Rift Evolution Research Articles

New insights into the thermo‐tectonic development of the Suez rift within the framework of the northern Arabian–Nubian Shield

AbstractThe Gulf of Suez is a young continental rift, the flanks of which make up the Arabian–Nubian Shield basement complex that formed during the East African Orogeny. The impact and significance of the consecutive tectono‐thermal activities on the Arabian–Nubian Shield and the rifting processes in the Gulf of Suez remain uncertain. Combining zircon and apatite fission‐track dating with time–temperature modelling has been effective in addressing these issues. We here present thermochronological data for 20 basement samples collected from the Samra Mountain region at the northern tip of the Gulf of Suez's eastern flank. Zircon fission‐track data revealed two age groups separated spatially and dating from ca. 652 ± 25 Ma and ca. 426 ± 31 Ma. In contrast, apatite fission‐track data revealed three spatially separated age groups dating from ca. 473 ± 10 Ma, ca. 269 ± 29 Ma and ca. 101 ± 12 Ma. Reconstructed time–temperature historical records revealed four distinct rapid cooling pulses (i.e. Neoproterozoic, Devonian–Carboniferous, Cretaceous and Oligocene–Miocene) consistent with the tectonic history and regional geology. By integrating our findings with the regional tectonic and sedimentation histories, the relationship between cooling events and exhumation events could be inferred. These cooling pulses were activated in response to four events: (1) the Precambrian–Cambrian post‐accretion erosional event, (2) the Devonian–Carboniferous Variscan tectonic event, (3) the Cretaceous Gondwana disintegration and (4) the Oligocene–Miocene Gulf of Suez rifting, respectively. In the studied region, no thermal overprint was seen in association with the rifting in the Gulf of Suez, suggesting that the region had been segmented into northern and southern segments. A southward thermal source, the Arabian margin plume, caused an increase in the rift flank elevation and heat flow in the southern Sinai.

From Orogeny to Rifting: The Role of Inherited Structures During the Formation of the South China Sea

AbstractMany of the world's rifts and rifted margins have developed within former orogens. The South China Sea (SCS) formed during Cenozoic rifting by utilizing pre‐existing orogenic structures, like thrust faults, thickened crust, and corresponding thermal weaknesses. The mechanisms explaining how inherited structures influence the spatiotemporal evolution of a rift remain a topic of on‐going research. Here, we explore the impact of orogenic inheritance on rift evolution through a numerical forward model that reproduces geodynamic and landscape evolution processes. By imposing time‐dependent phases of shortening and extension, we model rifted margin formation that is consistent with the available geological and geophysical observations of the SCS. Our numerical models allow us to identify thrust faults that are reactivated as normal faults during extensional phases. Not all pre‐existing thrust faults, however, undergo full reactivation, as their behavior is influenced by variations in lithospheric strength and the pre‐existing structural discontinuities. We further show that inherited orogenic structures compete with each other during extensional reactivation and ultimately govern the location of continental breakup. Our results provide valuable insights into the broader implications of inherited orogenic structures and how they affect subsequent rift system evolution.

Magmatic activity in incipient continental break-up as revealed by coupling melt and fluid inclusions

Abstract Deciphering deep magmatic processes driving the onset of continental break-up is fundamental to constrain our understanding of plate tectonics. The East African Rift System (EARS) is the only currently active system on Earth to study distinct stages of rift evolution. We present a coupled analysis of melt and fluid inclusions in the Virunga Volcanic Province (VVP) offering an unprecedented insight into the dynamics of incipient rifting and its evolution. Our study highlights that melting of distinct metasomes in the deep lithosphere is a common feature of immature rifts. In the VVP, it leads to the emission of nephelinitic and basanitic melts at Nyiragongo and Nyamulagira volcanoes, respectively. Additionally, the chemical composition of melt and fluid inclusions supports the identification of another magmatic series in the area. Related alkali basaltic melts would be produced by contemporary melting of a less enriched domain in the upper lithosphere, more classically documented in mature rifts. Various extents of mixing and crystallisation of these three distinct magmatic series occur in the lower crust beneath the VVP where the barometric estimates are consistent with the presence of a thick seismic low velocity zone (LVZ). The involvement of alkali basaltic melts in the regional magma production could be also detected in the spread of gas emissions in the rift valley and in the fumaroles of the main active volcanoes. Melting of the corresponding mantle domain is an added source of gas release that may largely contribute to CO2 emissions along the EARS.

