Journal articles: 'Oman Moho Transition Zone'

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BOUDIER, F., and A. NICOLAS. "Nature of the Moho Transition Zone in the Oman Ophiolite." Journal of Petrology 36, no. 3 (1995): 777–96. http://dx.doi.org/10.1093/petrology/36.3.777.

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Jousselin, David, Luiz F. G. Morales, Marie Nicolle, and Aurore Stephant. "Gabbro layering induced by simple shear in the Oman ophiolite Moho transition zone." Earth and Planetary Science Letters 331-332 (May 2012): 55–66. http://dx.doi.org/10.1016/j.epsl.2012.02.022.

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Michibayashi, Katsuyoshi, and Tatsuya Oohara. "Olivine fabric evolution in a hydrated ductile shear zone at the Moho Transition Zone, Oman Ophiolite." Earth and Planetary Science Letters 377-378 (September 2013): 299–310. http://dx.doi.org/10.1016/j.epsl.2013.07.009.

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Rajendran, Sankaran, and Sobhi Nasir. "Mapping of Moho and Moho Transition Zone (MTZ) in Samail ophiolites of Sultanate of Oman using remote sensing technique." Tectonophysics 657 (August 2015): 63–80. http://dx.doi.org/10.1016/j.tecto.2015.06.023.

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Jousselin, David, Adolphe Nicolas, Françoise Boudier, Laurie Reisberg, Mathilde Henri, and Marie Nicolle. "Formation of the Moho transition zone in the Oman ophiolite, and comparison with sub-Moho melt lenses at fast spreading ridges." Tectonophysics 821 (December 2021): 229148. http://dx.doi.org/10.1016/j.tecto.2021.229148.

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Korenaga, Jun, and Peter B. Kelemen. "Origin of gabbro sills in the Moho transition zone of the Oman ophiolite: Implications for magma transport in the oceanic lower crust." Journal of Geophysical Research: Solid Earth 102, B12 (1997): 27729–49. http://dx.doi.org/10.1029/97jb02604.

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Rollinson, Hugh, and Jacob Adetunji. "Mantle podiform chromitites do not form beneath mid-ocean ridges: A case study from the Moho transition zone of the Oman ophiolite." Lithos 177 (September 2013): 314–27. http://dx.doi.org/10.1016/j.lithos.2013.07.004.

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Negishi, Hironori, Shoji Arai, Hisayoshi Yurimoto, et al. "Sulfide-rich dunite within a thick Moho transition zone of the northern Oman ophiolite: Implications for the origin of Cyprus-type sulfide deposits." Lithos 164-167 (April 2013): 22–35. http://dx.doi.org/10.1016/j.lithos.2012.11.024.

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Rospabé, Mathieu, Mathieu Benoit, Georges Ceuleneer, Florent Hodel, and Mary-Alix Kaczmarek. "Extreme geochemical variability through the dunitic transition zone of the Oman ophiolite: Implications for melt/fluid-rock reactions at Moho level beneath oceanic spreading centers." Geochimica et Cosmochimica Acta 234 (August 2018): 1–23. http://dx.doi.org/10.1016/j.gca.2018.05.012.

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Al-Lazki, Ali I., Dogan Seber, Eric Sandvol, and Muawia Barazangi. "A crustal transect across the Oman Mountains on the eastern margin of Arabia." GeoArabia 7, no. 1 (2002): 47–78. http://dx.doi.org/10.2113/geoarabia070147.

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ABSTRACT The unique tectonic setting of the Oman Mountains and the Semail Ophiolite, together with ongoing hydrocarbon exploration, have focused geological research on the sedimentary and ophiolite stratigraphy of Oman. However, there have been few investigations of the crustal-scale structure of the eastern Arabian continental margin. In order to rectify this omission, we made a 255-km-long, southwesterly oriented crustal transect of the Oman Mountains from the Coastal Zone to the interior Foreland via the 3,000-m-high Jebel Akhdar. The model for the upper 8 km of the crust was constrained using 152 km of 2-D seismic reflection profiles, 15 exploratory wells, and 1:100,000- to 1:250,000-scale geological maps. Receiver-function analysis of teleseismic earthquake waveform data from three temporary digital seismic stations gave the first reliable estimates of depth-to-Moho. Bouguer gravity modeling provided further evidence of depths to the Moho and metamorphic basement. Four principal results were obtained from the transect. (1) An interpreted mountain root beneath Jebel Akhdar has a lateral extent of about 60 km along the transect. The depth-to-Moho of 41 to 44 km about 25 km southwest of Jebel Akhdar increased to 48 to 51 km on its northeastern side but decreased to 39 to 42 km beneath the coastal plain farther to the northeast. (2) The average depth to the metamorphic basement was inferred from Bouguer gravity modeling to be 9 km in the core of Jebel Akhdar and immediately to the southwest. A relatively shallow depth-to-basement of 7 to 8 km coincided with the Jebel Qusaybah anticline south of the Hamrat Ad Duru Range. (3) Based on surface, subsurface, and gravity modeling, the Nakhl Ophiolite block extends seaward for approximately 80 km from its most southerly outcrop. It has an average thickness of about 5 km, whereas ophiolite south of Jebel Akhdar is only 1 km thick. The underlying Hawasina Sediments are between 2 and 3 km thick in the Hamrat Ad Duru Zone, and 2 km thick in the Coastal Zone. (4) Southwest of Jebel Akhdar, reactivated NW-oriented strike-slip basement faults that deformed Miocene to Pliocene sediments were inferred from the interpretation of seismic reflection profiles.

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Kang, Hyunsun, YoungHee Kim, Junkee Rhie, Tae-Seob Kang, and Marco Brenna. "Seismic crustal structure beneath Jeju Volcanic Island, South Korea from teleseismic P-receiver functions." Geophysical Journal International 227, no. 1 (2021): 58–75. http://dx.doi.org/10.1093/gji/ggab211.

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SUMMARY Jeju Island is an intraplate volcanic island with enigmatic origins, located on the continental shelf south of the Korean Peninsula. A dense temporary seismic array, operated on Jeju Island from 2013 to 2015, revealed several important constraints on the magma plumbing system of Jeju Island. In this study, we determined the deep crustal seismic structure beneath Jeju Island from the teleseismic P-to-S converted phases (receiver functions) recorded from 20 temporary and three permanent stations. We removed the contribution of near-surface reverberations in the resulting receiver functions by applying a resonance removal filter. We estimated crustal P-to-S velocity ratio (VP/VS) and discontinuity depth to provide teleseismic constraints on the composition and structure. We observed two major seismic discontinuities, which are the upper boundaries of a mid-to-lower crustal low-velocity zone (LVZ) and the Moho transition zone. The depth to the upper boundary of the LVZ is deep in the west and southeast (24–30 km) and shallow in the northeast (8–11 km). The LVZ can be interpreted as an extensively distributed residual magma plumbing system, with magma batches stalled at various levels and at various degrees of crystallization, consistent with the chemical diversity of Jeju magmas. The seismic characteristics of the Moho transition zone vary greatly among regions. The top interface of the Moho transition zone is at a wide range of depth (26–40 km), and is shallow at 26–29 km depths beneath central Jeju, suggesting a complex Moho topography. The presence of mafic cumulates and partially molten mushes may contribute to the observed shallow seismic discontinuity at a depth of 26–29 km. The lack of obvious crustal thickening below the shield volcano, Mt Halla, may be associated with mantle upwelling or presence of mafic underplating and cumulates below Jeju. Spatial variations of crustal VP/VS represent highly heterogeneous crustal composition, resulting from magma differentiation during the evolution of the island.

