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Metamorphic texture

변성암의 조직

변성 조직 (Metamorphic Textures)조직 : 작은 스케일의 통찰력 있는 특징잔류 조직

　 원암의 조직이 남아 있는 것

　 “-blasto-” = relict

　 Any degree of preservation

　 광물의 가상 또는 변성작용

이전의 조직/구조Fig. 6. Xenolith of amphibolite after basic granulite with a reaction rim in enderbite-charnockite. Point Cherny.

변형(deformation), 재생(recovery) 및 재결정 작

용(recrystallization)

1. 압쇄 구조

• 기계적인 파쇄작용 및 광물들의 미끄러짐이나 회전으로

만들어짐.

• 변형 쌍정, 압쇄, 깨짐, 구부러짐(bend), 갈림(분쇄), 꺾임

(kink), 파동소광(undulose extinction), 운모류들의 부서

짐, 안구상 구조, 모르타르 조직 등

• 꼭 변성암에서만 발생되는 조직은 아님. (변성작용이 아

닐 수도 있음)

꺽임꺽임구조구조 (kink band)(kink band)

Figure 23-30. Kink bands involving cleavage in deformed chlorite. Inclusions are quartz (white), and epidote (lower right). Field of view ~ 1 mm. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.

구부러짐구부러짐 (( bend)bend)

Figure 23-8. Gneissic anorthositic-amphibolite (light color on right) reacts to become eclogite (darker on left) as left-lateral shear transposes the gneissosity and facilitates the amphibolite-to-eclogite reaction. Bergen area, Norway. Two-foot scale courtesy of David Bridgwater. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.

모르타르모르타르구조구조또는또는분쇄분쇄

Figure 23-16b. Vein-like pseudotachylite developed in gneisses, Hebron Fjord area, N. Labrador, Canada. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.

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변형(deformation), 재생(recovery) 및 재결정 작용(recrystallization)

2. Pressure Solution

Figure 23-2 a. Highest strain in areas near grain contacts (hatch pattern). b. High-strain areas dissolve and material precipitates in adjacent low-strain areas (shaded). The process is accompanied by vertical shortening. c. Pressure solution of a quartz crystal in a deformed quartzite (σ1 is vertical). Pressure solution results in a serrated solution surface in high-strain areas (small arrows) and precipitation in low-strain areas (large arrow). ~ 0.5 mm across. The faint line within the grain is a hematite stain along the original clast surface. After Hibbard (1995) Petrography to Petrogenesis. Prentice Hall.

결정 결함들의 이동은 아결정을 형성

Figure 23-5. Illustration of a recovery process in which dislocations migrate to form a subgrain boundary. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.

Figure 23-4 a. Undulose extinction and (b) elongate subgrains in quartz due to dislocation formation and migration Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.

aa bb

입자 경계 주변에 발생한 재결정

Figure 23-6. Recrystallization by (a) grain-boundary migration (including nucleation) and (b) subgrain rotation. From Passchier and Trouw (1996) Microtectonics. Springer-Verlag. Berlin.

Figure 23-7a. Recrystallized quartz with irregular (sutured) boundaries, formed by grain boundary migration. Width 0.2 mm. From Borradaile et al. (1982).

높은 응력에서 변성 조직

응력에따른형태의변화가암석에그대로

보존됨.

압력은광물입자의크기를줄여주는역할

취성변형과연성변형 (취성변형이천부)

aa

bb

Figure 23-15. Progressive mylonitization of a granite. From Shelton (1966). Geology Illustrated. Photos courtesy © John Shelton.

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cc

dd

Figure 23-15. Progressive mylonitization of a granite. From Shelton (1966). Geology Illustrated. Photos courtesy © John Shelton.

Figure 22-3. Terminology for high-strain shear-zone related rocks proposed by Wise et al. (1984) Fault-related rocks: Suggestions for terminology. Geology, 12, 391-394.

접촉 변성작용에서 조직

전형적으로천부의심성암체주변(aureoles; low-P)

전형적으로열에의한변성작용은결정의크기를

증가시켜주는역할을함.

결정작용및재결정작용은거의정적임. 등방성조직

발달 (hornfels, granofels)

잔류구조발달(Relict texture)

1Progressive thermal metamorphism of a diabase (SiO2 ~ 50wt.%; coarse basalt). From Best (1982). Igneous and Metamorphic Petrology. W. H. Freeman. San Francisco.

2Progressive thermal metamorphism of a diabase (SiO2 ~ 50wt.%; coarse basalt). From Best (1982). Igneous and Metamorphic Petrology. W. H. Freeman. San Francisco.

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3Progressive thermal metamorphism of a diabase (SiO2 ~ 50wt.%; coarse basalt). From Best (1982). Igneous and Metamorphic Petrology. W. H. Freeman. San Francisco.

