Hydrothermal generation of hydrocarbons in basement rocks, Southern Tuscany

Andrea Schito* (Corresponding Author), David Muirhead, Stephen Bowden, John Parnell

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Carbonaceous material in the form of graphitic carbon, amorphous carbon and liquid hydrocarbons occurs in the metamorphic rocks of Monti Romani in Southern Tuscany. Raman spectroscopic analyses show a contrast in structural ordering between carbon in the host rocks and carbon films and nodules at the contact with high temperature mineralized veins. Microscopy and gas chromatography additionally indicate liquid hydrocarbons, with a thermal maturity at the peak of the oil window. The association of hydrocarbons with high temperature fluids together with gas chromatographic and spectroscopic data indicate a probable hydrothermal origin of the oils, from the late Miocenic sediments that fill the Tafone Graben. A model is proposed in which hydrocarbons were generated along the fault that borders the Tafone Graben and then migrated toward the basements rocks at the footwall. The presence of 25-norhopane indicates biodegradation in the depth interval between about 100 and 1500 m. The hydrothermal generation of hydrocarbons could occur in other geothermal areas in Southern Tuscany where the presence of hydrocarbons has been reported but never fully explained.
Original languageEnglish
Pages (from-to)231-244
Number of pages14
JournalItalian Journal of Geosciences
Volume141
Issue number2
Early online date26 Apr 2022
DOIs
Publication statusPublished - 26 Apr 2022

Keywords

  • hydrothermal hydrocarbons
  • basement rocks
  • Raman spectroscopy
  • fluid inclusions
  • biomarkers

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