Abstract
Elemental analysis, X-ray diffraction, infrared absorption and electron spin resonance have been used to characterize the kerogens from the Miocene muddy rocks between 500 and 4500m in depth obtained from the MITI Hamayuchi Borehole in the northern part of Hokkaido. The progressive maturation of the kerogen properties observed were discussed, compared with the data of the extractable organic matter in the same samples which had been already reported by ATAKE (1973) and ASAKAWA (1975).
The results are as follows:
1) The kerogens are clearly classified into two definite groups in C-H-O composition, one being more than 79% in carbon content from the samples deeper than 3200m in depth and the other less than 75% from those shallower than 2100m.
2) X-ray diffraction spectra of all of these kerogens correspond to "graphite-d3" of LANDIS' classification (1971).
3) Infrared absorption analyses suggest that the ratios of absorption intensity of C=O at 1700cm-1 to aromatic C=C at 1600cm-1 could be a useful parameter to identify the kerogen maturation.
4) ESR measurements could be also a useful tool for estimating kerogen maturity only for the deeply buried kerogens.
5) Maturity of kerogens increases progressively with an increase of the concentration and maturity of the extractable organic matter included at the depth of 2000-3400m from the surface. This evidence suggests the extractable organic matter in the muddy rocks originates from the breakdown of hydrocarbon side chains of kerogens by natural pyrolysis during diagenesis.
