Karasjokgrønnsteinbeltet. Regional geofysisk og geologisk tolkning

Abstract

A geophysical interpretation of geological structures within 5 map-sheets in 1:50,000 scale (AMS M711) has been done. Petrophysical properties of 1350 rock samples and about 11000 in situ susceptibility measurements have been analyzed. The interpretation is based on all available information including geological and petrophysical data, low altitude magnetic and electromagnetic measurements and gravimetric data. The aeromagnetic interpretation includes a magnetic structure map showing patterns, contacts, magnetization levels and dip estimations. From this map the outcropping of the tectonostratigraphic units and the internal layering can be seen. An interpretation of magnetic dislocations together with a topografic lineament study has been made, revealing 3 directions of dislocation maxima, NE, E and NV. The Ne-direction is thought to be the youngest. Thrusts are also detected from the magnetic data. Detailed gravimetric interpretations have been made along 5 profiles. These model calculation show alternating culmination and depressions with a maximum depth to basement being 4 km. By combining the magnetic and gravimetric interpretation . The map shows two foldsystems, NNe and ESE. The oldest NNE-system is thought to be connected with suturing in this area. These two interfering fold systems are producing 4-5 km deep synclinorias separated by shallow basement-ridges within the Karasjok Greenstone Belt. A regional gravimetric model calculation crossing the Precambrian terrain of the Northern Fennoscandia has been made. This interpretation supports the theory of a suture between the Karasjok Greenstone Belt and Levajok Granulite Belt.