scholarly journals Origin of ocean island basalts in the West African passive margin without mantle plume involvement

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Iyasu Getachew Belay ◽  
Ryoji Tanaka ◽  
Hiroshi Kitagawa ◽  
Katsura Kobayashi ◽  
Eizo Nakamura
Keyword(s):  
Mantle Plume ◽  
West African ◽  
Passive Margin ◽  
The West ◽  
Ocean Island ◽  
Ocean Island Basalts

The Equatorial Atlantic Laboratory: sediment routing systems and lithosphere deformation

2020 ◽  
Author(s):  
Delphine Rouby ◽  
Dominique Chardon ◽  
Jing Ye ◽  
Flora Bajolet ◽  
Artiom Loparev ◽  
...  
Keyword(s):  
West African ◽  
Passive Margin ◽  
Rift System ◽  
Equatorial Atlantic ◽  
The West ◽  
Geological Time Scale ◽  
West African Craton ◽  
Continental Scale ◽  
Sediment Routing ◽  
Atlantic Margin

<p>We summarize the results of a 7 years study of the sediment routing systems of the West African Craton transporting its erosional products to the Central and Equatorial Atlantic passive margins at geological time scale. We used paleogeograhic maps to define the geodynamics framework of this routing system with in particular the propagation of the Equatorial Atlantic oblique rift separating the West African and Amazonian Cratons. We used sub-surface data to evaluate the evolution of lithosphere necking distribution along the conjugated African and South American margins of the rift system. We estimated the long-term denudation pattern at continental scale from low temperature thermochronology measures of samples from 3 transects perpendicular to the Atlantic margin. We used the exceptional preservation of geomorphologic markers to reconstruct the drainage system of the craton since 45 Ma, and estimate the associated denudation and exports of terrigeneous sediments to the Atlantic margin. Finally, we estimated the accumulation history in the passive margin basins and compare them with the estimated denudation histories from thermal histories and geomorphologic markers. We show that the modes of preservation of sedimentary export in the passive margin basins are highly variable in time (immediate post roft versus late post-rift) and space (transform/oblique versus divergent margin segments). We show that the present day drainage of the West African Craton as been stable since 30 Ma when it underwent a major reorganization driven by the growth of the relief associated with the Hoggar mantle plume. We show that accumulation in the passive margin basins fall within the same order of magnitude than denudation on the craton at the scale of the Meso-Cenozoic. This allows us to argue to the relevance of using the stratigraphic architecture of passive margin basins to estimate the denudation history of their continental domains.</p>

Detrital zircon sources in the Ordovician metasedimentary rocks of the Moroccan Meseta: Inferences for northern Gondwanan passive-margin paleogeography

2022 ◽  
Author(s):  
Cristina Accotto ◽  
David Martínez Poyatos ◽  
Antonio Azor ◽  
Cristina Talavera ◽  
Noreen Joyce Evans ◽  
...  
Keyword(s):  
Detrital Zircon ◽  
West African ◽  
Passive Margin ◽  
Variscan Orogeny ◽  
The West ◽  
West African Craton ◽  
Metasedimentary Rocks ◽  
Population Peak ◽  
A Minor ◽  
Detrital Zircon Ages

ABSTRACT Detrital zircon U-Pb geochronology has been widely used to constrain the pre-Carboniferous geography of the European and, to a lesser extent, the Moroccan Variscides. The latter have been generally considered as part of a long-lasting passive margin that characterized northern Gondwana from Ordovician to Devonian time, and was subsequently involved in the late Paleozoic Variscan orogeny. We report detrital zircon ages for three Early to Late Ordovician samples from the Beni Mellala inlier in the northeastern part of the Western Moroccan Meseta in order to discuss the temporal evolution of the sources of sediments in this region. The detrital zircon spectra of these samples, characterized by two main populations with mean ages of 630–610 Ma and 2170–2060 Ma, are typical of Cambrian–Devonian rocks from the Moroccan Variscides and confirm their link to the West African craton. A minor Stenian–Tonian population (peak at ca. 970 Ma) suggests the influence of a distant and intermittent NE African source (Sahara metacraton), which was probably interrupted after Ordovician time. Our data support previous interpretations of the Moroccan Meseta (and the entire northern Moroccan Variscides) as part of the northern Gondwana passive margin. The main sources of these sediments would have been the West African craton in the western regions of the passive margin (Moroc- can Meseta and central European Paleozoic massifs), and the Arabian-Nubian Shield and/or Sahara metacraton in the eastern areas (Libya, Egypt, Jordan, central and NW Iberian zones during Paleozoic time), where the 1.0 Ga detrital zircon population is persistent throughout the Ordovician–Devonian time span.

