Title Carbonic fluids in ultrahigh- temperature metamorphism; evidence from Raman spectroscopic study of fluid inclusions in granulites from the Napier Complex, East Antarctica
Author Tsunogae, T.; Santosh, M.; Dubessy, J.; Osanai, Y.; Owada, M.; Hokada, T.; Toyoshima, T.
Author Affil Tsunogae, T., University of Tsukuba, Graduate School of Life and Environmental Sciences (Earth Evolution Sciences), Tsukuba, Japan. Other: National Institute of Polar Research, Japan; Kyushu University, Japan; Chiba University, Japan; Kochi University, Japan; Université Henri Poincaré-Nancy 1, France; Kyushu University, Japan; Yamaguchi University, Japan; National Institute of Polar Research, Japan; Niigata University, Japan
Source Geodynamic evolution of East Antarctica; a key to the east-west Gondwana connection, edited by M. Satish-Kumar, Y. Motoyoshi, Y. Osanai, Y. Hiroi and K. Shiraishi. Geological Society Special Publications, Vol.308, p.317-332, . Publisher: Geological Society of London, London, United Kingdom. ISSN: 0305-8719. ISBN: 978-1-86239-268-7
Publication Date 2008
Notes In English. 64 refs. Ant. Acc. No: 85826
Index Terms Antarctica--East Antarctica; Antarctica--Enderby Land; Amundsen Bay; Antarctica; aqueous solutions; Archean; Bunt Island; carbon dioxide; chemical composition; East Antarctica; Enderby Land; fluid inclusions; geologic thermometry; granulites; inclusions; International Polar Year 2007-08; IPY 2007-08 Research Publications; metamorphic rocks; metamorphism; mineral assemblages; Napier Complex; petrography; Precambrian; Priestley Peak; Raman spectra; spectra; temperature; Tonagh Island; ultrahigh temperature
Abstract We report the first quantitative compositional data on fluid inclusions in ultrahigh-temperature (UHT) granulites from the Napier Complex of Enderby Land, East Antarctica. Fluid inclusions in various high- grade minerals such as garnet, orthopyroxene and sapphirine from three UHT localities in the Amundsen Bay area were studied in terms of petrography and microthermometry as well as laser Raman spectroscopy. Measured melting temperatures of inclusions from all the three localities indicate that the trapped fluid phase is dominantly carbonic. Raman analyses confirmed a near pure CO2 composition with only minor dilutants such as N2 (‹6.0 mol%), CH4 (‹0.3 mol%), and H2O (‹0.1 mol%). CH4- bearing fluid associated with sapphirine granulites suggests low oxygen fugacity ( fO2) conditions for the rocks, whereas CH4 was not detected from fluid inclusions in magnetite-bearing high-f O2 garnet granulite. The range of CO2 isochores computed from density measurements in fluid inclusions from the granulites pass through the peak P-T conditions of the Napier metamorphism (T= 1050-1150 °C, P=9-11 kbar) indicating synmetamorphic nature of the fluids. Inclusions in garnet from Bunt Island coexist with carbonate minerals (magnesite) and graphite along with dense CO2-rich fluid, indicating probable derivation from deep- seated primary magmatic sources. The ubiquitous association of carbonic fluids in the UHT mineral assemblages suggests CO2 influx during extreme crustal metamorphism of the Napier Complex. The carbonic fluid probably played an important role in transporting heat from mantle or mantle- derived magmas and in stabilizing the dry mineral assemblages.
URL http://hdl.handle.net/10.1144/SP308.15
Publication Type journal article
Record ID 290781