화성암이란??? Lecture 2 Igneous Rocks: Classifications Igneous rocks ( 화성암류 ) : 마그마로부터형성된결정질또는유리질암석 ( 냉각작 용및결정화작용 ) Magma : 화학적 / 물리학적으로복잡하고광물을만들수있는다양한분자들을포함하고있는고온의용융체 Classification of Igneous Rocks 왜암석을분류해야하나? (Fig. 시대별암석분류개수 ) Igneous rock = feldspathic rock + ferromagnesian rock( 장석 10%, 유색광물 90%, 색지수 ) 규장질중성고철질초고철질 화성암의종류에따라서생성환경이다르다. 너무많은사람들이다양한이름을이용. 분류학의필요성강조 ( 분류된암석종류판별 = 생성환경판단 ) Light color Igneous rock = feldspathic rock + ferromagnesian rock( 장석 10%, 유색광물 90%, 색지수 ) 규장질중성고철질초고철질 Igneous rock = feldspathic rock + ferromagnesian rock( 장석 10%, 유색광물 90%, 색지수 ) 규장질중성고철질초고철질 화강암 (granite) 반려암 (gabbro) 화강암 (granite) 섬록암 (diorite) 반려암 (gabbro) Light color Light color 유문암 (rhyolite) 현무암 (basalt) 유문암 (rhyolite) 안산암 (andesite) 현무암 (basalt) 1
Igneous rock = feldspathic rock + ferromagnesian rock( 장석 10%, 유색광물 90%, 색지수 ) 규장질중성고철질초고철질 요약및정리 화성암을분류하는기준은? 조직 : 특히입자의크기 ( 현정질암석 / 비현정 감람암 (peridotite) 질암석 = 심성암 / 화산암 ) 구성광물 : 주구성광물 화강암 (granite) 섬록암 (diorite) 반려암 (gabbro) 화학성분 : 특히 SiO 2 의함량, 그외에다른주 원소함량도변화함. 기타 : 암편 ( 화산쇄설성암석 ) Light color 유문암 (rhyolite) 안산암 (andesite) 현무암 (basalt) Plate Tectonic - Igneous Genesis 1. 중앙해령 2. 대륙열곡 3. 호상열도 4. 대륙충돌경계 5. 배호분지 6. 해양화산섬 7. 판내부화산활동 kimberlites, carbonatites, anorthosites... Magma 맨틀또는하부지각에서형성됨. 주변과의밀도차이등으로인해서지표로상승이동 다양한환경에따라서여러가지암석이만들어짐 Volcanic rocks( 화산암 ) : 분출, 지표근처에서결정화 Plutonic rocks( 심성암 ) : 심부에서결정화작용됨. 화성암의구분및명명법 화성암의인지과정 Texture ( 조직 ) Structure ( 구조 ) Composition ( 성분 ) 입자크기정도스케일에서암석의특징 ( 입자크기, 모양, 방향성, 분포, 상호간의관계등을관찰 ) 입자크기보다큰규 주원소 (Major element) 모의스케일에서특미량원소 (Trace element) 징희토류원소 (Rare earth ( 물리적인배열, 엽리, element; REE) 구멍, 균열, 단층, 습동위원소 (Isotope) 곡등을관찰 ) Structure 물리적특징 화학적특징 Texture Sampling Microscopic analysis Chemical analysis 2
화성암의구조 (Structure) : 마그마분출로인하여형성된구조 ( 대부분화산또는 ) 대, 중, 소구조로구분 유리질 - 세립질, 화성암의구조 (Structure) 분출암 냉각주변상은바닦에국한 세립 - 조립질 관입암 냉각주변상은암체의가장자리 ( 내부보다세립 ) 암체하부의산화토대와약한변성작용산화토대없고, 넓은접촉변성작용 관입구조 : 지표의아래에서형성된구조 표면이불규칙, 상위에퇴적물 ( 암 ) 하위암석의암편포함기공이나행인주변암석의변형유발없음 암체의표면이불규칙포획암기공과행인없음주변암석의변형유발 Structures and Field Relationships 대구조 : 용암대지 / 현무암평원, 화성쇄설암상 ( 혼합형 ), 순상화산, 혼합화산구 ( 층상화산 ) Volcanic landforms associated with a central vent (all at same scale). Basaltic plain 대구조 : 용암대지 / 현무암평원, 화성쇄설암상 ( 혼합형 ), 순상화산, 혼합화산구 ( 층상화산 ) 대구조 : 용암대지 / 현무암평원, 화성쇄설암상 ( 혼합형 ), 순상화산, 혼합화산구 ( 층상화산 ) Shield volcano pyroclastic sheet 3
대구조 : 용암대지 / 현무암평원, 화성쇄설암상 ( 혼합형 ), 순상화산, 혼합화산구 ( 층상화산 ) Mt. Fuji 분화구 / 칼데라 Strata volcano Caldera & resurgent caldera (Cf. cauldron & resurgent cauldron, craters) 중구조 : 화성암설구 ( 분석구 ), 용암류, 도옴 중구조 : 화성암설구 ( 분석구 ), 도옴 (dome), 용암류 The photo shows the eruption of Paricutin V olcano, Mexico, a classic example of a cinder cone. Lava dome(volcanic dome) formed by the in-,ex-trusion or both of viscous siliceous magm a. 중구조 : 화성암설구 ( 분석구 ), dome, 용암류 용암류 Pahoehoe lava : smooth, vesicular, ropy surface. Aa lava : rough, irregular flow tops, loose fragment 4
