• Journal of the Korean earth science society
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• v.32 no.7
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• pp.860-870
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• 2011

This study is to explore the Pedagogical Content Knowledge of beginning earth science teachers about the porphyritic texture of igneous rocks, and to suggest the teaching device that can prevent a trial and error of students in earth science instruction. We developed an interview guideline concerned with basic perception on the porphyritic texture, formation condition and formation process of porphyritic rocks, teaching and learning on porphyritic rocks for it. And data was collected from 5 beginning earth science teachers (3 high schools, 2 middle schools) through a group discussion method. In result, despite the porphyritic texture can be found at hypabyssal rocks as well as volcano rocks and plutonic rocks, most beginning earth science teachers cognized that it could be found at hypabyssal rocks only by focusing the formation depth of hypabyssal rocks. Also, the formation of porphyritic texture should be considered the factors such as cooling rate, nucleation density, growth rate, growth time, etc. However they mainly reflected the formation temperature and growth rate as it's parameter. Participants have wrongly perceived that a phenocryst necessarily differs from a groundmass on chemical composition. And they are inclined to discriminate phenocryst from groundmass through their chemical differences, instead of grain size.

• Economic and Environmental Geology
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• v.11 no.1
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• pp.1-9
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• 1978

The study is on petrology and petrochemistry of Pajoo Acidic Igneous pluton which intruded into Precambrian metasediments of basement of the area. The geologic sequence of studied area was shown in table 1 and 10 modal analyses and 7 chemical analyses on the rock samples taken from the body. Pajoo Acidic Igneous rock consist of hypersthene-quartz-diorite and porphyritic adamellite which based on the classification of the subcommision on systematics of igneous rocks of IUGS. And porphyritic adamellite which occured as a small stock was intruded into hypersthene quartz diorite. The rock forming minerals of hypersthene quartz diorite are composed of plagioclase, perthite, quartz, hypersthene, hornblende, biotite and porphyritic adamellite is composed of perthite, quartz, plagioclase and biotite. And the former is hypidiomorphic granular texture and later is porphyritic texture with microcline phenocrysts. In silica-oxides variation diagram, the Pajoo acidic igneous rocks are similar to the trend of Daly's average composition and equivalent to the calc-alkalic rock series. In AMF diagram, these rocks are stock of fissure filling vein type by cooling in magmatic differentiation.

• Economic and Environmental Geology
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• v.7 no.3
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• pp.123-152
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• 1974

The study focused to the so called "Yangpyeong Igneous Complex" which intruded into the Gyeong Gi gneiss complex of Pre-cambrian basement of Yangpyeong area. The geologic sequence of the mapped area was shown in table 1. In laboratory work, 31 modal analyses and 7 chemical analyses on the rock samples taken from the igneous complex have been made to discuss the nomenclature of the rocks and the petrological relationship between rock types. The petrographical and petrochemical features based on the analyses are as follow; 1) The classification of this rocks based on the systematics of igneous rocks of IUGS showed that Yangpyeong Igneous complex consist of hornblende gabbro, diorite and porphyritic monzonite. The major rock forming minerals in hornblende gabbro are hornblende and plagiodase ($An_{46{\sim}55}$), in diorite, hornblende, biotite and plagioclase ($An_{23{\sim}33}$) and in porphyritic monzonite, K-feldspar, plagioclase ($An_{21{\sim}35}$), hornblende and biotite. Hornblende gabbro and diorite show coarse to medium grained hypidiomorphic granular texture and porphyritic monzonite was named by the characteristically porphyritic texture of K-feldspar phenocrysts. 2) Silica-oxides variation diagram (Fig.4) illustrate that the igneous complex is similar ttl that of Daly's average basalt-andesite-dacite-rhyolite and equivalent to the calc-alkalic rock series of Peacock's rock series. In AMF diagram (Fig. 5), the trend of the igneous complex is nearly pararell to that of the Skaergaard intrusion which shows the trend of the fractional crystalization of magma. 3) In normative Or-Ab-An diagram (Fig. 6) the general trend of the data points from gabbro to porphyritic monzonite of the igneous complex directs to a point of Or/Ab=1:1 on the side of Or-Ab. The field and laboratory evidences suggested that the Yangpyeong igneous complex was thought to be a series of comagmatic differential products.

