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Royden, Leigh, et Claudio Faccenna. « Subduction Orogeny and the Late Cenozoic Evolution of the Mediterranean Arcs ». Annual Review of Earth and Planetary Sciences 46, no 1 (30 mai 2018) : 261–89. http://dx.doi.org/10.1146/annurev-earth-060115-012419.
Texte intégralRésumé :
The Late Cenozoic tectonic evolution of the Mediterranean region, which is sandwiched between the converging African and European continents, is dominated by the process of subduction orogeny. Subduction orogeny occurs where localized subduction, driven by negative slab buoyancy, is more rapid than the convergence rate of the bounding plates; it is commonly developed in zones of early or incomplete continental collision. Subduction orogens can be distinguished from collisional orogens on the basis of driving mechanism, tectonic setting, and geologic expression. Three distinct Late Cenozoic subduction orogens can be identified in the Mediterranean region, making up the Western Mediterranean (Apennine, external Betic, Maghebride, Rif), Central Mediterranean (Carpathian), and Eastern Mediterranean (southern Dinaride, external Hellenide, external Tauride) Arcs. The Late Cenozoic evolution of these orogens, described in this article, is best understood in light of the processes that govern subduction orogeny and depends strongly on the buoyancy of the locally subducting lithosphere; it is thus strongly related to paleogeography. Because the slow (4–10 mm/yr) convergence rate between Africa and Eurasia has preserved the early collisional environment, and associated tectonism, for tens of millions of years, the Mediterranean region provides an excellent opportunity to elucidate the dynamic and kinematic processes of subduction orogeny and to better understand how these processes operate in other orogenic systems.
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Müller, R. D., et T. C. W. Landgrebe. « The link between great earthquakes and the subduction of oceanic fracture zones ». Solid Earth 3, no 2 (5 décembre 2012) : 447–65. http://dx.doi.org/10.5194/se-3-447-2012.
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Abstract. Giant subduction earthquakes are known to occur in areas not previously identified as prone to high seismic risk. This highlights the need to better identify subduction zone segments potentially dominated by relatively long (up to 1000 yr and more) recurrence times of giant earthquakes. We construct a model for the geometry of subduction coupling zones and combine it with global geophysical data sets to demonstrate that the occurrence of great (magnitude ≥ 8) subduction earthquakes is strongly biased towards regions associated with intersections of oceanic fracture zones and subduction zones. We use a computational recommendation technology, a type of information filtering system technique widely used in searching, sorting, classifying, and filtering very large, statistically skewed data sets on the Internet, to demonstrate a robust association and rule out a random effect. Fracture zone–subduction zone intersection regions, representing only 25% of the global subduction coupling zone, are linked with 13 of the 15 largest (magnitude Mw ≥ 8.6) and half of the 50 largest (magnitude Mw ≥ 8.4) earthquakes. In contrast, subducting volcanic ridges and chains are only biased towards smaller earthquakes (magnitude < 8). The associations captured by our statistical analysis can be conceptually related to physical differences between subducting fracture zones and volcanic chains/ridges. Fracture zones are characterised by laterally continuous, uplifted ridges that represent normal ocean crust with a high degree of structural integrity, causing strong, persistent coupling in the subduction interface. Smaller volcanic ridges and chains have a relatively fragile heterogeneous internal structure and are separated from the underlying ocean crust by a detachment interface, resulting in weak coupling and relatively small earthquakes, providing a conceptual basis for the observed dichotomy.
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Moore, Nicole E., et Lynn Robinson. « The Role of Subduction Zone Processes in the Cultural History of the Cascade Region ». Elements 18, no 4 (1 août 2022) : 246–50. http://dx.doi.org/10.2138/gselements.18.4.246.
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The Cascadia subduction zone continuously shapes the landscape of the Pacific Northwest of North America and the cultures of its inhabitants. The impacts of subduction processes on Pacific Northwest societies and cultures are varied, but Native Americans and European settler cultures alike have described geological processes through oral histories and have relied on resources provided by the subduction zone. Indigenous peoples focus many aspects of their religious practices and art around the geohazards of the Cascadia region, and our melded modern cultures continue to take part in storytelling related to subduction zone hazards through movies and other forms of narration.
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Walker, James A., et Esteban Gazel. « Igneous Rock Associations 13. Focusing on the Central American Subduction Zone ». Geoscience Canada 41, no 1 (4 mars 2014) : 57. http://dx.doi.org/10.12789/geocanj.2014.41.036.
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Central America has recently been an important focus area for investigations into the complex processes occurring in subduction zones. Here we review some of the new findings concerning subduction input, magma production and evolution, and resultant volcanic output. In the Nicaraguan portion of the subduction zone, subduction input is unusually wet, likely caused by extensive serpentinization of the mantle portion of the incoming plate associated with bending-related faulting seaward of the Middle America trench. The atypical influx of water into the Nicaraguan section of the subduction zone ultimately leads to a regional maximum in the degree of mantle melting. In central Costa Rica, subduction input is also unusual in that it includes oceanic crust flavored by the Galapagos plume. Both of these exotic subduction inputs are recognizable in the compositions of magmas erupted along the volcanic front. In addition, Nicaraguan magmas bear a strong chemical imprint from subducting hemipelagic sediments. The high-field-strength-element depletions of magmas from El Salvador through Costa Rica are related to local variations in the depth to the subducting Cocos plate, and, therefore, to segmentation of the volcanic front. Minor phases, probably amphibole or rutile, control these variable depletions. Silicic magmas erupted along the volcanic front exhibit the same along-arc geochemical variations as their mafic brethren. This and their mantle-like radiogenic isotopic compositions suggest the production of juvenile continental crust all along the Central American subduction zone. Punctuated times of enhanced magmatic input from the mantle may aid in crustal development.SOMMAIREL’Amérique centrale a récemment été le lieu de recherches sur les processus complexes se produisant dans les zones de subduction. Ici nous passons en revue certaines découvertes sur nature des intrants de subduction, la production et l’évolution des magmas, ainsi que les extrants volcaniques résultants. Dans le segment nicaraguayen de la zone de subduction, les intrants de subduction sont exceptionnellement humides, probablement à cause de la serpentinisation généralisée de la portion mantélique de la plaque en subduction, fissurée par flexure dans partie marine de la fosse océanique de l’Amérique centrale. L'afflux atypique en eau dans le segment nicaraguayen de la zone de subduction induit ultimement un maximum régional de la proportion de fusion du manteau. Dans la portion centrale du Costa Rica l’intrant de subduction est lui aussi atypique en ce qu’il comprend une croûte océanique teintée par le panache des Galápagos. Ces deux intrants de subduction atypiques sont répercutés dans la composition des magmas éjectés le long du front volcanique. En outre, les magmas nicaraguayens affichent une forte empreinte chimique héritée des sédiments hémipélagiques en subduction. Les appauvrissements en éléments à fortes liaisons atomiques des magmas, du El Salvador jusqu’au Costa Rica, sont liés à des variations localisées de la profondeur de la plaque en subduction de Cocos, et donc, à la segmentation du front volcanique. Des phases mineures, probablement amphibole et rutile, déterminent ces appauvrissements variables. Les magmas siliceux éjectés le long du même front volcanique montrent les mêmes variations géochimiques le long de l’arc que leur contrepartie mafique. De plus, les compositions radiogéniques de leurs contreparties mantéliques évoquent la production d’une croûte continentale juvénile le long de la zone de subduction de l’Amérique centrale. Des épisodes d’accroissements ponctuels des intrants magmatiques du manteau peuvent contribuer au développement d’une croûte.
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Gerya, Taras. « Numerical modeling of subduction : State of the art and future directions ». Geosphere 18, no 2 (9 février 2022) : 503–61. http://dx.doi.org/10.1130/ges02416.1.
