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Geological map of the UAE (modified after British Geological Survey maps), showing the location of the Sheikh Khalifa Bin Zayed road and reference locations to subsequent figures. For comparison, we have kept the British Geological Survey subdivision of the gabbros. MTZ = Moho transition zone; UAE = United Arab Emirates.
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The Oman‐United Arab Emirates (UAE) ophiolite is the most intensely studied ophiolite on Earth, is commonly used as a template for other poorly exposed and structurally complex ophiolites, and is often used as an analog for fast‐spreading mid‐ocean ridges like the East Pacific Rise. Several recent studies, including the largest ever focused on the...
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The Oman ophiolite (Samail massif, Sultanate of Oman) is the largest sub-aerial exposure of oceanic lithosphere on Earth and provides the opportunity to study the accretion and alteration of oceanic lithosphere formed under fast-spreading conditions. Drill hole GT3A (23∘06′50.7′′ N, 58∘12′42.2′′ E) of the ICDP (International Continental Scientific...
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... The structure of the Semail ophiolite and its tectonic evolution have been subject of geoscientific investigations for decades (e.g., Glennie, 1974;Searle & Malpas, 1980). Geological studies (e.g., Ambrose & Searle, 2019;Duretz et al., 2016;Guilmette et al., 2018;Hacker et al., 1996;Nicolas et al., 1994Nicolas et al., , 2000Porkoláb et al., 2021;Rioux et al., 2016;Searle & Cox, 1999) have provided insights into the chronological phases and the geological context underlying the formation of oceanic lithosphere, the dynamics of obduction, and the orogenic development in northern Oman. Previous studies provided a comprehensive understanding of tectonic evolution of the continental crust. ...
To gain a deeper understanding of the extensive and varied lithospheric deformations beneath northern Oman, we examine seismic anisotropy in this region using splitting analysis of teleseismic shear wave data. Our study utilizes data from a dense network consisting of 13 permanent and 45 temporary seismic stations, which were operational for approximately 2.5 years starting from October 2013. By examining the azimuthal distribution of shear wave splitting (SWS) parameters, we were able to divide the study area into three sub‐regions. The stations located to the west of the Hawasina window exhibit relatively azimuthally invariant SWS parameters suggesting a single anisotropic layer. On the other hand, most of the stations located in the central and eastern regions display variations versus back‐azimuth, indicating the potential presence of depth‐dependent anisotropy. The General NW‐SE trend of the Fast Polarization Directions (FPDs) of the one‐layer anisotropy in the west and FPDs of the upper layers in the east is concordant with the strike of the structures resulting from the collision between the continental and oceanic plates. A clear contrast in SWS parameters is observed in the Semail Gap Fault Zone (SGFZ), suggesting that the SGFZ can be a lithospheric‐scale structure that hampers the intrusion of mafic magma from the southeast. Furthermore, the FPDs of the lower layer in the east exhibit an NE‐SW trend, which may be indicative of the large‐scale mantle flow resulting from the present‐day plate motion.
... Extensive geological and geophysical studies have been carried out in eastern Arabia, including the Oman-United Arab Emirates (UAE) mountain belt and adjacent basins, with the aim of determining the physical properties of the crust and upper mantle in a region that has experienced ophiolite obduction (Glennie et al., 1973;Searle and Cox, 1999;Cooper, 1988;Searle, 2007;Ali and Watts, 2009;Goodenough et al., 2010;Searle et al., 2014;Searle et al., 2015;Ambrose and Searle, 2019;Ali et al., 2018;Pilia et al., 2021a;Pilia et al., 2021b;Lippard et al., 1986;Searle and Ali, 2009;Geng et al., 2022;Weidle et al., 2022;Ismaiel et al., 2023;Ali et al., 2020). Despite the likely control of the long-term strength of the lithosphere on geological processes such as orogeny, rifting, and sedimentary basin development, the mechanical strength of the lithosphere of the Oman-UAE mountain belt and surrounding areas remains poorly explored. ...
