Reconstruction of in situ pore-water compositions obtained by aqueous leaching of drill core: an evaluation using multivariate statistical deconvolution

Abstract

A method for reconstructing pore-water compositions from aqueous leachate data obtained from milled and dried drill core is described. The method uses principal component analysis (PCA) to construct an abstract model of the aqueous leachate data which separates out the contaminating components, arising from rock dissolution and drilling fluid contamination, from the pore-water residual solutes component. Iterative target factor analysis (TFA) is used to quantify this pore-water component based on the assumptions that halides in the aqueous leachate are mainly attributable to the pore-water and that the lithium tracer in the drilling fluid is not present in the pore-water. The method is tested on a simulated data set and on data obtained from a deep borehole in Sellafield, Cumbria. The results demonstrate that the proposed method, although requiring further development, has potential use as a powerful investigative tool in a wide range of environmental applications.