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26 Cards in this Set

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Igneous Rocks
Formed by the freezing of molten rock coming from the mantle. Freezing means 650-1100 C.
Magma
molten rock below Earth's surface
Lava
molten rock at Earth's surface
If crystallization of rock happens below surface / at suface…
...intrusive / extrusive igneous rock.
How do we get magma? (3)
1. Decompression, 2. Addition of volatiles to rock, 3. Heat transfer
Decompression
As pressure decreases, magma can form.
Addition of volatiles
Water / CO2 gets added to hot, dry rock, and as it diffuses, it begins to melt. The volatiles break chemical bonds, which cause the melting.
Heat Transfer
Rising magma melts rock it intrudes.
Felsic Magma
Rhyolitic, very high in sulfate (76-66%), quartz, k.feld, light colored rock
Intermediate Magma
Andesitic, high in sulfate, quartz, Ca/Na-plagioclase, salt and pepper look
Mafic Magma
Olivine, pyroxene, calcium rich
Ultramafic Magma
Olivine, pyroxene, green undertone
Why does magma composition vary? (5)
1. Source rocks, 2. Mixing, 3. Assimilation, 4. Xenoliths, 5. Partial melting
Xenoliths
pieces of country rock that break off into magma but don't melt (assimilation)
Partial melting
Felsic melts first, migrating towards the surface first and leaving mafic solids behind
Fractional crystallization
crystals settle out while cooling, mafic minerals form first, fall to the bottom, and keep silica-rich magma up on the top.
Types of igneous intrusions (4)
dikes (vertical), sills (horizontal), plutons (10m blobs), batholiths (100km, a lot of blobs in the same region)
When classifying igneous rock, consider three things:
Setting of cystallization, mineral composition, and texture.
Setting of cystalization
was it at the surface and how fast? Extrusive fast smaller crystals, Intrusive slow bigger crystals.
Phaneritic
visible crystals (intrusive)-- Granite
Aphanitic
crystals too small to see (extrusive)-- Rhyolite
Pegmatitic
visible crystals larger than 1cm
Porphyritic
both large crystals surrounded by smaller crystals
Glassy
solid mass of glass or tiny crystals surrounded by glass
Vesicular
porous, preserved gas bubbles
Fragmental
pyroclastics (material ejected from volcanoes).