PDF link: https://authors.elsevier.com/c/1hXTO98we1puv
The continental lithosphere of the Arabian Plate has evolved through a long and complex tectonic history and comprises major geological features such as an ophiolite complex, Cenozoic basalt extrusion, and Proterozoic basement outcrops. In eastern Arabia, an NW-SE to N-S oriented orogenic belt is present in Oman and the United Arab Emirates (UAE). The mountain belt formed due to the Late Cretaceous obduction of the Semail ophiolite, where a thick slab of oceanic crust and upper mantle was emplaced on the rifted Arabian continental margin. However, the mechanical strength of the lithosphere over the entire region is poorly known. In this study, we employ Bouguer gravity anomaly and topographic data, along with data on crustal properties obtained from teleseismic analyses, to assess the spatial variations in the effective elastic thickness (Te) of the eastern Arabian Plate. The joint inversion of coherence and admittance yielded Te values ranging from 10 to 50 km and an initial subsurface-to-surface load ratio (F) of 0.1 to 0.8. Te values in the southern part of eastern Arabia are low (< 20 km), while the northeastern regions of Saudi Arabia, the UAE, and Qatar exhibit intermediate to high Te values ranging from 30 to 45 km. The Oman-UAE mountain belt is associated with an intermediate Te of 30 km in the northern segment and a low Te of 20 km in the southern segment. The reduction in Te observed along the strike of the mountain belt suggests weakening of the lithosphere during the obduction of the Semail ophiolite. Te correlates well with both the seismic thickness of the lithosphere (Ts) and the decrease in shear-wave velocity at a depth of 150 km. The seismogenic thickness in eastern Arabia, however, is about 15 km, which is significantly less than Te and shows that both the crust and upper mantle contribute to the strength of the continental lithosphere. The Ts/Te ratio ranges from 1 to 9, with a maximum peak at 3–5, which is similar to the results observed for the oceanic lithosphere.
... Extensive geological and geophysical studies have been carried out in eastern Arabia, including the Oman-United Arab Emirates (UAE) mountain belt and adjacent basins, with the aim of determining the physical properties of the crust and upper mantle in a region that has experienced ophiolite obduction (Glennie et al., 1973;Searle and Cox, 1999;Cooper, 1988;Searle, 2007;Ali and Watts, 2009;Goodenough et al., 2010;Searle et al., 2014;Searle et al., 2015;Ambrose and Searle, 2019;Ali et al., 2018;Pilia et al., 2021a;Pilia et al., 2021b;Lippard et al., 1986;Searle and Ali, 2009;Geng et al., 2022;Weidle et al., 2022;Ismaiel et al., 2023;Ali et al., 2020). Despite the likely control of the long-term strength of the lithosphere on geological processes such as orogeny, rifting, and sedimentary basin development, the mechanical strength of the lithosphere of the Oman-UAE mountain belt and surrounding areas remains poorly explored. ...
The study of gravity signatures corresponding to sediment load over the passive margins is helpful to constrain the mechanical properties of continental rift systems as well as the adjacent ocean basins. Seismic reflection, free-air gravity and well information from the East India Passive Margin (EIPM) are investigated through spectral approach and 2D process-oriented gravity modelling for quantifying effective elastic plate thickness (Te) to understand the rift mechanisms and the sedimentary basins evolution. The characteristics of lithosphere within the major structural domains along the margin are quite variable. A narrow necking zone (40 km) in the southern segment, and approximately a 70 km hyper-thinned and exhumed domains are inferred in the central segment, while a narrow hyper-thinned domain (30-35 km) is observed in the northern segment of the margin. The southern segment of EIPM, adjacent to Southern Granulite Terrain has low Te values ranging from 5-10 km.
