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Über dieses Buch

This book sets out the basic materials science needed for understanding the plastic deformation of rocks and minerals. Although at atmospheric pressure or at relatively low environmental pressures, these materials tend to be brittle, that is, to fracture with little prior plastic deformation when non-hydrostatically stressed, they can undergo substantial permanent strain when stressed under environmental conditions of high confining pressure and high temperature, such as occur geologically in the Earth’s crust and upper mantle. Thus the plastic deformation of rocks and minerals is of fundamental interest in structural geology and geodynamics. In mountain-building processes and during convective stirring in the Earth’s mantle, rocks can undergo very large amounts of plastic flow, accompanied by substantial changes in microstructure. These changes in microstructure remain in the rocks as evidence of the past deformation history. There are a number of types of physical processes whereby rock and minerals can undergo deformation under geological conditions. The physics of these processes is set out in this book.

Inhaltsverzeichnis

Frontmatter

Chapter 1. The Nature of Minerals and Rocks as Materials

Minerals show a wide range in physical and chemical properties, and rocks have the additional complexity of the textural and structural variety of polycrystalline materials. However, there are some generalizations that can be made. Thus, most minerals are electrically insulating, optically transparent in thin sections, and brittle under ordinary atmospheric conditions, and many are silicates in chemical constitution.

Mervyn S. Paterson

Chapter 2. Thermodynamics

Thermodynamics is the theory of the interaction of heat and work and of their relationship to the physical properties and processes in material systems, dealt with at the macroscopic scale. One of its principal uses is therefore to provide constraints on the constitutive equations that describe the state of systems or the processes occurring in them. The foundation of thermodynamics consists of a minimal number of postulates or empirical laws drawn from experience. However, it has also been proposed that it can be regarded as being rooted in some universal and fundamental concepts of symmetry or invariance under transformation that apply to physical laws. The scope of thermodynamics has traditionally been limited mainly to systems in equilibrium but has more recently been extended to deal also with non-equilibrium situations. We shall give here a brief summary of the principal results of these two branches of the theory.

Mervyn S. Paterson

Chapter 3. Rate Processes

We now proceed to some general considerations of processes in material systems. A rate process in any system may be defined as a course of change in the system as a function of time. Very broadly, three types of rate processes may usefully be distinguished; reactions, transport processes, and deformations.

Mervyn S. Paterson

Chapter 4. Mechanical Fundamentals

There are some very broad distinctions that can usefully be made in classifying types of mechanical behavior and the approaches to their study. The first of these distinctions is between

brittle

and

ductile

behavior. We can define brittleness as the liability to gross fracturing without substantial permanent change of shape in response to loading beyond the elastic range. Conversely, ductility is the capacity for substantial permanent change of shape without gross fracturing. In this context, “gross” means on the scale of the whole body or region under consideration and the use of the terms brittle and ductile is only meaningful with proper reference to scale. For the study of brittle behavior, see Jaeger (1969), Paterson and Wong (2005), and Jaeger et al. (2007). In this chapter, we are mainly concerned with ductile behavior or plastic deformation.

Mervyn S. Paterson

Chapter 5. Deformation Mechanisms: Atomic Transfer Flow

In this category of deformation mechanisms we are concerned with processes in which individual atoms or small groups of associated atoms are removed from certain interfaces or discontinuities within the structure of the body (sources) and are transferred to other interfaces or discontinuities (sinks) in such a way that the overall shape of the body is changed, that is, the body undergoes macroscopic strain. The sources and sinks may be dislocation cores, planar crystal defects, grain boundaries or free internal or external surfaces, and the transfer may take place by a variety of mechanisms, including solid state diffusion (intra- or intergranular) and transfer via a fluid phase (in case of a porous or partially melted body). The overall kinetics may be controlled by the kinetics of the transfer process or by the kinetics of the detachment and re-attachment processes. We have used the term “atomic transfer flow” in introducing this class of mechanisms in order to emphasize that the transfer occurs more or less atom by atom rather than by the movement of relatively large blocks of atoms; however, the term “diffusion creep” is commonly used in the same sense, especially when it is wished to emphasize diffusion as the transfer process or as being rate controlling.

Mervyn S. Paterson

Chapter 6. Deformation Mechanisms: Crystal Plasticity

The deformation mechanisms of the greatest importance in the intra granular plastic deformation of crystalline materials are slip and twinning. In these mechanisms, the strain or change of shape is achieved by the relative movement of blocks of atoms rather than by the more or less independent movement of individual atoms that characterizes the atomic transfer mechanisms considered in the previous chapter

Mervyn S. Paterson

Chapter 7. Deformation Mechanisms: Granular Flow

In the previous two chapters we have considered deformation processes that involve the relative movement of individual atoms or molecules (Chap. 5) or of different parts of a given crystal or crystalline grain (Chap. 6). In this third chapter on deformation mechanisms we shall consider flow by the relative movement of more or less macroscopic entities, which may be whole grains or groups of grains such as particles of fractured rock. These entities can perhaps best be referred to generically as

granules

and their assemblage be said to constitute a

granular body

. The flow by relative movement of granules can then be called

granular flow

.

Mervyn S. Paterson

Backmatter

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