Igneous Rocks

Igneous Rocks

location

Volcanic Rocks

“extrusive rock.”

Rocks that solidifed upon eruptive in a volcano. fast cooling, small crystals

Plutonic Rocks

Rocks that solidified underground

“Intrusive rocks.”

Intrusive locks slowly cool and crystallize inside the earth. slow cooling, large crystals

plumbing network

dikes, etc. lubing between

texture

some key properties:

• *crystalline*8888888888wg: interlocking crystals (no melt in between them), with big crystalline construction
• glassy: sillica frozen in place, large black faces
• fragmental: something in between
• porphyritic: bimodal distributions, large Crysta lstructurem

compositition

mafic

iron-rich rocks, “magnesium ferric icon”, relatie r

biotite, hornblende, pyroxene, olividine

felsic

sillca rich rocks; relatively light. “felsbar + sillica”.

quantz, plagioclass, feldspar, pottasium.

melt generation

Outer core is almost all icon and nickel, we rarely don’t get iron and nickle . Seismic evidence suggests that we get all of our melts from sciesmic activity.

Thus, 0.1% of the asthenosphere (upper mantle) accounts for the majority of the melt.

detour: heat tranfer

1. convection; advection (hot material adds to your hand (like hon
2. conduction: an (e.n., physical iron rod conducting heat)

geothermal gradient

The average geothermal gradient (e.g., just sticking things deeper and deeper) is not possible to cause melting (i.e. we are a bit short re temperature vs. pressure that causes melting.)

normal situation

Geothermal gradient (i.e. adding usual temperature/pressure) not enough to cause melting. i.e. when you go deep enough for temp to be high, pressure is also too high to hold it together.

heat-transfer melting

if magma swells up and heats up surrounding rock, then the surrounding rock at a lower pressure melts.

decompression melting

if you take something hot and deep and bubble it up quickly, it may not have time to cool down and thus it melts as the pressure reduces

This often happens when you rift a crust (i.e., pulling apart a continent.) This is you thinning the crust, and thus pressure reduces and decompression.

volatiles

add a catalyst: most commonly at subduction zones, since the intruding plate can often have water in it and you can change the melting temperature of the rock (think salting the driveway.)

1. rock gets wet
2. subduction
3. higher pressures causes hydrous minerals to break down, water thus releases
4. partial melting of the mantle

This is also why ocean-continent subduction zones causes a bunch of volcanos.

volcanism progression

how do melting generation result in Plutonic Rock features on the ground?

dike

Where volcanos “vertically” poke out due to geothermal gradient, we call thoes" dike"

sill

when it happens horizontally, we call those “sills”

pluton

an individual body of intrusive plutonic rock

batholith

a large body of plutonic rock, often made up of multiple plutons