Granite
The
granitization theory states that granite is formed in place by extreme
metamorphism.
The History Says
The 'alphabet soup' scheme of Chappel & White was proposed
initially to divide granites into I-type granite (igneous protolith)
and S-type granite (sedimentary protolith). Both of these types of
granite are formed by melting of high grade metamorphic rocks, either
other granite or depleted mantle, or buried and subducted sediment,
respectively.
The Present Scenario
Granite has been extensively used as a dimension stone, flooring
tiles in public and commercial buildings and monuments, and in
kitchens.
Granite
is a common and widely-occurring group of intrusive felsic igneous
rocks. It consosits of orthoclase and plagioclase feldspars, quartz,
hornblende, biotite, muscovite and minor accessory minerals, like
magnetite, garnet, zircon and apatite. Ordinary granite always
contains a small amount of plagioclase. With the absence of
plagioclase, it is known as alkali granite.
Uses of Granite
The Red Pyramid, third largest Egyptian pyramids, of Ancient Egypt
(c. 26th century BC) was made by granite. Menkaure's Pyramid, dating
in the same era, was also constructed with granite blocks apart from
limestone. The Gread Pyramid of Giza (c. 2580 BC) has a huge granite
sarcophagus fashioned of "Red Aswan Granite." The ruined
Black Pyramid during the reign of Amenemhat III had a polished granite
pyramidion or capstone. It is now on display in the main hall of the
Egyptian Museum in Cairo. The Ancient Egypt also used it in door
lintels, sills, jambs, and wall and floor veneer.
Currently, granite is extensively being used as a dimension stone and
as flooring tiles in and public as well as commercial buildings and
monuments. The polished granite is a demanding choice for kitchen
countertops because of its high durability and aesthetic qualities. In
sports world, curling rocks are traditionally being fashioned of
granite.
Occurrences
of Granite
Granite occurs even in a very small mass, like 100 km2, and as large
as batholiths, which is often associated with orogenic mountain ranges
and is frequently of great extent. Smaller dikes of granite
composition, known as aplites, are associated with granite margins. In
some locations, a very coarse-grained pegmatite masses occur with
granite.
Granite occurred into the Earth's crust during all geologic periods,
much in Precambrian age. It is widely distributed throughout the
continental crust of the Earth and is the most abundant basement rock.
It underlies the relatively thin sedimentary rock veneer of the
continents.
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