QUANTITATIVE MODEL OF SEDIMENT DISPERSAL AND HEAVY MINERAL DISTRIBUTION IN NORTH CARDIGAN BAY, IRISH SEA

The formation of economic-grade noble metal and heavy mineral placers at high latitudes is facilitated by the interaction of high-energy wav es and currents with the multimodal size and density fractions of glac ial material (Emory-Moore & Solomon, 1989). Placers which form under s uch conditions tend to exhibit very irregular distribution patterns, s uch that these deposits are typically not distinguished by traditional sediment dispersal modeling techniques. In an effort to model sedimen t dispersal patterns in high-latitude regions more effectively, multiv ariate geostatistical analyses, which have proven successful in modeli ng complex sediment dispersal patterns in a number of marine and lacus trine areas, were carried out on sediment geochemical data for 184 sam ples from a typical high-latitude coastal site (North Cardigan Bay). A Q-mode factor analysis of North Cardigan Bay sediments revealed that >99% of the total variance in the data can be explained by four end me mbers, representing (1) mixed quartz and orthoclase, (2) mixed alumino silicates, (3) carbonates, and (4) heavy minerals. Linear programming was used to estimate the relative amount of these end members in each sample; the data from this analysis were used to model sediment disper sal. By comparison with the results of a comprehensive study of North Cardigan sediments by Moore (1968), this modeling approach accurately predicts the sediment distribution pattern for North Cardigan Bay. Thi s sediment dispersal modeling procedure represents a significant impro vement over traditional techniques, in that sediment dispersal is not constrained to occur along concentration gradients and if requires onl y the type of sediment geochemical information that would be obtained in a standard reconnaissance-level exploration survey.