Effect of igneous activity on molecular-maturation indices in different types of organic matter

Naphthalenes in Neogene sediments of the Shinjo basin, Japan.

“…The ratio varies from 0.7 to 1.4 and shows no depth dependence. The methylnaphthalene parameter has been reported to be around one in coals or sediments with the vitrinite reflectance from 0.5 to 1.5% and in many cases to show scattered plots against depth of samples (Radke et al, 1982a(Radke et al, , 1984Raymond and Murchison, 1992), being similar to our results obtained here. In our separate experiments, the samples 83106, 83103 and 90103 were heated at 300°C for 48 h and the time-course of the ratio was determined by the same analytical procedure as used in this study (details of this experiment will be published elsewhere).…”

Estimation and application of the thermodynamic properties of aqueous phenanthrene and isomers of methylphenanthrene at high temperature

“…George (1992) studied a siltstone and oil shale affected by igneous intrusions in the Midland Valley of Scotland and found values of MPR that increase, then decrease at closest approach to a dyke and a sill. In another study of samples from the Midland Valley, Raymond and Murchison (1992) found ratios of alkylated naphthalenes and phenanthrenes in rapidly heated zones that at first increased, then decreased at higher maturities. A reversal of MPI-1 was apparent by R o ≈ 2.0%, but MPR did not decrease up to the highest reported R o = 3.5%.…”

“…Reversals in methylation patterns for hopanes and triterpanes at high temperature have been reported (Schwab et al, 2005;Raymond and Murchison, 1992), as have reversals or values that are lower than expected for high maturities for maturity parameters based on the stereochemistry of hopanes and steranes (Strachan et al, 1989;Davies, 1997;Arouri et al, 2000), including some examples near igneous intrusions Abbott, 1993, 1995;Othman et al, 2001). The behavior of these and other biomarker ratios is not considered further in this study, but our results suggest that a thermodynamic analysis of the relative stabilities of the biomarkers at high temperature could offer an explanation for some of the reversals that are usually considered to be anomalous.…”

“…Price (1993) reported the presence of naphthalene and biphenyl at 450 • C in aqueous-pyrolysis experiments and predicted that aromatic hydrocarbons might be found at low concentrations at higher temperatures, possibly preserved as inclusions in minerals that have undergone the early stages of rock metamorphism, potentially making organic compounds useful as geothermobarometers. Indeed, the relative abundances of specific aromatic compounds, known as maturity parameters, can be used to infer effects of past igneous and hydrothermal activity on organic-rich systems (George, 1992) and the history of possible ore-forming fluids (Püttmann et al, 1989;Chen et al, 2003;Mackenzie et al, 2008;Williford et al, 2011), but observed reversals or unexpectedly low values of these ratios at high maturity and/or temperature (George, 1992;Raymond and Murchison, 1992;Bechtel et al, 1995;Brocks et al, 2003a, and others) are not accounted for by existing theoretical models. The goal of the present study is to better understand the applications of the aromatic maturity ratios of phenanthrene (P) and methylphenanthrene (MP) in hydrothermal systems by estimating the high-temperature standard Gibbs energies of the species involved and comparing predictions made by thermodynamic calculations with published observations.…”

Biomarker Distributions as Maturity Indicators in Coals, Coaly Shales, and Shales From Taiwan

“…The deviation of the ratio from the equilibrium to lower values is attributed to a high heating rate during maturation (Lu et al 1989;Abbott et al 1990;Peters et al 1990;Raymond and Murchison 1992;Bishop and Abbott 1993;Requejo Fig. 5.…”