Ductile Shear Zones: From Micro- to Macro-scales

626 Pages·2015·123.043 MB·English

by  Soumyajit Mukherjee, Kieran F. Mulchrone

Table of Contents
Cover
Title Page
Contributors
Acknowledgments
Introduction
REFERENCES
PART I: Theoretical Advances and New Methods
Chapter 1: From finite to incremental strain: Insights into heterogeneous shear zone
evolution
1.1 INTRODUCTION
1.2 INCREMENTAL STRAIN
1.3 FINITE STRAIN
1.4 PRACTICAL APPLICATION OF INCREMENTAL AND FINITE STRAIN
ANALYSES
1.5 CONCLUSIONS
ACKNOWLEDGMENTS
REFERENCES
Chapter 2: How far does a ductile shear zone permit transpression?
2.1 INTRODUCTION
2.2 FIELD OBSERVATIONS: GEOMETRIC ANALYSIS
2.3 SHEAR ZONE KINEMATICS: ANALOG EXPERIMENTS
2.4 FINITE ELEMENT MODELING
2.5 DISCUSSION
2.6 CONCLUSIONS
ACKNOWLEDGMENTS
REFERENCES
Chapter 3: 2D model for development of steady-state and oblique foliations in simple
shear and more general deformations
3.1 INTRODUCTION
3.2 MODELING STEADY-STATE AND OBLIQUE FOLIATION
DEVELOPMENT
3.3 ANALYSIS OF THE MODEL
3.4 COMPARISON WITH NATURAL AND EXPERIMENTAL DATA
3.5 DISCUSSION AND CONCLUSION
ACKNOWLEDGMENTS
REFERENCES
Chapter 4: Ductile deformation of single inclusions in simple shear with a finite-strain
hyperelastoviscoplastic rheology
4.1 INTRODUCTION
4.2 METHODS
4.3 RESULTS
4.4 DISCUSSION
ACKNOWLEDGMENTS
REFERENCES
Chapter 5: Biviscous horizontal simple shear zones of concentric arcs (Taylor–Couette
flow) with incompressible Newtonian rheology
5.1 INTRODUCTION
5.2 THE MODEL
ACKNOWLEDGMENTS
REFERENCES
PART II: Examples from Regional Aspects
Chapter 6: Quartz-strain-rate-metry (QSR), an efficient tool to quantify strain
localization in the continental crust
6.1 INTRODUCTION
6.2 METHODS
6.3 GEOLOGICAL SETTING
6.4 STRAIN RATE MEASUREMENTS IN NATURAL SHEAR ZONES
6.5 DISCUSSION
6.6 CONCLUSIONS
ACKNOWLEDGMENTS
REFERENCES
Chapter 7: Thermal structure of shear zones from Ti-in-quartz thermometry of
mylonites: Methods and example from the basal shear zone, northern Scandinavian
Caledonides
7.1 INTRODUCTION
7.2 BACKGROUND
7.3 METHODS
7.4 RESULTS
7.5 DISCUSSION
ACKNOWLEDGMENTS
REFERENCES
Chapter 8: Brittle-ductile shear zones along inversion-related frontal and oblique thrust
ramps: Insights from the Central–Northern Apennines curved thrust system (Italy)
8.1 INTRODUCTION
8.2 REGIONAL GEOLOGY
8.3 BRITTLE–DUCTILE THRUST SHEAR ZONES IN THE APENNINES: A
BRIEF REVIEW
8.4 DEFORMATION SHEAR FABRICS WITHIN CURVED THRUSTS
8.5 DISCUSSIONS AND CONCLUSIONS
ACKNOWLEDGMENTS
REFERENCES
Chapter 9: Microstructural variations in quartzofeldspathic mylonites and the problem
of vorticity analysis using rotating porphyroclasts in the Phulad Shear Zone, Rajasthan,
India
9.1 INTRODUCTION
9.2 MICROSTRUCTURAL VARIATION IN QUARTZOFELDSPATHIC
MYLONITES
9.3 PROBLEM OF USING ROTATING PORPHYROCLASTS FOR VORTICITY
ANALYSIS IN THE PHULAD SHEAR ZONE
9.4 CONCLUSIONS
ACKNOWLEDGMENTS
REFERENCES
Chapter 10: Mineralogical, textural, and chemical reconstitution of granitic rock in
ductile shear zones
10.1 INTRODUCTION
10.2 GEOLOGY OF THE AREA
10.3 STUDY AREA
10.4 FIELD FEATURES OF THE STUDIED GRANITE
10.5 MICROSTRUCTURES AND MINERAL DEFORMATION BEHAVIOR
10.6 REACTION TEXTURES
10.7 MINERAL CHEMISTRY
10.8 CHEMICAL REACTIONS AND MASS TRANSPORT DURING
MYLONITIZATION
10.9 MASS TRANSFER
10.10 PHYSICAL CONDITIONS OF SHEARING
