Magnmas
Páginas: 3 (518 palabras)
Publicado: 13 de marzo de 2012
Partial melting
Melting:
• Partial melting of crustal materials
gives GRANITES
• Partial melting of mantle materials
gives BASALTS/ANDESITES
Partiallymolten rocks
= migmatites
Differenciation
• Fractionnal crystallization • Other processes
Fractional crystallisation
22
10
Al2O3
17
MgO
5
Liquids composition
12
015
FeO* 10
10
CaO
5
5
Harker diagram for Crater Lake
0 6
0 4
Na2O
4
3 2
K2O
2
1
0 50 55 60 65 70 75 45 50 55 60 65 70 75
0 45
SiO2
SiO2Differenciation
• Always towards high SiO2 contents • Depending on the initial composition, this can mean…
– Evolution towards saturated rocks (rhyolites), as in sub-alkaline series – Evolution towardsunder-saturated rocks (phonolites), as in alkaline series – Little or no evolution… if the initial magma was already SiO2-rich !
Figure 4-21. Kangâmiut dike swarm in the Søndre Strømfjord region of SEGreenland. From Escher et al. (1976), Geology of Greenland, © The Geological Survey of Denmark and Greenland. 77-95.
Ploumanac’h, France
Torres del Paine, S. Chile
Half-dome granite(s),Yosemite, USA
a
b
N
Structures and Field Relationships
Figure 4-32. Developmental sequence of intrusions composing the Tuolumne Intrusive Series (after Bateman and Chappell, 1979), Geol. Soc.Amer. Bull., 90, 465-482. a. Original intrusion and solidification of marginal quartz diorite. b. Surge of magma followed by solidification of Half Dome Granodiorite. c. Second surge of magmafollowed by solidification of porphyritic facies of Half Dome Granodiorite. d. Third surge of magma followed by solidification of Cathedral Peak Granodiorite and final emplacement of Johnson Granite Porphry.Magma Magma
Marginal quartz diorite Half Dome granodiorite (porphyritic)
Half Dome granodiorite (non-porph) Cathedral Peak granodiorite
Johnson granite porphry
10 kilometers
c...
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