Magma Differentiation

Magma is liquid or incandescent silicate solution that is formed naturally, with temperatures of between 9000 to 11,000 C and derived from the crust bottom or top of the envelope of the earth (Vide FFGrouts, 1947: Turner & Verheogan, 1960: H. Williams, 1962).

Natural silicate magma as a solution containing all the ions that would form all rock-forming minerals, but minerals are not formed simultaneously because it depends on silicate phase with certain conditions. Within the meaning of certain minerals will crystallize at certain temperatures and conditions.
Generally accepted opinion that the original magma is alkaline (Dally, 1933: Winkler Vide WT Huang, 1962). But the nature of the magma can be transformed into a magma with other properties, by processes called:

• Hybridization: is the formation of new magma, because the mixing of two different magma types.
• Sinteksis: is the process of forming new magma due to assimilation process with the country rocks or terlarutnya foreign rock into magma.
• Anateksis: is the formation of magma from the melting of rock at a depth of very big.from magma with this particular condition, then having a magnetic differentiation, are all processes that alter the large-scale homogeneous magma becomes igneous rock compositions berfariasi denagn (WT Huang, 1962).

These processes include:

1. Fractionation: separation of crystals from solution is at the time of the cooling of magma or the crystals in the magma cooling time can not keep abreast of new magma composition of the solution. This fractionation process is the most important differentiation process.
2. Gravitational Settling: is the precipitation of crystals by gravity, so that the heavy minerals that will enrich the base (magma reservoir) and were located under the lighter minerals.
3. Liquid Immissibility: is the solution of magma that have a high temperature and pressure, low temperature condensation will split into factions, each of which freezes to form a heterogeneous rock.

Composition
In common igneous minerals can be divided into two groups:
Minerals - minerals felsik; composed of silica and alumina, usually brightly colored.
Minerals include:
                   - Quartz         - Plagioclase
                   - Ortoklas      - muscovite

Mineral - mafic minerals; composed of the elements - magnesium, calcium, iron elements, generally minerals - mineral dark.
Minerals include:   - olivine           - pyroxene
                             - Hornblende   - Biotite

Based on the genesis of igneous rocks can be divided into intrusive igneous rocks (frozen below the earth's surface) and extrusive igneous rocks (frozen surface of the earth). In addition igneous rocks can also be divided into 3 groups:
1. Igneous rocks are volcanic.
Usually have relatively fine crystal size, because the frozen surface or near the surface of the earth.

2. Igneous hipabisal.
Usually has a crystal - a medium-sized crystals or mixing between rough and smooth, because the freeze on the surface of the earth.

3. Plutonic igneous rocks.
Usually has a crystal - the crystal size coarse, because frozen deep in the earth's surface.
The above groups can be distinguished by looking at the size of the crystal. Volcanic igneous rocks can be divided into 3 types, namely, instrusif volcanic rocks, extrusive igneous rock (ekplosif) which is often referred to fragmental rocks and volcanic rocks of extrusive (effusive), such as lava flows.

In Indonesia, more dominated by extrusive igneous rock texture or often referred to fragmental pyroclastic rocks which will be grouped with different classification with non-fragmental igneous rocks.