Chapter 7 Flashcards
Grain boundary sliding is influenced by friction, and the mechanism is therefore called
frictional sliding
The grains translate and rotate to accommodate frictional grain boundary slip, and the whole process is called
granular flow
are fractures restricted to single grains.
Intragranular fractures
are fractures that extend across a few grains.
Intergranular fractures
The fracture and crushing of grains, coupled with frictional sliding along grain contacts and grain rotation
cataclasis
More moderate cataclastic deformation can occur in somewhat wider brittle or cataclastic shear zones. In this case the fragments resulting from grain crushing flow during shearing
cataclastic flow.
Strong grain crushing without evidence of shear offset has also been observed and is called
pulverization
any planar or subplanar discontinuity that is very narrow in one dimension compared to the other two and forms as a result of external (e.g. tectonic) or internal (thermal or residual) stress.
fracture
Fractures can be separated into:
- shear fractures (slip surfaces)
- opening or extension fractures (joints, fissures and veins)
are very narrow zones, often thought of as surfaces, associated with discontinuities in displacement and mechanical properties (strength or stiffness).
Fractures
is a fracture along which the relative movement is parallel to the fracture
is used for fractures with small (mm- to dm-scale) displacements
shear fracture
is more commonly restricted to discontinuities with larger offset.
fault
used for fractures with fracture-parallel movements regardless of the amount of displacement and is consistent with the traditional use of the term fault.
slip surface
are fractures that show extension perpendicular to the walls.
Extension Fractures
have little or no macroscopically detectable displacement, but close examination reveals that most joints have a minute extensional displacement across the joint surfaces, and therefore they are classified as true extension fractures.
Joints
When filled with air or fluid we use the term
fissure
Mineral-filled extension fractures are called
veins
while magma-filled fractures are classified
dikes
have contractional displacements across them and are filled with immobile residue from the host rock.
Contractional planar features
are compactional structures characterized by very irregular, rather than planar, surfaces.
Stylolites
as they nicely define one of three endmembers in a complete kinematic fracture framework together with shear and extension fractures.
Contraction fractures
can be used to test the uniaxial compressive or tensile strength of rocks.
Uniaxial rigs
is used to explore the effect of large shear strain under vertical compression of up to about 25 MPa.
ringshear apparatus
where rock cylinders are loaded in the axial direction while the sample is confined in fluid that can be pumped up to a certain confining pressure.
Triaxial tests