Principal components analysis of the geochemistry and mineralogy of the Portaskaig Tillite and Kiltyfanned Schist (Dalradian) of Co. Donegal, Eire

Forty-eight samples of a slightly metamorphosed glaciomarine till (Portaskaig Tillite) and 14 samples of the overlying Kiltyfanned Schist in the Dalradian (? late Precambrian) of Co. Donegal have been subjected to Q-mode principal components analysis based on chemical and modal analyses of the metasediments. This proved useful in comparing the trends of major element variation with those of other analyzed sediments, and revealed features in the sedimentary variation of the mixtite units of the Portaskaig Tillite which were not obvious from the raw data. Good agreement was obtained between sample classifications derived from independent principal components analyses of the geochemical and mineralogical data for both formations. The technique has potential for the study of multivariate trends of variation in sedimentary rocks.