• Journal of the Korean earth science society
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• v.29 no.3
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• pp.305-314
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• 2008

The purpose of this study is to analyze the concept of igneous rock textures and to uncover incorrect descriptions regarding the concept found within high school Earth Science II course seventh curriculum textbooks. Based upon this analysis suggestions will be made so as to improve descriptions regarding the concept of igneous rock texture. At least some incorrect descriptions regarding igneous rock texture were found in all the textbooks examined. Textures of volcanic rocks are described as being either fine-grained and glassy or porphyritic, while those of plutonic rocks are described as hollocrystalline, granular, coarse-grained or equigranular. These descriptions may contribute to forming and/or reinforcing misconceptions about both the classification criteria for, as well as the general concept of igneous rock textures. Therefore, some improvement schemes for the classification of igneous rock textures have been suggested. These schemes suggest that volcanic rocks be classified as either aphanitic or porphyritic, while plutonic rocks be classified as phaneritic, hollocrystalline or equigranular according to granularity, crystallinity, and both the absolute and relative sizes of the crystals within the rock.

• Economic and Environmental Geology
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• v.15 no.4
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• pp.189-204
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• 1982

The Geodo mine is located in the southern limb of the Hambaeg syncline. Geology of the area consists of Paleozoic-Mesozoic sedimentary Rocks and Cretaceous igneous rocks. The important igneous rocks presumably related to skarnization and ore mineralization in the area, are the early granodiorite and the late porphyritic granodiorite. Two mineralogical types of ore deposits are recognized in the area. They are the Fe-Cu deposits in the Myobong formation and the Au-Bi-Cu deposits in the Hwajeol formation. Contact metamorphism due to granodiorite intrusion includes hornfelsization, exoskarnization and endoskarnization. Wall-rock alterations related to the Fe mineralization are grouped into the hydrothermal replacement skarnization and the hydrothermal filling skarnization. Another hydrothermal alteration is associated with the Cu mineralization. Various mineralogical analyses have been applied for the identification of minerals. They include optical microscopy, chemical analysis, etching test, X-ray diffraction, and infrared absorption spectroscopic analyses. The ore minerals in these ore deposits are classified into two groups;hypogene and supergene minerals. Hypogene minerals consist of magnetite, pyrite, chalcopyrite, and chalcocite. Supergene minerals consist of chalcocite, bornite, and geothite. Ore minerals show various kinds of ore texture: open-space filling, exsolution, replacement, and cementation texture. The gangue minerals consist of quartz, diopside, epidote, garnet and plagioclase in the hornfelsic zone, garnet, diopside, scapolite, actinolite, sericite, chlorite, quartz, and calcite in the skarn zone, and, epidote, chlorite, sericite, quartz, and calcite in the late hydrothermal alteration zone. This study shows that the Fe-Cu deposits are of metasomatic pipe type with the later hydrothermal fillings, and the Au-Bi-Cu deposits are of hydrothermal fissure-filling type. The mineralization is probably related to the intrusion of porphyritic granite.

• The Journal of the Petrological Society of Korea
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• v.14 no.1
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• pp.12-23
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• 2005

Cretaceous granitic rocks in the Waryongsan area occur as a stock and show compositional changes with altitude. They include mafic microgranular enclaves (MME) with various sizes and types. The MMEs present clear evidence of magma mingling such as supercooling zone, mantling texture and back veining. The granitic rocks are divided into porphyritic granite, porphyritic granodiorite and fined-grained granite by their petrographic characteristics and modal compositions. The MMEs are discriminated to quartzdioritie, quartzmonzodiorite and tonalite. They have varying areal proportions in each granitic rock-type: 10∼l5% in the porphyritic granite, about 50% in the porphyritic granodiorite, and about 20% in the fined-grained granite. SiO₂ contents shows compositional change of 61.2∼72.0wt.%. Mean SiO₂ contents have 61.7wt.% in the porphyritic granodiorite, 68.6wt.% in the porphyritic granite. and 71.9wt.% in the fined-grained granite, respectively. Major oxide contents of the granitic rocks linearly vary with SiO₂ contents from the porphyiritic granodiorite to the fine-grained granite on Harker diagrams. Linear compositional variations seem to have been caused by differential degrees of mingling between mafic magma and host granite. Where larger amount of mafic magma was injected into the host granitic magma, the two magmas reached to thermal equilibrium more quickly and eventually chemical mixing occurred to produce the composition of the porphyritic granodiorite. On the other hand. less amount of injected mafic magma would have been responsible for mechanical mixing to produce the compositions of the porphyritic granite and the fined-grained granite. Therefore, it is considered that the granitic rocks in the Waryongsan area experienced magmas mingling resulting from the injection of more mafic magma into differentiating granitic magma, and that the compositional changes of the granitic rocks were ascribed to the degree of mingling between the two magmas.

