Five strata-bound massive sulphide deposits are situated at three different stratigraphic levels in the volcanogenic Fundsjø group in the Folldal area. The deposits are bosted in metabasalts, metarhyodacites and volcaniclastic rocks and betong to the Cu-Zn class of volcanic-associated massive sulphide deposits. The metal con tent of the deposits indicates that the sources of metals are underlying strata, possibly with a contribution from intrusives. Wall rock alteration varies according to differences in host rocks, and is probably a result of chemical variations of the host rocks, temperature differences and proximity to the hydrothermal vent. The clustering of deposits in the Folldal area is considered to be due to the occurrence of a large subvolcanic trondhjemitic intrusion which acted as the major heat engine for convection. The small size of the deposits might be related to the shallow level of the intrusion.
T. Bjerkgård & A. Bjørlykke, lnstitutt for Geologi, University of Oslo, P. O. Box 1047 Blindern, 0316 Oslo, Norway.