Experimental controls on D/H and C-13/C-12 ratios of kerogen, bitumen and oil during hydrous pyrolysis

Large isotopic transfers between water-derived hydrogen and organic hydroge n occurred during hydrous pyrolysis experiments of immature source rocks, i n spite of only small changes in organic C-13/C-12. experiments at 330 degr eesC over 72 h using chips or powder containing kerogen types I and III ide ntify the rock/water ratio as a main factor affecting Delta deltaD for wate r and organic hydrogen. Our data suggest that larger rock permeability and smaller rock grain size increase the H-isotopic transfer between water-deri ved hydrogen and thermally maturing organic matter. Increasing hydrostatic pressure may have a similar effect, but the evidence remains inconclusive. (C) 2001 Elsevier Science Ltd. All rights reserved.