Analysis of partial melting reactions of pelitic and basic metamorphic rocks of the Hidaka metamorphic belt.

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Following results have been obtained by the three-year research (1995,1996 and 1997) supported by this grant.1.The Hidaka metamorphic rocks were formed by progressive metamorphism under the conditions of the greenschist facies to the granulite facies. The pressure and temperature conditions are estimated to have been 450ﾟC,0.2 MPa to 900ﾟC,0.5 MPa by means of several kinds of geothermometor and geobarometor. The age of the metamorphism are estimated to have been 56-40 Ma (Eocene) on the basis of data of K-Ar dating.2.Leucosome of pelitic and basic metamorphic rocks of the Hidaka metamorphic belt is solidified parts of melt formed by partial melting of these rocks. On the other hand, melanosome is residue of partial melting.3.Partial melting reactions of pelitic rocks of the granulite facies (zoneD and zone E) are as follow :1.3 biotite + 4.6 K-feldspar + 78.3 plagioclase + H_2O = 100 melt + 3.2 sillimanite + 191 quartz (in zone D),13.4 biotite + 8.6 plagioclase + 15.6 quartz + 16.9 sillimanite = 100 melt + 13.7 K-feldspar + 10.8 cordierite (in zone E).4.Partial melting reactions of basic rocks (amphibolite migmatites) of the granulite facies (zone E) calculated by the isocon method are as follow :0.77 hornblende + 10.00 plagioclase + 0.01 limenite = 0.04 magnetite + 10.98 + melt (in the lower temperature part of zone E),1.85 hornblende + 10.00 plagioclase + 0.0.ilmenite + 12.54 quartz = 0.01 magnetite + 23.96 melt + clinopyroxene (in the higher temperature part of zone E).5.Protolith of basic metamorphic rocks is basalt of N-MORB compositions.