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Abstract During the past five decades, numerical modeling of subduction, one of the most challenging and captivating geodynamic processes, remained in the core of geodynamic research. Remarkable progress has been made in terms of both in-depth understanding of different aspects of subduction dynamics and deciphering the diverse and ever-growing array of subduction zone observations. However, numerous key questions concerning subduction remain unanswered defining the frontier of modern Earth Science research. This review of the past decade comprises numerical modeling studies focused on 12 key open topics: Subduction initiationSubduction terminationSlab deformation, dynamics, and evolution in the mantle4D dynamics of subduction zonesThermal regimes and pressure-temperature (P-T) paths of subducted rocksFluid and melt processes in subduction zonesGeochemical transport, magmatism, and crustal growthTopography and landscape evolutionSubduction-induced seismicityPrecambrian subduction and plate tectonicsExtra-terrestrial subductionInfluence of plate tectonics for life evolution. Future progress will require conceptual and technical progress in subduction modeling as well as crucial inputs from other disciplines (rheology, phase petrology, seismic tomography, geochemistry, numerical theory, geomorphology, ecology, planetology, astronomy, etc.). As in the past, the multi-physics character of subduction-related processes ensures that numerical modeling will remain one of the key quantitative tools for integration of natural observations, developing and testing new hypotheses, and developing an in-depth understanding of subduction. The review concludes with summarizing key results and outlining 12 future directions in subduction and plate tectonics modeling that will target unresolved issues discussed in the review.
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Groves, David I., Liang Zhang et M. Santosh. « Subduction, mantle metasomatism, and gold : A dynamic and genetic conjunction ». GSA Bulletin 132, no 7-8 (4 novembre 2019) : 1419–26. http://dx.doi.org/10.1130/b35379.1.
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Abstract Global gold deposit classes are enigmatic in relation to first-order tectonic scale, leading to controversial genetic models and exploration strategies. Traditionally, hydrothermal gold deposits that formed through transport and deposition from auriferous ore fluids are grouped into specific deposit types such as porphyry, skarn, high- and low-sulfidation–type epithermal, gold-rich volcanogenic massive sulfide (VMS), Carlin-type, orogenic, and iron-oxide copper-gold (IOCG), and intrusion-related gold deposits (IRGDs). District-scale mineral system approaches propose interrelated groups such as porphyry Cu-Au, skarn Cu-Au-Ag, and high-sulfidation Au-Ag. In this study, the temporal evolution of subduction-related processes in convergent margins was evaluated to propose a continuum of genetic models that unify the various types of gold deposits. At the tectonic scale of mineral systems, all hydrothermal gold deposits are interrelated in that they formed progressively during the evolution of direct or indirect subduction-related processes along convergent margins. Porphyry-related systems formed initially from magmatic-hydrothermal fluids related to melting of fertile mantle to initiate calc-alkaline to high-K felsic magmatism in volcanic arcs directly related to subduction. Formation of gold-rich VMS systems was related to hydrothermal circulation driven by magmatic activity during rifting of oceanic arcs. Orogenic gold deposits formed largely through fluids derived from devolatilization of the downgoing slab and overlying sediment wedge during late transpression in the orogenic cycle. Carlin-type deposits, IRGDs, and some continental-arc porphyry systems formed during the early stages of orogenic collapse via fluids directly or indirectly related to hybrid magmatism from melting of lithosphere that was metasomatized and gold-fertilized by earlier fluid release from subduction zones near margins of continental blocks. The IOCGs were formed during postorogenic asthenosphere upwelling beneath such subduction-related metasomatized and fertilized lithospheric blocks via fluid release and explosive emplacement of volatile-rich melts. Thus, importantly, subduction is clearly recognized as the key unifying dynamic factor in gold metallogenesis, with subduction-related fluids or melts providing the critical ore components for a wide variety of gold-rich deposit types.
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Harangi, Szabolcs, Hilary Downes et Ioan Seghedi. « Tertiary-Quaternary subduction processes and related magmatism in the Alpine-Mediterranean region ». Geological Society, London, Memoirs 32, no 1 (2006) : 167–90. http://dx.doi.org/10.1144/gsl.mem.2006.032.01.10.
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Lobkovsky, L. I., M. M. Ramazanov et V. D. Kotelkin. « UPPER MANTLE CONVECTION RELATED TO SUBDUCTION ZONE AND APPLICATION OF THE MODEL TO INVESTIGATE THE CRETACEOUS-CENOZOIC GEODYNAMICS OF CENTRAL EAST ASIA AND THE ARCTIC ». Geodynamics & ; Tectonophysics 12, no 3 (17 septembre 2021) : 455–70. http://dx.doi.org/10.5800/gt-2021-12-3-0533.
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A geodynamic model of upper mantle convection related to the Pacific subduction zone is mathematically substantiated and applied to investigate the Cretaceous-Cenozoic evolution of Central East Asia (CEA) and the Arctic. We present a solution for the two-dimensional stationary problem of thermal convection in the upper mantle layer, considering different Rayleigh numbers and taking into account the influence of the subduction process and lithospheric movements along the upper mantle base. We describe the results of 3D modeling of nonstationary upper mantle convection in a subduction zone. Our data give grounds to propose explanations for the entire spectrum of tectonic-magmatic processes developing within CEA in the Cenozoic and the Arctic in the Upper Cretaceous and Cenozoic. We discuss the reasons why the lithosphere in CEA and the Arctic is generally shifting towards the Pacific subduction zone, considering the presence of separate magmatic provinces and rift zones. In our opinion, this is due to the existence of a large horizontally elongated convective cell, which interior is composed of smaller isometric cells. This long cell creates the effect of conveyor dragging of the lithosphere, while its internal cells produce the effect of upper mantle plumes.
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Myeong, Bora, Jonguk Kim, Jung Hoon Kim et Yun Deuk Jang. « Petrogenesis of subduction-related lavas from the southern Tonga arc ». Journal of Asian Earth Sciences 188 (février 2020) : 104089. http://dx.doi.org/10.1016/j.jseaes.2019.104089.
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Arcay, D. « Dynamics of interplate domain in subduction zones : influence of rheological parameters and subducting plate age ». Solid Earth 3, no 2 (21 décembre 2012) : 467–88. http://dx.doi.org/10.5194/se-3-467-2012.
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Abstract. The properties of the subduction interplate domain are likely to affect not only the seismogenic potential of the subduction area but also the overall subduction process, as it influences its viability. Numerical simulations are performed to model the long-term equilibrium state of the subduction interplate when the diving lithosphere interacts with both the overriding plate and the surrounding convective mantle. The thermomechanical model combines a non-Newtonian viscous rheology and a pseudo-brittle rheology. Rock strength here depends on depth, temperature and stress, for both oceanic crust and mantle rocks. I study the evolution through time of, on one hand, the brittle-ductile transition (BDT) depth, zBDT, and, on the other hand, of the kinematic decoupling depth, zdec, simulated along the subduction interplate. The results show that both a high friction and a low ductile strength at the asthenospheric wedge tip shallow zBDT. The influence of the weak material activation energy is of second order but not negligible. zBDT becomes dependent on the ductile strength increase with depth (activation volume) if the BDT occurs at the interplate decoupling depth. Regarding the interplate decoupling depth, it is shallowed (1) significantly if mantle viscosity at asthenospheric wedge tip is low, (2) if the difference in mantle and interplate activation energy is weak, and (3) if the activation volume is increased. Very low friction coefficients and/or low asthenospheric viscosities promote zBDT = zdec. I then present how the subducting lithosphere age affects the brittle-ductile transition depth and the kinematic decoupling depth in this model. Simulations show that a rheological model in which the respective activation energies of mantle and interplate material are too close hinders the mechanical decoupling at the down-dip extent of the interplate, and eventually jams the subduction process during incipient subduction of a young (20-Myr-old) and soft lithosphere under a thick upper plate. Finally, both the BDT depth and the decoupling depth are a function of the subducting plate age, but are not influenced in the same fashion: cool and old subducting plates deepen the BDT but shallow the interplate decoupling depth. Even if BDT and kinematic decoupling are intrinsically related to different mechanisms of deformation, this work shows that they are able to interact closely. Comparison between modelling results and observations suggests a minimum friction coefficient of 0.045 for the interplate plane, even 0.069 in some cases, to model realistic BDT depths. The modelled zdec is a bit deeper than suggested by geophysical observations. Eventually, the better way to improve the adjustment to observations may rely on a moderate to strong asthenosphere viscosity reduction in the metasomatised mantle wedge.
