CORE-LEVEL STUDIES OF CALCITE AND DOLOMITE by

Detailed knowledge of chemical bindings on the surface of a mineral is required for theoretical modelling of dissolution processes. For example, Stipp & Hochella (1991) used X-ray photoelectron spectroscopy (XPS) to study bonding environ-ments on the calcite surface. Based on their results, Van Cappellen et al. (1993) created a surface complexation model that postulated the formation of two pri-mary hydration species:>CO3H0 and>MeOH0, where> represents the mineral lattice and Me is the mineral cation. Our motivation has been to extend the knowledge of chemical bonding on the surfaces of calcite and dolomite. Both conventional (XPS) and synchrotron-based XPS (SRXPS) were used to record spectra from (104) surfaces of calcite and dolomite that were cleaved in an ultra-high vacuum (UHV) to minimize surface contamination. Surface sensitiv-ity was altered by changing either the measurement angle (XPS) or photon energy (SRXPS). An electron flood gun (Huchital & McKeon 1971) and a conductive mask (Moulder & Hook 1997) were used for charge neutralization. We discovered that with successful neutralization, it is possible to use SRXP