glg 101 - physical geology bob leighty igneous rocks
TRANSCRIPT
GLG 101 - Physical GeologyGLG 101 - Physical Geology Bob LeightyBob Leighty
Igneous RocksIgneous Rocks
These lecture notes are very similar to the ones I use in my traditional classes. You’ll find they are loaded with imagery and streamlined text that highlight the most essential terms and concepts. The notes provide a framework for learning and, by themselves, are not meant to be a comprehensive source of information.
To take advantage of the global knowledge base known as the Internet, I have included numerous hyperlinks to external web sites (like the Wikipedia, USGS, NASA, etc.). Follow the links and scan them for relevant info. The information from linked web sites is meant to supplement and reinforce the lecture notes – you won’t be responsible for knowing everything contained in them.
As a distance learning student, you need to explore and understand the content more independently than in a traditional class. As always, I will help guide you through this learning adventure. Remember, email Dr. Bob if you have any questions about today’s lecture ([email protected]).Leave no questions behind!
Explore and have fun!Explore and have fun!
These notes and web links are your primary “lecture” content in this class. Additionally, various articles are assigned each week to supplement this “lecture” information. I believe you’ll have enough information to reference without having to purchase a costly textbook.
> cool and crystallize at depth as intrusions
> migrate to the surface and erupt as extrusions
Most magma initially rises because of its greater buoyancy
The Life of MagmaThe Life of MagmaIgneousIgneous
RocksRocks
Crustal melting felsic magmas
Texture (crystal size) - mostly related to the cooling rate
(largely controlled by where the magma cools)
Composition (mineralogy) - mostly related to what was
melted
coarse-grained texture
Cool slowly
at depth
fine-grained texture
Cool fast
on surface
granite
rhyolite
Composition & TextureComposition & TextureIgneousIgneous
RocksRocks
Naming Igneous RocksNaming Igneous RocksIgneousIgneous
RocksRocks
click on the chart
magma
MaficMafic
Ca
Ca
Fe
Fe
Mg
Mg
Si
Si O
O
O
O
O
OO
O
Mafic magmas are rich in Fe, Mg, & Ca, but poor in Si, Na,
& K
Igneous CompositionsIgneous CompositionsIgneousIgneous
RocksRocks
basalt
gabbro
…which compose most mafic igneous rocks
Upon cooling, mafic magmas crystallize mafic minerals…
olivine
pyroxene
Ca-feldspar
MaficMafic
Igneous CompositionsIgneous CompositionsIgneousIgneous
RocksRocks
Abundant in the oceanic crust & mantle
peridotitegabbrobasalt
Mafic & Mafic & UltramaficUltramafic
Igneous CompositionsIgneous CompositionsIgneousIgneous
RocksRocks
peridotitegabbrobasalt
Mafic rocks form by partial melting of ultramafic mantle
Mafic & Mafic & UltramaficUltramafic
Igneous CompositionsIgneous CompositionsIgneousIgneous
RocksRocks
magma
K
K
Si
Si
Na
Na
Si
Si O
O
O
O
O
OO
O
Felsic magmas are poor in Fe, Mg, & Ca, but rich in Si, Na,
& K
FelsicFelsic
Igneous CompositionsIgneous CompositionsIgneousIgneous
RocksRocks
…which compose most felsic igneous rocks
rhyolite
granite
Upon cooling, felsic magmas crystallize felsic minerals…
quartz
K-feldspar
Na-Feldspar
mica
FelsicFelsic
Igneous CompositionsIgneous CompositionsIgneousIgneous
RocksRocks
rhyolite granitepumice
Abundant in the continental crust
FelsicFelsic
Igneous CompositionsIgneous CompositionsIgneousIgneous
RocksRocks
rhyolite granitepumice
Form by melting continental crust
FelsicFelsic
Igneous CompositionsIgneous CompositionsIgneousIgneous
RocksRocks
magma
K
Ca
Fe
Si
Mg
Na
Si
Si O
O
O
O
O
OO
O
“Combo deal” includes some mafic & felsic elements
IntermediateIntermediate
Igneous CompositionsIgneous CompositionsIgneousIgneous
RocksRocks
andesite
diorite
…which compose intermediate igneous rocks
Upon cooling, intermediate magmas crystallize int.
minerals…
amphibole
Ca/NaFeldspar
IntermediateIntermediate
Igneous CompositionsIgneous CompositionsIgneousIgneous
RocksRocks
andesite diorite
Abundant in the continental crust
IntermediateIntermediate
Igneous CompositionsIgneous CompositionsIgneousIgneous
RocksRocks
andesite diorite
Form by “wet” melting of the mantle and crust
IntermediateIntermediate
Igneous CompositionsIgneous CompositionsIgneousIgneous
RocksRocks
Big crystals (coarse-grained texture)
granite
> slow cooling at depth (intrusive)
microscope view
Igneous TexturesIgneous TexturesIgneousIgneous
RocksRocks
Small crystals (fine-grained texture)
basaltrhyolite
> fast cooling on the surface (extrusive)
Igneous TexturesIgneous TexturesIgneousIgneous
RocksRocks
No crystals (glassy texture)
> ultra-fast to cool (quenching) on the surface
(extrusive)
obsidian
Igneous TexturesIgneous TexturesIgneousIgneous
RocksRocks
Big & small crystals (porphyritic texture)
porphyritic andesite
> two stages of cooling: slower & faster cooling (int &
ext)
microscope view
Igneous TexturesIgneous TexturesIgneousIgneous
RocksRocks
> gas bubbles escaping the magma (extrusive)
Igneous TexturesIgneous TexturesIgneousIgneous
RocksRocks
Holes or vesicles (vesicular texture)
scoria
Pieces of rock (pyroclastic texture)
> explosive eruption (extrusive)
Volcanic breccia, lapilli, & tuff
increasing
explosivenes
s
Igneous TexturesIgneous TexturesIgneousIgneous
RocksRocks
WWW Links in this LectureWWW Links in this Lecture> Magma - http://en.wikipedia.org/wiki/Magma
> Buoyancy - http://en.wikipedia.org/wiki/Buoyancy
> Intrusions - http://en.wikipedia.org/wiki/Intrusion
> Extrusions - http://en.wikipedia.org/wiki/Extrusive
> Mafic - http://en.wikipedia.org/wiki/Mafic
> Basalt - http://en.wikipedia.org/wiki/Basalt
> Gabbro - http://en.wikipedia.org/wiki/Gabbro
> Oceanic crust - http://en.wikipedia.org/wiki/Oceanic_crust
> Mantle - http://en.wikipedia.org/wiki/Mantle_%28geology%29
> Peridotite - http://en.wikipedia.org/wiki/Peridotite
> Felsic - http://en.wikipedia.org/wiki/Felsic
> Rhyolite - http://en.wikipedia.org/wiki/Rhyolite
> Granite - http://en.wikipedia.org/wiki/Granite
> Continental Crust - http://en.wikipedia.org/wiki/Continental_crust
> Pumice - http://en.wikipedia.org/wiki/Pumice
> Andesite - http://en.wikipedia.org/wiki/Andesite
> Diorite - http://en.wikipedia.org/wiki/Diorite
> Obsidian - http://en.wikipedia.org/wiki/Obsidian
> Scoria - http://en.wikipedia.org/wiki/Scoria
> Tuff - http://en.wikipedia.org/wiki/Tuff
IgneousIgneous
ProcessesProcesses