The segment in the central margin, offshore Dharwar Craton has moderate Tevalues of 15-20 km. And the northern segment adjacent to onshore Eastern Ghats Mobile Belt has relatively high mechanical strength with Te values ranging from 25-35 km. The
pattern of Te values and extent of major structural domains along the margin indicates that the southern, central and northern segments evolved as three different modes of rifting such as transform, hyperextended and hypoextended, respectively. In the
oceanic domain, the lithospheric strength broadly increases with age following the thermal induced cooling plate model (600°C isotherm). The thick sedimentary basin of the Bay of Bengal had attained the high value of elastic thickness (Te > 45 km) in the
last 23 Myrs. The significant rheological strengthening of the oceanic lithosphere may be attribute to the following reasons: 1) increase in shear-wave velocity anomaly at a depth of 150 km and upper mantle density, 2) change in plate curvature caused by
excessive deposition of Bengal Fan sediments in the deep ocean basins and subduction of oceanic plate under the Eurasian plate near the Bengal Fan and 3) modification of stress state of the lithosphere as a convergent interaction of the Indian plate with SE Asia.
... Since the 1970s, several comprehensive geological studies have provided details of the tectonic evolution of the Semail Ophiolite in the UAE and Oman (Glennie et al., 1974;Coleman, 1981;Lippard et al., 1982;Lippard et al., 1986;Searle et al., 1983;Searle, 1988;Searle and Cox, 1999;Goodenough et al., 2010;Searle et al., 2014;Ambrose and Searle, 2019). The Semail Ophiolite is one of the largest and best-preserved Phanerozoic ophiolites and is, therefore, a valuable example to assist the understanding of other more disrupted ophiolites of similar age. ...
... The Semail Ophiolite is one of the largest and best-preserved Phanerozoic ophiolites and is, therefore, a valuable example to assist the understanding of other more disrupted ophiolites of similar age. Furthermore, the exposed deep sections through the Semail yield many insights into the processes operating in the present-day oceanic lithosphere (Ambrose and Searle, 2019). ...
... The generalized geology of the Northern Emirates has been presented in detail by a range of previous studies (Lippard et al., 1982;Searle et al., 1983;Searle, 1988;Searle and Cox, 1999;Styles et al., 2006;Farrant et al., 2012;Searle et al., 2014;Callot et al., 2017;Ambrose and Searle, 2019). The Semail ophiolite of the Hajar mountains in the UAE is part of the 700 km long and 50-150 km wide thrust sheet of former Tethyan oceanic lithosphere emplaced onto the previously rifted Arabian margin during the Late Cretaceous (Glennie et al., 1973(Glennie et al., , 1974Coleman, 1981;Searle and Cox, 1999;Searle et al., 2014;Ali et al., 2020;Searle et al., 2022). ...
Recent geophysical studies are focused on imaging the present-day architecture of the subsurface structures in the northern United Arab Emirates. Previous geophysical data have not fully investigated the deep structures in the middle and lower crust. The foreland basin flanking the UAE-Oman mountains to its west has been investigated by oil companies, mainly using seismic techniques. These studies have been vital in providing a constraint on the subsurface structure of the northern Emirates. This paper reports the results of using broad-band magnetotelluric (BBMT) data acquired for the first time in the UAE to map deep electrical crustal structures. The study aims at determining the geometry of the Semail Ophiolite, the underlying thrust sheets, and the basement structure beneath the allochthonous units and the foreland basin. The MT data were collected from 15 stations along an E-W profile across the Semail Ophiolite and the Dibba zone in the east and the foreland basin in the west. The MT data achieve greater crustal penetration, revealing electrical structures within the upper, mid, and lower crust. 2D and 3D inversion of the data map the high resistivity Ophiolite structure and the associated conductive Hwasina-Haybi thrust sheets in the mountain ranges and in the Dibba zone. In the foreland basin, the Quaternary and Tertiary sediments in the Pabdeh basin are characterized by low resistivity. Furthermore, the MT models detect a high resistivity zone related to the basement structure of the northern UAE in the middle and lower crust. The Ophiolite near the Dibba zone has >7 km thickness as shown in the 2D MT model, and the Hawasina-Haybi sheets have a maximum thickness of ⁓10 km beneath the Ophiolite. The allochthonous units indicate an oceanward dipping as similarly reported in the previous geophysical and geologic studies.
