Geophysical investigations of the Qaqarssuk Carbonatite Complex, southern West Greenland

During the summers of 1984 and 1985, geophysical investigations were made in the Qaqarssuk area, situated 65°23'N, 51°40'W, in connection with exploration for phosphorus, niobium and lanthanide deposits of potential economic interest. The geophysical field work carried out in the summer of 1984 has previously been briefly discussed (Kjærgaard & Olsen, 1985a). Most of the interpretations have now been completed, some of which are presented below, together with the new results from 1985. The investigations focussed on three subjects: (1) Shallow seismic and geoelectric measurements to map the thickness of residual soil (possibly enriched in P and Nb) overlying the carbonatite. (2) Radiometric meaSurements to localise pyrochlore-rich (V bearing) and lanthanide-rich carbonatites (Th bearing). (3) Magnetic investigations, primarily to map the structures in the carbonatite. A general description of the geology of the complex is given in Knudsen (1985) and Knudsen (1986). A geological sketch map is shown in fig. 1.