Early Paleogene alkaline magmatism in the Subandean Ranges of Jujuy Province

The Zapla Range (Jujuy province) represents the southern edge of the central Andean Subandean Ranges in Argentina. In the northernmost area of the Zapla Range, basaltic rocks are interbedded in the Mealla Formation. These volcanic units form part of the post-rift magmatism of the Salta rift basin, which mainly focused on the Lomas de Olmedo sub-basin to the east. In this paper, six of these basaltic occurrences are characterized on the basis of new geological, petrographic and geochemical data, in order to explore their emplacement, petrogenesis and possible tectonic setting during rift evolution. Peperites in the upper contact of sills evidence the interaction between basalts and unconsolidated or poorly consolidated wet sediments. This implies that there was concomitance between sedimentation and subsurface magma emplacement, suggesting a Paleocene age for the magmatic event according to zircon U-Pb data available for Mealla Formation rocks. Other basaltic units show hipocrystalline textures and lack peperites at the top, which points to their extrusive nature. Additionally, some of these lava flows are spatially associated with pyroclastic deposits that reveal the occurrence of explosive hydrovolcanic eruptions. The study rocks are classified as alkaline basalts and basanites with high Mg# and Ni- and Cr-rich compositions, close to primitive magmas. They show affinity with continental intraplate settings. The analyses of Ba/Nb, Nb/La, (La/Yb)N, (La/Sm)N, (Gd/Yb)N and (Dy/Yb)N ratios, as well as normalized trace and rare earth element patterns, suggests a genesis by low degrees of partial melting of a residual garnet-bearing mantle source. Therefore, basalts from this part of the Subandean Ranges evidence a magmatic episode probably linked to an extensional reactivation stage of the Salta Group rift system in the Lomas de Olmedo depocenter during the Paleocene (∼60 Ma).

Deflected Mantle Flow and Shearing‐Aligned Lithospheric Melt Under the Strike‐Slip Dead Sea Rift

AbstractContinental rifting is one of the fundamental tectonics of the Earth evolution while our current understandings on the dynamic mechanism of the strike‐slip ones are relatively limited. Here, we have utilized three kinds of core‐refracted shear waves (including PKS, SKKS, and SKS) and employed the shear‐wave splitting technique to systematically investigate the azimuthal anisotropy of the upper mantle under the typical strike‐slip Dead Sea rift. There are a total of 1,855 well‐determined anisotropic measurements from 187 stations with dominantly N‐S fast orientations. We have proposed a new model from a joint analysis of multiple newly available geophysical observations to interpret the resulting anisotropy as mainly due to the absolute‐plate‐motion‐driven mantle flow deflected by the thick lithosphere of the eastern Arabian plate. Relatively larger splitting times are locally revealed at the rift zone and attributed to additional lithospheric anisotropy from the shearing‐oriented melt pockets whose existence further induces complex anisotropy with slight difference of fast orientations between the upper and lower layer anisotropy. The overall rift‐parallel fast orientations, when combined with the absence of low‐velocity and hot thermal anomalies in the mantle transition zone, rule out the role of mantle plume or edge‐driven convection in the rift development and further infer the Dead Sea rift to evolve in a passive mode.