4Progressive thermal metamorphism of a diabase (coarse basalt). From Best (1982). Igneous and Metamorphic Petrology. W. H. Freeman. San Francisco.

1slate

Progressive thermal metamorphism of slate. From Best (1982). Igneous and Metamorphic Petrology. W. H. Freeman. San Francisco.

2slate

Progressive thermal metamorphism of slate. From Best (1982). Igneous and Metamorphic Petrology. W. H. Freeman. San Francisco.

3slate

Progressive thermal metamorphism of slate. From Best (1982). Igneous and Metamorphic Petrology. W. H. Freeman. San Francisco.

The The CrystalloblasticCrystalloblastic SeriesSeriesMost Euhedral Most Euhedral ((자형자형))

Titanite, rutile, pyrite, spinel

Garnet, sillimanite, staurolite, tourmaline

Epidote, magnetite, ilmenite

Andalusite, pyroxene, amphibole

Mica, chlorite, dolomite, kyanite

Calcite, vesuvianite, scapolite

Feldspar, quartz, cordierite

Least EuhedralLeast Euhedral ((타형타형))

Differences in development of crystal form among some metamorphic minerals. From Best (1982). Igneous and Metamorphic Petrology. W. H. Freeman. San Francisco.

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Figure 23-9. Typical textures of contact metamorphism. From Spry (1969) Metamorphic Textures. Pergamon. Oxford.

aa bb

Figure 23-52. a. Mesh texture in which serpentine (dark) replaces a single olivine crystal (light) along

irregular cracks. b. Serpentine pseudomorphs orthopyroxene to form bastite in the upper portion of

photograph, giving way to mesh olivine below. Field of view ca. 0.1 mm. Fidalgo sepentinite, WA state.

Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.

Fig. 23-10 Grain boundary energy controls triple point angles

c.

Figure 23-10. a. Dihedral angle between two mineral types. When the A-A grain boundary energy is greater than for A-B, the angle θ will decrease (b) so as to increase the relative area of A-B boundaries. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall. c. Sketch of a plagioclase (light)-clinopyroxene (dark) hornfels showing lower dihedral angles in clinopyroxene at most cpx-plag-plag boundaries. (c. from Vernon, 1976) Metamorphic Processes: Reactions and Microstructure Development. Allen & Unwin, London.

Figure 23-11. Drawings of quartz-mica schists. a. Closer spacing of micas in the lower half causes quartz grains to passively elongate in order for quartz-quartz boundaries to meet mica (001) faces at 90o. From Shelley (1993). b. Layered rock in which the growth of quartz has been retarded by grain boundary “pinning” by finer micas in the upper layer. From Vernon, 1976) Metamorphic Processes: Reactions and Microstructure Development. Allen & Unwin, London.

a

b

Metamorphic Textures• 여러 번의 변성작용은 광물 조직이나 조성으로

흔적이 남는다.

• 접촉변성작용 이전의 변성/변형의 흔적을 보존

하는 경우가 많음.

• 보통 대륙 충돌대에서는 최대 압력 조건 이후 최

대 온도의 변성작용을 수반함.

• Nodular overprints

• Spotted slates and phyllites

a

b

Figure 23-14. Overprint of contact metamorphism on regional. a. Nodular texture of cordierite porphyroblasts developed during a thermal overprinting of previous regional metamorphism (note the foliation in the opaques). Approx. 1.5 x 2 mm. From Bard (1986) Microtextures of Igneous and Metamorphic Rocks. Reidel. Dordrecht. b. Spotted phyllite in which small porphyroblasts of cordierite develop in a preexisting phyllite. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.

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Depletion haloesDepletion haloes

Progressive development of a depletion halo about a growing porphyroblast. From Best (1982). Igneous and Metamorphic Petrology W HMetamorphic Petrology. W. H. Freeman. San Francisco.

Figure 23-13. Light colored depletion haloes around cm-sized garnets in amphibolite. Fe and Mg were less plentiful, so that hornblende was consumed to a greater extent than was plagioclase as the garnets grew, leaving hornblende-depleted zones. Sample courtesy of Peter Misch. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall.

Depletion halo around garnet porphyroblast. Boehls Butte area, Idaho

광역 변성작용에서의 조직–Dynamothermal (crystallization under dynamic conditions)

–조산운동(Orogeny) : 장기간동안 산맥을 형성하는 작용.

–여러가지 지구조 운동(Tectonic Events) 다양한 변형 작용

–하나이상의 반응작용과 함께 변성과정이 발생함.

1. 텍토나이트(Tectonite) : 변형작용을 기록하

고 있는 조직이 존재하는 암석.

