Igneous Petrology (Part 2 - Intrusive Igneous Structures, Crystalline Forms)

Question 1

Plutons of more or less irregular shape with surface exposures _> 100km2

Answer 1

Batholith

Question 2

Plutons with surface exposures _< 100km2

Answer 2

Stocks

Question 3

A tabular, concordant pluton that parallels the country rock

Answer 3

Sill

Question 4

A dome-like concordant pluton characterized by a dome roof and flat floor.

Answer 4

Laccolith

Question 5

A dish-shaped concordant pluton that has a “champagne glass” appearance in a section view

Answer 5

Lopolith

Question 6

Tabular intrusions that cuts through the country rock.

Answer 6

Dike

Question 7

Cylindrical dikes exposed by erosion, and represents ancient conduits of old volcanoes.

Answer 7

Neck

Question 8

Cylindrical pipes that can extend up to 20 km deep and develop through explosive intrusions.

Answer 8

Diatremes

Question 9

Rocks that formed as a result of magma or lava cooling and solidifying

Answer 9

Igneous Rocks

Question 10

Intrusive Igneous Rock

Answer 10

Plutonic

Question 11

Extrusive Igneous Rock

Answer 11

Volcanic

Question 12

A direct type of classification of composition that involves visual comparison of minerals and determining their volume percentages.

Answer 12

Modal Classification

Question 13

An indirect type of classification of composition that analyzes the chemical composition of rocks

Answer 13

Normative Classification

Question 14

Factors for Igneous Rocks Classification

Answer 14

Composition and Texture

Question 15

Review table of Normative and Modal Classification

Answer 15

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Question 16

A plutonic, very dark-colored (ultramafic) rock, depleted in SiO2.

Answer 16

Peridotite

Question 17

A volcanic, very dark-colored (ultramafic) rock, depleted in SiO2.

Answer 17

Komatiite

Question 18

Komatiite is characterized by?

Answer 18

Spinifex Texture

Question 19

A plutonic, dark-colored (mafic), SiO2-poor (basic) rocks rich in plagioclase, pyroxene and olivine.

Answer 19

Gabbro

Question 20

A volcanic, dark-colored (mafic), SiO2-poor (basic) rocks rich in plagioclase, pyroxene and olivine.

Answer 20

Basalt

Question 21

A plutonic, salt and pepper-colored rock and generally contain more than half to almost two-thirds to SiO2.

Answer 21

Diorite

Question 22

A volcanic, gray-colored (intermediate), rock rich in hornblende, pyroxene and plagioclase and generally contain more than half to almost two-thirds SiO2.

Answer 22

Andesite

Question 23

A plutonic, light colored (felsic) rocks, containing approximately two-thirds SiO2. Can also be seen having a bit of pinkish hue

Answer 23

Granodiorite

Question 24

A volcanic, light colored (felsic) rocks, containing approximately two-thirds SiO2.

Answer 24

Dacite

Question 25

A plutonic, light colored (felsic) rocks, containing more than two-thirds SiO2.

Answer 25

Granite

Question 26

A volcanic, light colored (felsic) rocks, containing more than two-thirds SiO2.

Answer 26

Rhyolite

Question 27

Light colored, felsic, frothy, vesicular rock, less dense

Answer 27

Pumice

Question 28

Dark-colored, felsic, frothy, vesicular rock, more dense

Answer 28

Scoria

Question 29

A dark-colored silicic, non-crystalline igneous rock that has a glassy texture.

Answer 29

Obsidian

Question 30

A dark-colored basic, non-crystalline igneous rock that has a glassy texture.

Answer 30

Tachylite

Question 31

Complete crystal faces that are not impinged upon by other crystals, developed under circumstances such as slow cooling of magma.

Answer 31

Euhedral

Question 32

Partially complete crystal form

Answer 32

Subhedral

Question 33

Crystals that lack any observable faces

Answer 33

Anhedral/xenomorphic

Question 34

A mix of euhedral, subhedral and anhedral grains

Answer 34

Hypidiomorphic-granular texture

Question 35

Wholly crystalline texture

Answer 35

Holocrystalline

Question 36

Partially crystalline/partially glassy texture

Answer 36

Hypocrystalline

Question 37

Wholly glass texture

Answer 37

Holohyaline

Question 38

Texture that contains small crystals less than 1 mm in diamater that are not generally discernible to the naked eye and are associated with volcanic rocks that cool quickly on Earth's surface.

