6.2 what are igneous rocks
Igneous rocks:
Ignis, meaning fire
Magma cools, atoms/ions combine to form solid minerals = crystallization
Two types of igneous materials:
Magma: molten rock that stays within the crust and/or mantle
Lava: molten rock material that has erupted onto the earth’s surface
6.3.1 igneous rock types
Form three general types of igneous rock
intrusive or plutonic
Magma crystallizes below ground
Large, interlocking crystals
Slow cooling rate
Ex. Granite, gabbro, diorite
extrusive or volcanic
Lava crystallizes on or above the surface
Small (or no) crystals in a glassy groundmass
Fast cooling rate
6.6.2 Magmatic Differentiation
magma chamber B can interact with Magma chamber a and mix
6.7 Types of Igneous Intrusions
Pluton: body of magma emplaced into host rock (metamorphic)
Batholith: large igneous body (a group of plutons together)
ex. Tuolumne batholith, Yosemite, NP, CA
associated with oceanic continental convergent boundary
Magma’s orientation with host rock:
sill: concordant; igneous intrusion parallels the structure of the host rock (magma came and wedged in between)
dike: discordant; igneous intrusion cuts across the host rock (breaks rock for magma to crystalize)
6.8/6.8.1 Igneous Rocks and Plate Tectonics (slide 25)
magma and volcanoes form at divergent and convergent plate boundaries
transform and continent/continent = no melting
divergent: seafloor spreading at mid-ocean ridges
most igneous rocks on Earth are formed here
partial melting (decompression melting) of upper mantle
crystalizes as mafic basalt at surface; gabbro at depth
continental rifts can have felsic rocks, with enough rifting can start erupted basalt
convergent: ocean-continent or ocean-ocean boundaries
flux melting: water lowers melting temp
oceanic-continent: melts crystalize as intermediate andesite at surface, diorite at depth
oceanic-ocean: will have mafic basalt on surface, gabbro at depth
through magmatic differentiation can form felsic rocks