Plutonism (geological)
Under Plutonismus are understood geologic processes in which magma in the earth's crust penetrate and there to plutons solidify. The resulting rocks are called plutonites . B. the granite .
The plutons arise at greater depths of 5 km and more and largely correspond in their mineral composition to the volcanic rocks. However, these are predominantly basalts , while plutons are predominantly granites . The different manifestations are explained by the different physical and chemical formation conditions: The viscosity of the silicon-rich (“acid”) melts of the magma is significantly higher than that of the silicon-poor (“basic”) volcanic melts. In addition, the melting behavior is influenced by the water content : In the water-saturated systems of the Plutons, the melt volume increases when it rises ( pressure relief ), while it decreases in anhydrous basaltic systems. This results in the different appearances despite the same mineral compositions.