9526673 Hall This project applies newly refined 40Ar/39Ar dating techniques to the problem of dating large scale hydrothermal systems. Recent improvements in the 40Ar/39Ar method have demonstrated the potential for this technique to handle even the finest-grained material. This project will concentrate on five study areas: a) the Cerro Colorado porphyry copper deposit, Panama; b) Mississippi Valley-type (MVT) deposits with pre-existing Rb-Sr age information; c) sediment-hosted micron gold deposits, Nevada (Twin Creeks); d) the Almaden mercury district, Spain; e) the Tsumeb-Kombat chimney deposits, Namibia. Samples for all five sites have been collected. The Cerro Colorado deposit is associated with coarse-grained minerals which have already been dated using K-Ar, and this will provide a good test for the ages derived from fine-grained alteration products. The MVT deposits have high quality Rb-Sr ages already available, thus providing a further test of the system. The remaining three sites have arrange of existing ages with very little consensus as to the timing of the hydrothermal activity. It is with these sites that the project should provide the greatest amount of new information.
