Igneous Petrology

Question 1

The science concerned with rocks, including their mode of occurrence, composition, classification, origin, and their relations to geological processes and history.

Answer 1

Petrology

Question 2

A branch of petrology that deals with the history and origin of the rock; interpretations of the origin of rocks

Answer 2

Petrogenesis

Question 3

places emphasis on the purely descriptive part of rock science from textural, mineralogical, and chemical points of view.

Answer 3

Petrography

Question 4

Study of description and classification of rocks. It is considered an observational science because it looks at the physical features such as color, mineralogy, texture, etc.

Answer 4

Petrography

Question 5

the branch of geology dealing with the origin, occurrence,
structure, and history of rocks.

Answer 5

Petrology

Question 6

Rocks that directly solidify from molten or partially molten material, i.e. magma.

Answer 6

Igneous Rocks

Question 7

two basic types of igneous rocks

Answer 7

intrusive igneous rocks and extrusive igneous rocks

Question 8

what is the difference between intrusive igneous rocks and extrusive igneous rocks?

Answer 8

intrusive igneous rocks are formed beneath the surface of the Earth

extrusive igneous rocks are formed at the surface of the earth.

Question 9

another term for extrusive igneous rocks

Answer 9

Volcanic rocks

Question 10

another term for intrusive igneous rocks

Answer 10

Plutonic Rocks

Question 11

three general types of magma based on their chemical composition

Answer 11

Basaltic magma
Andesitic magma
Rhyolitic magma

Question 12

Magma that has 45-55% SiO2, high in Fe, Mg, Ca; low in K, Na; and has temperature range of 1000-1200°C

Answer 12

Basaltic Magma

Question 13

Magma that has: 55-65% SiO2, intermediate in Fe, Mg, Ca, K, and Na; has a temperature range of 800-1000°C

Answer 13

Andesitic Magma

Question 14

Magma that has 65-75% SiO2, low in Fe, Mg, Ca; high in K, Na; and has a temperature range of 650-800°C.

Answer 14

Rhyolitic Magma

Question 15

Low viscosity, low gas content, high-temperature magma

Answer 15

Basaltic Magma

Question 16

intermediate viscosity, intermediate gas content, intermediate temperature magma

Answer 16

Andesitic Magma

Question 17

High viscosity, High gas content, Low-temperature magma

Answer 17

Rhyolitic Magma

Question 18

Magma is generated for? and with what process?

Answer 18

Mantle; through Partial Melting

Question 19

Heat sources on the Earth

Answer 19

1. Heat from the early accretion and differentiation of the Earth;
2. Heat released by the radioactive breakdown of unstable nuclides

Question 20

similar to the melting of dry minerals, melting temperatures increase with increasing pressure, except there is a range of temperature over which there exists a partial melt, Partial melting can range from 0 to 100%

Answer 20

Melting of dry rocks

Question 21

similar to the melting of wet minerals, melting temperatures initially decrease with increasing pressure, except there is a range of temperatures over which there exists a partial melt

Answer 21

Melting of rocks containing water or carbon dioxide

Question 22

What are the ways to generate magma on (solid part of) the earth?

Answer 22

increase/ raise the geothermal gradient
lower the melting temperature of rocks.

Question 23

3 mechanisms of Magmatic Differentiation.

Answer 23

Fractional Crystallization
Magma mixing
Magmatic assimilation

Question 24

Likely to be the most important in controlling magmatic differentiation.

Answer 24

Crystal fractionation

Question 25

Magma is close to its original composition and has therefore in theory not undergone crystal fractionation.

Answer 25

primitive magma

Question 26

Magma in which crystal fractionation has taken place such the magma composition is different from the starting composition.

Answer 26

Evolved Magma

Question 27

where two magmas with different compositions happen to come in contact with one another and mix together and have a composition somewhere between that of the original two magma compositions.

Answer 27

Magmatic Mixing

Question 28

magma reacts with the “country rock” which is adjacent to the magma chamber.

Answer 28

Assimilation

Question 29

incompletely melted chunks of country rock. these materials contaminate the magma by incorporating materials originally present in the country rock.

Answer 29

Inclusions

Question 30

The reaction between the magma and the wall rock/ host rock

Answer 30

Magmatic assimilation

Question 31

Minerals in Bowen's reaction series: Discontinuous series (in order from high to low temp, and increasing SiO2 Liquids)

Answer 31

Olivine, Pyroxene, Hornblende (amphibole), Biotite

Question 32

Minerals in Bowen's reaction series: continuous series (in order from high to low temp, and increasing SiO2 Liquids)

Answer 32

Ca-rich to Na-rich Plagioclase (ABLAOA)

Question 33

Refers to any process that cause magma composition to change.

Answer 33

Magmatic Differentiation

Question 34

the proposed processes of Magmatic Differentiation

Answer 34

1. Distinct melting events from distinct sources 2. Various degrees of partial melting from the same source 3. Crystal Fractionation / Fractional Crystallization 4. Mixing of 2 or more magma (Magma mixing) 5. Assimilation/ Contamination of magma by crustal rocks 6. Liquid Immiscibility

Question 35

Each magma might represent melting at a different source rock at different times during the heating event

Answer 35

Distinct melting events from distinct sources

Question 36

In multicomponent rock systems, each component has its own melting range temperature.

Answer 36

Various degrees of partial melting from the same source

Question 37

the liquid composition changes as a result of removing crystals from the liquid as they form creating a magma with a different composition from the parent magma

Answer 37

Crystal Fractionation / Fractional Crystallization

Question 38

2 mechanism of fractional crystallization

Answer 38

Crystal settling/ floating crystals Inward crystallization

Question 39

Forming from magma will have different densities; Higher-density crystal sinks and lower-density crystal floats.

Answer 39

Crystal settling/ Floating Crystals

Question 40

The magma body is hot and the country rock that surrounds it is expected to be cooler, heat will move outward, away from the magma; the walls of the magma body will be coolest, crystallization is expected to take place in the cooler portion; magma expected to crystallize from walls inward

Answer 40

Inward crystallization

Question 41

Two or more magma with different compositions come in contact with one another beneath the surface and mix to produce magma with a composition intermediate between the end member (the two magma).

Answer 41

Magma Mixing

Question 42

factors that can inhibit (hinder) mixing.

Answer 42

Temperature contrast Density contrast Viscosity contrast

Question 43

The mechanism that makes magma mixing possible

Answer 43

Stirring e.g. Convection (where hotter magma rising through the cooler magma)

Question 44

Evidence(s) of Mixing

Answer 44

Mingling of Magmas Disequilibrium mineral assemblages Reverse Zoning Glass Inclusions Chemical Evidences

Question 45

“marble cake” appearance, dark-colored mafic rock intermingled with lighter-colored rhyolitic rock (banding)

Answer 45

Mingling of magma

Question 46

basaltic magma containing Mg-rich olivine mixed with rhyolite magma containing quartz

Answer 46

Disequilibrium mineral assemblages

Question 47

minerals placed in an environment different than the one in which it originally formed, will react, instead of dissolving completely, solid solution minerals start precipitating new composition that is stable – zoned crystals

Answer 47

Reverse Zoning in Minerals

Question 48

Crystal grows trapping liquid inside; glass should represent the composition of magma that precipitated the crystal.

Answer 48

Glass inclusions

Question 49

oxide-oxide variation diagrams

Answer 49

Chemical evidence

Question 50

A state in which two liquids with different compositions coexist in equilibrium with each other.

Answer 50

Liquid Immiscibility

Question 51

___________ do not mix and form an emulsion of droplets or network of one liquid within the other

Answer 51

Immiscible