Fault-related Rocks

Fault-related Rocks: A Photographic Atlas

Arthur W. Snoke
Jan Tullis
Victoria R. Todd
Copyright Date: 1998
Pages: 634
https://www.jstor.org/stable/j.ctt7zvg0k
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    Fault-related Rocks
    Book Description:

    This is a richly illustrated reference book that provides a unique, comprehensive, and up-to-date survey of the rocks and structures of fault and shear zones. These zones are fundamental geologic structures in the Earth's crust. Their rigorous analysis is crucial to understanding the kinematics and dynamics of the continental and oceanic crust, the nature of earthquakes, and the formation of gold and hydrocarbon deposits. To document the variety of fault-related rocks, the book presents more than six hundred photographs of structures ranging in scale from outcrop to submicroscopic. These are accompanied by detailed explanations, often including geologic maps and cross sections, contributed by over 125 geoscientists from around the world.

    The book opens with an extensive introduction by Arthur W. Snoke and Jan Tullis that is itself a major contribution to the field. Fault-related rocks and their origins have long been controversial and subject to inconsistent terminology. Snoke and Tullis address these problems by presenting the currently accepted ideas in the field, focusing on deformation mechanisms and conceptual models for fault and shear zones. They define common terminology and classifications and present a list of important questions for future research. In the main, photographic part of the book, the editors divide the contributions into three broad categories, covering brittle behavior, semi-brittle behavior, and ductile behavior. Under these headings, there are contributions on dozens of subtopics with photographs from localities around the world, including several "type" areas.

    The book is an unrivaled source of information about fault-related rocks and will be important reading for a broad range of earth scientists, including structural geologists, petrologists, geophysicists, and environmental specialists.

    Originally published in 1998.

    ThePrinceton Legacy Libraryuses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These paperback editions preserve the original texts of these important books while presenting them in durable paperback editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.

    eISBN: 978-1-4008-6493-5
    Subjects: General Science

Table of Contents

  1. Front Matter
    (pp. i-iv)
  2. ERRATA
    (pp. v-vi)
  3. Preface
    (pp. vii-viii)
    Arthur W. Snoke, Jan Tullis and Victoria R. Todd
  4. Contributors’ addresses
    (pp. ix-2)
  5. AN OVERVIEW OF FAULT ROCKS
    (pp. 3-18)
    Arthur W. Snoke and Jan Tullis

    The characteristics of faults and shear zones are strikingly variable. One goal of this Atlas is to provide a visual overview of the characteristics of the rocks associated with faults and shear zones. Such rocks are broadly calledfault rocks(Sibson, 1977) and range from brittle, incohesive breccia or gouge at the highest structural levels in the Earth’s crust to high-temperature, crystal-plastic mylonites in the deep crust or upper mantle.

    In this overview, we include (1) a brief discussion of fault-rock nomenclature and classification. (2) a summary of the important grain-scale deformation mechanisms operative within fault and shear zones, (3)...

  6. BRITTLE BEHAVIOR Geometrical characteristics and microstructures
    (pp. 19-50)

    Common abbreviations used in regard to the plates in this section include PPL = plane polarized light, NX = crossed nicols, SEM = scanning electron microscope, and TEM = transmission electron microscope.

    This set of plates illustrates some mesoscopic to microscopic characteristics of brittle fault zones in the upper crust. Many of the examples are in granitic rocks, although characteristics of brittle deformation in other rock types are also illustrated in several of the plates, including mafic rocks of the oceanic crust. Fractures at all scales from the single mineral grain to mesoscopic fracture arrays are the focus of many...

  7. BRITTLE BEHAVIOR Cataclasis and gouge development
    (pp. 51-74)

    Common abbreviations used in regard to the plates in this section include PPL = plane polarized light and NX = crossed nicols.

    Although the basic focus of this set of nine plates overlaps in part with the previous examples from brittle fault zones, they emphasize the processes and nature of gouge and cataclasite from natural and experimental faults. The dominant process in all cases is fracturing on all scales and frictional sliding of the fragments. The ultimate product is extremely fine grained, incohesive fault gouge, or if cementation occurs by precipitation from fluids or other processes, cohesive cataclasite. Many of...

  8. BRITTLE BEHAVIOR Pseudotachylyte
    (pp. 75-128)

    Common abbreviations used in regard to the plates in this section include PPL = plane polarized light, NX = crossed nicols, SEM = scanning electron microscope, and TEM = transmission electron microscope.

