Classification of distinct eruptive phases of the diamondiferous Star kimberlite, Saskatchewan, Canada based on statistical treatment of whole rock geochemical analyses

Discrete eruptive events of the Star kimberlite, Saskatchewan, Canada have been classified into five distinctive clusters using statistical methods applied to whole rock geochemical data. The data set consists of 270 kimberlite samples from 38 drill holes that were analysed for whole rock major- and trace-element geochemistry. The data set was analysed by multivariate statistical techniques after a log-ratio transformation, including principal component analysis and linear discriminant analysis. Data analysis using principal component analysis recognized five distinct classes, confirmed by petrographic study, which correspond to unique mineralogical compositions. Based on relationships from detailed drill core logging results, these five geochemical classes are the Cantuar, Pense, early Joli Fou (eJF), mid Joli Fou (mJF) and late Joli Fou (lJF) equivalent age eruptive phases of the Star kimberlite. Subsequent statistical analysis utilizing linear discriminant analysis supports the distinctions between the classes. For the four kimberlite eruptive phases (Pense, early Joli Fou, mid Joli Fou and late Joli Fou) for which there is macrodiamond data from bulk sampling, there is an excellent correlation between the amount of lithospheric mantle contamination (as defined by the geochemistry) and the diamond grade.