... The Semail (Oman) ophiolite is the largest-exposed obducted thrust sheet of oceanic crust and upper mantle emplaced onto a continental margin on Earth (Reinhardt, 1969;Glennie et al., 1973Glennie et al., , 1974Coleman and Hopson, 1981;Lippard et al., 1986;Searle and Cox, 1999;Searle, 2007Searle, , 2019; Ambrose and Searle, 2019). It is exposed along the length of the northern Oman -United Arab Emirates (UAE) mountains, which are more than 700 km in length and up to 150 km wide (Fig. 1). ...
The Semail Thrust in the Oman-UAE mountains is mapped along the base of the Semail Ophiolite, a 10–15 km thick sequence of Cenomanian oceanic crust and upper mantle emplaced from NE to SW onto the previously passive, Mid-Permian to Cenomanian continental margin of Oman. The juxtaposition of the Semail ophiolite with a range of different rock types sourced from different depths suggest a complex tectonic history for this major fault and shear zone. Here we summarize previous work and present an overview of the tectonic history of the fault. The Semail Thrust is mapped along the base of the ophiolite as a single line on the geological map, yet it covers a variety of structural features spanning depths of 40–45 km to the surface, and a time scale from ∼96 Ma (or earlier) to Eocene time. The structural evolution of the Semail Thrust includes (a) the roof fault or ductile shear zone of an exhumed oceanic subduction zone (granulites, amphibolites and greenschists of the metamorphic sole), (b) a deep mantle ductile shear zone (Banded Ultramafic Unit), (c) a brittle fault above a foreland-directed fold-thrust belt, (d) an out-of-sequence brittle fault exhuming a higher ophiolite thrust sheet above deeper level lower crust granulites (e.g. Bani Hamid, UAE), (e) a late out-of-sequence thrust truncating underlying structural units (e.g. Hawasina Window), (f) a passive roof fault beneath exhuming HP rocks (e.g. ‘Semail Thrust’ below the Muscat peridotite, above the Ruwi mélange and high-pressure rocks of northern Saih Hatat), and (g) a reactivated normal fault bounding rising footwall culminations, notably of the Jebel Akhdar, Jebel Nakhl, and Saih Hatat anticlines. Different stages in the evolution of the Semail Thrust can be mapped out and interpreted from different regions along the Oman Mountains.
... During the Tethys Ocean closure in the Late Cretaceous, convergent tectonics resulted in the emplacement of the Samail Ophiolite and related deep-sea sediments of the Hawasina Complex over the Hajar Supergroups (Coleman, 1981;Glennie et al., 1974;Jacobs et al., 2015;Robertson et al., 1990). The Samail Ophiolite exposures are close to the study area located on the Batina Coast along the eastern flank of the Oman Mountains (i.e., within a distance of a few kilometers; Figure 1a) and consist of serpentinite, harzburgite, dunite, layered gabbro, sheeted dykes, and pillow lava (Ambrose & Searle, 2019;Boudier & Coleman, 1981;Boudier & Nicolas, 1995;Boudier et al., 1996;Braun & Kelemen, 2002;Christensen & Smewing, 1981;Godard et al., 2000;Hanghøj et al., 2010;Lippard et al., 1986;Manghnani & Coleman, 1981;Monnier et al., 2006;Nicolas et al., 2000). Post-obduction Campanian to Maastrichtian Aruma Group, Paleocene-Eocene Hadhramaut Group, Oligocene MAM reefs, and Neogene Fars Group sedimentary successions accumulated in the Batina Coast region including the study area Mann et al., 1990;Nolan et al., 1990;Salad Hersi & Al-Harthy, 2010). ...