10.11 DISCUSSION
ACKNOWLEDGMENTS
ABBREVIATIONS
REFERENCES
Chapter 11: Reworking of a basement–cover interface during Terrane Boundary
shearing: An example from the Khariar basin, Bastar craton, India
11.1 INTRODUCTION
11.2 GEOLOGICAL SETTING
11.3 DEFORMATION PATTERN AND FABRIC RELATIONSHIP
11.4 MICROSTRUCTURE AND QUARTZ C-AXIS PATTERNS
11.5 P–T CONDITION ACROSS THE FORELAND
11.6 DISCUSSION
11.7 CONCLUSIONS
ACKNOWLEDGMENT
REFERENCES
Chapter 12: Intrafolial folds: Review and examples from the western Indian Higher
Himalaya
12.1 INTRODUCTION
12.2 GEOLOGY AND TECTONICS OF THE STUDY AREAS
12.3 REVIEW OF INTRAFOLIAL FOLDS
12.4 PRESENT STUDY
12.5 DISCUSSION AND CONCLUSIONS
ACKNOWLEDGMENTS
REFERENCES
Chapter 13: Structure and Variscan evolution of Malpica–Lamego ductile shear zone
(NW of Iberian Peninsula)
13.1 INTRODUCTION
13.2 GEOLOGICAL SETTING
13.3 STRUCTURAL DESCRIPTION AND INTERPRETATION
13.4 CONCLUSIONS
REFERENCES
Chapter 14: Microstructural development in ductile deformed metapelitic–
metapsamitic rocks: A case study from the greenschist to granulite facies megashear
zone of the Pringles Metamorphic Complex, Argentina
14.1 INTRODUCTION
14.2 GEOLOGICAL SETTING
14.3 FIELD ASPECT AND PETROGRAPHY
14.4 PHASE RELATIONS
14.5 GEOTHERMOBAROMETRY
14.6 MECHANISMS OF MICROSTRUCTURAL DEVELOPMENT
14.7 DISCUSSION
14.8 CONCLUSIONS
ACKNOWLEDGMENTS
REFERENCES
Chapter 15: Strike–slip ductile shear zones in Thailand
15.1 INTRODUCTION
15.2 TECTONIC FRAMEWORK OF THAILAND
15.3 STRUCTURAL GEOLOGY OF THESTRIKE–SLIP DUCTILE SHEAR
ZONES
15.4 GEOCHRONOLOGY
15.5 DISCUSSION
15.6 CONCLUSIONS
ACKNOWLEDGMENTS
REFERENCES
Chapter 16: Geotectonic evolution of the Nihonkoku Mylonite Zone of north central
Japan based on geology, geochemistry, and radiometric ages of the Nihonkoku
Mylonites: Implications for Cretaceous to Paleogene tectonics of the Japanese Islands
16.1 INTRODUCTION
16.2 GEOLOGY OF THE NIHONKOKU MYLONITE ZONE
16.3 PETROGRAPHY OF THE NIHONKOKU MYLONITES AND RELATED
ROCKS
16.4 STRUCTURE OF THE NIHONKOKU MYLONITE ZONE
16.5 GEOCHEMISTRY OF THE NIHONKOKU MYLONITES AND RELATED
ROCKS
16.6 RADIOMETRIC AGES OF THE NIHONKOKU MYLONITES AND
RELATED ROCKS
16.7 DISCUSSION
16.8 SUMMARY
ACKNOWLEDGMENTS
REFERENCES
Chapter 17: Flanking structures as shear sense indicators in the Higher Himalayan
gneisses near Tato, West Siang District, Arunachal Pradesh, India
17.1 INTRODUCTION
17.2 GEOLOGY
17.3 DUCTILE SHEAR FABRICS
17.4 FLANKING STRUCTURES FOR SHEAR SENSE
17.5 DISCUSSION
17.6 CONCLUSIONS
ACKNOWLEDGMENTS
REFERENCES
Index
End User License Agreement
List of Tables
Chapter 02
Table 2.1. Material properties and model parameters used in the finite element
modeling
Chapter 03
Table 3.1. Summary of data obtained from analysis of microphotographs
Chapter 06
Table 6.1 QSR strain rate measurements in the ASRR and KFZ strike-slip shear zones
Table 6.2. Titanium-in-quartz measurements
Chapter 07
Table 7.1. Mineral assemblages from rocks of the Scandinavian Caledonides in
northern Norway and Sweden
Table 7.2. Thin section descriptions of rocks from the Scandinavian Caledonides in
northern Norway and Sweden
Table 7.3. Titanium contents and calculated temperatures
Table 7.4. Representative electron probe analyses of garnet, plagioclase, and micas
Chapter 10
