Trace element and isotopic analysis by laser ablation ICP-MS of ore deposit bitumens: A test case with uranium ores from Oklo, Gabon

Carbonaceous substances (CS) such as kerogen and derivative bitumens are cl osely linked to the origin of various types of ore deposits. Examples are m etal accumulations in living organisms, black shales, crude oils, solid bit umens, and coals. Although presently a marginal economic proposition, the u ranium ores of Oklo provide a classic case. At Oklo, solid bitumen occurs c losely associated with the several main uranium ore types and also as discr ete veinlets in the 2.1 Ga old country rock shales. These bitumen occurrenc es have been distinguished on the basis of Weld evidence, petrography, carb on isotopic signatures, and degree of thermal maturation. Chemical analysis by laser ablation inductively coupled plasma-mass spectrometry (ICP-MS) no w allows detailed chemical characterization of CS such as these solid bitum ens. For the first time, the technique has been used to produce quantitativ e in situ trace element and isotopic analysis of bitumen. There is a potent ial here to make major contributions to the understanding of Oklo and other ore deposits associated with carbonaceous substances.