Description
DOWNLOAD AMIS CERTIFICATE (PDF)
Origin of Material
This standard was made using ore material from 3 active pits (SUBIKA, AMOMA and AWONSU) within The Ahafo Project. The Ahafo Project is in south-western Ghana, approximately 300 km northwest from the Capital of Accra. The south-western part of Ghana hosts the Birimian Super-Group which comprises several narrow north-east-trending belts of volcanic and volcaniclastic rocks of tholeiitic to acidic composition. These are separated by broad sedimentary basins dominated by turbidites. The Ahafo projects are in the Sefwi Belt, one of the five Birimian volcanic belts. The Sefwi Belt is bounded to the northwest by the Sunyani Basin and to the southeast by the Kumasi Basin. The Dixcove suite or “belt-type” granitoids intrude the contact and predominate in the metavolcanics that form elongate bodies parallel to the regional strike. Cape Coast or “basin-type” granitoid intrusions are found in the southern-most part of the project area.
Regionally, the sedimentary succession consists mainly of fine to medium-grained lithologies (argillites and wackes) with variable amounts of volcaniclastic material. Cape Coast type granitoids intrude the metasediments. The volcanics are mainly basaltic and have been metamorphosed to varying degrees from Lower Greenschist to Amphibolite Facies.
Approximate Mineral and Chemical Composition
Gold mineralization within the Subika deposit in the southern portion of the project area is located within a fracture zone within a host of Dixcove Suite granitoids. Gold mineralization in the southern part of the Sefwi Belt within the Amoma and Awonsu deposits is hosted at or near the contact between the overthrust of the Dixcove granite with underlying meta-volcano sedimentary units.
The mineral composition for the Subika samples are: Quartz – 17%, Albite – 54%, Ankerite – 15%, Calcite – 2%, Muscovite – 7%, Chlorite – 2%, Pyrite – 3%. The mineral composition for the Amoma and Awonsu samples are: Quartz – 15%, Plagioclase – 51%, Muscovite – 15%, Chlorite – 2%, Ankerite – 16%, Pyrite – 1%, Calcite/Siderite – trace amounts.
Certified Concentrations (at two Standard Deviations)
| Analyte | Method | Certified (µ) | (2s) ± | Unit |
| Au | CL | 0.670 | 0.083 | g/t |
| Au | Pb Collection | 0.691 | 0.093 | g/t |
| SG | SG | 2.75 | 0.10 | Dimensionless |
| Ba | 4A_MICP | 631 | 53 | ppm |
| Be | 4A_MICP | 0.7 | 0.3 | ppm |
| Bi | 4A_MICP | 0.1 | 0.09 | ppm |
| Ca | 4A_MICP | 4127 | 675 | ppm |
| Co | 4A_MICP | 13 | 5 | ppm |
| Cs | 4A_MICP | 2 | 0.5 | ppm |
| Ga | 4A_MICP | 9 | 0.5 | ppm |
| Hf | 4A_MICP | 1 | 0.8 | ppm |
| Mo | 4A_MICP | 1 | 0.3 | ppm |
| Ni | 4A_MICP | 22 | 4 | ppm |
| Pb | 4A_MICP | 15 | 5 | ppm |
| Sn | 4A_MICP | 1 | 0.3 | ppm |
| Sr | 4A_MICP | 167 | 21 | ppm |
| Ta | 4A_MICP | 0.4 | 0.3 | ppm |
| Th | 4A_MICP | 5 | 0.5 | ppm |
| U | 4A_MICP | 1 | 0.1 | ppm |
| V | 4A_MICP | 59 | 17 | ppm |
| W | 4A_MICP | 8 | 2 | ppm |
| Y | 4A_MICP | 6 | 3 | ppm |
Major Oxides Certified Concentrations (at two Standard Deviations)
| Analyte | Method | Certified (µ) | (2s) ± | Unit |
| Al2O3 | XRF | 7.95 | 0.29 | % |
| CaO | XRF | 0.59 | 0.01 | % |
| Fe2O3 | XRF | 4.41 | 0.055 | % |
| K2O | XRF | 1.40 | 0.075 | % |
| Na2O | XRF | 1.00 | 0.036 | % |
| P2O5 | XRF | 0.031 | 0.003 | % |
| SiO2 | XRF | 82.13 | 0.49 | % |
| TiO2 | XRF | 0.28 | 0.01 | % |