Geomorphic expressions of active rifting reflect the role of structural inheritance: a new model for the evolution of the Shanxi Rift, northern China

Abstract. Many rifts are influenced by pre-existing structures and heterogeneities during their evolution, a process known as structural inheritance. During rift evolution, these heterogeneities may aid rift nucleation, rift growth, and the segmentation of faults; encourage the linkage of various segments; or even inhibit the formation of faults. Understanding how structural inheritance influences early rift evolution could be vital for evaluating seismic risk in tectonically active areas. The Shanxi Rift in the north of China is an active rift system believed to have formed along the trend of the Proterozoic Trans-North China Orogen; however, the influence of these pre-existing structures on the present-day rift architecture is poorly understood. Here, we use tectonic geomorphological techniques, e.g. the hypsometric integral (HI), channel steepness (ksn), and local relief, to study the evolution of the Shanxi Rift and identify areas of higher tectonic activity. We found that the HI was less sensitive to lithology and more valuable in evaluating the tectonic signal and that activity is concentrated in two rift interaction zones (RIZs) formed between the Xinding, Taiyuan, and Linfen basins. We then evaluated the relationship between the active faults and mapped pre-existing structures, finding that many faults formed parallel to inherited structures, while faults in the RIZs often cross-cut these structures. Based on these observations, we propose a new model for the evolution of the Shanxi Rift, where inherited structures play an important role in the initial segmentation of the rift, which, in turn, controls the development of the RIZ structures.

Continental rift evolution and drainage reorganization along the Dead Sea rift since the Miocene

The Dead Sea fault is a section of the Arabian-African plate boundary. Widespread field relations indicate that three major drainage systems (stages) occupied the landscape west of the Dead Sea fault since its initiation at ca. 20 Ma. Specifically, (1) an early to middle Miocene drainage system, only minorly reconfigured by the fault (all sediments of this system belong to the Hazeva Formation); (2) a late Miocene to early Pleistocene fault-parallel drainage system named Paran-Neqarot (all sediments of this system belong to the Arava and Zehiha Formations; and (3) the early Pleistocene to present drainage configuration. The temporal and spatial frameworks of drainage stage 1 are generally constrained by radiometric dating of interfingering volcanic units, and the onset and temporal and spatial frameworks of drainage stage 3 are well constrained by cosmogenic 10Be surface exposure ages. The timing and longevity of the rift-parallel drainage (stage 2) have until now been evasive to direct dating. The overall time gap between stages 1 and 3 is ∼12−13 million years. Thus, an early age (within this time gap) of stage 2 would imply an immediate response of drainage reorganization to rift tectonics, while a later age of this drainage system would imply a delayed response. We present 11 10Be-26Al cosmogenic burial ages of alluvial and colluvial units related to the fault-parallel drainage system (stage 2), which collectively constrain the time of deposition of the Arava Formation sediments in the central Negev to ca. 8 Ma. The general lack of stratigraphic order, together with the large dispersion of ages both across and within the sampling sites, attests to significant recycling of sediments from drainage stage 1 into the Arava Formation deposits. The termination of Arava and Zehiha Formation sediment deposition at ca. 1.8 Ma was determined previously using cosmogenic exposure ages of desert pavements that cover the formations. Combining the previously published data with our new data, we established the longevity and character of the Paran-Neqarot drainage system. This framework highlights the temporal aspect of drainage system build-up and collapse as it responded to transform and extensional plate boundary tectonics during the Neogene.

The effect of pre-existing structures on the Cenozoic rifting processes: Insights from seismic reflection imaging of the northeastern south China sea

