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Gold and Palladium Mineralization at East of Bou Azzer Ophiolite, Morocco

Gold and Palladium Mineralization at East of Bou Azzer Ophiolite, Morocco. M. EL GHORFI 1 , L. MAACHA 1 , A. EN-NACIRI 1 AND T. OBERTHÜR 2 1 Managem, Twin Center, Tour A, Angle Bd Zerktouni et Massira Khadra, Casablanca, Morocco 2 BGR, Stilleweg 2, 30655 Hannover, Germany.

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Gold and Palladium Mineralization at East of Bou Azzer Ophiolite, Morocco

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  1. Gold and Palladium Mineralization at East of Bou Azzer Ophiolite, Morocco M. EL GHORFI1, L. MAACHA1, A. EN-NACIRI1 AND T. OBERTHÜR2 1Managem, Twin Center, Tour A, Angle Bd Zerktouni et Massira Khadra, Casablanca, Morocco 2BGR, Stilleweg 2, 30655 Hannover, Germany

  2. Simplified geological Map of the Anti-Atlas mountains, which developed during Pan-African times at the northern edge of the west African craton. Important ore deposits and the different inliers with Precambrian basement exposures are shown.

  3. Geological Map of the Bou Azzer–El Graara inlier, modified after Leblanc (1981). Ore deposits of Co-As-Cr, copper (Cu) and gold are named and shown by stars.

  4. Focused zoom on the geological map of the interested area • In the Bleïda FW area, an interlayered series of amphibolites, basic and felsic tuffs, chlorite schists, sericite schists, and cordierite schists of sedimentary and volcanic origin, and quartz diorites are exposed and intruded by the Bleïda granodiorite. • Metamorphism in the area is generally of greenschist facies (actinolite, albite, epidote, and chlorite); however, local amphibolite facies of metamorphic grade (hornblende, epidote, calcic plagioclase) has been recorded.

  5. 2.8 Cm S1 S1 (N 45°–60°). S2 (N 120°). Structures and Mineralization • The ore lodes usually occupy structurally favorable S2 sites in folded and mylonitic bands. • The mineralized veins crosscut S1 structures and are synchronous with, or later than, the second Panafrican orogenesis event (B2). • Individual veins are generally narrow (1–2 cm, locally up to 0.5 m wide) and discontinuous along strike and down dip.

  6. A vertical section of the gold mineralization, showing steep north-dipping, andirregular orebodies (up to 100 m depth), and gold grades.

  7. Au vs. Ag Au vs. Pd+Pt 18 6 16 14 5 12 4 10 Ag (g/t) Pd + Pt (g/t) 3 8 6 2 4 1 2 0 0 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 Au (g/t) Au (g/t) Whole Rock Geochemistry • Whole rock geochemistry In the set of combined drill core and surface samples, gold shows positive correlations with Ag, Pd, and Pt only. • Maximum noble metal contents of the investigated ore samples are 170 ppm Au, 18 ppm Ag, 6 ppm Pd, and 177 ppb Pt. • Sulfur contents are generally below 0.01 wt% and are accompanied by low-base metal tenors. • All mineralized samples notably have distinct contents of manganese (0.2–0.3 wt% Mn).

  8. Gold grains are often visible (millimeter-sized) in drill core samples from greater depth and on surface samples. • The Au-Pd mineralization is sulfides free, in some deep-seated samples (up to 100 m), a disseminated, brecciated sulfide assemblage consisting of rare chalcocite, covellite, chalcopyrite and pyrite, occurs in a ferruginous breccia matrix and in vein quartz fragments. Pépites d’Or 2 Cm 3 mm PGM visible Gold Au 400µm

  9. Ba hm Or Ba transmitted light reflected light PGM Qtz Qtz hm chl hm Au-PGM Au-PGM chl alb cal 300µm epi • In polished sections, gold grains are in association with specular hematite and variable amounts of quartz, calcite, barite, epidote, and chlorite. • Gold is usually optically homogeneous; however, it locally contains inclusions or, is intergrown with a suite ofPGM grains along its peripheries.

