scholarly journals Bien Dong seafloor spreading and its influence to formation & development of sedimentary basins

2014 ◽  
Vol 17 (3) ◽  
pp. 132-138
Author(s):  
Hung Nguyen Manh ◽  
Tieng Hoang Dinh
Keyword(s):  
Continental Crust ◽  
Oceanic Crust ◽  
Sedimentary Basins ◽  
Seafloor Spreading ◽  
Fault System ◽  
Basalt Magma ◽  
Deep Fault ◽  
Thermal Anomalies ◽  
South West ◽  
Favorable Conditions

The paper presents the characteristics of Bien Dong seafloor spreading which including two parts: The Eastern part is quite large, in which developed by Eastern- Western orientation (spreading on N-S). The Southern- Western part gradually changed its orientation from E-W into East- North and in to South- West at the end (spreading SE- NW). There are two main dynamic resources created the spreading and deformation: The appearance of thermal abnormality by mantle plume occurred 36 M.a. until 14 M.a. The Eastern thermal anomalies continued to develop follow this orientation. In the SW- part the thermal anomalies changed it orientation from E-W into NE- SW 26 M.a and gradually developing toward S-W. Since 14 M.a, both two these trends been stopped, began to cooling and shrinkage. The abnormal existence caused pinchout and rifting the continental crust in Bien Dong Center and generating new oceanic crust as well. The uplift and variation of thermal abnormality (basalt magma) raised up the favorable conditions to forming, developing and varying the axis of Bien Dong spreading seafloor. The all above synthetic activities created favorable conditions for generation and development a series of deep fault systems with E-W direction in Eastern part and NE- SW direction in Southern-Western direction in remain part, and created and evolved the sedimentary basins in margins of Bien Dong with along the main deep fault system.

Crustal contamination and hybridization of an embryonic oceanic crust during the Red Sea rifting: An example from the Tihama Asir igneous complex, Saudi Arabia

2021 ◽  
Author(s):  
Valentin Basch ◽  
Alessio Sanfilippo ◽  
Luigi Vigliotti ◽  
Antonio Langone ◽  
Najeeb Rasul ◽  
...  
Keyword(s):  
Continental Crust ◽  
Oceanic Crust ◽  
Red Sea ◽  
Crustal Contamination ◽  
Seafloor Spreading ◽  
Rift System ◽  
Continental Rifting ◽  
Igneous Complex ◽  
Early Stages ◽  
Incompatible Elements

<p>The Red Sea rift system represents the best case study of the rift-to-drift history, i.e., the transition from a continental to an oceanic rift and the formation of passive margins. Although the onset of seafloor spreading has been constrained by geophysical observations to 5 Ma in the southern Red Sea, recent studies have suggested that MORB-type melts were intruded within the extended continental crust already during the early stages of rifting. We present here a petro-geochemical investigation of gabbroic bodies and associated basaltic intrusions from the Tihama Asir igneous complex, which formed as part of the intense magmatism that occurred during early Red Sea continental rifting. The most primitive olivine gabbros present modal, bulk and mineral compositions consistent with formation from MORB-type parental melts, but more evolved gabbros and oxide gabbros show saturation of phlogopite and define a geochemical evolution that progressively diverges from that of lower oceanic crust at mid-ocean ridges. Indeed, the Tihama Asir evolved gabbros are characterized by enrichments in LREE and highly incompatible elements (Rb, Ba, U, Th, Nb, Sr, K), suggesting hybridization of a MORB-type parental melt through a process of progressive assimilation of continental crust during the emplacement of gabbroic bodies. Additionally, the gabbros are associated with basaltic dike swarms intruded into the extending continental crust. The basalts show enrichments in LREE and highly incompatible elements similar to the gabbros, suggesting that they formed from melts extracted from the hybridized gabbroic crystal mush. This indicates that the Red Sea oceanization started before the onset of seafloor spreading, and that the cold continental crust was partially assimilated and replaced by hot gabbroic bodies since the early stages of continental rifting.</p>

New model of two-stage seafloor spreading in the Eurasian basin (Arctic Ocean); insights from the analysis of the sedimentary basin architecture