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Gosselin, Jeremy M., Pascal Audet, Clément Estève, Morgan McLellan, Stephen G. Mosher et Andrew J. Schaeffer. « Seismic evidence for megathrust fault-valve behavior during episodic tremor and slip ». Science Advances 6, no 4 (janvier 2020) : eaay5174. http://dx.doi.org/10.1126/sciadv.aay5174.
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Fault slip behavior during episodic tremor and slow slip (ETS) events, which occur at the deep extension of subduction zone megathrust faults, is believed to be related to cyclic fluid processes that necessitate fluctuations in pore-fluid pressures. In most subduction zones, a layer of anomalously low seismic wave velocities [low-velocity layer (LVL)] is observed in the vicinity of ETS and suggests high pore-fluid pressures that weaken the megathrust. Using repeated seismic scattering observations in the Cascadia subduction zone, we observe a change in the seismic velocity associated with the LVL after ETS events, which we interpret as a response to fluctuations in pore-fluid pressure. These results provide direct evidence of megathrust fault-valve processes during ETS.
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Watson, Sally J., Joshu J. Mountjoy, Philip M. Barnes, Gareth J. Crutchley, Geoffroy Lamarche, Ben Higgs, Jess Hillman et al. « Focused fluid seepage related to variations in accretionary wedge structure, Hikurangi margin, New Zealand ». Geology 48, no 1 (28 octobre 2019) : 56–61. http://dx.doi.org/10.1130/g46666.1.
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Abstract Hydrogeological processes influence the morphology, mechanical behavior, and evolution of subduction margins. Fluid supply, release, migration, and drainage control fluid pressure and collectively govern the stress state, which varies between accretionary and nonaccretionary systems. We compiled over a decade of published and unpublished acoustic data sets and seafloor observations to analyze the distribution of focused fluid expulsion along the Hikurangi margin, New Zealand. The spatial coverage and quality of our data are exceptional for subduction margins globally. We found that focused fluid seepage is widespread and varies south to north with changes in subduction setting, including: wedge morphology, convergence rate, seafloor roughness, and sediment thickness on the incoming Pacific plate. Overall, focused seepage manifests most commonly above the deforming backstop, is common on thrust ridges, and is largely absent from the frontal wedge despite ubiquitous hydrate occurrences. Focused seepage distribution may reflect spatial differences in shallow permeability architecture, while diffusive fluid flow and seepage at scales below detection limits are also likely. From the spatial coincidence of fluids with major thrust faults that disrupt gas hydrate stability, we surmise that focused seepage distribution may also reflect deeper drainage of the forearc, with implications for pore-pressure regime, fault mechanics, and critical wedge stability and morphology. Because a range of subduction styles is represented by 800 km of along-strike variability, our results may have implications for understanding subduction fluid flow and seepage globally.
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Fyfe, W. S. « Granites and a wet convecting ultramafic planenet ». Earth and Environmental Science Transactions of the Royal Society of Edinburgh 79, no 2-3 (1988) : 339–46. http://dx.doi.org/10.1017/s0263593300014310.
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ABSTRACTGranites and their associated extrusive rocks are formed in large volumes whenever the continental crust is heated by rising hot mantle, or thickened by collision processes. The complexity of rocks of the granite family is related to the complexity of the continental crust itself and the complexity of processes which lead to thermal perturbations. The light continental crust acts as a density filter which screens out heavy mantle magmas and leads to complex underplating and magma mixing processes. Perhaps the primary cause of crustal melting is the deep recycling of volatiles which are fixed in the oceanic crust before subduction. Modern studies of subduction and collision processes show the large scale and complexity of processes which modify old continental crust.
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Proietti, Giampaolo, Alessia Conti, Marco Cuffaro, Paolo Esestime et Sabina Bigi. « Subduction related faults and sedimentary basins : The Western Ionian Sea case ». Tectonophysics 813 (août 2021) : 228943. http://dx.doi.org/10.1016/j.tecto.2021.228943.
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Tursi, Fabrizio, Richard Spiess, Vincenzo Festa et Rosa Anna Fregola. « Hercynian subduction‐related processes within the metamorphic continental crust in Calabria (southern Italy) ». Journal of Metamorphic Geology 38, no 7 (3 juillet 2020) : 771–93. http://dx.doi.org/10.1111/jmg.12537.
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Bohm, Mirjam, Christian Haberland et Günter Asch. « Imaging fluid-related subduction processes beneath Central Java (Indonesia) using seismic attenuation tomography ». Tectonophysics 590 (avril 2013) : 175–88. http://dx.doi.org/10.1016/j.tecto.2013.01.021.
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Westby, Elizabeth G., Andrew Meigs et Chris Goldfinger. « Volcano, Earthquake, and Tsunami Hazards of the Cascadia Subduction Zone ». Elements 18, no 4 (1 août 2022) : 251–56. http://dx.doi.org/10.2138/gselements.18.4.251.
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Subduction zones produce some of Earth’s most devastating geological events. Recent eruptions of Mount St. Helens and great earthquakes and tsunamis in Japan and Sumatra provide stark examples of the destructive power of subduction-related hazards. In the Cascadia subduction zone, large earthquakes, tsunamis, and volcanic eruptions have occurred in the past and geologic records imply that these events will occur in the future. As the population and infrastructure increase in the region, resilience to these natural hazards requires a detailed scientific understanding of the geologic forces and processes involved, combined with a society motivated to mitigate risks.
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Leat, Philip T., et Teal R. Riley. « Chapter 3.1b Antarctic Peninsula and South Shetland Islands : petrology ». Geological Society, London, Memoirs 55, no 1 (2021) : 213–26. http://dx.doi.org/10.1144/m55-2018-68.
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AbstractThe Antarctic Peninsula contains a record of continental-margin volcanism extending from Jurassic to Recent times. Subduction of the Pacific oceanic lithosphere beneath the continental margin developed after Late Jurassic volcanism in Alexander Island that was related to extension of the continental margin. Mesozoic ocean-floor basalts emplaced within the Alexander Island accretionary complex have compositions derived from Pacific mantle. The Antarctic Peninsula volcanic arc was active from about Early Cretaceous times until the Early Miocene. It was affected by hydrothermal alteration, and by regional and contact metamorphism generally of zeolite to prehnite–pumpellyite facies. Distinct geochemical groups recognized within the volcanic rocks suggest varied magma generation processes related to changes in subduction dynamics. The four groups are: calc-alkaline, high-Mg andesitic, adakitic and high-Zr, the last two being described in this arc for the first time. The dominant calc-alkaline group ranges from primitive mafic magmas to rhyolite, and from low- to high-K in composition, and was generated from a mantle wedge with variable depletion. The high-Mg and adakitic rocks indicate periods of melting of the subducting slab and variable equilibration of the melts with mantle. The high-Zr group is interpreted as peralkaline and may have been related to extension of the arc.
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Cisneros, Miguel, Jaime D. Barnes, Whitney M. Behr, Alissa J. Kotowski, Daniel F. Stockli et Konstantinos Soukis. « Insights from elastic thermobarometry into exhumation of high-pressure metamorphic rocks from Syros, Greece ». Solid Earth 12, no 6 (15 juin 2021) : 1335–55. http://dx.doi.org/10.5194/se-12-1335-2021.
