Whole-rock geochemistry
(XRF) of the arkosic sandstones west of the SDZ show elevated
concentrations of SiO2, Al2
O3, CaO, K2O, and Na2O and decreased
concentrations of FeO, MgO, relative to rocks sampled east of the SDZ
and/or deeper in the borehole. The fracture surfaces that are coated
with clays and oxides/hydroxides are one exception to the above