Progress in Resource Evaluation Using a Handheld Raman Instrument Developed for Astronaut Missions

ABSTRACT Raman spectroscopy is being developed for resource evaluation on planetary surfaces, especially on the Moon. Analogue studies were undertaken to collect data that would indicate the presence of water and help develop the technology to search for valuable trace elements. Analysis of a gabbro‐anorthosite suite by Raman spectroscopy distinguished pyroxene, olivine and feldspar in samples whose mineralogy had been cross‐checked by electron microscopy. Examination of the olivine by electron microscopy showed a complex distribution of hydrated alteration products referable as serpentine or iddingsite. The altered olivine is thus a proxy for water. Raman spectroscopy of similar olivine produced a map of alteration products, which is a first depiction of a map of hydration. A targeted set of trace elements was more abundant in the feldspar. Raman spectroscopy of feldspar in cross‐cutting pegmatite veins detected a range of minerals containing trace elements, including anomalous amounts of the critical elements lithium and caesium. Measurement of Li and Cs in hot spring deposits which lie on the gabbro‐anorthosite suite shows much higher enrichment in shale sediments, which Raman spectroscopy identified as muscovite. This conclusion is consistent with the concentration of some trace elements (including Li) in detrital minerals and other trace elements (including Cs) in fluid precipitates.