• Korean Journal of Heritage: History & Science
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• v.46 no.2
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• pp.136-149
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• 2013

We studied the characteristics and the growth mechanism of surface cracks from the Naksansa seven-storied stone pagoda(Treasure No. 499). The pagoda is composed of both medium-grained, porphyritic biotite granite and hornblende-biotite granite. Alkali feldspar megacrysts are easily found as phenocrysts in the rocks. Surface cracks intensely developed at the lower part of the stone pagoda, and their directions are of vertical, horizontal, and diagonal. The rocks of the pagoda have intrinsic microcracks which can be defined as rift and grain rock cleavages. Both rock cleavages seems likely to have led to the crack growth and consequently to the mechanical deterioration of the pagoda. The vertical cracks developed parallel to the vertical compressive stress, whereas horizontal ones formed by tensile strength normal to the vertical compression. In addition mineral cleavages and twin planes of alkali feldspar phenocrysts seems to have been closely related to the mechanical breakdown of the rocks in the NE part of the pagoda.

• Economic and Environmental Geology
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• v.26 no.1
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• pp.83-96
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• 1993

Kwangju granite body located in vicinity of Kwangju city consist of three rock bodies-Kwangju rock body, Jangsung rock body and Youngkwang rock body. Petrochemistry of Kwangju granite is as follows: Kwangju granite body is igneous complex which compose of a series of differential products of a magma. Kwangju granites are divided into four rock facies based on the geologic age, mineralogical and chemical constituents and texture: Triassic hornblende-biotite granodiorite and biotite granite, and Jurassic porphyritic granite and two mica granite. Harker and other variation diagrams of Kwangju granites plot on trend of calc-alkali rock series and range of peraluminous granite. Parental magma type of Kwangju granites correspond to I-type, Syn-Collision type in compressive stress field by collision movement between both rock block. In chondrite normalized REE patterns of Kwangju grnites, LREE enriched than HREE in REE amount and have more steep negative slope with slightly (-) Eu anormaly.

• Economic and Environmental Geology
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• v.20 no.2
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• pp.125-136
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• 1987

The characteristic features of mylonitic granite in the Unbong-Ayoung area is as follow; (1) Mylonitic granite is a shearing product from porphyritic granite of Namweon Granites. (2) This rock megascopically shows foliated texture, and their modal compositions according to classification of dynamically metamorphosed rock are correspond to blastomylonite. (3) This rock generated by dextral strike slip movement at deep level. (4) The geochronological data of hornblendes from this rock undertaken by $^{40}Ar/^{89}Ar$ method are 191Ma to 195Ma. (5) The geochronological data of this rock suggests that Namweon Granites might be a product of intrusion and crystallization at the late Triassic or the Jurassic.

• The Journal of the Petrological Society of Korea
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• v.28 no.4
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• pp.279-298
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• 2019

Mupung granite, which is located adjacent to Gimcheon granites to the north and Geochang granites to the south, has been known to consist of biotite-hornblende granite (Gbh), porphyritic granite (Gp), and hornblende-biotite granite (Ghb). In this study, we subdivided the Gbh of Mupung granite into biotite granite (Gb) and biotite hornblende granite (Gbh), based on petrological observations. The grayish Gb with medium to coarse grain and porphyritic texture contains a small amount of muscovite, but the hornblende and mafic microgranular enclave (MME) is not observed in Gb. On the other hand, MME can be commonly found in pinkish Gbh. The mafic minerals in Gbh are mostly hornblende and biotite. In the Gb in Mupung granites, the hornblende and sphene (which is the characteristic minerals in Gimcheon granite) are not observed. In addition, the trend of the changes in major elements of Gb in Mupung granites is similar to that of Geochang granites. These petrological characteristics suggest that the Gb in Mupung granite has a similarity with Geochang granite (than Gimchen granite). We also observed that the texture and composition of minerals of Gbh, as well as those of surrounding Gp and Ghb, are consistent with the characteristics of Cretaceous granites in Gyeongsang basin, rather than those of Jurassic granites in Yeongnam massif.