Geophysical and geological interpretation of regional structures within the Precambrian Kautokeino Greenstone Belt, Finnmark, North Norway.

Abstract

The Kautokeino Greenstone Belt comprises a synclinorium of volcano-sedimentary rocks. This sequence of Early Proterozoic age is situated between two culminations of gneisses. Large areas of the belt have been mapped in detail (1:50.000) and petrophysical properties of about 1150 rock samples have been measured. Geophysical interpretation based on aeromagnetic and gravimetric maps have been made. The aeromagnetic interpretation includes a magnetic dislocation map showing three directions of dislocation maxima (NNW, N, NE). From an inter- pretation of magnetic structures showing patterns, contacts and magnetization levels, the basement and intrusions can be separated from the supracrustals, primary layering in supracrustals can be seen, and the boundaries between rock units can be located. The gravity interpretation includes model calculations along four profiles. The profiles show alternating culminations and depressions within the greenstone belt with maximum depth up to 6 km. By combining a magnetic interpretation map and a gravity anomaly map a threedimensional analysis can be made. Anticlines and synclines in the greenstone belt emerge clearly on this map. It is concluded that most of the deformation is caused by gravitational tectonics.