The South China Sea (SCS) opened due to the extension of a compressional setting of the paleo-Pacific subduction. The pre-existing structure significantly influences the geometry of rift basins and the kinematic evolution of the rifting. However, structural evidence of the paleo-Pacific subduction in the northeastern SCS remains enigmatic. The deformation front, serving as the structural evidence of paleo-subduction, is associated with accretionary style deformation and would be reactivated during the subsequent extension phase. In this study, we use a multi-channel seismic profile to investigate the pre-existing structure related to the paleo-Pacific subduction in the northeastern SCS, emphasizing the influence of pre-existing structure on the rift evolution. The seismic profile reveals imbricate reflections in the lower crust. These reflections are interpreted as the deformation front of the Paleo-Pacific subduction. Notably, the deformation front is hyperextended in the Chaoshan Depression. The result of the stretching factors indicates that the ductile lower crust experienced preferential thinning during the rifting beneath the Chaoshan Depression. In the northern part of the profile, a transparent reflection zone was identified and interpreted as a magmatic arc related to Mesozoic subduction. One major achievement of our study is these seismic reflections provide the structural evidence for Paleo-Pacific subduction and reveal that the northeastern SCS has experienced crustal shortening and imbrication through a series of dipping thrusts. Subsequently, we discuss the role of pre-existing structures in lower crustal thinning and continental rifting. We propose the deformation front of the Mesozoic subduction, as a pre-existing weakness, facilitated the kinematic evolution of the rifting in the northeastern SCS during the Cenozoic.

Late Ediacaran to Early Cambrian stratigraphic correlation and its geological implications in the northwestern Sichuan Basin: insights from phosphorus, isotopes, and small shelly fossils

The characteristics of elements, isotopes, and small shelly fossils were investigated for Late Ediacaran to Early Cambrian stratigraphy division and to discuss their geological implications in the northwestern Sichuan Basin. The results reveal that small shelly fossils can be detected in the high-phosphorous section, with the concentration of phosphorus mainly ranging from 2% to 8%, suggesting that this interval belongs to the Early Cambrian, which is also consistent with the carbon isotopic composition results. In addition, the Early Cambrian is denudated in the Sichuan Basin due to tectonic movement, and the characteristics of some isotopes and small shell fossils are different from those in other basins. It can be proposed that P content can support the recognition of lithological boundaries, and the high phosphorus content can be used as a reference to identify the top and bottom boundaries of the Maidiping Formation in the study area. According to the elemental compositions in the Ediacaran Dengying Formation, the variations in Si, Al, Fe, and K contents are similar in the platform area and rift area, suggesting that the third and fourth member of the Dengying Formation are also developed in the Deyang–Anyue Rift. The results suggest that both the Deng-4 member and Maidiping Formation feature contemporaneous deposition of different facies in the northwestern Sichuan Basin. The strata consist of shale intercalated with thin carbonate rock deposits in the Deyang–Anyue Rift, while carbonate rock deposits in the platform. The Deyang–Anyue Rift expanded gradually in the Late Ediacaran and eventually filled in the Early Cambrian. The data in this study illustrate that elemental compositions, isotopes, and small shelly fossils can be combined to correlate the Late Ediacaran to Early Cambrian strata and provide new evidence for Deyang–Anyue Rift evolution. The results offer some new insights for deep oil and gas exploration in the Sichuan Basin and for the tectonic–depositional–environmental–biological synergistic evolution in the Late Ediacaran to Early Cambrian transition.

The influence of the strength of pre-existing weak zones on rift geometry and strain localization

Continental rifts normally initiate within previously deformed lithosphere and thus their evolution and architecture can be largely controlled by inherited weak zones in the pre-rift crust. Here, we quantify the role of the strength and obliquity of pre-existing crustal-scale weak zones in the evolution of continental rift systems. We use a 3D numerical geodynamic model to assess strain localization, associated fault development, and rift segmentation during the early stages of tectonic extension. We find that both the strength and obliquity of the weak zones significantly influence the patterns of strain localization. A pre-existing very weak zone with low obliquity can promote the development of continuous and long-lived border faults parallel to the rift axis. Conversely, a comparatively strong weak zone with high obliquity leads to a staggered en-echelon rift geometry that lacks rectilinear laterally persistent strain localization. Furthermore, we find that rift obliquity and weak zone strength may modulate rift fault length, throw, and azimuth. These results provide new and compelling insights into the structure and evolution of natural active rifts that develop within orogenic basement terranes.

