Grady, M. M.

Koehler, M.

Menzies, O. N.

Morlok, A.

English

Open Research Online 

Open Research OnlineThe Open University’s repository of research publicationsand other research outputsMid-infrared spectroscopy of CAI and their mineralcomponentsConference or Workshop ItemHow to cite:Morlok, A.; Koehler, M.; Menzies, O. N. and Grady, M. M. (2004). Mid-infrared spectroscopy of CAI andtheir mineral components. In: Chondrites and the Protoplanetary Disk, 8-11 Nov 2004, Kaua’i, Hawai’i.For guidance on citations see FAQs.c© [not recorded]Version: [not recorded]Link(s) to article on publisher’s website:http://www.lpi.usra.edu/meetings/chondrites2004/pdf/9023.pdfCopyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyrightowners. For more information on Open Research Online’s data policy on reuse of materials please consult the policiespage.oro.open.ac.ukMID-INFRARED SPECTROSCOPY OF CAI AND THEIR MINERAL COMPONENTS.  A. Morlok1,4; M. Koehler2,4; O.N.Menzies3,4; M. M. Grady1,4 1Department of Mineralogy, The Natural History Museum, Cromwell Road, London SW7 5BD, e-mail A.Morlok@nhm.ac.uk 2Institut fuer Planetologie, Wilhelm-Klemm-Str.10, 48149 Muenster, Germany 3Imperial College London, South Kensington Campus, SW7 2AZ 4IARC  Introduction:  Calcium-aluminium rich inclusions (CAI) represent highly refractory materials formed very early in the history of our solar system. As such, infrared spectra taken from their components and min-erals are of interest for the search of mineral phases in astronomical spectra of circumstellar discs of young stars. Although not completely pristine, these mineral phases formed possibly in environments similar to those found where the astronomical spectra come from. So far, for comparison purposes mainly terrestrial analogs like synthetic minerals e.g.[1] or whole dust particles like IDP [2] have been used. Techniques: Owing to the fine grained nature of the minerals and components, which made a separation of single, homogeneous mineral grains mostly impos-sible, a whole range of different FT-IR techniques was applied. For in-situ measurements we used a Perkin Elmer SpectrumOne FT-IR microscope in the specular reflectance mode, which allows to obtain spectra from areas down to 10 10 m. From these reflectance spec-tra, the absorption part was obtained using the Kram-ers-Kroning algorithm. When it is possible to separate material from a CAI, we plan to analyse powdered samples in the transmission/absorption mode of the microscope. The wavelength range covered by these techniques is 2.5 to 16 m.     The CAI analyzed was on a polished block of a Ornans CO3.3 sample. Phases were preliminary char-acterized based on their stochiometry using SEM-EDX. Results: The compact CAI (Fig.1a) mainly con-sists of  spinel and  melilite, surrounded by Al-diopside. Fig.1b shows the reflectance (R) and calcu-lated absorbance spectra (k) of areas in the CAI. Discussion: Fig.1c compares the results with infra-red spectra  of  the circumstellar discs from the T-Tauri star TW Hya [3] and   Pictoris [4] (Fig.1c). While there is no perfect fit, the band positions in the absorbance spectra e.g. of the melilite/spinel mixture and the Al-diopside exhibits some similarity with the TW Hya spectra for two bands.  References: [1] Hofmeister A. M. et al. (2003) Mon. Not. R. Astron. Soc. 345, 16-38. [2] Molster F. J. et al. (2003) Lunar Plan. Sci. XXXIV, A1148. [3] Sitko M. L. et al. (2000) Astron. Journ., 120, 2609-2614 [4] Knacke et al. (1993) Astrophys. J., 418, 440-450.    Fig.1a-c. (a) BSE image, (b) reflectance (R) and absorbance (k) IR in-situ spectra, (c) astronomical data. Workshop on Chondrites and Protoplanetary Disk (2004) 9023.pdf

Mid-infrared spectroscopy of CAI and their mineral components

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Mid-infrared spectroscopy of CAI and their mineral components

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