The Relationship between the Structural Orientation and the Gold Mineralisation of Quartz-Sulphide Veins in the Navachab Gold Deposit, Namibia

- Direct assessment of the gold grade in different vein sets
- Assessment of the factors controlling the grade distribution
- Veins oriented at high angle to bedding have higher mean gold concentrations
- Vein thickness or host rock type do not influence the gold grade in a specific vein

This study uses a representative dataset of more than 500 vein samples from the Navachab gold deposit containing information on the gold concentration, structural orientation, vein thickness, alteration and host rock type to investigate small scale controls on the grade distribution in the veins in order to obtain a better understanding of the architecture of the Navachab ore bodies. We calculated mean gold concentrations for each vein set in different parts of the mine. We then examine the preferential mineralisation of certain vein sets by setting this grade information into context to other geological parameters such as the structural geology of that particular part of the mine as well as the above mentioned factors structural orientation of the vein, vein thickness, alteration- and host rock type. Our main findings are that vein sets oriented favourably to the stress field and at high angles to the bedding are better mineralised than veins sets oriented at low angles to the bedding. Other factors do not exert a great influence on the gold concentration in the veins. We propose that the gold grade in the veins is influenced by the effectiveness of fluid flow into the veins and by time rates during vein propagation and fluid flow.