Igneous Rocks 3 Flashcards

Terms Definitions
aphanitic intermediate
Ultramafic and aphanitic
Vesicular, light colored
intrusive igneous rock
formed underground
Intermediate Felsic
Volcanic: Dacite
Plutonic: Granodiorite
produced from melting continental rocks, rich in silica and poor in iron and magnesium
coarse-grained, crystals are large enough to be seen w/out a microscope, formed by slow cooling (intrusive)
An intrusive, phaneritic, mafic igneous rock.
Below ground- plutonic. Granite. Large crystals.
flux melting
volatiles decrease the melting temperature
the extrusive equivalent of granite and, like granite, is composed essentially of the light-colored silicates.
gaseous components of magma, will vaporize at surface presure.
Porphyritic Andesite
porphyritic aphanitic, andesitic, it doesnt scratch on glass
Igneous Rocks
formed from magma or lava
Ultramafic, largely made up of olivine, but also made up of plagioclase and augite
the outer layer of the Earth
cools quickly at or near surface
naturally, produced when molten lava cools too rapidly to permit recrystallization. The volcanic form is a solid composed of unordered atoms
the melted rock earth is formed form
what type of magma has intermediate density and melting point?
granitic composition
the composition that igneous rocks composed mainly of light-colored silicates (quartz and feldspar) have
a large discordant pluton with an areal extent at earth's surface greater than 100 square km
Mafic Rocks
Also called basaltic rocks because they are dark in color and are iron rich.
Intermediate Minerals
describes igneous rocks (ex. andesite, diorite), and the magmas they crystallize from, that have a composition in between that of mafic and felsic rocks and magmas (medium silica)
magma that flowed between two layers and hardened
Rare, ultramafic rock that can contain diamonds and other minerals formed only under very high pressures
Melilite rock
o >10% melilite (the mineral)
o Otherwise ultramafic foiditic rock
Cinder Cone
A relatively small volcano made primarily of pyroclastic materials ejected from a single cone. They are steep-sided and erupt only tephra.
fractional crystallization
The process by which the crystals formed in a cooling magma are segregated from the remaining liquid at progressively lower temperatures.
the process of magma rising to the surface and flows as lava and/or proclastic materials and gases
ex. responsible for all extrusive igneous rock such as basalt, tuff and obsidian
having very small grains that are hard to see with the naked eye, like basalt and rhyolite
decompression melting
partial melting of hot mantle rock when it moves upward and the pressure is reduced to the extent that the melting point drops to the temperature of the body
Dikes, sills
_______ cut across layers of country rock, _______ run parallel.
intrusive rock
igneous rock that formed when magma hardened beneath Earth's surface
smaller domes that push up the earth's surface
chemical sedimentary rock
sedimentary rock that forms when minerals precipitate from a solution or settle from a suspension.
silica is the material that causes rocks to have
light color
fragmental texture
an igneous rock texture resulting from the consolidation of individual rock fragments that are ejected during a violent volcanic eruption
aphanitic texture
a texture of igneous rocks in which the crystals are too small for individual minerals to be distinguished with the unaided eye
Extrusive Rocks
Rock that is formed from the magma cooling and crystallizing on Earth's surface
Igneous Texture influenced by
- Cooling rate
- Depth
- Crystal nucleation rates
- Crystal growth rates
- Rate of undercooling
- Ion availability
- Diffusion rates
- Viscosity
- Chemical composition
- Gas content
smooth because of small crystals
extrusive rocks are rough or smooth
A ______ is a large crystal that is a different size from the rock surrounding it because it cooled differently.
there dense and durable
why have people through out history used igneous rocks for tools and building maerials
molten rock
rock that is so hot it is a very thick, slow-moving liquid.
When does partial melting occur?
1. When mantle rocks are heated to temperatures above their solidus temperature, 2. The solidus temperature is reduced due to the addition of volatiles.
7 steps to igneous rock classification
- If rock is fragmental it is described as a pyroclastic rock
- If modal primary carbonate is >50% = carbonatite
- For a mafic/ultramafic rock where A, P, F minerals are absent or only in ground mass:
o Lamproite, Lamprophyre or Kimberlite
- If rock has M>90% and model melilite is >10% then it is an ultramafic melilitic rock
- If the rock is felsic and contains opx is is a Charnockite
- If its phaneritic, it is a plutonic rock
- Aphanitic, it is a volcanic rock
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