Crustal Domains Research Articles

Role of rift maturity on the architecture and shortening distribution in mountain belts

Many relics of passive margin are found in mountain belts sometimes together with pristine exhume mantle. The reasons why these structures are preserved from tectonic reworking and whether the piece of mantle that accompanies them is exhumed during extension or collision remains a question. Using thermo-mechanical modelling we find on the one hand that, the strain distribution in the orogenic wedge is controlled by the original position of crustal domains across the rifted margin. In the upper plate, the structural relationships acquired during the rifting phase between the upper mantle and surrounding units are never reactivated during compression due to crustal strain localization. Mantle exhumation on the other hand can occur either during the collision or rifting phase depending on the thermal regime at the onset of the inversion. Applying these general rules to the Pyrenees, we show that exhumed mantle domain in the former passive margin could not exceed a width of 50 km to 70 km; otherwise obduction would have occurred due to the high thermal regime at the onset of the inversion.

Active-couple indentation in geodynamics of NNW Iran: Evidence from synchronous left- and right-lateral co-linear seismogenic faults in western Alborz and Iranian Azerbaijan domains

Situated within the central portion of the Arabia-Eurasia collision zone, NNW Iran exhibits an interesting active tectonic context characterized by synchronous left- and right-lateral co-linear seismogenic faults along the adjacent WNW-striking West-Central Alborz (e.g. the Rudbar earthquake fault) and Iranian Azerbaijan (e.g. the North Tabriz seismogenic fault). These structural domains are deforming as a single deformable geomechanical territory between the nearly rigid Central Iran and South Caspian domains to the SSW and NNE, respectively. In this paper, we analyze tectonic interactions of these active structural domains and their influence on the geodynamics of NNW Iran based on morphotectonic and seismological investigations. Indentation tectonics is suggested to play an important role in the geodynamics of this territory. At a plate tectonic scale, the rigid Arabian plate acts as the main indenter which bulldozes the less rigid crustal domains ahead into folded belts (within Zagros and Caucasus to the north) and pushes other blocks aside. In this deformation system, the South Caspian domain acts as a backstop against southern and western deformation zones. The structural domains of Alborz (to the east) and Iranian Azerbaijan Caucasus (to the west) are separated by the NNW-striking Astara-Talesh dextral transpressional zone. Analysis of morphotectonic features and focal mechanisms conducted in this central portion of NNW Iran confirms dextral faulting localized along the NNW-striking deformation zone, which is in agreement with the observed reverse earthquake faulting on west-dipping planes. We also discuss the contraction trajectories derived from kinematics and geometry of active folding and faulting features observed within NNW Iran. Our study highlights two prominent sets of fan-shaped trajectories dominating in the west and east sides of the N–S zone in the Astara-Zanjan direction. We propose a couple-indentation geodynamic model to explain the fan-shaped pattern of these two laterally convergent sets of trajectories within the Talesh-Azerbaijan and Alborz domains.

Tectonic framework of the Paraná basin unveiled from gravity and magnetic data

The Paraná Basin, one of the most important Brazilian sedimentary basins, was created during the formation of Western Gondwana. Until recently, its tectonic framework has been studied mainly through indirect studies using geophysical data such as gravity, magnetic, as well as seismic reflection, and bore hole data. However, the last years, new geophysical data with better resolution became available, enabling new studies on the Brazilian sedimentary basins. To this end, the objective of this work is to contribute with new information on regarding the central and northern areas of the Parana basin and to investigate the major tectonic structures of its basement, as to understand the role of the Precambrian basement structures on its reactivation and geodynamics. For this purpose, quantitative and qualitative analysis of gravity and magnetic data were conducted using the Matched-Filter technique associated with enhancement filters, such as Total Horizontal Gradient and Tilt Derivative of the Total Horizontal Gradient. These geophysical products allowed interpreting the main geophysical lineaments and their depth. We identified structural patterns related to basement reactivation associated with the evolution of Western Gondwana. The NNE-SSW trending structures are related to reactivations of the Transbrasiliano and Paraíba do Sul Strike-slip Systems in the Late Ordovician. The NW-SE trending lineaments were generated with the tectonic growth of the Western Gondwana in the Triassic to the Late Jurassic, which started in the region of the Ponta Grossa Arch. This event was followed by the intracontinental magmatism in the Early Cretaceous. The E-W trending structures are related to the drifting of the South American Plate in the Late Cretaceous-Neogene and the faults originated from it, forming dextral binaries inside the plate pertaining to the Neotectonic Strike-slip System. The NNE-SSW, NE-SW, and NW-SE trending lineaments close to the border between the Paranapanema Block, the Goiano Domain, and the Araguaia, Paraguay, Brasília and Ribeira Belts are associated with suture zones. Thus, this work provides additional information related to the continuity of fault systems and crustal domain limits, as well as the extent of the crustal blocks in the basement of the Paraná Basin. It highlights the reactivation influence of the structures inherited from the Precambrian basement based on the results from both, gravity and magnetic data.

