Pneumatolysis

Pneumatolysis ( from the Greek pneuma solve = wind, air and lyein =) is a form of rock alteration. It is primarily for the formation of deposits of significance.

It takes place during the cooling and partial crystallization of magma under high pressure deep inside the earth. The volume of the magma decreases. At the same time, volatile substances such as water, carbon dioxide, hydrogen fluoride, hydrogen chloride, boron, beryllium, and heavy and precious metals accumulate in it and let the gas pressure of the melt increases.

The aggressive acidic siliceous gases exceeds the ambient pressure, so penetrate deep into the surrounding rock. Due to the high temperatures this is partially remelted. Pressure changes lead to complex boiling and distillation processes of the invading gases that lead to the formation of new minerals and ores. Insofar as the pneumatolysis is a special case of a contact metamorphosis.

Pneumatolytic processes lead to the formation of greisen and characteristic vein deposits of tin, tungsten, molybdenum, and copper ores. Typical gemstone developments are rubies, sapphires, emeralds and Nephrite.

• Petrology