Carbonate precipitation through atmospheric CO2 uptake by alkaline-hyperalkaline
waters offers a potential approach to mitigating anthropogenic CO2 emissions. The Oman Ophiolite produces high-pH water characterized by continuous sequestration of CO2 at the air-water interface. The geochemical and isotopic data of carbonates from the Barzaman Formation is used to assess the amount of atmospheric CO2 stored in the dolomite-calcite assemblage. Post Archean Australian Shale -normalized rare earth elements patterns, with the exception of La and Ce anomalies, are similar to
those of the bulk oceanic and lower crusts, with increasing LREE and flat HREE trends, and a positive Eu anomaly. The δ13CVPDB and δ18OVSMOW isotope values of the analyzed samples show two distinct endmembers, in which dolomite (−7.77‰ and +27.3‰) is isotopically heavier than calcite (−9.93‰ and +21.5‰). The estimated carbonate growth temperatures (18°C–56°C) are indistinguishable from the previously reported range (18°C–66°C). The C-O isotope model for calcite, groundwater, and atmospheric CO2 shows that an ophiolite-derived calcite sample absorbed an unequivocal amount of atmospheric CO2 (78% ± 11%) during precipitation. At the same time, dissolved inorganic carbon (DIC) in water accounts for the remaining carbon contribution (22% ± 9%). DIC is closely associated with different carbonate lithofacies and ophiolite-derived soil, exhibiting large variations in C-O isotopic compositions caused by isotopic disequilibrium. Taken together, geochemical and isotopic properties confirm that the carbonates were formed under oxic conditions triggered by the water-rock interaction. For a reliable estimate of CO2 sequestered by carbonates of the Barzaman Formation, a systematic groundwater analysis is recommended to determine the contribution of CO2 in DIC.
... During the Tethys Ocean closure in the Late Cretaceous, convergent tectonics resulted in the emplacement of the Samail Ophiolite and related deep-sea sediments of the Hawasina Complex over the Hajar Supergroups (Coleman, 1981;Glennie et al., 1974;Jacobs et al., 2015;Robertson et al., 1990). The Samail Ophiolite exposures are close to the study area located on the Batina Coast along the eastern flank of the Oman Mountains (i.e., within a distance of a few kilometers; Figure 1a) and consist of serpentinite, harzburgite, dunite, layered gabbro, sheeted dykes, and pillow lava (Ambrose & Searle, 2019;Boudier & Coleman, 1981;Boudier & Nicolas, 1995;Boudier et al., 1996;Braun & Kelemen, 2002;Christensen & Smewing, 1981;Godard et al., 2000;Hanghøj et al., 2010;Lippard et al., 1986;Manghnani & Coleman, 1981;Monnier et al., 2006;Nicolas et al., 2000). Post-obduction Campanian to Maastrichtian Aruma Group, Paleocene-Eocene Hadhramaut Group, Oligocene MAM reefs, and Neogene Fars Group sedimentary successions accumulated in the Batina Coast region including the study area Mann et al., 1990;Nolan et al., 1990;Salad Hersi & Al-Harthy, 2010). ...
