Abstract

To gain a better understanding of the geologic controls on sodium distribution, samples of coal were obtained from 27 sites from the Wasatch Plateau in central Utah. As much as 90 percent of the sodium, particularly in the central and south-central parts of the plateau, occurs in analcime, a hydrous sodium aluminum silicate. Equilibrium modeling indicated that the water from the aquifer within the Ferron Sandstone Member of the Mancos Shale may be the source of the sodium in the overlying coals. The Pleasant Valley and Joes Valley fault systems provided a conduit through which sodium-bearing aquifer waters migrated vertically to reach the overlying coal-bearing strata. The distribution of the sodium was controlled by the hydrology and structure of the Ferron Sandstone Member which forms a broad syncline under the Plateau. As a result, the highest sodium (analcime) contents lie between the fault systems and along the trace of the synclinal axis. It is concluded that (1) the analcime-bearing coals will have low fouling potentials; (2) established indices for predicting fouling potential do not apply to these coals; (3) analcime can be physically removed from these coals by conventional coal cleaning techniques; (4) weathered surface samples of coal can be used for evaluating the original sodium content of the coal; and (5) the geologic controls on sodium distribution in the coals of the Wasatch Plateau have been identified, so sodium concentrations may now be estimated in areas where analytical data are absent.