A methodology for density determination from core imagery and assays

Abstract

Density is an important physical parameter due to its influence on ore resource and reserve estimation. The most efficient form of density measurement is gamma-gamma logging. However, downhole density logging is rarely conducted in non-ferrous metalliferous mines. Accurate prediction of density from core images could provide an alternative means for continuous density estimation. A Geotek Multi-Sensor Core Logging system has been used to record petrophysical properties and also core imagery on archival drill core from Ernest Henry mine, Queensland, Australia for geometallurgical studies. Mineral grades estimated from the classified core images were not sufficiently reliable for density prediction. However, the fractional volumes can be adjusted to ensure consistency with assay data. A linear programming algorithm was developed for this purpose. Given corrected volumes and mineral densities, it was then possible to predict density continuously along the drill hole. At Ernest Henry the average relative error between image-based density and Geotek gamma-gamma density was 3.5%.