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Abstract. Retrograde metamorphic rocks provide key insights into the pressure–temperature (P–T) evolution of exhumed material, and resultant P–T constraints have direct implications for the mechanical and thermal conditions of subduction interfaces. However, constraining P–T conditions of retrograde metamorphic rocks has historically been challenging and has resulted in debate about the conditions experienced by these rocks. In this work, we combine elastic thermobarometry with oxygen isotope thermometry to quantify the P–T evolution of retrograde metamorphic rocks of the Cycladic Blueschist Unit (CBU), an exhumed subduction complex exposed on Syros, Greece. We employ quartz-in-garnet and quartz-in-epidote barometry to constrain pressures of garnet and epidote growth near peak subduction conditions and during exhumation, respectively. Oxygen isotope thermometry of quartz and calcite within boudin necks was used to estimate temperatures during exhumation and to refine pressure estimates. Three distinct pressure groups are related to different metamorphic events and fabrics: high-pressure garnet growth at ∼1.4–1.7 GPa between 500–550 ∘C, retrograde epidote growth at ∼1.3–1.5 GPa between 400–500 ∘C, and a second stage of retrograde epidote growth at ∼1.0 GPa and 400 ∘C. These results are consistent with different stages of deformation inferred from field and microstructural observations, recording prograde subduction to blueschist–eclogite facies and subsequent retrogression under blueschist–greenschist facies conditions. Our new results indicate that the CBU experienced cooling during decompression after reaching maximum high-pressure–low-temperature conditions. These P–T conditions and structural observations are consistent with exhumation and cooling within the subduction channel in proximity to the refrigerating subducting plate, prior to Miocene core-complex formation. This study also illustrates the potential of using elastic thermobarometry in combination with structural and microstructural constraints, to better understand the P–T-deformation conditions of retrograde mineral growth in high-pressure–low-temperature (HP/LT) metamorphic terranes.
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Lallemant, Siegfried, Nicolas Chamot-Rooke, Xavier Le Pichon et Claude Rangin. « Zenisu Ridge : a deep intraoceanic thrust related to subduction, off southwest Japan ». Tectonophysics 160, no 1-4 (mars 1989) : 151–74. http://dx.doi.org/10.1016/0040-1951(89)90389-2.
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Loreto, Maria Filomena, Camilla Palmiotto, Filippo Muccini, Valentina Ferrante et Nevio Zitellini. « Inverted Basins by Africa–Eurasia Convergence at the Southern Back-Arc Tyrrhenian Basin ». Geosciences 11, no 3 (4 mars 2021) : 117. http://dx.doi.org/10.3390/geosciences11030117.
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The southern part of Tyrrhenian back-arc basin (NW Sicily), formed due to the rifting and spreading processes in back-arc setting, is currently undergoing contractional tectonics. The analysis of seismic reflection profiles integrated with bathymetry, magnetic data and seismicity allowed us to map a widespread contractional tectonics structures, such as positive flower structures, anticlines and inverted normal faults, which deform the sedimentary sequence of the intra-slope basins. Two main tectonic phases have been recognised: (i) a Pliocene extensional phase, active during the opening of the Vavilov Basin, which was responsible for the formation of elongated basins bounded by faulted continental blocks and controlled by the tear of subducting lithosphere; (ii) a contractional phase related to the Africa-Eurasia convergence coeval with the opening of the Marsili Basin during the Quaternary time. The lithospheric tear occurred along the Drepano paleo-STEP (Subduction-Transform-Edge-Propagator) fault, where the upwelling of mantle, intruding the continental crust, formed a ridge. Since Pliocene, most of the contractional deformation has been focused along this ridge, becoming a good candidate for a future subduction initiation zone.
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Ellam, R. M., C. J. Hawkesworth, D. S. Ormerod et N. W. Rogers. « Rb/Sr and U/Pb fractionation in subduction-related processes : Implications for mantle evolution ». Chemical Geology 70, no 1-2 (août 1988) : 49. http://dx.doi.org/10.1016/0009-2541(88)90316-6.
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Manthilake, Geeth, Nathalie Bolfan-Casanova, Davide Novella, Mainak Mookherjee et Denis Andrault. « Dehydration of chlorite explains anomalously high electrical conductivity in the mantle wedges ». Science Advances 2, no 5 (mai 2016) : e1501631. http://dx.doi.org/10.1126/sciadv.1501631.
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Mantle wedge regions in subduction zone settings show anomalously high electrical conductivity (~1 S/m) that has often been attributed to the presence of aqueous fluids released by slab dehydration. Laboratory-based measurements of the electrical conductivity of hydrous phases and aqueous fluids are significantly lower and cannot readily explain the geophysically observed anomalously high electrical conductivity. The released aqueous fluid also rehydrates the mantle wedge and stabilizes a suite of hydrous phases, including serpentine and chlorite. In this present study, we have measured the electrical conductivity of a natural chlorite at pressures and temperatures relevant for the subduction zone setting. In our experiment, we observe two distinct conductivity enhancements when chlorite is heated to temperatures beyond its thermodynamic stability field. The initial increase in electrical conductivity to ~3 × 10−3S/m can be attributed to chlorite dehydration and the release of aqueous fluids. This is followed by a unique, subsequent enhancement of electrical conductivity of up to 7 × 10−1S/m. This is related to the growth of an interconnected network of a highly conductive and chemically impure magnetite mineral phase. Thus, the dehydration of chlorite and associated processes are likely to be crucial in explaining the anomalously high electrical conductivity observed in mantle wedges. Chlorite dehydration in the mantle wedge provides an additional source of aqueous fluid above the slab and could also be responsible for the fixed depth (120 ± 40 km) of melting at the top of the subducting slab beneath the subduction-related volcanic arc front.
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Baldwin, Suzanne L., Jan Schönig, Joseph P. Gonzalez, Hugh Davies et Hilmar von Eynatten. « Garnet sand reveals rock recycling processes in the youngest exhumed high- and ultrahigh-pressure terrane on Earth ». Proceedings of the National Academy of Sciences 118, no 3 (11 janvier 2021) : e2017231118. http://dx.doi.org/10.1073/pnas.2017231118.
Texte intégralRésumé :
Rock recycling within the forearcs of subduction zones involves subduction of sediments and hydrated lithosphere into the upper mantle, exhumation of rocks to the surface, and erosion to form new sediment. The compositions of, and inclusions within detrital minerals revealed by electron microprobe analysis and Raman spectroscopy preserve petrogenetic clues that can be related to transit through the rock cycle. We report the discovery of the ultrahigh-pressure (UHP) indicator mineral coesite as inclusions in detrital garnet from a modern placer deposit in the actively exhuming Late Miocene–Recent high- and ultrahigh-pressure ((U)HP) metamorphic terrane of eastern Papua New Guinea. Garnet compositions indicate the coesite-bearing detrital garnets are sourced from felsic protoliths. Carbonate, graphite, and CO2 inclusions also provide observational constraints for geochemical cycling of carbon and volatiles during subduction. Additional discoveries include polyphase inclusions of metastable polymorphs of SiO2 (cristobalite) and K-feldspar (kokchetavite) that we interpret as rapidly cooled former melt inclusions. Application of elastic thermobarometry on coexisting quartz and zircon inclusions in six detrital garnets indicates elastic equilibration during exhumation at granulite and amphibolite facies conditions. The garnet placer deposit preserves a record of the complete rock cycle, operative on <10-My geologic timescales, including subduction of sedimentary protoliths to UHP conditions, rapid exhumation, surface uplift, and erosion. Detrital garnet geochemistry and inclusion suites from both modern sediments and stratigraphic sections can be used to decipher the petrologic evolution of plate boundary zones and reveal recycling processes throughout Earth’s history.
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Jaxybulatov, K., I. Koulakov et N. L. Dobretsov. « Segmentation of the Izu-Bonin and Mariana slabs based on the analysis of the Benioff seismicity distribution and regional tomography results ». Solid Earth 4, no 1 (31 janvier 2013) : 59–73. http://dx.doi.org/10.5194/se-4-59-2013.