Archean and paleoproterozoic crust generation events, Amparo complex and Serra Negra orthogneiss in southern Brasília Orogen, SE Brazil

The Amparo Complex and Serra Negra orthogneisses consists largely of Archean and Paleoproterozoic domains, which represent the older tectonizied basement of Ribeira Belt, southeastern portion of the Brasília Neoproterozoic Orogenesis. This is the subject of UPb SHRIMP and Nd and Sr isotopic and geochemical investigations aiming to increase the knowledge of these juvenile crustal domains. In this region, older Meso and Neoarchean rocks occur in physical proximity to younger Paleoproterozoic rocks of Serra Negra Orthogneiss. Mesoarchean gneisses with UPb zircon ages of 2956 Ma have a composition of TTG suites with TDM of 3176 Ma and a ƐNd(t) of −0.14, suggesting derivation from the partial fusion of older mafic rocks. Mafic (amphibolite) and ultramafic rocks are associated with these domains. Neoarchean porphyritic granites are associated with the former rocks, occurring as intrusive high-K granites. They have a TDM value of 3404 Ma and a ƐNd (2.7Ga) of −4.29, which demonstrates their derivation from older Archean crust. Paleoproterozoic units occur throughout the belt represented by granodioritic or tonalitic orthogneiss with intercalations of amphibolites and ultramafic rocks. In the extension to the west the units crop out in the Campinas region, and to the east are denominated Pouso Alegre Complex. They constitute a TTG-type granite-tonalite suite, as verified by their geochemical signatures, REE and incompatible elements, high Na/Ca ratios, and negative anomalies of Ta, Nb, and Ti. SHRIMP UPb zircon ages are between 2.09 and 2.16 Ga (Rhyacian) with TDM between 2.11 and 2.36 Ga and ƐNd(2.1 Ga) between +0.88 and + 3.18, indicating juvenile nature. Low 87Sr/86Sri ratios disclose a possible contribution of mafic precursors in their origin. Neoproterozoic Ediacaran ages of Ribeira Belt event are seen in zircon crystals of all samples analyzed for this study. The effects of this Neoproterozoic orogenic event on basement rocks resulted in anatexis, banding and folding of the older rocks. As suggested for the Paleoproterozoic Pouso Alegre Complex, it is possibly an important period of juvenile continental growth that, in association with the Archean gneisses, may be related to the southern end of the São Francisco Craton.

Detrital fingerprint: The use of early Precambrian zircon age spectra as unique identifiers of Phanerozoic terranes

Archean and Proterozoic zircon grains are commonly found in much younger clastic sedimentary rocks, but the geological significance of these ages is often overlooked. Here we demonstrate that the age spectra of early Precambrian sedimentary recycled and/or magmatic inherited zircon grains form a unique pattern (detrital fingerprint) that can be used to test connectivity or indicate sediment recycling between terranes. Using the island of New Caledonia as a case study, we compiled 212 (published and new) concordant ages that are older than 1400 Ma from samples that represent contemporary sediments (this study), an allochthonous nappe sequence, and Paleozoic–Mesozoic metasedimentary rocks. By comparing these data with an equivalent dataset of Precambrian zircon ages (n>1400 Ma = 2636) from Paleozoic eastern Australia (Tasmanides), we test connectivity and disjunction of New Caledonia with crustal domains within the Tasmanides. Results show that the early Precambrian detrital fingerprint of New Caledonia is similar to the southern Tasmanides (and possibly East Antarctica), but is significantly different than the detrital fingerprint of the northern Tasmanides. The results thus provide an independent constraint on the origin of the late Paleozoic to early Mesozoic New Caledonian continental basement, shedding new light on the tectonic evolution of the southwestern Pacific region, and demonstrate the capabilities of the methodological approach.

