Subject: Beryllium in Sapphirine/Khmaralite: implications for sapphirine compatibility relationships and geochemistry
Time: 16:00pm September 10, 2009
Place: New Geology Building 3325 Room
Reporter: Dr. Andrew G. CHRISTY
Research School of Earth Sciences, Australian National University
Brief introduction of the reporter:
Andrew G. CHRISTY received his BA in Geological Sciences in 1984 and his PhD in 1988, both from Cambridge University, England. His PhD study was on the effects of pressure, temperature, and composition in controlling the occurrence of different crystal structural varieties of the mineral sapphirine. This work led him from mineral chemistry and crystallography into the area of ultrahigh temperature metamorphism. Since then, he was held postdoctoral positions in Earth Sciences at Cambridge (1988-1990), in Chemistry at Leicester University, England, studying crystal structures at high pressure using diamond anvil cells (1990-1993), and at the Daresbury Synchrotron, England (1993-1994). In 1994, he moved to the Australian National University, Canberra, Australia, where he held Research Fellowships in the Research School of Chemistry (1994-1999) and Research School of Physics and Engineering (2000-2001) before becoming manager of the analytical laboratories at the former Geology Deparment, which in 2008 merged with the Research School of Earth Sciences. He now lectures in mineralogy, and contributes to other undergraduate courses such as petrology and analytical chemistry.
Dr. Christy has published about 80 papers, on subjects that include theory of crystal structure phase transitions, diamond anvil cell design, magnetic carbon nanofoams, and silicate-carbonate composite 'biomorphs' that resemble Archean microfossils. A recurring theme is the relationship between chemical composition (especially unusual minor solid solution components), short-range and long-range order of atoms, and the stability of structures. The mineral sapphirine shows many types of unusual behaviour in this regard, which is why he has returned to it often since his PhD, and has published a total of 12 sapphirine-related papers, most recently in early 2009. This talk shows why sapphirine is so fascinating, the way that it concentrates the rare light element beryllium, which has an extreme effect upon its phase stability relationships, and the resulting change in behaviour of beryllium from a classic 'incompatible element' to a highly compatible one.