Question

3. Classify the Metamorphic Rocks according to their depths and evaluate them in terms of their usability as foundation, tunnel and material (aggregate, anchoring, building block, etc.).

Answer 1

Ans

Metamorphic Rock
Metamorphic rocks are rocks formed from pre-existing rocks, the mineralogy, chemistry and texture of which have been changed by heat and pressure deep within the earth’s crust.
From: Seismic Data Analysis Techniques in Hydrocarbon Exploration, 2014
Related terms:
ShaleUraniumTroughOil ReservoirPhyllitesPorosity
View all Topics
Rock Fracture and Rock Strength
Zong-Xian Zhang, in Rock Fracture and Blasting, 2016
3.1.2 Metamorphic Rock
Metamorphic rock is the result of the transformation of an existing rock type, the protolith, in a process called metamorphism. The protolith is subjected to heat and pressure causing profound physical and chemical change. The protolith may be sedimentary rock, igneous rock, or another (older) metamorphic rock. Metamorphic rock may be formed when magma is injected into the surrounding solid rock, as shown in Fig. 3.1b. It may be formed simply by being deep beneath the Earth’s surface, subjected to high temperatures and the great pressure of the rock layers above it. Metamorphic rock can also be formed from tectonic processes such as continental collisions. Some examples of metamorphic rocks are gneiss, slate, marble, schist, quartzite, hornblende, and phyllite. Most of metamorphic rocks have good crystallization, compact textures, high strength, small porosity, and low water permeability. Some metamorphic rocks, such as marble and quartzite, can be well considered as homogeneous isotropy. However, if foliation is high, the contact between mineral grains is usually bad, and the rock shows anisotropy.
View chapterPurchase book
Grinding: Principles and Theories
Jean-Paul Duroudier, in Size Reduction of Divided Solids, 2016
1.1.4 Heterogeneous rocks
Metamorphic rocks are extremely heterogeneous, especially if they contain a significant amount of mica (metamorphic rocks structure has been modified by pressure or temperature). Rocks exposed to weathering are also heterogeneous from the fact that their inter-granular surfaces have disintegrated (particularly in those with cemented grains). Shale is an example of a heterogeneous rock.
In the fines region, we see a maximum M2 which corresponds to an average grain size x¯ of rocks held together by a “cement” or pressure. The more the number of large grains in the rock, the more the maximum M2 shifts to the right.
If all the grains in the rock have a similar size, then the maximum M2 is very sharp. Some rocks display 2 or 3 maxima of the type M2.
Metamorphic rocks are very heterogeneous (gneisses).
Grain boundaries are weak zones. Wind and water erode heterogeneous rocks as grain boundaries are quickly broken down.
If a rock is permeable to moisture, it will be sensitive to freezing.
Some grains in rocks are more difficult to break. The result is 2 or 3 maxima in variations of mj function of xj (see Figure 1.4).

Sign in to download full-size image
Figure 1.4. Granulometry of a heterogeneous rock
View chapterPurchase book
Building Decorative Stone
In Building Decorative Materials, 2011
3 Metamorphic Rock
Metamorphic rock is made when magmatic or sedimentary or even other metamorphic rock is subjected to high temperature and extreme pressure inside the crust. According to the changes that take place in the course of metamorphism alteration, it is further divided into ortho-metamorphic and para-metamorphic rocks.
Ortho-metamorphic rock is metamorphosed from magmatic rock. After metamorphosis, its structure and performances are weaker than those of the primary rock. For instance, gneiss which is metamorphosed from granite rock is more likely to delaminate and flake off, and its durability becomes weaker.
Para-metamorphic rock is metamorphosed from sedimentary rock. After metamorphosis, its structure and performances are better than those of the primary rock. For instance, marble, metamorphosed from lime-rock, has denser structure and stronger durability.
Commonly-used metamorphic rocks are marble, quartz rock and gneiss.
View chapterPurchase boo