Polyphase rifting and break-up of the central Mozambique margin

Abstract The break-up of the Gondwana supercontinent resulted in the formation of the Central Mozambique passive margin as Africa and Antarctica were separated during the mid-Jurassic period. Although plate kinematics during the oceanic spreading phase are well constrained, the initial fit of Africa and Antarctica, their earliest relative movements and margin architectures remain active areas of interest. This study uses high quality multi-channel seismic reflection profiles to identify the major crustal domains in the Angoche and Beira regions of the Central Mozambique margin. Our results show that the Central Mozambique passive margin is characterised by intense but localised magmatic activity, evidenced by the existence of seaward dipping reflectors (SDRs) in the Angoche region, and magmatic sills and volcanoclastic material marking the Beira High. The Angoche and Beira regions possess faulted upper-continental crusts, with possible exhumation of lower crustal material forming an extended ocean-continent transition (OCT). The Beira High segment reveals an offshore continental fragment, which is overlain by a faulted pre-rift sedimentary unit likely to belong to the Karoo Group. The combination of our seismic interpretation with existing geophysical and geological data has allowed us to propose a break-up model which supports the idea that the Central Mozambique margin was affected by polyphase rifting. The Beira High basement is formed by a strike-slip deformation along a proposed lithospheric weakness - the Lurio-Pebane shear zone. Northwestern-southeastern oriented extension follows and results in continental break-up and oceanic spreading. Our results suggest a segmentation of the Central Mozambique margin with oceanisation first occurring in the Angoche segment. The formation of the first oceanic crust in the Beira segment followed, likely delayed by the formation and failure of the northern Beira High rift.

From Continental Hyperextension to Seafloor Spreading: New Insights on the Porcupine Basin From Wide‐Angle Seismic Data

AbstractThe deep structure and sedimentary record of rift basins provide an important insight into understanding the geological processes involved in lithospheric extension. We investigate the crustal structure and large‐scale sedimentary architecture of the southern Porcupine Basin, offshore Ireland along three wide‐angle seismic profiles, supplemented by 13 selected seismic reflection profiles. The seismic velocity and crustal geometry models obtained by joint refraction and reflection traveltime inversion clearly image the deep structure of the basin. Our results suggest the presence of three distinct crustal domains along the rifting axis: (a) continental crust becoming progressively hyperextended from north to south through the basin, (b) a transitional zone of uncertain nature, and (c) a 7‐ to 8‐km‐thick zone of oceanic crust. The latter is overlain by an ~8‐km compacted Upper Paleozoic‐Mesozoic succession and ~ 2 km of Cenozoic strata. Due to the lack of clear magnetic anomalies and in the absence of well control, the precise age of interpreted oceanic crust is unknown. However, we can determine an age range of Late Jurassic to Late Cretaceous from the regional context. We propose a northward propagating rifting process in the Porcupine Basin, resulting in variations in strain along the rift axis.

Unraveling a distal segment of the West African Craton Paleozoic margin: Stratigraphy of the Mougueur inlier of the eastern High Atlas, Morocco

Because of its location in the boundary zone between the Anti-Atlas and the Atlas–Meseta crustal domains of Morocco, the Mougueur Paleozoic Massif is a key area to decipher the evolution of the Gondwana NW margin during the Paleozoic. In this work, we report for the first time the occurrence of Hirnantian sandstones, Silurian (Gorstian) graptolitic shales and probable Lower Devonian turbidites in the Massif. Comparison of our observations with regional stratigraphic data from literature allows us to suggest that the area was included in the distal part of the West African Craton passive margin during Cambrian-Devonian times.

