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Mineralsthe building blocks of rocks
Mineral Characteristics• natural • inorganic • solid• definite composition• crystal structure
Mineral Formation
4 major processes by which minerals form:1. Crystallization from magma- cooling magma causes minerals to crystallize
3. Pressure and Temperature
• Change in pressure and temperature cause an existing mineral to recrystallize while still solid
Muscovite
Talc
4. Hydrothermal Solutions
• A hot mixtures of water with substances dissolved in them. When they come in contact with existing minerals- a chemical reaction occurs forming a new mineral
Bornite
Mineral CompositionMinerals are grouped or classified based on
their composition. There are 6 groups
1. Carbonates - contain carbon, oxygen, and one ore more metallic element
2. Silicates- formed from silicon and
oxygen - elements combined to
form a silicon tetrahedron, 1 silicon atom and 4 oxygen atoms
- formed from cooling magma
- either near the surface (few crystals) or deep below surface (larger crystals)
6. Native ElementsMinerals that exist in a
relatively pure form
gold, silver, copper
Gold crystal structure
Mineral Properties
Mineral PROPERTIES are used to identify minerals based on specific characteristics
LusterStreakColor
Specific GravityCleavage & FractureHardnessMagnetismFluoresence
Specific Gravity- ratio of a mineral’s density to the density of water
Specific Gravity =
mass (g) of dry sample mass lost in water
Specific Gravity is a ratio…so Specific Gravity has no units
Rocks- any solid mass of mineral or mineral-like matter that occurs
naturally as part of our planet• There are 3 major type or families or rock:
– Igneous rocks– Sedimentary rocks– Metamorphic rocks
Igneous Rocks
• Magma- molten material underground
• Lava- magma that reaches the surface
• Igneous rocks are formed from magma that has cooled and hardened either beneath the surface or from a volcanic eruption
2 Ways to Form Igneous Rock• Intrusive Igneous
Rocks- form when magma hardens beneath Earth’s surface
• Magma intrudes into existing rocks
• Extrusive Igneous Rocks- form when lava hardens on the surface of the Earth
• Extruded onto the surface
granite
rhyolite
• Magma contains some gases, including water vapor- this make it less dense, so it rises
• As magma rises, it cools and forms crystals
• The longer the cooling time the larger the crystals
Classification of Igneous Rocks Igneous rocks are classified by texture
and composition• Texture refers to the appearance of an
igneous rock (size, shape, arrangement of crystals)
• Composition refers to the proportions of light and dark minerals in the rock
• Coarse- grained Texture- form as a result of slow cooling, ions can move = large crystal size
• Fine-grained Texture- form as a result of quick cooling time, ions lose motion= small crystal size
• Glassy Texture- form from lava that cools rapidly, ions don’t have time to arrange = glassy texture
• Porphyritic Texture- rocks with different size minerals that form from varying cooling rates
• Felsic Composition- contain mainly quartz and feldspar, some with biotite mica and amphibole. Make up major rocks of continental crust
• Mafic Composition- contain mainly dark colored minerals and feldspar, along with Mg and Fe. Darker and denser than granitic composition
Classification of Major Igneous RocksTexture is crossed with composition to classify igneous rocks. For example, granite has a coarse texture due to slow cooling and larger crystals, and a light color from the light colored quartz and feldspar minerals used to form it.
Sedimentary Rocks- formed from compacted and cemented sediments
• Weathering physically and chemically breaks rocks into small pieces called sediments
• Sediments are moved by wind, water, ice, and gravity• Eventually, they are dropped and form layers that are cemented together
Weathering, Erosion, and Deposition
• Weathering breaks rocks down
• Erosion involves weather and the removal of rock
• Deposition is the dropping of sediments • Sediments are
deposited according to size
Compaction and Cementation• Compaction is the
process that squeezes the water out of the sediments. It is caused by the weight of the sediments.
• Cementation takes place when dissolved minerals are deposited in the tiny spaces among the sediments.
• Cementing holds the sediments together.
