Voigt and Reuss prediction of anisotropic elasticity of dunite

Crosson, Robert S.; Jia-jun, Lin

doi:10.1029/jb076i002p00570

Cited by 168 publications

(59 citation statements)

References 19 publications

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“…Bunge 1982;Ben Ismail & Mainprice 1998). Due to stress/strain compatibility assumptions, three different averaging schemes are possible (Crosson & Lin 1971). The constant strain or Voigt (V) average (Voigt 1928) and constant stress or Reuss (R) average (Reuss 1929) provide upper and lower bounds.…”

Section: Methodsmentioning

confidence: 99%

From crystal to crustal: petrofabric-derived seismic modelling of regional tectonics

Lloyd

Halliday

Butler

et al. 2011

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Abstract:The Nanga Parbat Massif (NPM), Pakistan Himalaya, is an exhumed tract of Indian continental crust and represents an area of active crustal thickening and exhumation. While the most effective way to study the NPM at depth is through seismic imaging, interpretation depends upon knowledge of the seismic properties of the rocks. Gneissic, 'mylonitic' and cataclastic rocks emplaced at the surface were sampled as proxies for lithologies and fabrics currently accommodating deformation at depth. Mineral crystallographic preferred orientations (CPO) were measured via scanning electron microscope (SEM)/electron backscatter diffraction (EBSD), from which three-dimensional (3D) elastic constants, seismic velocities and anisotropies were predicted. Micas make the main contribution to sample anisotropy. Background gneisses have highest anisotropy (up to 10.4% shear-wave splitting, AVs) compared with samples exhibiting localized deformations (e.g. 'mylonite', 4.7% AVs; cataclasite, 1% AVs). Thus, mylonitic shear zones may be characterized by regions of low anisotropy compared to their wall rocks. CPOderived sample elastic constants were used to construct seismic models of NPM tectonics, through which P-, S-and converted waves were ray-traced. Foliation orientation has dramatic effects on these waves. The seismic models suggest dominantly pure-shear tectonics for the NPM involving horizontal compression and vertical stretching, modified by localized ductile and brittle ('simple') shear deformations.

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Section: Methodsmentioning

confidence: 99%

From crystal to crustal: petrofabric-derived seismic modelling of regional tectonics

Lloyd

Halliday

Butler

et al. 2011

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“…In ultramafic and metamorphic rocks, numerous authors have shown that acoustic anisotropy can be explained by preferred orientation of anisotropic minerals (Crosson and Lin, 1971;Baker and Carter, 1972;Brocher and Christensen, 1990). Calcite is a highly anisotropic mineral in which the P-wave velocity parallel to the oaxis is 5.6 km/s whereas P-wave velocity perpendicular to the c-axis is 7.4 km/s (Dandekar, 1968).…”

Section: Mineral Orientationmentioning

confidence: 99%

Velocity Anisotropy in Calcareous Sediments from Leg 130, Ontong Java Plateau

Bassinot¹,

Marsters²,

Mayer³

et al. 1993

Proceedings of the Ocean Drilling Program

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During Leg 130, an intensive program of P-wave velocity measurements was conducted on calcareous sediments of varying induration (ranging from ooze to limestone) that cover the Ontong Java Plateau (west equatorial Pacific). The high quantity and quality of shipboard acoustical property measurements seemed to be particularly appropriate for gaining a better understanding of acoustic anisotropy in calcareous sediments. Major results can be summarized as follows:1. In calcareous oozes, acoustic anisotropy exists even at shallow depths of burial. Values are low, ranging from -0.5% to 3.5% and averaging 1.2%. Anisotropy profiles are affected by coring disturbances, but they still roughly correlate between holes cored at a same site. There is no general increase of anisotropy with depth of burial in ooze sections. These observations imply that most of the anisotropy measured in oozes is controlled by original changes in sediment composition rather than by reorientation of anisotropic minerals or flattening of pores during burial. Given the data available, bedding lamination seems to be the most satisfactory explanation for acoustic anisotropy in calcareous oozes of Ontong Java Plateau. However, bioturbation affects the entire ooze sections cored and much of the original depositional features may have been removed. Further analysis such as scanning-electron-microscope (SEM) observations of epoxy impregnated ooze samples are necessary to test the "bedding lamination" hypothesis.2. Ooze to chalk transition is marked by a tremendous change in the anisotropy profiles. In chalk sections the anisotropy values are higher (reaching 20%) than in ooze sections. Most of the anisotropies are negative (horizontal P-wave velocities lower than vertical velocities), whereas positive values are expected. Weakly cemented chalk samples are affected by cracking when compressed between the Hamilton Frame transducers for P-wave measurement. Cracks occur along bedding planes during horizontal P-wave velocity measurements, thus leading to anomalously low horizontal P-wave velocities and negative anisotropies.

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“…Using an interactive program (Mainprice, 1990), the procedure for the calcula tion of seismic phase velocities uses the Christof fel equation and has been described in detail by Crosson and Lin (1971) and Peselnick et al (1974). This explains the only monoclinic symmetry of the diagrams.…”

Section: Calculations Of Sws From Petrofabric Datamentioning

confidence: 99%