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Pistone, Mattia, Othmar Müntener, Luca Ziberna, György Hetényi, and Alberto Zanetti. "Report on the ICDP workshop DIVE (Drilling the Ivrea–Verbano zonE)." Scientific Drilling 23 (November 30, 2017): 47–56. http://dx.doi.org/10.5194/sd-23-47-2017.

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Abstract. The Ivrea–Verbano Zone is the most complete, time-integrated crust–upper mantle archive in the world. It is a unique target for assembling data on the deep crust and the Moho transition zone and testing several hypotheses of formation, evolution, and modification of the continental crust through space and time across the Earth. The ICDP workshop Drilling the Ivrea–Verbano zonE (DIVE), held in Baveno, Italy, from 1 to 5 May 2017, focused on the scientific objectives and the technical aspects of drilling and sampling in the Ivrea–Verbano Zone at depth. A total of 47 participants from 9 countries with a wide variety of scientific and/or drilling expertise attended the meeting. Discussion on the proposed targets sharpened the main research lines and led to working groups and the necessary technical details to compile the full drilling proposal. The participants of the workshop concluded that four drilling operations in the Val Sesia and Val d'Ossola crustal sections represent the scientifically most promising solution to achieve the major goals within DIVE to unravel the physico-chemical properties and architecture of the lower continental crust towards the crust–mantle (Moho) transition zone.

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Prathigadapa, Raju, Subrata Das Sharma, and Durbha Sai Ramesh. "Seismic Evidence for Proterozoic Collisional Episodes along Two Geosutures within the Southern Granulite Province of India." Lithosphere 2020, no. 1 (2020): 1–20. http://dx.doi.org/10.2113/2020/8861007.

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Abstract The Southern Granulite Province of India had witnessed episodes of multiple tectonic activities, leading to sparsely preserved surface geological features. The present study is focused on unraveling the geodynamic evolution of this terrain through measurement of Moho depth and Vp/Vs ratio using data from a large number of broadband seismic stations. These results unambiguously establish three domains distinct in Moho depth and crustal composition. An intermediate to felsic crust with a 7–10 km step-in-Moho is delineated across the Moyar–Bhavani region. Anomalously high felsic crust with abrupt jump in Moho (~8–10 km) together with a dipping feature at deeper level characterizes the transition from eastern to southern segments of the Jhavadi–Kambam–Trichur region. By contrast, the central zone hosting the Palghat–Cauvery shear zone records uniform felsic crust and flat Moho. Drawing analogy from similar results in different parts of the globe, juxtaposition of petrologically dissimilar crustal blocks characterized by varied depths to the Moho is argued to point towards unambiguous presence of two distinct geosutures in the study area: one along the Moyar–Bhavani region and the other across the Jhavadi–Kambam–Trichur. This inference is corroborated by the presence of layered meta-anorthosite, related rock suites, and mafic-ultramafic bodies, supporting the view of a suprasubduction setting in the Moyar–Bhavani region. The Jhavadi–Kambam–Trichur area is marked by operation of the Wilson cycle by way of sparsely preserved geological features such as the presence of ophirags (ophiolite fragments), alkali syenites, and carbonatites. Geochronological results suggest that the suturing along Moyar–Bhavani took place during the Paleoproterozoic and that along Jhavadi–Kambam–Trichur was during the late Neoproterozoic.

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Tsai, C. J. "A method to analyze and verify deep crustal reflections offshore Costa Rica." GEOPHYSICS 50, no. 2 (1985): 196–206. http://dx.doi.org/10.1190/1.1441909.

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A multichannel seismic reflection profile across the oceanic crust seaward of the Middle America Trench off the Nicoya Peninsula, Costa Rica, shows discontinuous, low‐frequency events at 6.5 to 7.0 s. These events might first be interpreted as reflections from the Moho. However, careful analysis of the seismic data suggests that these events represent three‐dimensional (3-D) scattered energy from the rough basaltic basement. Velocity analysis indicates that root‐mean‐square (rms) velocities for these deep “reflection events” are too low to emanate from the Moho. Also, the ghost separation caused by the streamer depth decreases for increasing record time, suggesting that incident angle for these “reflections” increases with time. Furthermore, these events are approximately 13 dB stronger than would be expected for a Moho reflection. Common‐depth‐point (CDP) stacking and velocity filtering were used to attenuate the scattered noise and sideswipe from the basalt. The results show a 21 dB total reduction of scattered energy. However, Moho reflections still cannot be discerned. The results suggest (1) ambient noise after processing is 20 dB below the expected Moho level and is not a factor in detection of the Moho; (2) Moho reflectivity may be smaller than 0.1 (reflectivity is calculated from assumed velocities and densities) and could be as small as 0.05 (the detection threshold); (3) the Moho may not be a discrete reflector and may therefore represent a transition zone; and (4) Moho events may be disorganized by transmission through rough basalt so the CDP stacking process is not effective.

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Mauser, E. C., J. Gephart, T. Latham, et al. "COCORP Arizona transect: Strong crustal reflections and offset Moho beneath the transition zone." Geology 15, no. 12 (1987): 1103. http://dx.doi.org/10.1130/0091-7613(1987)15<1103:catscr>2.0.co;2.

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O'Leary, D. M., R. M. Clowes, and R. M. Ellis. "Crustal velocity structure in the southern Coast Belt, British Columbia." Canadian Journal of Earth Sciences 30, no. 12 (1993): 2389–403. http://dx.doi.org/10.1139/e93-207.

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We applied an iterative combination of two-dimensional traveltime inversion and amplitude forward modelling to seismic refraction data along a 350 km along-strike profile in the Coast Belt of the southern Canadian Cordillera to determine crust and upper mantle P-wave velocity structure. The crustal model features a thin (0.5–3.0 km) near-surface layer with an average velocity of 4.4 km/s, and upper-, middle-, and lower-crustal strata which are each approximately 10 km thick and have velocities ranging from 6.2 to 6.7 km/s. The Moho appears as a 2 km thick transitional layer with an average depth of 35 km and overlies an upper mantle with a poorly constrained velocity of over 8 km/s. Other interpretations indicate that this profile lies within a collision zone between the Insular superterrane and the ancient North American margin and propose two collision-zone models: (i) crustal delamination, whereby the Insular superterrane was displaced along east-vergent faults over the terranes below; and (ii) crustal wedging, in which interfingering of Insular rocks occurs throughout the crust. The latter model involves thick layers of Insular material beneath the Coast Belt profile, but crustal velocities indicate predominantly non-Insular material, thereby favoring the crustal delamination model. Comparisons of the velocity model with data from the proximate reflection lines show that the top of the Moho transition zone corresponds with the reflection Moho. Comparisons with other studies suggest that likely sources for intracrustal wide-angle reflections observed in the refraction data are structural features, lithological contrasts, and transition zones surrounding a region of layered porosity in the crust.

