• Economic and Environmental Geology
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• v.19 no.2
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• pp.123-131
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• 1986

This study is focused on petrochemistry and petrogenesis of alkali granite which exposed at northern area of the Uljin mine in NE Korea. The rock is corresponded to the range of alkali feldspar granite and alkali feldspar quartz syenite on IUGS classification and contains characteristic Fe-rich biotite (annite) and sodic alkali amphibole (arfvedsonite). The alkali granite is the hypersolvus one-feldspar granite which is characterized by the absence of plagiclase except as a component of perthite and its normatve An contents are less than 5wt%. The bulk compositions of the alkali granite show reverse trends compared to Daly's. Tuttle and Bowen (1958) experimentally support that properties of the hypersolvus granite indicate that they have crystallized at high temperatures from a magma.

• The Journal of the Petrological Society of Korea
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• v.5 no.2
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• pp.142-160
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• 1996

Petrological and geochemical characteristics of A-type granite were studied from the Namsan and Tohamsan granites in the vicinity of Kyeongju city, southeastern Korea. The Namsan granite consists of hypersolvus alkali-feldspar granite in the northern part and subsolvus alkali-feldspar to biotite granite in the southern part. This hypersolvus granite usually has miarolitic cavities and is characteristically composed of quartz, single homogeneous one-feldspar (alkali feldspar) forming tabular microperthite crystals, or micrographic intergrowth with quartz, and interstitial biotite (Fe-rich annite), alkali amphibole (riebeckitic arfvedsonite) and fluorite. Petrographic and petrochemical characteristics indicate that the hypersolvus granite and subsolvus granite from the Namsan belogn to the A-type and I-type granitoid, respectively. The A-type granite is petrochemically distinguished from the I-type Bulgugsa granites of Late Cretaceous in South Korea, by higher abundance of $SiO_2$, $Na_2O$, $Na_2O+K_2O$, large highly charged cations such as Rb, Nb, Y, Zr, Ga, Th, Ce. U the REEs and Ga/Al ratio, and lower abundance of $TiO_2$, $Al_2O_3$, CaO, $P_2O_5$, MnO, MgO, Ba, Sr, Eu. The total abundance of REEs is 293 ppm to 466 ppm, showing extensively fractionated granitic compositon, and REEs/chondrite normalized pattern shows flat form with strong Eu '-' anomaly ($Eu/Eu^{\ast}$=0.03-0.05). A-type granite from the Namsan area is thought to have been generated late in the magmatic/orogenic cycle after the production of I-type granite and by direct, high-temperature partial melting of melt-depleted, relatively dry tonalitic/granulitic lower crustal material with underplating by mantle-derived basaltic magmas associated with subduction.

• Economic and Environmental Geology
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• v.31 no.5
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• pp.399-413
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• 1998

Daegang granite is located around the Namwon-gun, Cheolabuk-do, and is an elongate stock $(80 km^{2})$ in the NNE-SSW direction. Daegang granite has the very same mineralogical and geochemical characteristics as those of the typical A-type granites; (1) it is a one feldspar hypersolvus granite, and is classified as an alkali feldspar granite in the lUGS scheme, (2) has small amounts of Fe-rich biotite (annite) and alkali amphibole (ribeckite) that are late in the crystallization sequence of the granitic magma, (3) always contains opaque oxides, fluorite and zircon, (4) shows high and quite homogeneous $SiO_2$, content (mostly 72~77 wt.%) and $(Na_{2}O+K_{2}O)/Al_{2}O_{3}$ ratio (0.90~0.98), (5) contains high Ga, lOOOO*Ga/Ai, $K_{2}O+Na_{2}O$, $(K_{2}O+Na_{2}O)/CaO$, $K_{2}O/MgO$, FeO/MgO, agpaitic index, Zr, Nb, Ce, Y, Zn value or ratio that resemble to those of the Australian A-type granites (Whalen et al., 1987), and (6) has enriched LREE and HREE that show flat variation pattern with slightly depleted in HREE and profound Eu anomalies (Eu/Eu*=0.04~0.l4). In the tectonic discrimination diagrams of Pearce et al. (1984) and Eby (1992), Daegang granite is classified as a within plate granite and $A_{2}-type$.