소구조 : 분화구, 리소피시 (Lithophysae), 화산압력구릉 (Pressure ridge), 용암동굴 (Lava tube), 주상절리 (Columnar joint), 유동띠 (Flow banding), 화산탄 (Bomb) Columnar joint : pencil-like cooling structure. Figure 4-13. a. Schematic drawing of columnar joints in a basalt flow, showing the four common subdivisions of a typical flow. The column widths in (a) are exaggerated about 4x. After Long and Wood (1986) Geol. Soc. Amer. Bull., 97, 1144-1155. b. Colonnade-entablature-colonnade in a basalt flow, Crooked River Gorge, OR. John Winter and Prentice Hall. 소구조 : 분화구, 리소피시 (Lithophysae), 화산압력구릉 (Pressure ridge), 용암동굴 (Lava tube), 주상절리 (Columnar joint), 유동띠 (Flow banding), 화산탄 (Bomb) 소구조 : 리소피시 (Lithophysae) Pillow lava : extruded under water Lithophsae : Hollow, bubble-like, or roselike spherulites, usually with a concentric structure, that occur in rhyolite, obsidian, and related rocks. (Cf: lithophysa.) 5
Small Structure : Small Structure : Baked zone ( 산화토대 ) : weathering of a flow surface followed by extrusion of hot lava over the soil developed on the weathered surface will produce a brick-red zone of oxidized material 동원포획암 & 포획암 Small Structure : Small Structure : 기공 & 행인 Flow banding ( 유동띠 ) 소구조 : 화산쇄설물 쇄설물 화산회 화산력 화산탄, 암괴 직경 ~ 2mm 2 ~ 64 64 ~ Bomb Lapilli Figure 4-18. Types of pyroclastic flow deposits. After MacDonald (1972), Volcanoes. Prentice- Hall, Inc., Fisher and Schminke (1984), Pyroclastic Rocks. Springer-Verlag. Berlin. a. collapse of a vertical explosive or plinian column that falls back to earth, and continues to travel along the ground surface. b. Lateral blast, such as occurred at Mt. St. Helens in 1980. c. Boiling-over of a highly gas-charged magma from a vent. d. Gravitational collapse of a hot dome (Fig. 4-18d). Ash 6
관입구조 (Table 2.3) 대구조저반 (batholith), 암주 (Stock), 분상암체 (Lopolith), 현수체 (Roof pendent) 중구조암주, 암맥 (dike), 원추형관입암상 (Cone Sheet), 암경 (Pipe, neck, vent), 깔때기형암체 (Funnel), 큐폴라 (Cupola), 관입암상 (Sill), 병반 (Laccolith), 패콜리스 (Phacolith), 현수체, 쉬리에렌도옴 (Schlieren dome)/ 아치 (arch) 소구조암맥, 돌기암맥 (Apophysis), 맥 (Vein), 관입암상, 엽리 (foliation), 쉬리에렌, 포획암, 동원포획암, 화성성층 (Layering), 선구조 (Lineation) Figure 4-16. Approximate aerial extent and thickness of Mt. Mazama (Crater Lake) ash fall, erupted 6950 years ago. After Young (1990), Unpubl. Ph. D. thesis, University of Lancaster. UK. Intrusive structure (Table 2.3) : Major structure 심성암체 (Pluton) : 심성암으로구성된암체를나타내는일반적인형식으로, 화강암질 (granitic) 조직을갖는다. 화강암질조직 : 화강암및이와관련된암석들의조직적특징을총칭하는말이다 ( 화강암을생각하면됨 ; 괴상, 등립질의중립질이상의암석 ). Batholith ( 저반 ) : plutonic bodies having map area of 100 km 2 and more. Cf) Stock : less than 100 km 2 mainly composed of granitic rocks Earlier idea(fig. 2.11c) : Steep-side, sylinderlike, great depth(bottomless) Ex. Sierran crust : elongated tabular or lensshaped batholith (<30 km thickness) Intrusive structure Batholith and stock in South Korea Red area : Daebo granite purple area : Bulkuksa granite 7
