Magma And Intrusive Structures

Question 1

Melting of source rocks

Answer 1

Anatexis

Question 2

requires that the melt remains in contact with the residual rock throughout the melting process. As a result, the overall composition of the system remains the same

Answer 2

Equilibrium melting

Question 3

Implies that solids and melt separate into isolated fractions that do not continue to react together during the melting process.

Answer 3

Fractional melting

Question 4

Earth ’ s average geothermal gradient is?

Answer 4

∼ 25 ° C/km for the upper 10km

Question 5

geothermal gradient variation for old rocks

Answer 5

5-10C/km

Question 6

Geo gradiemd for hotspots

Answer 6

30 to 50C/km

Question 7

Decompression melting, also known as , results from a decrease in pressure.

Answer 7

adiabatic melting?

Question 8

CO, CO2 , OH, SO2 , H2S, NH3 , K2O, Na2O, HCl and HF, as well as the elements H, F, Cl, S, He and Ar

Answer 8

Volatiles

Question 9

A is an agent that reduces the melting temperature

Answer 9

flux

Question 10

H2O, CO2 , K2O and Na2O is the major cause for partial melting in subduction zones. T or f

Answer 10

T

Question 11

original melt evolves into one or more melts with a different composition, without material being exchanged with an external source

Answer 11

Differentiation

Question 12

processes whereby early formed crystals are segregated from the remaining melt

Answer 12

Fractional crystallization

Question 13

father of modern petrology

Answer 13

Bowen

Question 14

Sill studied by bowen

Answer 14

Palisades sill

Question 15

Coarse grained basalt

Answer 15

Diabase

Question 16

indicate incomplete discontinuous chemical reactions between crystals and melts

Answer 16

Rxn rims

Question 17

Bc they do not react with the magma, continuously or discontinuously

Answer 17

muscovite, potassium feldspar and quartz

Question 18

Models for fractional crystallization

Answer 18

marginal accretion, gravitational separation, convective fl ow and filter pressing.

Question 19

Crystallization along the walls of the magma chamber

Answer 19

marginal accretion

Question 20

includes crystal settling and crystal flotation processes

Answer 20

Gravitational separation

Question 21

one parent magma fractionates to produce two or more distinctly different daughter magmas with different compositions

Answer 21

Liquid fractionation

Question 22

Liquid fractionation processes include (2)

Answer 22

differential diffusion and liquid immiscibility

Question 23

involves the preferential diffusion of select ions within the magma in response to compositional, thermal or density gradients as well as water content. Differential diffusion may play a key role in the transport and concentration of metallic ore deposits in plutonic systems

Answer 23

Differential diffusion

Question 24

, also called liquid – liquid fractionation , occurs when magma separates into two or more distinct immiscible liquid phases

Answer 24

Liquid immiscibility

Question 25

Forceful injection of magma commonly fractures the surrounding wall rock by a process called _ . Country rock fragments that fall ( stope ) into the magma are called_

Answer 25

stoping, xenoliths

Question 26

involving multiple magma injections over time, produces complex relationships and constitutes an important diversification mechanism

Answer 26

Magma replenishment

Question 27

occurs when two or more dissimilar magmas coexist, displaying contact relations but retaining their distinctive individual magma characteristics

Answer 27

Magma mingling

Question 28

marble cake is caused by?

Answer 28

Magma mingling

Question 29

implies thorough mixing so that the individual magma components are no longer recognizable. For example, felsic and mafi c magma can mix to produce an intermediate magma

Answer 29

Magma mixing

Question 30

consists of genetically related magmas that have changed composition from a common original parental magma

Answer 30

magma series

Question 31

Igneous rock series include: (2)

Answer 31

alkaline (or alkalic), and (2) sub - alkaline assemblages

Question 32

high Na2O and K2O concentrations compared to SiO2 and are generally undersaturated with respect to SiO2

Answer 32

Alkaline

Question 33

subalkaline series can be subdivided into (2)

Answer 33

calc alkaline and tholeiite suites

Question 34

rocks have moderate to high Na2O, K2O and SiO2 concentrations

Answer 34

Calc alkaline

Question 35

have low Na2O and K2O but high FeO and CaO concentrations

Answer 35

Tholeiites

Question 36

Standard references include

Answer 36

Chondrite, primitive mantle, NMORB, EMORB, OIB

Question 37

Useful in demonstrating enrichment or depletion of compatible VS incompatible elements

Answer 37

Spider diagram

Question 38

Depletion of europium indicates plag fractionation from melt. T or f

Answer 38

T

Question 39

Enrichment of europium indicates assimilation of plag. T or f

Answer 39

T

Question 40

Calc alkali series include

Answer 40

Dacite, rhyolite, andesite, high alumina basalt(16-50%al2o3)

Question 41

Magmas that dominate convergent e.g. Circum pacific

Answer 41

Calc alk

Question 42

Rocks in convergent margin volcanoes are known as?

Answer 42

BADR

Question 43

Al203 (Inc, Dec) with crystallization of ferromag monerals(olivine, Pyro, amphi) then (Inc, Dec) with removal of plag and micas

Answer 43

Inc, dec

Question 44

MgO and Fe203 (Inc, Dec) with crystallization of ferromag min

Answer 44

Dec

Question 45

Cao (Inc, Dec) with crystallization of Calc plag

Answer 45

Dec

Question 46

NaO (Inc, Dec) due to removal of ig MgO Fe203 CaO, then (Inc, Dec) as sodium plag crystallizes in andesitic and more silicic rocks

Answer 46

Inc, dec

Question 47

Sio2 and k20 (Inc, Dec) as MgO Fe203 CaO na203 Al203 are progressively removed by crystallization

Answer 47

Inc

Question 48

_magmas and basalts dominate extensional envi e.g. Ocean ridges and cont drifts

Answer 48

Tholeiitic

Question 49

Tholeiites occur over Hotspot in intra plate settings and in frontal portions of immature (relatively young) volc. Arcs (characterized by thinning crust). T or f

Answer 49

T

Question 50

Amphi mins from alkaline magmas include

Answer 50

Riebeckite, richterite

Question 51

Pryxn mins from alkaline rocks

Answer 51

Aegerine, aegirine-augite, spodumene

Question 52

Alkaline rocks

Answer 52

Alkali basalts, hawaiite, benmoreite, mugearite, trachyte, nephelinite, phonolite, lamprophyre, carbonatite, komatiite, kimberlite

Question 53

Alkali rocks occurs in?

Answer 53

Stable cratonic interior, cont rifts, ocean islands away from spreading centers and subd zones ,

Question 54

Both alkali and tholeiitic magmas occur at hotspots, ocean islands, Rift envi. T or f

Answer 54

T

Question 55

Calc alkaline occur almost at convergent margins. T or f

Answer 55

T

Question 56

Tholeiitic magmas generated at ocean spreading centers, in cont rifts, Backarc basins, ocean islands, hotspots. T or f

Answer 56

T

Question 57

Alkaline magmas occur primarily at hotspots, ocean islands, Rift. T or f

Answer 57

T

Question 58

Bomodal rifts occur at cont rifts. T or f

Answer 58

T

Question 59

Magmas of Rift valley

Answer 59

Alk and bomodal

Question 60

Volc. Arc magma

Answer 60

Calc. Alkali

Question 61

Ocean Island magma

Answer 61

Tholeiitic and alkali

Question 62

Ocean ridge magma

Answer 62

Tholeiitic