2020 ◽  
Author(s):  
Pavel Rekant ◽  
Oleg Petrov
Keyword(s):  
Continental Crust ◽  
Magnetic Anomaly ◽  
Rift Valley ◽  
Sedimentary Basins ◽  
Seafloor Spreading ◽  
The Arctic ◽  
Two Stage ◽  
Gakkel Ridge ◽  
Sedimentary Architecture ◽  
Eurasian Basin

<p>Base on thorough interpretation of Russian seismic reflection data the sedimentary architecture of Amundsen and Nansen basins was studied. Accordingly, we infer four development stages of the Eurasian Basin (EB) sedimentary system, caused by tectonic evolution of the region.</p><p><strong>Continental break-up stage I</strong> ~120-56 MA leads to formation of 120-130 km wide synrift basins both in the Eastern Amundsen and in the Western Nansen basins. Both basins were floored by extremely extended continental crust. Therefore, the hypothesized continent-ocean boundary (COB) should be placed at the seaward edges of synrift portions of Amundsen and Nansen basins, roughly along the magnetic anomaly #20.</p><p><strong>Spreading</strong> <strong>stage II</strong> (56-34 MA) was characterized by seafloor spreading in the EB as low as 8 mm/year, which was accompanied by expansion of the Amundsen and Nansen sedimentary basins up to their current sizes. The successive expansion of the sedimentary basins which is characteristic of the seafloor spreading basin, was revealed from the architecture of only this sequence, neither underlying nor overlapping. We propose the formation of a Gakkel Ridge rift valley and its infilling with thick sediments sequence during this stage.</p><p><strong>Synoceanic</strong> <strong>stage III</strong> (34-~3 MA) was resulted in the accumulation of the undisturbed Oligocene-Quaternary sediment sequence all over the entire EB. If the non-tectonized architecture of this sequence indicates a calm tectonic regime for the most of the Oligocene-Miocene, the existence of the sediment veneer all over the entire EB proves that sedimentation basin and consequently the oceanic crust domain of modern size were already formed by the beginning of Oligocene.</p><p><strong>Re-spreading stage IV (~3-0 MA)</strong> is characterized by the resumption of seafloor spreading in the Gakkel Ridge axial zone by propagation of the oceanic rift from Norwegian-Greenland basin toward the east.  </p><p>The proposed model of two-stage seafloor spreading in the EB allows us to explain most of the geological issues in this region and is of perfect relation to the known tectonic events along the Arctic periphery.</p><p>In particular: (1) thick sediments sequence in the Eastern and Central (e.g.  at 94°E by Rekant & Gusev, 2016)  Gakkel Ridge rift valley could be explained by the Eocene age of the rift valley, (2) recent spreading resumption could be considered as the cause of the unpredictable high both the hydrothermal activity and volcanism at the Western Gakkel Ridge, (3) the consolidated sand- and siltstones, dredged from the seamount scarp in the middle part of Amundsen Basin (Gaedicke et al., 2019), which thought to be fragments of Mesozoic continental crust, confirm the suggested COB position along magnetic anomaly No.20, (4) the eastward propagation of the ocean rifting along the Gakkel Ridge leads to apparent change of the accentuated high relief morphology of the Western Gakkel Ridge to a smoother ridge morphology of the Eastern Gakkel Ridge as well as to defocusing seismicity at the Eurasia Basin– Laptev Sea transition.</p><p> </p>

scholarly journals Seismic investigation of an active ocean–continent transform margin: the interaction between the Swan Islands Fault Zone and the ultraslow-spreading Mid-Cayman Spreading Centre

2019 ◽  
Vol 219 (1) ◽  
pp. 159-184 ◽  
Author(s):  
C Peirce ◽  
A H Robinson ◽  
A M Campbell ◽  
M J Funnell ◽  
I Grevemeyer ◽  
...  
Keyword(s):  
Continental Crust ◽  
Oceanic Crust ◽  
Fault Zone ◽  
Lower Crust ◽  
P Wave ◽  
Fault System ◽  
Transform Fault ◽  
Apparent Lack ◽  
The North ◽  
Transform Margin

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

Recent and active deformation in the North Evia domain, a diffuse plate boundary between Eurasia and Aegean plates in the Western termination of the North Anatolian Fault. 

