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

Lindgren, Paula LU ; Parnell, John; Norman, Craig; Mark, Darren F.; Baron, Martin; Ormö, Jens; Sturkell, Erik; Conliffe, James and Fraser, Wesley (2007) In Meteoritics and Planetary Science 42(11). p.1961-1969
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... (More)

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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author
publishing date
type
Contribution to journal
publication status
published
subject
in
Meteoritics and Planetary Science
volume
42
issue
11
pages
9 pages
publisher
Wiley-Blackwell
external identifiers
  • scopus:41549141425
ISSN
1086-9379
DOI
10.1111/j.1945-5100.2007.tb00553.x
language
English
LU publication?
no
id
27477ed3-effe-4e39-b9a6-7b6da9e91a49
date added to LUP
2017-06-26 10:04:42
date last changed
2018-01-10 14:36:18
@article{27477ed3-effe-4e39-b9a6-7b6da9e91a49,
  abstract     = {<p>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.</p>},
  author       = {Lindgren, Paula and Parnell, John and Norman, Craig and Mark, Darren F. and Baron, Martin and Ormö, Jens and Sturkell, Erik and Conliffe, James and Fraser, Wesley},
  issn         = {1086-9379},
  language     = {eng},
  number       = {11},
  pages        = {1961--1969},
  publisher    = {Wiley-Blackwell},
  series       = {Meteoritics and Planetary Science},
  title        = {Formation of uranium-thorium-rich bitumen nodules in the Lockne impact structure, Sweden : A mechanism for carbon concentration at impact sites},
  url          = {http://dx.doi.org/10.1111/j.1945-5100.2007.tb00553.x},
  volume       = {42},
  year         = {2007},
}