f unidad 2 magma

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M.Sc. SANDRA MANOSALVA

ACTUALIZADO: 2010

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Rocas ígneas extrusivas- Lava (Hawaii)

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Nuevo modelo del manto

Figure 10-16b After Basaltic Volcanism Study Project (1981). Lunar and Planetary Institute.

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En el borde de placas principalmente

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Porqué se hunde una placa al chocar?

Porqué hay vulcanismo, magmatismo?

Porqué se funden las rocas que subducen?

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El agua y los gases disueltos

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TIPO 1. HIMALAYA TIPO 2. CHILE TIPO 3. MARIANAS

O I l d A (IA)

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Ocean-ocean Island Arc (IA)Ocean-continent Continental Arc or

Active Continental Margin (ACM)

Figure 16-1. Principal subduction zones associated with orogenic volcanism and plutonism. Triangles are on theoverriding plate. PBS = Papuan-Bismarck-Solomon-New Hebrides arc. After Wilson (1989) Igneous Petrogenesis,

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Figure 17-1. Map of western South Americashowing the plate tectonic framework, and thedistribution of volcanics and crustal types. NVZ,CVZ, and SVZ are the northern, central, andsouthern volcanic zones. After Thorpe and Francis(1979) Tectonophys. , 57, 53-70; Thorpe et al. (1982)

In R. S. Thorpe (ed.), (1982). Andesites. Orogenic Andesites and Related Rocks. John Wiley & Sons.New York, pp. 188-205; and Harmon et al. (1984) J.Geol. Soc. London, 141, 803-822. Winter (2001) AnIntroduction to Igneous and MetamorphicPetrology. Prentice Hall.

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Figure 17-15b. Major plutons of the SouthAmerican Cordillera, a principal segment ofa continuous Mesozoic-Tertiary belt from theAleutians to Antarctica. After USGS.

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Good diagram forthe Andes Mountains

Small blobs, not much heat in themAssimilate some crust, fractionate

BASALTIC

ANDESITIC

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17Andesites form above the deep portions of a subduction zone

Andes

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Figure 17-2. Schematic diagram to illustrate how ashallow dip of the subducting slab can pinch outthe asthenosphere from the overlying mantlewedge. Winter (2001) An Introduction to Igneousand Metamorphic Petrology. Prentice Hall.

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Huge blobs w/ lowtemps but lots ofmagma, fractionation &assimilation => GraniteBatholiths

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DORSALES MESO-OCEÁNICAS (Mid-OceanRifts Basalts)

MORB

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Typical Ophiolite

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The Mid-Ocean Ridge System

Figure 13-1. After Minster et al.

(1974) Geophys. J. Roy. Astr.Soc., 36, 541-576.

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OIB: Oceanic intraplate basalts

O i l d d t

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Ocean islands and seamountsCommonly associated with hot spots

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Ocean islands and seamounts

Commonly associated with hot spots

 Volcanism

Figure 14-1. After Crough (1983)Ann. Rev. Earth Planet. Sci., 11, 165-

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MagmaType

Solidified Rock Chemical Composition Temperature Viscosity Gas Content

Basaltic Basalt45-55 SiO2 %, high in Fe, Mg, Ca,low in K, Na

1000 - 1200 oC 10 - 103 PaS Low

Andesitic Andesite55-65 SiO2 %, intermediate in Fe,Mg, Ca, Na, K 800 - 1000 oC 103 - 105 PaS Intermediate

Rhyolitic Rhyolite 65-75 SiO2 %, low in Fe, Mg, Ca,high in K, Na.

650 - 800 oC 105 - 109 PaS High