Texte intégralRésumé :
Abstract. We present a new model of P and S velocity anomalies in the mantle down to a depth of 1300 km beneath the Izu-Bonin and Mariana (IBM) arcs. This model is derived based on tomographic inversion of global travel time data from the revised ISC catalogue. The results of inversion are thoroughly verified using a series of different tests. The obtained model is generally consistent with previous studies by different authors. We also present the distribution of relocated deep events projected to the vertical surface along the IBM arc system. Unexpectedly, the seismicity forms elongated vertical clusters instead of horizontal zones indicating phase transitions in the slab. We propose that these vertical seismicity zones mark zones of intense deformation and boundaries between semi-autonomous segments of the subducting plate. The P and S seismic tomography models consistently display the slab as prominent high-velocity anomalies coinciding with the distribution of deep seismicity. We can distinguish at least four segments which subduct differently. The northernmost segment of the Izu-Bonin arc has the gentlest angle of dipping which is explained by backward displacement of the trench. In the second segment, the trench stayed at the same location, and we observe the accumulation of the slab material in the transition zone and its further descending to the lower mantle. In the third segment, the trench is moving forward causing the steepening of the slab. Finally, for the Mariana segment, despite the backward displacement of the arc, the subducting slab is nearly vertical. Between the Izu-Bonin and Mariana arcs we clearly observe a gap which can be traced down to about 400 km in depth. Based on joint consideration of the tomography results and the seismicity distribution, we propose two different scenarios of the subduction evolution in the IBM zone during the recent time, depending on the reference frame of plate displacements. In the first case, we consider the movements in respect to the Philippine Plate, and explain the different styles of the subduction by the relative backward and forward migrations of the trench. In the second case, all the elements of the subduction system move westward in respect to the stable Asia. Different subduction styles are explained by the "anchoring" of selected segments of the slab, different physical properties of the subducting plate and the existence of buoyant rigid blocks related to sea mount and igneous provinces.
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Fryer, Patricia, C. Geoffrey Wheat, Trevor Williams, Christopher Kelley, Kevin Johnson, Jeffrey Ryan, Walter Kurz et al. « Mariana serpentinite mud volcanism exhumes subducted seamount materials : implications for the origin of life ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 378, no 2165 (6 janvier 2020) : 20180425. http://dx.doi.org/10.1098/rsta.2018.0425.
Texte intégralRésumé :
The subduction of seamounts and ridge features at convergent plate boundaries plays an important role in the deformation of the overriding plate and influences geochemical cycling and associated biological processes. Active serpentinization of forearc mantle and serpentinite mud volcanism on the Mariana forearc (between the trench and active volcanic arc) provides windows on subduction processes. Here, we present (1) the first observation of an extensive exposure of an undeformed Cretaceous seamount currently being subducted at the Mariana Trench inner slope; (2) vertical deformation of the forearc region related to subduction of Pacific Plate seamounts and thickened crust; (3) recovered Ocean Drilling Program and International Ocean Discovery Program cores of serpentinite mudflows that confirm exhumation of various Pacific Plate lithologies, including subducted reef limestone; (4) petrologic, geochemical and paleontological data from the cores that show that Pacific Plate seamount exhumation covers greater spatial and temporal extents; (5) the inference that microbial communities associated with serpentinite mud volcanism may also be exhumed from the subducted plate seafloor and/or seamounts; and (6) the implications for effects of these processes with regard to evolution of life. This article is part of a discussion meeting issue ‘Serpentine in the Earth system’.
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Zhu, Weiling, Lin Ding, Yingfeng Ji, Rui Qu, Ye Zhu, Chaodi Xie et Deng Zeng. « Subduction Evolution Controlled Himalayan Orogenesis : Implications from 3-D Subduction Modeling ». Applied Sciences 12, no 15 (23 juillet 2022) : 7413. http://dx.doi.org/10.3390/app12157413.
Texte intégralRésumé :
Himalayan orogenesis remains enigmatic in terms of Tibetan Plateau geodynamics originating from the Cenozoic India–Eurasian continental collision. India underthrusts below Tibet to the Yarlung–Tsangpo suture, which has been identified as the northernmost boundary for underplating. However, the way in which the historical evolution of continental subduction induces plateau uplift and the way it controls the variation in uplift between outboard and inboard areas is still unclear. To interpret the evolutionary mechanisms involved in the Himalayan growth history, we constructed different 3-D dynamic models at important stages to address these questions related to the formation of the Himalayas on the basis of paleoenthalpy evidence encoded in fossil leaves from recently documented assemblages in southern Tibet. The results show that (1) the effect of crustal thickening was the predominant factor in the early evolution from the Paleocene to the early Eocene, which resulted in a moderate growth rate. (2) The consecutive slab break-off eastward from the western syntaxis and the associated slab rebound significantly accelerated orogenesis from the late Eocene to the Oligocene. The upwelling asthenospheric flow was a key control of increasing crustal buoyancy, which resulted in the fastest growth of the Himalayas during the early Miocene. (3) Thereafter, the gradually enhanced monsoon and surface erosion during accompanying the increasing mountain height resulted in a slowdown of the orogenic rate, which counterbalanced the buoyant force produced by asthenospheric flow driving continuous Himalayan growth.
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Schoonover, Mark, et Soichi Osozawa. « Exhumation process of the Nago subduction-related metamorphic rocks, Okinawa, Ryukyu island arc ». Tectonophysics 393, no 1-4 (novembre 2004) : 221–40. http://dx.doi.org/10.1016/j.tecto.2004.07.036.
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Wang, Zhong-Mei, Chun-Ming Han, Wen-Jiao Xiao, Ben-Xun Su et Jia-Xin Ding. « Paleoproterozoic subduction-related magmatism and crustal evolution of the Dunhuang Block, NW China ». Journal of Asian Earth Sciences 134 (février 2017) : 13–28. http://dx.doi.org/10.1016/j.jseaes.2016.11.008.
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Hanuš, V., et J. Vaněk. « Seismically active fracture zones related to the eastern segment of the Hellenic subduction ». Journal of Geodynamics 17, no 1-2 (mai 1993) : 39–56. http://dx.doi.org/10.1016/0264-3707(93)90016-y.
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Li, Dapeng, Yuelong Chen, Guoliang Xue, Huan Kang, Yang Yu, Jianzhen Geng, Yulong Zhang et Ting Li. « Initiation of modern-style subduction in the Neoarchean : From plume to subduction with frequent slab break-off ». GSA Bulletin 132, no 9-10 (9 mars 2020) : 2119–34. http://dx.doi.org/10.1130/b35522.1.
Texte intégralRésumé :
Abstract Fundamental geodynamic changes from vertical tectonics to lateral subduction occurred during the Neoarchean, yet detailed processes related to this transition and initiation of modern-style subduction remain enigmatic. Successive Neoarchean magmatic rocks including both plume-derived komatiites and subduction-related supracrustal and intrusive rocks appeared and preserved key information on the late Archean geodynamic changes in the Western Shandong Province granite-greenstone belt (WSP), North China Craton. In this study, whole-rock geochemical and Sm-Nd isotopic data and zircon U-Pb and Lu-Hf isotopes are reported for early Neoarchean supracrustal and intrusive rocks for the WSP. Temporally, the early Neoarchean magmatic movements in the WSP can be subdivided into two stages, including the early stage (2.77–2.69 Ga) and the late stage (2.69–2.60 Ga). Spatially, from southwest to northeast, intrusive rocks with similar ages define three belts (A, B, and C). Early stage tholeiitic and enriched meta-basalts were plume-related, representing oceanic crust opening from a pre-early Neoarchean continent. Slab subduction at least initiated at ca. 2.74 Ga and generated various Neoarchean tonalite-trondhjemite-granodiorites, quartz diorites, and arc-related volcanic rocks and mafic intrusions. Episodic emergence of meta-basaltic rocks and/or mafic intrusions with depleted εHf(t) values and low (La/Yb)N ratios indicates frequent slab break-offs during ca. 2.70–2.68 Ga, 2.66–2.64 Ga, and 2.62–2.60 Ga due to a relatively hotter mantle and regional heating by mantle plume. Secular geochemical changes of mafic and felsic rocks in this study outline roles of slab subduction in contributions of cooling the mantle, secular mantle refertilization, and crustal growth.
