GEOG 150 Lecture Notes - Lecture 5: Silicate Minerals, Igneous Textures, Pyroxene
General characteristics of magma
-Parent Material of igneous rocks
-Forms from Partial Melting Rocks
-Magma at surface is called Lava
Lava
Magma at surface is called
Volatiles
Are dissolved gasses in the melt that vaporize at surface pressure
Crystallization
is the cooling of magma which results in the systematic arrangement of ions into orderly patterns
Plutonic/ Intrusive Igneous Rocks
Magma that crystallizes at depth forms
Volcanic or Extrusive Igneous Rocks
The solidification of lava or volcanic debris forms
Granitic or Felsic Composition
-Light-colored silicates
-Composed almost entirely of quartz and potassium feldspar
-Termed felsic (feldspar and silica) in composition
-Highly Silica content
-Major constituent of continental Crust
Basaltic Or Mafic Composition
-Dark silicates and calcium rich feldspar
-Termed Mafic
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Higher density than granitic rocks
-compromise the ocean floor and many volcanic islands
Andesitic or intermediate
-contains 25 percent of more dark silicate minerals
(AMPHIBOLE, PYROXENE, AND BIOTITE MICA)
-Associated with Volcanic Island Arcs
Ultramafic Composition
-Rare composition of mostly olivine and pyroxene
-Composed almost entirely of ferromagnesium minerals
-Peridotite is and example
Texture
the overall appearance of a rock based on the size, shape and arrangement of mineral grains
Aphanitic (fine grained texture)
Phaneritic (coarse-grained) texture
TYPES OF IGNEOUS TEXTURES
Phenocrysts
groundmass
Large crystals ____ are embedded in a ,matrix of smaller crsytals ___
Vesicular Textures
-rocks contain voids left by gas bubbles in the lava (air pockets)
Glassy Texture
-Very Rapid Cooling
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Document Summary
Are dissolved gasses in the melt that vaporize at surface pressure. Crystallization is the cooling of magma which results in the systematic arrangement of ions into orderly patterns. The solidification of lava or volcanic debris forms. Composed almost entirely of quartz and potassium feldspar. Compromise the ocean floor and many volcanic islands. Contains 25 percent of more dark silicate minerals (amphibole, pyroxene, and biotite mica) Texture the overall appearance of a rock based on the size, shape and arrangement of mineral grains. Large crystals ____ are embedded in a ,matrix of smaller crsytals ___ Rocks contain voids left by gas bubbles in the lava (air pockets) Forms from the consolidation of individual rock fragments ejected during explosive eruption. Form is late stages of crystallizations of magmas. 10-20 percent quartz, roughly 50 percent potassium felspar. Forms when silicia-rich lava cools quickly on earth surface. Glassy texture rock that forms when large amounts of gas espace the lava.
