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Bleida |
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Morocco |
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Cu
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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The Bleïda copper deposit is located in the Anti-Atlas of Morocco, North Africa, 330 km east of Agadir.
The Bleida volcano-sediment hosted sulphide deposit was developed at several horizons within a Neoproterozoic marginal basin of the Bou AzzerEl Graara inlier, comprising three successions of ferruginous jasper, sulphide bearing felsic tuffs and turbidites. These sequences are developed on both sides of a half horst along a synsedimentary normal fault. Towards the fault the jasper becomes apatite and chlorite rich and grades to a chlorite and K feldspar rich albitite. Over the same interval the sulphides grade from pyrite-chalcopyrite-bornite to bornite-chlorite rich albitite.
The three mineralised levels comprise the following, from the base:
1). A 50 m thick keratophyric horizon is developed above a basaltic lava suite. It lies within a discontinuous jasper-carbonate bed and is made up of lava domes, volcanic breccias and waterlain tuffs interbedded with pyritic black shales. The ore occurs as lenses of disseminated copper sulphides, mostly within the felsic tuffs above magnetite rich keratophyre. Grades are from 2.5 to 3.5% Cu.
2). A 20 m thick volcaniclastic band, commencing with a jasper bed, followed by finely laminated pyritic felsic tuffs and ash flow tuffs. This unit, which overlies the black shales that separate it from the first ore layer, hosts three lenses of 6 to 9% Cu as finely laminated high grade sulphide. It is in turn overlain by a thick turbidite.
3). Lenticular horizons of felsic tuffs within the turbidite unit, with low grade mineralisation in tuffs, above a jasper bed.
Chalcopyrite dominates over pyrite, and laminae of magnetite are found in the basal parts of the jasper beds that underlie each of the sulphide units
Individual ore lenses are 0.5 to 4 m thick and 50 to 90 m wide, while the main lens extends down plunge to 330 m below surface. The deposit carries 200 000 tonnes of contained copper metal.
Structurally controlled AuPd mineralisation occurs at Bleïda Far West in a section of the volcano-sedimentary rock sequence represented by altered amphibolites and chlorite schists. This mineralisation has been mainly deposited in brittle structures and is virtually sulphide-free, with gold being associated with hematite, barite, selenides, quartz and calcite. The gold grains carry silver and palladium levels of up to 19 wt% Ag and 6.3 wt% Pd and are intergrown with a distinct suite of mainly Pd-dominated platinum group minerals, specifically mertieite-isomertieite, merenskyite, keithconnite, kotulskite, palladseite and sperrylite. It is unclear whether the mineralisation is late Pan-African (600 to 550 Ma) in age, or connected with the Variscan orogeny (330 to 300 Ma), or related to some other hydrothermal event. See also the Bou Azzer district record.
For more detail consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 1990.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Selected References:
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El Ghorfi M, Oberthur T, Melcher F, Luders V, El Boukhari A, Maacha L, Ziadi R and Baoutoul H, 2006 - Gold-palladium mineralization at Bleida Far West, Bou Azzer-El Graara Inlier, Anti-Atlas, Morocco : in Mineralium Deposita v41 pp 549-564
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Leblanc M, Arnold M 1994 - Sulfur isotope evidence for the genesis of distinct mineralizations in the Bleida stratiform Copper deposit (Morocco): in Econ. Geol. v 89 pp 931-935
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LeBlanc M, Billaud P 1990 - Zoned and rercurrent deposition of Na-Mg-Fe-Si exhalites and Cu-Fe Sulfides along synsedimentary faults (Bleida, Morocco): in Econ. Geol. v85 pp 1759-1769
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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