Igneous Association

Question 1

Suites of rocks that form in response to similar geologic conditions.

Answer 1

Petrotectonic Associations

Question 1

What are the three classifications of petrotectonic associations?

Answer 1

1. Divergent Plate Boundary Magmatism
2. Convergent Plate Boundary Magmatism
3. Intraplate Magmatism

Question 2

Primarily driven by the decompression of the asthenosphere in response to lithospheric extension resulting in partial melting of mantle peridotite at divergent margins, producing basic (mafic) melts that rise to solidify and produce oceanic crust

Answer 2

Divergent Plate Boundary Magmatism

Question 3

A sequence of the ocean lithosphere containing four distinct layers.
Enumerate the four distinct layers.

Answer 3

Ophiolitic sequence

Question 4

Slices of ocean lithosphere preserved in landmasses.

Answer 4

Ophiolites

Question 5

Basalts and gabbros that are geochemically distinct which formed from partial melting of lherzolite at ocean spreading centers, and contain plagioclase, augite, hypersthene, pigeonite, diopside and olivine.
-What are its two types?

Answer 5

Mid-Ocean Ridge Basalts (MORB)

Question 6

Strongly depleted in highly incompatible elements such as large ion lithophile (LIL) elements, high field strength (HFS) elements, and light rare earth elements (LREE), which implies that they represent 20-30% partial melting of a well-mixed, depleted mantle source.

Answer 6

Normal MORB (N-MORB)

Question 7

Contains higher incompatible element (LREE, HFS, LIL) concentrations compared to N-MORB, representing smaller degrees (~10-15%) of partial melting of residual mantle rock so that the incompatible elements are more highly concentrated in E-MORB magmas.

Answer 7

Enriched MORB (E-MORB)

Question 8

-Ions that are easily accommodated in the crystal lattice and mineral structure.
-They are left in the ‘early stages’ of the melt. Therefore, it is concentrated in the solid.

Answer 8

Compatible Elements

Question 9

• Ions that do not fit into the mineral structure of rock- forming minerals at the time of crystallization of the magma, leading to accumulation in the residual magma and concentration in late-stage differentiation.
  -They tend to ‘stick’ to the melt instead of the crystallizing portion. Therefore, it is concentrated in the melt.

Answer 9

Incompatible Elements

Question 10

Small, highly charged incompatible elements (REE, Th, U, Ce, Pb4+, Zr, Hf, Ti, Nb, Ta).

Answer 10

High Field Strength (HFS) Elements

Question 11

Low field strength incompatible elements that are more mobile, especially in a fluid phase.

Answer 11

Large Ion Lithophile (LIL) Elements

Question 12

Specific elements that are common but rarely occur in significant amount enough to be economically extractable.

Answer 12

Rare Earth Elements (REE)

Question 13

Generates chemically diverse igneous assemblages that erupt in the convergent margins widely distributed around the globe, occurs for thousands of kilometers parallel to the trench, and up to 500 km perpendicular to the trench in the direction of the subduction.

Answer 13

Convergent Plate Boundary Magmatism

Question 14

What are the 5 variables that can diversify magma composition?

Answer 14

1. Composition and geometry of the crust.
2. Composition of material undergoing anatexis.
3. Flux melting
4. Diversification processes
5. Dip angle of the subduction zone

Question 15

The calc-alkaline association - signature volcanic rock suite of convergent margins which is one of the most voluminous rock assemblages on Earth.

Answer 15

Basalt, Andesite, Dacite, Rhyolite (BADR)

Question 16

Develop on the overlying ocean lithosphere plate above the subduction zone.

Answer 16

Island Arcs

Question 17

(Under island arcs)
Contains calcium plagioclase and quartz, with minor potassium feldspar, biotite, and hornblende.

Answer 17

Tonalite

Question 18

(Under Island Arcs)
Also called plagiogranite, are granodioritic rocks with half to two- thirds sodium plagioclase for the total feldspar content.

Answer 18

Trondjhemite

Question 19

Produce low potassium arc tholeiite basalts, as well as relatively rare rocks such as boninites and adakites.

Answer 19

Young Island Arc Systems

Question 20

Archean associations found in archean subduction zones where adakite formation is linked to.

Answer 20

Tonalite, Trondhjemite and Granodiorite (TTG) associations

Question 21

Develops behind an arc during lithospheric extension occurring in the overlying plate and can erupt a diverse suite of volcanic rocks.

Answer 21

Back-arc Basins

Question 22

Mature convergent arcs that involve the subduction of ocean lithosphere beneath thick continental lithosphere, where the subducting lithosphere reacts with the overlying plate, and produces more silicic magmas.

