The Open UniversitySkip to content
 

Halite and stable chlorine isotopes in the Zag H3-6 breccia

Bridges, J.C.; Banks, D.A.; Smith, M. and Grady, M.M. (2004). Halite and stable chlorine isotopes in the Zag H3-6 breccia. Meteoritics and Planetary Science, 39(5) pp. 657–666.

Full text available as:
[img]
Preview
PDF (Not Set) - Requires a PDF viewer such as GSview, Xpdf or Adobe Acrobat Reader
Download (582Kb)
URL: http://www.ingentaconnect.com./content/arizona/map...
Google Scholar: Look up in Google Scholar

Abstract

Zag is an H3-6 chondrite regolith breccia within which we have studied 14 halite grains ?3mm. The purity of the associated NaCl-H2O brine is implied by freezing characteristics of fluid inclusions in the halite and EPMA analyses together with a lack of other evaporite-like phases in the Zag H3-6 component. This is inconsistent with multistage evolution of the fluid involving scavenging of cations in the Zag region of the parent body. We suggest that the halite grains are clastic and did not crystallise in situ. Halite and water-soluble extracts from Zag have light Cl isotopic compositions, ?37-Cl = -1.4 to '2.8 �. Previously reported bulk carbonaceous chondrite values are approximately ?37-Cl = +3 to +4 �. This difference is too great to be the result of fractionation during evaporation and instead we suggest that Cl isotopes in chondrites are fractionated between a light reservoir associated with fluids and a heavier reservoir associated with higher temperature phases such as phosphates and silicates. Extraterrestrial carbon released at 600 degrees Celsius from the H3-4 matrix has ?13-C = -20 �, consistent with poorly graphitised material being introduced into the matrix rather than indigenous carbonate derived from a brine. We have also examined 28 other H-chondrite falls in order to ascertain how widespread halite or evaporite-like mineral assemblages are in ordinary chondrites. We did not find any more to add to Zag (H3-6) and Monahans (H5), which suggests that such highly soluble phases were not usually preserved on the parent bodies.

Item Type: Journal Article
ISSN: 1086-9379
Academic Unit/Department: Science > Physical Sciences
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 72
Depositing User: Users 12 not found.
Date Deposited: 09 May 2006
Last Modified: 21 Jan 2011 10:08
URI: http://oro.open.ac.uk/id/eprint/72
Share this page:

Actions (login may be required)

View Item
Report issue / request change

Policies | Disclaimer

© The Open University   + 44 (0)870 333 4340   general-enquiries@open.ac.uk