Exempel på magma

• Sometimes, the magma below a volcano becomes even hotter and moves towards the top. 

• Suddenly, the top of the volcano breaks open, and thousands of kilograms of boiling magma and ash fly up into the air. 

• This is so hot that the rock is not hard, it is a boiling liquid called magma. 

• Volcanoes are mountains that have a lot of magma below them. 

• This characteristic also inhibits development of pronounced vertical zonation of the magma body.

• Crustally-contaminated andesites could be produced by combined assimilation and fractional crystallization of basaltic magmas.

• Second, differentiation, mixing, assimilation of magmas and alteration can produce compositional trends that can cross field boundaries within discrimination diagrams.

• These constituents are formed rapidly from cooled droplets of magma that take on dynamic shape during transport.

• Even if such a magma chamber extended through the entire crust, its height/diameter ratio would still be less than one.

• It is therefore likely that generation of the widespread intermediate-silicic magmas represents an early stage in the formation of continental crust.

• Constraints on melting and magma production in the crust.

• The rise of felsic magma to a high level in the crust without degassing or neutralization of the melt volatile phase suggests deep faulting.

• In particular, the heat for the melting may have been supplied by mafic mantle-derived magmas.

• The role of mantle plumes, particularly in the generation of flood basaltic magmas, has been emphasized by many authors.

• With all these processes, interactions between mantle-derived and crustal-derived magmas control the nature of magmatism in the complex.

• However, the geochemical data are consistent with derivation of magmas from a mantle source modified by subduction processes.

• The mafic magmas were probably derived from the upper mantle (spinel stability field) by 9 % partial melting.

• The magmas are of transitional (mildly alkalic) type, generated by relatively small-fraction (6-7 %) melting of a depleted mantle source.

• The evidence, including that of xenoliths carried in the magmas, supports the idea of melting of old metasomatized lithospheric mantle, usually associated with rifting tectonics.