The sulphide deposit of Nordre Gjetryggen Gruve, Folldal, Norway.

Abstract

Nordre Gjetryggen Gruve in the Folldal district, southern Norway, is at approximately 62 9'N. latitude and 10 E. longitude. The mining of copper from pyritic ores began in the area in 1748, while the recovery of zinc and sulphur became important in the 19th century, Nordre Gruve alone yielded 1,1 million metric tons of raw ore before 1957. From then until 1962 it produced about 65 thousand tons of raw ore per year. The mine has been developed for about 420 meters along the strike of N.42 E. and to a depth of 510 meters. The ore body dips 38 NW. in the western part and between 45-50 NW. in the eastern part; the ore zone plunges 45 NE. The average thickness of the ore is 1,66 meters. Geologically, the district is in the southwestern part of the Trondheim region near the Sparagmite boundary and Nordre Gruve can be cosidered to be on the southwest limb of a northeasterly plunging syncline composed of schists in the quartz-albite-epidote-almandine subfacies of the greenschist facies that have been assigned tentatively to rock units similar to those in the Hølonda-Horg district. The rock units mapped are: 1) undifferentiated schists composed dominantly of quartz, chlorite, calcite, biotite, epidote, and hornblende; 2) quartzite schists; 3) hornblende-quartz schist; and 4) trondhjemite now albite-quartz-garnet gneiss, and surficial material.