The origin of small cracks in igneous rocks
01 May 1970-International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts (Pergamon)-Vol. 7, Iss: 3, pp 307-314
TL;DR: The difference in compressional velocities at pressures of 1 atm and 10 kb, a sensitive indicator of microcrack porosity, is closely related to the presence of quartz in many igneous rock samples.
About: This article is published in International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts.The article was published on 1970-05-01. It has received 143 citations till now. The article focuses on the topics: Igneous rock & Quartz.
Citations
More filters
TL;DR: A review of recent work on microcracks in rock can be found in this paper, with a focus on the morphogenesis, kinematics, dynamics, population statistics and observational techniques.
812 citations
TL;DR: In this paper, the effective elastic compliance of rock that contains cracks is evaluated from energy considerations, as first proposed by Eshelby [1957], and the effective compliance is linearly elastic for small-amplitude elastic waves.
Abstract: The effective elastic compliance of rock that contains cracks is evaluated from energy considerations, as first proposed by Eshelby [1957]. The compliance of rock depends on the compliance of the solid matrix, the directional distribution of the cracks, an ‘inhomogeneity’ interaction tensor, and the shape distribution of cracks, which are assumed to be shaped like pennies. The effective compliance is linearly elastic for small-amplitude elastic waves. Anisotropic crack distribution causes elastic anisotropy, with associated acoustic birefringence. Nonhydrostatic stress causes stress-induced anisotropy, owing to anisotropic closure of cracks. Although velocities are uniquely determined from the distribution of cracks, the distribution cannot be determined uniquely from the velocities. The theoretical results compare favorably with measured compressional velocities and crack distribution in Salisbury granite and with measured stress-induced compressional and shear velocity anisotropy in Barre granite.
396 citations
TL;DR: In this paper, the authors developed a Fracture mechanics model to interpret thermal cracking in the Oak Hall limestone and found that the internal stresses due to thermal expansion anisotropy are relaxed by plastic flow in this relatively fine grained limestone.
Abstract: Samples of Westerly granite, Frederick diabase, and Oak Hall limestone were thermally cracked at room pressure to various peak temperatures. Scanning electon microscopy (SEM) was performed on ion-thinned samples. The thermally induced crack density is dependent upon the temperature, thermal expansion mismatch, thermal expansion anisotropy, initial crack porosity, and grain size. The mode of propagation is different for grain boundary and intragranular cracks. Crack densities in the granite were quantified using stereological techniques. The thermally induced crack surface area per unit volume apparently has a quadratic dependence on the temperature increase, a physical interpretation for which can be formulated on the basis of energetic balance. Fracture mechanics models are developed to interpret thermal cracking. The predictions concerning thermal crack initiation temperature and crack propagation and arrest behavior agree well with observations for the granite and the diabase. The model predicts significant thermal cracking for the Oak Hall limestone, which contradicts the SEM observation. A possible explanation for this discrepancy is that the internal stresses due to thermal expansion anisotropy are relaxed by plastic flow in this relatively fine grained limestone.
382 citations
TL;DR: In geologic settings, microfractures commonly form as Mode I (opening) fractures where the minimum principal stress exceeds the elastic tensile strength creating a narrow opening displacement; in isotropic rocks such fractures mark the plane perpendicular to the least compressive principal stress during fracture growth as discussed by the authors.
301 citations
Cites background from "The origin of small cracks in igneo..."
...…1979; Dula, 1981; Anders, 1982; Lespinasse and Pêcher, 1986; Kowallis et al., 1987; Laubach, 1988a,1989,1997; Fleischmann, 1990; Blenkinsop, 1990; Onasch, 1990; Wang and Sun, 1990; Anders and Wiltschko, 1994; Vermilye and Scholz, 1998; Boullier, 1999; Wilson et al., 2003; Gomez and Laubach,…...
[...]
...…paleoseismic events (Boullier and Robert, 1992), the character of fluids in deformational settings (Pêcheret al., 1985; Cathelineau et al., 1990; Boullier, 1999; Lespinasse, 1999), and, assuming inclusion size is a marker for microfracture opening displacement, finite strain (Onasch, 1990)....
[...]
