Formation of uranium-thorium-rich bitumen nodules in the Lockne impact structure, Sweden: A mechanism for carbon concentration at impact sites

Paula Lindgren, John Parnell, Craig Norman, Darren F. Mark, Martin Baron, Jens Ormö, Erik Sturkell, James Conliffe, Wesley Fraser

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

The Ordovician Lockne impact structure is located in central Sweden. The target lithology consisted of limestone and black unconsolidated shale overlaying a Precambrian crystalline basement. The Precambrian basement is uranium-rich, and the black shale is both uranium- and organic-rich. This circumstance makes Lockne a good candidate for testing the occurrence of U-Th-rich bitumen nodules in an impact structure setting. U-Th-rich bitumen nodules are formed through irradiation; hence the increase in the complexity of organic matter by a radioactive (uranium- and thorium-rich) mineral phase. U-Th-rich bitumen nodules were detected in crystalline impact breccia and resurge deposits from the impact structure, but samples of non-impact-affected rocks from outside the impact structure do not contain any U-Th-rich bitumen nodules. This implies that in the Lockne impact structure, the nodules are associated with impact-related processes. U-Th-rich bitumen nodules occur throughout the geological record and are not restricted to an impact structure setting, but our studies at Lockne show that this process of irradiation can readily occur in impact structures where fracturing of rocks and a post-impact hydrothermal system enhances fluid circulation. The irradiation of organic matter by radioactive minerals has previously been proposed as a process for concentration of carbon on the early Earth. Impact structures are suggested as sites for prebiotic chemistry and primitive evolution, and irradiation by radioactive minerals could be an important mechanism for carbon concentration at impact sites.

Original languageEnglish
Pages (from-to)1961-1969
Number of pages9
JournalMeteoritics & Planetary Sciences
Volume42
Issue number11
DOIs
Publication statusPublished - Nov 2007

Keywords

  • archean granites
  • organic matter
  • ore deposits
  • parry sound
  • mineralization
  • sandstones
  • petroleum
  • basin
  • Mars
  • thucholite
  • organic-matter
  • ore-deposits
  • parry-sound
  • mars

Cite this

Formation of uranium-thorium-rich bitumen nodules in the Lockne impact structure, Sweden : A mechanism for carbon concentration at impact sites. / Lindgren, Paula; Parnell, John; Norman, Craig; Mark, Darren F.; Baron, Martin; Ormö, Jens; Sturkell, Erik; Conliffe, James; Fraser, Wesley.

In: Meteoritics & Planetary Sciences, Vol. 42, No. 11, 11.2007, p. 1961-1969.

Research output: Contribution to journalArticle

Lindgren, Paula ; Parnell, John ; Norman, Craig ; Mark, Darren F. ; Baron, Martin ; Ormö, Jens ; Sturkell, Erik ; Conliffe, James ; Fraser, Wesley. / Formation of uranium-thorium-rich bitumen nodules in the Lockne impact structure, Sweden : A mechanism for carbon concentration at impact sites. In: Meteoritics & Planetary Sciences. 2007 ; Vol. 42, No. 11. pp. 1961-1969.
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abstract = "The Ordovician Lockne impact structure is located in central Sweden. The target lithology consisted of limestone and black unconsolidated shale overlaying a Precambrian crystalline basement. The Precambrian basement is uranium-rich, and the black shale is both uranium- and organic-rich. This circumstance makes Lockne a good candidate for testing the occurrence of U-Th-rich bitumen nodules in an impact structure setting. U-Th-rich bitumen nodules are formed through irradiation; hence the increase in the complexity of organic matter by a radioactive (uranium- and thorium-rich) mineral phase. U-Th-rich bitumen nodules were detected in crystalline impact breccia and resurge deposits from the impact structure, but samples of non-impact-affected rocks from outside the impact structure do not contain any U-Th-rich bitumen nodules. This implies that in the Lockne impact structure, the nodules are associated with impact-related processes. U-Th-rich bitumen nodules occur throughout the geological record and are not restricted to an impact structure setting, but our studies at Lockne show that this process of irradiation can readily occur in impact structures where fracturing of rocks and a post-impact hydrothermal system enhances fluid circulation. The irradiation of organic matter by radioactive minerals has previously been proposed as a process for concentration of carbon on the early Earth. Impact structures are suggested as sites for prebiotic chemistry and primitive evolution, and irradiation by radioactive minerals could be an important mechanism for carbon concentration at impact sites.",
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