    Pseudotachylyte is a fault rock of great interest, because frictional melting is the most certain microstructural indicator of seismicity on ancient faults. This set of plates illustrates features of pseudotachylytes on scales from outcrop to thin section to SEM and TEM. The original type locality of pseudotachylyte in the Vredefort Structure, South Africa, is illustrated. Although this feature is now known to be an impact structure, the pseudotachylyte...

  9. BRITTLE BEHAVIOR Fluid-related features
    (pp. 129-140)

    Common abbreviations used in regard to the plates in this section include PPL = plane polarized light, NX = crossed nicols, and SEM = scanning electron microscope.

    This set of plates, consisting of observations based on both naturally and experimentally deformed samples, illustrates the important role of fluids in faulting. It is now recognized that veins, precipitated from fluids, are a common constituent of many fault zones, indicating that faults tend to focus the upward migration of metamorphic and other fluids. Two of the contributions illustrate portions of fault-related vein systems, and they present clear evidence for cycles of rupture...

  10. SEMI-BRITTLE BEHAVIOR Geometrical characteristics and microstructures
    (pp. 141-202)

    Common abbreviations used in this section include PPL = plane polarized light, NX = crossed nicols, PNX = partial crossed nicols, and TEM = transmission electron microscope.

    The contributions in this section illustrate the complexity of deformation in fault and shear zones at depths spanning the brittle-to-plastic and seismic-aseismic transitions. Most of the contributions illustrate features from naturally deformed quartzo-feldspathic rocks, on outcrop and thin-section scales; other contributions illustrate features from naturally deformed gabbroic rocks, and experimentally deformed halite and feldspar rocks. In all cases, the deformation has occurred partly by crystal-plasticity and partly by fracturing. In some examples, deformation...

  11. SEMI-BRITTLE BEHAVIOR Fluid-related features
    (pp. 203-224)

    Common abbreviations used in regard to the plates in this section include PPL = plane polarized light, NX = crossed nicols, and SEM = scanning electron microscope.

    This set of plates illustrates a further complexity of rocks deformed at depths spanning the brittle-to-plastic and seismic-aseismic transitions, namely, the influence of fluids. These plates document that even though the dominant deformation in low-grade shear zones may be crystal-plasticity, the permeability in these shear zones is higher than in the undeformed wall rocks. The evidence for the influence of fluids ranges from outcrop features to thin-section and SEM-scale microstructures, as well as...

  12. DUCTILE BEHAVIOR Strain partitioning and other geometric characteristics
    (pp. 225-254)

    Common abbreviations used in regard to the plates in this section include NX = crossed nicols and TEM = transmission electron microscope.

    This set of plates illustrates the partitioning of strain on mesoscopic and microscopic scales, from rocks deformed at greenschist through granulite facies, and from rocks of the oceanic as well as the continental crust. Strain partitioning results from rheological heterogeneities; the plates in this section primarily illustrate strain partitioning resulting from compositional heterogeneities. Some of the microstructures that characterize Lapworth’s original mylonite are due to grainscale strain partitioning in a granitic rock, deformed at physical conditions where feldspar...

  13. DUCTILE BEHAVIOR Microstructures
    (pp. 255-290)

    Common abbreviations used in regard to the plates in this section include: PPL = plane polarized light, NX = crossed nicols, PNX = partial crossed nicols, and SEM = scanning electron microscope.

    This set of plates illustrates some of the grain-scale microstructures characteristic of highly strained rocks or mylonites. Most examples are from quartz or feldspar, although there are several illustrations of other phases, including micas, garnet, calcite, and analog materials. Many of these plates illustrate aspects of dynamic recrystallization, which is one of the hallmarks of a ductilely deformed mylonite, and a process that is very important for reducing...

  14. DUCTILE BEHAVIOR Foliation development
    (pp. 291-304)

    Common abbreviations used in regard to the plates in this section include PPL = plane polarized light and NX = crossed nicols.

    In addition to grain-size reduction, another characteristic of mylonites in Lapworth’s original definition was fluxion structure or foliation. This set of plates illustrates the development of foliation in mylonites by several processes, including the high-strain attentuation of original compositional layers; the flattening or shearing of originally equant grains or regions; and the synkinematic reaction to micaceous phases. The plates illustrate that foliation may be fairly uniform and planar, but once formed it constitutes a heterogeneity and may become...

  15. DUCTILE BEHAVIOR Composite foliations in mylonites
    (pp. 305-332)

    Common abbreviations used in regard to the plates in this section include PPL = plane polarized light and NX = crossed nicols.

    An important microstructural feature of many mylonitic rocks is composite foliations. In a widely cited paper on mylonitic granitic rocks, Berthé and others (1979a) introduced the terminology S (forschistositéor plane of flattening) and C (forcisaillementor plane of shearing). The classic S-C fabric, as originally described by Berthé and others (1979a), was interpreted as a shear-strain-sensitive fabric in that the angle between S and C became smaller with increased strain. One contribution within this set...

