Vanadyl ions in ancient marine carbonaceous sediments

Vanadyl ions in ancient shaly-type sedimentary rocks of marine origin from a variety of world sources and geological periods have been investigated using electron spin resonance. These and other results provide evidence that there are two types of vanadyl ions. The first is inorganically bound in the clay/ silicate fraction of these rocks and the second type is associated with vanadyl porphyrin compounds.