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Microporous and Mesoporous Solids
Published in Elaine A. Moore, Lesley E. Smart, Solid State Chemistry, 2020
Elaine A. Moore, Lesley E. Smart
SiO44− units share two corners to form infinite chains (see Figure 7.3c). The repeat unit is SiO32−. Minerals with this structure are called pyroxenes, which together with olivine, form the primary constituents of the Earth’s upper mantle, for example, diopside (CaMg(SiO3)2) and enstatite (Mg2(SiO3)2). The silicate chains lie parallel to one another and are linked together by the cations that lie between them.
Determination of rock stress by anelastic strain recovery measurement of an oriented core in the Nittsu region of Japan
Published in Katsuhiko Sugawara, Yuzo Obara, Akira Sato, Rock Stress, 2020
W. Lin, T. Hirono, T. Nakamura, K. Yamamoto, K. Matsuki, T. Imamura, Y. Oikawa, M. Takahashi, M. Kwasniewski
A deep well named METI (Ministry of Economy, Trade and Industry) Niitsu well was drilled in Niigata Heiya, Japan. The maximum depth of the well reached 5000 m MD with an inclination of about 20º, and the true vertical depth at the bottom of the well was 4702 m. The outline of the geological structure of the region has been given by Imamura (2003). At this site, the anelastic strain of oriented cores obtained from four depths in the range from about 2400m MD to 4500m MD was measured in six independent directions after the release of the corresponding in-situ stresses. In this paper, the anelastic strain measurement results for a core taken from the deepest location as well as the predicted orientations and magnitudes of three-dimensional principal in-situ stresses will be reported. The core of about 10cm in diameter was taken from a depth of 4544 m MD; the rock material was andesite. Major component minerals were feldspar, quartz, enstatite or hypersthene, and hematite. Dry bulk density of the rock was 2.72 g/cm3, and porosity determined using water saturation method was 0.71%. Compressional wave velocities measured in three directions on a cubic specimen obtained from the depth of 4542m MD, being macroscopically the same as the core used for ASR measurement, ranged from 4.4 km/s to 4.8 km/s, and shear wave velocities were 2.8–3.0 km/s. Although a slight difference between the velocities in different directions was revealed, distinct anisotropy of the texture of the cores could not be macroscopically observed. Poisson’s ratio calculated from compressional and shear wave velocities was equal to 0.20, approximately.
Composition and Miocene deformation of the lithospheric mantle adjacent to the Marlborough Fault System in North Canterbury
Published in New Zealand Journal of Geology and Geophysics, 2023
Sophie J. Bonnington, James M. Scott, Marshall C. Palmer, Nadine P. Cooper, Malcolm R. Reid, Claudine H. Stirling
Olivine-websterite xenoliths display olivine Mg# ranging from 83.0 to 87.1 (Figure 5A). One exception is LLR-6, with an extremely low olivine Mg# of 74.4. All the olivine-websterite Mg# sit below primitive upper mantle values (Figure 5A). Orthopyroxene within the pyroxenite samples is typically magnesium-rich enstatite with an average end-member composition of Wo2En84Fs14, similar to the peridotites. Orthopyroxene comprises 39% to 93% of the total modal abundance of the pyroxenite samples. Clinopyroxenes have an average end-member composition of Wo43En49Fs9 and are diopside (Data Supplementary). These are very similar to the peridotite clinopyroxene compositions.