Processes of Granulite Formation and Their Geochemical Signatures: A Study in the Wind River and Laramie Mountains,Wyoming

点击翻译按钮获取中文摘要

The problem of the origin of granulites is of interest to a wide cross-section of Earth Scientists because present-day surface outcrops are believed to give clues to processes operating, past and present, in the lower crust. It is proposed to study the causes of granulite metamorphism and to identify the geochemical effects of hornblende breakdown. The breakdown will be studied in two places in the contact aureole of the Laramie Anorthosite. In one locality hornblende breakdown due to simple dehydration, while in other breakdown is in response to CO2-fluxing from adjacent marble. Both of these mechanisms of hornblende decomposition have been proposed as causes of granulite metamorphism. The results of the Laramie Anorthosite investigation will be applied to interpreting the origins of charnockites in the Wind River Mtns. An attempt will be made to determine the origin of granulite selvages in the country rock of charnockite dikes. Criteria will be established for distinguishing igneous charnockites from granulite gneisses metamorphosed in the granulite facies. The research will use field mapping, petrology, electron microprobe analyses, stable and radiogenic isotope analyses to deduce the processes of granulite formation and their geochemical signatures.