Answer 38

Aphanitic

Question 39

What is the type of aphanitic that igneous texture with crystals too fine to be identified even with a petrographic microscope

Answer 39

Cryptocrystalline

Question 40

Igneous texture containing minerals that can only be discerned using a petrographic microscope called microlites.

Answer 40

Microcrystalline

Question 41

Crystals too small for the naked eye but large enough to be identified with a petrographic microscope.

Answer 41

Microlites

Question 42

Characterized by crystals with diameters ranging from 1 to 30 mm but subdivided into three.

Answer 42

Phaneritic a. fine grained - 1mm to 3mm b. medium grained - 3mm to 10mm c. coarse grained - 10mm to 30mm

Question 43

Consists of two distinctly different crystal sizes due to a two stage cooling process

Answer 43

porphyritic

Question 44

Large crystals in a porphyritic texture.

Answer 44

Phenocrysts

Question 45

fine-grained material in a porphyritic texture

Answer 45

Groundmass

Question 46

A type of porphyritic texture where all crystals are visible to the naked eye.

Answer 46

Porphyritic-phaneritic

Question 47

A type of porphyritic texture where the phenocrysts are embedded in an aphanitic groundmass

Answer 47

Porphyritic-aphanitic

Question 48

Characterized by large crystals averaging more than 30 mm in diameter

Answer 48

Pegmatitic

Question 49

Igneous rocks with pegmatitic texture

Answer 49

Pegmatite

Question 50

The number of new "seed" crystals that develop per volume per unit time.

Answer 50

Crystal Nucleation Rate

Question 51

Factors affecting crystal nucleation

Answer 51

Cooling Rate Ion Availability Diffusion

Question 52

The rate at which elements migrate through magma that depends primarily on the viscosity of the melt.

Answer 52

Diffusion

Question 53

Elements that tend to increase molecular linkage which increases viscosity.

Answer 53

Network formers

Question 54

An igneous rock texture primarily composed of glass that develop in lava that solidifies without experiencing significant crystallization

Answer 54

Glassy/Holohyaline

Question 55

An amorphous solid possessing a disordered form, thereby lacking an ordered crystalline form.

Answer 55

Glass

Question 56

Occurs when melts come into contact with air and water, rapidly absorbing heat, causing the melt to solidify rapidly before crystals could nucleate and grow.

Answer 56

Quenching

Question 57

An igneous rock texture that contains recognizable phenocrysts in a glassy groundmass.

Answer 57

Vitrophyric

Question 58

An igneous rock with vitrophyric texture.

Answer 58

Vitrophyre

Question 59

A process when glasses crystallize into a solid state by growing on pre-existing microlitic or cryptocrystalline nuclei.

Answer 59

Devitrification

Question 60

Rounded masses of radiating crystals that develop from devitrification.

Answer 60

Spherulites

Question 61

black, glassy obsidian with cristobalite seeds that grew as "white snowflakes" within the obsidian.

Answer 61

Snowflake obsidian

Question 62

igneous rock texture characterized by a cloudy appearance.

Answer 62

Perlitic

Question 63

Glassy SiO2-rich volcanic rocks with a perlitic texture and higher water contents than obsidian.

Answer 63

Perlite

Question 64

Curved or subpherical cooling cracks

Answer 64

Perlitic cracks

Question 65

An igneous rock texture that are dominated by vesicles and develop due to exsolution and entrapment of gas bubbles in lava as it cools and solidifies.

Answer 65

Vesicular

Question 66

Spherical or ellipsoidal void spaces.

Answer 66

Vesicles

Question 67

A depth where volatiles exsolve from the liquid as a separate phase.

Answer 67

Level of exsolution

Question 68

A process that occurs above the level of exsolution where volatiles nucleate as small bubbles

Answer 68

Vesiculation

Question 69

Encountered when bubbles constitute 70-80% of the magma volume.

Answer 69

Fragmentation surface

Question 70

A modifier of igneous rocks placed before the rocks' names when they contain 5-30% vesicles.

Answer 70

Vesicular

Question 71

A modifier for igneous rocks containing less than 5% vesicles.

Answer 71

Vesicle-bearing

Question 72

An igneous rock texture primarily made up of cemented or welded pyroclasts.

Answer 72

Pyroclastic

Question 73

Rock particles of varying sizes ejected by volcanic eruptions

Answer 73

Pyroclasts

Question 74

Airborne pyroclasts ejected into the atmosphere

Answer 74

Tephra

Question 75

Rock fragment pyroclasts

Answer 75

Lithic

Question 76

Glassy fragment pyroclasts

Answer 76

Vitric

Question 77

Mineral and crystalline pyroclasts

Answer 77

Crystals