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Chi, Tsung-Chih, Young-Fo Chang, and Bor-Shouh Huang. "Receiver Function Imaging of the Crustal Structure Beneath Northern Taiwan Using Dense Linear Arrays." Geosciences 12, no. 3 (2022): 136. http://dx.doi.org/10.3390/geosciences12030136.

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In order to realize the crustal structure in Taiwan, the receiver function method was used to analyze the teleseismic waveforms recorded by two orthogonal broadband linear arrays deployed in northern Taiwan in the east–west and south–north directions by the TAiwan Integrated GEodynamics Research (TAIGER) project from 2007 to 2009. By incorporation with Common Conversion Point (CCP) stacking, the Moho discontinuities beneath northern Taiwan were imaged. Based on the CCP stack of receiver functions in the east–west direction array, a collision boundary between the Philippine Sea Plate and the Eurasian Plate appears at the east of Taiwan. The Moho depth of the Eurasian Plate in west Taiwan is flat and 30 km; the Moho depth of the Philippine Sea Plate below the Central Mountain Range is about 55 km; in the east, the Moho depth of the Ryukyu arc is about 40 km. The south–north profile shows a brittle–ductile transition zone at depths of 15–20 km beneath central Taiwan from south to north. Moreover, the Moho depth of the Eurasian Plate is about 20–25 km in northern Taiwan. The Moho depth appears to deepen from north to south. The deepest Moho is located at the junction of the two profile lines, the Philippine Sea Plate, and has a depth of 60 km. According to these Moho depths, the crustal structure is thin and flat in the west part of northern Taiwan which is similar to the thin-skin model. However, the lithosphere is deformed and forms the mountain root in the east part which is similar to the lithospheric collision model.

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KASAHARA, Junzo, Sadao UNOU, Kayoko TSURUGA, Toshihiro IKE, and Keita KODA. "Characteristics of Moho Reflections Identified by MCS Reflection Records in the Western Pacific Ocean and Effects of Moho Transition Zone Properties." Chigaku Zasshi (Jounal of Geography) 117, no. 1 (2008): 5–44. http://dx.doi.org/10.5026/jgeography.117.5.

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Ingale, Vaibhav, and Satish C. Singh. "Insights from synthetic seismogram modelling study of oceanic lower crust and Moho Transition Zone." Tectonophysics 816 (October 2021): 229030. http://dx.doi.org/10.1016/j.tecto.2021.229030.

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Heydarizadeh Shali, H., D. Sampietro, A. Safari, M. Capponi, and A. Bahroudi. "Fast collocation for Moho estimation from GOCE gravity data: the Iran case study." Geophysical Journal International 221, no. 1 (2020): 651–64. http://dx.doi.org/10.1093/gji/ggaa026.

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SUMMARY The study of the discontinuity between crust and mantle beneath Iran is still an open issue in the geophysical community due to its various tectonic features created by the collision between the Iranian and Arabian Plate. For instance in regions such as Zagros, Alborz or Makran, despite the number of studies performed, both by exploiting gravity or seismic data, the depth of the Moho and also interior structure is still highly uncertain. This is due to the complexity of the crust and to the presence of large short wavelength signals in the Moho depth. GOCE observations are capable and useful products to describe the Earth’s crust structure either at the regional or global scale. Furthermore, it is plausible to retrieve important information regarding the structure of the Earth’s crust by combining the GOCE observations with seismic data and considering additional information. In the current study, we used as observation a grid of second radial derivative of the anomalous gravitational potential computed at an altitude of 221 km by means of the space-wise approach, to study the depth of the Moho. The observations have been reduced for the gravitational effects of topography, bathymetry and sediments. The residual gravity has been inverted accordingly to a simple two-layer model. In particular, this guarantees the uniqueness of the solution of the inverse problem which has been regularized by means of a collocation approach in the frequency domain. Although results of this study show a general good agreement with seismically derived depths with a root mean square deviation of 6 km, there are some discrepancies under the Alborz zone and also Oman sea with a root mean square deviation up 10 km for the former and an average difference of 3 km for the latter. Further comparisons with the natural feature of the study area, for instance, active faults, show that the resulting Moho features can be directly associated with geophysical and tectonic blocks.

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UMINO, Susumu, Nobuo GESHI, Hidenori KUMAGAI, and Kiyoyuki KISIMOTO. "Do Off-ridge Volcanoes on the East Pacific Rise Originate from the Moho Transition Zone?" Journal of Geography (Chigaku Zasshi) 117, no. 1 (2008): 190–219. http://dx.doi.org/10.5026/jgeography.117.190.

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Sodoudi, F., A. Bruestle, T. Meier, R. Kind, and W. Friederich. "New constraints on the geometry of the subducting African plate and the overriding Aegean plate obtained from P receiver functions and seismicity." Solid Earth Discussions 5, no. 1 (2013): 427–61. http://dx.doi.org/10.5194/sed-5-427-2013.

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Abstract. New combined P receiver functions and seismicity data obtained from the EGELADOS network employing 65 stations within the Aegean constrained new information on the geometry of the Hellenic subduction zone. The dense network and large dataset enabled us to accurately estimate the Moho 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 clearly 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 Peloponnesus 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 (Moho depth 23–27 km). Moreover, P receiver functions significantly imaged the subducted African Moho as a strong converted phase down to a depth of 180 km. However, the converted Moho phase appears to be weak for the deeper parts of the African plate suggesting reduced dehydration and nearly complete phase transitions of crustal material into denser phases. We show the subducting African crust along 8 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 hypocenter locations of temporary networks within the Aegean. P receiver function profiles significantly revealed in good agreement with the seismicity a low dip angle slab segment down to 200 km depth in the west. Even though, the African slab seems to be steeper in the eastern Aegean and can be followed down to 300 km depth implying lower temperatures and delayed dehydration towards larger depths in the eastern slab segment. Our results showed that the transition between the western and eastern slab segments is located beneath the southeastern Aegean crossing eastern Crete and the Karpathos basin. High resolution P receiver functions also clearly resolved the top of a strong low velocity zone (LVZ) at about 60 km depth. This LVZ is interpreted as 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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Cook, Frederick A. "The reflection Moho beneath the southern Canadian Cordillera." Canadian Journal of Earth Sciences 32, no. 10 (1995): 1520–30. http://dx.doi.org/10.1139/e95-124.

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The transition from the crust to the mantle beneath the Canadian portion of the North American Cordillera varies in depth, geometry, and tectonic age across the orogen. These variations are rarely spatially related to the positions of morphologic or tectonic belts based on surface geology, nor to nearly 25 km of structural relief identified in outcrop and on seismic reflection data. The Moho in this region is thus interpreted to be a long-lived feature, perhaps as old as Proterozoic in the eastern part of the Cordillera, that probably has been active as a structural boundary during periods of crustal contraction and subsequent crustal stretching. Recognition of the Moho and lower crust as a zone of localized tectonic activity provides a partial explanation for the problem of where regional detachments that underlie the foreland thrust and fold belt go as they project westward to deep structural levels beneath the interior of the orogen: they likely project to the base of the crust, where they flatten and cause imbrication of crustal rocks.

