MINERALS AND ROCKS
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Atomic structure
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Isotopes
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Atoms and molecules
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Chemical reactions => Bonding
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Ionic bonding (give & take electrons)
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Covalent bonding (share electrons)
Mineral: definition
Crystal Lattices => 3 dimensional order
Ion substitutions => stability of min. species
Physical properties of minerals
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hardness
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density
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fracture
-
cleavage
Minerals require specific conditions for
their formation. The appearance of a given mineral under conditions other
than the ones of its formation can shed light on the processes that brought
the mineral to its present environment.
MINERAL GROUPS
Silicates (rock forming minerals). E.g. quartz &
feldspars
Carbonates and sulfates (low temperature). E.g. calcite
& gypsum
ROCKS
Classified by texture and composition
IGNEOUS ROCKS: solidification of magma
|
FELSIC (Feldspar and
silica rich)
|
MAFIC (Magnesium and
iron rich)
|
|
light colored
|
dark colored
|
|
low density
|
high density
|
|
granite
|
basalt or gabbro
|
Coarse grained => slow cooling => intrusive
or plutonic
Intrusions
sills
dikes
Fine grained => fast cooling => extrusive or
volcanic
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lava
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tuff
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fissure (flood basalt)
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pillow basalt
SEDIMENTARY ROCKS
Origin:
-
fragments of preexisting rocks (clasts)
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crystals precipitated out of water
-
skeletons of living organisms
Sediment production:
FRAGMENTAL OR DETRITAL OR CLASTIC ROCKS
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weathering (break down).
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Felspar => clay
-
Quartz => resistant
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Ferromagnesian=> iron oxide (fast weathering)
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erosion (removal)
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deposition => SEDIMENT
Lithification (compaction & /or cementation) => sedimentary
rock
Siliciclastic sedimentary rocks
Mudstones (from mud sediment)
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clay => shale (fissile)
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silt => siltstone (less fissile)
Sand => sandstone (cement)
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quartz sandstone
-
arkose
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graywacke
Common cements: calcite, iron oxides (red beds)
Gravel => conglomerate
breccia
Sorting:
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well sorted (similar sizes)
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poorly sorted (mixed sizes)
CHEMICAL AND BIOGENIC SEDIMENTARY ROCKS
Inorganically precipitated or precipitated by organisms
as part of their structure.
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Inorganic precipitation
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gypsum & anhydrite
soluble
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halite
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Banded Iron Formations
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Inorganic or biogenic
Chert
Carbonatic ROCKS
Limestones calcite
dolomite
aragonite (unstable)
oolitesCarbonatic rocks indicate tropical environments
SEDIMENTARY STRUCTURES
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graded bedding
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ripple marks
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cross-bedding or cross-stratification
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mudcracks
METAMORPHIC ROCKS
No melting
Metamorphic grade: indicates temperature achieved during
the metamorphic event
Regional metamorphism (P) foliation slate => green
schist => schist => gneiss
marbles and quartzites = non foliated
Contact metamorphism (T ) fine grained rocks
grade decreases away from intrusive
Hydrothermal metamorphism mostly at MOR (midoceanic
ridges)
Burial metamorphism => coal (peat => lignite =>
anthracite) => graphite ( a metamorphic mineral)
At the upper limit of metamorphismn rocks are "close
to melting" and resemble igneous rocks, therefore, they are difficult to
distinguish from them
GEOL
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GEOL
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