Early Jurassic Rifting of the Arabian Passive Continental Margin of the Neo‐Tethys. Field Evidence From the Lurestan Region of the Zagros Fold‐and‐Thrust Belt, Iran

AbstractThe Arabian passive margin formed at the southern margin of the Neo‐Tethys ocean during the breakup of Pangea. In the Lurestan region of the Zagros mountain belt, the deformed Arabian continental paleo‐margin can be reconstructed as originally consisting of distinct crustal domains, including a proximal sector and a distal continental ribbon, separated by a deep‐water trough, known as the Radiolarite Basin. Such an architecture was shaped by the continental rifting process, thus reflecting timing and style of continent separation, which is generally assumed to have occurred during the Permo‐Triassic interval. This study reports evidence of syn‐sedimentary extensional faults, unconformities, and facies changes in the Mesozoic stratigraphic succession of the Lurestan region, which point to a major Jurassic extensional pulse. In detail, extension reached its climax at the end of the Early Jurassic, when tectonically driven drowning of the long‐lived Triassic to Early Jurassic carbonate platform led to the transition from shallow‐ to deep‐water environments in large areas of the inner margin, coevally with the development of the Radiolarite Basin. Our findings suggest a two‐step continental rifting in this area, with the first Permo‐Triassic phase predating an Early Jurassic one.

Zircon petrochronology reveals the timescale and mechanism of anatectic magma formation

Igneous rocks of intermediate to acidic composition commonly exhibit considerable degrees of isotope variability preserved at the crystal and sub-crystal scale, as well as a significant U–Pb age range, reflecting protracted timescales of zircon crystallization and long magma residence times. The association of high-precision U–Pb zircon dates with stable and radiogenic isotope data represents a powerful tool to unravel the petrological evolution of granitic rocks, hence allowing a better understanding of the processes that led to the formation and reworking of the continental crust.In this case study, we combine high-precision U–Pb dates with stable and radiogenic isotope data from zircon crystals in the Larderello–Travale (Italy) shallow-level granites. These rocks are peraluminous two-mica, cordierite-bearing granites and represent pure crustal anatectic magmas, generated in a post-collisional extensional setting. As such, they are ideal candidates to investigate the timing, rates and mechanisms of melt production during anatectic magma formation, giving insights into the process of intracrustal differentiation. Magmatic zircon crystals from the Larderello–Travale granites contain δ18O values ranging from 8.6 to 13.5‰ and crystals from individual samples exhibit inter- and intra-grain oxygen isotope variability exceeding 3‰. The analysed crystals have εHf values ranging between −7.4 and −12.4, with moderate, intra-sample εHf isotope variability. All CA-ID-TIMS (chemical abration isotope-dilution thermal ionization mass spectrometry) 206Pb/238U zircon ages range from 4.5 to 1.6 Ma and suggest four pulses of magmatic activity at ∼3.6, 3.2, 2.7 and 1.6 Ma. More importantly, zircon crystals from individual samples typically exhibit an age spread as large as 300–500 ka. This age dispersion suggests that most of the zircon did not crystallize at the emplacement level but in the middle crust and were subsequently recycled and juxtaposed during ascent and emplaced at shallow level. When plotted against age, stable and radiogenic isotope data suggest the co-existence of multiple and isotopically distinct magma batches produced by partial melting of different crustal domains. This requires coeval magma batches that are physically separated and evolve independently for hundreds of thousands of years before coalescing during ascent and emplacement. The involvement of multiple sources in the production of crustal anatectic magmas reflects the inherent heterogeneous nature of the continental crust and result from the interplay between the rise and evolution of the geotherms through the crust and the composition of the fertile source rocks. Finally, the isotopically diverse zircon-bearing magma batches mixed and assembled into shallow-level intrusions generated during the four major magma pulses.

Crustal architecture and its controls on mineralisation in the North China Craton

Knowledge of the history of the Earth’s continents and the genesis of mineral deposits is poorly understood on a crustal-scale. This contribution combines geological and zircon Hf-isotopic data collected from igneous rocks associated with mineralisation to gain a better understanding of the nature of the growth of, and mineral genesis in the North China Craton. The new zircon U–Pb dates reported here are 2587 ± 62 Ma for syenogranite at Zanhuang in the northeast part of craton, 2552 ± 24 Ma for trondhjemitic gneiss and 2554 ± 29 Ma for metadiorite at Dengfeng in the eastern and central part of, and 2820 ± 6 and 2821 ± 32 Ma for tonalite at Lushan in the southeast part of the craton. Lu-Hf isotopic data collected from granitic rocks for this study yield εHf(t) values and Hf crustal model ages (TDMc) of 3–5.8 and 2580–2600 Ma for the syenogranite at Zanhuang, 1.9–7.4 and 2550–2580 Ma for trondhjemitic gneiss and metadiorite at Dengfeng, and 0.5–5.2 and 3120–2840 Ma for tonalite at Lushan. Six major magmatic events have been recognised throughout the region. The crustal growth and reworking of the craton includes Eo- to Mesoarchean, early Neoarchean, and Paleoproterozoic events. The consistency in the evolution of Neoarchean magmatism coupled with zircon Hf isotope systematics indicate that similar crustal growth and reworking were in action in the Eastern, Trans-North China, and Western blocks. The crust architecture indicated by Hf isotopic mapping of the North China Craton constrains the distribution of mineral deposits. The BIF-hosted Fe deposits are spatially related to juvenile or reworked crustal domains, with groups of deposits located internal to and at the margins of Archean terranes, and orogenic Au deposits are spatially associated with juvenile crustal domains.

