Structure and U/Pb geochronology of Central Hoggar (Algeria): A reappraisal of its Pan‐African evolution

Abstract

Discovery of large‐scale deep‐seated thrusts in Central Hoggar, with a plurifacial evolution ranging from lower amphibolite facies to upper greenschist facies conditions and linked to a regional refoliation, has led us to reconsider the Pan‐African tectonic and metamorphic history in that region. Two areas are described, and a review of other thrusts leads to an interpretative cross section of a large portion of reactivated continental crust. The age and kinematics of this structural reworking have been approached using U/Pb zircon dating in the Tamanrasset region. Despite the difficulty of estimating the age of the initiation of the assumed intracontinental A‐type subduction, the results provide a time span of 30–40 m.y. between the climax of granitoid emplacement and a late retrogressive offset along the thrust planes. Some key ages were determined: (1) 2075 ± 30 Ma is the age given by granulite facies remnants which escaped from the refoliation, the corresponding lower intercept at 530 ± 70 Ma confirms the Pan‐African imprint; (2) 615 ± 5 Ma reflecting the age of syntectonic to late‐tectonic granitoids emplaced in reworked gneisses and in preserved granulites; (3) 580 Ma, the concordant age of sphenes and monazites from the same granitoids, which is interpreted as corresponding to the end of medium‐grade conditions. No evidence has been found of a ∼1000 Ma age: a Kibaran event does not appear to exist in Central Hoggar. The age similarity between the observed deep intracontinental evolution of Central Hoggar and the collision‐related tectonics of Western Hoggar and Iforas suggests a common origin for both phenomena.

Metacraton: Nature, genesis and behavior

“…This event has been dated at c. 615 Ma (zircon recrystallization age, Fig. 12; Bendaoud et al, 2008), which corresponds to the climax of the batholith intrusions in the area (Bertrand et al, 1986;Liégeois et al, 2003;Talmat-Bouzeguella et al, 2011). Similar P-T-t paths, even if with slightly different absolute values, are observed elsewhere in LATEA (Boureghda et al, 2010).…”

Use of Landsat 7 ETM+ for lithological and structural mapping of Wadi Afara Heouine area (Tahifet–Central Hoggar, Algeria)

“…3e) occupies a large surface. By analogy, it is comparable to the batholite of Anfeg dated in ±608 7 by Bertrand et al (1986), worked out again by Acef et al (2003). This batholite is intruded by the subcircular pluton of wadi Temaguessine which is dated at 582±5 My by the method U-Pb on zircon (Abdallah et al 2007).…”

“…So the main objectives of this work are to highlight the most adequate treatments of satellite images to (1) show their contribution to lithologic discrimination of various units met in Wadi Afara Héouine region (Tahifet) and (2) represent the various accidents in a lineament map, especially who were never listed or indicated during the previous works (Bertrand et al 1986;Briedj 1993).…”

Geologic and Metallogenic Framework of North Africa

“…685 Ma (Liégeois et al 2003). Pan-African overprints are represented by reactivation of shear zones along which granitic bodies were intruded, accompanied by greenschist-to amphibolite-facies metamorphism at 630-580 Ma (Bertrand et al 1986;Liégeois et al 2003;Abdallah et al 2007;Bendaoud et al 2008;Fezaa et al 2010). According to Liégeois et al (2003), the Archean and Eburnean LATEA microcontinent was dismembered by mega-shear zones and intruded by granitic batholiths during the main episode of the Pan-African orogeny (640-580 Ma).…”