Digital mapping and GIS-based spatial analyses of the Pur-Banera Group in Rajasthan, India, with special reference to the structural control on base-metal mineralization

Abstract

GIS-based ‘digital’ maps help to store geological field data in a georeferenced framework that can be easily displayed at map-scale to outcrop-scale, without the need to map an area separately at different scales. In the iron and base-metal (Pb–Zn ± Cu) prospect of Pur-Banera belt in Rajasthan, India, multiple phases of folding and shearing of the host rocks have led to a complex structural pattern. The relationship between deformation and ore (especially the base-metal ore) localization is not well understood, although it is very important for mineral prospecting and mining. To facilitate exploration targeting, a large part of the Pur-Banera belt is mapped by us at different scales, using the ArcGIS™ platform. The resulting map is ‘intelligent’ in nature, as it can display geological field data at different scales by just zooming in and out, and it is possible to retrieve any type of geological data from any outcrop/sector through a specific GIS-query. Photographs and virtual 3D models of an outcrop can be opened through hyperlinks. Geospatially referenced mapping of the Pur-Banera belt demonstrates four phases of folding, of which the F3 folds define the regional structural pattern. Detailed mapping of mineralized bands and gossans indicate that the originally stratiform iron ore is best mined at the F3 hinge zones where these layers are thickest due to repeated folding. In contrast, the primarily stratabound Pb–Zn ± Cu ore has largely remobilized during F2 folding, becoming concentrated in the hinge zone and/or along the axial plane of F2 folds, which are consequently now the best prospect sites for base metals.