왜암석을분류해야하나? (Fig. 시대별암석분류개수 ) Lecture 2 Igneous Rocks: Classifications 화성암의종류에따라서생성환경이다르다. 너무많은사람들이다양한이름을이용. 분류학의필요성강조 ( 분류된암석종류판별 = 생성환경판단 ) Textural-mineralogical classifications 현정질? 비현정질? Mineralogy Essential mineral( 주구성광물 ) : 필수요소 ( 광물부피비율 ) Chracterizing accessory mineral or varietal mineral( 특정부수광물 ) : 세분에사용 Minor accessory mineral( 부부수광물 ) : % 미만광물로명명에는무관 Textural-mineralogical classifications 반상조직 : 반정 (phenocryst) + 석기 (groundmass) 세립 (fine grained) < 1mm (<sugar granules) 중립 (medium grained) 1- mm (sugar to pea size) 조립 (coarse grained) - 0 mm Example (gabbro) : phaneritic rock, Ca-Plagioclase, olivine, pyroxene, other accessories. Example (gabbro) : 현정질, Ca- 사장석 ( 회장석 )+ 감람석 (olivine) + 휘석 (pyroxene), other accessories. Textural-mineralogical classifications 반상조직 : 반정 (phenocryst) + 석기 (groundmass) 세립 (fine grained) < 1mm (<sugar granules) 중립 (medium grained) 1- mm (sugar to pea size) 조립 (coarse grained) -0 mm Textural-mineralogical classifications 반상조직 : 반정 (phenocryst) + 석기 (groundmass) 세립 (fine grained) < 1mm (<sugar granules) 중립 (medium grained) 1- mm (sugar to pea size) 조립 (coarse grained) -0 mm Example (gabbro) : 현정질, Ca- 사장석 ( 회장석 )+ 감람석 (olivine) + 휘석 (pyroxene), other accessories. Example ( 흑요암 ;obsidian) : 유리질 or 유리반정상 ( 반상 ) 1
( 장석 %, 유색광물 %, 색지수 ) ( 장석 %, 유색광물 %, 색지수 ) ( 장석 %, 유색광물 %, 색지수 ) ( 장석 %, 유색광물 %, 색지수 ) 감람암 (peridotite) 섬록암 (diorite) 섬록암 (diorite) 안산암 (andesite) 안산암 (andesite) Table 4.1. Some Classification of Color Index IUGS Shand Raymond 0- Holo- ( 완우백질 ) -3 Leucocratic ( 우백질 ) 0-30 0- hyper Table 4.1. Some Classification of Color Index IUGS Shand Raymond 0- Holo- ( 완우백질 ) -3 Leucocratic ( 우백질 ) 0-30 0- hyper 3-6 Mesocratic ( 아우흑질 ) 30- mesotype 11-0 3-6 Mesocratic ( 아우흑질 ) 30- mesotype 11-0 6- Melanocratic ( 우흑질 ) - melanocratic 0-89 Melanocratic 6- Melanocratic ( 우흑질 ) - melanocratic 0-89 Melanocratic Ultramafic ( 초염기성 ) hypermelanic Hypermelanocratic Ultramafic ( 초염기성 ) hypermelanic Hypermelanocratic 2
Figure 2-1a. Method #1 for plotting a point with the components: 70% X, 20% Y, and % Z on triangular diagrams. An Introduction to Igneous and Metamorphic Petrology, John Winter, Prentice Hall. Figure 2-1b. Method #2 for plotting a point with the components: 70% X, 20% Y, and % Z on triangular diagrams. An Introduction to Igneous and Metamorphic Petrology, John Winter, Prentice Hall. Mode : mineral volume percentage (vol.%) 광물의종류와그양을결정 (point counting, areal or dimensional measurement; using modal counter option of microscope) 특정광물 vol.