Cadre geologique et geochronologique U/Pb sur zircon des batholites precoces dans le segment pan-africain du Hoggar central (Algerie)

Metacraton: Nature, genesis and behavior

“…LATEA, made of Archean and Paleoproterozoic metamorphic and magmatic rocks (Peucat et al, 2003;Bendaoud et al, 2008 and references therein) behaved as a craton during the Mesoproterozoic and the Early and Middle Neoproterozoic where oceanic terranes (such as the juvenile Iskel terrane and the Tin Begane eclogite-bearing nappes) were accreted along its margins during Cryogenian and Ediacaran periods ( Fig. 11; Caby et al, 1982;Liégeois et al, 2003;Bechiri-Benmerzoug et al, 2011). No Neoproterozoic events older that 630 Ma have been recorded in the LATEA basement itself, a time that marks the beginning of the Tuareg/West African craton collision.…”

Terrane assembly and geodynamic evolution of central–western Hoggar: a synthesis

“…7a). The base of the series around Silet is defined by polygenic conglomeratic layers with an arkosic matrix displaying angular blocks up to 50 cm in size from the nearby adjacent basement, overlain by a 2-10 m thick dolomitic layer grading to pebbly dolomite (Gravelle, 1969;Caby et al, 1982;Lapierre et al, 1986). Upright incipient slaty cleavage coeval with low-temperature greenschist facies is observed in overlying silty layers, greywackes and metabasalts.…”

“…Greywackes, tuffs and debris flows originating from basaltic volcanoes occur on top, possible pillowed metabasalts being also present. Conformable andesite and rhyodacites flows, and pyroclastic rocks (the Irrelouchem volcanic unit, Gravelle, 1969;Caby et al, 1982;Dupont et al, 1985) make up a c.1500 m thick accumulation preserved in an open syncline cut by hypovolcanic andesite dykes and microdiorite stocks. The geochemical characters (major, trace elements and REE) of volcanic rocks are those of active margin settings (Dupont et al, 1985).…”

Provenance, deposition and age of gneiss units from the KTB drill hole (Germany): evidence from SHRIMP and conventional U–Pb zircon age determinations

“…From the eastern Hoggar, a monzogranite which intruded during amphibolite-facies metamorphism and anatexis has been dated at 604$13 Ma (U-Pb on zircon), and a late kinematic grantic pluton yielded a U-Pb zircon date of 585$14 Ma (Betrand et al 1978). Caby et al (1982), and the pre-tectonic cordilleran batholiths that formed during the Pan-African subduction phase (Pharusian II cycle), dated at 660$4 Ma by Betrand et al (1978), are apparently lacking in the KTB gneiss zircons. However, growth phase I3(v), between 565 and 545 Ma, may have been related to the 550$7 Ma post-collision calcalkaline and alkaline magmas, and 543$9 Ma alkaline dyke swarms dated by Vialette and Vitel (1979) and Lie´geois and Black (1984), respectively, using the Rb-Sr whole-rock method.…”