Density structures of the upper mantle in the East African Rift System: implications for the evolution of intracontinental rifting

The East African Rift System (EARS) provides an ideal natural laboratory for studying the mechanisms of tectonic plate breakup and continental drift, as well as a unique perspective for exploring the maturation process of continental rifting and its drivers. This study combines high-resolution satellite gravity data and seismic tomography model with an integrated geophysical approach to reveal the density structures in the upper mantle of the EARS. The results show that the northeastern to central Congo and Zimbabwe Craton exhibit significant high-density anomalies extending up to 250 km, which is indicative of a thicker and more intact lithosphere. In contrast, the Uganda, Tanzania, eastern and southern Congo, and Kaapvaal Craton show shallow high-density anomalies underlain by low-density anomalies that are clearly derived from the deeper mantle, indicating a thining of the lithosphere with some degree of possible melting at the base. The various rift segments of the EARS exhibit different rift morphologies. The Main Ethiopian Rift and the Kenya Rift of the Eastern Rift Branch show strong low-density anomalies, indicating intense melting, which is much stronger than that observed in the Western Rift Branch. However, the two rifts may have originated from the same mantle uplift in which the low-density anomalies of the Eastern and Western Rift Branches connected in the deep upper mantle. The lower portion of the Malawi Rift exhibits weaker low-denstiy anomalies, which can be observed to the south of the Malawi Rift, extending further south as a continuation of the EARS. Combining the results of previous kinetics simulations and our density perturbation results, it can be inferred that the Eastern Rift Branch is mainly affected by active rifting, while the Western Rift Branch is affected by both active and passive rifting.

Rift and plume: a discussion on active and passive rifting mechanisms in the Afro-Arabian rift based on synthesis of geophysical data

Abstract. The causal relationship between the activity of mantle plumes and continental break-up is still elusive. The Afro-Arabian rift system offers an opportunity to examine these relationships, in which an ongoing continental break-up intersects a large Cenozoic plume-related flood basalt series. In the Afar region, the Gulf of Aden, the Red Sea, and the Main Ethiopian Rift form an R-R-R triple junction within plume-related flood basalt series. We provide an up-to-date synthesis of the available geophysical and geological data from this region. We map the rift architecture in the intersection region by applying the difference in Gaussians to the topography and the bathymetry and interpreting vertical gravity gradients and Bouguer anomalies. With the aid of these methods we review the spatiotemporal constraints in the evolution of the different features of the plume–rift system. Our results show rough and irregular morphologies of the Gulf of Aden and the Red Sea arms in contrast to the symmetric, continuous, and smooth Main Ethiopian Rift. The triple junction formed by the northeastward propagation of the Main Ethiopian Rift and developed simultaneously with the abandonment of the tectonic connection between the Red Sea and the Gulf of Aden through Bab al Mandab Strait. The triple junction was the last feature to develop in the plume–rift system and marked a tectonic reorganization. By this time, all rift arms were sufficiently evolved and the break-up between Africa and Arabia was already accomplished. We argue that the classical active and passive rifting mechanisms cannot simply explain the progressive development of the Afro-Arabian rift. Instead, we propose a plume-induced plate rotation, which includes an interaction between active and passive mechanisms. In this tectonic scenario, the arrival of the Afar plume provided a push force that promoted the rotation of Arabia around a nearby pole located to the northwest of the plate boundary, enabling the rifting and, ultimately, the break-up of Arabia from Africa.

The Tectonic Structure and Evolution of the Potiguar‐Ceará Rifted Margin of Brazil