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Janik, Tomasz, Vitaly Starostenko, Paweł Aleksandrowski, et al. "Lithospheric Structure of the East European Craton at the Transition from Sarmatia to Fennoscandia Interpreted from the TTZ-South Seismic Profile (SE Poland to Ukraine)." Minerals 12, no. 2 (2022): 112. http://dx.doi.org/10.3390/min12020112.

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The TTZ-South seismic profile follows the Teisseyre-Tornquist zone (TTZ) at the SW margin of the East European craton (EEC). Investigation results reveal the upper lithospheric structure as representing the NW-vergent, NE-SW striking overthrust-type, Paleoproterozoic (~1.84–1.8 Ga) Fennoscandia-Sarmatia suture. The Sarmatian segment of the EEC comprises two crustal-scale tectonic thrust slices: the Moldavo-Podolian and Lublino-Volhynian basement units, overriding the northerly located Lysogoro-Radomian unit of Fennoscandian affinity. The combined results of the TTZ-South and other nearby deep seismic profiles are consistent with a continuation of the EEC cratonic basement across the TTZ to the SW and its plunging into the deep substratum of the adjacent Paleozoic platform. Extensional deformation responsible for the formation of the mid to late Proterozoic (~1.4–0.6 Ga), SW-NE trending Orsha-Volhynia rift basin is probably also recorded. The thick Ediacaran succession deposited in the rift was later tectonically thickened due to Variscan deformation. The Moho depth varies between 37 and 49 km, resulting in the thinnest crust in the SE, sharp depth changes across the TTZ, and slow shallowing from 49 to 43 km to the NW. The abrupt Moho depth increase from 43 to 49 km is considered to reflect the overlying lower crust tectonic duplication within the suture zone.

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Li, Xuelei, Zhuo Jia, Nanqiao Du, Yi Xu, and Gongbo Zhang. "Structural Characteristics of Moho Surface Based on Time Series Function of Natural Earthquakes." Remote Sensing 13, no. 4 (2021): 763. http://dx.doi.org/10.3390/rs13040763.

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Remote sensing is a non-contact, long-distance detection technology. The reflection characteristics of a seismic wave can be used to detect remote and non-contact targets. Based on the reflection characteristics of a seismic wave, the underground structure in Tengchong Volcanic Area is explored. In order to further study the deep structure and magmatic activity of the crust in the volcanic area, we carried out a one-year mobile seismic observation. In this paper, nine broadband seismic stations were set up in the Tengchong Volcanic Area, and 3350 receiver function waveforms were collected. The crustal thickness, average wave velocity ratio, and Poisson’s ratio below these stations were calculated by the receiver function method, and the velocity structure near the Moho below these stations was evaluated. Combined with topographic data from SRTM3 (Shuttle Radar Topography Mission 3), this study reveals the dynamic relationship among crustal structure, crustal magmatism, and regional tectonic movement. Mantle upwelling plays an important role on the Moho uplift in the northern Tengchong Volcanic Area, and there are interconnected intracrustal magma chambers in the upper platform. The evaluation results of the Moho transition zone also indicate that the Dayingjiang fault is closely related to the tectonic activity of the Tengchong Volcanic fault.

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Ghosh, Biswajit, Tomoaki Morishita, Bidisa Sen Gupta, Akihiro Tamura, Shoji Arai, and Debaditya Bandyopadhyay. "Moho transition zone in the Cretaceous Andaman ophiolite, India: A passage from the mantle to the crust." Lithos 198-199 (June 2014): 117–28. http://dx.doi.org/10.1016/j.lithos.2014.03.027.

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Wang, Qin, Nickolai Bagdassarov, and Shaocheng Ji. "The Moho as a transition zone: A revisit from seismic and electrical properties of minerals and rocks." Tectonophysics 609 (December 2013): 395–422. http://dx.doi.org/10.1016/j.tecto.2013.08.041.

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Guo, Peng, Satish C. Singh, Venkata A. Vaddineni, Gerhard Visser, Ingo Grevemeyer, and Erdinc Saygin. "Nonlinear full waveform inversion of wide-aperture OBS data for Moho structure using a trans-dimensional Bayesian method." Geophysical Journal International 224, no. 2 (2020): 1056–78. http://dx.doi.org/10.1093/gji/ggaa505.

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SUMMARY Seismic full waveform inversion (FWI) is a powerful method for estimating quantitative subsurface physical parameters from seismic data. As the FWI is a nonlinear problem, the linearized approach updates model iteratively from an initial model, which can get trapped in local minima. In the presence of a high-velocity contrast, such as at Moho, the reflection coefficient and recorded waveforms from wide-aperture seismic acquisition are extremely nonlinear around critical angles. The problem at the Moho is further complicated by the interference of lower crustal (Pg) and upper mantle (Pn) turning ray arrivals with the critically reflected Moho arrivals (PmP). In order to determine velocity structure near Moho, a nonlinear method should be used. We propose to solve this strong nonlinear FWI problem at Moho using a trans-dimensional Markov chain Monte Carlo (MCMC) method, where the earth model between lower crust and upper mantle is ideally parametrized with a 1-D assumption using a variable number of velocity interfaces. Different from common MCMC methods that require determining the number of unknown as a fixed prior before inversion, trans-dimensional MCMC allows the flexibility for an automatic estimation of both the model complexity (e.g. the number of velocity interfaces) and the velocity–depth structure from the data. We first test the algorithm on synthetic data using four representative Moho models and then apply to an ocean bottom seismometer (OBS) data from the Mid-Atlantic Ocean. A 2-D finite-difference solution of an acoustic wave equation is used for data simulation at each iteration of MCMC search, for taking into account the lateral heterogeneities in the upper crust, which is constrained from traveltime tomography and is kept unchanged during inversion; the 1-D model parametrization near Moho enables an efficient search of the trans-dimensional model space. Inversion results indicate that, with very little prior and the wide-aperture seismograms, the trans-dimensional FWI method is able to infer the posterior distribution of both the number of velocity interfaces and the velocity–depth model for a strong nonlinear problem, making the inversion a complete data-driven process. The distribution of interface matches the velocity discontinuities. We find that the Moho in the study area is a transition zone of 0.7 km, or a sharp boundary with velocities from around 7 km s−1 in the lower crust to 8 km s−1 of the upper mantle; both provide nearly identical waveform match for the field data. The ambiguity comes from the resolution limit of the band-limited seismic data and limited offset range for PmP arrivals.

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Zelt, B. C., R. M. Ellis, R. M. Clowes, et al. "Crust and upper mantle velocity structure of the Intermontane belt, southern Canadian Cordillera." Canadian Journal of Earth Sciences 29, no. 7 (1992): 1530–48. http://dx.doi.org/10.1139/e92-121.

