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|Title: ||A preliminary report on the geochemistry of amphibolites from the Chuncheon area in the Gyeonggi massif, Korea|
|Authors: ||SUZUKI, Kazuhiro|
DUNKLEY, Daniel J.
|Issue Date: ||2009|
|Publisher: ||Dept. of Earth and Planetary Sciences, Nagoya University|
|Citation: ||The Journal of Earth and Planetary Sciences, Nagoya University. v.56, 2009, p.13-29|
|Abstract: ||Amphibolites in the Gubongsan Group at Chuncheon, South Korea have garnetbearing and garnet-free assemblages: garnet+tschermakitic hornblende+quartz+plagioclase+ biotite (garnet amphibolite), relict garnet+edenitic hornblende+plagioclase+ quartz+biotite (relict garnet-bearing amphibolite), edenitic hornblende+plagioclase+ quartz+biotite and tschermakitic to edenitic hornblende+plagioclase+chlorite+quartz +biotite. The garnet relics are extensively embayed and surrounded by coronas of plagioclase+edenitic hornblende. Whole-rock compositions of amphibolite samples are equivalent to basaltic protoliths with MORE-like characteristics. Garnet-free, chlorite-bearing amphibolite is the most magnesian, with an Fe2+/(Fe2++Mg) value of 0.26. Graphical representations of whole-rock and mineral compositions show that individual mineral assemblages approach chemical equilibrium and define distinct compositional volumes in the A (Al203+Fe203-Na20-K20) - C (CaO) - F (FeO) - M (MgO) tetrahedron. The A component is critical in determining the stability of the garnet-bearing assemblage, which occurs above a threshold that decreases at higher Fe/(Fe+Mg) values. As a result, small variations in bulk composition can produce differing mineral assemblages. Whole-rock Sr concentrations are significantly depleted in garnet amphibolite, whereas values in relict garnet-bearing and garnet-free amphibolite match typical basaltic compositions. The depletion may be attributable to leaching via fluids released by dehydration reactions and the prograde breakdown of Sr hosts, such as plagioclase and epidote.|
|Appears in Collections:||The Journal of earth and planetary sciences|
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