Lexikon

plutonic rocks (also called intrusive igneous rocks) resulted from magmas solidified below ground. When magmas crystallize deep underground they look different from volcanic rocks because they cool more slowly and, therefore, have larger crystals. Igneous rocks cooled beneath the Earth's surface are called intrusive rocks. The intrusive equivalents of basalt, andesite, and rhyolite are gabbro, diorite, and granite, respectively. In Hungary the Velencei mountain is composed of intrusive igneous rocks such as, granodiorite and diorite and the granite block in Mórágy was formed in similar conditions.

The underground crystallization stages of the magma are the following:
A. Preliminary crystallization stage (approx. 1100–1000 °C)
During the preliminary crsystallization stage ultrabasic and basic rocks are formed. The temperature decrease results separation of the silicate and sulphide melts. The preliminary crystallization gives economically important ore deposits: chromite, magnetite, ilmenite, platina, diamond and apatite.
B. Main crystallization stage (approx. 1000–700 °C)
In the main crystallization stage the magma solidification occurs. The olivine, pyroxene, amphiboles and the feldspars crystallize in parallel and finally the quartz.
C. Post magmatic stage (from approx. 700 °C)
The volatile containing residual magma is crystallised in this phase. The post magmatic stage includes three phases:

Pegmatite phase (approx. 700–550 °C): The mineral composition of the pegmatites crystallized in this phase is identical with that of the main crystallization phase however the pegmatites contain much larger crystals. The pegmatites in general occur in veins and are rich in rare elements such as stanium, uranium, thorium, boron, lithium, berillium, zirconium, titanium, tanthal.

Pneumatolitic phases (approx. 550–375 °C): The halogene rich solutions are chemically very active and thus are able to considerably modify the solidified rocks. This phase results various minerals such as quartz, fluorite, wolframite, turmaline.

Hydrothermal phase (from approx. 375 °C): The water diluted, solutions of the residual magma penetrated the cracks, voids of the rocks forming hydrothermal veins. During the hydrothermal phase mainly the following metals are concentrated: gold, silver, copper, lead, zinc, mercury and the iron, cobalt and nickel remained still in the residual solution.