You should review Bowen's Reaction Series.

Please review the Bowen's reaction series.

Please avoid the Bowen's reaction series! It is a very old concept no longer valid. It can be chosen as a general rule, but each case requires specific considerations, rendering this concept no longer valid. Variation of H2O and CO2 content, magma mixing, crustal contamination processes and AFC processes can strongly influence the sequence of minerals appearing when a melt crystallizes.

Things are much more complex than the Bowen reaction scheme claims.

michele

In plate tectonics concept, continental crust is never subducted but continent-continent collision occurs leading to a thickened crust at the collision zone and partial melting of the generally sialic crustal material, producing granitic melt. In the course of ascent of the magma through the continental crust, the chemical composition is expected to change depending on the temperature of the magma, the specific path of ascent of the magma, i.e. the different lithologies the magma encounters and assimilates, etc.

In oceanic-continental crustal convergence it is the oceanic crust that is subducted, leading to generation of andesitic magma. Again, the magma's composition will depend on the same factors as explained above, in the course of its ascent through the continental crust.

Bowen's reaction series is applicable to magma that is mantle-derived considered initially basic/ultrabasic in composition.

Dear Muharrem Yavuz: You've got very good answers from other colleagues, but I must include that the temperature of the subducted oceanic plate also modifies the nature of the magmatic output in an active margin (and also in a volcanic island arc), such as the Andean, and others. The temperature and thickness of the oceanic lithosphere varies with the distance of the ridge to the trench. In the western coast of the Americas, the Mid-Pacific Ridge has been subducted under North America, generating both the Basin and Range Province, and the San Andreas Fault System. In a few tens of millions of years, it will be subducted first under Mexico-Central America (this is already happenning in Baja California), and later on, under South America (in 50 Ma or so). Episodes of ridge subduction may lead to the genesis of the relatively rare adakitic magma (a type of high-Mg andesite), supposed to represent direct partial fusion of the subducted oceanic crust (but other petrogenesis have been proposed too). Adakites are known from the Aleutian Arc (Adak island, is the type location), to Ecuador, Perú and Chile. Magmatic adakitic intervals are of short duration, and such flows are not easily to find in remote and high volcanoes, as those in the Andes, which surpass easily 5.000 m above sea level, and they surely represent a major change in the composition of the erupted material in the volcanic arc.

Regards, Sebastian Grande.

Dear Sebastián Grande, Thank you very much for sharing a key point for understanding the subduction related magmatism. This geodynamical approach gave me new insights. After the start of melting, there would be some trends in the properties of the melt (some properties increase, some other decreases) for an undefined time interval. But geodynamical factors are able to stop this trend. For example if subduction is rapid then the spreading in the middle ocean ridge then the spreading center will converge to the subduction zone and this will cause adakitic melts(in the case of Andes). Or in the case that spreading(on the ridge) is slower than the subduction, this time the slab become colder through time. So generalizing the trends of magmatism is not be valid for long time intervals in geological time.