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Bou Azzer |
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Morocco |
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Co Au
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Super Porphyry Cu and Au
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The Bou Azzer district comprises a series of small Co-As-(Au) vein deposits in the Anti Atlas Mountains of southern Morocco, 320 km east of Agadir.
The Bou Azzer-El Graara inlier is within the Anti-Atlas in Morocco represents a window into the Proterozoic basement surrounded by a discordantly overlying infra-Cambrian to Palaeozoic cover sequence. The inlier is a segment of a Pan-African (685 to 580 Ma) orogenic belt, located along the main Anti-Atlas thrust, an E-W trending fault zone which constitutes the northern boundary of the West African craton (ca. 2.0 Ga)
Mineralisation is within a Neoproterozoic (788 ±9 Ma) ophiolite complex obducted onto the northern margin of the West African (Eburnian) craton during the Pan African tectonic phase (685 ± 15 Ma).
The Bou Azzer ophiolite is 4 to 5 km thick, and is composed of three domains, namely:
i). an accretionary melange to the south,
ii). a dismembered ophiolite sequence in the centre and
iii). a fore arc volcanic sequence in the north.
The ore deposits are located at the boundary between serpentinite massifs and plutonic, metamorphic or volcanic rocks. The ophiolites are overlain by late Neoproterozoic to Cambrian volcanic and sedimentary cover rocks.
Three types of mineralisation are recognised,
i). Co contact mineralisation at the serpentinite contacts with wall rocks,
ii). Co veins in the wall rocks, up to 400 m from the contacts, and
iii). native silver stockworks at the contact between serpentinite and quartz-diorite.
The Co-Ni-As-(Au) ores of the Bou Azzer district are hosted in variably steep shear zones which occur mainly at or close to the contact of serpentinites with other rock types. Mineralisation has been traced locally for ~1 km within structures that can be followed for up to 5 km. Individual veins and lodes that make up the ore zones are usually between 0.2 and 2 m wide, and have lengths of 30 to 120 m along strike and extend down dip for 20 to 300 m. The pristine ore mineral assemblage mainly consists of Co-Ni-Fe arsenides and sulpharsenides.
Since 1933, 55 000 tonnes of Co and between 2 and 5 tonnes of gold have been produced. Currently (2008), about 150 000 t of ore with grades of ~1% Co, 1% Ni and 3 to 4 g/t Au is mined annually from several mines in the Bou Azzer district.
See also the Bleïda record for information on the Bleïda Far West Au-Pd occurrence in the same area.
For more detail consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 1997.
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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Ahmed AH, Arai S and Ikenne M, 2009 - Mineralogy and Paragenesis of the Co-Ni Arsenide Ores of Bou Azzer, Anti-Atlas, Morocco : in Econ. Geol. v104 pp 249-266
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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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En-Naciri A, Barbanson L, Touray J-C 1997 - Brine inclusions from the Co-As(Au) Bou Azzer district, Anti-Atlas Mountains, Morocco: in Econ. Geol. v92 pp 360-367
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Essarraj S, Boiron M C, Cathelineau M, Banks D A and Benharref M 2005 - Penetration of surface-evaporated brines into the Proterozoic basement and deposition of Co and Ag at Bou Azzer (Morocco): Evidence from fluid inclusions: in J. of African Earth Sciences v41 pp 25-39
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Oberthur T, Melcher F, Henjes-Kunst F, Gerdes A, Stein H, Zimmerman A and El Ghorfi M, 2009 - Hercynian Age of the Cobalt-Nickel-Arsenide-(Gold) Ores, Bou Azzer, Anti-Atlas, Morocco: Re-Os, Sm-Nd, And U-Pb Age Determinations?: in Econ. Geol. v104 pp 1065-1079
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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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