Carbonate precipitation through atmospheric CO2 uptake by alkaline‐hyperalkaline waters offers a potential approach to mitigating anthropogenic CO2 emissions. The Oman Ophiolite produces high‐pH water characterized by continuous sequestration of CO2 at the air‐water interface. The geochemical and isotopic data of carbonates from the Barzaman Formation is used to assess the amount of atmospheric CO2 stored in the dolomite‐calcite assemblage. Post Archean Australian Shale ‐normalized rare earth elements patterns, with the exception of La and Ce anomalies, are similar to those of the bulk oceanic and lower crusts, with increasing LREE and flat HREE trends, and a positive Eu anomaly. The δ¹³CVPDB and δ¹⁸OVSMOW isotope values of the analyzed samples show two distinct end‐members, in which dolomite (−7.77‰ and +27.3‰) is isotopically heavier than calcite (−9.93‰ and +21.5‰). The estimated carbonate growth temperatures (18°C–56°C) are indistinguishable from the previously reported range (18°C–66°C). The C‐O isotope model for calcite, groundwater, and atmospheric CO2 shows that an ophiolite‐derived calcite sample absorbed an unequivocal amount of atmospheric CO2 (78% ± 11%) during precipitation. At the same time, dissolved inorganic carbon (DIC) in water accounts for the remaining carbon contribution (22% ± 9%). DIC is closely associated with different carbonate lithofacies and ophiolite‐derived soil, exhibiting large variations in C‐O isotopic compositions caused by isotopic disequilibrium. Taken together, geochemical and isotopic properties confirm that the carbonates were formed under oxic conditions triggered by the water‐rock interaction. For a reliable estimate of CO2 sequestered by carbonates of the Barzaman Formation, a systematic groundwater analysis is recommended to determine the contribution of CO2 in DIC.
... The volume of V2 magmatism varies along the length of the ophiolite, with V2 volcanic and plutonic being rare in the southern ophiolite massifs and becoming increasingly more abundant to the north (Goodenough et al., 2010;Haase et al., 2016;Styles, Ellison, et al., 2006). Goodenough et al. (2010) argued that up to 50% of the crust in the UAE portion of the ophiolite is composed of V2 magmatism; however, detailed mapping and structural analyses by Ambrose and Searle (2019) suggest apparent differences between Oman and UAE may simply reflect the level of exposure. The final V3 volcanic series, which is enriched in LREE, is separated from the V2 lavas by a ∼15 m thick pelagic sedimentary sequence and significantly post-dates ophiolite magmatism, potentially reflecting obduction of the ophiolite onto the continental margin (Alabaster et al., 1982;Ernewein et al., 1988). ...
... These facies are interpreted to be equivalent to the V2 plutonic rocks in the Oman portion of the ophiolite. As discussed above, the late plutonic series comprises up to 50% of the exposed section in the UAE (Goodenough et al., 2010;Styles, Ellison, et al., 2006); however, this may reflect the level of exposure, rather than a higher proportion of V2 magmatism in this area (Ambrose & Searle, 2019). The dated rocks include a sample of the Fujairah gabbro (131213M04), a sample from a km-scale tonalite intrusion associated with the Fujairah gabbro (131211M03), and two samples of tonalites from mixed mafic and felsic intrusions with "vinaigrette" textures (131211M04, 131213M06; Figure 2b; Goodenough et al., 2010;Styles, Ellison, et al., 2006). ...
Understanding the tectonic setting in which ophiolites form is necessary to determine how they can be used to study ocean spreading and subduction zone processes. Here, we present high‐precision U‐Pb zircon dates and Sm‐Nd isotopic data from two late magmatic series in the Samail ophiolite in Oman and the United Arab Emirates (UAE), which constrain its tectonic development. Volcanic rocks in the ophiolite record a progression from MORB‐like V1 lavas to subduction‐related V2 lavas. Plutonic rocks related to V2 magmatism yielded ²⁰⁶Pb/²³⁸U dates of 95.557 ± 0.063–95.289 ± 0.067 Ma. A second late magmatic series consists of felsic dikes and sills that intermittently intrude the upper mantle and are attributed to melting of a subducting slab. These dikes in Oman range from 95.201 ± 0.032 to 94.95 ± 0.10 Ma, with εNd(t) = −5.05 to −1.63. A single dike, attributed to V2 magmatism, has a higher εNd(t) = 7.35 and a date of 95.478 ± 0.032 Ma. Similar intrusions in the UAE are younger, ranging from 94.119 ± 0.057 to 90.998 ± 0.052 Ma. Our new and existing data indicate the following timeline of ophiolite formation during subduction initiation: (1) Initial sole metamorphism at ≥96.2 Ma; (2) Formation of the crust through primarily decompression‐related V1 magmatism from 96.1 to 95.6 Ma; (3) V2 magmatism related to H2O‐fluxed mantle melting from 95.6 to 95.2 Ma; and (4) Intrusion of slab‐derived felsic dikes from 95.2 to 95.0 Ma. The temporal progression of magmatism is similar to the timescales of subduction initiation predicted by geodynamic models and observed in the Izu‐Bonin‐Mariana forearc.
