Major fault zones within the Precambrian Kautokeino Greenstone Belt, Finnmark, Norway: combined interpretation of geophysical data.

Abstract

Process images of aeromagnetic, gravimetrid and topographical data and geological maps combined with EM helicopter measurements and VLF ground measurements have been interpreted in mapping the main fault structures within the Kautokeino Greenstone Belt, KGB. The bulk of the mafic volcanic rocks in the Kautokeino Greenstone Belt is situated within a NNW-SSE-trending, 35 km wide and up to 5-6 km deep trough which is thought to represent an Early Proterozoic rift deformed by strike-slip faulting along the Bothnian-Kvæn- angen Fault Complex, BKFC. The margins of the Alta-Kautokeino Rift, AKR, van be outlined from the geophysical data. The Ciednjaljåkka-Boaganjav'ri Lineament and the Soadnjujav'ri Bajasjav'ri Fault are the main bordering fault zones and are continuous along the entire greenstone belt. The supracrustals between these two zones are continuous to great depth (5-6km) and the contacts along these bordering zones are steeply dipping. Gravity interpretations show that the outer amphibolite-facies rocks are just as deep as the central greenschist-facies unit. Results of the present study suggests that the amphibolite-facies volcano-sedimentary rocks at the flanks of the KGB should also be included in the rift.