Skip to Main content Skip to Navigation
Theses

Altération diagénétique et post-diagénétique (thermicité, oxydation) des charbons carbonifères du Massif Central français (Saint-Etienne, Graissessac et autres lieux)

Abstract : This work deals with some prominent properties of the organic matter (OM), such as its ability to record the thermal history of basins, (hydro)thermal events of more limited influence or oxidising processes. Two of these topics have been developed in the frame of the study of Carboniferous coals sampled in several basins in the Massif Central.
As a consequence of the tectonic regime that prevailed at the end of Hercynian orogenesis, thermal domes and even faults acting as conduits for hydrothermal fluids, have generated a heterogeneous hyperthermicity in the studied basins. Local coalification conditions such as Maximum Paleotemperatures of Burial (MPTB), paleoburial depths, durations of maturation, have been estimated.
A compilation of OM characteristic parameters suggests that some mature coals have been affected by a restricted hyperthermal activity, while others have solely recorded a simple oxidation.
Astonishingly, this latter process that occurred at low temperature, is characterised by an increase in Tmax (and a decrease in Hydrogen Index), which mimics a classical thermal degradation. This peculiar behaviour is reinforced both by the study of profiles of weathered mature coals and by oxidation experiments. The considered oxidation process consists in two successive reaction stages. The first is defined by a notable loss in hydrogen and a weak gain in oxygen, while the second, is characterised by a weak loss in hydrogen and a gain in oxygen. The increase in Tmax occurs at the beginning of the second stage, this later one being reached all the more faster than the raw coal is poor in hydrogen (i.e. has reached a high level of maturity). This alteration process preferentially affects the periphery of the carbon skeleton (Base Structural Units) by provoking the degradation of "thermolabile / oxilabile" functional groups. Hence, these features justify and explain the strong similarity evidenced between the effects of thermal and oxidising processes.
Complete list of metadata

https://tel.archives-ouvertes.fr/tel-00001902
Contributor : Nathalie Pothier <>
Submitted on : Wednesday, November 6, 2002 - 7:28:18 AM
Last modification on : Tuesday, December 24, 2019 - 1:27:01 AM
Long-term archiving on: : Tuesday, September 11, 2012 - 6:15:08 PM

Identifiers

  • HAL Id : tel-00001902, version 1

Citation

Yoann Copard. Altération diagénétique et post-diagénétique (thermicité, oxydation) des charbons carbonifères du Massif Central français (Saint-Etienne, Graissessac et autres lieux). Géologie appliquée. Université d'Orléans, 2002. Français. ⟨tel-00001902⟩

Share

Metrics

Record views

570

Files downloads

5999