Title Fe2+-Mg partitioning experiments between orthopyroxene and spinel using ultrahigh-temperature granulite from the Napier Complex, East Antarctica
Author Sato, K.; Miyamoto, T.; Kawasaki, T.
Author Affil Sato, K., Tokyo Institute of Technology, Department of Earth and Planetary Sciences, Tokyo, Japan. Other: National Institute of Polar Research, Japan; Kyushu University, Japan; Chiba University, Japan; Kyushu University, Japan; Ehime 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.431-447, . Publisher: Geological Society of London, London, United Kingdom. ISSN: 0305-8719. ISBN: 978-1-86239-268-7
Publication Date 2008
Notes In English. 56 refs. Ant. Acc. No: 85833
Index Terms Antarctica--East Antarctica; Antarctica--Enderby Land; alkaline earth metals; Antarctica; Archean; chain silicates; chemical composition; chemical fractionation; East Antarctica; Enderby Land; experimental studies; ferrous iron; geochemistry; geologic thermometry; granulites; high-grade metamorphism; International Polar Year 2007- 08; IPY 2007-08 Research Publications; iron; laboratory studies; magnesium; metals; metamorphic rocks; metamorphism; Napier Complex; orthopyroxene; oxides; partitioning; Precambrian; pyroxene group; silicates; spinel; temperature; ultrahigh temperature
Abstract Temperature dependence of the Fe2+-Mg exchange between orthopyroxene (Opx) and spinel (Spl), 1/2Fe2Si2O6(OPX) + MgAl2O4(Spl) = 1/2Mg2Si2O6(Opx) + FeAl2O4(Spl) was experimentally determined at 9-13 kbar and 900-1200C using an ultrahigh-temperature (UHT) granulite collected from the Napier Complex in Enderby Land, East Antarctica. The Fe2+-Mg distribution coefficient, KD=XSplFeXOpxMg/XSplMgXOplFe is emirically obtained as ln KD=-1.134+[2341+7.5(P-11)]/T where X is the cationic mole fraction, and pressure P and temperature T are in kbar and Kelvin, respectively. The new geothermometer was applied to various natural UHT and associated high-grade metamorphic rocks from East Antarctica and other regions of the world. The results indicate temperatures between 735 and 902C at pressures in the range of 5-14 kbar. This geothermometer utilizing spinel does not give peak metamorphic condition, because it is relatively easy for spinel to re-equilibrate during the cooling stage of metamorphism. Hence, we conclude that the geothermometer is suitable for evaluating the closure temperature for the KD between aluminous orthopyroxene and spinel during retrograde metamorphism rather than the thermal peak.
URL http://hdl.handle.net/10.1144/SP308.22
Publication Type journal article
Record ID 290774