Answer 22

Continental margin arcs

Question 23

Arcs producing voluminous granodiorite, diorite, granite, and tonalite plutons which can erupt onto the Earth’s surface and produce composite volcanoes.

Answer 23

Ocean-continent convergent margins

Question 24

Dark-colored, trachyandesites, potassium-rich commonly containing olivine and augite phenocrysts with a groundmass of labradorite plagioclase, alkali feldspar, olivine, augite, and leucite.

Answer 24

Shoshonites

Question 25

Continent-continent collisions where the lower continental lithosphere does not subduct to great depths, but essentially breaks off and underplates the overlying continental lithosphere plate, producing a doubly thick lithosphere.

Answer 25

Continent collision zones

Question 26

Fault-bounded, deformed rock sequences that mark the site of present or former convergent margins.

Answer 26

Alpine orogenic complexes

Question 27

An intensely sheared, heterogenous rock assemblage embedded within a highly deformed mud matrix.

Answer 27

Tectonic mélange

Question 28

Enumerate the types of granites.

Answer 28

1. M-type granite (derived from mantle-derived parental magma)
2. I-type granite (generated by melting of igneous protolith)
3. S-type granite (produced by melting of sedimentary crustal rocks)
4. A-type granite (anorogenic rocks)

Question 29

Magma generation and igneous rock suites generated within lithospheric plates which may be initiated by hotspot activity, continental rifts, or overthickened continental lithosphere,

Answer 29

Intraplate magmatism

Question 30

-Greatest manifestations of intraplate magmatism on Earth, encompassing >106 km³ in volume, which occur as both oceanic flood basalts and continental flood basalts, and is generally basaltic in composition.

Answer 30

Large igneous provinces (LIP)

Question 31

LIPs that are more silicic in composition.

Answer 31

Silicic large igneous provinces (SLIP)

Question 32

Involves Ocean islands and ocean plateaus that formed above mantle hotspots that erupt anomalously high volumes of tholeiitic and alkalic basaltic lava onto the ocean floor.

Answer 32

Oceanic intraplate Magmatism

Question 33

Volcanic landforms that rise upward above sea level.

Answer 33

Ocean Islands

Question 34

Volcanically produced peaks
below sea level.

Answer 34

Seamounts

Question 35

Broad, flat-topped areas that result from massive outpourings of lava flowing laterally from source vents

Answer 35

Oceanic Plateaus

Question 36

Geochemically distinct suite of rocks that are more alkalic, less depleted, and may be somewhat enriched with incompatible elements that is interpreted to represent different mantle sources areas.

Answer 36

Ocean Island Basalts (OIB)

Question 37

Magmatism and volcanism within continental plates that can produce continental flood basalts (CFB), continental rift assemblages, bimodal volcanism, layered basic and ultrabasic intrusions, ultrabasic suites which includes komatiites and kimberlites, and an unusual array of alkaline rocks and anorogenic granites.

Answer 37

Continental Intraplate Magmatism

Question 38

Huge outpourings of basalts within continental plates.

Answer 38

Continental Flood Basalts (CFB)

Question 39

A continental feature that produce a wide array of rocks, including alkalic basalt, as well as alkalic and silicic rocks.

Answer 39

Continental Rifts

Question 40

The widespread occurrence of basalt and rhyolite without significant andesite and occurs at continental rifts and hotspots underlying continental lithosphere.

Answer 40

Bimodal Volcanism

Question 41

Anorogenic bodies injected into stable continental cratons at moderate depths.

Answer 41

Layered Basic-Ultrabasic Intrusions

Question 42

Brecciated, magnesium-rich,
ultrabasic rocks that rapidly rise to Earth’s surface via cylindrical diatremes from deep within the mantle and are intimately associated with diamonds

Answer 42

Kimberlites

Question 43

-Shallow intrusive to volcanic rocks that contain >20% CO3 minerals, and form in stocks, dikes and cylindrical structures primarily at continental rifts.
-Only known active volcano to produce this type of rock?

Answer 43

-Carbonites
-Ol Doinyo Lengai

Question 44

Magnesium-rich, volatile-rich, porphyritic rocks containing mafic phenocrysts, and are associated with kimberlites and continental rift zones

Answer 44

Lamprophyre

Question 45

Potassium-rich, peralkaline rocks containing pyroxene and olivine minerals enriched in barium, lanthanum, and zirconium, but relatively poor in CO2, and occur in areas of thickened lithosphere that have experienced earlier plate convergence or rifting episodes.

Answer 45

Lamproite