2. 석리(Fabric) : 조직적 요소들의 완벽한 공간

적/기하학적 배치

광역 변성작용에서의 조직

적/기하학적 배치

1. 엽리(Foliation) : planar textural element

2. 선리(Lineation) : linear textural element

3. Lattice Preferred Orientation (LPO)

4. Dimensional Preferred Orientation (DPO)

1Volcanic graywacke

Progressive syntectonic metamorphism of a volcanic graywacke, New Zealand.From Best (1982). Igneous and Metamorphic Petrology. W. H. Freeman. San Francisco.

2Volcanic graywacke

Progressive syntectonic metamorphism of a volcanic graywacke, New Zealand.From Best (1982). Igneous and Metamorphic Petrology. W. H. Freeman. San Francisco.

3Volcanic graywacke

Progressive syntectonic metamorphism of a volcanic graywacke, New Zealand.From Best (1982). Igneous and Metamorphic Petrology. W. H. Freeman. San Francisco.

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4Volcanic graywacke

Progressive syntectonic metamorphism of a volcanic graywacke, New Zealand.From Best (1982). Igneous and Metamorphic Petrology. W. H. Freeman. San Francisco.

Fig 23-21 Types of foliations

a. Compositional layeringb. Preferred orientation of platy

mineralsc. Shape of deformed grainsd. Grain size variatione. Preferred orientation of platy

minerals in a matrix withoutminerals in a matrix without preferred orientation

f. Preferred orientation of lenticular mineral aggregates

g. Preferred orientation of fracturesh. Combinations of the above

Figure 23-21. Types of fabric elements that may define a foliation. From Turner and Weiss (1963) and Passchier and Trouw (1996).

a

b

Figure 23-23. Continuous schistosity developed by dynamic recrystallization of biotite, muscovite, and quartz. a. Plane-polarized light, width of field 1 mm. b.Crossed-polars, width of field 2 mm. Although there is a definite foliation in both samples, the minerals are entirely strain-free.

Figure 23-22. A morphological (non-genetic) classification of foliations. After Powell (1979) Tectonophys., 58, 21-34; Borradaile et al. (1982) Atlas of Deformational and Metamorphic Rock Fabrics. Springer-Verlag; and Passchier and Trouw (1996) Microtectonics. Springer-Verlag.

Figure 23-22. (continued)

Progressive development (a → c) of a crenulation cleavage for both

i ( ) iasymmetric (top) and symmetric (bottom) situations. From Spry (1969) Metamorphic Textures. Pergamon. Oxford.

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Figure 23-24a. Symmetrical crenulation cleavages in amphibole-quartz-rich schist. Note concentration of quartz in hinge areas. From Borradaile et al. (1982) Atlas of Deformational and Metamorphic Rock Fabrics. Springer-Verlag.

Figure 23-24b. Asymmetric crenulation cleavages in mica-quartz-rich schist. Note horizontal compositional layering (relict bedding) and preferential dissolution of quartz from one limb of the folds. From Borradaile et al. (1982) Atlas of Deformational and Metamorphic Rock Fabrics. Springer-Verlag.

Figure 23-25. Stages in the development of crenulation cleavage as a function of t t d i t it f th d

Development of SDevelopment of S22 micas depends upon T micas depends upon T and the intensity of the second deformationand the intensity of the second deformation

temperature and intensity of the second deformation. From Passchier and Trouw (1996) Microtectonics. Springer-Verlag.

Types of lineationsTypes of lineationsa. Preferred orientation of

elongated mineral aggregates

b. Preferred orientation of elongate minerals

c. Lineation defined by platy minerals

d. Fold axes (especially of crenulations)

e. Intersecting planar elements.

Figure 23-26. Types of fabric elements that define a lineation. From Turner and Weiss (1963) Structural Analysis of Metamorphic Tectonites. McGraw Hill.

Figure 23-27. Proposed mechanisms for the development of foliations. After Passchier and Trouw (1996) Microtectonics. Springer-Verlag.

Figure 23-28. Development of foliation by simple shear and pure shear (flattening). After Passchier and Trouw (1996) Microtectonics. Springer-Verlag.

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Development of an axial-planar cleavage in folded metasediments. Circular images are microscopic views showing that the axial-planar cleavage is a crenulation cleavage, and is developed preferentially in the micaceous layers. From Gilluly, Waters and Woodford (1959) Principles of Geology, W.H. Freeman; and Best (1982). Igneous and Metamorphic Petrology. W. H. Freeman. San Francisco.

Diagram showing that structural and fabric elements are generally consistent in style and orientation at all scales. From Best (1982). Igneous and Metamorphic Petrology. W. H. Freeman. San Francisco.

