CHEMICAL AFFINITIES OF IRON AND MANGANESE IN PENNSYLVANIAN COAL-BEARING STRATA IN THE CENTRAL APPALACHIAN BASIN: IMPLICATIONS FOR CONTAMINATED MINE DRAINAGE

Two cores that penetrate Upper to Lower Pennsylvanian strata in the Central Appalachian basin have been analyzed in 1 foot increments for major and minor element and major mineral phase concentrations. The lower Upper Pennsylvanian Conemaugh Group (CG) and the upper Middle Pennsylvanian Allegheny Formation (AF) are represented in one core from northern West Virginia. The lower Middle Pennsylvanian Kanawha Formation (KF) and upper Lower Pennsylvanian New River Formation (NR) were cored in southern West Virginia. Statistical correlations of major element and mineral concentrations indicate that the dominant mode of occurrence of Fe and Mn is in siderite. Within the CG, AF, KF and NR, Mn (reported as MnO) is strongly correlated with Fe (reported as Fe₂O₃) and siderite. Iron is not correlated with either sulfur or pyrite. Within each formation, sulfur is strongly correlated with SO2 and pyrite.

A comparison of the mean concentrations of Fe, Mn and siderite among formations indicates that they are, for the most part, statistically different from one another. There appears to be a consistent statistical linkage between the concentration of Fe and Mn associated with siderite. The NR has the lowest concentration for each variable and the CG has the highest concentration for Fe and siderite.

Cluster analysis on data from each complete core (not classified by formations) yields a sample grouping that contains the highest mean concentration among clusters for Mn, Fe and siderite. Within the core from southern West Virginia, three of the four samples within the cluster are contiguous in a NR sandstone. All 5 samples from the other core are scattered throughout siltstones where geologist core logs often noted siderite-filled root traces. These preliminary results indicate the importance of understanding the stratigraphic, elemental and mineralogical affinities of deleterious elements such as Mn in the prediction and mitigation of contaminated mine drainage.