Crystals settling to the bottom due to gravity are removed from further reaction with the melt - silica poor minerals at bottom of chamber, silica rich minerals at top 17 Page 18 CRYSTALLIZATION OF MAGMA Processes responsible for diversity of igneous rocks: 3) Continuous Reaction of the Melt and Early Formed Minerals - early formed crystals keep in contact with the melt, continuing to react with the melt forming minerals of different composition (BRS) 4) Crystallization of the Melt in a New Location - some of the melt can be squeezed into fracture surrounding the magma chamber - the minerals formed is lacking in early formed minerals giving rise to rocks of different composition 18 Page 19 CRYSTALLIZATION OF MAGMA Processes responsible for diversity of igneous rocks: Other mechanisms 5) Assimilation : incorporation of pre-existing country rocks (and reaction) into a magnetic melt - unmelted country rocks are called XENOLITHS 6) Mixing of magmas : two magmas of different composition merge e.g. basaltic + granitic = andesitic 7) Partial melting : produces magma with composition different from that of the parent rock (this the reverse of the Bowen's reaction series) 19 
(Crystals; settling; to the bottom due to gravity) (fracture; surrounding; the magma chamber) (early formed minerals; giving; rise; to rocks of different composition) (early; formed; minerals giving rise to rocks of different composition 18 Page 19 CRYSTALLIZATION OF MAGMA Processes responsible for diversity of igneous rocks: Other mechanisms 5) Assimilation : incorporation of pre-existing country rocks (and reaction) into a magnetic melt - unmelted country rocks) (two magmas of different composition; merge; ) (the minerals formed; is lacking; ) (3) Continuous Reaction of the Melt; Formed; T:Early) (two magmas of different composition; melting; ) (the minerals; formed; ) (the melt; forming; minerals of different composition (BRS) 4) Crystallization of the Melt in a New Location)
Crystals fracture early formed minerals early two magmas of different composition the minerals formed 3) Continuous Reaction of the Melt two magmas of different composition the minerals the melt
settling surrounding giving formed merge is lacking Formed melting formed forming
to the bottom due to gravity
the magma chamber
rise to rocks of different composition
minerals giving rise to rocks of different composition 18 Page 19 CRYSTALLIZATION OF MAGMA Processes responsible for diversity of igneous rocks: Other mechanisms 5) Assimilation : incorporation of pre-existing country rocks (and reaction) into a magnetic melt - unmelted country rocks
T:Early
minerals of different composition (BRS) 4) Crystallization of the Melt in a New Location