Evidence for pervasive petroleum generation and migration in 3.2 and 2.63 Ga shales

Research Article| June 01, 2005 Evidence for pervasive petroleum generation and migration in 3.2 and 2.63 Ga shales Birger Rasmussen Birger Rasmussen 1School of Earth and Geographical Sciences, University of Western Australia, Crawley, WA 6009, Australia Search for other works by this author on: GSW Google Scholar Geology (2005) 33 (6): 497–500. https://doi.org/10.1130/G21316.1 Article history received: 25 Oct 2004 rev-recd: 25 Jan 2005 accepted: 31 Jan 2005 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Birger Rasmussen; Evidence for pervasive petroleum generation and migration in 3.2 and 2.63 Ga shales. Geology 2005;; 33 (6): 497–500. doi: https://doi.org/10.1130/G21316.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Petroleum generation largely occurs through the thermal decomposition of organic matter. The presence of oil-bearing fluid inclusions and pyrobitumen in Archean rocks suggests that similar processes operated as early as ca. 3.25 Ga. However, direct evidence of petroleum generation from potential source rocks is lacking, and an abiogenic origin has been proposed for some Archean carbonaceous residues. Pilbara craton ca. 3.2 Ga and ca. 2.63 Ga black shales were found to contain abundant kerogenous streaks and laminae, as well as bitumen nodules (comprising a radioactive mineral core surrounded by a carbonaceous rim) and pyrobitumen (formerly petroleum) globules, films, and aggregates. The bitumen nodules formed around detrital radioactive grains via polymerization of fluid hydrocarbons generated within the shale and represent diagnostic indicators of oil generation in ancient shales. The bitumen globules, films, and masses are preserved within authigenic pyrite and demonstrate that a separate hydrocarbon phase had developed in the shale matrix during burial, providing compelling evidence for in situ petroleum generation and expulsion. The abundance of bitumen nodules and residual pyrobitumen in black shales across the Pilbara craton suggests that hydrocarbon generation from kerogenous shales was a common phenomenon during the Middle to Late Archean. The petroleum was generated from organic matter that accumulated in marine environments, most probably comprising the remains of photosynthetic and chemosynthetic organisms, pointing to a sizeable biomass as early as 3.2 Ga. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.