AbstractThe Brazilian Equatorial Margin (BEM) is interpreted as a transform margin, where the last segment opened during Gondwana rifting. However, margin evolution, and break‐up age remain unconstrained. We interpret >10k km of crustal‐scale seismic images extending along ∼600 km of the margin calibrated with drillholes. We determine the style and timing of tectonics across the rift system. We link changes in crustal‐scale structure and age of sediment deposits to interpret variations with the style of extension and intensity of thinning across the BEM. Observations support a rift evolution where deformation is initially distributed forming a shallow basin, subsequently focusses, and later migrates basin‐ward forming the deep‐water domain. We interpret that tectonic activity started ∼140–136 Ma and stopped earlier in the shallow basin causing minor thinning, than in the deep‐water domain with a ∼60 km wide area with 4–8 km thick crust extended in Late Aptian to Early Albian (116–110 Ma). Constraints from seismic and drilling help define an abrupt continent to ocean transition (COT) where continental crust may be abutted by oceanic crust, and breakup occurred at early Albian time. Basin sedimentation from the onset to the Late Aptian is continental, indicating an isolated environment disconnected from Atlantic oceans. During late‐most Aptian to Early Albian basin sedimentation changes and indicates a comparatively rapid marine water infill. Rifting of the BEM is not dominated by transcurrent deformation as previously inferred, with strike‐slip faulting limited to comparatively small sectors, whereas most of the margin extended by normal faulting deformation.

Eocene to Miocene sediment provenance features and evolution history of the western slope area in the Xihu Sag of the East China Sea Continental Shelf Basin

Rift basins are commonly characterised by multiple sediment sources (e.g. transverse and longitudinal) that change over time during different rifting evolution stages. Therefore, tracing sediment provenance to decipher the sedimentary source-to-sink analyses processes in rift basins is important to predict sandy reservoirs. The Xihu Sag in the East China Sea Shelf Basin, particularly its western slope, features large-scale sand bodies of unclear origin. We used petrography, heavy minerals and geochemistry to study sediment provenance in the Eocene Baoshi to Miocene Longjing formations. Our work suggests there are three distinct areas (namely zones A, B and C) affected by different source areas. Zone A, influenced by the Hupijiao uplift, primarily contains metamorphic rock minerals; Zone B, affected by the Haijiao and Hupijiao uplifts, contains igneous and metamorphic rock minerals; and Zone C, dominated by the Haijiao uplift, features igneous with some metamorphic sources, which increase over time, indicating stronger sediment input from the northern Hupijiao uplift. Rare earth element analysis suggests a continental margin and island arc setting, primarily with intermediate–acid felsic rock sources. However, a Eu negative anomaly in Eocene upper Pinghu Formation to the Miocene Longjing Formation indicates some basic source contributions, possibly from a volcanic belt east of the South Yellow Sea. This intermediate–basic volcanic rock belt is located to the northwest of the Hupijiao uplift and may provide clasts for zones A and B through axial channels. These findings indicate that varied sediment sources in the different zones and basin evolution stages with a growing extra-basinal contribution from the Eocene to Miocene, which align with the tectonic shift from the rifting to post-rift period, are essential for understanding the sedimentary filling in this area.

Provenance of the late Jurassic to Cenomanian sedimentary succession of the Araripe Basin (NE Brazil) and implication for the geodynamic evolution of Western Gondwana

The separation of Gondwana was controlled by preexisting Proterozoic structures and by the development of rift aborted basins, of which the Araripe Basin (NE Brazil) is one of the best examples. Previous studies have focused on the presence and provenance of Aptian–Albian shallow-marine incursions in the Araripe Basin but to date, little attention has been given to its paleodrainage evolution during sedimentation stages. Understanding the paleodrainage evolution is crucial for determining sediment sources and how topographic changes relate to the geodynamic development of the northern part of South America during the fragmentation of Gondwana, and this study investigates the provenance of Mesozoic rift and post-rift sedimentary rocks in the Araripe Basin using a multi-proxy dataset comprising major and trace element concentrations, Sm–Nd isotopic composition, and detrital zircon U–Pb ages. The low Eu/Eu* ratios (0.3–0.9) and high Th/Sc ratios (>0.64) in the most of analyzed samples suggest a felsic and silicic source. The εNd(0) values (−12.3 to −23.7) and TDM ages (1.68 to 2.55 Ga) of analyzed samples suggest overall ancient crustal sources. The presence of oval and elongated zircon grains suggests a major contribution of first-cycle transport sediments. The presence of 2.3–1.8 Ga and 0.63–0.58 Ga U–Pb zircon ages further indicates the dominant contribution of the Borborema Province influenced by the Brasiliano cycle (650–520 Ma). The low contribution of Tonian (∼940 Ma) zircons to the U–Pb zircon age distribution of the rift-beginning stage sample associated with published paleocurrent direction suggests sources located in the northern and northwestern terranes of the Borborema Province. The increase of Tonian (0.9–1.0 Ga) zircon grains during the rift stage suggests a provenance change with a dominant source in the eastern terranes during the rift stage. During the post-rift I stage, the decrease of 1.2–0.72 Ga zircon ages suggests a change in the source areas, with the paleodrainage coming from northern Borborema Province, similar to that of the rift-beginning stage. The samples of the post-rift II stage exhibit dominant contributions of Paleoproterozoic and Neoproterozoic U–Pb ages related to the Albian to Cenomanian uplift of the Borborema plateau during the opening of Equatorial Atlantic Ocean. Together with previous published studies, these findings highlight the significant role played by the post-rift continental uplift to the paleodrainage of the northern part of South America.

