Association of organic matter and vanadium in oil shale from the Toolebuc Formation of the Eromanga Basin, Australia

Vanadyl porphyrins have been detected in a series of oil shale and weathered coquinite samples from the Toolebuc Formation, Queensland, Australia. Concentrations of soluble vanadyl porphyrins range from < 1 to 730 μg g −1. Organically bound vanadium has also been found in kerogens isolated from oil-shale samples taken at locations up to several hundred kilometres apart. Variations in the concentration of both vanadyl porphyrins and kerogen-bound V are probably due to recent weathering. By preferentially removing smaller aliphatic molecules, weathering progressively renders the remaining kerogen more aromatic and ultimately solubilizes all organic matter in the shales. At the same time, organically bound V is released and becomes associated with the inorganic fraction of the weathered shale.