GEOCHEMICAL FACIES ANALYSIS OF LI-ENRICHED PALEOSOLS IN COAL MEASURE STRATA OF THE NORTHERN APPALACHIAN BASIN

A regional lithologic and chemostratigraphic framework for a high alumina clay and coal-bearing formation in central and western Pennsylvania demonstrates that elevated [Li] exists in predictable stratigraphic horizons in polygenetic paleosol profiles: in intensively rooted zones immediately beneath coals, and meters deeper in a zone of pervasive siderite spherules. The formation exists in a Pennsylvanian-aged coal-bearing group formed by deposition in an ancient river delta subjected to episodes of varying redox conditions. A model of [Li] involves: 1) deposition of Li-bearing minerals on a floodplain with subsequent burial, weathering and leaching of overlying strata under relatively well-drained conditions; 2) liberation of Li under saturated and reducing conditions as the regional water table rose and siderite spherules precipitated; 3) biological pumping of Li by plants with subsequent Li redistribution in the ancient soil profile; and, 4) interruption of biolifting by water table rise and flooding of the land surface at which time peat formed resulting in the coal seams we observe today. Elevated [Li] are positively correlated with [Al] suggesting that Li is most associated with clay minerals and other aluminosilicates in the formation. The stratigraphic distribution of REEs are also presented and considered.