Classification of Sedimentary Rocks• Clastic Sedimentary
Rocks are formed from weathered bits of rocks and minerals
• Organic Sedimentary Rocks are formed from living materials
• Chemical Sedimentary Rocks are formed when dissolved minerals precipitate from water solution
rock saltlimestone
• Sedimentary rocks hold many clues to the Earth’s history
• Layers of sediments are records of geologic events on Earth
• Fossils are unique to sedimentary rocks
Metamorphic Rocks- form when existing rocks undergo change through
heat and pressure• Metamorphism means
to change• Most metamorphic
changes occur at high temperatures and pressure
• These occur deep below the Earth’s surface and extend into the mantle
Forms of Metamorphism
• Contact Metamorphism- forms when magma intrudes into existing rock
• Changes in rocks are minor
• Regional Metamorphism- formed during mountain building process that occur over a large area
• Major changes to rocks
Agents of Metamorphism
• Heat- causes existing minerals to recrystallize or new minerals to form
• Pressure- causes the spaces between mineral grains to close= more compact rock= greater density
Classification of Metamorphic Rocks- based on texture and composition
• Foliated Metamorphic Rocks- form when minerals recrystallize at right angles to the direction of force
• Causes a layered or banded appearance
• Nonfoliated Metamorphic Rocks- no banded texture
• Most contain only one mineral
Major Rock Groups• Igneous
– Formed from a melt (molten rock)– Plutonic (intrusive):slow cooling and crystallization– Volcanic (extrusion): quick cooling at the surface
•Sedimentary–Formed at the Earth’s surface
–Clastic (Mineral Fragments or grains, clays)
–Chemical (crystalline chemical/biochemical precipitates)
–Organic (made from living material: shells, plants)
•Metamorphic–Changed by pressure, heat and fluids.
50
MAGMA
SEDIMENT
Uplift
Crystallization
Weathering SEDIMENT
Extrusive/Volcanic
IGNEOUS
Intrusive/Plutonic
51
MAGMA
SEDIMENT
SEDIMENTARY
Uplift
Crystallization
WeatheringErosion
Transport
DepositionExtrusive/Volcanic
IGNEOUS
Intrusive/Plutonic
52
MAGMA
SEDIMENT
SEDIMENTARY
Uplift
Crystallization
WeatheringErosion
Transport
DepositionExtrusive/Volcanic
IGNEOUS
Intrusive/Plutonic
53
MAGMA
SEDIMENT
SEDIMENTARY
METAMORPHIC
UpliftBurial
Increased P&T
Crystallization
WeatheringErosion
Transport
DepositionExtrusive/Volcanic
IGNEOUS
Intrusive/Plutonic
54
MAGMA
SEDIMENT
SEDIMENTARY
METAMORPHIC
UpliftBurial
Increased P&T
MeltingCrystallization
WeatheringErosion
Transport
DepositionAdd the
Shortcuts
Extrusive/Volcanic
IGNEOUS
Intrusive/Plutonic
55
MAGMA
SEDIMENT
SEDIMENTARY
METAMORPHIC
UpliftBurial
Increased P&T
MeltingCrystallization
WeatheringErosion
Transport
DepositionExtrusive/Volcanic
IGNEOUS
Intrusive/Plutonic
56
MAGMA
SEDIMENT
SEDIMENTARY
METAMORPHIC
UpliftBurial
Increased P&T
MeltingCrystallization
WeatheringErosion
Transport
DepositionExtrusive/Volcanic
IGNEOUS
Intrusive/Plutonic
• The rock cycle demonstrates the relationships among the three major rock groups
• It is powered by the interior heat of the Earth
• As well as earth’s momentum and…
• The energy from the sun
• It involves processes on the Earth’s surface as well as the Earth’s interior
• It connects the “hydrologic cycle” with the “tectonic cycle”.
In Conclusion…
ROCK CYCLEROCK CYCLE
• The surface of the The surface of the Earth is made of Earth is made of rockrock
• ROCK ROCK is a collection is a collection of one or more of one or more minerals, mixed minerals, mixed together into a solid together into a solid substancesubstance
Rock CycleRock Cycle
• The Series of processes in which rock forms The Series of processes in which rock forms and changes from one type to another by and changes from one type to another by geological processes.geological processes.
PROPERTIES OF ROCKSPROPERTIES OF ROCKS
• BOWEN’S BOWEN’S REACTION SERIESREACTION SERIES: : The pattern that shows The pattern that shows how minerals form how minerals form crystals when they crystals when they cool based on their cool based on their chemical make-up and chemical make-up and melting pointmelting point
The Rock The Rock CycleCycle
-Melting & Intrusion-Solidification of melt-Mountain Building-Uplift & Exposure-Weathering-Erosion & Transport-Deposition & Burial-Metamorphism-Melting & Intrusion
Fig 4.9
The Rock CycleThe Rock Cycle
Fig 4.9
Convergent Plate Boundary-Subducting
slab-Mantle melting-Bouyant rise
of melt