Examples of copper mineralization in the Eastern Anti

G68
Examples of copper mineralization in the
Eastern Anti-Atlas (Maroc): Geological
context and mode of emplacement
ABDEL‑ALI KHARIS, DAOUD ELAZMI, MOHAMED AISSA,
HASSANE OUGUIR AND MOULAY LAHCEN ELMEHDOUDI
(UNIVERSITÉ MOULAY ISMAÏL, MAROC)
The Eastern Anti-Atlas of Morocco lies to the northeast of the Anti-Atlas Major Fault, which separates
it from the West African Craton. It constitutes, at its
base, Pan-African basement of Neoproterozoic age,
overlain by Paleozoic formations. The region contains
numerous metal concentrations hosted in the basement (Bou Skour) and cover rocks (Oumjrane).
The Bou Skour deposit is located 56 km east of Ouarzazate. It
consists of porphyritic mineralization related to a granodioritic
intrusion (680 Ma) of calc-alkaline affinity that cuts the andesites
and was emplaced during the West African island arc collision at
the end of the lower Cryogenian. The emplacement of the intrusion caused intense fracturing, thereby promoting the circulation
of hydrothermal fluids that produced copper mineralization
in the form of disseminations and stockworks in andesite. This
mineralization is associated with potassic alteration, silicification,
and argillic and propylitic alteration. Hercynian-age (Atlasic?)
late remobilization of the NW-SE vein structures affected the
mineralization.
The Oumjrane mineralized district is located 90 km
northeast of Zagora. It consists of epithermal
(high-sulphidation) copper mineralization related to
an intracontinental extensional phase that has been
recognized at the scale of the Eastern Anti‑Atlas during Visean time. This mineralization is the result of remobilization of earlier mineralization via hydrothermal
fluids, giving rise to lenticular vein-type mineralization
in Ordovician quartz sandstones. Hydrothermal circulation produced vertical and lateral zonation of the
metallic minerals (pyrite, arsenopyrite, chalcopyrite,
galena and sphalerite) in E-W and NE-SW Hercynian
mineralized structures. This was accompanied by
strong silicification. Copper enrichment following
supergene alteration, likely related to the lower Jurassic-Cretaceous emergence, affected the mineralized
structures of Oumjrane.
Posters
The copper mineralization of Bou Skour and Oumjrane
are the focus of our work, with the aim of developing
a model of emplacement and establishing whether a
genetic link exists between the metal concentrations
in the basement and those in the cover rocks.
By combining the geological and metallogenic characteristics of the two deposits described above, we
can conclude that copper mineralization in the Eastern
Anti-Atlas was likely related to two major events:
`` a Pan-African (Neoproterozoic) event responsible for the emplacement of copper concentrations in the basement rocks;
`` a Hercynian-Atlasic event that caused the
remobilization and reconcentration of copper
in NW-SE, NE-SW and E-W structures.
Extract of DV 2014-04
151

Download Report