Table 10.1. Composition of feldspar and chlorite
Table 10.2. Representative composition of biotite, muscovite, rutile, and ilmenite
Table 10.3. Bulk Composition of major oxides (wt%) and trace elements and REE
(ppm) used for mass balance calculations
Chapter 11
Table 11.1. Electron probe data of plagioclase (a) and amphibole (b) used for P–T
estimation
Chapter 13
Table 13.1. Characterization of the Variscan episodes (D and later ones) recorded on
3
MLDSZ activity: timing of deformation, P–T and kinematic conditions, lithologies,
magmatism, and mineralizations
Chapter 14
Table 14.1. Synoptic table of phase relationships. Left column: summary of field and
petrographically observed mineral associations in each lithological type. Right column:
predicted low to high-T succession of equilibrium associations and stability
temperature range from pseudosection modeling, along the path shown by the arrow in
Fig. 14.4. In italic, main continuous reactions between established lithological types
and temperature range of development calculated through Fig. 14.5.
Table 14.2. Representative chemical analysis of plagioclases used for
geothermobarometry. The location of the samples along the profile is shown in Fig.
14.2
Table 14.3. Representative chemical analysis of biotites used for geothermobarometry.
The location of the samples along the profile is shown in Fig. 14.2
Table 14.4. Representative chemical analysis of garnets used for geothermobarometry.
The location of the samples along the profile is shown in Fig. 14.2.
Table 14.5. Results of the geothermobarometric study, corresponding to points plotted
in Fig. 14.2 to draw the geothermal curve along the cross-section. Details in the text
Chapter 15
Table 15.1. Summary of the geochronology data of the rocks within the strike–slip
ductile shear zones in Thailand
Table 15.2. Summary of the meso- and microstructures of the strike–slip ductile shear
zone in Thailand.
Chapter 16
Table 6.1. Chemical compositions of amphibole in the Nihonkoku mylonites
Table 16.2. K-Ar ages of the Nihonkoku Mylonites and related rocks
Chapter 17
Table 17.1. The quantitative parameters for the flanking folds of the area
List of Illustrations
Chapter 01
Fig. 1.1. Examples of strain evolution along the xy plane of the coordinate reference
frame for heterogeneous shear zones consisting of seven homogeneously deformed
layers and characterized by transtension in the active shear zone and synchronous pure
shear elsewhere. (a) Localizing shear zone. (b) Delocalizing shear zone.
Fig. 1.2. (a) Cartoon showing a homogeneous wrench zone. (b) Finite strain ellipsoid
geometry in case the x-axis lies in the xy plane of the coordinate reference frame. (c)
Finite strain ellipsoid geometry in case the x-axis is parallel to the z-axis of the
coordinate reference frame.
Fig. 1.3. (a) Outcrop view of the analyzed heterogeneous dextral wrench zone
deforming quartz vein. (b) Subdivision into homogeneously deformed layers. (c)
Geological sketch map of part of the Eastern Alps, showing site of the structural
analysis (star) (modified after Pennacchioni and Mancktelow 2007). (d) Normalized
Fry plot showing finite strain measured in the host rock.
Fig. 1.4. Γ− θ’ scatter diagram. The k –γ grid was constructed for a
2
transpressional/transtensional deformation (Δ = 0 and k = 1).
