Matrices of carbonaceous chondrites: Characterization by synchrotron IR microspectroscopy

Abstract

Here we demonstrate the diagnostic potential of reflectance IR microspectroscopy for non-destructive characterization of matrices of carbona-ceous chondrites (CCs) in situ using conventional polished sections. Polished sections of Orgueil (CI1), Kainsaz (CO3), Efremovka (CV3), Mighei (CM2), Cold Bokkeveld (CM2), Murray (CM2), Isheyevo (CH-CBb), metamorphosed carbonaceous chondrites (MCCs) Dhofar 225, Dhofar 735, and NWA 4757 were used in this study. The IR spectra between 1.5 and 14 µm were acquired at the IRIS infrared beamline at the electron storage ring facility BESSY. We show that IR reflectance microspectro-scopy is a useful tool for characterization of CC matrix constituents in terms of their hydration states. It allows one to distinguish between various types of CC matrix materials, including hydrated, anhydrous and thermally metamorphosed. In particular, in Ish-eyevo (CH-CBb) we detected three different types of hydrated matrix lumps, none of which could be identified with a known CC group.