A-type tonian granite in the northwest of the gavião block: Record of within-plate magmatism precursor to the continental rifting of the São Francisco paleoplate?

The Early Tonian period in the São Francisco Craton represents the development of an intracontinental rift across the northern and central Espinhaço regions, playing a crucial role in understanding the tectonic evolution of the Neoproterozoic Period within this craton and its adjacent orogens. This rift is associated with the breakup of the São Francisco paleoplate, marked by the formation of several rifts, some of which were aborted (e.g. Santo Onofre Rift), and magmatism associated. Field investigations, coupled with petrographic, lithogeochemical, and U–Pb geochronological data of the Serra do Meio Suite, elucidate key characteristics and offer significant insights into the Tonian tectonic evolution of the São Francisco Craton and its relationship with Santo Onofre Rift. The suite comprises metagranitoids exhibiting a mineralogical composition spanning from alkali-feldspar granites to granites and its petrogenesis and tectonic characteristics reveal an alkaline to calc-alkalic signature, exhibiting extreme ferroan geochemistry and indications of moderate to high oxygen fugacity. Pressure estimations suggest low-pressure conditions during magma crystallization, implying shallow crustal emplacement. The suite's evolution involves complex petrogenetic processes, likely influenced by fractional crystallization and contamination by country rocks from a quartz-feldspathic crustal source, as well as a possible contribution from juvenile tholeiitic mantle sources associated with rift environments, showcasing a signature typical of A1-type granite. The U–Pb SHRIMP age, determined as 930 ± 2 Ma (MSWD = 0.34), is interpreted as the crystallization age of the rock and allows us to connect it to the opening of the Santo Onofre-Macaúbas Rift in the São Francisco Craton.

Kinematic reconstruction of the Jurassic intraplate rift deformation in the Northern Carnarvon Basin, Australia

Intraplate rift basins, like the inboard sub-basins of the Northern Carnarvon Basin (NCB), host rich energy resources, but their complex geological histories complicate exploration efforts. The paleo-deformation that formed these intraplate rifts also controlled their resource systems distribution. Hence, understanding their complex kinematic and tectonostratigraphic histories can optimise exploration and targeting. However, without forming oceanic seafloor, these regions lack adjacent magnetic seafloor isochrons to constrain paleo-positions of rift margins, rendering kinematic reconstruction nearly impossible. We present a method that constrains the spatiotemporal paleo-distribution of intraplate rift-related deformation and precisely locates paleo-positions of rift margins using time-dependent backstripped subsidence rasters. This method correlates areas with high subsidence rates with rifted regions within extension settings, and we apply it to reconstruct the kinematic evolution of the NCB sub-basin rift.Reconstruction results indicate that the Late Triassic – Early Jurassic extension initiated rifting in the nearshore parts of the NCB, creating Exmouth and Barrow sub-basin grabens at 8 mm/yr maximum rift widening rates. Rifting shifted northeastwards into the Dampier and Beagle regions from Mid Jurassic to Early Cretaceous. Rifting rates in the nearshore regions slowed at ∼155 Ma, coinciding with the Argoland – Australia separation and seafloor spreading within the outboard Argo region. The rates increased again at ∼145 Ma during the Tithonian extension and then decreased significantly at ∼120 Ma during the seafloor spreading in the Cuvier and Gascoyne regions. The temporal correlation between Gondwana dispersal events and the nearshore sub-basin rift evolution suggests that the sub-basins were part of a broader deformation zone across the margin. However, strain localised and triggered breakup and seafloor spreading within the outboard Argo, Gascoyne, and Cuvier regions. Such breakups released extension forces and caused rift cessation in the nearshore NCB sub-basins.