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Leclerc, Frédérique, et Nathalie Feuillet. « Quaternary coral reef complexes as powerful markers of long-term subsidence related to deep processes at subduction zones : Insights from Les Saintes (Guadeloupe, French West Indies) ». Geosphere 15, no 4 (5 juin 2019) : 983–1007. http://dx.doi.org/10.1130/ges02069.1.
Texte intégralRésumé :
Abstract Geodetic measurements reveal modern rates of tectonic deformation along subduction zones, but the kinematics of long-term deformation are typically poorly constrained. We explore the use of submarine coral reefs as a record of long-term coastal vertical motion in order to determine deformation rate and discuss its origins. The Lesser Antilles arc results from the subduction of the American plates beneath the Caribbean plate and undergoes regional vertical deformation. Uplifted reefs along forearc islands are markers of the interplay between tectonics and sea-level variations since the late Pleistocene. We compared results from a numerical model of reef-island profile development to high-resolution marine geophysical measurements of Les Saintes reef plateau (Guadeloupe, French West Indies), a ∼20-km-wide, 250-m-thick submerged platform that lies at 45 m below sea level along the volcanic arc, to constrain its vertical deformation history. Models explore different scenarios over wide parameter domains including start time, basement morphology, sea level variations, reef growth rate, subaerial erosion rate, and vertical motion history. The major features of the plateau (its depth, internal structure, unusual double-barrier) is only reproduced in a context of subsidence, with a constant rate of −0.3 to −0.45 mm/yr since the late Pleistocene, or in a context of increasing subsidence, presently of ∼–0.2 mm/yr. Discussed in the framework of the forearc vertical deformation history, this result indicates subsidence is promoted by local faulting, volcanic, and deep subduction processes. Coseismic deformation accumulation could be a mechanism by which deformation builds up in the long-term. We show that subduction can drive long-term subsidence of a volcanic arc, and demonstrate that submarine reefs are powerful markers of long-term vertical motion.
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Alvarez-Marron, J., E. Rubio et M. Torne. « Subduction-related structures in the North Iberian Margin ». Journal of Geophysical Research : Solid Earth 102, B10 (10 octobre 1997) : 22497–511. http://dx.doi.org/10.1029/97jb01425.
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MUKHERJEE, BARUN K., et HIMANSHU K. SACHAN. « Fluids in coesite-bearing rocks of the Tso Morari Complex, NW Himalaya : evidence for entrapment during peak metamorphism and subsequent uplift ». Geological Magazine 146, no 6 (15 juillet 2009) : 876–89. http://dx.doi.org/10.1017/s0016756809990069.
Texte intégralRésumé :
AbstractFluid inclusions trapped in coesite-bearing rocks provide important information on the fluid phases present during ultrahigh-pressure metamorphism. The subduction-related coesite-bearing eclogites of the Tso Morari Complex, Himalaya, contain five major types of fluids identified by microthermometry and Raman spectroscopy. These are: (1) high-salinity brine, (2) N2, (3) CH4, (4) CO2and (5) low-salinity aqueous fluids. These fluids were trapped during both deep subduction and exhumation processes. The coesite-bearing rocks are inferred to have been buried to a depth of >120 km, where they experienced ultrahigh-pressure metamorphism. The fluid–rock interaction provides direct evidence for fluid derivation during a deep subduction process as demonstrated by silica–carbonate assemblages in eclogite. High salinity brine, N2and CH4inclusions are remnants of prograde and peak metamorphic fluids, whereas CO2and low-salinity aqueous fluids appear to have been trapped late, during uplift. The high-salinity brine was possibly derived from subducted ancient metasedimentary rocks, whereas the N2and CH4fluids were likely generated through chemical breakdown of NH3-bearing K minerals and graphite. Alternatively, CH4might have been formed by a mixed fluid that was released from calcareous sediments during subduction or supplied through subducted oceanic metabasic rocks. High density CO2is associated with matrix minerals formed during granulite-facies overprinting of the ultrahigh-pressure eclogite. During retrogression to amphibolite-facies conditions, low-salinity fluids were introduced from external sources, probably the enclosing gneisses. This source enhances salinity differences as compared to primary saline inclusions. The subducting Indian lithosphere produced brines prior to achieving maximal depths of >120 km, where fluids were instead dominated by gaseous phases. Subsequently, the Indian lithosphere released CO2-rich fluids during fast exhumation and was then infiltrated by the low-salinity aqueous fluids near the surface through external sources. Elemental modelling may improve quantitative understanding of the complexity of fluids and their reactions.
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Figueiredo, M. C. H. « Geochemical evolution of eastern Bahia, Brazil : A probable Early Proterozoic subduction-related magmatic arc ». Journal of South American Earth Sciences 2, no 2 (janvier 1989) : 131–45. http://dx.doi.org/10.1016/0895-9811(89)90041-2.
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Safonova, I. Yu, et А. I. Khanchuk. « SUBDUCTION EROSION AT PACIFIC-TYPE CONVERGENT MARGINS ». Tikhookeanskaya Geologiya 40, no 6 (2021) : 3–19. http://dx.doi.org/10.30911/0207-4028-2021-40-6-3-19.
Texte intégralRésumé :
The paper presents a review of processes of subduction or tectonic erosion at the Pacific-type convergent margins (PTCM) including definition of “tectonic erosion”, its triggers, driving forces and consequences. We review examples of tectonic erosion at the Circum-Pacific PTCMs and at the fossil PTCMs of the Paleo-Asian Ocean (PAO) currently hosted by the Central-Asian Orogenic Belt (CAOB). Recent geological and stratigraphic studies have shown two types of PTCMs: accreting and eroding. Accreting PTCMs consist of older deposits of accretionary and frontal prisms and grow oceanward, i.e. the trench retreats. Eroding PTCMs are characterized by the destruction of the prism, approaching arc and trench and typically form during shallow-angle and fast subduction of an oceanic slab with oceanic floor topographic highs. The mechanism of tectonic erosion includes destruction of oceanic slab, island arcs, accretionary prism, fore-arc and related prism. Tectonic erosion is a common phenomenon at many Circum-Pacific PTCMs, e.g., in South America, Tonga and Nankai troughs, Alaska. Accretion and subduction of oceanic rises contributes greatly to the processes of formation, transformation and destruction of continental crust at PTCM. The episodes of tectonic erosion can be also reconstructed for an ancient ocean, for example, for the PAO, which evolution and suturing formed the CAOB. Many CAOB foldbelts (Altai, Tienshan, eastern Kazakhstan, Transbaikalia, Mongolia) carry signs of disap-pearance of big volumes of continental crust (arcs). Studying processes responsible not only for the formation of continental crust, but also for the disappearance of big volumes of crustal mate-rial is important for correct evaluation of the nature of intra-continental orogenic belts, e.g., CAOB, and development of reliable tectonic models.
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Kosarev, A. M., A. G. Vladimirov, A. I. Khanchuk, D. N. Salikhov, V. B. Kholodnov, T. A. Osipova, G. A. Kallistov, I. B. Seravkin, I. R. Rakhimov et G. T. Shafigullina. « DEVONIAN-CARBONIFEROUS MAGMATISM AND METALLOGENY IN THE SOUTH URAL ACCRETIONARY-COLLISIONAL SYSTEM ». Geodynamics & ; Tectonophysics 12, no 2 (23 juin 2021) : 365–91. http://dx.doi.org/10.5800/gt-2021-12-2-0529.
