Exploration significance of gravity surveys, Rosebery Mine, Tasmania

Abstract

Gravity surveys of semi-regional specification around, and within, Rosebery Mine in the Mt Read Volcanics of western Tasmania have demonstrated that shallowly dipping base metal ore systems may generate significant perturbations in the gravity field. The effect reflects the entire ore-gangue-alteration association and not simply the proportion of ore of economic grade or density. High relief terrain, complex near surface geology and concealed granite stock do not obscure the correlation with mineralisation. Analysis shows that much of the mine lies within the metamorphic aureole of the granite and the confusing mix of isotope and mineral indicators is fully explained. Comparative analysis of the observed field and that calculated from the rock and density distribution in the mine area has revealed several local anomalous masses. The largest of these, offset from a large barren volume in the mine, has now been shown to be due to a large, previously unsuspected and detached volume of mineralised host sequence.