산청지역에 분포하는 챠노카이트의 암석학적 연구 = Petrology of Charnockite in Sancheong Area

다국어 초록 (Multilingual Abstract)

The Charnockite in Sancheong region is quarzofeldspathic rock containing orthopyroxene and garnet with a
color dark than common granitic rocks. The Charnockite are mostly massive and medium to coarse-grained with Kfeldspar
phenocryst, but reveal weak foliation. The rock consist mainly of quartz, K-feldspar, plagioclase and
orthopyroxene, with biotite, garnet, and anthophyllite. In petrochemistry, the Charnockite has 61-65% SiO2 contents,
varying gradually into the margin contacted with orthogneiss, which have compositions of felsic igneous rocks. Major
element show almost systematical variation with those of the marginal orthogneisses, except the hornblende gneiss and
anorthosite. The Charnockite and orthogneisses show the tholeiitic differentiational trend. Trace and rare earth element
abundance patterns in the Charnockite show remarkable negative Sr and Eu anomalies similar to orthogneisses, but
different from the hornblende gneiss and anorthosite. Eu contents of the Charnockite are richer than that of orthogneisses.
The metamorphic condition of the Charnockite were tested by an orthopyroxene-garnet geothermometer and a plagioclasegarnet
geobarometer. Estimated P-T conditions are about 761oC and 7 kbar at peak metamorphism, but 653oC and 6.4
kbar at retrograde metamorphism. This suggests that the Charnockite have from an early stage of high-grade
metamorphism to represent the granulite facies and then to a late stage medium-grade metamorphism belonging to the
amphibolite facies.