|Résumé||(disponible en anglais seulement)|
The Aley carbonatite-hosted deposit is the most important Nb resource in the British Columbia alkaline province. Portable X-ray fluorescence (pXRF) was used
effectively to determine concentrations of carbonatite pathfinder elements (Nb, Ta, La, Ce, Pr, Nd, Y, Th, U, Ba, and Sr) in stream sediments. Investigation of sediments of the unnamed creek ("Al creek") draining the Aley carbonatite area, indicates
that the +250?m, +125?m, and +63?m size fractions contain high concentrations of carbonatite pathfinder elements (Nb, Ta, La, Ce, Pr, Nd, U, and Th) relative to other size fractions. The +125?m fraction was chosen for systematic evaluation of the
pathfinder element distribution in Al Creek sediments because it is suitable for chemical analysis and Quantitative Evaluation of Materials by Scanning electron microscopy (QEMSCAN). The same samples enriched in pathfinder elements are expected to
contain minerals characteristic of carbonatites such as pyrochlore, columbite-(Fe), fersmite, monazite-(Ce), rare earth element (REE)-bearing fluorocarbonates, barite, and apatite. Optical microscopy, electron microprobe (EMP), laser ablation
inductively coupled plasma mass spectrometry (LA-ICP-MS), and QEMSCAN studies of these samples are required to identify the most useful carbonatite indicator minerals and quantify their relative abundances with increasing distance from the deposit.
The main objectives of this study are to: 1) determine if stream sediment geochemistry can be used effectively to explore for Aley type deposits; 2) establish the best stream sediment size fraction for indicator minerals that might point to
Nb-bearing carbonatite deposits; 3) characterize the geochemical gradient of potential pathfinder elements (Nb, Ta, REEs, P, Ba, Sr, U, and Th) in sediments downstream from the deposit, and 4) evaluate the usefulness of pXRF analyses for preliminary
assessment of indicator mineral and stream sediment studies.