Classifications (Chapter 2) Flashcards
Phaneritic
Individual crystals are visible (with the naked eye)
Also plutonic or intrusive
Aphanitic
Individual crystals are not visible (with the naked eye)
Also volcanic or extrusive
Fragmental
Has pieces of pre-existing fragmented rock. Also pyroclastic
Equigranular
Grain size is more or less even
Porphyritic
Two populations of grain size
Seriate
Continuous change in grain size
Based on Si02 content, what are the four categories igneous rocks can be categorized as? (In the order of increasing Si02 content)
Ultrabasic, Basic, Intermediate, Acidic
What are the two components to igneous nomenclature?
The root name and its qualifier(s)
If a root name has two qualifiers, which one is more important?
The qualifier that is closest to the root name
What are three types of minerals used in the classification scheme?
Essential minerals
Type minerals
Accessory minerals
What is an essential mineral?
A mineral that is required to qualify for the root name
What is a type mineral?
A mineral that is used as a qualifier to subdivide the rock name
What is an accessory mineral?
Minor minerals that are described but not named.
True or False: Can the IUGS classification be used for pyroclastic rocks?
False. The IUGS classification can only be used for phaneritic and aphanitic rocks.
What are five common minerals/mineral groups that are in igneous rocks?
Quartz, Plagioclase, Alkali Feldspar, Feldspathoids, Mafics and accessories
True or False: Quartz and Feldspathoids cannot co-exist
True. As well as quartz and olivine.
What type of rocks are included in the QAT diagram?
Felsic Phaneritic Rocks (Diagram 2.1)
What type of rocks are included in the APF diagram?
Alkaline Felsic Phaneritic Rocks (Diagram 2.2)
What types of rock do the two corner diagrams include?
1) Basic-ultrabasic / mafic-ultramafic rocks (plag rich) (Diagram 2.3)
2) Ultramafic rocks (>90% mafics) (Diagram 2.4)
What is the TAS diagram?
A diagram that uses chemical composition as parameters for classification. Usually used for classifying aphanitic rocks
What are four special names for high Mg volcanic rocks?
Picrite, Komatiite, Meimechite, Boninite
What does the CIPW norm stand for and what is it?
Cross, Iddings, Pirsson, Washingston.
It is a normative mineralogy calculation that can be used when chemical composition of the whole rock is known.
What are some important rocks that aren’t included in the IUGS classification diagrams?
Hypabyssal: diabase
Carbonatites
Lamprophyres
Spilites
Keratophyres
Pyroclastic rocks
- “Fire-broken” rocks
- Comes from blocks/bombs, lapilli, or ash
- No phenocrysts, just clasts
- > 75% pyroclasts
