THE NEODYMIUM ISOTOPE SYSTEM AS A TOOL FOR PETROLEUM-EXPLORATION

Mineralogical, petrological, geochemical, and neodymium isotopic inves tigations strongly suggest isotopic and chemical exchange between auth igenic silicate phases and petroleum. Alteration of organic matter, su lfur reduction, generation of aqueous-acidic solutions with the result ant dissolution of K-feldspar leads to in situ crystallization of illi te and chlorite as well as neodymium isotopic equilibration between th e silicate phases and petroleum. These findings are of significance no t only to understand the mechanisms leading to neodymium isotopic equi libration between authigenic clay minerals in detrital sediments but a lso to source rock-petroleum (in reservoir) correlations, in particula rly when biomarker molecules (i.e., isoprenoid hydrocarbons) have been obliterated by prolonged, severe diagenesis.