two subsequent, basal main thrusts (MT1 and MT2) active during the Neogene-middle Pleistocene tectonic evolution, as well as ii) a decrease in slip- and shortening-rate, estimated for the later MT2 as compared to earlier MT1 basal main thrust. The foreland-basin system evolution recorded during these two steps suggests: – the regional lithofacies distribution, during late Tortonian-early Pliocene, accounted for a wide depozone including the Iblean plateau and its offshore;– a crucial change was recorded by the late Pliocene-Pleistocene wedge-top depozone, when the deeper basal main thrust (MT2) involved and thickened (in the inner sector of the FTB) the crystalline basement (thin- to thick-skinned thrust tectonics); this change influenced the depozones, progressively narrowing up to the present-day setting. As regards this general evolutionary framework, thin-skinned and thick-skinned thrust tectonics can be recognized in the Sicilian FTB evolution. The late Tortonian-early Pliocene, thin-skinned thrust tectonics include two main tectonic events, a “shallow-seated” Event 1 and a “deep-seated” Event 2, with the Pliocene-Pleistocene thick-skinned thrust tectonics representing a third tectonic event (Event 3).

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Jolivet, Laurent, Armel Menant, Camille Clerc, Pietro Sternai, Nicolas Bellahsen, Sylvie Leroy, Raphaël Pik, Martin Stab, Claudio Faccenna e Christian Gorini. "Extensional crustal tectonics and crust-mantle coupling, a view from the geological record". Earth-Science Reviews 185 (ottobre 2018): 1187–209. http://dx.doi.org/10.1016/j.earscirev.2018.09.010.

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41

White, D. J., S. B. Lucas, Z. Hajnal, A. G. Green, J. F. Lewry, W. Weber, A. H. Bailes, E. C. Syme e K. Ashton. "Paleo-Proterozoic thick-skinned tectonics: Lithoprobe seismic reflection results from the eastern Trans-Hudson Orogen". Canadian Journal of Earth Sciences 31, n. 3 (1 marzo 1994): 458–69. http://dx.doi.org/10.1139/e94-042.

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Abstract (sommario):

New seismic reflection data collected by Lithoprobe across the Trans-Hudson Orogen (Manitoba and Saskatchewan) provide striking images of juvenile paleo-Proterozoic arc rocks (Flin Flon and Kisseynew belts) juxtaposed against the deformed northwestern margin of the Archean Superior craton. Crustal imbrication on a scale imaged in few other orogens is observed within the Flin Flon Belt where a package of shallowly east-dipping reflections extends from the surface to 14 s. These reflections are attributed to middle to lower crustal arc rocks that appear to have been stacked below a major detachment that underlies the upper crustal rocks of the Flin Flon Belt. Surprisingly, the seismic images show the juvenile arc rocks dipping moderately eastward beneath the craton in apparent contradiction to existing tectonic models. Geological and geochronological evidence suggest that the observed crustal imbrication probably reflects late-collisional or postcollisional convergence rather than earlier oceanic subduction polarity. The east-dipping reflection fabric, marking a Hudsonian tectonic overprint, extends across the Superior Boundary Zone up to the Pikwitonei Granulite Belt where upper crustal reflections are west dipping. An east-dipping seismic boundary between these domains, which soles into the mid-crust, may represent a west-verging thrust fault along which the crust of the Archean Superior craton was uplifted.

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42

Vasconcelos, Bruno Rodrigo, Amarildo Salina Ruiz e João Batista de Matos. "Polyphase deformation and metamorphism of the Cuiabá group in the Poconé region (MT), Paraguay Fold and Thrust Belt: kinematic and tectonic implications". Brazilian Journal of Geology 45, n. 1 (marzo 2015): 51–63. http://dx.doi.org/10.1590/23174889201500010004.