a) Lopolith( 분상암체 ) : 대규모의접시모양의층상관입암체 (uncommon, economic) b) Sill( 관입암상 ) : 층의경계사이를관입한편판형의암체 c) Laccolith( 병반 ) : 층의경계사이를관입한위로볼록한렌즈모양의관입암체 d) Dike( 암맥 ) : 부조화적인평판형관입암체 Roof pendant( 현수체 ) : 관입암체위에놓인형상의고기변성암이나퇴적암 Schlieren(flow layer) domes and arches : tabular, diffuse, disklike concentration of minerals within an igneous rock mass Cupolar : dome-shaped projection of igneous rock of a batholith Apophysis(offshoot; 돌기 ) : intrusion detached from its source a) Lopolith( 분상암체 ) : large, dishshape, layerd intrusion.(uncommon, economic) The sill and dike with xenolith in the Precambrian basement rock. Yeoncheon, South Korea. Dike( 암맥 ) : 복합적암맥 d) 암전 (bysmalith ): A roughly vertical cylindrical igneous intrusion, bounded by steep faults. It has been interpreted as a type of laccolith. Cf: bell-jar intrusion e) 패콜리스 (Phacolith) : lenticular intrusions, along fold axes 8
Virginia Dale ring dike f) Funnel : solid plutonic bodies in shich the layering dips inward, just as do the dikes of cone sheets. g) Cone sheet( 원추형관입암상 ) : downward-pointing cones in form Ring dike( 환상암맥 ) : verticlal, cylindrical in form 모두 cauldron collapse 와관련깊음 Figure 4-23. The formation of ring dikes and cone sheets. a. Cross section of a rising pluton causing fracture and stoping of roof blocks. b. Cylindrical blocks drop into less dense magma below, resulting in ring dikes. c. Hypothetical map view of a ring dike with N-S striking country rock strata as might result from erosion to a level approximating X- Y in (b). d. Upward pressure of a pluton lifts the roof as conical blocks in this cross section. Magma follows the fractures, producing cone sheets. Original horizontal bedding plane shows offsets in the conical blocks. (a), (b), and (d) after Billings (1972), Structural Geology. Prentice-Hall, Inc. (c) after Compton (1985), Geology in the Field. Wiley. New York. Major structure Volcanic neck (pipe, vent; 암경 ) : residue of erosion at volcanic cone. Figure 4-24. b. Cone sheets in the same area of Mull, after Ritchey (1961), British Regional Geology. Scotland, the Tertiary Volcanic Districts. Note that the yellow felsite ring dike in part (a) is shown as the red ring in the NW of part (b). British Geological Survey. vein : tabular bodies form fracture fillings(dike type). that consist of 1-2 minerals (quartz or calcite) Foliation( 엽리 ) Lineation( 선구조 ) layering( 화산성층 ) Textures of Igneous Rocks 조직 ( 미시적인특징 ) 9
Texture of Igneous Rocks Igneous rock = glass ± crystal ±fragment Photomicrograph of hypocrystalline texture crystal glass Fig. 2.19. Igneous rock texture plotted in terms of crystallinity and grain size. Arrows indicate a range of grain size within a single rock Photograph of holohyaline texture 현정질 (phaneritic) 과비현정질 (aphanitic) 현정질 (phaneritic) 과비현정질 (aphanitic) 현정질과비현정질암석의육안관찰 현정질과비현정질암석의현미경사진 Pegmatitic( 페그마타이트질 ; 거정질 ) 반상 (porphyritic) 조직 : 반정 + 석기 10
감람석반상현무암 : 감람석의반정과미립의감람석및사장석의석기로구성 Width = 6 mm. Maui, Hawaii. Aphyric( 무반정상 ) : 화산암류는반정이없음 (opp. phyric; 반정상 ) Microphyric ( 미반상 ): 반정 (phenocrysts) 과석기 (groundmass) 가비현정질 Cf) 비현정질반상조직, 현정질반상조직 11