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Shear behaviour of joints under heat in direct shear
Published in Hans Peter Rossmanith, Mechanics of Jointed and Faulted Rock, 2020
H. Aydin Bilgin, A. Günham Paşamehmetoğlu
Petrographie descriptions of the tested rock types are given below: Andesite: Straight to dark pinkish coloured, massive to compact vesicular andesite. In the thin section euhedral plagioclase phenocrystals of andesine composition and mafic minerals are observed. Matrix is composed of very fine plagioclase lets and volcanic glass. Plagioclase lets show flow texture within the groundmass.Limestone is yellowish white to buff coloured and slightly to moderately porous. Rock is mainly composed of calcite crystals (400 to 50 micron size range) aggregates. Place to place rock shows approximately 1 mm size calcite filling the pores.Bluish or light green coloured shale is massive except rare plant material along bedding planes. In the thin section microscopic mineral assemblages are mainly cryptocrystalline size calcite crystals, clay minerals, sericite, chlorite and minor amount of quartz.
Igneous Rocks
Published in F.G.H. Blyth, M. H. de Freitas, A Geology for Engineers, 2017
F.G.H. Blyth, M. H. de Freitas
The Skaergaard intrusion is shaped like an inverted cone or funnel, with an area of 50 km2 at the surface, and is exposed on the east coast of Greenland to a vertical depth of some 2500 m; the funnel-shaped mass may continue below this for a similar distance. The lowest part of the exposed gabbro possesses a nearly horizontal layering, consisting of dark bands rich in olivine (formed by the gravity-settling of olivine crystals in the magma) separated by broader bands of olivine-gabbro and hypersthene gabbro. A small scale layering which is repeated many times is called rhythmic banding. The layered rocks pass upwards into gabbros without olivine, succeeded by iron-rich gabbros and finally by quartz-gabbros. The plagioclase in the gabbros ranges from labradorite in the lower rocks to andesine in the upper. At the margins of the mass fine-grained gabbros are present.
Igneous rocks
Published in W.S. MacKenzie, A.E. Adams, K.H. Brodie, Rocks and Minerals in Thin Section, 2017
W.S. MacKenzie, A.E. Adams, K.H. Brodie
This rock (Figure 101, Figure 102) can be seen to consist mainly of microphenocrysts of two minerals in a fine-grained groundmass in which one of the constituents is plagioclase feldspar. The feldspar microphenocrysts are clear in the plane-polarized light view (Figure 101) and show grey to white interference colours and multiple twinning in the view with crossed polars (Figure 102). The approximate composition of the plagioclase feldspar can be obtained from extinction angle measurements and is found in this case to be andesine. In addition to multiple twinning, zoning can be seen in some of the feldspar crystals.
Petrogenesis of the Hoy lava field, a long-lived continental mafic volcanic province in eastern Australia
Published in Australian Journal of Earth Sciences, 2023
T. J. Crossingham, T. Ubide, P. M. Vasconcelos, K. M. Knesel
Plagioclase is typically restricted to the rock groundmass, with macrocrysts only present in two samples from the Hoy lavas: Mount Llandillo and Mount Leura. The larger (∼750 µm), euhedral Mount Llandillo plagioclase has an anorthite (An93) core and labradorite (An63–68) rim. The smaller (∼450–500 µm) Mount Leura subhedral, sieved plagioclases have labradorite to andesine cores (An35–59), labradorite enrichment zones (An58–59) and labradorite to oligoclase rims (An21–51). Groundmass feldspar from Policeman’s Knob consists of andesine (An29–46) and rare anorthoclase (An7–10). In contrast, groundmass feldspars from all other samples (excluding Anakie Hills whose groundmass feldspars were not analysed) include labradorite (An68–53), andesine (An46–43) and rare sanidine (An2).
Detrimental effects of low-rank coal utilization to the operational condition of large capacity updraft moving-bed gasifier
Published in International Journal of Coal Preparation and Utilization, 2022
Phiciato Phiciato, Miftahul Huda
The fact that EDS only provides localized elemental information of small spots such as element distribution and their relative proportions, the compounds composition obtained by this method is inaccurate. As a comparison, we performed XRD whose diffraction patterns of each sample are shown in Figure 18. Surprisingly the deposit material of Top and Bottom sample does not consist of slag compounds but it is primarily comprised of hematite and magnetite. Slag compounds are not detectable in the deposit material because the amount of slag material is very small. It is also important to mention here that the major compound of Slag material is Andesine; NaCa(Al2Si)ASi2 which is categorized as feldspar group material. It has a relatively low melting point thanks to the presence of alkali elements (Na, Ca) which act like fluxing materials during the combustion process. The effect of fluxing materials to the low melting point of slag is known in literatures (Song et al. 2010; Wang and Massoudi 2013). The melting point of slag tends to decrease with the increase of Na2O and CaO content while Al2O3 and SiO2 increase this value. Thus, it can be concluded that slag material in this experiment has melted because of its high alkali content such as Na and Ca.
Cretaceous igneous-related mineralisation in the Reefton Goldfield, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2019
Jim E. Dickie, James M. Scott, Matt W. Sagar, Hamish Blakemore
There are two textural types of Greenland Group present. The first type occurs to the east of the granitoid dike; here, distal (non-hornfelsed) meta-greywacke is dominated by coarse to fine-grained detrital sandstones of moderately to well-sorted sub-angular to well-rounded detrital quartz, plagioclase and K-feldspar. Biotite and epidote occur sporadically and are partially decomposed and may be detrital. Anhedral to subhedral grains of metamorphic muscovite and minor chlorite fill interstitial space in the matrix, and their orientation defines a weak cleavage (Figure 4(A)). Accessory magnetite is also present. Argillites consist of muscovite, quartz and chlorite, with minor detrital feldspar and biotite. A spaced, disjointed foliation is defined by pressure solution seams and enhanced by preferred alignment of quartz and muscovite. This foliation anastomoses around detrital quartz grains. In textural regard, the Greenland Group east of the dike is identical to ‘Type I’ of Ritchie et al. (2015). Type I Greenland Group begins to display spotted hornfels textures at about 50 m from the dike. The spots are typically composed of biotite (Figure 4(B)) or pale patches of sericite. The associated plagioclase is andesine to labradorite. Pyrite is present and in one sample was found to be inter-grown with andalusite.