Geology Reference
In-Depth Information
Fig. 6
Landsat TM image of the
Zenaga Inlier showing the
Palaeoproterozoic surrounded by
the Neoproterozoic volcano-
sedimentary rocks and Palaeozoic
sediment cover (Ennih et al.
2001b
)
Fig. 7
Sedimentary structures of
the Precambrian rocks of the
Taghdout Group in the Anti-
Atlas.
a
Complex of ripple-drift
lamination, and ripple lamination
in sandstone (
b
) and (
c
). Small
scale ripple lamination, horizontal
lamination, mud drapes, buried
ripple bedforms, and larger-scale
cross lamination.
d
Mud cracks
exposed on a bedding surface
—
the cracks are
lled with
syndepositional sand.
e
Rippled
sandstone.
f
Close-up of rippled
sand showing asymmetric ripples
5.1.3 Neoproterozoic Doleritic Dykes (ca
1,000
-
800 Ma)—Witness of the Break-Up
of the WAC During the Pre-pan African
Orogeny
The Palaeoproterozoic basement of the Zenaga inlier is
cross-cut by tholeiitic dyke swarms in N
dykes consist mainly of gabbro, dolerite and trachy-ande-
sites. They often preserve their original texture and their
primary mineralogy, in spite of a secondary hydrothermal
alteration under greenschist facies (epidotization, hematiti-
zation) probably related to the Pan-African orogeny. The
primary mineral assemblage consists of plagioclase, clino-
pyroxene (augite), very rare orthopyroxene, ilmenite, apatite,
S, NW-SE and NE-
-
SW directions (Ennih et al.
2001a
;Ha
d et al.
2001
). These