CONTRASTING STRUCTURAL CONTROLS ON GOLD MINERALIZATION ALONG THE ELDORADO SHEAR ZONE, ZIMBABWE

The Eldorado shear zone is a regional shear zone that runs along or ne ar the southern margin of the Chinhoyi greenstone belt in the Zimbabwe Archaean craton. Four of the seven mines with recorded gold productio n greater than 100 kg in the southern part of the greenstone belt lie on the shear zone, including the top two current producers, Golden Kop je and Muriel. Displacement occurred in the late Archaean, producing a shear zone with a trend that ranges from northeast at Golden Kopje mi ne to east at Muriel mine. The orebodies at the two mines formed synch ronously with shearing and show strong but contrasting structural cont rols on mineralization. The Golden Kopje orebodies plunge to the south west, parallel to the intersection of S with C or C' planes and sub-pe rpendicular to local stretching lineations. The Muriel orebodies plung e steeply west but parallel to local stretching lineations. The greate st fluid flow during mineralization of the Eldorado shear zone was alo ng either the intersection of fabrics (Golden Kopje) or the extension direction (Muriel mine). There is no unique relation between the orebo dies and the extension or shear direction. Where earlier mining has no t established the orientations of oreshoots it is essential to underst and the possible structurally controlled geometries of orebodies befor e designing a drilling programme to evaluate their potential.