Abstract: The present invention relates to the field of organic geochemistry wherein a method for accessing high molecular mass aromatic hydrocarbons and diamondoids was developed from comprehensive characterization carried out by high resolution spectrometry coupled with the atmospheric pressure photoionization source (APPI FT-ICR MS). Based on the compositional profile of diamondoids and aromatic hydrocarbons, it is possible to quickly and robustly classify oils in relation to their origin and thermal evolution. It is verified that the compositional detail provided by the APPI(+)-FT-ICR MS analysis allowed the development of new molecular indicators, accessed without the need for any preliminary separation technique, in order to become a powerful tool for prospecting the use of oils exploited for specific purposes.