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Several deformation models have been proposed for the Paraguay Belt, which primarily differ in the number of phases of deformation, direction of vergence and tectonic style. Structural features presented in this work indicate that the tectonics was dominated by low dip thrust sheets in an initial phase, followed by two progressive deformation phases. The first phase of deformation is characterized by a slate cleavage and axial plane of isoclinal recumbent folds with a NE axial direction, with a recrystallization of the minerals in the greenschist facies associated with horizontal shear zones with a top-to-the-SE sense of movement. The second stage shows vergence towards the NW, characterized by crenulation cleavage axial plane to F2 open folds over S0 and S1, locally associated with reverse faults. The third phase of deformation is characterized by subvertical faults and fractures with a NW direction showing sinistral movement, which are commonly filled by quartz veins. The collection of tectonic structures and metamorphic paragenesis described indicate that the most intense deformation at the deeper crustal level, greenschistfacies, occurred during F1, which accommodated significant crustal shortening through isoclinal recumbent folds and shear zones with low dip angles and hangwall movement to the SE, in a thin-skinned tectonic regime. The F2 deformation phase was less intense and had a brittle to ductile behavior that accommodated a slight shortening through normal open subvertical folds, and reverse faults developed in shallower crustal level, with vergence towards the Amazonian Craton. The third phase was less pervasive, and the shortening was accommodated by relief subvertical sinistral faults.

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43

Tenzer, Robert, e Ali Fadil. "Tectonic classification of vertical crustal motions – a case study for New Zealand". Contributions to Geophysics and Geodesy 46, n. 2 (1 giugno 2016): 91–109. http://dx.doi.org/10.1515/congeo-2016-0007.

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Abstract We investigate the relationship between vertical crustal motion and tectonic block configuration. The study is conducted along the active tectonic margin between the Australian and Pacific tectonic plates in New Zealand with a well-defined tectonic block configuration. For this purpose, the rates of vertical crustal motions relative to the ITRF2008 reference frame are estimated based on processing the GPS data (provided by the GeoNET project) collected at 123 continuous and semi-continuous GPS sites. The numerical results confirmed the uplift of the central Southern Alps at the current rate of 4.5 mm/yr. This tectonic uplift is coupled in the South Island by the subsidence on both sides of the Southern Alps. The detected rates of subsidence in the eastern South Island are typically less than 1 mm/yr. The subsidence in the Buller Region (in the northwest South Island) is 1.4–1.5 mm/yr. Except for the Taupo Volcanic Zone and the upper Raukumara Block (in the central and northeast North Island), the subsidence is prevailing in the North Island. The systematic subsidence up to 9 mm/yr is detected along the Dextral Fault Belt (in the lower North Island). The largest localized vertical displacements (between −10 and 17 mm/yr) in the Taupo Volcanic Zone are attributed to active tectonics, volcanisms and geothermal processes in this region. A classification of these vertical tectonic motions with respect to the tectonic block configuration reveals that most of tectonic blocks are systematically uplifted, subsided or tilted, except for regions characterized by a complex pattern of vertical motions attributed to active geothermal and volcanic processes.

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Vita-Finzi, C. "River history and tectonics". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370, n. 1966 (13 maggio 2012): 2173–92. http://dx.doi.org/10.1098/rsta.2011.0605.

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Abstract (sommario):

The analysis of crustal deformation by tectonic processes has gained much from the clues offered by drainage geometry and river behaviour, while the interpretation of channel patterns and sequences benefits from information on Earth movements before or during their development. The interplay between the two strands operates at many scales: themes which have already benefited from it include the possible role of mantle plumes in the breakup of Gondwana, the Cenozoic development of drainage systems in Africa and Australia, Himalayan uplift in response to erosion, alternating episodes of uplift and subsidence in the Mississippi delta, buckling of the Indian lithospheric plate, and changes in stream pattern and sinuosity along individual alluvial channels subject to localized deformation. Developments in remote sensing, isotopic dating and numerical modelling are starting to yield quantitative analyses of such effects, to the benefit of geodymamics as well as fluvial hydrology.

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Ivolga, E. G., e Yu F. Manilov. "THE STRUCTURE OF THE WESTERN PRIOKHOTYE LITHOSPHERE (BASED ON THE INTERPRETATION OF GRAVITY DATA)". Tikhookeanskaya Geologiya 42, n. 3 (2023): 20–37. http://dx.doi.org/10.30911/0207-4028-2023-42-3-20-37.