PrePre--kinematic kinematic crystalscrystals

a. Bent crystal with undulose extinction

b. Foliation wrapped around a porphyroblast

c. Pressure shadow or fringe

d. Kink bands or folds

e. Microboudinagef. Deformation

twins

Figure 23-34. Typical textures of pre-kinematic crystals. From Spry (1969) Metamorphic Textures. Pergamon. Oxford.

PostPost--kinematic crystalskinematic crystalsa. Helicitic folds b. Randomly oriented crystals c. Polygonal arcs

d. Chiastolite e. Late, inclusion-free rim on a poikiloblast (?) f. Random aggregate pseudomorph

Figure 23-35.Typical textures of post-kinematic crystals. From Spry (1969) Metamorphic Textures. Pergamon. Oxford.

SynSyn--kinematic kinematic crystalscrystalsParacrystalline microboudinageParacrystalline microboudinage Spiral PorphyroblastSpiral Porphyroblast

Figure 23-36. Syn-crystallization micro-boudinage. Syn-kinematic crystal growth can be demonstrated by the color zoning that grows and progressively fills the gap between the separating fragments. After Misch (1969) Amer. J. Sci., 267, 43-63.

Figure 23-38. Traditional interpretation of spiral Si train in which a porphyroblast is rotated by shear as it grows. From Spry (1969) Metamorphic Textures. Pergamon. Oxford.

SynSyn--kinematic crystalskinematic crystals

Figure 23-38. Spiral Si train in garnet, Connemara, Ireland. Magnification ~20X. From Yardley et al. (1990) Atlas of Metamorphic Rocks and their Textures. Longmans.

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SynSyn--kinematic crystalskinematic crystals

Figure 23-40. Non-uniform distribution of shear strain as proposed by Bell et al. (1986) J. Metam. Geol., 4, 37-67. Blank areas represent high shear strain and colored areas are low-strain. Lines represent initially horizontal inert markers (S1). Note example of porphyroblast growing preferentially in low-strain regions.

SynSyn--kinematic crystalskinematic crystals

Figure 23-38.“Snowball garnet” with highly rotated spiral Si. Porphyroblast is ~ 5 mm in diameter. From Yardley et al. (1990) Atlas of Metamorphic Rocks and their Textures. Longmans.

Figure 23-37. Si characteristics of clearly pre-, syn-, and post-kinematic crystals as proposed by Zwart (1962). a. Progressively flattened Si from core to rim. b. Progressively more intense folding of Si from core to rim. c. Spiraled Si due to rotation of the matrix or the porphyroblast during growth. After Zwart (1962) Geol. Rundschau, 52, 38-65.

Analysis of Deformed Rocks

Figure 23-42. (left) Asymmetric

icrenulation cleavage (S2) developed over S1cleavage. S2 is folded, as can be seen in the dark sub-vertical S2bands. Field width ~ 2 mm. Right: sequential analysis of the development of the textures. From Passchier and Trouw (1996) Microtectonics. Springer-Verlag.

Figure 23-46. Textures in a hypothetical andalusite porphyryoblast-mica schist. After Bard (1986) Microtextures of Igneous and Metamorphic Rocks. Reidel. Dordrecht.

Figure 23-47. Graphical analysis of the relationships between deformation (D), metamorphism (M), mineral growth, and textures in the rock illustrated in Figure 23-46. Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall. Figure 23-48a. Interpreted sequential development of a polymetamorphic rock. From Spry (1969)

Metamorphic Textures. Pergamon. Oxford.

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Figure 23-48b. Interpreted sequential development of a polymetamorphic rock. From Spry (1969) Metamorphic Textures. Pergamon. Oxford.

Figure 23-48c. Interpreted sequential development of a polymetamorphic rock. From Spry (1969) Metamorphic Textures. Pergamon. Oxford.

Post-kinematic: Si is identical to and continuous with Se

Pre-kinematic: Porphyroblasts are post-S2. Si is inherited from an earlier deformation. Se is compressed about the

From Yardley (1989) An Introduction to Metamorphic Petrology. Longman.

pporphyroblast in (c) and a pressure shadow develops.

Syn-kinematic: Rotational porphyroblasts in which Si is continuous with Se suggesting that deformation did not outlast porphyroblast growth.

Figure 23-53. Reaction rims and coronas. From Passchier and Trouw (1996) Microtectonics.

Figure 23-54. Portion of a multiple coronite developed as concentric rims due to reaction at what was initially the contact between an olivine megacryst and surrounding plagioclase in anorthosites of the upper Jotun Nappe, W. Norway. From Griffen (1971) J. Petrol., 12, 219-243.

Photomicrograph of multiple reaction rims between olivine (green, left) and plagioclase (right).

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Coronites in outcrop. Cores of orthopyroxene (brown) with successive rims of clinopyroxene (dark green) and garnet (red) in an anorthositic matrix. Austrheim, Norway.