Discriminant Analysis as a Method of Flow Identification and Correlation in Layered Basalt Provinces

摘要

Discriminant analysis was applied to over 50 flows of the Columbia River Basalt Group which range from widely differing compositions (Saddle Mountains Basalt) to only slight chemical differences (Grande Ronde Basalt). Well-defined, correlated stratigraphic sections were tested for the probability of correctly identifying individual flows or groups of flows. Probability of properly identifying samples from flows of the Saddle Mountains Basalt approaches 1.0. The Grande Ronde Basalt constitutes approximately 85% of the Columbia River basalt and consists of >35 flows, yet it has previously been divided into only three chemical groups. Using 21 variables for each sample and 28 groups, approx. 67% of the samples were correctly identified with probabilities ranging from 0.3 to 0.9. Elements that were particularly important in discriminating Grande Ronde Basalt flows were MgO (3.0 to 6.0 wt %), TiO sub 2 (1.6 to 2.6 wt %), Zr (160 to 250 ppM), Ba (300 to 1050 ppM), and P sub 2 O sub 5 (0.2 to 0.5 wt %). (ERA citation 06:011688)