  16. DUCTILE BEHAVIOR Porphyroclasts in mylonites
    (pp. 333-358)

    Common abbreviations used in regard to the plates in this section include PL = plane light. PPL = plane polarized light, and NX = crossed nicols.

    This set of plates illustrates an important microstructural indicator of shear sense in mylonites, namely asymmetric porphyroclasts. A great deal of research in the past fifteen years has been devoted to experimental and theoretical investigations of porphyroclast systems, determining the effect of rheologic contrast, initial shapes, and rate of shearing versus rate of dynamic recrystallization. These plates illustrate natural porphyroclasts of feldspar, mica, amphibole, as well as porphyroclasts in experimental systems where the variables...

  17. DUCTILE BEHAVIOR Folds in mylonitic zones
    (pp. 359-368)

    Abbreviation used in regard to the plates include PPL = plane polarized light.

    Progressive general shear tends to amplify initial heterogeneities and to produce folds on various scales. After high strain, the limbs will be parallel and the hinge line may be curvilinear, as in a sheath fold. Folds in shear zones are commonly difficult to recognize; but if hinges can be identified and a consistent vergence established, the folds can serve as sense-of-shear indicators, especially if the folding and high strain were synchronous. However, folds in mylonitic shear zones can be confusing for kinematic analysis, because they may represent...

  18. DUCTILE BEHAVIOR Evidence of coaxial deformational histories
    (pp. 369-380)

    Common abbreviations used in regard to the plates in this section include PL = plane light, NX = crossed nicols, and TEM = transmission electron microscope.

    Most mylonites are thought to result from simple or general shear, and the abundance of asymmetric structures such as composite foliations, rotated porphyroclasts, and asymmetric crystallographic preferred orientations is consistent with that interpretation. However, highly localized strain can sometimes result from coaxial deformation. For example, mylonitic textures have been produced in high-strain axial compression experiments. The plates in this section illustrate some examples of natural mylonites interpreted to have resulted from coaxial deformation. The...

  19. DUCTILE BEHAVIOR Metamorphic grade variations Low- and medium-grade shear zones
    (pp. 381-416)

    Common abbreviations used in regard to the plates in this section include PPL = plane polarized light, NX = crossed nicols, PNX = partial crossed nocols, SEM = scanning electron microscope, and TEM = transmission electron microscope.

    This set of plates includes a contribution from the type locality of mylonite at Ben Arnaboll Hill within the Moine thrust zone at Eriboll, northwest Scotland. The rocks illustrated from this classic locality, as well as those illustrated in several other plates, are quartzo-feldspathic. This group of plates also illustrates low-and medium-grade mylonites developed in other rock types, including mafic and ultramafic rocks...

  20. DUCTILE BEHAVIOR Metamorphic grade variations High-grade shear zones
    (pp. 417-448)

    Common abbreviations used in regard to the plates in this section include PPL = plane polarized light, NX = crossed nicols, SEM = scanning electron microscope, and TEM = transmission electron microscope.

    This set of plates illustrates features developed in shear zones formed at upper-amphibolite to granulite fades, and during the transition from granulite to eclogite facies. High temperature promotes crystal plasticity in plagioclase, amphibole, and pyroxene which are strong at low to moderate grades. However, high-temperature microstructures are only well preserved if the rocks remain dry during exhumation. Several plates illustrate the interplay of deformation and metamorphism; others emphasize...

  21. DUCTILE BEHAVIOR Metamorphic grade variations Annealed fault-rock textures
    (pp. 449-464)

    Common abbreviations used in regard to the plates in this section include: PPL = plane polarized light, NX = crossed nicols, and TEM = transmission electron microscope.

    High-temperature mylonites tend to be completely recrystallized to an aggregate of polygonal grains that appear internally unstrained. Such rocks may appear to have been statically annealed following deformation, but at high temperatures the rates of dislocation climb and dynamic recrystallization keep pace with the strain rate, and dynamic recrystallization can produce microstructures that are almost almost identical to those of annealing recrystallization. This set of plates includes the results of two experimental studies...

  22. DUCTILE BEHAVIOR Fluid-related features
    (pp. 465-476)

    Common abbreviations used in regard to the plates in this section include PPL = plane polarized light, NX = crossed nicols, SEM = scanning electron microscope, and TEM = transmission electron microscope.