Facies analysis and depositional model of the Midcontinent Rift System in Kansas, USA

AbstractThe Midcontinent Rift System of North America is one of the oldest continental rifts but rifting ceased before continental breakup. The southern segment of the Midcontinent Rift System lies in Kansas, USA, where the stratigraphic succession and rift evolution are largely unknown. This study analysed the rift basin infill in this part of the Midcontinent Rift System to propose a depositional model. The Precambrian rift succession was described in discontinuous cores drilled in the Texaco Noel Poersch#1 well in Washington County. Sixteen lithofacies were identified and grouped into four different facies associations (fluvial, aeolian, lacustrine and alluvial fan). Overall, the studied succession comprises continental deposits accumulated dominantly in alluvial and aeolian settings, with the intermittent development of lacustrine systems. The proposed depositional models for the available core intervals indicate cyclic patterns of overfilled and underfilled phases within the rift basin. These changes in the accommodation‐to‐supply ratio were controlled by tectonism and probably modulated by climate during evolution in the syn‐rift phase. This study advances our understanding of variations across the Midcontinent Rift System.

Influence of mantle plume on continental rift evolution: A case study of the East African rift system

Mantle plume is an essential component of the mantle convection system, and its influence on the geodynamics of continental rifts is of great significance for understanding the crust–mantle interaction. The East African Rift System, as the largest continental rift in the Cenozoic and in the initial stage, provides an excellent option for studying the interaction between the mantle plume and the continental crust. Based on the data such as GPS, seismic tomography, and global crustal model, a viscoelastic-plastic 2D thermodynamic numerical model is established to reconstruct the evolution of the Afar depression, Ethiopian Rift, and Kenyan Rift. By comparing the differences between the models of the Afar depression, Ethiopian Rift, and Kenyan Rift, the relationship between the mantle plume and pre-existing structures and their influence on the evolution of continental rifts are discussed. The results show that the mantle plume can increase the depth of the rift faults, concentrate the distribution of the faults, and strengthen the control of main faults on the rifts, allowing the possibility of narrow rifts. Pre-existing structures control the fault styles and symmetry of the rifts and also the morphology of the mantle plume.

Structural geology and deformation analysis in the Búzios-Itapu area, Santos Basin — offshore Brazil

Despite their proximity, the Búzios and Itapu oil fields in the Santos Basin have different structural configurations. The study of the deformation pattern of the area and the relationship of the observed structures with the tectonic evolution of the basement is important to understand the geologic setting and evolution of the studied oil fields. In this work, a 3D PSDM seismic volume calibrated with well data was used to characterize the different types of structures, the distinct structural domains that occur in the Pre-Salt of the Búzios and Itapu fields, and the relationship between the basement trends and the structures in the sedimentary section. The Búzios field is formed by a series of half-grabens and horsts elongated in the NE-SW and NW-SE trends. Over the structural highs, a wide carbonate platform was developed. The Itapu field is a structural high related to a single elongated half-graben with a N-S main trend. The main structural pattern in the area is defined by normal faults that indicate an extensional process, typical of rift evolution. However, there are several structures that show indication of oblique-like deformation with strike-slip displacements, throughout the studied area. A very important issue is the discussion of the hierarchy of the observed structures, both rift extensional structures, and the oblique-like ones.