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Metamorphic Rocks
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Figure 10.27 shows a diagram equivalent to Figure 10.25, but for mafic igneous rocks instead of for pelites. Just like with pelitic rocks, the presence or absence of specific minerals is a good indicator of metamorphic grade. Table 10.4 gives the compositions of these key minerals. The minerals in mafic rocks have high-temperature (igneous) origins. Consequently, during low-grade metamorphism, new minerals often form by retrograde reactions, which is not generally the case for pelitic rocks. One complication with mafic rocks is that, in contrast with minerals in pelitic rocks, some of the minerals in mafic rocks have quite varying compositions—and thus variable stability ranges. So, the sizes of the red boxes and their order in Figure 10.27 are approximate.
Application of teleseismic receiver function in investigation of crustal thickness and Poisson's ratio
Published in Rajib Biswas, Recent Developments in Using Seismic Waves as a Probe for Subsurface Investigations, 2023
Monika Wadhawan, Devajit Hazarika, Sowrav Saikia
The average Poisson's ratio of the crust provides an idea of underlying rock types and mineral composition (Christensen and Fountain, 1975; Zandt and Ammon, 1995); it is tried to correlate with local geology and rock type underneath the seismological stations along with laboratory estimates for common rock types (Christensen, 1996). Poisson's ratio values are sometimes affected by the presence of fluid content and partial melt in the crust (O'Connell and Budiansky, 1974; Owens and Zandt, 1997; Wang et al., 2010). Laboratory estimates suggest that it is low for felsic rocks with high silica content and it is high for mafic rocks (Christensen, 1996).
Review of the design methodology for the Bad Creek underground powerhouse as it would apply to a hard rock cavern design for Compressed Air Energy Storage (CAES)
Published in Bjørn Nilsen, Jørn Olsen, Storage of Gases in Rock Caverns, 2022
Hugh G. McKay, Richard E. Steffens, Betsy W. Curlin
The 27 sites studied classified into three categories: 1) suitable, 2) probably suitable, and 3) unsuitable. It was decided in this initial evaluation to define the sites with the most homogenous crystalline rock mass conditions as suitable. Sites with heterogeneous rock mass conditions are generally rated as probably suitable. Sites that are located in mafic rock units, very heterogeneous rock mass conditions (many repeating layers of different rock types), not underlain by hard crystalline rock, and/or located near a known major fault are rated as unsuitable.
Predictive quantitative model for assessing the asphalt-aggregate adhesion quality based on aggregate chemistry
Published in Road Materials and Pavement Design, 2021
Within siliceous rocks, the mafic-felsic classification is commonly used. Mafic rocks refer to those with relatively high contents of Mg and Fe (e.g. serpentinite, basalt and gabbro), whereas felsic rocks are those with high contents of quartz and feldspar minerals (e.g. granite, quartzarenite and granodiorite) (Marshak & Repcheck, 2009). It should be noted that since this classification is made for siliceous rocks, both mafic and felsic rocks have silica as their major constituent. For calcareous rocks, several different chemical classifications have been proposed (e.g. Dunham, 1962; Folk, 1980). However, for the pavement engineering field, a simpler classification based on its SiO2 content might be more useful. This is due to the fact that although the SiO2 contents in these rocks are naturally much lower than in the siliceous rocks, they have consistently been found to be the main culprit in the moisture susceptibility of the asphalt-aggregate system (Cala et al., 2019; Kim et al., 2008).
Petrogenesis of Jurassic Xietongmen intrusive rocks at the southern margin of the Lhasa terrane: implications for intra-oceanic arc evolution
Published in Australian Journal of Earth Sciences, 2020
The Jurassic Xietongmen intrusion includes voluminous intermediate–felsic rocks and minor mafic rocks, with the former also containing abundant MMEs, suggesting they record magma mixing (Figure 3f). The mafic rocks in this area are dominantly hornblende gabbros and gabbros that contain large amounts of hydrous minerals (e.g. amphibole; Figure 3). The intermediate–felsic intrusives in this region are hosted by gabbro–granitoid complexes, are medium- to high-K, calc-alkaline (Figure 4b), and metaluminous (0.90–0.98), suggesting they represent calc-alkaline I-type granitoids (Figure 9).