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A density 3D model was constructed, which made it possible to identify inhomogeneities in the western Priokhotye lithosphere and to obtain geophysical characteristics of the main tectonic elements in the region. Qualitative analysis of the density profiles revealed features of fault tectonics at different depth levels. Oblique faults are shown to prevail in the crust of the region, while orthogonal faults prevail in the lithospheric mantle. It is established that the metamorphic basement of the northeastern margin of the North Asian Craton is divided by active long-lived zones into differently directed blocks. Different-level (mantle-crustal) igneous intrusions and endogenous mineralization are confined to the distinguished zones.

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DATTATRAYAM, R. S. "Earthquake source parameter estimation using synthetic waveform modelling". MAUSAM 43, n. 4 (31 dicembre 2021): 365–70. http://dx.doi.org/10.54302/mausam.v43i4.3503.

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Fault plane solutions and focal depths for three crustal events occurring in the Himalayan collision zone have been obtained using synthetic waveform modelling. Two crustal events with their epicenters in the Tibetan plateau show large component of normal faulting with east-west trading T-axes. The third event with It’s epicenter north of Main Boundary Thrust (MBT) shows reverse faulting with the nodal planes paralleling the local structural trend. All the three crustal events studied have occurred at shallow focal depths of less than 15 km. The Inferred source parameters of these events are discussed In the light of active tectonics of the region.

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Papoulia, J., e J. Makris. "TECTONIC PROCESSES AND CRUSTAL EVOLUTION ON/OFFSHORE WESTERN PELOPONNESE DERIVED FROM ACTIVE AND PASSIVE SEISMICS". Bulletin of the Geological Society of Greece 43, n. 1 (19 gennaio 2017): 357. http://dx.doi.org/10.12681/bgsg.11187.

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Abstract (sommario):

We developed velocity models of the crust and sediments offshore south western Greece, between the island of Zakynthos and Messinia. Using these velocity models and depth migrating the seismic data we delineated the main faults and associated them with the tectonic processes of western Greece. This active seismic experiment was essential for defining the limits between the continental domain of western Greece and the oceanic one of the deep Ionian Sea. We successfully linked the onshore with the offshore tectonics and for the first time it was possible to understand how the main dextral fault systems of Cephalonia and Andravida are responsible for the crustal deformation, and its link to the local seismicity. Most of the seismic activity is connected to thrusting, due to crustal shortening or strike-slip faulting that follows the two main dextral wrench faults of Cephalonia and Andravida. It was recognized that the back stop offshore western Peloponnese is floored by thinned continental crust of Preapulia and that the Hellenic Alpine napes do not extend in the back stop domain.

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Lin, Wei, e Qingchen Wang. "Late Mesozoic extensional tectonics in the North China block: a crustal response to subcontinental mantle removal?" Bulletin de la Société Géologique de France 177, n. 6 (1 novembre 2006): 287–97. http://dx.doi.org/10.2113/gssgfbull.177.6.287.

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Abstract In the North China block, Cretaceous extensional tectonics is expressed by numerous syntectonic plutons bounded by ductile normal faults and several metamorphic core complexes (MCC). Cretaceous half-grabens filled by continental terrigenous deposits are widespread. The examples of MCC from South Liaoning Peninsula, Yiwulüshan, Hohhot as well as the Yunmengshan syntectonic pluton spread along ca 2000 km suggest that the early Cretaceous extensional tectonics in the North China block is globally symmetric. The geodynamics setting of this continental-scale extension remains disputed. It is not satisfactorily explained by back-arc rifting related to the Paleo-Pacific subduction or crustal “unthickening”. Mantle lithosphere removal is, however, considered. Upwelling of asthenosphere may be the origin of heat advection and fluid transfer from mantle to lower crust, thus triggerring the Cretaceous magmatism, crustal softening and diffuse continental stretching. Several possible lithosphere-scale models, such as convective removal of mantle lithosphere and detachment of a large piece of mantle, are discussed.