... The 5-6 km s −1 velocity range is typical of sheeted dikes or upper gabbros from ophiolites in the Troodos, Papua New Guinea, and Newfoundland . We note that the uppermost section of the oceanic crust (pillow lavas) is not observed anywhere in the UAE, although it is present in Oman (Ambrose & Searle, 2019). Seismic reflection data (Figure 2), with the aid of several wells, allow us to image the stratigraphy of the broad depositional sedimentary basin underlying the Gulf of Oman. ...
The Semail ophiolite, a thick thrust sheet of Late Cretaceous oceanic crust and upper mantle, was obducted onto the previously rifted Arabian continental margin in the Late Cretaceous, and now forms part of the United Arab Emirates (UAE)‐Oman mountain belt. A deep foreland basin along the west and SW margin of the mountains developed during the obduction process, as a result of flexure due to loading of the ophiolite and underlying thrust sheets. The nature of the crust beneath the deep sedimentary basins that flank the mountain belt, and the extent to which the Arabian continental crust has thickened due to the obduction process are outstanding questions. We use a combination of active‐ and passive‐source seismic data to constrain the stratigraphy, velocity structure and crustal thickness beneath the UAE‐Oman mountains and its bounding basins. Depth‐migrated multichannel seismic reflection profile data are integrated in the modeling of traveltimes from long offset reflections and refractions, which are used to resolve the crustal thickness and velocity structure along two E‐W onshore/offshore transects in the UAE. Additionally, we apply the virtual deep seismic sounding method to distant earthquake data recorded along the two transects to image crustal thickness variations. Active seismic methods define the Semail ophiolite as a high‐velocity body dipping to the east at 40°–45°. The new crustal thickness model presented in this work provides evidence that a crustal root is present beneath the Semail ophiolite, suggesting that folding and thrusting during the obduction process may have thickened the pre‐existing crust by 16 km.
... The Semail ophiolite sequence is a regular Penrose-type ophiolite with a harzburgite-dunite mantle sequence, with a 1-2 km thick Moho transition zone comprising interbanded harzburgites, dunites and wehrlites with overlying gabbro sill complexes intruded by tonalite-trondhjemite dykes, and an upper crust comprising sheeted dykes and extrusive basalts [20][21][22] . From structurally lowest to highest position, the allochthonous sheets, Fig. 1 Location map showing the transects along which geological and geophysical data were acquired. ...
The Oman-United Arab Emirates ophiolite has been used extensively to document the geological processes that form oceanic crust. The geometry of the ophiolite, its extension into the Gulf of Oman, and the nature of the crust that underlies it are, however, unknown. Here, we show the ophiolite forms a high velocity, high density, >15 km thick east-dipping body that during emplacement flexed down a previously rifted continental margin thereby contributing to subsidence of flanking sedimentary basins. The western limit of the ophiolite is defined onshore by the Semail thrust while the eastern limit extends several km offshore, where it is defined seismically by a ~40–45°, east-dipping, normal fault. The fault is interpreted as the southwestern margin of an incipient suture zone that separates the Arabian plate from in situ Gulf of Oman oceanic crust and mantle presently subducting northwards beneath the Eurasian plate along the Makran trench. The Semail ophiolite provides evidence for geological processes that form oceanic crust, however, its deep structure remains debated. Here, the authors use geophysical imaging to determine that the ophiolite is bound by a thrust fault in the west, and a normal fault in the east, bounding a rapidly subsiding basin, implying the ophiolite may not be rooted in the Gulf of Oman crust.
