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A brief introduction to A brief introduction to minerals, rocks and the rock minerals, rocks and the rock cyclecycle
rockrock
collection ofone or moreminerals
mineral
A collectionof one or moretypes of atoms
minerals
Minerals and RocksMinerals and RocksMinerals
-> To be considered a mineral, it must:
1. Occur naturally
Minerals blocks of rocksMinerals: the building
2. Be inorganic3. Be a solid
5. Have a definite chemical composition
4. Possess an orderly internal structure
Definition of a mineral Definition of a rock
-> different from that of a mineral. A rock:
1) is solid
Minerals blocks of rocksMinerals: the building
4) occurs naturally as part of our planet
2) contains a mixture of one or more minerals
3) May contain a non-mineral
Rocks and minerals
Some rocks composed entirely of one minerallimestone (calcite)
Minerals blocks of rocksMinerals: the building
Most rocks have more than one kind of mineralgranite
Some rocks contain non-mineral mattercoal (has organic debris)obsidian (volcanic glassy rock -> not crystalline)
Granite & constituent minerals
The composition of mineralsThe composition of mineralsMinerals
Minerals
Over 4000 minerals: only few dozen are abundant, making up most rocks of Earth’s crust
=> rock-forming minerals
Only 8 elements make up most of crust’s minerals & represent over 98% of the continental crust
The two most abundant elements:
Silicon (Si)Oxygen (O)
Average composition of the continental crustAverage composition of the continental crust
Percent of elements by WEIGHT
Minerals
112 known elements
Only 92 occur naturally
The composition of mineralsThe composition of mineralsMinerals
Atomic structure The silicates
Every silicate mineral contains the elements
silicon (Si)oxygen (O)
Nearly every silicate mineral combines with one or more additional elements to achieve electrical neutrality
Mineral groups
Silicon and Oxygen combine to form the most common mineral group, the silicates.
The silicates
The fundamental building block of all silicates is the
silicon-oxygen tetrahedron
Two different views of this arrangement:Two different views of this arrangement:
silicon atom
oxygen atoms
1) Mineral groups
Light colored (crust, esp. continental crust)Non-ferromagnesian (felsic) silicates
Feldspar (Si, O, Al, K, Na, Ca) - mostly white or pink50% of earth’s crust !
Quartz (SiO2 =silica) - commonly transparentsilicate that consists only of silicon and oxygensecond most abundant in crust!
Muscovite (Si, O, Al, K, H) – most common micacleavage in sheets, glass in Middle agessparkle in rocks, mica flakes in sand
1) Mineral groups
The silicates
Remember:Silicates are the most abundant mineral group with the silicate ion as basic building block.
Dark colored (mantle, basalt, continental crust)Ferromagnesian (mafic) are dark silicates, contain ions of iron
and/or magnesium)
Olivine – black to olive green, in basaltPyroxene – important component of earth’s mantleHornblende – important component of continental rockBiotite – iron rich mica, component of continental rock
Mineral groups
The silicates
Remember:Silicates are the most abundant mineral group with the silicate ion as basic building block.
Important Nonsilicate Minerals
Carbonates (CO3 2- ) = carbonate ion
Calcite (CaCO3)Dolomite (CaMg(CO3)2
found together in sedimentary rock limestone, Main ingredient to cement, roads & building stones
Mineral groups
Calcium/magnesiumCarbonate, forms dolostone
Forms limestone
HalidesHalite (NaCl)-> common table salt
SulfatesGypsum (CaSO4-H2O)-> calcium sulfate + water, main ingredient of
plaster & other building materialsOxides
Hematite (Fe2O3)-> mined for iron, steel
Mineral groups
Important Nonsilicate Minerals
Ice (H2O)-> solid form of water
RocksRocks Three major types of Three major types of rockrock
Rock cycle and the three basic rock groups.
From Tarbuck, Lutgens: EarthFrom Press, Siever: Understanding Earth, 4th edition
The rock cycle is an interaction between Climate and Plate Tectonic System
RocksRocksIgneous rocks
Extrusive rocks are formed at the surface from lava, rapidly cooling, small crystals, fine-grained texture.
Intrusiverocks are formed from magma in Earth’s crust, slow cooling, large crystals, coarse texture.
Extrusive-Intrusive Sedimentary rocks
DiagenesisAny physical and chemical change that happens to the sediments or the sedimentary rock
How to make a How to make a sedimentary rock.sedimentary rock.
“metamorphism” Lit. “change form”
Transform:
Igneous
Sedimentary
Metamorphic
Metamorphicinto:
“process”
occurs deep
Recall: 3 fundamental rock typesHow to make a metamorphic rock.How to make a metamorphic rock.
Metamorphic rocks
RocksRocks Metamorphic rocks form under 4 main conditions:
Contact Ultra high P Regional high P High P, Low T
• Intro: Chemical and physical structure of Earth
1) The plate tectonic system2) A theory is born3) Early evidence for continental drift
TODAY: Plate Tectonics (Part I)
Read Chapter 3!
EarthEarth’’s layering by chemical s layering by chemical propertiesproperties
Crust
Mantle
Core
Earth’s layer by chemical properties
Lithosphere andLithosphere andasthenosphereasthenosphere
Lithosphere:Crust and uppermost mantle.Broken into 12 plates.Brittle, rigid. 1-100km
Asthenosphere:Lower portion of upper mantle, down to 660kmSoft, deformable, small amount of melting.
3-18
Earth’s layer by physical properties
1) The plate tectonic system1) The plate tectonic system
1. The lithosphere is the outer rigid shell of earth, about 100km thick. It is broken into a dozen large plates that move on the plastic asthenosphere (lower part of the upper mantle)
2. The lithosphere is created at mid-ocean spreading centers and subducts when converging with another plate.
3. The driving force of this movement are convection currents in the asthenosphere.
Fig. 3.10
1) The plate tectonic system1) The plate tectonic system
Convection
PLATEPLATETECTONICSTECTONICS 1) Overview1) Overview1) The plate tectonic system1) The plate tectonic system
Compare with Fig. 3-14