  10. Gold occurs as open-space filling in fragments of qtz hm-rich material 5 S1 Or calcite S2 50µm 60µm Or S2 S1 S1 100µm and intergrown with a specular hematite, calcite, and quartz. Or

  11. ● Zone des Brèches (ZB) ■ Zone Intermédiaire (ZI) ▲ Zone Central (ZC) Gold composition (EMPA) n = 170 • The composition of gold ranges from 79 to 93 wt% Au, 6 to 19 wt% Ag, and 0.5 to 6.3 wt% Pd. • Mercury contents are generally close to the detection limit of the method (ca. 0.1 wt% Hg) • in rare instances gold grains contain up to 1.33 wt% Hg. • Copper concentrations in the range 0.2 to 1 wt% Cu (average 0.5, max 3.13 wt% Cu).

  12. Platinum Group Minerals (PGM) Determined and Identified In Bleida FW Area by the EMP

  13. Mertieite-I / Isomertieite: [Pd10.9(Sb1.97As1.84)] Sperrylite : [(Pt0.94Fe0.02)0.97(As1.85Se0.04S0.06Te0.06)2.01] 40µm 60µm 20µm • Gold is usually optically homogeneous • It locally contains inclusions or is intergrown with a suite of PGM along its peripheries • In decreasing order of abundance, the PGM were identified: • 1- mertieite-I, • 2- keithconnite, • 3- palladseite, • 4- merenskyite, • 5- kotulskite, • 6- sperrylite. hm Or 6 calcite 6 1  Palladseite : [(Pd16.9Cu0.9)17.8(Se12.8Bi0.7)13.5] Merenskyite : [(Pd0.98Pt0.03)1.01(Te1.93Bi0.04)1.97] Kotulskite : [Pd(Te0.79Bi0.21)] 1 4 2 3 1 Or Pd-Bi-O 4 5 Mn-Fe hm 5 Or Mertieite-I / Isomertieite: [Pd10.9(Sb1.97As1.84)] Keithconnite : [Pd2.92Pt0.01Te0.85Bi0.18]

  14. b S-PGM a Pals & Mert S-PGM 50 Secondary PGM (S-PGM) Secondary PGM are regarded as products of exogenic weathering and mainly consist of ill-defined phases or mixtures of oxides containing the elements Pd, Bi, Te, Se, V, Cu, Fe, and Mn. Mertieite-I and palladseite are locally replaced by a Pd-rich oxides phase. Two distinct groups of “oxides” may be distinguished : Group 1: • Dominated by Bi (>50 wt%) and about 10 wt% Pd, 15 wt% V, some Se (up to 2.4 wt%), and traces of Fe, Cu, Te, Pb, and Mn. O2 concentrations range from 10 to 13 wt%. Group 2: • Dominated by Pd (64–83 wt%) and variable amounts of Bi, Cu, Se, Te, Fe, Mn (up to 2.3 wt%), and V (up to 2.6 wt%).

  15. Summary and Conclusions • The Bleïda Far West mineralization represents a new deposit type in the Anti-Atlas of Morocco. • At Bleïda FW, Au–Pd mineralization is hosted by dominantly brittle structures and displays open-space filling textures in hydrothermally altered amphibolites and chlorite schists • The mineralization is virtually sulfide-free. Free gold is associated with abundant hematite, calcite, quartz, barite, epidote, and chlorite • Chemical signature mainly Au-Pd-As-Sb-Se-Te are registered • In conjunction with the mineral association, oxidizing fluids are indicated, and Au - PGE transport and deposition took place by chloride complexes in the epithermal range, at elevated f O2 and/or low pH. • The origin of PGE is not constrained?

  16. Actually Gold Production in Open Pit Bleida FW Excavation of gold bearing-rocks in Bleida FW (600m long and 180m wide) BPW (1316) BPC (1318) BPE (1322) NBPC Sud C4 (1319) C4 (1315) C4 Est (1316) gradin nord (1332)

  17. The Origin of the PGE? Thanks Very Much

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