En postkarelsk peridotit i urberget norr om Torneträsk

Abstract A post-Karelian peridotite in the Archacan bed-rock north of Lake Tornetrask, Northern Sweden. The bed-rock north of Lake Tornetrask is very monotonous, consisting only of late-Karelian granite and migmatite. Among those rocks is found, however, at Ravaive on the peninsula of Pieksennena, an ultra-basic rock, intrusive in the granite. It is a peridotite consisting of slightly serpentinized olivine. The type is the same as is found in many places in the mountains along the border between Sweden and Norway, belonging to the deepest parts of the Caledonian geosyncline. Besides the peridotite are found soap-stones, consisting of almost pure tale. The shape of the small ultra-basic bodies is seen from Fig. 2. They are very irregular, partly because the intrusions have taken place along fairly small fissure zones in the older rock. No other rock of this kind younger than the late-Karelian granite is known from the Swedish Archaean. The only rocks that could be compared with it are the already mentioned...