CESIUM-LABELED PHLOGOPITE AS A TRACER FOR IN-SITU STUDIES OF SEDIMENTBURIAL, REWORKING, AND RESUSPENSION RATES

Phlogopite is a mica mined commercially in eastern Canada. Its major e xchangeable cation, K+, can be removed with sodium tetraphenylboron. W hen the K-depleted phase is soaked in CsCl (aq), it binds Cs+, forming a new crystalline phase, CsPhlog, that contains up to 10 weight-% Cs. The new phase binds Cs+ strongly (K-D > 10(6)), making CsPhlog stable enough to be useful as a tracer for clay particles. We investigated t he direct determination of Ca in lacustrine sediments using neutron ac tivation analysis, X-ray fluorescence spectrometry, and radio frequenc y (r, f.) glow-discharge mass spectrometry. Glow discharge mass spectr ometry proved insufficiently sensitive due to isobaric interferences, but the other two methods were usable at tracer levels. Activation ana lysis was used for routine determinations because of its superior sens itivity. Starting with CsPhlog containing a few percent Cs by weight, the observed sensitivity translated to a measurable dispersal factor o f at least 10(4). We used CsPhlog deployed from a manned submersible t o study sediment reworking in Lake Superior, where it behaved similarl y to rare-earth oxide tracers deployed simultaneously.