From twelve samples of WA oil studied, only three returned the results because of quite low Re-Os abundances in separated asphaltines, in a range of up to 1 ppb for rhenium and tens of ppt for osmium. This is quite low compare to Canadian oils, which usually show about an order of magnitude higher abundances of these metals. Higher Re and Os contents in Canadian oils correlate with markedly higher nickel and vanadium abundances.
Our preliminary data show a good fit with the basin ages using geologically reasonable initial Os ratios varying from depleted mantle-like ratio of for Ordovician samples to the more evolved ratio of , corresponding to the Os isotopic composition of Late Devonian seawater. Interestingly, the Ordovicial oil from Canning basin show more depleted source according to carbon isotope composition (~-31‰δ¹³C) as well, trending towards more enriched marine compositions for Devonian-Carboniferous parts of the basin (-27 to -29‰δ¹³C). As a conclusion, the study involving more samples shows a good potential for both geochronology and source fingerprinting of WA oils.