2021 ◽  
Author(s):  
Fabien Caroir ◽  
Frank Chanier ◽  
Virginie Gaullier ◽  
Julien Bailleul ◽  
Agnès Maillard-Lenoir ◽  
...  
Keyword(s):  
Fault Zone ◽  
Plate Boundary ◽  
Fault Zones ◽  
North Anatolian Fault ◽  
Fault System ◽  
Eurasian Plate ◽  
Slip Rates ◽  
The North ◽  
South West ◽  
North Aegean

<p>The Anatolia-Aegean microplate is currently extruding toward the South and the South-West. This extrusion is classically attributed to the southward retreat of the Aegean subduction zone together with the northward displacement of the Arabian plate. The displacement of Aegean-Anatolian block relative to Eurasia is accommodated by dextral motion along the North Anatolian Fault (NAF), with current slip rates of about 20 mm/yr. The NAF is propagating westward within the North Aegean domain where it gets separated into two main branches, one of them bordering the North Aegean Trough (NAT). This particular context is responsible for dextral and normal stress regimes between the Aegean plate and the Eurasian plate. South-West of the NAT, there is no identified major faults in the continuity of the NAF major branch and the plate boundary deformation is apparently distributed within a wide domain. This area is characterised by slip rates of 20 to 25 mm/yr relative to Eurasian plate but also by clockwise rotation of about 10° since ca 4 Myr. It constitutes a major extensional area involving three large rift basins: the Corinth Gulf, the Almiros Basin and the Sperchios-North Evia Gulf. The latter develops in the axis of the western termination of the NAT, and is therefore a key area to understand the present-day dynamics and the evolution of deformation within this diffuse plate boundary area.</p><p>Our study is mainly based on new structural data from field analysis and from very high resolution seismic reflexion profiles (Sparker 50-300 Joules) acquired during the WATER survey in July-August 2017 onboard the R/V “Téthys II”, but also on existing data on recent to active tectonics (i.e. earthquakes distribution, focal mechanisms, GPS data, etc.). The results from our new marine data emphasize the structural organisation and the evolution of the deformation within the North Evia region, SW of the NAT.</p><p>The combination of our structural analysis (offshore and onshore data) with available data on active/recent deformation led us to define several structural domains within the North Evia region, at the western termination of the North Anatolian Fault. The North Evia Gulf shows four main fault zones, among them the Central Basin Fault Zone (CBFZ) which is obliquely cross-cutting the rift basin and represents the continuity of the onshore Kamena Vourla - Arkitsa Fault System (KVAFS). Other major fault zones, such as the Aedipsos Politika Fault System (APFS) and the Melouna Fault Zone (MFZ) played an important role in the rift initiation but evolved recently with a left-lateral strike-slip motion. Moreover, our seismic dataset allowed to identify several faults in the Skopelos Basin including a large NW-dipping fault which affects the bathymetry and shows an important total vertical offset (>300m). Finally, we propose an update of the deformation pattern in the North Evia region including two lineaments with dextral motion that extend southwestward the North Anatolian Fault system into the Oreoi Channel and the Skopelos Basin. Moreover, the North Evia Gulf domain is dominated by active N-S extension and sinistral reactivation of former large normal faults.</p>

French and Belgian Uplands

2005 ◽  
Author(s):  
Bernard Etlicher
Keyword(s):  
Continental Crust ◽  
Rift Valley ◽  
Sedimentary Basins ◽  
Shear Zones ◽  
Metamorphic Complex ◽  
French Massif Central ◽  
Massif Central ◽  
Montagne Noire ◽  
Oceanic And Continental Crust ◽  
Moderate Elevation