1
Fig. 1.5. Scatter diagrams of (a) finite effective shear strain Γ, (b) finite shear strain γ,
(c) finite strain ratio R , (d) finite elongation k , and (e) finite kinematic vorticity
XZ 2
number W versus finite angle θ’. Best-fit curves are also shown with associated
k
equation and coedfficient of determination R 2.
Fig. 1.6. Profiles of finite and incremental values of: (a) effective shear strain Γ, (b)
shear strain γ, (c) strain ratio R , (d) stretch k , and (e) kinematic vorticity number
XZ 2
W versus layer number n.
k
Fig. 1.7. (a) Γ− θ’ and (b) logarithmic Flinn diagrams showing incremental and finite
strain paths.
Chapter 02
Fig. 2.1. A generalized geological map of Singhbhum Craton, modified after Saha
(1994). (a) Position of the Singhbhum region. (b) Simplified geological map showing
the distribution of lithological units in Singhbhum craton (after Saha 1994).
Abbreviated units: CGGC: Chhotanagpur Granite Gneiss Complex; ASC: Archean
Singhbhum craton; NSMB: North Singhbhum mobile belt; SSZ: Singhbhum shear zone,
DV: Dalmaviolcanics. (c) Geological map of Purulia district (modified after map
published by Geological Survey of India, 2001), West Bengal within the eastern part of
CGGC. Black dashed box is the study area. Symbols in the legend indicate lithology
and structural fabrics and fold axis.
Fig. 2.2. Distortion patterns of passive markers in transpression zones for different S
r
(ratio of pure and simple shear rates) values. Markers were initially oriented at an
angle of θ with shear directions. The bottom row shows the initial orientation of
markers.
Fig. 2.3. Field examples of mesoscopic-scale, isolated ductile shear zones from the
CGGC (20 km west of Purulia town). Note that the foliation markers passing through
the shear zone at a high angle have been uniformly deflected sinistrally within the shear
zones (marked in white line). The aspect ratios of the shear zones were (a) 10.3, (b)
4.4 and (c) 11.7. Small scale dextral shear zones are also presented here showing
deflections of the foliation markers oriented t an angle of: 61° (d) and 34° (e) with the
shear direction respectively. The aspect ratios of the shear zones were measured to be
7.7 in (d) and 7.2 in (e). See text for detailed descriptions. Straight dashed lines mark
the shear zone boundary, while curved dashed lines indicate deflection of foliations.
Fig. 2.4. A schematic plan view of the experimental set-up used for analog experiments
of the transpressional kinematics in planar ductile shear zones under plane strain
conditions. α: inclination of shear zone normal to the bulk compression direction.
Black arrows indicate the direction of moving pistons.
Fig. 2.5. Development of ductile shear zones in analogue models with α = 45°. Bold
arrow indicates the direction of maximum compression. D : Shear zone aspect ratio.
f
The square grids were stamped in the initial models. Scale bar: 5 cm.
Fig. 2.6. Graphical presentations of the results obtained from analog experiments (left)
and FE simulations (right). (a) Finite bulk shortening across the shear zones (ε ), (b)
b
ratio of bulk pure and simple shear rates (S ) and (c) bulk vorticity (W ) versus shear
r k
zone aspect ratio (D ). Symbols (on the top right) indicate the inclination (in degrees)
f
of shear zone normal with the bulk compression direction (α).
Fig. 2.7. Progressive development of ductile shear zones in analog models with α = 30°
for different aspect ratio (D ). Bold arrow indicates the direction of maximum
f
compression. (a) D = 5; (b) D = 8, and (c) D = 10. Scale bar: 5 cm.
f f f
Fig. 2.8. Progressive development of ductile shear zones in analog models with α = 20°
for different aspect ratio (D ). Bold arrow indicates the direction of maximum
f
compression. (a) D = 5; (b) D = 7, and (c) D = 10. Scale bar: 5 cm.
f f f
Fig. 2.9. Initial FE models showing the boundary conditions for simulation of a ductile
shear zone at an angle α with the bulk compression direction (bold arrows). Both the
inclinations (α) and the length (l) to thickness (t) ratio of the shear zones were varied in
FE simulations. Regions 1 and 2 represent the shear zone and wall rock, respectively
with a non-slip boundary (white dotted lines) condition. U and U represent the
x y
amount of displacement along x and y directions respectively.