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As part of the Lithoprobe Southern Cordillera transect, seismic refraction data were recorded along a 330 km long strike profile in the Intermontane belt. An iterative combination of two-dimensional traveltime inversion and amplitude forward modelling was used to interpret crust and upper mantle P-wave velocity structure. This region is characterized by (i) a thin near-surface layer with large variations in velocity between 2.8 and 5.4 km/s, and low-velocity regions that correlate well with surface expressions of Tertiary sedimentary and volcanic rocks; (ii) an upper and middle crust with low average velocity gradient, possibly a weak low-velocity zone, and lateral velocity variations between 6.0 and 6.4 km/s; (iii) a distinctive lower crust characterized by significantly higher average velocities relative to midcrustal values beginning at 23 km depth, approximately 8 km thick with average velocities of 6.5 and 6.7 km/s at top and base; (iv) a depth to Moho, as defined by wide-angle reflections, that averages 33 km with variations up to 2 km; and (v) a Moho transition zone of depth extent 1–3 km, below which lies the upper mantle with velocities decreasing from 7.9 km/s in the south to 7.7 km/s in the north. Where the refraction line obliquely crosses a Lithoprobe deep seismic-reflection profile, good agreement is obtained between the interpreted reflection section and the derived velocity structure model. In particular, depths to wide-angle reflectors in the upper crust agree with depths to prominent reflection events, and Moho depths agree within 1 km. From this comparison, the upper and middle crust probably comprise the upper part of the Quesnellia terrane. The lower crust from the refraction interpretation does not show the division into two components, parautochthonous and cratonic North America, that is inferred from the reflection data, indicating that their physical properties are not significantly different within the resolution of the refraction data. Based on these interpretations, the lower lithosphere of Quesnellia is absent and presumably was recycled in the mantle. At a depth of ~ 16 km below the Moho, an upper mantle reflector may represent the base of the present lithosphere.

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Mayer, James R., and Larry D. Brown. "Signal penetration In the COCORP Basin and Range‐Colorado Plateau survey." GEOPHYSICS 51, no. 5 (1986): 1050–55. http://dx.doi.org/10.1190/1.1442160.

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Seismic sections from COCORP’s 1982 survey from the eastern Basin and Range to the Colorado Plateau of central Utah exhibit distinct cutoff times after which reflections are rare to nonexistent. In the eastern Basin and Range, this cutoff time is approximately 11 s (33 km), but beneath the central Colorado Plateau it exceeds 15 s (45 km). These depths appear to correspond to the base of the crust (Moho), with the lack of reflections from greater depths indicating mantle homogeneity. In general, absence of deeper reflections may be due either to geologic homogeneity or to lack of signal penetration. COCORP line 3 in the Colorado Plateau‐Basin and Range transition zone shows that variations in penetration are significant. On line 3 few reflections are evident below the structurally complex sedimentary cover, which extends to only 4 s (8 km), and virtually none are identifiable later than 7 s (21 km). Lateral variations in the temporal decay of source‐generated energy, together with estimates of corresponding ambient noise levels, infer that limited signal penetration, rather than geologic homogeneity, causes the lack of subsedimentary reflections within the transition zone. Deep reflections, if any, from beneath the westernmost Colorado Plateau appear to be masked by unusually high local environmental noise. In contrast, continued decay of source‐generated energy at traveltimes significantly greater than Moho arrival times within the Basin and Range and Colorado Plateau suggests (though it cannot confirm) that the underlying mantle is seismically transparent. Variations in signal penetration, such as those documented here, severely constrain interpretations of nonreflective zones in deep reflection data and should be a standard estimation in any interpretational procedure.

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Singh, D. D. "Quasi-continental oceanic structure beneath the Arabian Fan sediments from observed surface-wave dispersion studies." Bulletin of the Seismological Society of America 78, no. 4 (1988): 1510–21. http://dx.doi.org/10.1785/bssa0780041510.

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Abstract The fundamental and higher modes of surface waves generated by 31 earthquakes and recorded at seismographic stations along the western margins of India and Pakistan (Trivandrum, Kodaikanal, Goa, Bombay, Poona, New Delhi, Nillore, and Quetta) are used to estimate the crustal structure beneath the Arabian Fan sediments. The sedimentary thickness is determined from the observed higher mode data. The observed dispersion data suggest an increase in crustal thickness northward, from an approximately 16 km crustal thickness at the southern tip of India (Trivandrum) to an approximately 28 km crustal thickness at the regions of 20°N and above latitude, with an overlying 6 km sedimentary thickness. This gradual increase in crustal thickness in the northward direction and the attaining of quasi-continental oceanic (transition from continent to ocean) structure beneath the Arabian Fan sediments suggest that the Mohorovičić discontinuity may have resulted from a change in crystal structure due to increase of pressure and not a phase change. The same material exists beneath the Moho, and it does not represent the boundary between two different materials. The transition has given rise to crustal thickening in the northward direction. Another possible explanation is that the increase in hydrostatic pressure due to the load exerted by a large sedimentary column together with horizontal pressure caused by the collision of Indian and Eurasian plates has given rise to an increase in temperature near the Moho. Because of the thermal blanketing effect of this large sedimentary column, an inferred rise in temperature may have either changed the upper mantle into material with crustal-like velocity or may have given rise to metamorphism of earlier existing sedimentary rocks. An inferred high temperature near the Moho depth beneath the Arabian Fan sediments is in close agreement with the high attenuating zone at the shallow depth (30 to 45 km) as determined by Singh (1987).

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Benn, K., A. Nicolas, and I. Reuber. "Mantle—crust transition zone and origin of wehrlitic magmas: Evidence from the Oman ophiolite." Tectonophysics 151, no. 1-4 (1988): 75–85. http://dx.doi.org/10.1016/0040-1951(88)90241-7.

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Peirce, C., A. H. Robinson, A. M. Campbell, et al. "Seismic investigation of an active ocean–continent transform margin: the interaction between the Swan Islands Fault Zone and the ultraslow-spreading Mid-Cayman Spreading Centre." Geophysical Journal International 219, no. 1 (2019): 159–84. http://dx.doi.org/10.1093/gji/ggz283.