The crustal structure in the transition zone between the western and eastern Barents Sea

We present a crustal-scale seismic profile in the Barents Sea based on new data. Wide-angle seismic data were recorded along a 600 km long profile at 38 ocean bottom seismometer and 52 onshore station locations. The modeling uses the joint refraction/reflection tomography approach where co-located multi-channel seismic reflection data constrain the sedimentary structure. Further, forward gravity modeling is based on the seismic model. We also calculate net regional erosion based on the calculated shallow velocity structure. Our model reveals a complex crustal structure of the Baltic Shield to Barents shelf transition zone, as well as strong structural variability on the shelf itself. We document large volumes of pre-Carboniferous sedimentary strata in the transition zone which reach a total thickness of 10 km. A high-velocity crustal domain found below the Varanger Peninsula likely represents an independent crustal block. Large lower crustal bodies with very high velocity and density below the Varanger Peninsula and the Fedynsky High are interpreted as underplated material that may have fed mafic dykes in the Devonian. We speculate that these lower crustal bodies are linked to the Devonian rifting processes in the East European Craton, or belonging to the integral part of the Timanides, as observed onshore in the Pechora Basin.

Nd and Pb isotope mapping of crustal domains within the Makkovik Province, Labrador

AbstractThe Makkovik Province of eastern Labrador represents part of an accretionary orogen active during an early stage in the development of the Palaeoproterozoic southern Laurentian continental margin. New Nd isotope data for the eastern Makkovik Province suggest that accreted juvenile Makkovik crust was generated in the Cape Harrison domain during a single crust-forming event at c. 2.0 Ga. Pb isotope data support this model, and show a strong similarity to radiogenic crustal signatures in the juvenile Palaeoproterozoic crust of the Ketilidian mobile belt of southern Greenland. As previously proposed, an arc accretion event at c. 1.9 Ga triggered subduction-zone reversal and the development of an ensialic arc on the composite margin. After the subduction flip, a temporary release of compressive stress at c. 1.87 Ga led to the development of a retro-arc foreland basin on the downloaded Archean continental edge, forming the Aillik Group. Unlike previous models, a second arc is not envisaged. Instead, a compressive regime at c. 1.82 Ga is attributed to continued ensialic arc plutonism on the existing margin. The tectonic model for the Makkovikian orogeny proposed here is similar to that for the Ketilidian orogeny. Major- and trace-element analyses suggest that much of the magmatism in the Makkovik orogen results from post-accretionary ensialic arc activity, and that few vestiges remain of the original accreted volcanic arc. This pattern of arc accretion and intense post-accretion reworking is common to many accretionary orogens, such as the South American Andes and North American Cordillera.

Basement characterization and crustal structure beneath the Arabia–Eurasia collision (Iran): A combined gravity and magnetic study

We present a study on the depth to basement and magnetic crustal domains beneath the Iranian Plateau by modeling aeromagnetic and gravity data. First, field processing of the aeromagnetic data was undertaken to estimate the general characteristics of the magnetic basement. Afterwards, inverse modeling of aeromagnetic data was carried out to estimate the depth to basement. The obtained model of basement was refined using combined gravity and magnetic forward modeling. Hereby, we were able to distinguish different magnetic domains in the uppermost crust (10–20 km depths) influencing the medium to long wavelength trends of the magnetic anomalies. Magnetic basement mapping shows that prominent shallow magnetic features are furthermore located in the volcanic areas, e.g. the Urumieh Dokhtar Magmatic Assemblage. The presence of ophiolite outcrops in SE Iran implies that shallow oceanic crust (with high magnetization) is the main source of one of the biggest magnetic anomalies in entire Iran area located north of the Makran.

