ESTERLE, JOAN S., CSIRO, -Division of Geomechanics, Kenmore, Queensland; MARC BUSTIN, Department of Geology, University of British Columbia, Vancouver; and ARTUR STANKIEWICZ, Department of Geology, Southern Illinois University, Carbondale, IL

ABSTRACT: Rock-Eval Pyrolysis of Cold-Temperature and Tropical Peats and Coal: What is Generated and When

Rock-eval pyrolysis was used to examine differences in hydrocarbon content of woody and herbaceous peat types in two Holocene deposits from cold temperate South Island, New Zealand and tropical Sarawak, Malaysia. Almost all peat types were pre-vitrinite rich (80 to 95%), with low (<5%) ash contents and vitrinite reflectances ranging from .23 to .40, depending on decomposition state. S1 peaks ranged from 4 to 59, S2 from 49 to 230, S3 from 29 to 126 mg HC/gm; TMax ranged from 389 to 423 C. On a HI/OI plot, all peats straddled above the Type III kerogen line. Results were compared to rock-eval data from older NZ "waxy" peats and Tertiary coals. No significant trends occurred between peat types, but significant differences occurred between the peats and coals. All peats contained more free hydrocarbon (S1) and CO2 (S3) than the coal, but less pyrolyzable hydrocarbon (S2) (lignite the exception). Some peats were "more mature" than the lignite. On a plot of S1 vs S1+S2, all peats show a direct correlation, but the coals show no correlation and fall beneath the 10 mg HC/gm S1 line. The drop in free hydrocarbons (from 5-60 to <10) from peat to coal suggests an abundance of easily generated hydrocarbons are lost during early burial and before thermal maturation. The composition of these hydrocarbons is being examined by Pyrolysis GC-MS.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.