Journal of Petroleum Geology, Vol.4, No.4, pp. 437-439, 1982

©Copyright 2000 Scientific Press, Ltd.

EVIDENCE THAT STABLE CARBON ISOTOPES ARE NOT A RELIABLE CRITERION FOR DISTINGUISHING BIOGENIC FROM NON-BIOGENIC PETROLEUM

A. A. Giardini* and Charles E. Melton**

Departments of Geology* and Chemistry**, University of Georgia, Athens, GA, 30602, USA.

Abstract

The isotopic abundance of presumably-pristine primordial carbon has been determined by analyzing carbon dioxide entrapped in a 8.65 carat natural diamond of African origin. The results were ¹²C = 98.9275% and ¹⁴C = 1.0725%, which give ¹³C = -35.2 0/00. This value is well within the range used to assign a biogenic origin to carbon-containing compounds, i.e., more negative than -18.0 0/00. Similar negative values have been reported for some natural diamonds and carbon-bearing meteorites. It is concluded, therefore, that stable carbon isotopes can be an unreliable criterion for assigning a biogenic origin to petroleum.