Igneous Rocks Flashcards
What is a Phanerite?
Coarse grained igneous rock
What is a Phanerite?
Coarse grained igneous rock
What is Pegmatite?
Igneous Rock with unusually large grains
What is Aphanite?
Fine grained igneous rock
What 3 descriptors describe the grains of igneous rock?
Phanerite, Pegmatite, Aphanite
How is a glassy igneous rock formed?
When magma cools very quickly (e.g obsidian)
What are the 6 most common minerals in igneous rocks?
Quartz, feldspar, Mica, Amphibole, Pyroxene, Olivine
What is a pluton?
An intrusive igneous body
What is the name given to an intrusive igneous body?
A pluton
What are the 5 types of minor pluton?
Dyke, Sill, Laccolith, Volcanic pipe, Kimberlite pipe
What is the largest pluton type (major pluton)?
A batholith
What’s the difference between a dyke and a sill?
Both tabular and sheet like but a dyke cuts across a body of rock, and a sill runs parallel to the layering/fabric of the rock it intrudes
Describe a laccolith.
An intrusion parallel to the layering of existing rocks which forces the ones above it to bend up like a dome
What is a volcanic pipe?
A pipe shaped conduit, usually vertical that once fed magma to a volcanic event.
What is a kimberlite pipe?
A cylindrical intrusion
What are xenoliths?
Fragments of rock in magma that are formed when magma dislodges fragments of rock which then sink through the less dense magma
What are two cooling features of magma?
Columnar joints, chilled margins
What are kimberlite pipes the world’s main source of?
Diamonds
What are layered intrusions?
Layers produced by crystal settling within a magma chamber
