The geology, exploration and characterisation of graphite deposits in the Jennestad area, Vesterålen, northern Norway

Abstract

This paper reviews graphite exploration in the Jennestad area, Nordland. As a result of helicopter aeromagnetic surveying and subsequent ground geophysics mapping and trenching, some 30, variously sized bodies of graphite schist identified.The graphite-bearing schist occurs associated with dolomite marbles amphibolites and pyroxene gneisses, all of which are intruded by charnockites and granites. The graphite is coarse, fully ordered, crystalline and flaky. Graded up to 40% carbon were found. Gangue minerals in the ore are quartz, plagioclase, K-feldspar, biotite and orthopyroxene. Some of the largest ore bodies contain about 250,000 tonnes each with an average grade of 20% carbon. Bench-scale benefication tests shown that the ore can be upgraded to a maximum grade of 97% C, with a recovery of 89%. It is believed that the graphite schists were originally sediments rich in organic matter which was converted to graphite during granulite-facies metamorphism.