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SUMMARY The Swan Islands Transform Fault (SITF) marks the southern boundary of the Cayman Trough and the ocean–continent transition of the North American–Caribbean Plate boundary offshore Honduras. The CAYSEIS experiment acquired a 180-km-long seismic refraction and gravity profile across this transform margin, ∼70 km to the west of the Mid-Cayman Spreading Centre (MCSC). This profile shows the crustal structure across a transform fault system that juxtaposes Mesozoic-age continental crust to the south against the ∼10-Myr-old ultraslow spread oceanic crust to the north. Ocean-bottom seismographs were deployed along-profile, and inverse and forward traveltime modelling, supported by gravity analysis, reveals ∼23-km-thick continental crust that has been thinned over a distance of ∼70 km to ∼10 km-thick at the SITF, juxtaposed against ∼4-km-thick oceanic crust. This thinning is primarily accommodated within the lower crust. Since Moho reflections are not widely observed, the 7.0 km s−1 velocity contour is used to define the Moho along-profile. The apparent lack of reflections to the north of the SITF suggests that the Moho is more likely a transition zone between crust and mantle. Where the profile traverses bathymetric highs in the off-axis oceanic crust, higher P-wave velocity is observed at shallow crustal depths. S-wave arrival modelling also reveals elevated velocities at shallow depths, except for crust adjacent to the SITF that would have occupied the inside corner high of the ridge-transform intersection when on axis. We use a Vp/Vs ratio of 1.9 to mark where lithologies of the lower crust and uppermost mantle may be exhumed, and also to locate the upper-to-lower crustal transition, identify relict oceanic core complexes and regions of magmatically formed crust. An elevated Vp/Vs ratio suggests not only that serpentinized peridotite may be exposed at the seafloor in places, but also that seawater has been able to flow deep into the crust and upper mantle over 20–30-km-wide regions which may explain the lack of a distinct Moho. The SITF has higher velocities at shallower depths than observed in the oceanic crust to the north and, at the seabed, it is a relatively wide feature. However, the velocity–depth model subseabed suggests a fault zone no wider than ∼5–10 km, that is mirrored by a narrow seabed depression ∼7500 m deep. Gravity modelling shows that the SITF is also underlain, at &gt;2 km subseabed, by a ∼20-km-wide region of density &gt;3000 kg m−3 that may reflect a broad region of metamorphism. The residual mantle Bouguer anomaly across the survey region, when compared with the bathymetry, suggests that the transform may also have a component of left-lateral trans-tensional displacement that accounts for its apparently broad seabed appearance, and that the focus of magma supply may currently be displaced to the north of the MCSC segment centre. Our results suggest that Swan Islands margin development caused thinning of the adjacent continental crust, and that the adjacent oceanic crust formed in a cool ridge setting, either as a result of reduced mantle upwelling and/or due to fracture enhanced fluid flow.

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Haldar, C., P. Kumar, and M. Ravi Kumar. "Seismic structure of the lithosphere and upper mantle beneath the ocean islands near mid-oceanic ridges." Solid Earth 5, no. 1 (2014): 327–37. http://dx.doi.org/10.5194/se-5-327-2014.

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Abstract. Deciphering the seismic character of the young lithosphere near mid-oceanic ridges (MORs) is a challenging endeavor. In this study, we determine the seismic structure of the oceanic plate near the MORs using the P-to-S conversions isolated from quality data recorded at five broadband seismological stations situated on ocean islands in their vicinity. Estimates of the crustal and lithospheric thickness values from waveform inversion of the P-receiver function stacks at individual stations reveal that the Moho depth varies between ~ 10 ± 1 km and ~ 20 ± 1 km with the depths of the lithosphere–asthenosphere boundary (LAB) varying between ~ 40 ± 4 and ~ 65 ± 7 km. We found evidence for an additional low-velocity layer below the expected LAB depths at stations on Ascension, São Jorge and Easter islands. The layer probably relates to the presence of a hot spot corresponding to a magma chamber. Further, thinning of the upper mantle transition zone suggests a hotter mantle transition zone due to the possible presence of plumes in the mantle beneath the stations.

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Amukti, Rian, and Wiwit Suryanto. "Analisa Receiver Function Teleseismic untuk Mendeteksi Moho pada Stasiun Bkb Data Meramex." INDONESIAN JOURNAL OF APPLIED PHYSICS 3, no. 02 (2016): 195. http://dx.doi.org/10.13057/ijap.v3i02.1272.

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It has been done a research to determine internal earth using receiver function teleseismic analysis method. This method have been done by using MERAMEX (MErapi Amphibious Experiment) data from broadband seismometer BKB. Event of teleseismic is chosen from Honshu Japan with radius 30o and magnitude 7.2. This research begun by analysing radial and vertical characteristic of teleseismic event and using bandpass filter with range 0.003 Hz – 0.5 Hz. Then Iteractive Deconvolution is used to get velocity model. The result of this model shows crustal model that has 4 Km thick upper crust, a 26 Km thick lower crust and 10 Km thick Moho transition zone, with velocity increasing gradually.

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36

Zagrtdenov, Nail R., Georges Ceuleneer, Mathieu Rospabé, et al. "Anatomy of a chromitite dyke in the mantle/crust transition zone of the Oman ophiolite." Lithos 312-313 (July 2018): 343–57. http://dx.doi.org/10.1016/j.lithos.2018.05.012.

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ZHAGN, Pengfei, Meifu ZHOU, Benxun SU, et al. "Iron Isotopic Fractionation and Origin of Chromitites in the Paleo-Moho Transition Zone of the Kop Ophiolite, NE Turkey." Acta Geologica Sinica - English Edition 91, s1 (2017): 53. http://dx.doi.org/10.1111/1755-6724.13181.

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38

Zhang, Peng-Fei, Mei-Fu Zhou, Ben-Xun Su, et al. "Iron isotopic fractionation and origin of chromitites in the paleo-Moho transition zone of the Kop ophiolite, NE Turkey." Lithos 268-271 (January 2017): 65–75. http://dx.doi.org/10.1016/j.lithos.2016.10.019.

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39

Nurmukhamedov, A. G., and M. D. Sidorov. "THE DEEP STRUCTURE MODEL FOR SOUTHERN KAMCHATKA BASED ON 3D DENSITY MODELING AND GEOLOGICAL AND GEOPHYSICAL DATA." Tikhookeanskaya Geologiya 41, no. 2 (2022): 25–43. http://dx.doi.org/10.30911/0207-4028-2022-41-2-25-43.

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In the south of Kamchatka, a number of deep geophysical studies have been conducted along the profile lines. The aim of the research was to study the lithosphere in the zone of present-day volcanism and active seismicity. Geological and geophysical models of the Earth's crust and upper mantle were constructed along the profiles. The results were obtained as part of two-dimensional modeling of geophysical fields. But the analysis of materials shows that the territory is characterized by a complex geological structure, which is reflected in three-dimensional distribution of gravitating masses. For the first time, the article presents the results of volumetric density modeling covering the territory of southern Kamchatka, including areas covered by the Sea of Okhotsk and the Pacific Ocean. The model is based on the technology of three-dimensional imaging of 2D modeling results obtained along the grid of intersecting profiles. The 3D modeling generated isodensity surfaces that enclose regions with layers of high density (≥ 3.33 g/cm3). Thus, the surface identified beneath the ocean is interpreted as a fragment of the top of the subducting plate and the surface under the peninsula is identified as the top of the paleosubduction zone. A subhorizontal high-gradient zone (3.0–3.3 g/cm3) is recognized in the density structures that intersect the 3D model, which is identified with the Moho boundary. A model of subduction interaction between oceanic and continental lithospheric plates is proposed. The two-dimensional model shows the formation of a transitional layer between the Moho boundary of the overhanging lithospheric plate and the top of the paleosubduction zone. In the transition layer, a low-density zone is distinguished, where individual areas of maximum low-density are associated with melting chambers. Conditions are shown for the formation of the crust block with abundant basic-ultrabasic intrusions and the diorite-granodiorite intrusive massif. All ore occurrences and gold deposits of the Karymshinsky ore cluster are located within the contours of projection onto the ground surface of the deep high-gradient zone that encloses the low-density zone. Ore occurrences are genetically related to the zones of crustal weakness where epithermal deposits are formed in closed hydrothermal systems. Based on the analogy, it is possible to prognosticate gold occurrences in other areas of the projection of the high-gradient zone.

