Quiz 9 (9:30-9:35 AM)
UNIVERSITY OF SOUTH ALABAMA
GY 111: Physical Geology
Lecture 26
Regional Metamorphism
Last Time
Metamorphism 1
1. Indonesian Earthquake (finish last lecture)
2.Agents of Metamorphism
3. Types of metamorphism
4. Hydrothermal fluids (webnotes only)
Web notes: 25
Largest Earthquakes in
the World Since 1900
Location
Date UTC
Magnitude
Coordinates
Reference
1.
Chile
1960 05 22
9.5
-38.24
-73.05
Kanamori, 1977
2.
Prince William Sound, Alaska
1964 03 28
9.2
61.02
-147.65
Kanamori, 1977
3.
West Coast of Northern Sumatra
2004 12 26
9.1
3.30
95.78
PDE
4.
Kamchatka
1952 11 04
9.0
52.76
160.06
Kanamori, 1977
5.
Off the Coast of Ecuador
1906 01 31
8.8
1.0
-81.5
Kanamori, 1977
6.
Rat Islands, Alaska
1965 02 04
8.7
51.21
178.50
Kanamori, 1977
7.
Northern Sumatra, Indonesia
2005 03 28
8.6
2.08
97.01
PDE
8.
Andreanof Islands, Alaska
1957 03 09
8.6
51.56
-175.39
Johnson, 1994
9.
Assam - Tibet
1950 08 15
8.6
28.5
96.5
Kanamori, 1977
10.
Kuril Islands
1963 10 13
8.5
44.9
149.6
Kanamori, 1977
11.
Banda Sea, Indonesia
1938 02 01
8.5
-5.05
131.62
Kanamori, 1977
12.
Kamchatka
1923 02 03
8.5
54.0
161.0
Kanamori, 1988
Updated 2006 May 02
Source: http://earthquake.usgs.gov/regional/world/10_largest_world.php
December 26, 2004
Tsunami
SEISMOGRAPHIC NETWORK
The Rock Cycle
Igneous
Loop
Metamorphic
Loop
Sedimentary
Loop
Metamorphism
Metamorphism: a solid state change (recrystallization)
of a parent rock by physical “agents” using operating
deep within the interior of the Earth.
Shale (Parent Rock)
Slate (Metamorphic Rock)
Metamorphism
Agents of Metamorphism
1. Heat (25˚C to 800˚C; up to
the point of melting)
Geothermal Gradient: the increase in
ambient temperature with depth.
15 to 30°C/km under stable continental
rocks
200°C/km under mid oceanic ridges
http://www.geo.umn.edu/courses/1001/Summer_Session/MeltingVsDepth.jpg
Metamorphism
Agents of Metamorphism
1. Heat (25˚C to 800˚C; up to
the point of melting)
2. Pressure (1 bar to 12 kbars)
1 bar = 1 atmosphere
12 kbar = 12,000 atmospheres
http://www.geol.ucsb.edu/faculty/hacker/geo102C/lectures/hydrostat.jpg
Metamorphism
Agents of Metamorphism
1. Heat (25˚C to 800˚C; up to
the point of melting)
2. Pressure (1 bar to 12 kbars)
3. Chemically active fluids
(AKA hot water)
http://news-service.stanford.edu/news/2005
Types of Metamorphism
Regional (heat and pressure)
Associated with convergent
plate boundaries
1) Isobars
2) Isotherms
3) Isograds (upcoming lecture)
Types of Metamorphism
 Contact (heat only)
Metamorphic aureoles
Types of Metamorphism
 Cataclastic (pressure only)
Mylonites
Shear zones
http://www.cliffshade.com/colorado/homestake/hsz01.jpg
Today’s Agenda
Regional Metamorphism
A) Foliated rocks
B) Non-foliated rocks
Web notes: 26
Regional Metamorphism
Involves both heat
and pressure
Regional Metamorphism
Pressure causes certain minerals (clays) to deform and
change their orientation in the original parent rock.
e.g., shale (sedimentary)
Kaolinite (a clay)
Regional Metamorphism
The most stable configuration for platy minerals like
clays and micas is perpendicular to the stress direction
Regional Metamorphism
The most stable configuration for platy minerals like
clays and micas is perpendicular to the stress direction
Regional Metamorphism
Foliated Rocks
This is a low grade form of metamorphism and does not
impose great changes in the rock (e.g., color stays the same)
e.g., slate (metamorphic)
Foliated Rocks
But it can develop rock cleavage
Foliated Rocks
As metamorphic grade increases (especially pressure),
minerals begin to alter and new minerals start to grow
(e.g., Kaolinite is unstable at all but Low P/T and turns into micas)
Low
Shale
Medium
slate
phyllite
Foliated Rocks
Higher P/T causes minerals to grow large enough to be
visible. Metamorphic minerals include: garnet, talc,
graphite, chlorite, kyanite, staurolite etc.
Low
Shale
Medium
slate
phyllite
Med-High
schist
Foliated Rocks
Higher P/T causes minerals to grow large enough to be
visible. The highest pressure can cause mineral
separation (distinct bands e.g., quartz, biotite, feldspars).
Low
Medium
slate
phyllite
Med-High
schist
High
gneiss
Foliated Rocks
Terminology Hell:
Rock cleavage, foliation, schistosity, gneissosity (sp?)
Low
Medium
slate
phyllite
Med-High
schist
High
gneiss
Foliated Rocks
Slate
Foliated Rocks
Phyllite
Foliated Rocks
Garnet-Mica schist
Foliated Rocks
Kyanite schist
Foliated Rocks
Gneiss
Non-foliated Rocks
Foliations can only develop during metamorphism if
there was mica and/or clay in the original parent rocks.
But what about clean
limestones?
Chalk Board
Non-foliated Rocks
Foliations can only develop during metamorphism if
there was mica and/or clay in the original parent rocks.
Marble (non-foliated)
Non-foliated Rocks
Quartz arenite sandstones also produce non-foliated
rocks when subjected to high grade metamorphism
Non-foliated Rocks
Warning: marble can look exactly the same as quartzite
Marble (non-foliated)
Quartzite (non-foliated)
Today’s Homework
1. Assignment number 4 (due now)
2. GY Photo assignment (due Friday Nov 20 by 5PM)
3. GY 302 mineral poster show
(LSCB 136 Hallway, Tues Nov 24. 1-3 PM) BONUS
Next Time
Contact metamorphism
GY 111: Physical Geology
Lecture 26: Regional Metamorphism
Instructor: Dr. Doug Haywick
dhaywick@southalabama.edu
This is a free open access lecture, but not for commercial purposes.
For personal use only.