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37 Cards in this Set
- Front
- Back
Mineral definition
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a naturally occurring inorganic solid with a specific chemical composition and a specific regular atomic architecture
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Halite cleavage and composition
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perfect in 3 directions, makes cubes.
Atomic structure looks like a cube. |
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Graphite structure and bonds
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series of 2-D sheets stacked on each other.
Each sheet has strong carbon bonds, but between each sheet are very weak bonds. Makes it easy to flake off. |
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Diamond structure and bonds
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carbon atoms in diamond make a 3-D network of carbon tetrahedra (3-D triangles) sharing corners.
Every single bond is VERY strong Hardest natural solid |
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Why do some crystalline solids display external perfect shape of crystals whereas others have extremely irregular shapes?
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The shape can be determined by the other minerals crowded around it.
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What is the most important mineral group on Earth and why does this make sense?
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Silicates (90% of continental crust and higher in oceanic and mantle)
Made of 4 oxygen atoms around 1 silicon. Oxygen is ready to bond with many things. |
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Silica Tetrahedron
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oxygen atoms define 4 corners of a 3-D object (tetrahedron). Each side is an equilateral triangle.
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Pluton
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when an irregular blob of magma freezes underground. Plutons are 10s of m to 10s of km across.
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Batholith
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intrusion of many plutons create a vast igneous body of 100s of km long and 100km wide
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Dikes
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a tabular (sheet-like) intrusion that CUTS ACROSS regional layering.
Show rifting (stretching) |
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Sills
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tabular intrusions that run parallel to layering
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Which part of a volcanic system do plutons and batholiths represent?Which indicates a long lived subduction zone?
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Magma chambers (in fossil form).
Batholiths |
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Do igneous rocks fall into distinct clusters based on chemical or mineralogical composition, or do they fall into a continuum?
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They fall into a continuous spectrum of compositions. Evolving compositions.
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Mafic vs. Felsic melting temperatures
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Mafic are dark and dominated by minerals that melt @ high temps.
Felsic are light and dominated by minerals that melt @ low temps. |
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Why is there a range of crystallization temperatures?
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Variations in mineral and magma compositions and pressure experienced(depth).
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Geothermal Gradient (geotherm)
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The increase in temperature with depth in the Earth.
Slows after 100km. |
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Is the mantle made of mafic or felsic minerals? Which rock dominates?
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Periodite is an ultramafic rock. (Green)
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What physically has to happen to a rock to produce decompression melting?
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Asthenosphere comes closer to surface. Rock rises.
Occurs at ocean spreading centers & continental rifts. |
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Decompression melting definition
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occurs when rocks rise, pressure drops, and the solidus is crossed.
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What happens when water is added to hot, pressurized periodotite?
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It lowers the solidus of some of the minerals causing it to melt faster.
The water percolates upward between the mineral grains. |
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Which types of boundaries cause decompression melting?
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Convergent and divergent.
Ridges and rifts. |
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Which type of boundaries cause hydration melting?
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Convergent.
Subduction zones. |
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Mantle Plumes
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Rising columns of hot rock below hot spot volcanoes. When it reaches lithosphere, the flow is deflected to sides.
caused by crystallization of iron in outer core. mantle gets hot enough to flow and sends up solid mantle. 150km below surface (litho.), partial melting produces volcanic magma. |
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Color
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results from the way a mineral interacts w/ light. What we see represents the wavelength the mineral doesn't absorb.
Not reliable |
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Streak
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color of the powder produced by pulverizing the mineral.
Fairly reliable |
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Luster
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way a mineral surface scatters light.Compare it to a familiar substance.
ex:metal,silky,glassy,etc. |
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Hardness
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measure of the relative ability of a mineral to resist scratching, and therefore represents the resistance of bonds from being broken.
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Cleavage
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when a mineral breaks to form distinct planar surfaces that have a specific orientation in relation the the crystal structure.
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Conchoidal fractures
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smoothly curving, clamshell shaped surfaces. Typical in quartz & glass.
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Compare mafic and intermediate/felsic lavas in terms of density and viscosity
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Mafic is denser but less viscous
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Viscosity
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resistance to flow
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Why do magmas rise?
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A rock expands as it melts, therefore it is less dense than the surrounding and it rises. Buoyancy
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What determines how far up a large blob of magma will rise?
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If magma is too dense it will rise until the density matches the surrounding rock.
Can become too viscous to force their way through fractures. |
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Where does all partial melting start? What is the composition of this layer and the melts it produces?
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All melting starts in mantle.
A partial melt of an ultramafic mantle periodotite is a MAFIC melt that crystallizes to form a gabbro or basalt. |
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What is heat transfer and assimilation?
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Mafic magmas cause heat transfer by directly melting felsic materals which then release water and stimulate more melting.
Assimilation is when original magma incorporates some felsic melt from heat transfer melting. |
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How does Fractional crystallization work?
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As magma cools, minerals begin to crystallizae. Mafic settle first and remove themselves from the magma creating intermediate magma.
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Why does volcanism on continental crust produce many compositions, but ocean ridges produce only basalts?
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cont. crust is rich in felsic rock for assimilation
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