THE EFFECTS OF METAMORPHISM, TECTONICS AND HOST ROCKS ON THE LOCATION OF SULPHIDE ORES IN THE KONGSBERG SERIES, SOUTH NORWAY.
Abstract
A study has been made of two deposits of Fe-Cu-Zn sulphide ores,
from Gr¢sli and Eiker, in the Proterozoic Kongsberg Series of South
Norway. The ores are located at the junction of acid-intermediate
supracrustals and amphibolitized gabbros. The supracrustals underwent
Upper Amphibolite facies metamorphism of Svecofennian age (1600 to
1500 m.y.B.P.) and were then intruded by the gabbros which underwent
subsequent Sveconorwegian (1200 to 1000 m.y.B.P.) metamorphism at
~lid-Amphiboli te facies grade.
The ore bodies were originally part of the supracrustal sequence,
which was deposited as a volcano-sedimentary succession (with some
hydrothermally altc:ced equivalents), similar to the KuroKo-type c1r.'posits
of Japan. The ores have thus undergone both phases of h5[;h grade
regional metamorphism. At Gr¢sli, the ores were partially incorporated
in the gabbros prior to the later (Sveconorwegian) metar.lorphism, during
which extensive shearing occurred throughout the ores at Eiker.
The cores of the gabbroic intrusions retained original igneous
mineralogies and textures, with progressive amphibolitization towards
the peripheries. A subsequent Epidote-Amphibolite and later Greenschist
facies grade overprint produced varying retrograde assemblages in the
silicate rocks. Under Greenschist facies conditions, rejuvenation of
the Sveconorwegian shear (at Eiker) caused brittle faulting, while fluid
activity (at both Gr¢sli and Eiker) caused the formation of chloriteact
ino.li te-carbo!)a.te assemblages around some of the ore bodies. Renobilisation
of ~he ore material itself was minimal.
Studies of R00thermometry and geobarometry indicate that the ore deposits were re-equilibrated during the Epidote-Ampllj boli te facies
overprinting.
Authors
Dibb, Timothy EricCollections
- Theses [4122]