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