Rare Earth Elements (REE) are metals that are classified as critical for the European industry. They are fundamentally important in the manufacturing of HiTech and green technology products. Today almost the total world REE-mining is controlled by China. REE deposits in Europe are few and none of them are in production. The Fe-dolomite carbonatites (“rauhaugites”) in the Fen Carbonatite Complex in Telemark, Norway, has for some years been known to host abundant REE-minerals. The knowledge of this rock type has, however, been limited to the near surface environment. In 2017 the Ministry of Trade, Industry and Fisheries funded a reconnaissance core-drilling program to test the continuation of the Fedolomite carbonatite at depth. Two rock cores, 1001 and 716 metres long, were recovered at the drillsites, LHKB-1 (near Fen old school) and LHKB-2 (east of Søve) respectively. Core LHKB-1 consists almost only of Fe-dolomite carbonatites down to 1001 metres depth. Core LHKB-2 also consists of Fedolomite carbonatite from top to bottom, but cross-cutting damtjernites (a lamprophyric rock) occur in some intervals. Scattered REE-mineralizations are abundant in both drill-cores. Rare Earth Elementminerals are REE-fluorocarbonates (bastnaesite, parisite-synchysite), and subordinate REE-phosphate (monazite). The LHKB-2 core is generally richer in REE (median TRE2O3 1.70 wt%) than the LHKB-1 (median TRE2O3 1.08 wt%). The thorium content is low (median 181.5 and 128.5 ppm in LHKB-1 and 2 respectively) in these Fe-dolomite carbonatites compared to the Fen rødbergite. Geological, hyperspectral and geochemical analyses of these two reconnaissance drill-cores demonstrates that the REE-bearing Fe-dolomite carbonatites extend at least down to a depth of 1000 metres. An industrial exploration program of the Fen Complex should be considered. This report with appendices presents all chemical and hyperspectral data available from these two reconnaissance cores, and thus serves as an excellent basis for competent industry to plan an eventual exploration program.