The vanadium isotopic constitution of petroleum asphaltenes: La Luna Formation (Venezuela)

High-resolution mass spectrometry indicates that the isotopic abundance of V-50 Of the Late Cretaceous La Luna petroleum asphaltenes of marine origin (highly enriched with V > 2000 ppm)fi higher by about 3.5% than that of the inorganic source (VOSO4 X 5H(2)O, Merck). We propose that the difference i n the V-50/V-51 values between the La Luna petroleum asphaltenes and the in organic source can be best ascribed to the biological processing of seawate r vanadium. The fact that the V isotopic compositions of petroleum asphalte nes vary over avery narrow range (2.46-2.52) suggests essentially the same (or similar) and fixed biological source of vanadium. (C) 2000 Elsevier Sci ence Inc. All rights reserved.