Tectonic influence on chemical composition of ocean island basalts in the West and South Pacific: Implication for a deep mantle origin

2011 ◽  
Vol 12 (7) ◽  
pp. n/a-n/a ◽  
Author(s):  
Gen Shimoda ◽  
Osamu Ishizuka ◽  
Katsuyuki Yamashita ◽  
Miwa Yoshitake ◽  
Masatsugu Ogasawara ◽  
...  
Keyword(s):  
Chemical Composition ◽  
South Pacific ◽  
The West ◽  
Ocean Island ◽  
Ocean Island Basalts ◽  
Mantle Origin ◽  
Deep Mantle

Along-Strike Variation of Halokinesis and Structural Inheritance Along the West African Salt Basin, South Atlantic

2020 ◽  
Author(s):  
Etienne Legeay ◽  
Jean-Claude Ringenbach ◽  
Jean-Paul Callot
Keyword(s):  
Cross Sections ◽  
Temporal Distribution ◽  
West African ◽  
Passive Margin ◽  
Distal Margin ◽  
Dynamic Topography ◽  
Regional Study ◽  
The West ◽  
Seismic Reflection Data ◽  
Break Up

<p>Along the West African margin from Gabon to southern Angola, the Loeme Aptian salt deposited during the late rift break-up process. Following the Atlantic opening, passive margin subsidence, large deltas and dynamic topography triggered and shape gravity tectonic systems. Evaporite deposition occurred during the break-up process, from the rupture of the continental crust to the spreading, thus providing an early inheritance (in term of thickness and geographic distribution of evaporites) for future salt tectonics, which is largely controlled by the genetic domain compartmentalizing the margin, namely the proximal margin, the neck basin, the distal margin, and the outer high and exhumed mantle. Classically, since the mid-90s the gravity gliding system pattern, with the usual triptych extension-translation-compression, has been over-applied along the West African margin. Recent data from Angola show mini-basins in a context of gravity spreading in addition to pure gliding-spreading roll-overs, rafts and diapirs, as well as mini basins developed during the early phase of evolution, and were later on squeezed by the gliding cell. We present here a regional study to compare major internal and external factors controlling halokinesis structural styles and we propose new maps and cross-sections up to 300 km long from onshore to ultra-deep offshore, to describe the main domains and styles across the Gabon, Lower Congo, Kwanza, Benguela and Namibe sub-basins. This work is based on an extensive 2D and 3D seismic reflection data, wells and internal reports. Margin scale cartographic compilation of both pre- and post-salt tectono-sedimentary trends provide elements to constrain both geometries and kinematics. This study documents the spatial and temporal distribution of both the inherited salt controlled basins (i.e. minibasins, salt ridges, etc.) as well as the superimposed gravitational systems, their characteristics and drivers (e.g. gliding, spreading), and by linking them to the genetic domains of the margin to highlight their various roles.</p>

Variscan deformation at the northern border of the West African Craton, eastern Anti-Atlas, Morocco: compression of a mosaic of tilted blocks

2007 ◽  
Vol 178 (5) ◽  
pp. 343-352 ◽  
Author(s):  
Youssef Raddi ◽  
Lahssen Baidder ◽  
Mohamed Tahiri ◽  
André Michard
Keyword(s):  
Regional Scale ◽  
West African ◽  
Passive Margin ◽  
Fold Belt ◽  
The West ◽  
West African Craton ◽  
Margin Setting ◽  
The North ◽  
Atlas Mountains ◽  
Northern Border

Abstract North of the Saharan cratonic domain, the Anti-Atlas mountains correspond to the foreland, external fold belt of the Variscan orogen which extends in the Meseta block to the north, and Mauritanides to the southwest. The Anti-Atlas was uplifted during the Mesozoic-Cenozoic, and display several basement culminations (“boutonnières”) amidst the folded Palaeozoic cover. Recent studies in western Anti-Atlas emphasized the basement implication in the shortening process (thick skinned structure). Hereafter we investigate the cover-basement relations in eastern Anti-Atlas south of the Ougnat culmination, based on mapping at scale 1:50,000. The Palaeozoic sequence is much thinner than in the west, and the décollement levels are less important. Flexural slip folds are concentrated along the faults (en échelon folds) and within some rhombic domains crushed between major faults (e.g. Angal-Gherghiz Lozenge), whereas other areas are monoclinal. The main shortening direction deduced from the fold axes trend is directed ~N045°E as in the Ougarta range further to SE. At a regional scale, this shortening direction interferes with a N-S trending one. A sketch map of the top of the basement makes visible a mosaic of S- to SE-ward tilted blocks. The faults between these blocks are inherited from paleofaults which formed during extensional events during the Cambrian, late Ordovician, and (mainly) Middle-Late Devonian. The paleofault array is indicative of a proximal passive margin setting at the northern border of the metacratonic domain. The fault inversion and their dominant strike-slip throw occurred during a late Variscan (Stephanian-Permian) compression event, postdating the NNW-SSE collision of the Meseta block.

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