The Kolsvik Au-As-deposit, Bindal, North-Central Norway, I: Corelogs

Abstract

The report presents the corelog for 47 diamond-drillholes (total corelength: 3430 m) drilled by A.S. Sulfidmalm and Terra Mining A\/S in the periods 1980-82 and 1985-86, respectively. From the corelogs, the summary corelog-diagrams and the drillhole profiles several conclusions can be drawn regarding ore control and ore genesis. The native gold being generally fine-grained (1-100 um) is strongly intergrown with arsenopyrite and is only locally found as tiny visible grains. Mineralisation of economic potential occurs along a system of brittle dextral shear zones at the margin of the Early Silurian Oksdal granite massif. The mineralisation constitutes fracture fillings, veins and breccias of arseno- pyrite which nearly invariably are hosted by the competent granitoids and pre- existing quartz veins along the shear zones. Although not much can be said about average ore grades the deposit is estimated to have a total reserve potential in the range 550 000 - 850 000 tonnes for a 1 m wide and 100 m deep ore zone with ore density of 2,75 tonnes\/m3. 250 000 tonnes of this preliminary estimate probably contain enough gold for small scale mining. Further work is recommended. Frie emneord: Kaledonidene Malmpotensiale