Optical thermal maturity parameters and organic geochemical alteration at low grade diagenesis to anchimetamorphism: A review

Sedimentary organic matter derives from biological precursor material which undergoes systematic, irreversible changes upon burial which mainly reflect increasing diagenetic temperatures, although other factors have also an influence. Several parameters have been established in the last decades to determine the palaeotemperature history of sedimentary rocks based on geochemical or petrographical methods. Organic matter is the most temperature-sensitive solid constituent in sedimentary rocks and vitrinite reflectance (VR), miospore and conodont colour alteration are among the most widely used optical maturity parameters. Despite tremendous interest in estimating maturity parameters in the oil generation zone as well as for high grade diagenesis and metamorphism and despite decades of research only a few of these methods have been well established and compared to each other by now. The focus of this review is on some new aspects with respect to organic matter maturation and optical palaeotemperature parameters, especially for high grade diagenesis and anchimetamorphism. Such a discussion might be a prerequisite for a better understanding of palaeotemperature assessments in different sedimentological and/or geotectonic settings and useful for different fields in applied sciences. Furthermore, suggestions for further research are discussed. (C) 2015 Elsevier B.V. All rights reserved.