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40

Higgie, Katherine, and Andréa Tommasi. "Feedbacks between deformation and melt distribution in the crust–mantle transition zone of the Oman ophiolite." Earth and Planetary Science Letters 359-360 (December 2012): 61–72. http://dx.doi.org/10.1016/j.epsl.2012.10.003.

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41

Hassan, Soha, Mohamed Sultan, Mohamed Sobh, et al. "Crustal Structure of the Nile Delta: Interpretation of Seismic-Constrained Satellite-Based Gravity Data." Remote Sensing 13, no. 10 (2021): 1934. http://dx.doi.org/10.3390/rs13101934.

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Interpretations of the tectonic setting of the Nile Delta of Egypt and its offshore extension are challenged by the thick sedimentary cover that conceals the underlying structures and by the paucity of deep seismic data and boreholes. A crustal thickness model, constrained by available seismic and geological data, was constructed for the Nile Delta by inversion of satellite gravity data (GOCO06s), and a two-dimensional (2D) forward density model was generated along the Delta’s entire length. Modelling results reveal the following: (1) the Nile Delta is formed of two distinctive crustal units: the Southern Delta Block (SDB) and the Northern Delta Basin (NDB) separated by a hinge zone, a feature widely reported from passive margin settings; (2) the SDB is characterized by an east–west-trending low-gravity (~−40 mGal) anomaly indicative of continental crust characteristics (depth to Moho (DTM): 36–38 km); (3) the NDB and its offshore extension are characterized by high gravity anomalies (hinge zone: ~10 mGal; Delta shore line: >40 mGal; south Herodotus Basin: ~140 mGal) that are here attributed to crustal thinning and stretching and decrease in DTM, which is ~35 km at the hinge zone, 30–32 km at the shoreline, and 22–20 km south of the Herodotus Basin; and (4) an apparent continuation of the east-northeast–west-southwest transitional crust of the Nile Delta towards the north-northeast–south-southwest-trending Levant margin in the east. These observations together with the reported extensional tectonics along the hinge zone, NDB and its offshore, the low to moderate seismic activity, and the absence of volcanic eruptions in the Nile Delta are all consistent with the NDB being a non-volcanic passive margin transition zone between the North African continental crust (SDB) and the Mediterranean oceanic crust (Herodotus Basin), with the NDB representing a westward extension of the Levant margin extensional transition zone.

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Tsvetkova, T. O., I. V. Bugaenko, and L. M. Zaets. "Seismic tomography of the mantle and primary hydrogen deposits in the Dnieper-Donetsk basin." Geofizicheskiy Zhurnal 44, no. 3 (2022): 44–55. http://dx.doi.org/10.24028/gj.v44i3.261967.

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According to the three-dimensional P-velocity model of the mantle under Eurasia obtained by the Taylor approximation method, the analysis of the velocity structure of the mantle (to depths of 2500 km south of 50° N and 1700 km north) in the territory of the Dnieper-Donetsk depression was carried out in order to determine the possible areas of primary hydrogen release. Primary hydrogen is formed in the core and lower mantle, can be transferred to the surface (according to I.L. Gufeld). According to seismotomography, nine superdeep mantle fluids are isolated on the territory of Ukraine, the routes of which are defined as subvertical columns of alternation of high-speed and low-speed anomalies. In addition to the presence of superdeep mantle fluids in the study area, the following characteristics were analyzed: the depth of the main geodynamic boundary, the influence of the high-velocity transition zone of the upper mantle (propagating northward into the low-velocity transition zone of the upper mantle of the East European platform), the depth of the Moho boundary, gravity mantle anomalies and heat flow. The totality of the studies performed allowed us to conclude that, according to seismic tomography data, the Izyumsky and the eastern part of the Lokhvitsky segment of the Dnieper-Donetsk depression are promising areas for detecting primary hydrogen in the territory of the Dnieper-Donetsk depression.

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43

Abdullah, Saquib, Santanu Misra, and Biswajit Ghosh. "Melt-rock interaction and fractional crystallization in the Moho transition Zone: Evidence from the cretaceous Naga Hills Ophiolite, North-East India." Lithos 322 (December 2018): 197–211. http://dx.doi.org/10.1016/j.lithos.2018.10.012.

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Magalhães, José Ricardo, José Antonio Barbosa, Jefferson Tavares C. Oliveira, and Mário F. de Lima Filho. "CHARACTERIZATION OF THE OCEAN-CONTINENT TRANSITION IN THE PARAÍBA BASIN AND NATAL PLATFORM REGION, NE BRAZIL." Revista Brasileira de Geofísica 32, no. 3 (2014): 481. http://dx.doi.org/10.22564/rbgf.v32i3.504.

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ABSTRACT. Several studies have tried to address the evolution of the Atlantic conjugate margins, including Brazil and West Africa. However, past researchadvances has been hindered by a lack of data for the marginal region in the eastern portion of northeastern Brazil, extending from the Pernambuco Shear Zone tothe Touros High. This situation has imposed serious limitations on the development of a regional view of the paleotectonic and paleogeographic evolution of the marginin this area and on correlations with regional counterparts in Africa. Here, we present an investigation using regional seismic and potential field data. The results showthat this region represents a basement high forming a narrow platform with a thin sedimentary cover (0.8-2.5 km) and an abrupt shelf break, which created a large bypasszone towards the slope. The analysis of a deep seismic section revealed that thinned continental crust (transitional crust) occupies a narrow zone and that the continentaloceanicboundary (COB) is located approximately 100 km to the east of the present coastline. Geophysical modeling integrated with interpretation of the seismic datasuggests that this region is characterized by an abrupt thinning of continental crust, with an accompanying sudden rise of the Moho. There are also indications for theexistence of a zone of extremely thinned continental crust, which was interpreted as proto-oceanic crust. Our findings suggest that the study area shows strong similaritiesto non-volcanic rifted margins.Keywords: Paraíba and Natal Platform Basins, continental-oceanic transition, northeastern Brazilian continental margin, Atlantic rift. RESUMO. Vários trabalhos têm tentado abordar a evolução das margens conjugadas do Atlântico, incluindo o nordeste do Brasil e o oeste da África. Entretanto,o avanço de pesquisas anteriores tem sido dificultado em razão da falta de dados na região marginal da porção oriental do nordeste do Brasil, a área entre a Zonade Cisalhamento de Pernambuco e o Alto de Touros. Este fato tem imposto limitações ao desenvolvimento de modelos regionais sobre a evolução paleotectônica e paleogeográfica desta região, assim como na correlação com sua contraparte na África. Aqui é apresentada uma investigação realizada com base em dados sísmicos e de métodos potenciais regionais. Os resultados mostraram que esta região representa um alto do embasamento que forma uma plataforma estreita com uma coberturasedimentar pouco espessa (0,8-2,5 km) e uma quebra abrupta da plataforma, o que criou uma grande zona de by pass através do talude. A análise de uma seçao sísmica profunda revelou que a crosta continental afinada (crosta transicional) representa uma estreita zona, e que o limite crosta continental-oceânica (COB) está localizadoa aproximadamente 100 km a leste da atual linha de costa. A modelagem geofísica, integrada com a interpretação sísmica, indica que esta região é caracterizada porum afinamento abrupto da crosta continental, com a consequente ascensão súbita da Moho. Também há evidências da existência de uma zona de crosta continental extremamente afinada, a qual foi interpretada como crosta proto-oceânica. Estes novos dados demonstram que esta área apresenta fortes similaridades com margens rifteadas não vulcânicas.Palavras-chave: bacias da Paraíba e da Plataforma de Natal, transição crosta continental-oceânica, margem continental do nordeste Brasileiro, rifte Atlântico.

