Hydrocarbons isolated from hydrothermal anhydrite, chalocopyrite, and sphalerite-enriched samples from the mid-Atlantic Ridge exhibit a high degree of thermal maturation, compared to a Fe-oxide-enriched sample, as evidenced by the high abundane of low molecular weith n-alkanes ranging from C14 to C25 with a broad distribution of naphthenes. These trace hydrothermally-derived petroleums contain some polycyclic aromatic hydrocarbons (PAH) and very low amounts of typical biomarkers (e.g., steroid hydrocarbons, triterpanes). The low levels of biomarkers may be due to removal by hydrothermal conversion to other products (e.g., aromatics) or have not yet formed. The Fe-oxide-enriched sample has a lower content of PAH than the other mineral samples; however, benzopyrenes and coronene are present at a significant level, and a series of mature triterpanes is also detectable. The loss of the lower molecular weight PAH in the Fe-oxide-enriched sample could be due to dissolution/oxidation processes. The presence of trace levels of petroleum strongly suggest its generation from contemporary organic detritus by hydrothermal activity and subsequent association with the minerals. ¿ American Geophysical Union 1989