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Rocks and Minerals
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Minerals the building blocks of rocks
Mineral Characteristics natural inorganic solid definite composition crystal structure
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Mineral Formation 4 major processes by which minerals form:
1. Crystallization from magma- cooling magma causes minerals to crystallize
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2. Precipitation Minerals dissolve out of evaporated water; precipitated
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3. Pressure and Temperature
Change in pressure and temperature cause an existing mineral to recrystallize while still solid Muscovite Talc
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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
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Mineral Composition Minerals are grouped or classified based on their composition. There are 6 groups 1. Carbonates - contain carbon, oxygen, and one ore more metallic element
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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)
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3. Oxides - Minerals that contain oxygen and one or more other element(s)
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Gypsum 4. Sulfates and Sulfides - Minerals containing sulfur Pyrite
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5. Halides Halite -minerals containing halogen ions plus one or more other elements
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6. Native Elements Minerals that exist in a relatively pure form gold, silver, copper Gold crystal structure
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Mineral Properties Mineral PROPERTIES are used to identify minerals based on specific characteristics Luster Streak Color Specific Gravity Cleavage & Fracture Hardness Magnetism Fluoresence
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Streak color of a mineral in its powder form
Color often not a good property for Iding
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Luster how light is reflected from the surface of a mineral
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Cleavage- tendency to break along flat, even surfaces (mica) Fracture- uneven breakage (quartz)
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Specific Gravity- ratio of a mineral’s density to the density of water
mass (g) of dry sample mass lost in water Specific Gravity is a ratio…so Specific Gravity has no units
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Hardness- measure of resistance of a mineral being scratched
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Magnetism Magnetite Fluorescence Double Refraction Calcite Smell
Sulfur
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Rocks and The Rock Cycle
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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
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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
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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 rhyolite granite
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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
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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
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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
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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
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Classification of Major Igneous Rocks
Texture 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.
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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
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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
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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.
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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 salt limestone
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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
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Sedimentary rocks drop according to size; larger particles fall first followed by smaller particles
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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
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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
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Contact metamorphism Regional metamorphism
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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
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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
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Foliated NonFoliated slate marble schist gneiss
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The Rock Cycle
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Thinking about relationships among the major rock groups
The Rock Cycle Thinking about relationships among the major rock groups
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Major Rock Groups Igneous Sedimentary Metamorphic
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.
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Fig. 2.9 MAGMA
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IGNEOUS Crystallization MAGMA 46
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IGNEOUS Intrusive/Plutonic Crystallization MAGMA 47
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Extrusive/Volcanic IGNEOUS Intrusive/Plutonic Crystallization MAGMA 48
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Extrusive/Volcanic IGNEOUS Intrusive/Plutonic Uplift MAGMA Weathering
Crystallization Uplift MAGMA 49
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SEDIMENT SEDIMENT Extrusive/Volcanic IGNEOUS Intrusive/Plutonic Uplift
Weathering Extrusive/Volcanic IGNEOUS Intrusive/Plutonic Crystallization Uplift MAGMA 50
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SEDIMENT Extrusive/Volcanic IGNEOUS Intrusive/Plutonic SEDIMENTARY
Erosion SEDIMENT Weathering Transport Deposition Extrusive/Volcanic IGNEOUS Intrusive/Plutonic SEDIMENTARY Crystallization Uplift MAGMA 51
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SEDIMENT Extrusive/Volcanic IGNEOUS Intrusive/Plutonic SEDIMENTARY
Erosion SEDIMENT Weathering Transport Deposition Extrusive/Volcanic IGNEOUS Intrusive/Plutonic SEDIMENTARY Crystallization Uplift MAGMA 52
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SEDIMENT Extrusive/Volcanic IGNEOUS Intrusive/Plutonic SEDIMENTARY
Erosion SEDIMENT Weathering Transport Deposition Extrusive/Volcanic IGNEOUS Intrusive/Plutonic SEDIMENTARY Increased P&T METAMORPHIC Crystallization Burial Uplift MAGMA 53
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SEDIMENT Extrusive/Volcanic IGNEOUS Intrusive/Plutonic Add the
Erosion SEDIMENT Weathering Transport Deposition Extrusive/Volcanic IGNEOUS Intrusive/Plutonic Add the Shortcuts SEDIMENTARY Increased P&T METAMORPHIC Crystallization Melting Burial Uplift MAGMA 54
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SEDIMENT Extrusive/Volcanic IGNEOUS Intrusive/Plutonic SEDIMENTARY
Erosion SEDIMENT Weathering Transport Deposition Extrusive/Volcanic IGNEOUS Intrusive/Plutonic SEDIMENTARY Increased P&T METAMORPHIC Crystallization Melting Burial Uplift MAGMA 55
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SEDIMENT Extrusive/Volcanic IGNEOUS Intrusive/Plutonic SEDIMENTARY
Erosion SEDIMENT Weathering Transport Deposition Extrusive/Volcanic IGNEOUS Intrusive/Plutonic SEDIMENTARY Increased P&T METAMORPHIC Crystallization Melting Burial Uplift MAGMA 56
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In Conclusion… 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”.
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ROCK CYCLE The surface of the Earth is made of rock
ROCK is a collection of one or more minerals, mixed together into a solid substance
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Rock Cycle The Series of processes in which rock forms and changes from one type to another by geological processes.
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PROPERTIES OF ROCKS BOWEN’S REACTION SERIES: The pattern that shows how minerals form crystals when they cool based on their chemical make-up and melting point
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The Rock Cycle Melting & Intrusion Solidification of melt
Mountain Building Uplift & Exposure Weathering Erosion & Transport Deposition & Burial Metamorphism Fig 4.9
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Convergent Plate Boundary
The Rock Cycle Convergent Plate Boundary Subducting slab Mantle melting Bouyant rise of melt Fig 4.9
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Convergent Plate Boundary
The Rock Cycle Convergent Plate Boundary Solidification of melt Volcanic activity Extrusive rocks Intrusive rocks Fig 4.9
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