minerals & rox

EESC 2200The Solid Earth System

Minerals & Rox22 Sep 08

IsostasyContinental Tectonics

Homework 1:Due Today

ES101--Lect 5

Minerals

rock forming

gems & ores

ES101--Lect 5

Plate Tectonics can produce all

rock classes:

• igneous

• sedimentary

• metamorphic

ES101--Lect 5

Earth is made of rocks

Each rock is made up of grainsminerals

ES101--Lect 5

Feldspar

Quartz

Mica

ES101--Lect 5

basaltfrom Hawaiiwitholivine

basalt

ES101--Lect 5photomicrograph of basalt

Feld-spar

Oli-vine

(x-polars)

ES101--Lect 5

What Are Minerals?

Naturally occurring,

solid substances,

with a specific chemical compositions

and crystal structure.

Structureof anAtom

Ionic Radiiof some

geologicallyimportant ions

Carbon Atoms in Diamondand Graphite

Graphite

Diamond

Bonding effectson

Physical Properties

3.5 g/cc

2.1 g/cc

ES101--Lect 5

Graphite

Diamond

0 1000 2000

50

100

150

Temperature (°C)

Depth(km)

One Mineral or Two?

ES101--Lect 5

Graphite

Diamond

0 1000 2000

50

100

150

Temperature (°C)

Depth(km)

Polymorph! same chemical comp'n, different shape

Galena (PbS)

Ionic Bonding

ES101--Lect 5

H

Li

Na

Fr

Be

Mg

Ca

Ra

Sc

Y

Ac

Ti

Zr

Hf

V

Nb

Ta

Cr

Mo

W

Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

He

Ne

Ar

Xe

Rn

F

Cl

I

At

O

S

Te

Po

N

P

Sb

Bi

C

Si

Sn

B

Al

In

Tl

Cd

Hg

Ag

Au

Pd

Pt

Rh

Ir

Ru

Os

Tc

Re

Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Pa

K

Rb

Cs

Sr

Ba La Pb

Th U

Periodic Table of the Elements

common in crust and mantle crust

ES101--Lect 5

ChartMg Si

Ca "rest"

Fe Al

Elemental Composition of the Earth(no core)

by weight

Si - SiliconMg - MagnesiumFe - IronAl - AluminumCa - Calcium

O - Oxygen not shown

ES101--Lect 5

Si

AlFe

CaMg

Na K "rest"

Abundance of Elements

Crust Mantle

ChartMg Si

Ca "rest"

Fe AlNa - sodiumK - potassium O - Oxygen not shown

ES101--Lect 5

The Silicates

Silicate Tetrahedron (SiO4)4-

Si4+

O2-

Basic Element:

ES101--Lect 5

=

Building block of the EarthVery strong Si-O bonds

ES101--Lect 5

Form Minerals By:1. Combining w/ Other Cations

most important: Olivine

4-

2+2+

Mg2SiO4

ES 101-Lect 6Olivine

ES 101-Lect 6

Olivine

• Main mineral in upper mantle

• In igneous rox in crust

• Dense

• Green

• Gem = peridot

(Mg,Fe)2SiO4

ES 101-Lect 6

Single Tetrahedron

Double:

Single Chain

Double Chain

Sheet 3D!

ES 101-Lect 6

Most Important Silicate Minerals

"rock-forming"

• Olivine• Pyroxene• Feldspar• Quartz• Mica• Amphibole

ES 101-Lect 6

Single Tetrahedron

Double:

Single Chain

Double Chain

Sheet 3D!

ES 101-Lect 6

Pyroxenes

e.g., CaMgSi2O6 = diopside

Fe, Mg, Ca, Mn, Na, Al

Single Chain silicate

Common in mantle, oceanic crust rocks

ES 101-Lect 6Diopside, Pyroxene

ES 101-Lect 6

Main mantle rock: Peridotite

• Mostly Olivine

• some pyroxene

(green)

(black, green)

ES 101-Lect 6

Si

AlFe

CaMg

Na K "rest"

The Crust:Need minerals that hold

Al - AluminumCa - CalciumNa - SodiumK - Potassium...more Si

K+ Fe2+

ES 101-Lect 6

Single Tetrahedron

Double:

Single Chain

Double Chain

Sheet3D!

ES 101-Lect 6

Feldspars

KAlSi3O8

CaAl2Si2O8NaAlSi3O8

• Makes 60% of crust

Holdslight largecations

plagioclase

"K-spar"

3D!

ES 101-Lect 6Orthoclase K-Feldspar

ES 101-Lect 6

-- No cations ("pure")

Common in continental crust

SiO2

Pure silica: Quartz

3D!

ES 101-Lect 6Quartz

ES 101-Lect 6

Single Tetrahedron

Double:

Single Chain

Double Chain

Sheet 3D!

ES 101-Lect 6

Just Add Water!• Silicates react, form more open structures

Pyroxenes + H2O -> Amphiboles

+

H2Odouble chain

ES 101-Lect 6Hornblende, Amphibole

ES 101-Lect 6

Others + H2O -> Sheet Silicates

clays, micas, serpentines

Just Add Water!

sheet

ES 101-Lect 6

Big gaps betweensheets:• Very weak bonds• Holds Water

• Makes "platy" minerals Cleavage

Micas sheet

ES 101-Lect 6

• Absorbant clays

• Common upper crust, weathering

Clayssheet

Clay minerals:

formed fromsheets of silica tetrahedra

ES 101-Lect 6

Two General Forms:

Serpentines: > 95% of all asbestos

Amphiboles: "blue asbestos"

Asbestos sheetvs.

double

ES 101-Lect 6Serpentine

ES 101-Lect 6

Theme:

Molecular structure affects

mineral structure

ES 101-Lect 6

Silicatetrahedra

Dense

LightIons

Mg2+

Fe2+

Ca2+

Al3+

Na1+

K1+

man

tle

crus

t

3D!

ES101--Lect 5

Feldspar

Quartz

Mica

ES 101-Lect 6

Major Rock-forming Minerals-> Silicates: SiO2 based

• 95% of crust, upper Mantle SiO

OO

O

ES 101-Lect 6

Major Rock-forming Minerals-> Silicates: SiO2 based

• 95% of crust, upper Mantle

-> Carbonates: CO3 based• Common near-surface (limestones,...) -- Major Carbon store

C

O

O

SiO

OO

O

ES 101-Lect 6

Major Rock-forming Minerals-> Silicates: SiO2 based

• 95% of crust, upper Mantle

-> Carbonates: CO3 based• Common near-surface (limestones,...) -- Major Carbon store

-> OthersOxides (various settings)Sulfides, Sulfates (S = sulfur)

C

O

O

SiO

OO

O

Rock Types• All rocks are organized according to genesis (igneous,

sedimentary or metamorphic), composition and texture• Igneous

– Mafic (silica poor) to felsic (silica rich)– Aphanitic (finely crystalline) to phaneritic (coarsely crystalline)

• Sedimentary– Clastic– Chemical and/or biochemical

• Metamorphic– Protolith (what was it before being heated and/or deformed?)– Contact (heating) vs. regional metamorphism (heating and

deforming)