Preliminary Results of Cathodoluminescence Spectral Analysis of beta-Ca-Phosphates (``Whitlockite'') in the Mars Meteorite ALH 84001

Three mineral grains of -Ca-phosphates were found during a cathodoluminescence (CL) imaging study of grain mounts of the mars meteorite ALH84001 sample N fragments #3734, #3738 and #3739. The images of one of the fragments and the resulting CL spectra are shown in Plate 1. CL spectra were collected with microcomputer-based solid state multichannel analyser, integrated with a linear CCD-array silicon detector responsive from 200-1100 nm, has been interfaced within the optical chain of a MBX Cameca microprobe. The grains were also analysed with an SX50 microprobe at 20kV, 10nA and 10 second peak counting time. The small size and questionable stability of the mineral does not allow for greater counting times and higher beam currents. The sample had already been damaged by the use of high beam currents and exposure times. These Ca-phosphates were often called whitlockite, however they are better described as -Ca-phosphates as discussed by E. Dowty (2). The calculated formula closely matches that purposed by Dowty. The CL spectra results are very preliminary and the peaks have been labelled as indicated by the probe analysis and CL spectral analysis of standards at the GSC. The more important aspect is that CL spectroscopy is a potentially powerful tool in the study of -Ca-phosphates.