Peridotite xenoliths which are thought to sample the upper mantle sometimes contain supra-chondritic Os-isotopic ratios.Over the years, Chemostrat has expanded the services on offer to now include more advanced isotopic techniques that so far have been used only in academia.Furthermore, as Re and Os have been inherited from the source rocks, Os isotopes can be employed to correlate an oil with its source.Re - Os dating and oil - source rock correlation is actually helped if the oils are highly biodegraded, e.g., oil sands, tar mats and bitumen-stained sandstones (where traditional techniques such as biomarker identification are disrupted), as this concentrates Re and Os within an oil making analysis easier.Organic-rich muds are a significant crustal reservoir of Re & Os with concentrations of up to 300 ppb of Re and 3 ppb of Os, more than two orders of magnitude higher than the average crustal abundance (Creaser et al., 2002).
When oil is formed from a source rock, a proportion of the Re and Os from the source rock is transferred to the oil, thus one can date the formation process using the Re - Os geochronometer.Thus the two elements should be depleted in the silicate Earth yet the The reason for this apparent contradiction is owed to the change in behavior between Re and Os in partial melt events.Re tends to enter the melt phase (incompatible) while Os remains in the solid residue (compatible).The Re - Os technique can also be utilised to date the formation of sulphide minerals.Reliable dating of sediments has several applications in petroleum systems analysis (PSA), such as improving our basin models (e.g. While biostratigraphy can be a very useful qualitative technique for dating sediments, issues can arise where fossil assemblages are strongly facies- or province-dependant.subsidence rates) and geochemical interpretations (e.g. Radiogenic dating is routinely applied to inorganic rocks to determine the absolute age of deposition (e.g. granites), but is less commonly applied to organic-rich sediments such as source rocks.