Factors affecting trace elements enrichment and its interaction with organic materials in Qalikouh oil shale, Lorestan, western Iran

Qalikouh anticline is located 35 km southwest of Aligudarz city, Lorestan province, SW of Iran. The area is located in the high structural zone of Zagros. The oil shales of the areas are located in the Middle Jurassic and Lower Triassic of Sargelu and Garu Formations. The Sargelu Formation contains a series of shale, carbonate, oil shale, and clays. Garau Formation includes oil shale horizons with different thicknesses, ammonite shales, and black cherty layer. The shales of these two formations in the high Zagros region have formed oil shale reserves due to their richness in organic matter (OM), kerogen type is I and II, and relatively low thermal maturity at the beginning of the oil window. This study focuses on the effect of geochemical processes on the enrichment of trace elements and their interaction with organic matter in Qalikouh oil shale. analysis was performed by XRF, XRD, ICP-Ms, and Rock-Eval methods and Statistical significance were analyzed. The results of this study indicated the high enrichment of elements Cd, Mo, Ag, U, Cs. The correlation between immobilized and mobile oxides, organic matter, formed minerals, and other factors were tested. These tests revealed that the enrichment of trace elements is affected by classical, biological, and autogenic materials. Elements U, V, Cd are related to the organic and autogenic matter. Elements Ca, Si, P is of biological origin, and elements Ag, Ti are of classical origin.