This study used Raman spectral analysis to characterise the structural order of carbon in three carbonaceous chondrites and twelve achondrites. The achondrites analysed were a group of carbon-rich meteorites, known as ureilites. These meteorites are composed primarily of olivine and pyroxene and have igneous textures but contain noble gases and primitive oxygen isotopes which appear to contradict their high temperature origin, which has led to the group being described as “enigmatic” by some authors. This study used Raman spectral analysis to show that ureilite carbon is heterogeneous, even at the micrometer scale, and is derived from more than one source. In order to better understand the processes involved in ureilite formation, terrestrial analogues containing carbonaceous material with similar spectral characteristics to the meteorites were identified. Analysis of terrestrial samples showed that the sedimentary carbon can be incorporated into igneous rocks with little structural change, suggesting that the same may be true for carbonaceous material in ureilites. Although the terrestrial carbon is biogenic in origin, it is structurally similar to pre-biotic organic matter found in meteorites. Carbon can be used as an effective tracer for geological events, such as melting and heating, which appear to be ubiquitous in planetary evolution. This study concluded that carbon is a primary component of melts on the ureilite parent body (UPB) and that impact processes have increased the heterogeneity of ureilite carbonaceous material. Carbon is likely to have been remobilised by later impact events, explaining the lack of correlation between carbon content and isotopic values with other geochemical parameters. Spectral analysis suggested that most of the carbon in ureilites is derived from primitive material.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:522236 |
| Date | January 2010 |
| Creators | Wright, Alison Jane |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=130931 |
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