Crustal architecture of the East Siberian Arctic Shelf and adjacent Arctic Ocean constrained by seismic data and gravity modeling results

The Eastern Siberian Arctic Shelf (ESAS) represents a geologically complex realm with a tectonic history that is related to the final stages of the formation of the Pangaea supercontinent during the Mesozoic and its subsequent disintegration during the Late Cretaceous and Cenozoic. It is a key region to constrain the origin of the deep-water basins and intervening ridges of the Amerasia Basin. We present results of gravity modeling of published seismic refraction and reflection profiles acquired between 1989 and 2012 over the ESAS and adjacent Arctic Ocean along five composite geotransects using Getech’s satellite altimeter-derived gravity data. Our main goal was to examine published crustal models and to present new models for the ESAS that are constrained by both seismic data and 2D gravity forward modeling. We consider several topics important for understanding Arctic geology: (i) hyperextension within the Laptev Rift System and the possible extent of the exhumed mantle, (ii) the relationship between the New Siberian Shelf and the Lomonosov Ridge, (iii) the nature of the collapsed upper Mesozoic fold belt in the southern part of the East Siberian Sea, (iv) the character of transition between the De Long Massif and the deep-water Podvodnikov Basin, (v) the lateral extent of the hyperextended North Chukchi Basin and the nature of its basement, and (vi) relationship between the Mendeleev Ridge and Chukchi Plateau crustal domains. Our results do not confirm the previously inferred extent of continental crust beneath the oceanic realm. The latter is dominated by High Arctic Large Igneous Province (HALIP) igneous crust. We discuss the existence of a dismembered continental Bennett-Barrovia block that is currently represented by three smaller fragments/massifs. When restored to its possible single state, this block can play a crucial role in reconstructing the pre-Canada Basin Arctic.

Transition From Collisional to Subduction‐Related Regimes: An Example From Neogene Panama‐Nazca‐South America Interactions

AbstractA geological transect across the suture separating northwestern South America from the Panama Arc helps document the provenance and thermal history of both crustal domains and the suture zone. During middle Miocene, strata were being accumulated over the suture zone between the Panama Arc and the continental margin. Integrated provenance analyses of those middle Miocene strata show the presence of mixed sources that includes material derived from the two major crustal domains: the old northwestern South American orogens and the younger Panama Arc. Coeval moderately rapid exhumation of Upper Cretaceous to Paleogene sediments forming the reference continental margin is suggested from our inverse thermal modeling. Strata within the suture zone are intruded by ~12 Ma magmatic arc‐related plutons, marking the transition from a collisional orogen to a subduction‐related one. Renewed late Miocene to Pliocene acceleration of the exhumation rates is the consequence of a second tectonic pulse, which is likely to be triggered by the onset of a flat‐slab subduction of the Nazca plate underneath the northernmost Andes of Colombia, suggesting that late Miocene to Pliocene orogeny in the Northern Andes is controlled by at least two different tectonic mechanisms.

Longitudinal and Temporal Evolution of the Tectonic Style Along the Cyprus Arc System, Assessed Through 2‐D Reflection Seismic Interpretation

AbstractThe Cyprus Arc system constitutes a major active plate boundary in the eastern Mediterranean region. This structure is directly linked with the northward convergence of the African and Eurasian plates since the Late Cretaceous. Two‐dimensional reflection seismic data were utilized, which image the main plate structures and their lateral evolution south of the island of Cyprus. Interpretation of these data allowed the identification of nine tectono‐sedimentary packages in three different crustal domains south of the Cyprus Arc system: (1) the Levant Basin (attenuated continental crust), (2) the Eratosthenes microcontinent (continental crust), and (3) the Herodotus Basin (oceanic crust). Within these domains, numerous tectonic structures were documented and analyzed in order to understand the mechanism and timing of deformation. In the north, south verging thrusting commenced in early Miocene along the Larnaca and Margat ridges, whereas no activity was identified before middle Miocene along the Latakia Ridge. Thus, the deformation front migrated southward and was accompanied by the development of flexural basins and stratigraphic onlaps as in the Cyprus Basin. The acme of deformation occurred in mid‐late Miocene. A regional unconformity of Pliocene age marks the end of the first deformation sequence. In Plio‐Pleistocene time, the westward escape of the Anatolian microplate resulted in the reactivation of existing structures. The evolution of deformation along the plate boundary is identified from the creation of positive flower structures revealing transpressive movements along the Larnaca and Latakia Ridges (eastern domains), whereas in the Eratosthenes domain a flexural basin highlights a compressive regime.

