ELUCIDATION OF THE ALUM-SHALE KEROGEN STRUCTURE USING A MULTIDISCIPLINARY APPROACH

The significance and validity of integrating data obtained from a vari ety of analytical techniques to understand, elucidate and model keroge n's complex chemical structure is reported here using degradative (ope n and closed system pyrolysis, chemical oxidation), non-degradative (C -13 CP/MAS NMR) and optical (incident white light and blue light) meth ods. Seven Cambrian Alum Shale samples, ranging in maturity from immat ure to post-mature with respect to petroleum generation, were studied and were chosen for their simple geological history, uniform organic m atter type and high organic carbon content. The Alum Shale kerogens, w hich primarily consist of algal organic matter, liberate low molecular weight gaseous and aromatic compounds on pyrolysis and give mostly br anched dicarboxylic acids on chemical oxidation. C-13 NMR spectroscopy shows that the Alum Shale kerogens are anomalously rich in oxygen-bea ring functional groups (such as C = O, ArCO, CHO, CHxO), most of which apparently remain intact within the kerogen macro-molecule (KMM) thro ugh the diagenetic and catagenetic stages. Fragments released by diffe rent degradative techniques are quantified and the aromaticity (f(a)), O/C and relative proportions of various carbon types estimated by C-1 3 NMR. A synthesis of these data has allowed us to better understand t he chemistry of the Alum Shale kerogen. (C) 1996 Elsevier Science Ltd