Selenium and tellurium enrichment in palaeo-oil reservoirs

• Se and Te can become enriched in rocks containing palaeo-oil charges.
• The Se and Te are concentrated within sulfides.
• Precipitation of the sulfides was microbially mediated during oil degradation.

The exploration for selenium (Se) and tellurium (Te) will become intensified as the technological demand for these elements grows. It is known that they are enriched in organic-rich sedimentary rocks over crustal mean values. LA-ICP-MS measurement of pyrite in two biodegraded palaeo-oil reservoirs in central England shows that Se and Te are enriched in them, but not in other sulfide samples from the region and elsewhere. The Carboniferous source rock shales in the region are Se-rich, implying that this enrichment was conferred to the oil generated from them. The Se and Te are located in pyrite precipitated in the palaeo-reservoirs by microbial activity. Exhumed oil reservoirs merit further investigation for concentrations of these elements.