% = 특정광물면적 / 전체면적 *0 The Basis of Classification Classification of Igneous Rocks (a) The rock must contain a total of at least % of the minerals below. Renormalize to 0% Quartz-rich Granitoid Granite Q Quartzolite Granodiorite Peridotites 40 Pyroxenite Hornblendite 각암석의 image는 http://geology.com/rocks/ 사이트참조 용어는 http://ieg.or.kr 참조 Alkali Fs. 20 20 Qtz. Diorite/ Quartz Syenite Quartz Quartz Quartz Qtz. Gabbro Alkali Fs. Syenite Monzonite Monzodiorite Syenite Diorite/Gabbro/ Syenite 3 Monzonite 6 Monzodiorite Anorthosite A (Foid)-bearing (Foid)-bearing (Foid)-bearing P Syenite Monzonite Monzodiorite (Foid)-bearing Diorite/Gabbro (Foid)-bearing Alkali Fs. Syenite (Foid) (Foid) Monzosyenite Monzodiorite Pyroxene 0 Hornblend Pyroxene 40 Peridotite 0 Pyroxenite, Hornblendite gabbroid Anorthosites Pyroxene Figure 2-2. A classification of the phaneritic igneous rocks. a. Phaneritic rocks with more than % (quartz + feldspar + feldspathoids). After IUGS. (Foid)olites Figure 4.3. IUGS field classification of the phaneritic igneous rocks. F 3
Plagioclase Anorthosite Figure 2-2. A classification of the phaneritic igneous rocks. b. Gabbroic rocks. c. Ultramafic rocks. After IUGS. Classification of Igneous Rocks Q Rhyolite Dacite 20 20 gabbro Dunite Peridotites A Trachyte Latite Andesite/Basalt 6 3 P (foid)-bearing (foid)-bearing (foid)-bearing Trachyte Latite Andesite/Basalt Plagioclase-bearing ultramafic rocks Pyroxene (b) 40 Lherzolite Figure 2-3. A classification and nomenclature of volcanic rocks. After IUGS. Phonolite Tephrite Orthopyroxenite Websterite Pyroxenites (Foid)ites (c) Orthopyroxene Websterite Clinopyroxenite Clinopyroxene F IUGS 분류법의장점 국제기구에서고안되고채택된분류법 암석의종류를구별하는데필요한기준제공 널리사용 세종류의주요광물군 ( 석영 / 장석 / 준장석 ) 의함량비를기준 화성암과화성암처럼보이는암석을포함 자연적상호관계 와일치 가능한전통적인분류법을따름 사용하기에간단하고쉽다. IUGS 분류법의단점 석영이 20% 이상이며알칼리장석함량이높은암석들의세분이불가능 Q+A+P=0 or F+A+P=0 이기때문에다른광물의관여도는무시 임의의암석간의경계는관찰된내용과물리 / 화학적인함축성을배제할가능성높음 일부는화성암처럼보이는변성암을화성분류에포함시키는것이옳지않다고생각함 단순성은상대적인것임. 야외용임시분류체계역시삼각도법이므로실제로이용하기매우힘듦. Chemical Classification of Igneous Rocks Chemical 예 ) Harker diagram : SiO2 vs. other elements 화성암은화학적일관성을가지고있기때문에화학적성분에따른분류가가능하다. Harker variation diagram for 3 analyzed volcanic rocks from Crater Lake (Mt. Mazama), Oregon Cascades. Data compiled by Rick Conrey (personal communication). Figure 2-4. A chemical classification of volcanics based on total alkalis vs. silica. After Le Bas et al. (1986) J. Petrol., 27, 74-70. Oxford University Press. 4
Chemical ( 기타암석 ) LeMaitre plot. This plot combines silica saturation on the horizontal axis with peraluminous-peralkaline classification on the vertical. It's useful when rocks are too fine-grained for reliable mineral identification, ifi i have been metamorphosed, and so on.1 Figure 2-. Classification of the pyroclastic rocks. a. Based on type of material. After Pettijohn (197) Sedimentary Rocks, Harper & Row, and Schmid (1981) Geology, 9, 40-43. b. Based on the size of the material. After Fisher (1966) Earth Sci. Rev., 1, 287-298. 요약및정리 화성암을분류하는기준은? 조직 : 특히입자의크기 ( 현정질암석 / 비현정질암석 = 심성암 / 화산암 ) 구성광물 : 주구성광물 (IUGS 삼각도 ) 화학성분 : 특히 SiO 2 의함량, 그외에다른주원소함량도변화함. 기타 : 암편 ( 화산쇄설성암석 )