...Some studies that used transmitted-light images of FIPs to determine the size and shape of fractures, on the premise that the inclusion distribution and widths are adequate proxies for fracture-opening displacement (Onasch, 1990), are not validated....
[...]
...…rocks (Tuttle, 1949), deformed sedimentary rocks (Engelder, 1974; Knipe and White, 1979; Dula, 1981; Anders, 1982; Mitra, 1987; Laubach, 1988a,b; Onasch, 1990; Anders and Wiltschko, 1994; Vermilye and Scholz, 1998; Wilson et al., 2003; I~nigo et al., 2012; Anders et al., 2013), and less…...
[...]
...Nevertheless, for microfractures with apertures in the range of 1 micron or less (Onasch, 1990), new approaches for discriminating healing and sealing processes should be sought (Onasch and Vennemann, 1995; Onasch et al., 2009)....
[...]
TL;DR: In this paper, a string of long, thin low aspect ratio cavities often follows grain boundaries in granites; aspect ratio of cavities ranges down to 10−3, while individual low aspect ratios rarely exceed about a tenth the grain size contrary to theoretical predictions.
238 citations
References
More filters
Book•
[...]
01 Jan 1934
TL;DR: The theory of the slipline field is used in this article to solve the problem of stable and non-stressed problems in plane strains in a plane-strain scenario.
Abstract: Chapter 1: Stresses and Strains Chapter 2: Foundations of Plasticity Chapter 3: Elasto-Plastic Bending and Torsion Chapter 4: Plastic Analysis of Beams and Frames Chapter 5: Further Solutions of Elasto-Plastic Problems Chapter 6: Theory of the Slipline Field Chapter 7: Steady Problems in Plane Strain Chapter 8: Non-Steady Problems in Plane Strain
20,724 citations
TL;DR: In this paper, a new experimental method which increased the sensitivity of detection by several orders of magnitude over that of previous studies was used, and the pattern of crack occurrence for a wide variety of rocks and at confining pressures up to 5 kb was found to be closely related to the stress-strain behavior.
Abstract: The cracking that occurs during the deformation of rock in compression was studied by detecting and analyzing the radiated elastic waves. A new experimental method which increased the sensitivity of detection by several orders of magnitude over that of previous studies was used. The pattern of crack occurrence for a wide variety of rocks and at confining pressures up to 5 kb was found to be closely related to the stress-strain behavior. Dilatancy in the region above half the fracture stress was found to be directly proportional to cracking. Microfracturing, i.e. cracking, of brittle rock was compared with the microfracturing observed in frictional sliding and in the deformation of ductile rock. Cataclastic deformation of marble was found to be similar to frictional sliding in this respect but distinctly different than brittle deformation. The marble was found to undergo a gradual transition from cataclastic to fully plastic flow as confining pressure was increased in tests up to 4 kb. A model of deformation of an inhomogeneous brittle material is introduced which predicts the observed microfracturing activity and inelastic stress-strain behavior of rock. According to this model, microfracturing events in the dilatant region below about 95% of the fracture stress can be considered randomly independent. At higher stresses, where a rapid acceleration of activity is observed, the events cannot be considered independent and are correlated with the formation of the fault.
601 citations
Book•
01 Jan 1967
TL;DR: In this article, Mecanique des roches and Dimensionnement were used for the Elasticite Reference Record created on 2004-09-07, modified on 2016-08-08.
Abstract: Keywords: Mecanique des roches ; Dimensionnement ; Elasticite Reference Record created on 2004-09-07, modified on 2016-08-08
520 citations
TL;DR: In this article, room temperature linear compressibilities of ten rocks in three directions were given to 9 kb. The large initial changes of compressibility with pressure of certain of the rocks are related quantitatively to porosity, grain size, and dimensional orientation.
Abstract: Room temperature linear compressibilities of ten rocks in three directions are given to 9 kb. Compression of the jacketed sample was measured by electric resistance strain gages. The large initial changes of compressibility with pressure of certain of the rocks are related quantitatively to porosity, grain size, and dimensional orientation. Above 3 kb the measured volume compressibility of all the rocks is within 4% of the average of the Voigt and Reuss averages of the mineral volume compressibilities.
304 citations