Solid bitumen occurrences in the Arruda sub-basin (Lusitanian Basin, Portugal): Petrographic features

• Type: Article in International Scientific Journal
• Date: 2014

Authors

Paula Alexandra Goncalves (Author) FCUP; Joao Graciano Mendonca Filho (Author) Other; Frederico Sobrinho da Silva (Author) Other; Deolinda Flores (Author) FCUP

Journal

Title: International Journal of Coal Geology

Vol. 131

Pages: 239-249

ISSN: 0166-5162

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 18 Citations

Scopus - 20 Citations

Scientific classification

FOS: Engineering and technology > Environmental engineering

Other information

Authenticus ID: P-009-PA6

DOI: 10.1016/j.coal.2014.06.023

Abstract (EN): The Middle Jurassic to Cretaceous sedimentary record in the Lusitanian Basin (Portugal) reveals the presence of disseminated solid bitumen. The present work is focused on the petrographic characteristics of solid bitumen identified in the Freixial-1 and Benfeito-1 boreholes (Arruda sub-basin, Lusitanian Basin) that display different thermal maturities. Microscopy techniques (reflected and transmitted white light, incident blue light and SEM) and organic geochemistry analyses (total organic carbon, total sulfur and insoluble residue) were used to study these samples. From the results obtained by optical microscopy (fluorescence and reflectance) it was possible to distinguish three types of solid bitumen. They were labeled as solid bitumen A, present in all the samples, solid bitumen B and solid bitumen C, these ones observed in some of them. They correspond to allochthonous (migrated) bitumens. In blue incident light, some bitumen do not show fluorescence while others reveal fluorescence that range from yellow (solid bitumen B) to dark brown (solid bitumen A). All bitumens are optically isotropic. Bitumen reflectance varies between 0.70 and 2.60% R-r, and the vitrinite reflectance ranges from 1.11 to 1.48% R-r. Based on the % R-r values, the solid bitumen identified in these samples are classified as impsonite (epi- and cata-) or pyrobitumen. No relation can be established with confidence for the reflectance of bitumens with the reflectance of vitrinite.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 11