LASERS IN ORGANIC PETROLOGY AND ORGANIC GEOCHEMISTRY .2. IN-SITU LASER MICROPYROLYSIS GCMS OF COAL MACERALS

The development and preliminary results of a novel laser micropyrolysi s-gas chromatography, mass spectrometry (LMPy-GCMS) system are describ ed. Short exposures of near-infra red (IR) laser radiation focused thr ough a microscope's optics onto a specific, targeted maceral within a polymaceralic organic-rich shale or coal are used to release the therm al evaporation and pyrolysis products from the maceral. The products f rom multiple exposures on a single maceral type are collectively analy zed on-line using GCMS. This technique is intended to provide a means of chemically characterizing individual, microscopic organic entities (> 25 mu m) in coals and shales without the need to physically separat e them from each other (e.g. density gradient centrifugation) or from their mineral matrix (e.g. bulk analysis of kerogen concentrates). Mol ecular characterization of individual macerals is important in predict ing the technological properties of coal and the petroleum generation potential of petroleum source rocks. Different macerals respond differ ently when exposed to focused near-IR laser radiation due to differenc es in their heat capacity and heat conduction. The thermal products re leased during irradiation of macerals (ulminite, alginite, sporinite a nd fusinite) representing the huminite, liptinite and inertinite macer al groups are presented. Under the appropriate heating, collecting, an d trapping conditions, the thermal products liberated are considered r epresentative of the macromolecular structure of the macerals. Structu ral elucidation of macerals in coals and shales could significantly be nefit from concerted efforts of this and other in-situ micro-analytica l techniques.