Petrography, mineralogy and whole-rock data of the major lithologies of the Fen Complex

Abstract

This report documents the petrography of a limited sample set consisting of 12 specimens from the Fen complex, Telemark, South Norway. The samples comprise several, texturally variable calciocarbonatites (søvite), one Fe-rich carbonatite (rauhaugite), two magnetite-rich rødbergites, a silico-carbonate rock (\"vipetoite\") and a lamprophyre termed damtjernite. Major REE minerals are LREE carbonates and monazite in the søvite and rødbergite and LREE carbonates in the rauhaugite and damtjernite. The LREE are enriched to greater degrees (up to 4000-fold in the rødbergite and an inclusion-rich søvite) and lowest contents for Lu, a HREE, were found in a relatively fine-grained søvite sample, corresponding to a 2-fild enrichment relative to primitive mantle. The sum of all REE is as high as 15950 ppm in the REE-richest sample, a rødbergite, alnd lowest (715 ppm) in a søvite. The concentration of Th tend to correlate positively with the sum of the REE and are 1470 ppm in the REE-richest rødbergite and <20 ppm in the søvite. Uranium is as high as 114 ppm in the søvite and 20 ppm or less in the other lithologies.