Texte intégralRésumé :
The oceanic stage in the history of the South Urals completed in the Ordovician – Early Silurian. The Ordovician through Devonian events in the region included the formation of an island arc in the East Ural zone from the Middle Ordovician to Silurian; westward motion of the subduction zone in the Late Silurian – Early Devonian and the origin of a trench along the Main Ural Fault and the Uraltau Uplift; volcanic eruptions and intrusions in the Magnitogorsk island arc system in the Devonian. The Middle-Late Paleozoic geodynamic evolution of uralides and altaides consisted in successive alternation of subduction and collisional settings at the continent-ocean transition. The greatest portion of volcanism in the major Magnitogorsk zone was associated with subduction and correlated in age and patterns of massive sulfide mineralization (VMS) with Early – Middle Devonian ore-forming events in Rudny Altai. Within-plate volcanism at the onset of volcanic cycles records the Early (D1e2) and Middle (D2ef2) Devonian slab break off. The volcanic cycles produced, respectively, the Buribay and Upper Tanalyk complexes with VMS mineralization in the Late Emsian; the Karamalytash complex and its age equivalents in the Late Eifelian – Early Givetian, as well as the lower Ulutau Formation in the Givetian. Slab break off in the Late Devonian – Early Carboniferous obstructed the Magnitogorsk island arc and supported asthenospheric diapirism. A new subduction zone dipping westward and the Aleksandrovka island arc formed in the Late Devonian – Early Carboniferous. The Early Carboniferous collision and another event of obstructed subduction led to a transform margin setting corresponding to postcollisional relative sliding of plates that produced another slab tear. Postcollisional magmatism appears as alkaline gabbro-granitic intrusives with related rich Ti-magnetite mineralization (C1). Transform faulting persisted in the Middle Carboniferous through Permian, when the continent of Eurasia completed its consolidation. The respective metallogenic events included formation of Cu-Ni picritic dolerites (C2–3), as well as large-scale gold and Mo-W deposits in granites (P1–2).
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Barefoot, John, Elisabeth S. Nadin, Rainer J. Newberry et Alfredo Camacho. « Rock and age relationships within the Talkeetna forearc accretionary complex in the Nelchina area, southern Alaska ». Canadian Journal of Earth Sciences 57, no 6 (juin 2020) : 709–24. http://dx.doi.org/10.1139/cjes-2018-0268.
Texte intégralRésumé :
Subduction zone processes are challenging to study because of the rarity of good exposures and the complexity of rock relationships within accretionary prisms. We report the results of field mapping and petrographic, geochemical, and geochronological analyses of the McHugh Complex accretionary prism mélange in south-central Alaska that was recently exposed due to retreat of the Nelchina Glacier. Our new mapping and analyses of the mélange, as well as adjacent Talkeetna arc intrusives, suggests that the previously mapped trace of the Border Ranges fault should shift northward in this location. Detailed petrographic analysis places this mélange exposure with the Potter Creek assemblage of the McHugh Complex. Blocks of pillow lavas within the mélange have both mid-ocean ridge basalt and intra-plate geochemical affinities, attesting to the complex relations of subduction-zone inputs in an alternating erosive–accretionary margin. A new zircon U–Pb age and geochemical analyses of a set of felsic dikes that cross-cut the accretionary sequence provide constraints on the regional tectonic evolution, including near-trench plutonism associated with the migration of a subducting spreading ridge along the southern Alaska margin during the Paleocene–Eocene. The McHugh section and cross-cutting dikes in this location are pervasively hydrothermally altered, which we attribute to elevated temperatures related to ridge subduction. Late-stage motion along the Border Ranges fault system, which is also recorded in the area, may also have contributed to the widespread alteration. Our data indicate that the Talkeetna volcanic arc and associated accretionary prism sediments were in their current configuration by 55 Ma.
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Sodoudi, F., A. Brüstle, T. Meier, R. Kind et W. Friederich. « Receiver function images of the Hellenic subduction zone and comparison to microseismicity ». Solid Earth 6, no 1 (4 février 2015) : 135–51. http://dx.doi.org/10.5194/se-6-135-2015.
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Abstract. New combined P receiver functions and seismicity data obtained from the EGELADOS network employing 65 seismological stations within the Aegean constrained new information on the geometry of the Hellenic subduction zone. The dense network and large data set enabled us to estimate the Moho depth of the continental Aegean plate across the whole area. Presence of a negative contrast at the Moho boundary indicating the serpentinized mantle wedge above the subducting African plate was seen along the entire forearc. Furthermore, low seismicity was observed within the serpentinized mantle wedge. We found a relatively thick continental crust (30–43 km) with a maximum thickness of about 48 km beneath the Peloponnese Peninsula, whereas a thinner crust of about 27–30 km was observed beneath western Turkey. The crust of the overriding plate is thinning beneath the southern and central Aegean and reaches 23–27 km. Unusual low Vp / Vs ratios were estimated beneath the central Aegean, which most likely represent indications on the pronounced felsic character of the extended continental Aegean crust. Moreover, P receiver functions imaged the subducted African Moho as a strong converted phase down to a depth of about 100 km. However, the converted Moho phase appears to be weak for the deeper parts of the African plate suggesting nearly complete phase transitions of crustal material into denser phases. We show the subducting African crust along eight profiles covering the whole southern and central Aegean. Seismicity of the western Hellenic subduction zone was taken from the relocated EHB-ISC catalogue, whereas for the eastern Hellenic subduction zone, we used the catalogues of manually picked hypocentre locations of temporary networks within the Aegean. Accurate hypocentre locations reveal a significant change in the dip angle of the Wadati–Benioff zone (WBZ) from west (~ 25°) to the eastern part (~ 35°) of the Hellenic subduction zone. Furthermore, a zone of high deformation can be characterized by a vertical offset of about 40 km of the WBZ beneath the eastern Cretan Sea. This deformation zone may separate a shallower N-ward dipping slab in the west from a steeper NW-ward dipping slab in the east. In contrast to hypocentre locations, we found very weak evidence for the presence of the slab at larger depths in the P receiver functions, which may result from the strong appearance of the Moho multiples as well as eclogitization of the oceanic crust. The presence of the top of a strong low-velocity zone at about 60 km depth in the central Aegean may be related to the asthenosphere below the Aegean continental lithosphere and above the subducting slab. Thus, the Aegean mantle lithosphere seems to be 30–40 km thick, which means that its thickness increased again since the removal of the mantle lithosphere about 15 to 35 Ma ago.
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Hack, Alistair C., et Alan B. Thompson. « Density and Viscosity of Hydrous Magmas and Related Fluids and their Role in Subduction Zone Processes ». Journal of Petrology 52, no 7-8 (21 septembre 2010) : 1333–62. http://dx.doi.org/10.1093/petrology/egq048.
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Glasby, G. P. « Hydrothermal manganese deposits in island arcs and related to subduction processes : A possible model for genesis ». Ore Geology Reviews 4, no 1-2 (novembre 1988) : 145–53. http://dx.doi.org/10.1016/0169-1368(88)90010-8.
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Kononov, M. V., et L. I. Lobkovsky. « Influence of the upper-mantle convective cell and related Pacific plate subduction on Arctic tectonics in the late Cretaceous–Cenozoic ». Геотектоника, no 6 (17 novembre 2019) : 27–45. http://dx.doi.org/10.31857/s0016-853x2019627-45.
