Intro Flashcards
The study of the origin, occurrence, composition, and classification of rocks, including the history and geologic processes related to rocks.
Petrology
What is a rock
An aggregate of minerals and/or mineraloids.
What deals with the generation and origin of rocks.
Petrogenesis
Known as “primary rocks” that originated from solidified magma or lava.
Igneous rocks
Known as “secondary rocks” which formed as a result of lithified fragments of pre-existing rocks.
Sedimentary rocks
Rocks that formed as a result of pre-existing rocks undergoing metamorphism due to being subjected to heat, pressure, and fluids.
Metamorphic rocks
A rock that consists of multiple crystals of a SINGLE mineral.
Monomineralic rock
A rock that consists of MULTIPLE TYPES of minerals and/or mineraloids.
Polymineralic rock
A model showing the relationships and processes origins, between rock types and other geologic materials. (discuss)
rock cycle
The sub-branch of Petrology primarily focuses on processes and rocks that are formed from magma and lava.
Igneous Petrology
Molten rock material generated by partial melting of Earth’s mantle and crust. It contains liquids, crystals, gases and rock fragments in varying proportions depending upon temperature, pressure and chemistry conditions.
Magma
Magma that rises and erupts onto the surface of Earth.
Lava
Enumerate the composition of magma
- Melt
- Volatiles
- Crystals
The LIQUID portion of the magma.
Melt
The GASEOUS portion of the magma (H₂O, CO2, S, CI, F).
Volatiles
The SOLID portion of the magma.
Crystals
What is the process were
the magma or lava looses its heat and crystallizes?
What are the rocks Formed as a result of this process?
Crystallization- the process
Igneous Rocks-the product
Differentiate plutonic/intrusive and volcanic/extrusive rocks according to the crystal sizes.
Plutonic/Intrusive Igneous Rock
- Will tend to have larger crystal sizes as they have time to grow. (coarser-grained)
Volcanic/Extrusive Igneous Rock
- Will tend to have smaller crystal sizes as they rapidly cool and crystallize from the cooler environment. (finer-grained)
Igneous rocks that solidified at the surface as a result of extrusion.
Volcanic igneous rocks
Igneous rocks that formed beneath the surface as a result of loosing mobility.
Plutonic igneous rocks
-Medium-grained igneous rocks formed at shallow depths under moderate temperature and pressure.
-Give an example.
Hypabyssal Rocks
-Ex. Granodiorite
The process where your pre-existing rock is heated to the point of ________
Partial melting
What is partial melting within the Earth’s crust?
Anatexis
What are the factors determining the types of magma?
- Composition, temperature and depth of the source rock.
- Percent partial melting of the source rock.
- Source rock’s previous melting history.
- Diversification processes that change the composition of the magma after it leaves the source region.
What are the three origins of magma?
-Temperature increase
-Decompression melting
-Addition of volatiles
Origin of magma where magma is generated through heat transfer from a heated body until the melting point of the minerals present is reached.
Temperature increase
Increase of temperature with depth
Geothermal Gradient
25°C/km
-occurs as a result of the decrease in pressure in the system. Since magma behaves like a fluid, it migrates to areas with less pressure.
- the buoyant magma rises to fill in the space of lower pressure areas, common in divergent boundaries
decompression melting
The presence of volatiles in rocks acts as fluxes, weakening the bonds of atoms in the minerals, such as the Si-O bond, making them easier to melt.
Volatiles play an important role in generating magma at convergent plate boundaries where cool slabs of oceanic lithosphere descend into the mantle.
Addition of volatiles
Agents that reduce a melting temperature of a substance
Flux
