Leif Johansson

[1] Baddeleyite is a reliable geochronometer for dating the crystallization of mafic and other silica-undersaturated intrusive rocks. Its high U and negligible initial Pb content enable precise age determinations with statistical errors of a few million years or less. The widespread use of baddeleyite for dating has, however, been limited by the low content of baddeleyite in many samples and by difficulties in isolating baddeleyite. We have developed a new separation technique that utilizes differences in transport velocity among grains of varying size as they move across the deck of a water-shaking table. A small sample portion is loaded instantly on the table, and only the finest and densest material remaining after similar to120 s is collected. Repeated recovery of sample portions yields a concentrate strongly enriched in baddeleyite and opaque minerals; the latter is easily removed by a hand magnet. The "water-based'' separation technique will improve yields of baddeleyite from samples processed on a water-shaking table and is capable of recovering very fine grains. As the entire separation is made in water, problems arising from adhesive forces between minerals are minimized, as is the risk of cross contamination. No heavy liquids are necessary, making separation quick, uncomplicated and inexpensive.