Texte intégralRésumé :
Abstract The paper considers the history of the spreading of the Eurasian basin. The sharp deceleration of the spreading rate in the Eocene about 46 million years ago, which is fixed by the distribution of linear magnetic anomalies, is noted. That jump in velocity is clarified from the perspective of the geodynamic model but shouldnt be explained by the northern motion of Greenland. The geodynamic processes of the Pacific subduction zone generate an upper mantle convective cell with return flow dragging the Arctic continental lithosphere in the direction of the Pacific subduction zone. The geodynamic mechanism is confirmed by seismic tomographic mantle sections of the northeastern margin of Asia and the numerical model of the upper mantle convection of the active continental margin. It is the activity of the upper mantle convective return cell, which is determined by the runoff volume and, ultimately, the speed and direction of the Kula plate and Pacific plate subduction vectors in the subduction zone, affects tectonics and kinematics of the plates of the Eurasian basin. In the Middle CretaceousMiddle Eocene and for about 73 Ma the return cell has been active, since the Kula and Pacific plates move north and submerged orthogonally beneath the Central Arctic. After the Middle Eocene geodynamic reorganization about 47.5 million years ago, oceanic plates in the Pacific Ocean begin to move to the northwest. As a result, the transport of the oceanic Pacific Ocean lithospheric substance to the arctic convective return cell has practically ceased. After the restructuring, the spreading of the Eurasian basin slowed down about 46 million years ago to an ultra-slow regime. The main tectonic and geodynamic consequences of applying the proposed geodynamic model for the Arctic in the Late CretaceousCenozoic are considered.
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Peacock, Simon M. « Creation and preservation of subduction-related inverted metamorphic gradients ». Journal of Geophysical Research 92, B12 (1987) : 12763. http://dx.doi.org/10.1029/jb092ib12p12763.
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PHILLIPS, BETHAN A., ANDREW C. KERR et RICHARD BEVINS. « A re-appraisal of the petrogenesis and tectonic setting of the Ordovician Fishguard Volcanic Group, SW Wales ». Geological Magazine 153, no 3 (28 juillet 2015) : 410–25. http://dx.doi.org/10.1017/s0016756815000461.
Texte intégralRésumé :
AbstractThe Fishguard Volcanic Group represents an excellently preserved example of a volcanic sequence linked to the closure of the Iapetus Ocean. This study re-examines the petrogenesis and proposed tectonic setting for the Llanvirn (467–458 Ma) Fishguard Volcanic Group, South Wales, UK. New major and trace element geochemical data and petrographic observations are used to re-evaluate the magma chamber processes, mantle melting and source region. The new data reveal that the Fishguard Volcanic Group represents a closely related series of basalts, basaltic andesites, dacites and rhyolites originating from a spinel lherzolite source which had been modified by subduction components. The rocks of the Fishguard Volcanic Group are co-genetic and the felsic members are related to the more primitive basalts mainly by low-pressure fractional crystallization. The geochemistry of the lavas was significantly influenced by subduction processes associated with a coeval arc, while significant amounts of assimilation of continental crust along with fractional crystallization appear to have contributed to the compositions of the most evolved lavas. The Fishguard Volcanic Group was erupted into a back-arc basin where extensive rifting but no true seafloor spreading had occurred.
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Guo, Zhengfu, et Marjorie Wilson. « Late Oligocene–early Miocene transformation of postcollisional magmatism in Tibet ». Geology 47, no 8 (10 juin 2019) : 776–80. http://dx.doi.org/10.1130/g46147.1.
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Abstract Uplift of the Tibetan Plateau is thought to be one of the most important orogenic and climate forcing events of the Cenozoic Era, associated with geodynamic changes related to India-Asia collision and subsequent continental lithosphere subduction. However, the fate and scale of the subducted continental lithosphere segments remain highly controversial. Using a comprehensive compilation of the spatiotemporal distribution of postcollisional magmatic rocks across Tibet, together with new geochemical and Sr-Nd-Pb isotopic data and modeling simulations, we propose a holistic, two-stage evolutionary model to explain the link between genesis of the magmas and continental subduction. The magmatism prior to 25 Ma resulted from continuous upwelling of a carbonate-rich upper-mantle plume induced by northward underthrusting of Indian oceanic and continental lithosphere with its cover of Tethyan platform carbonate sediments, whereas magmatism after 25 Ma was related to opposing north-directed and south-directed continental subduction. Our model indicates a transformation in the distribution and nature of the magmatism in Tibet at ca. 25 Ma, which reflects a significant change in the Himalayan-Tibetan orogen and associated mantle dynamic processes in the early Miocene. Understanding this transformation could have important implications for the utility of the Himalayan-Tibetan system as a modern analogue for ancient orogens.
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Mora-Klepeis, Gabriela, et Fred W. McDowell. « Late Miocene calc-alkalic volcanism in northwestern Mexico : an expression of rift or subduction-related magmatism ? » Journal of South American Earth Sciences 17, no 4 (décembre 2004) : 297–310. http://dx.doi.org/10.1016/j.jsames.2004.08.001.
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Storey, B. C., P. A. R. Nell et T. H. Tranter. « Plate subduction and related deformation : a 600 km crustal transect across the Antarctic Peninsula magmatic arc ». Tectonophysics 191, no 3-4 (juin 1991) : 443. http://dx.doi.org/10.1016/0040-1951(91)90096-b.
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Wakita, Koji, Takanori Nakagawa, Masahiro Sakata, Natsuki Tanaka et Nozomu Oyama. « Phanerozoic accretionary history of Japan and the western Pacific margin ». Geological Magazine 158, no 1 (18 décembre 2018) : 13–29. http://dx.doi.org/10.1017/s0016756818000742.
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AbstractIt is generally accepted that oceanic plate subduction has occurred along the eastern margin of Asia since about 500 Ma ago. Therefore, the Japanese Islands have a >500 Ma history of oceanic plate subduction in their geological records. In this paper, the accretionary history of the Japanese Islands is divided into six main stages based on the mode and nature of tectonic events and the temporal gaps in the development of accretionary processes. In the first stage, oceanic plate subduction and accretion started along the margin of Gondwana. After detachment of the North and South China blocks in Devonian time, accretionary complexes developed along island arcs offshore of the South and North China blocks. After the formation of back arc basins such as the Japan Sea, accretionary processes occurred only along the limited convergent margin, e.g. Nankai Trough. Detrital zircons of sandstones revealed the accretionary history of Japan. An evaluation of a comprehensive dataset on detrital zircon populations shows that the observed temporal gaps in the development of the Japanese accretionary complexes were closely related to the intensity of igneous activity in their provenance regions. Age distributions of detrital zircons in the accretionary complexes of Japan change before and after the Middle Triassic period, when the collision of the South and North China blocks occurred.
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Ji, Tianxiao, et Zhigang Zeng. « Trace Element Evidence of Subduction-Modified Mantle Material in South Mid-Atlantic Ridge 18–21°S Upper Mantle ». Journal of Marine Science and Engineering 11, no 2 (17 février 2023) : 441. http://dx.doi.org/10.3390/jmse11020441.
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Mid-ocean ridge basalts (MORBs), produced at mid-ocean ridge where the continents and subduction zones are distant, are the product of partial melting of the upper mantle and their chemical composition can provide information about the mantle itself. The geochemical characteristics of MORBs enable us to be more informed about the geological processes of the upper mantle below the mid-ocean ridge, and assist us in understanding mantle heterogeneity and geodynamic processes. In this paper, new data of major elements, trace elements, and Nd-Hf isotopes of south mid-Atlantic ridge (SMAR) 18–21°S MORBs are presented. TAS diagram shows that the samples belong to subalkaline basalt compositional field. Trace elements (e.g., (La/Sm)N = 0.49–0.79) show that the samples are N-MORBs. However, the primitive mantle-normalized trace element patterns showed that the studied samples were clearly enriched in Rb, U, Pb, and other fluid-mobile elements. Meanwhile, the trace element ratios, such as Nb/U and Ce/Pb, are also significantly different from the typical N-MORB. Combined with the Nd-Hf isotopic composition, we propose that these anomalies are not related to continental crust material, delaminated subcontinental lithospheric mantle (SCLM), recycled sediments, direct supply of mantle plume, nor are they the result of subduction directly affecting the mantle source, but are caused by the incorporation of mantle material modified by subduction.
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Liu, Liang, Lei Kang, YuTing Cao et WenQiang Yang. « Early Paleozoic granitic magmatism related to the processes from subduction to collision in South Altyn, NW China ». Science China Earth Sciences 58, no 9 (6 août 2015) : 1513–22. http://dx.doi.org/10.1007/s11430-015-5151-1.
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