Use of petrophysical characterisation techniques in receptivity definition for carbonate-hosted MVT deposits

Abstract

Lithostratigraphically controlled replace-ment mineralization in the South Pennine Orefield, UK, has been studied to ascertain the petrophysical characteristics of receptive horizons. These exhibit significantly different pore parameters but mineralization is more directly controlled by the presence of hydrophobic, low solubility and low porosity horizons that create_‘intracarbonate ponding surfaces’ on which downward fluid movement is retarded and fluids focussed along the upper interface. For deposit formation a strong contrast is required with the overlying units so that the enhanced fluid flow and residence time can initiate and propagate replacement. The mechanical properties of the overlying units are also important. This represents a new conceptual approach to defining receptivity and for the first time allows receptive units to be identified by their essential and measurable petrophysical signatures. These techniques are already being used in an on-going exploration programme.