Abstract

A number of generally small and economically unimportant Mo mineralizations are found in amphibolitic horizons in high-grade metamorphic rocks in the southernmost part of the Precambrian of Norway. All of these mineralizations are associated with a series of gray, amphibolitic gneisses.The ores in the Flottorp area occur stratabound in a series of folded, high-grade amphibolitic and granitic gneisses. The mineralization is always found in connection with a folded zone of amphibolitic, banded gneisses. Molybdenite, pyrite, chalcopyrite, and pyrrhotite are the main ore minerals. Textural observations suggest that minimum temperatures of 450 degrees to 500 degrees C have been reached during metamorphism of ore and host rock.Fluid inclusions in matrix quartz from the mineralized host rock were found to vary in composition from nearly pure CO 2 through H 2 O + CO 2 mixtures to entirely aqueous, saline fluids. High-density, isolated CO 2 -rich fluid inclusions are considered to approximate most nearly the fluids present during peak conditions of metamorphism of ore and host rock and indicate pressures of 3.5 to 4.5 kb and temperatures around 650 degrees C.The majority of aqueous inclusions have salinities around 10 equiv. wt percent NaCl. Microthermometry and chemical analysis of leachates indicate the presence of minor amounts of cation such as K (super +) , Ca (super +2) , and/or Mg (super +2) in the inclusion fluids. The aqueous inclusions primarily represent fluids present during repetitive episodes of microfracturing and progressive introduction of meteoric water during uplift and cooling.

First Page Preview

First page PDF preview
You do not currently have access to this article.