The French Uplands were built by the Hercynian orogenesis. The French Massif Central occupies one-sixth of the area of France and shows various landscapes. It is the highest upland, 1,886 m at the Sancy, and the most complex. The Vosges massif is a small massif, quite similar to the Schwarzwald in Germany, from which it is separated by the Rhine Rift Valley. Near the border of France, Belgium, and Germany, the Ardennes upland has a very moderate elevation. The largest part of this massif lies in Belgium. Though Brittany is partly made up of igneous and metamorphic rocks, it cannot be truly considered as an upland; in the main parts of Brittany, altitudes are lower than in the Parisian basin. Similarities of the landscape in the French and Belgian Uplands derive from two major events: the Oligocene rifting event and the Alpine tectonic phase. The Vosges and the Massif Central are located on the collision zone of the Variscan orogen. In contrast, the Ardennes is in a marginal position where primary sediments cover the igneous basement. Four main periods are defined during the Hercynian orogenesis (Bard et al. 1980; Autran 1984; Ledru et al. 1989; Faure et al. 1997). The early Variscan period corresponds to a subduction of oceanic and continental crust and a highpressure metamorphism (450–400 Ma) The medio- Variscan period corresponds to a continent–continent collision of the chain (400–340 Ma). Metamorphism under middle pressure conditions took place and controlled the formation of many granite plutons: e.g. red granites (granites rouges), porphyroid granite, and granodiorite incorporated in a metamorphic complex basement of various rocks. The neo-Variscan period (340–320 Ma) is characterized by a strong folding event: transcurrent shear zones affected the units of the previous periods and the first sedimentary basins appeared. At the end of this period, late-Variscan (330–280 Ma), autochthonous granites crystallized under low-pressure conditions related to a post-collision thinning of the crust. Velay and Montagne Noire granites are the main massifs generated by this event. Sediment deposition in tectonic basins during Carboniferous and Permian times occurred in the Massif Central and the Vosges: facies are sandstone (Vosges), shale, coal, and sandstone in several Stephanian basins of the Massif Central, with red shale and clay ‘Rougier’ in the south-western part of the Massif Central.

scholarly journals Towards understanding how surface life can affect interior geological processes: a non-equilibrium thermodynamics approach

2011 ◽  
Vol 2 (1) ◽  
pp. 139-160 ◽  
Author(s):  
J. G. Dyke ◽  
F. Gans ◽  
A. Kleidon
Keyword(s):  
Continental Crust ◽  
Oceanic Crust ◽  
Mantle Convection ◽  
Dynamical Models ◽  
Geological Processes ◽  
The Earth ◽  
Uplift And Erosion ◽  
Life On Earth ◽  
Mantle Temperature ◽  
Non Equilibrium

Abstract. Life has significantly altered the Earth's atmosphere, oceans and crust. To what extent has it also affected interior geological processes? To address this question, three models of geological processes are formulated: mantle convection, continental crust uplift and erosion and oceanic crust recycling. These processes are characterised as non-equilibrium thermodynamic systems. Their states of disequilibrium are maintained by the power generated from the dissipation of energy from the interior of the Earth. Altering the thickness of continental crust via weathering and erosion affects the upper mantle temperature which leads to changes in rates of oceanic crust recycling and consequently rates of outgassing of carbon dioxide into the atmosphere. Estimates for the power generated by various elements in the Earth system are shown. This includes, inter alia, surface life generation of 264 TW of power, much greater than those of geological processes such as mantle convection at 12 TW. This high power results from life's ability to harvest energy directly from the sun. Life need only utilise a small fraction of the generated free chemical energy for geochemical transformations at the surface, such as affecting rates of weathering and erosion of continental rocks, in order to affect interior, geological processes. Consequently when assessing the effects of life on Earth, and potentially any planet with a significant biosphere, dynamical models may be required that better capture the coupled nature of biologically-mediated surface and interior processes.

General discussion

1987 ◽  
Vol 321 (1557) ◽  
pp. 271-273
Keyword(s):  
Mathematical Models ◽  
Continental Crust ◽  
Oceanic Crust ◽  
Continuous Medium ◽  
The Urals ◽  
The Earth ◽  
Scandinavian Caledonides ◽  
Fold Belts ◽  
Normal Thickness

E. V. Artyushkov ( Institute of Physics of the Earth, Moscow, U.S.S.R .). Shortening of the crust has been modelled by compression of a continuous medium. It has also been supposed that compression can start in continental crust of normal thickness. Mathematical models of the same type have recently been used by some other authors. It should be noted that an intense shortening of the crust in fold belts never occurred in such a way. In the main Phanerozoic fold belts (the Urals, Appalachians, Scandinavian Caledonides, the Alpine and Verkhoyansk belts, and others) no era tonic block with a normal continental crust and lithosphere was shortened (Artyushkov & Baer 1983, 1984, 1986). An intense compression took place only in deep basins on oceanic or continental crust. Most oceanic crust disappeared from the surface in the process of subduction. Now the fold belts are mainly built up of a strongly compressed crust of deep basins on continental crust. How can it be proven that this crust was really thin?

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