A Magnetic Geothermometer in Moderately Buried Shales - Aix-Marseille Université Access content directly
Journal Articles Minerals Year : 2021

A Magnetic Geothermometer in Moderately Buried Shales

Myriam Kars
  • Function : Author
  • PersonId : 1141462
Jean-Pierre Pozzi
  • Function : Author
  • PersonId : 1131591
Martin Mazurek
  • Function : Author
  • PersonId : 1131592

Abstract

Shales contain magnetic minerals generally at very low concentrations. In the early stages of diagenesis, the inherited magnetic minerals are altered, while magnetic nanominerals are formed. In this study, we proposed a study of shales over a stratigraphic thickness of 1.3 km from a borehole in the Paris basin (Borehole EST 433, France), and shales from the same formation (Opalinus Clay) collected in seven boreholes in the Jura molasse basin (Swiss). Magnetic measurements at experimental temperatures <30 K allowed the formation of a proxy of magnetite nanograins named PM. We showed that some of these nanograins formed around the pyrite grains, probably under the action of temperature and organic matter. PM was then compared to the maturity values of the organic matter. We found a correlation between PM and the percentage of reflectance of vitrinite. The shales from both Paris and molassic Swiss basins showed very comparable magnetic characteristics for a given maturity level. The magnetic study therefore provided constraints on the maturity level of the shales in the oil window area. Our study showed that PM can be used as a geothermometer in shales in which CaCO3 is lower than 60%.
Fichier principal
Vignette du fichier
2021 Aubourg et al (Minerals).pdf (1.27 Mo) Télécharger le fichier
Origin Publisher files allowed on an open archive

Dates and versions

hal-03629197 , version 1 (04-04-2022)

Licence

Identifiers

Cite

Charles Aubourg, Myriam Kars, Jean-Pierre Pozzi, Martin Mazurek, O. Grauby. A Magnetic Geothermometer in Moderately Buried Shales. Minerals, 2021, 11, ⟨10.3390/min11090957⟩. ⟨hal-03629197⟩
26 View
32 Download

Altmetric

Share

Gmail Mastodon Facebook X LinkedIn More