Reply to discussion on “From Pan-African transpression to Cadomian transtension at the West African margin: New U-Pb zircon ages from the Eastern Saghro Inlier (Anti-Atlas, Morocco)” by Ikenne et al. 2020 (GSL-SP, 503, 209-233)

2021 ◽  
pp. jgs2021-034
Author(s):  
Ezzoura Errami ◽  
Ulf Linnemann ◽  
Jamal El Kabouri ◽  
Mandy Hofmann ◽  
Andreas Gärtner ◽  
...  
Keyword(s):  
West African ◽  
Ultramafic Rocks ◽  
Geodynamic Evolution ◽  
The West ◽  
West African Craton ◽  
Zircon Age ◽  
Pan African ◽  
Stratigraphic Position ◽  
Age Constraints ◽  
Early Neoproterozoic

The comment of Ikenne et al. concerns recently described U-Pb baddeleyite ages, around 1.71 and 1.65 Ga, obtained on intrusive sills and dykes in the Taghdout-Lkest Group in the SW domain of the Anti-Atlas (AA). These authors suggest an independent geodynamic evolution of the eastern and western domains of the Anti-Atlas prior to the Ediacaran period. Furthermore, they state that we do not take this magmatic event into account when interpreting our data. We like to emphasize that this is beyond the scope of our paper and does not affect our interpretation of the AA evolution during the deposition of the Ediacaran sedimentary successions (Saghro, Mgouna, and Ouarzazate goups). We agree with the comment that we did not distinguish the Taghdout-Lkest from the Bleida-Tachdamt groups and now we separate them in the revised figure 2. The different geodynamic evolution of the SW and NE Anti-Atlas domains in pre-Ediacaran times sensu Ikenne et al., is not consistent with abundant inherited Paleoproterozoic zircon detritus and Nd model ages (0.80-1.82 Ga) from the northeastern Anti-Atlas and the Meseta. There is no doubt about Late Paleoproterozoic baddeleyite ages, but they do not have an analogue in the zircon age record of the West African Craton, which is expected from ultramafic rocks with few zircon grains. However, they locally allow assuming a Late Paleoproterozoic deposition of the lower Taghdout-Lkest Group. Any age constraints for the upper parts of this group are lacking, thus allowing a hypothetic deposition between ca. 1.65 Ga and 0.83 Ga (the assumed age of initial Bleida-Tachdamt Group deposition). Therefore, it is very important to close the gap in detailed stratigraphic studies that would allow differentiating between the different Late Paleoproterozoic and Early Neoproterozoic events including the stratigraphic position of the upper Taghdout-Lkest Group and Bleida-Tachdamt group.

Discussion on “From Pan-African transpression to Cadomian transtension at the West African margin: New U-Pb zircon ages from the Eastern Saghro Inlier (Anti-Atlas, Morocco)” by Errami et al. 2020 (GSL-SP 503, 209-233)

2021 ◽  
pp. jgs2020-206
Author(s):  
M. Ikenne ◽  
A. Bekker ◽  
R.E. Ernst ◽  
N. Youbi ◽  
A. Ait Lahna ◽  
...  
Keyword(s):  
West African ◽  
Age Difference ◽  
Geodynamic Evolution ◽  
The West ◽  
Mafic Magmatism ◽  
Tectonic Events ◽  
Pan African ◽  
Age Constraints ◽  
Published Paper ◽  
Mixed Carbonate

Recent U-Pb igneous ages obtained in the SW Domain of the Anti-Atlas are not consistent with the model proposed in the recently published paper by Errami et al. (2020). The formations of the Taghdoute and Lkest groups in the SW Domain, also known as the “limestones and quartzites” series, were previously considered to have a Cryogenian age due to similarities with the series of limestone and quartzite of the Tachddamt Bleida Formation in the Bou-Azzer Inlier located in the NE Domain of the Anti-Atlas. However, recent U-Pb ages on zircon and baddeleyite of 1.71-1.65 Ga obtained on intrusive sills and dykes in the Taghdoute and Lkest groups, constrain this sedimentary series of the SW Domain to be approximately 1 Ga older than previously thought. Absence of Paleoproterozoic series in the NE Domain combined with the available age constraints suggests that it has a Pan-African age. However, recent 1.71-1.65 Ga ages of mafic magmatism in the SW Domain conflict with the previously inferred Tonian to Cryogenian age for the mixed carbonate-siliciclastic series of the Taghdoute and Lkest groups and raises uncertainty about the age of tectonic events previously attributed to the Pan-African Orogeny in this part of the Anti-Atlas. Furthermore, the age difference between the NE and SW domains of the Anti-Atlas suggests their independent geodynamic evolution before the Ediacaran Period.

