lecture5_igneous - Lecture 5: Igneous Rocks: Solids From...

1. How do igneous rocks differ from
one another ?
2. How do magmas form ?
Lecture 5: Igneous Rocks:
Solids From Melts
6. Igneous rocks in the western US

Last time
• Rock cycle
• Local geology and geological history
Logistics:
• Labs this week.
• Ask questions anytime
• First midterm Oct 6 – stay tuned for details
Coming up: weathering sedimentary and rocks,
metamorphic rocks, volcanism
MAKE SURE YOU SIGN UP FOR A FIELD TRIP

Why?
1. Understand processes that form crust (differentiate Earth)
2. Decipher compositional and thermal history of Earth
3. Assess volcanic hazard
4. Geothermal and mineral resources
Remember . . . Rocks are the history books of Earth

Elemental associations
Periodic properties of the elements explain many geochemical patterns.
For example:
1. Earth is a “differentiated body” with a core, mantle and crust that are
chemically distinct. Why?
2. Why are K, Ca and Sr are concentrated in the crust and not in the core?
3. Why is Copper almost always found in sulfide ores rather than in
oxides?
In early 1900s, Victor Goldschmidt proposed a practical scheme for grouping
elements according to their occurrence in nature.
He found that most elements have greater affinity for one of three kinds of
minerals: silicates , sulfides , and metals

I II III IV V VI VII VIII
1 2
H He
3 4 5 6 7 8 10
Li Be B C N O Ne
11 12 13 14 15 16 18
Na Mg Al Si P S Ar
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 36
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Kr
37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 54
Rb Sr Y Zr Nb Mo (Tc) Ru Rh Pd Ag Cd In Sn Sb Te Xe
55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86
Cs Ba
La*
Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
87 88 89
Fr Ra Ac**
57 58 59 60 61 62 63 64 65 66 67 68 69 70 71
*Lanthanides La Ce Pr Nd (Pm) Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
89 90 91 92 93 94
**Actinides Ac Th Pa U Np Pu
Os Siderophile Cu Chalcophile N Atmophile
The Periodic Table of the Elements:
Lithophile = elements that readily form compounds with oxygen; elements concentrated in earth’s
crust; silicates, oxides and other “stony” minerals (Na, K, Si, Al, Ti, Mg, Ca)
Chalcophile = elements that most easily form sulfides; chalcos = copper
Siderophile = elements that form metallic alloys rather than stoichiometric compounds; sideros =
iron; weak affinity for oxygen and sulfur
Atmophile = elements commonly found as gases
à General geochemical behavior

I II III IV V VI VII VIII
1 2
H He
3 4 5 6 7 8 9 10
Li Be B C N O F Ne
11 12 13 14 15 16 17 18
Na Mg Al Si P S Cl Ar
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
37 38 39 40 41 42 44 45 46 47 48 49 50 51 52 53 54
Rb Sr Y Zr Nb Mo Ru Rh Pd Ag Cd In Sn Sb Te I Xe
55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86
Cs Ba
La*
Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
87 88 89
Fr Ra Ac**
57 58 59 60 61 62 63 64 65 66 67 68 69 70 71
*Lanthanides La Ce Pr Nd (Pm) Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
89 90 91 92 93 94
**Actinides Ac Th Pa U Np Pu
Os Siderophile Rb Lithophile N Atmophile
The Periodic Table of the Elements:
Lithophile = elements that readily form compounds with oxygen; elements concentrated in earth’s