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Höning, Dennis, Nicola Tosi e Tilman Spohn. "Carbon cycling and interior evolution of water-covered plate tectonics and stagnant-lid planets". Astronomy & Astrophysics 627 (luglio 2019): A48. http://dx.doi.org/10.1051/0004-6361/201935091.

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Abstract (sommario):

Aims. The long-term carbon cycle for planets with a surface entirely covered by oceans works differently from that of the present-day Earth because inefficient erosion leads to a strong dependence of the weathering rate on the rate of volcanism. In this paper, we investigate the long-term carbon cycle for these planets throughout their evolution. Methods. We built box models of the long-term carbon cycle based on CO2 degassing, seafloor-weathering, metamorphic decarbonation, and ingassing and coupled them with thermal evolution models of plate tectonics and stagnant-lid planets. Results. The assumed relationship between the seafloor-weathering rate and the atmospheric CO2 or the surface temperature strongly influences the climate evolution for both tectonic regimes. For a planet with plate tectonics, the atmospheric CO2 partial pressure is characterized by an equilibrium between ingassing and degassing and depends on the temperature gradient in subduction zones affecting the stability of carbonates. For a stagnant lid planet, partial melting and degassing are always accompanied by decarbonation, such that the combined carbon content of the crust and atmosphere increases with time. While the initial mantle temperature on planets with plate tectonics only affects the early evolution, it influences the evolution of the surface temperature of stagnant-lid planets for much longer. Conclusions. For both tectonic regimes, mantle cooling results in a decreasing atmospheric CO2 partial pressure. For a planet with plate tectonics this is caused by an increasing fraction of subduction zones that avoid crustal decarbonation, and for stagnant-lid planets this is caused by an increasing decarbonation depth. This mechanism may partly compensate for the increase of the surface temperature due to increasing solar luminosity with time, and thereby contribute to keeping planets habitable in the long-term.

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Ferreira, Ana M. G., Augustin Marignier, Januka Attanayake, Michael Frietsch e Andrea Berbellini. "Crustal structure of the Azores Archipelago from Rayleigh wave ellipticity data". Geophysical Journal International 221, n. 2 (14 febbraio 2020): 1232–47. http://dx.doi.org/10.1093/gji/ggaa076.

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Abstract (sommario):

SUMMARY Determining the crustal structure of ocean island volcanoes is important to understand the formation and tectonic evolution of the oceanic lithosphere and tectonic swells in marine settings, and to assess seismic hazard in the islands. The Azores Archipelago is located near a triple junction system and is possibly under the influence of a mantle plume, being at the locus of a wide range of geodynamic processes. However, its crustal structure is still poorly constrained and debated due to the limited seismic coverage of the region and the peculiar linear geometry of the islands. To address these limitations, in this study we invert teleseismic Rayleigh wave ellipticity measurements for 1-D shear wave speed (VS) crustal models of the Azores Archipelago. Moreover, we test the reliability of these new models by using them in independent moment tensor inversions of local seismic data and demonstrate that our models improve the waveform fit compared to previous models. We find that data from the westernmost seismic stations used in this study require a shallower Moho depth (∼10 km) than data from stations in the eastern part of the archipelago (∼13–16 km). This apparent increase in the Moho depth with increasing distance from the mid-Atlantic ridge (MAR) is expected. However, the rate at which Moho deepens away from the MAR is greater than that predicted from a half-space cooling model, suggesting that local tectonic perturbations have modified crustal structure. The 1-D VS models obtained beneath the westernmost seismic stations also show higher wave speeds than for the easternmost stations, which correlates well with the ages of the islands except Santa Maria Island. We interpret the relatively low VS profile found beneath Santa Maria Island as resulting from underplating, which agrees with previous geological studies of the island. Compared to a recent receiver function study of the region, the shallow structure (top ∼2 km) in our models shows lower shear wave speed, which may have important implications for future hazard studies of the region. More generally, the new seismic crustal models we present in this study will be useful to better understand the tectonics, seismicity, moment tensors and strong ground motions in the region.

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