SIGNIFICANCE FOR GOLD EXPLORATION OF STRUCTURAL STYLES OF AURIFEROUS DEPOSITS IN THE ARCHEAN BULAWAYO-BUBI GREENSTONE-BELT OF ZIMBABWE

Practical application of a knowledge of the structural controls on Arc haean gold deposits is of considerable importance in gold exploration- for example, in the Bulawayo-Bubi greenstone belt in the southwestern part of the Zimbabwe craton. The regional structural architecture of s hear and deformation zones in the belt, which is recognizable in plan view on Landsat TM imagery, is interpreted in terms of a conjugate-she ar model. Gold mineralization is related to this framework at a variet y of scales. On a mine scale the principal recurrent structural geomet ries that host most of the significant gold deposits in the belt are a ssociated with shear zones and folds and include conjugate systems (sh ears, shear intersections, kink sets), sidestep systems (en echelon se gmentation, duplexes, monoclinal inflections, antiform-synform couplet s) and interactions of the two. Linear sections of shear zones are gen erally poorly mineralized. The kinematics of the parent structures ref lects the structural evolution of the belt as a whole, although kinema tic interpretations of the deposits are of less importance to mine and exploration geologists than an appreciation of their structural geome tries. An important concept in using this approach in the selection of exploration targets for gold is the scale-invariance, or fractal natu re, of the structural patterns produced, which means that the same geo metries are identifiable on all scales from local (deposits) to region al. Hence, sections of regional structural lineaments or areas within mines should be prioritized for further investigation or development o n the basis of the gold-bearing geometries that are observed to be dom inant locally.