Intraplate volcanism in the Danube Basin of NW Hungary: 3D geophysical modelling of the Late Miocene Pásztori volcano

Three-dimensional geophysical modelling of the early Late Miocene Pasztori volcano (ca. 11–10 Ma) and adjacent area in the Little Hungarian Plain Volcanic Field of the Danube Basin was carried out to get an insight into the most prominent intra-crustal structures here. We have used gridded gravity and magnetic data, interpreted seismic reflection sections and borehole data combined with re-evaluated geological constraints. Based on petrological analysis of core samples from available six exploration boreholes, the volcanic rocks consist of a series of alkaline trachytic and trachyandesitic volcanoclastic and effusive rocks. The measured magnetic susceptibilities of these samples are generally very low suggesting a deeper magnetic source. The age of the modelled Pasztori volcano, buried beneath a 2 km-thick Late Miocene-to-Quaternary sedimentary sequence, is 10.4 +/− 0.3 Ma belonging to the dominantly normal C5 chron. Our model includes crustal domains with different effective induced magnetizations and densities: uppermost 0.3–1.8 km thick layer of volcanoclastics underlain by a trachytic-trachyandesitic coherent and volcanoclastic rock units of a maximum 2 km thickness, with a top situated at minimal depth of 2.3 km, and a deeper magmatic pluton in a depth range of 5–15 km. The 3D model of the Danube Basin is consistent with observed high ΔZ magnetic anomalies above the volcano, while the observed Bouguer gravity anomalies correlate better with the crystalline basement depth. Our analysis contributes to deeper understanding of the crustal architecture and the evolution of the basin accompanied by alkaline intraplate volcanism.

Jequitinhonha Basin: Structural aspects, relationship with igneous activity, and hydrocarbon exudations

The Jequitinhonha Basin (JB) is one of the sedimentary basins in the Brazilian Eastern Margin. Although several regional studies have been conducted to define its tectonic framework and petroleum system, neither one is very well-understood. For instance, the extent and influence of the volcanic rocks in the petroleum system of the JB are still matters of debate among geoscientists. We found a new integrated interpretation for the structural framework of JB in which we discover the major faults, the mapped volcanics, and a new basement map. Finally, we evaluate the correlation of known exudation occurrences with our findings. Several exudation occurrences are observed in the evaporite province (to the north), although only one exudation occurrence is seen in the Royal Charlotte domain (to the south) thus corroborating the negative impact of the Abrolhos magmatic event for the petroleum systems in the JB. At least seven exudation occurrences are observed in the oceanic crustal domain. This fact strengthens the possibility of the existence of an Urucutuca-Urucutuca postrift petroleum system.

Gulfs of Suez and Aqaba: New insights from recent satellite-marine potential field data

Previous models and interpretations of crustal geometry and the nature of the crust under the Gulfs of Suez and Aqaba have generally been based on a local or small scale and have been limited due to a lack of data. The few studies that present larger scale crustal and uppermost mantle structure were dependent on one type of data with no consideration of other geological and/or geophysical features. Satellite-marine potential field data provide for the first time a full coverage dataset of the Gulfs of Suez and Aqaba as well as the Sinai area at the same scale which allows for a better understanding of crustal domains and geometry and the interplay between tectonic events. To that end, our forward models of magnetic and gravity data constrained by seismic data and available geological information in this area suggest that the crustal domains in the Gulf of Aqaba are more complicated than those in the Gulf of Suez. Our result supports continental rifting under most of the Gulf of Suez and a combination of transitional and continental crusts under the Gulf of Aqaba. Yet, there is no evidence of oceanic segment development in these gulfs. Regardless of oceanic or transitional crust, the models support a link between the Arabia and Sinai plates at the central Gulf of Aqaba. The data also support that Red Sea tectonism has no connection to or influence on both gulfs. The result suggests a continuation of lithological elements from land into the eastern part of the Gulf of Suez. Our synthesis and interpretations may play an important role in the reassessment of the tectonic history and extension of this important rift system.