    It is known from experimental studies that aqueous fluids strongly affect all deformation mechanisms; this conclusion is supported by the microstructures of many naturally deformed rocks, and some of these are illustrated in this set of plates. One plate illustrates a possible example of stress corrosion, the process whereby fluids enhance the rate of stable crack propagation. Fluids also enhance the rates of pressure solution, and two plates...

  23. DUCTILE BEHAVIOR Microstructural development of mylonitic rocks of specific composition Quartzose rocks
    (pp. 477-502)

    Common abbreviations used in regard to the plates in this section include PPL = plane polarized light, NX = crossed nicols, SEM = scanning electron microscope, and TEM = transmission electron microscope.

    Quartz is one of the most ductile as well as one of the most studied crustal silicates. It undergoes significant crystal-plasticity under greenschist-facies conditions and develops strong crystallographic preferred orientations (CPOs) that are relatively easy to measure. These plates illustrate microstructures developed in naturally deformed quartzites from lower greenschist through upper amphibolite facies, including some from classic Moine thrust localities in the Scottish Highlands, as well as almost...

  24. DUCTILE BEHAVIOR Microstructural development of mylonitic rocks of specific composition Feldspathic rocks
    (pp. 503-530)

    Common abbreviations used in regard to the plates in this section include PPL = plane polarized light, NX = crossed nicols, SEM = scanning electron microscope, and TEM = transmission electron microscope.

    This set of plates illustrates the microstructures developed in feldspars from naturally sheared anorthosites. granites, tonalites, and monzogranites, as well as experimentally deformed albite aggregates. Several of these contributions indicate that feldspars show two of the same dislocation creep regimes identified in quartz, including a lower-temperature regime characterized by grain-boundary migration recrystallization and a higher-temperature regime characterized by subgrain rotation recrystallization. However, the temperatures required for these regimes...

  25. DUCTILE BEHAVIOR Microstructural development of mylonitic rocks of specific composition Carbonate rocks
    (pp. 531-550)

    Common abbreviations used in regard to the plates in this section include PPL = plane polarized light, NX = crossed nicols, SEM = scanning electron microscope, and TEM = transmission electron microscope.

    This set of plates illustrates the microstructures and crystallographic preferred orientations (CPOs) developed in experimentally and naturally deformed calcite aggregates, and one naturally deformed dolomite aggregate. Several of the contributions illustrate the important results that have come from experimental studies; for example, identification of different mechanisms of dynamic recrystallization and calibration of a recrystallized grain-size paleopiezometer. In addition, they illustrate the experimentally documented change in microstructures and CPOs...

  26. DUCTILE BEHAVIOR Microstructural development of mylonitic rocks of specific composition Evaporites
    (pp. 551-562)

    Common abbreviations used in regard to the plates in this section include NX = crossed nicols and TEM = transmission electron microscope.

    This set of plates illustrates the deformation of evaporites. which are even weaker than carbonates. There have been many studies of halite deformation, due in part to its possible use for nuclear waste repositories. The plates here illustrate mylonitic halite from salt domes and glaciers, in which the halite has undergone a combination of dislocation and solution transfer creep. These halite mylonites, especially when they contain small amounts of harder phases, have microstructures ranging from high-grade “gneisses” to...

  27. DUCTILE BEHAVIOR Microstructural development of mylonitic rocks of specific composition Mafic rocks
    (pp. 563-576)

    Common abbreviations used in regard to the plates in this section include PPL = plane polarized light and NX = crossed nicols.

    This set of plates illustrates deformation microstructures characteristic of the oceanic crust. These rocks are more difficult to sample, and our knowledge is more limited. Two contributions illustrate deformed gabbros from ophiolites, and two others illustrate deformed gabbros from dredged and cored oceanic ridge environments. These plates show that at higher temperature (granulite-facies) pyroxene and plagioclase undergo slip and dynamic recrystallization, but with decreasing temperature (amphibolite-facies) deformation becomes more localized and strain is partitioned almost entirely into the...

  28. DUCTILE BEHAVIOR Microstructural development of mylonitic rocks of specific composition Ultramafic rocks
    (pp. 577-594)

    Common abbreviations used in regard to the plates in this section include PPL = plane polarized light and NX = crossed nicols.

    This set of plates illustrates outcrop and thin-section scale structures developed in localized high-strain zones within upper mantle peridotites, involving chiefly olivine, clinopyroxene, and orthopyroxene. Most of the examples come from ophiolites, and one comes from a kimberlite xenolith. Most of these rocks record deformation at extremely high temperatures, characteristic of asthenospheric or lithospheric mantle, although one illustrates the structures developed at lower temperatures where serpentine was stable. The microstructures in these rocks demonstrate that the order of...

  29. References cited
    (pp. 595-614)
  30. Index
    (pp. 615-617)