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

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

In: Meteoritics and Planetary Science, Vol. 42, No. 11, 11.2007, p. 1961-1969.

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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 and Planetary Science. 2007 ; Vol. 42, No. 11. pp. 1961-1969.

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TY - JOUR

T1 - Formation of uranium-thorium-rich bitumen nodules in the Lockne impact structure, Sweden

T2 - Meteoritics & Planetary Science

AU - Lindgren, Paula

AU - Parnell, John

AU - Norman, Craig

AU - Mark, Darren F.

AU - Baron, Martin

AU - Ormö, Jens

AU - Sturkell, Erik

AU - Conliffe, James

AU - Fraser, Wesley

PY - 2007/11

Y1 - 2007/11

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=41549141425&partnerID=8YFLogxK

U2 - 10.1111/j.1945-5100.2007.tb00553.x

DO - 10.1111/j.1945-5100.2007.tb00553.x

M3 - Article

VL - 42

SP - 1961

EP - 1969

JO - Meteoritics & Planetary Science

JF - Meteoritics & Planetary Science

SN - 1086-9379

IS - 11

ER -