Geochemistry of carbonaceous impactites from the Gardnos impact structure, Norway

Gilmour, I., French, B.M., Franchi, I.A., Abbott, J.I., Hough, R.M., Newton, J. and Koeberl, C. (2003) Geochemistry of carbonaceous impactites from the Gardnos impact structure, Norway. Geochimica et Cosmochimica Acta, 67(20), pp. 3889-3903. (doi:10.1016/S0016-7037(03)00213-8)

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Publisher's URL: http://dx.doi.org/10.1016/S0016-7037(03)00213-8

Abstract

The Gardnos impact structure in southern Norway is one of only two known impact structures (among similar to175) whose impactites contain significant amounts (typically 0.2-1.0 wt.%) of carbon, or 5 to 10 times the amount present in the target rocks; Sudbury, Canada is the other. This study extends a previous investigation of the geochemistry and petrology of Gardnos impactites (French et al., 1997) with additional sampling and a detailed investigation of the nature and possible origin of the carbonaceous material present. Two principal carbon components have been identified in Gardnos impactites: (1) impact-produced diamonds, 0.5 to 1 mum in size, with a cubic crystal structure, predominantly hexagonal morphologies with platey layers and an estimated concentration of lt 0.19 ppm in Gardnos suevites and (2) graphitic carbon ranging from poorly ordered to moderately crystalline. Geochemical data suggests that there are no suitable target rocks that could provide a single source for the carbon in Gardnos impactites. However, Raman spectroscopy, stable isotope analysis and transmission electron microscopy of the impact diamonds and graphitic carbon suggests that there were at least two episodes of C emplacement in Gardnos impactites: an impact- related incorporation and shock transformation of graphitic material from target rocks followed by later mobilization of C, possibly during postimpact cooling or later regional metamorphism.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Newton, Dr Jason
Authors: Gilmour, I., French, B.M., Franchi, I.A., Abbott, J.I., Hough, R.M., Newton, J., and Koeberl, C.
Subjects:Q Science > QE Geology
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Geochimica et Cosmochimica Acta
ISSN:0016-7037

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