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Published in A. Bahurudeen, P.V.P. Moorthi, Testing of Construction Materials, 2020
Any rock can be transformed into metamorphic rocks. Meta means “change” and morph means “form”; consequently, “metamorphic” means “change of form”. It refers to the change in the form of their mineralogical composition by altering them from equilibrium to unstable condition by the application of external pressure and temperature. Finally, restoration of equilibrium, i.e. changes from unstable form to the stable form, results in the formation of transformed rock. Generally occurring metamorphic rocks are slate, schist, gneiss and marble. Some of the artificial aggregates are coarse blast furnace slag, ceramic waste, etc.
Our Earth, its minerals and ore bodies
Published in Odwyn Jones, Mehrooz Aspandiar, Allison Dugdale, Neal Leggo, Ian Glacken, Bryan Smith, The Business of Mining, 2019
Odwyn Jones, Mehrooz Aspandiar, Allison Dugdale, Neal Leggo, Ian Glacken, Bryan Smith
Metamorphic rocks are developed within the crust. Metamorphism is a gradual process by which the minerals and texture of rocks, which may be igneous, sedimentary or metamorphic, change in response to increasing temperature and/or pressure with burial. Minerals that are stable at the earth’s surface become unstable under specific temperature and pressure conditions and will undergo crystal lattice modifications to create a new mineral phase that is stable under the new conditions. This process will continue to occur with increasing depths within the crust. Commonly meta-morphism occurs in response to regional scale deformation processes due to larger-scale lithospheric plate movements. Where the plates collide in convergent zones the crust is thickened in response to compressive forces much like squeezing an accordion. Metamorphic rocks in the deeper parts of the crust become like plasticine due to the elevated temperature and pressure, whereas weakly metamorphosed rocks in the mid to upper portions of the crust are brittle. So that in areas of compression (e.g. convergent lithospheric plate boundaries) the metamorphic rocks deep in the crust will fold and those in the mid to upper crust will fail, forming faults and thrusts.
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
Burial metamorphism grades into regional metamorphism as temperature and pressure increase. Regional metamorphism, which occurs over millions of years, is not generally due to overlying layers of sediment being deposited and compressing rocks below but is caused by burial and heating associated with mountain-building events (orogenies), such as the one that affected the Adirondack Mountains. The mountain building, which occurs in orogenic belts, may be caused by continental collision or by tectonism at subduction zones and can affect very large areas. As the crust thickens and rocks become buried, the amount of metamorphism increases with depth in Earth. Generally, the greatest burial occurs near the centers of orogenic belts, so we commonly find high pressure-temperature (PT) metamorphic rocks in the centers of mountain ranges, with lower PT rocks near the range margins.
Orange, Yellow, Brownish Stains and Alteration on White Marble at El Montazah in Alexandria, Egypt
Published in International Journal of Architectural Heritage, 2021
Marble is a metamorphic stone composed of carbonate minerals (calcite and/or dolomite), in which calcite usually excesses of 95%. It is formed as a result of the recrystallization of limestone under the intense pressure and heat of geologic processes. The effect of metamorphic process is the creation of a stone with a very tight crystalline structure and change in textural properties such as grain size, shape and boundaries. Because of its structure, marble can take a very high polish and it is a very popular decorative stone for several applications such as building material, sculptural and ornamental purposes from the early-historic periods (late Neolithic – early Bronze Age culture), to the Greek and Roman times. Romans transported large quantities of marble from ancient Mediterranean quarries to the most near eastern archaeological sites (Capedri, Venturelli, and Photiades 2004).
Assessing groundwater quality and health risks of fluoride pollution in the Shasler Vagu (SV) watershed of Nalgonda, India
Published in Human and Ecological Risk Assessment: An International Journal, 2020
Narsimha Adimalla, Sudheer Kumar Marsetty, Panpan Xu
Shasler Vagu (SV) watershed is located in the southwest of Nalgonda district, India in between north latitudes from 16°55' to 17°00' and east longitudes from 78°45' to 79°10'. The study area falls in the Survey of India Toposheet Nos. 56 L/13 and 56 P/1 and covering an area of about 365 km2. Geologically, the study region is underline by Peninsular Gneissic Complex (PGC), and the dominant rock type are of granite and granite gneiss. Younger intrusive include gabbro, dolerite and hornblendite, apatite, pegmatite, quartz and epidote veins, and alluvium. Older metamorphic rocks include hornblende schists, amphibolites, banded magnetite quartzite, meta-basalt, and biotite schist. In the investigated area, biotite schist rock occurs as lenses, schlieren, and inclusion within the migmatitic gneisses. The exposures of biotite schist are oval shaped trending NNW-SSE in the study area. Low-grade metamorphosed basic igneous rock occurs as enclaves within the porphyritic granite, while banded magnetite quartzite is narrow bands trending NW-SE. Hornblende and amphibolite schist are mainly consisted of hornblende and plagioclase as an essential mineral, while quartz, sphene, sericite, and magnetite occur as accessory minerals. These rocks occur as elongated in N–S direction with vertical dip. The migmatite rocks are medium to coarse-grained in nature and are well exposed, while biotite gneisses are generally banded in nature and occur as sheets and inselbergs in low topographic areas (CGWB 2013; Sudheer Kumar et al. 2017).
Sedimentology in metamorphic rocks, the Willyama Supergroup, Broken Hill, Australia
Published in Australian Journal of Earth Sciences, 2018
B. P. J. Stevens, G. M. Bradley
Attempting to undertake sedimentological analysis in high-grade metamorphic rocks presents challenges, especially in Precambrian rocks with no fossils or trace fossils (bioturbation). There are major challenges in seeing through the changes produced by metamorphism and deformation. Metamorphism, particularly high-grade metamorphism, involves chemical reactions, recrystallisation, coarsening of grainsize and obliteration of fine-scale sedimentary features. Accompanying deformation can attenuate and/or transpose bedding. Ultimately all sedimentary features may be obliterated. However, even in high-grade metamorphic rocks, clues may be preserved. A separate challenge is the tendency of geologists working in metamorphic terranes to concentrate on metamorphic petrology and to only see deformation structure, while geologists trained in sedimentology tend to avoid such areas. The present study attempts to bridge this gap in the upper greenschist to granulite grade Willyama Supergroup at Broken Hill, Australia (Figure 1).