Igneous rock

Igneous rocks making up the earth's crust is derived from magma freezing. Igneous word derived from Greek, from IGNIS word which means fire or incandescent. Because the magma is a material or materials that incandescent and very hot so-called igneous rocks Igneous Rock.
Liquid silicate magma is very hot with  C, which is mobile and° C to 1250 °temperatures ranging from 600  naturally formed (Larsen, 1938). Classification, naming and introduction to igneous rocks are very closely related to the way the formation of minerals contained in igneous rocks such. Some common mineral found as an important content, in the formation of the rule "crystallization rate" of magma. Each mineral will crystallize at a fixed temperature and consistently follow a finite temperature interval, at the time of magma cooling process is called magma differentiation.

A.    Classification of Igeous Rocks

Classification (classification) of igneous rocks can be based on three main benchmark, which is based on genetic rocks, based on the content of chemical compounds and based on the composition mineraloginya.

1)      Based on Genetic Rock

This classification is based on the genesis or the occurrence of igneous rocks, igneous rocks of this division is the division prior to the beginning of further classification of rocks. Genetic divide igneous rocks are as follows:

a.       Plutonic or intrusion, formed in an environment that deep in the bowels of the earth in conditions of high pressure so that the constituent minerals in larger sizes. Form of intrusion can be broadly divided into two, namely

• konkordan form, is a body of rock that have a relationship structure IMNI intrusive rocks with rocks around it in such a way that the boundary / field parallel to the bedding contacts the surrounding rocks. Books: sill, laccolith, phacolith, lopolith.

  

Figure Sill

Figure Laccolith

 

Figure Lopolith

• discordant forms, is a body of rock that have a relationship structure that cuts (not parallel) with the host rock diterobosnya. Books: dike, batolith, stock

figure dike

figure Stock dan Batholith

Body image forms of intrusion

a.       Hypabisal, formed in an environment not far from the earth's surface.

b.      Volcanics, formed on the surface of the earth in low pressure conditions so that the smaller the constituent minerals.

1)      Based on the Content of Chemical Compounds

Based on the content of chemical compounds (silica content), the igneous rocks can be divided into:

Acid rock is frozen: Silica> 65%

Frozen rocks  Medium: Silica 65-52%

Frozen rocks Languages: Silica 52-45%

frozen ultramafic rocks: Silica <45%

Whitford (1975) made a classification diagram to know the series and types of rocks based on the content of potassium and silica. Whitford divide the series into the series toleitik rocks, calc-alkaline series, and series of high-k calc-alkaline. While the type of rock is basalt, basaltic Andesite, Andesite and dacite.

According to Whitford (1975), any increase in K2O and SiO2 will experience changes in magmatic series ranging from calc-alkaline series toleitik up to high k calc alkaline, nor will experience changes in rock types ranging from basalt, basaltic Andesite, Andesite, to dacite.

3)  Based on the content of Mineraloginya

Based on the color index or the composition of dark minerals (mafic and felsic minerals). This classification is based on mineral composition of rocks, usually done under a microscope based on optical properties of minerals.

B.    Structure of igneous

Igneous structures can be distinguished as follows:

1.      Massive, overall appearance with a uniform look rock solid.

2.      Vesicular, on the rocks there are small holes, round or elliptical with unequal distribution. This hole is a hole trapped gas used at the time of the magma solidifies.

3.      Amigdaloidal, vesicular structures that have been filled by minerals

4.      Scorious, vesicular structures are spread evenly with holes that are interconnected.

5.      Flow, alignment of minerals in a particular direction with a clear orientation.

6.      Pillow lava ,lava-like structure shows a collection of pillows, this is because the form in the marine environment.

7.      Columnar Joint, which shows the structure as a collection of poles, this is due to a contraction in the cooling process.