Igneous Rock Summary. Copy to your notes.
Composition: Basaltic/Gabbroic (Mafic)
Andesitic/Dioritic (Intermediate)
Sources: 1.Decompression melting at Rift or MOR
& cause above rising mantle convection
Above subduction zone
water induced melting with
fractionation & assimilation
Granitic/Rhyolitic (Felsic)
1.Above subduction zone or
2.continental plume with more
fractionation and assimilation
2. Ocean hot spot from deep mantle plume
Extrusive 1. Cinder (MOR Iceland), Great Rift Valley
(Volcano) 2. Shield (Hawaii)
Intrusive
(Plutons)
MOR Gabbro under Pillow Basalts
Silica
Temperature
Lava Viscosity
Gasses
Composite
Andes, Cascades (Mt.St.Helens)
Japan (Mt. Fujiyama),Vesuvius
Diorite Batholiths
Sierra Nevada
Huge Caldera
Yellowstone, Toba
<= Yosemite=>
Granite Batholiths
Low
Intermediate
High
Hot
Intermediate
Not as hot
Low (lava is runny)
Easily released
Eruptions
gentle
Products
1. Flood Basalts Scoria
Pillow lavas MOR
2. pahoehoe near vent
a'a' away from vent
Color
Dark, Green to gray
Minerals:
accessory:
Pyroxene, Ca-Plagioclase Feldspar
Olivine
High (molasses)
Very High like hot tar
Not easily released
Not easily released
explosive
Tuffs
nuée ardente
lahars
Pumice
medium Gray
Amphiboles, Na- Plagioclase Fldsp.
Biotite Mica
catastrophic
Extensive thick tuffs
light gray and pink or white
Quartz, K-Feldspar
Micas, etc.