Mineralogy Quiz questions Flashcards
(17 cards)
Why are some crystals skeletal?
Very rapid cooling of the some crystals
What are spherulites and where do they form?
Spherulites are small, rounded, crystalline structures that form from the crystallization of various substances, including polymers
How might magma be generated in mountain belts?
Anatexis of the crust from deep burial.
What type of magma is produced through decompression and dehydation partial melting
Mafic lavas/ Basaltic lavas.
Define magma in a sentence (Not just molten rock)
Polymerised silicate melt.
What structural processes occur in order for dykes to be emplaced?
Rifting
Where are you most likely to find Batholiths
Mountain Belts
What is commonest rock type on earth and what intrusions are they associated with
Gabbro/dolerite - dykes and sills.
What is likely to be the most common intrusion on Earth?
Dyke - Think of the oceanic crust
Put the following in order of increasing size:
a) Dyke
b) Laccolith
c) Batholith
d) Sill
e) Stock
- Dyke
- Sill
- Laccolith
- Stock
- Batholith
As you increase the silica content of the magma, what happens to the following physico-chemical properties?
Eruption temperature - decreases
Products - lavas versus pyroclastics - become more pyroclastic
Give the minerals associated with intermediate rocks
Minerals in intermediate rocks are MIXTURES of
MAFIC and FELSIC ones
Typically have plagioclase, amphibole, and biotite,
Are commonly found in volcanic arcs associated with subduction zones.
Give the minerals associated with mafic rocks
Olivine, Pyroxene, Amphiboles(e.g. hornblende) and Biotite
Give the minerals associated with Felsic rocks
Quartz, Plagioclase, Acid feldspar - Orthoclase
Give Ultramafic rock minerals
high FeO, low potassium, and are usually composed of greater than 90% mafic minerals
Define crystal fractionation
Fractional crystallization refers to processes which separate crystals from liquid.
When this happens the liquid that remains is considered as a new magma.
Where are intermediate rock founds typically
Mountain belts as intrusions. some oceanic islands/ island arcs.
