Bouabdellah, Mohammed; Maacha, Lhou; Jébrak, Michel et Zouhair, Mohammed
(2016).
« Re/Os Age Determination, Lead and Sulphur Isotope Constraints on the Origin of the Bouskour Cu–Pb–Zn Vein-Type Deposit (Eastern Anti-Atlas, Morocco) and Its Relationship to Neoproterozoic Granitic Magmatism », dans
Mineral Deposits of North Africa, sous la dir. de Bouabdellah, Mohamed et Slack, John F..
Switzerland, Springer International Pub., coll. «Mineral Resource Reviews », pp. 277-290.
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Résumé
The newly re-evaluated Bouskour deposit is a large, polymetallic
vein-type system in the Precambrian Sidi Flah-Bouskour inlier of the
eastern Anti-Atlas orogen. Resources are >53 Mt at 0.8 % Cu, of which
21 Mt has a higher grade of 1.3 % Cu and 9 g/t Ag. Host rocks are
assigned to the Ediacaran Ouarzazate Group, and consist of a succession
of mafic-ultramafic to felsic igneous rocks, both intrusive and extrusive,
with ages ranging from 570 ± 5 to 557 ± 5 Ma, partly intruding
Cryogenian basalt and andesite. Among these igneous bodies, intrusive
felsic rocks are by far the most abundant lithologies, consisting of three
elongate, NW-SE-trending, calc-alkaline intrusions referred to as:
(1) Bouskour Granodiorite, (2) Bouskour Granite dated at 570 ± 5 Ma,
and (3) amphibole-bearing Bouskour Granodiorite. ...
3 successive stages of ore deposition are recognized. The earliest stage (I) is referred to as “Cu–Zn–(Fe–As–Co–Bi–Sn) stage” is followed by the main Cu–Pb–Zn sulphide stage (II), which accounts for most of the exploited sulphide ore at Bouskour. The latest stage (III) forms late fillings in calcite or quartz veins or within older stage I and II assemblages, and includes Au–Ag–Cu–(Zn–Pb) mineralization.
New 187 188 Os age dating of a single molybdenite crystal from stage II yields an age of 574.9 ± 2.4 Ma. This age coincides, within analytical uncertainty, with a SHRIMP U–Pb age on zircon from the Bouskour Granite. The age correspondence suggests a foremost role of granite-derived hydrothermal fluids in the genesis of this polymetallic vein system, consistent with sulphur and lead isotopic data. This timing of
mineralization relates to the final, post-collision extensional stage of the
Pan-African orogeny.
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