Frictional sliding and the fabric developed in experimental shear zones /
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| Other Authors: | , , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1989.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy |
| Abstract: | The changes of fabric and deformation mechanisms in experimental shear zone are studied with calcite at confining pressure from 10MPa to 300MPa, 5μ per second slip rate, and temperature from 20° to 1000°C. By using stain markers, such as dicolour calcite gouge or crystallographic planes, the evolutionary processes of fabric developed in a triaxial experimental shear zone are quantitatively and qualitatively documented. In the brittle-cataclastic flow regime, three fabric developing stages are recognized. (1) Compaction-uniform shear. Loose gouge is compacted, layer-parallel sheared and fractured, limited shear displacement developed along R₁ fractures. (2) Slip-surface formation. The deformation is concentrated to discrete shear zones and R₁ fractures elongate and rotate to a lower angle to coalesce and to form Y-slip surfaces. (3) Steady-state friction. Sliding is concentrated along the rock-gouge interface or along a Y surface, located very close to the rock-gouge interface. A deformation mechanism field map is constructed that combines mechanisms and fabric development processes. A shear zone can be described mechanically as three part layers connected in series across frictional surfaces. The weak member, either the layer or the contact surface, dominates the deformation. Frictional sliding accommodates most of the strain until recovery process involving recrystallization dominates. With increasing temperature, stable sliding to stick-slip to stable shearing transition is observed. The effects of increasing temperature on the change of slip mode are similar to the effects of decreasing slip rate. The frictional strength-temperature relationship can be described by [Equation in PDF] Frictional sliding is divided into two categories: flow-type and adhesion-type. Flow-type friction is characterized by sliding along a deformation zone; deformation and plowing of asperities offer the dominant resistance. Surfaces and grains are fractured, sheared, rotated, and comminuted. Frictional strength increases with increasing slip rate. Adhesion-type friction is characterized by sliding along a flat single surface where adhesion is the main resistance. Minor deformation is found during frictional sliding, negative velocity dependency and unstable behavior are conspicuous features. At low confining pressure, fine-grained gouge or smooth surface, low slip rate, and moderate temperature promote instability. Stick-slip is stabilized at high confining pressure or high temperature, under which negative strain rate dependency vanishes. |
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| Item Description: | Typescript (photocopy). Vita. "Major subject: Geophysics." |
| Physical Description: | xiii, 167 leaves : illustrations ; 29 cm |
| Bibliography: | Includes bibliographical references. |