Chemical Composition Of Granite Gneiss

It is characterized by alternating light and dark bands differing in mineral composition coarser grained than schist.

Chemical composition of granite gneiss.

Depending on its chemical composition granite has specific geological petrographic names which are all grouped under the generic heading of granite. Gneiss is a medium to coarse grained semischistose metamorphic rock. Gneiss is a very widespread rock type especially in the lower parts of the continental crust but it is also a common rock on the surface in some places scandinavia canada and other shield areas where crystalline rocks are not covered by a layer of sedimentary rocks. Paragneiss results from the metamorphism of sedimentary rocks.

Gneiss can be classified on the basis of minerals that are present presumed formational processes chemical composition or probable parent material. A contact between gneiss granodioritic with migmatitic granite veins and granite pegmatite. Augen which means eyes is a coarse grained gneiss because of metamorphism of granite which incorporates characteristic elliptic or lenticular shear bound feldspar porphyroclasts typically microcline within the layering of the quartz biotite and magnetite bands. Other bands contain platy or elongate minerals with evidence of preferred orientation.

Rocks are naturally occurring solid masses or aggregates of minerals there are three major types of rocks as sedimentary rocks igneous rocks and metamorphic rocks. Paragneiss is gneiss derived from sedimentary rock such as sandstone. Granite is a very hard granular igneous stone. The random arrangement of grains in granite its lack of fabric is evidence of its plutonic origin.

Rock with the same composition as granite can form through long and intense metamorphism of sedimentary rocks. Orthogneiss is formed by the metamorphism of igneous rocks. Pink k feldspar gray quartz and. Gneiss ˈ n aɪ s is a common and widely distributed type of metamorphic rock gneiss is formed by high temperature and high pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks orthogneiss is gneiss derived from igneous rock such as granite.

Sio 2 71 84 tio 2 0 31 al 2 o 3 14 43 fe 2 o. This specimen has a composition of an ordinary granite. Average chemical composition of granite determined by 2485 chemical analyses of granitic rocks 3 numbers are mass percents recalculated volatile free to total 100. Augen gneiss from the german.

But that kind of rock has a strong fabric and is usually called granite gneiss. Gneiss is a foliated metamorphic rock identified by its bands and lenses of varying composition while other bands contain granular minerals with an interlocking texture. A sample from karelia russia. The main difference between gneiss and granite is that gneiss is a type of metamorphic rock whereas granite is a type of igneous rock.

Density melting point. The lighter bands contain mostly quartz and feldspar the darker often contain biotite hornblende garnet or graphite.