About this title - Mineralization and Sustainable Development in the West African Craton: From Field Observations to Modelling

10.1144/sp502 ◽  
2021 ◽  
Vol 502 (1) ◽  
pp. NP-NP
Author(s):  
T. Aïfa
Keyword(s):  
Sustainable Development ◽  
West African ◽  
Geodynamic Evolution ◽  
The West ◽  
Mineral Research ◽  
West African Craton ◽  
Origin And Evolution ◽  
Pan African ◽  
New Knowledge ◽  
Modelling Techniques

This Special Publication combines results obtained by interdisciplinary groups from numerous academic institutions working on Paleoproterozoic formations to decipher the origins of the main mineralization resources in the West African Craton (WAC) and their impacts on African economic development. Structural, geophysical, sedimentological, stratigraphical, geochemical, petrophysical and mineralogical analyses have been used to highlight the complexities involved in mineralization emplacement and its origin and evolution within the WAC. Fourteen articles contribute to new knowledge in mineral research. They show that the geodynamic evolution of the WAC is complex from one area to another: it involves subduction, collision and obduction during several deformation phases ranging from Birimian (2.3–2.0 Ga) to Pan-African (650–450 Ma) events. Various modelling techniques, when integrated, help in understanding the mechanisms of mineralization emplacement, some of which are still a matter of debate. The challenge for further studies is mitigation for sustainable development that can be appropriately used to minimize such damage.

Interprétation géodynamique du domaine pan-africain (Précambrien terminal) de l'Anti-Atlas (Maroc) à partir de données géologiques et géochronologiques

1980 ◽  
Vol 17 (1) ◽  
pp. 142-155 ◽  
Author(s):  
M. Leblanc ◽  
J. R. Lancelot
Keyword(s):  
Continental Margin ◽  
Active Continental Margin ◽  
West African ◽  
The Other ◽  
Geochronological Data ◽  
Geodynamic Evolution ◽  
The West ◽  
West African Craton ◽  
Northern Margin ◽  
Pan African

U–Pb and Rb–Sr ages performed in the Anti-Atlas (Morocco), especially in Bou Azzer area, demonstrate a Pan-African orogeny (680–570 Ma), along the northern margin of the West African craton (2000 Ma). Geological and geochronological data allow the reconstitution of a coherent succession of events of Pan-African ages. The geodynamic evolution of this domain comprises a stage of oceanic opening (ophiolites) followed with a stage of closure: obduction of the ophiolites on the craton, then subduction under an active continental margin. This segment of the Pan-African belt can be correlated with the other parts of the belt, located on the eastern margin of the West African craton.

Early Neoproterozoic rift-related magmatism in the Anti-Atlas margin of the West African craton, Morocco

2014 ◽  
Vol 255 ◽  
pp. 433-442 ◽  
Author(s):  
J. Javier Álvaro ◽  
André Pouclet ◽  
Hassan Ezzouhairi ◽  
Abderrahmane Soulaimani ◽  
El Hafid Bouougri ◽  
...  
Keyword(s):  
West African ◽  
The West ◽  
West African Craton ◽  
Early Neoproterozoic

Where are the Eburnian–Transamazonian collisional belts?

1990 ◽  
Vol 27 (10) ◽  
pp. 1382-1393 ◽  
Author(s):  
Jean Michel Bertrand ◽  
Emmanuel Ferraz Jardim de Sá
Keyword(s):  
West African ◽  
High Grade ◽  
The West ◽  
West African Craton ◽  
Early Proterozoic ◽  
Late Proterozoic ◽  
Nappe Tectonics ◽  
Pan African ◽  
Orogenic Belts ◽  
Lower Crustal

The reconstruction of Early Proterozoic crustal evolution and geodynamic environments, in Africa and South America, is incomplete if cratonic areas alone are studied. If the presence of high-grade gneisses is considered as a first clue to past collisional behaviour, 2 Ga high-grade gneisses are more abundant within the Pan-African–Brasiliano mobile belts than in the intervening pre-Late Proterozoic cratons. The West African craton and the Guiana–Amazonia craton consist of relatively small Archaean nuclei and widespread low- to medium-grade volcanic and volcanoclastic formations intruded by Early Proterozoic granites. By contrast, 2 Ga granulitic assemblages and (or) nappes and syntectonic granites are known in several areas within the Pan-African–Brasiliano belts of Hoggar–Iforas–Air, Nigeria, Cameroon, and northeast Brazil. Nappe tectonics have been also described in the Congo–Chaillu craton, and Early Proterozoic reworking of older granulites may have occurred in the São Francisco craton. The location of the Pan-African–Brasiliano orogenic belts is probably controlled by preexisting major structures inherited from the Early Proterozoic. High-grade, lower crustal assemblages 2 Ga old have been uplifted or overthrust and now form polycyclic domains in these younger orogenic belts, though rarely in the cratons themselves. The Congo–Chaillu and perhaps the São Francisco craton are exceptional in showing controversial evidence of collisional Eburnian–Transamazonian assemblages undisturbed during Late Proterozoic time.

scholarly journals Early Neoproterozoic oxygenation dynamics along the northern margin of the West African Craton, Anti-Atlas Mountains, Morocco

2021 ◽  
pp. 120404
Author(s):  
Ernest Chi Fru ◽  
Olabode Bankole ◽  
Ibtissam Chraiki ◽  
Nassrddine Youbi ◽  
Marc-Alban Millet ◽  
...  
Keyword(s):  
West African ◽  
The West ◽  
West African Craton ◽  
Northern Margin ◽  
Atlas Mountains ◽  
Early Neoproterozoic
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