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Geology of Hoggar Hoggar forms an old base whose history is complex.It constitutes a chain link panafricaine which marks out the circumference of the craton Archéen African West. This chain, which extends since Mauritanides in the West, Rockelides in the South, Burkina Faso, is sealed by the Eocambrien deposits of the basin of Taoudeni.

Principal lithostratigraphic units of Hoggar
the solid mass of Hoggar, or Touareg base, includes/understands primarily archaean, paleoproterozoïc and neoproterozoïc formations overcome in discordance by the sedimentary formations of the basin of Taoudeni.

The Eastern unit (in the East of 8°30 '), composed of 3 « terranes »

  • of the protolithes of archaean base terrazzo-gneissique, made up of meta-sediments (pelites, marbles), of meta-basites and compound gneisses (a specific age with 3,3 Ga; Latouche and Vidal, 1974). They are probable equivalents of the archaean mole of Issalane located immediately at the West of the accident 8°30;
  • a volcanogenic series, including basalts, rhyodacites, clastic rocks and black pelites, recristallized in the facies green schist;
  • of the thin straps of ophiolites and the granodiorites (these dated last with 725 My), which recut the preceding sets.

    These terranes is covered, in discordance, by the thick series of Tiririne (> 8000m;660-585 My) which includes/understands:
    • at the base, the trilogy dolomite-sandstone-jaspers (jaspers often corresponding to méta-rhyolites);
    • at the top, of the turbidites, sandstones, conglomerates, arkoses, grauwackes, the whole capped by fluviatile sandstones.

This series is affected by a schistosity (facies schists green) and recut by calc-alkali granite intrusions and volcano-plutonic complexes with dominant acid

The polycyclic central unit (between 4°50 ' and 8°30 ')

central Hoggar includes/understands " terranes " of archaean age (the oldest datings go up to 3,3 Ga) to paleoproterozoïc and mesoproterozoïc, affected by three orogenes (Eburnean ~2 Ga; Kibarienne ~1 Ga; Panafricaine ~600 My).

The archaean base with paleoproterozoïc (mole of Issalane) includes/understands meta-sediments (pelites and marbles), méta-basites, compound gneisses and gneisses (granodioritic with tonalitic).
Mesoprotérozoïque consists of marbles, cipolins, amphibolites, quarzites and mica schists.
The principal accidents NS are marked out volcanogenic and plutonic series of Neoprotérozoïque.


The Western unit (in the West of 4°50 ')

Western Hoggar results from the collision, with the panafricain (630-570Ma), between African Western Craton and the Touareg Shield. It comprises an archaean core (the mole of In Ouzzal, equivalent of Adrar of Iforas more to the South in Mali), stabilized and recut by dated granites with 2 Ga. It is surrounded by younger formations (mesoproterozoïc, neoproterozoïc, cambro-ordovicians, siluriennes, devoniennes, cretaceous and thirdly-quaternary).

  • The archaean mole of In Ouzzal consists of gneiss, charnockites, cipolins and quarzites ferruginous (BIF).

  • The mesoproterozoïc formations include marbles, amphibolites, quarzites, mica schists and, locally, komatiitic intrusions with composition.
  • The neoproterozoïc formations comprise meta-pelites, marbles, dolomites and quarzites, intersected with sills of basic-ultrabasic rocks and locally of andesitic castings. They are recut by two intrusive phases of granitoid, the first with 870-840Ma (Néoprotérozoïque) and the second with 650 My (Panafricain) (granite of Chock Tekadiouit, Immezzarène).
    These formations are covered by the higher volcanogenic green series: lava andesitic, turbidites, grauwackes and recut batholites panafricains.
 
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