| Abstract: | Atmospheric Ne, Ar, Kr and Xe are observed in fluids occurring in deep basins. Modifications of their abundance patterns reveal modes of recharge and brine formation, phase separations during boiling, and association of natural gas with water or oil. Radiogenic 4He and 40Ar serve as age indicators of entrapped fluids, effective over a significant portion of the geological time scale. Simultaneous application of δ13C, atmospheric noble gases and radiogenic 4He and 40Ar, is recommended to identify: (a) recent bacterial natural gas formation, not accompanied by oil, and (b) natural gas formed along with oil in a mature source rock. |