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45

Koga, Kenneth T., Peter B. Kelemen, and Nobumichi Shimizu. "Petrogenesis of the crust-mantle transition zone and the origin of lower crustal wehrlite in the Oman ophiolite." Geochemistry, Geophysics, Geosystems 2, no. 9 (2001): n/a. http://dx.doi.org/10.1029/2000gc000132.

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Dannowski, Anke, Heidrun Kopp, Ingo Grevemeyer, et al. "Seismic evidence for failed rifting in the Ligurian Basin, Western Alpine domain." Solid Earth 11, no. 3 (2020): 873–87. http://dx.doi.org/10.5194/se-11-873-2020.

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Abstract. The Ligurian Basin is located in the Mediterranean Sea to the north-west of Corsica at the transition from the Western Alpine orogen to the Apennine system and was generated by the south-eastward trench retreat of the Apennines–Calabrian subduction zone. Late-Oligocene-to-Miocene rifting caused continental extension and subsidence, leading to the opening of the basin. Yet it remains unclear if rifting caused continental break-up and seafloor spreading. To reveal its lithospheric architecture, we acquired a 130 km long seismic refraction and wide-angle reflection profile in the Ligurian Basin. The seismic line was recorded in the framework of SPP2017 4D-MB, a Priority Programme of the German Research Foundation (DFG) and the German component of the European AlpArray initiative, and trends in a NE–SW direction at the centre of the Ligurian Basin, roughly parallel to the French coastline. The seismic data were recorded on the newly developed GEOLOG recorder, designed at GEOMAR, and are dominated by sedimentary refractions and show mantle Pn arrivals at offsets of up to 70 km and a very prominent wide-angle Mohorovičić discontinuity (Moho) reflection. The main features share several characteristics (e.g. offset range, continuity) generally associated with continental settings rather than documenting oceanic crust emplaced by seafloor spreading. Seismic tomography results are complemented by gravity data and yield a ∼ 6–8 km thick sedimentary cover and the seismic Moho at 11–13 km depth below the sea surface. Our study reveals that the oceanic domain does not extend as far north as previously assumed. Whether Oligocene–Miocene extension led to extremely thinned continental crust or exhumed subcontinental mantle remains unclear. A low grade of mantle serpentinisation indicates a high rate of syn-rift sedimentation. However, rifting failed before oceanic spreading was initiated, and continental crust thickens towards the NE within the northern Ligurian Basin.

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Sano, S., and J. I. Kimura. "Clinopyroxene REE Geochemistry of the Red Hills Peridotite, New Zealand: Interpretation of Magmatic Processes in the Upper Mantle and in the Moho Transition Zone." Journal of Petrology 48, no. 1 (2006): 113–39. http://dx.doi.org/10.1093/petrology/egl056.

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48

Hutchinson, D. R., M. W. Lee, John Behrendt, W. F. Cannon, and A. G. Green. "Variations in the reflectivity of the moho transition zone beneath the Midcontinent Rift System of North America: Results from true amplitude analysis of GLIMPCE data." Journal of Geophysical Research 97, B4 (1992): 4721. http://dx.doi.org/10.1029/91jb02572.

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49

Gahlan, Hisham A., Shoji Arai, Fawzy F. Abu El-Ela, and Akihiro Tamura. "Origin of wehrlite cumulates in the Moho transition zone of the Neoproterozoic Ras Salatit ophiolite, Central Eastern Desert, Egypt: crustal wehrlites with typical mantle characteristics." Contributions to Mineralogy and Petrology 163, no. 2 (2011): 225–41. http://dx.doi.org/10.1007/s00410-011-0669-5.

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Mackie, D. J., R. M. Clowes, S. A. Dehler, R. M. Ellis, and P. Morel-À-l'Huissier. "The Queen Charlotte Islands refraction project. Part II. Structural model for transition from Pacific plate to North American plate." Canadian Journal of Earth Sciences 26, no. 9 (1989): 1713–25. http://dx.doi.org/10.1139/e89-146.

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The oceanic-continental boundary west of the Queen Charlotte Islands is marked by the active Queen Charlotte Fault Zone. Motion along the fault is predominantly dextral strike slip, but relative plate motion and other studies indicate that a component of convergence between the oceanic Pacific plate and the continental North American plate presently exists. This convergence could be manifest through different types of deformation: oblique subduction, crustal thickening, or lateral distortion of the plates. In 1983, a 330 km offshore–onshore seismic refraction profile extending from the deep ocean across the islands to the mainland of British Columbia was recorded to investigate (i) structure of the fault zone and associated oceanic–continental boundary and (ii) lithospheric structure beneath the islands and Hecate Strait to define the regional transition from Pacific plate to North American plate and thus the nature of the convergence. Two-dimensional ray tracing and synthetic seismogram modelling of many record sections enabled the derivation of a composite velocity structural section along the profile. The structural section also was tested with two-dimensional gravity modelling. Part I of the study addressed the structure of the fault zone; part II addresses lithospheric structure extending eastward to the mainland.The derived velocity structure has some important and well-constrained features: (i) anomalously low crustal velocities (5.3 km/s with a 0.2 km/s per km gradient) underlain by a steep, 19 °eastward-dipping boundary above the mantle in the terrace region west of the main fault; (ii) a thin crust of 21–27 km beneath the Queen Charlotte Islands; and (iii) a gentle 4 °eastward dip of the Moho below Hecate Strait as crustal thickness increases from 27 km to 32 km. The gravity modelling requires that mantle material extend upwards to a depth of about 30 km below the mainland and indicates that an underlying subducted slab, if it exists, extends eastward no farther than the mainland.Unfortunately, the velocity structure delineated by this study could not unambiguously determine the mode of deformation, because the lowermost crustal block beneath Queen Charlotte Islands and Hecate Strait can be interpreted as subducted oceanic crust or middle to lower continental crust. Thus, two different tectonic models for the transition from Pacific plate to North American plate are discussed: in one, oblique subduction is the principal characteristic; in the other, oceanic lithosphere juxtaposed against continental lithosphere across a narrow boundary zone along which only transcurrent motion occurs is the dominant feature. Based on the thin crust beneath the Queen Charlotte Islands, the lack of a wide zone of deformation along the plate boundary region, and other geological and geophysical characteristics, oblique subduction is the more plausible model.

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Journal articles on the topic 'Oman Moho Transition Zone'

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