Diagenetic Mobilization of Uranium and Iron from Red Beds of Catskill Formation in Eastern Pennsylvania: ABSTRACT

Abstract

The content of uranium, thorium, lanthanum, and major elements in 272 samples of clastic sedimentary rock from red beds of the Devonian Catskill Formation in eastern Pennsylvania varies with grain size and color (oxidation state). The samples were derived largely from fining-upward cycles in which sandstones, commonly gray to green, were deposited as channel fillings, while overlying shales, commonly red, were deposited as overbank muds. The contents of iron, aluminum, uranium, thorium, titanium, and lanthanum correlate negatively with grain size. Gray to green (reduced) shales and fine-grained sandstones have distinctly lower iron and higher uranium and uranium/thorium content than red (oxidized) sandstones and shales of the same grain size and the same aluminum content. The differences are greatest in shales. Thorium content does not vary with oxidation state. The levels of uranium, thorium, and iron in green shales are inferred to be approximately the amounts present in the original detritus. Gray sandstones have apparently lost iron and may have locally gained uranium probably by flow of reducing pore waters through the buried channels during early diagenesis. Red muds apparently lost uranium just after deposition because of strong oxidation and at least limited permeation by surface waters. The uranium lost from the red muds furnishes a probable source for uranium in roll-type uranium deposits found in sandstones in the area near Jim Thorpe, Pennsylvania. Recrystallization of amorphous iron oxides to hematite may have promoted the release of adsorbed uranium from the muds. End_of_Article - Last_Page 765------------