Download A brief introduction to minerals, rocks and the rock cycle

Minerals
rock
A brief introduction to
minerals, rocks and the rock
cycle
Minerals: the building
blocks of rocks
Minerals
Definition of a mineral
-> To be considered a mineral, it must:
1. Occur naturally
2. Be inorganic
3. Be a solid
4. Possess an orderly internal structure
5. Have a definite chemical composition
Minerals and Rocks
minerals
mineral
collection of
one or more
minerals
A collection
of one or more
types of atoms
Minerals
Minerals: the building
blocks of rocks
Definition of a rock
-> different from that of a mineral. A rock:
1) is solid
2) contains a mixture of one or more minerals
3) May contain a non-mineral
4) occurs naturally as part of our planet
Minerals: the building
blocks of rocks
Minerals
The composition of minerals
Minerals
Rocks and minerals
z Some rocks composed entirely of one mineral
limestone (calcite)
z Most rocks have more than one kind of mineral
granite
Granite & constituent
minerals
z Some rocks contain non-mineral matter
coal (has organic debris)
obsidian (volcanic glassy rock -> not crystalline)
Minerals
Minerals
Over 4000 minerals: only few dozen are abundant, making
up most rocks of Earth’s crust
=> rock-forming minerals
Percent of elements by WEIGHT
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 crust
Minerals
The composition of minerals
Mineral groups
) The silicates
) Atomic structure
Silicon and Oxygen combine to form the most
common mineral group, the silicates.
Every silicate mineral contains the elements
silicon (Si)
oxygen (O)
112 known elements
Only 92 occur
naturally
1) Mineral groups
Nearly every silicate mineral combines with one or more
additional elements to achieve electrical neutrality
1) Mineral groups
) The silicates
The fundamental building block of all silicates is the
silicon-oxygen tetrahedron
Two different views of this arrangement:
The silicates
Remember:
Silicates are the most abundant mineral group with the silicate ion as basic
building block.
Light colored (crust, esp. continental crust)
Non-ferromagnesian (felsic) silicates
Feldspar
(Si, O, Al, K, Na, Ca) - mostly white or pink
50% of earth’s crust !
silicon atom
Quartz
(SiO
2
=silica)
- commonly transparent
silicate that consists only of silicon and oxygen
second most abundant in crust!
oxygen atoms
Muscovite
(Si, O, Al, K, H) – most common mica
cleavage in sheets, glass in Middle ages
sparkle in rocks, mica flakes in sand
Mineral groups
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
Pyroxene
Hornblende
Biotite
) Important Nonsilicate Minerals
Carbonates
(CO ) = carbonate ion
2-
3
Calcite (CaCO ) Forms limestone
Dolomite (CaMg(CO ) Calcium/magnesium
Carbonate, forms dolostone
3
3 2
Æ found together in sedimentary rock limestone,
Æ Main ingredient to cement, roads & building stones
– black to olive green, in basalt
– important component of earth’s mantle
– important component of continental rock
– iron rich mica, component of continental rock
Mineral groups
) Important Nonsilicate Minerals
Halides
Halite (NaCl)
-> common table salt
Sulfates
Gypsum (CaSO4-H2O)
-> calcium sulfate + water, main ingredient of
plaster & other building materials
Oxides
Hematite (Fe2O3)
-> mined for iron, steel
Ice (H2O)
-> solid form of water
Rocks
Three major types of
rock
Rock cycle and the three basic rock groups.
The rock cycle is an interaction between Climate and
Plate Tectonic System
From Press, Siever: Understanding Earth, 4th edition
From Tarbuck, Lutgens: Earth
Rocks
Igneous rocks
Extrusive-Intrusive
Extrusive
rocks are formed
at the surface
from lava, rapidly
cooling, small
crystals, finegrained texture.
Intrusive
rocks are
formed from
magma in
Earth’s crust,
slow cooling,
large crystals,
coarse texture.
Sedimentary rocks
Diagenesis
How to make a
sedimentary rock.
Any physical and chemical change that happens to the sediments
or the sedimentary rock
How to make a metamorphic rock.
Recall:
3 fundamental rock types
“metamorphism”
Rocks
Metamorphic rocks
Metamorphic rocks
form under 4 main
conditions:
Lit. “change form”
Transform:
Igneous
Sedimentary
into:
“process” Metamorphic
Metamorphic
Contact
occurs deep
TODAY: Plate Tectonics (Part I)
Ultra high P
Regional high P
High P, Low T
Earth’s layer by chemical properties
Earth’s layering by chemical
properties
Crust
• Intro: Chemical and physical
structure of Earth
1) The plate tectonic system
2) A theory is born
3) Early evidence for continental drift
Read Chapter 3!
Mantle
Core
Earth’s layer by physical properties
Lithosphere and
asthenosphere
Lithosphere:
Crust and uppermost mantle.
Broken into 12 plates.
Brittle, rigid. 1-100km
Asthenosphere:
Lower portion of upper
mantle, down to 660km
Soft, deformable, small
amount of melting.
3-18
1) The plate tectonic system
1) The plate tectonic system
Convection
Fig. 3.10
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.
PLATE
1) The plate
tectonic system
1) Overview
TECTONICS
Compare with Fig. 3-14