chapter 3 igneous and intrinsic activity Flashcards
____ produced of entirely igneous rocks
mantle
____ : parent material for igneous rocks
magma
magma component: composed of the earth most common components
liquid- “melt”
magma component: possibly absent: crystal and silicates
solid
magma component: volatiles- vaporize at surface pressures- H20, Co2, So2
Gas
as temperature increases magma becomes ________, if it continues to increase bonds _____ and rock ______
crystaline rock, become destroyed, melts
Cooling reverses the events of melting. liquid melt —> organised solid structure
crystalization
Chem comp, # of volatiles, rate of colling
How magmas differ
when magma solidifies it creates ___ rocks
Intrusive igneous
lava cools in surface creating ____ rocks
extrusive igneous
Texture and crystal visibility of intrusive igneous rocks
course-grained + visible crystals
Texture and crystal visibility of extrusive igneous rocks
fine-grained + volcanic debris
Feldspar and quartz dominant rocks
felsic rocks
category of igneous rocks with around 10% dark silicate minerals (usually biotite or amphisole)
felsic rocks
category of igneous rocks that are the major constituants of the earths crust
felsic rocks
Category of igneous rock that has at least 25% dark silicates (usually amphibole, pyroxene, and biotite mica or plagioclase feldspar
Andesetic (intermediate)
Category of igneous rock that contain dark silicate minerals and plagiocase feldspar
Mafic
Category of igneous rock that typically darker and denser than granitic rock
Mafic
category of igneous rock that has many dark silicates (usually olivine and pyroxene) ex. peridiodite
ULTRAMAFIC
Granitic Magma has _____ therefore is thicker
more silicates
Basaltic Magma has _____ therefore is smoother
less silicates
Texture of igneous rock as a result of very rapid cooling ex. Pumis (ash)
Glassy
Texture of igneous rock as a result of being debris of eruption, with fine fragments of glass instead of interlocking crystals
pyroclastic
Texture of igneous rock as a result of lava cooling quickly (fine-grained)
Aphanatic
Texture of igneous rock where the rate of cooling starts slow then speeds up, classified by the observation of large crystals surrounded by small crystals
poryphyritic
Texture of igneous rock classified by the presence of large interlocking crystals surrounded by small crystals. The small crystals are called _____
pegmatatic, groundmass
Texture of igneous rock classified by the creation from the cooling of magma at depth (coarse-grained)
Phaneric
Rock that is phanaretic and felsic
Granite
Rock that is phaneretic and intermediate
Diorite
Rock that is phaneretic and mafic
Gabbro
Rock that is Aphanatic and felsic
Rhyolite
Rock that is Aphanatic and intermediate
Andesite
Rock that is Aphanatic and Mafic
Basalt
Rock that is Poryphitic and Felsic
Granite porphyry
Rock that is Poryphitic and intermediate
Andesite porphyry
Rock that is Poryphitic and Mafic
Basalt Porphyry
Most magma originates when essentially solid rock, located in the crust and upper mantle, _____
melts
This increase in temperature with depth, known as the _____
geothermal gradient
Melting, which is accompanied by an increase in volume, occurs at higher temperatures at depth because of ________
greater confining pressure
Conversely, reducing confining pressure _______
lowers a rock’s melting temperature
when confining pressure drops sufficiently __________
decompression melting is triggered
Decompression melting occurs where hot, solid mantle rock ______
ascends in zones of convective upwelling
As an oceanic plate sinks __________
both heat and pressure drive water from the subducting crustal rocks
Melting of peridotite generates _____ magma
basaltic
In summary, magma can be generated three ways:
(1) when an increase in temperature causes a rock to exceed
its melting point; (2) in zones of upwelling a decrease in pressure
(without the addition of heat) can result in decompression melting; and (3) the introduction of volatiles (principally water) can lower the melting temperature of hot mantle rock sufficiently to generate magma
basaltic magma crystallizes over
a range of at least ____
200 °C of cooling
______ process occurs when the earlier-formed minerals are more dense (heavier) than the liquid portion and sink toward the bot- tom of the magma chamber
crystal settling
The formation of one or more secondary magmas from a single parent magma is called _______
magmatic differentiation
Once a magma body forms its composition can also change through the incorporation of foreign material. For example, as magma migrates through the crust, it may incorporate some of the surrounding host rock, a process called ________
assimilation
This process occurs when one magma body intrudes another that has a different composition
magma mixing
he incomplete melting of rocks is known as ________, a process that produces most magma
partial melting
When magma rises through the crust, it forcefully displaces preexisting crustal rocks referred to _________
as host or country rock.
The structures that result from the emplacement of magma into preexisting rocks are called ________
intrusions or plutons
Igneous bodies are said to be ________ if they cut across existing structures
discordant
Igneous bodies are said to be ________ if they form poarallel to features such as sedimentary strata
concordant
_____ are discordant bodies that cut across bedding surfaces or other structures in the host rock.
dikes
_____ are nearly horizontal, concordant bodies that form when magma exploits weak- nesses between sedimentary beds
sills
________ form as igneous rocks cool and develop shrinkage fractures that produce elongated, pillar-like columns.
Columnar joints
By far the largest intrusive igneous bodies are _______
batholiths
When molten material is quenched instantly, a mass of unordered atoms, referred to as ____, forms
glass
Rocks of intermediate compsition, (e.g., andesite and diorite) are rich in plagioclase ______
feldspar and amphibole
“Strange rock”
- Rock embedded in a seperate matrix
xenolith
Melting mechanisms
- Mid Ocean Ridge
- Hot material is brought to the surface
Melting mechanisms
-Hotspot (mantle plume)
Adds heat to the base of the lithosphere
Melting mechanisms
-Subduction zone
A subducting plate brings water with it, thereby decreasing the melting point of the other plate
