Geology Reference
In-Depth Information
composed of limestones, jaspilites and quartzites where
spectacular shallow-water sedimentary features (ripple
marks, mud cracks, cross-bedding) are well preserved (e.g.,
at Jbel Mimount) (Fig.
7
). The stromatolitic strata and cross
beds, and occasional herring-bone cross-strati
composed of a succession of metamorphosed ultrama
c
rocks and minor acid volcanic and plutonic rocks (Scher-
merhorn et al.
1986
; Wallbrecher
1988
; El Boukhari et al.
1991
,
1992
; Admou and Soulaimani
2011
). It consists of
serpentine and talc schist, hornblendite and tremolite schist,
amphibolites as well metamorphosed quartz keratophyre and
plagiogranite. Khzama ophiolite is of tholeiitic af
cation indi-
cate that this series was deposited in a shallow marine-tide
and wave-agitated environment.
nities (El
Boukhari et al.
1991
,
1992
). Schermerhorn et al. (
1986
)
concluded that the ophiolite sea-
5.1.5 Bou Azzer Pan-African Ophiolite (Bou Azzer
Inlier, Central AA)
The Bou-Azzer ophiolite, an old fragment of oceanic crust
(697
oor spreading was in a
fore-arc environment, also borne out by the high-Mg low-Ti
boninitic nature of the ophiolite.
8 Ma; El Hadi et al.
2011a
), is a witness of the Pan-
African suture marking the boundary between the Palaeo-
proterozoic Eburnean basement forming the WAC in the
south and the Neoproterozoic accreted arcs to the north. This
ophiolite plays an important role in the geodynamic inter-
pretations of the AA during the Pan-African orogeny that
occurred between 650 and 580 Ma (Leblanc
1976
,
1981
;
Bodinier et al.
1984
; Saquaque et al.
1989
; Hefferan et al.
2000
; Admou et al.
2002
; Gasquet et al.
2005
;D
±
5.1.7 The Major Anti-Atlas Fault (Central
Anti-Atlas)
The Anti-Atlas Major Fault, located south of the South Atlas
Fault, is an important fault in Morocco (Fig.
9
c, d), which
provides information on crustal
tectonics that has global
signi
cance. The fault is underlain by Bou-Azzer and Siroua
ophiolitic complexes and has been viewed formerly as sep-
arating two geological domains in the Anti-Atlas, namely,
the Pan-African domain 600
Lemos et al.
2006
; El Hadi et al.
2011a
; Ouanaimi and Soulaimani
2011
).
The ophiolite consists of serpentines (mainly harzburgites
with chromite pods), gabbroic cumulates and gabbros, and
limited sheeted dyke complexes. Only rare metasediments
associated with volcanic layers are found on top of the oce-
anic complex (e.g., Ambed Co-bearing calcareous jaspers).
The ophiolite sequence was obducted onto the WAC during a
southward-dipping subduction (Leblanc and Lancelot
1980
)
or northward-dipping subduction (Saquaque et al.
1989
). It
hosts the famous Co
'
-
700 Ma in the North-East and
the
2 Ga Eburnian domain in the South-West (Leblanc
and Lancelot
1980
; Saquaque et al.
1989
). Recent studies by
Ennih and Li
*
geois (
2001
), Gasquet et al. (
2008
), Errami
et al. (
2009
) on the Zenaga and Saghro inliers suggest that
the Eburnian and Pan-African materials occur throughout the
Anti-Atlas region and that the entire Anti-Atlas is underlain
by Eburnian crust, unconformably overlain by a lower
Neoproterozoic passive margin. Allochthonous Pan-African
ocean crustal slices were thrust onto the WAC passive
margin sequence
é
Au Bou Azzer mine.
The unusual character of this Neoproterozoic magmatic
and tectonic geoheritage site, together with the excellent
quality of the outcrops in a desertic landscape of ca 15 km
length and 4 km width and the relatively easy access to the
area, make this complex attractive from both a scienti
Ni
Ag
-
-
-
685 Ma ago as a result of Pan-African
accretionary tectonics.
*
5.1.8 Ediacaran Iknioun Granodiorite (Eastern
Anti-Atlas)
The Ediacaran Iknioun amphibole-bearing granodiorites are
intruded into the Saghro Group volcano-sedimentary for-
mations and are intruded by the Iskn
c, an
educative and a geotouristic perspective (El Hadi et al.
2011b
).
'
Allah pink granite and
5.1.6 The Khzama Pan-African Ophiolite (Siroua
Inlier, Central Anti-Atlas)
The well-preserved Pan-African dismembered Khzama
ophiolitic complex, an old oceanic crust, forms a 4 km wide
E-W-striking outcrop. Geochronological data give an age of
760
covered by ignimbrite/rhyolite
n
Mansour. The area is providing didactic contacts between
the main Ediacaran formations of Eastern Saghro, Saghro
and Ouarzazate Groups (Errami et al.
2011
) It hosts basic
rock enclaves that point to a mixed origin for these grani-
toids (Errami et al.
2009
). Iknioun granodiorite displays a
regular pattern of magmatic lineations and foliations deter-
mined through the anisotropy of magnetic susceptibility
(AMS) study. S-sigmoid features outlined by these linea-
tions and top-to-the-SE movements in the adjacent country
rocks show that the emplacement of this pluton was related
to the E-W-trending dextral transpressive movements pre-
viously described in the Saghro inlier. Consequently, this
pluton appears as a particularly useful tectonic marker for
the Ediacaran evolution of this part of the Anti-Atlas which
ows of Jbel Amalou
'
1 Ma for Khzama plagiogranite that cross-cuts the
ophiolite (Admou et al.
2002
; Samson et al.
2004
). The
ophiolitic complex is partly bound by normal faults and is
covered either by the Ouarzazate Group or by the Neogene
Siroua volcanic rocks. The complex comprises mantle
harzburgites, and a crustal sequence typical for oceanic
ridges, including layered gabbros and sheeted dykes beneath
the pillow basalts section. Only rare metasediments associ-
ated with volcanic layers are found on top of the oceanic
complex (e.g., keratophyric tuf
±
tes and
ows).
It
is
