Chapter 4 Plutonic field relationships

studied byStudied by 0 people
0.0(0)
learn
LearnA personalized and smart learning plan
exam
Practice TestTake a test on your terms and definitions
spaced repetition
Spaced RepetitionScientifically backed study method
heart puzzle
Matching GameHow quick can you match all your cards?
flashcards
FlashcardsStudy terms and definitions

1 / 43

encourage image

There's no tags or description

Looks like no one added any tags here yet for you.

44 Terms

1

Plutonic Rocks

Intrusive – non-specific types commonly called plutons or intrusions
Typically thought of as solidified magma bodies formed at depth within Earth that intrude “country rock”
Remnants of:
 crystallized magma-chambers, magma lenses
 magma conduits /feeders
 volcanic plugs
 deep zones of crustal melt
Also late-stage intrusions of granitic veins and pegmatites
Multiple: All phases of injection are of the same composition
Composite: More than one rock type is represented.

New cards
2

Plutonic rocks classified by:

Tabular - injected along planes of weakness (fractures) sheet-like dikes (discordant) and sills (concordant)
Discordant: Cross cutting the country rock body
Concordant: parallel to the country rock structure

<p><span style="color: #000000">Tabular - injected along planes of weakness (fractures) sheet-like dikes (discordant) and sills (concordant)</span><span style="color: #000000"><br></span><span style="color: #000000">Discordant: Cross cutting the country rock body</span><span style="color: #000000"><br></span><span style="color: #000000">Concordant: parallel to the country rock structure</span></p>
New cards
3

Vast majority of dikes and sills form by injection and dilation

Types of tabular igneous bodies in bedded strata based on method of emplacement.

a. Simple dilation (arrows) associated with injection.

b. No dilation associated with replacement or stoping.

<p><span style="color: #000000">Types of tabular igneous bodies in bedded strata based on method of emplacement.</span></p><p><span style="color: #000000"> a. Simple dilation (arrows) associated with injection. </span></p><p><span style="color: #000000">b. No dilation associated with replacement or stoping.</span><span style="color: #000000"><br></span></p>
New cards
4

Dike discordant -crosscutting

knowt flashcard image
New cards
5

Vein

Vein refers to a small tabular body, whether or not it is discordant or concordant

<p><span style="color: #000000">Vein refers to a small tabular body, whether or not it is discordant or concordant</span></p>
New cards
6

Swarms

Genetically related sets of numerous dikes or sills

<p><span style="color: #000000">Genetically related sets of numerous dikes or sills</span></p>
New cards
7

Yhe
formation of ring dikes
and cone sheets.

Cross section of a rising pluton causing fracture and stoping of roof blocks.
b. Cylindrical blocks drop into less dense magma below, resulting in ring dikes.

c. Hypothetical map view of a ring dike with N- S striking country rock strata as might result from erosion to a level approximating X-Y in (b).
d. Upward pressure of a pluton lifts the roof as conical blocks in this cross section.
Magma follows the fractures, producing cone sheets. Original horizontal bedding plane shows offsets in the conical blocks.

<p><span style="color: #000000">Cross section of a rising pluton causing fracture and stoping of roof blocks.</span><span style="color: #000000"><br></span><span style="color: #000000">b. Cylindrical blocks drop into less dense magma below, resulting in ring dikes. </span></p><p><span style="color: #000000">c. Hypothetical map view of a ring dike with N- S striking country rock strata as might result from erosion to a level approximating X-Y in (b).</span><span style="color: #000000"><br></span><span style="color: #000000">d. Upward pressure of a pluton lifts the roof as conical blocks in this cross section.</span><span style="color: #000000"><br></span><span style="color: #000000">Magma follows the fractures, producing cone sheets. Original horizontal bedding plane shows offsets in the conical blocks.</span></p>
New cards
8

Caldera formation

knowt flashcard image
New cards
9

Plutonic rocks classified by: Non-tabular

Non-tabular – detailed form depends on depth, density, ductility of country rock
various shapes
stocks (< 100 km2): plugs, necks –often volcanic conduits
Batholiths- ( >100km2; often composite): Mostly discordant but some more conformable to regional structures
laccolith (arched roof)
lopolith (cone shaped basin)

New cards
10

Plutonic Bodies - Stocks

Smaller igneous bodies, generally steep sided (roughly cylindrical).
Many unrelated to larger batholiths
-These associated with alkaline mantle derived magmatism at continental rifts and hotspots
Not limited to being granitic

Some form in the roof zone of granitic batholiths and may be connected to a batholith at depth

<p><span style="color: #000000">Smaller igneous bodies, generally steep sided (roughly cylindrical).</span><span style="color: #000000"><br></span><span style="color: #000000">Many unrelated to larger batholiths</span><span style="color: #000000"><br></span><span style="color: #000000">-These associated with alkaline mantle derived magmatism at continental rifts and hotspots</span><span style="color: #000000"><br></span><span style="color: #000000">Not limited to being granitic</span></p><p><span style="color: #000000">Some form in the roof zone of granitic batholiths and may be connected to a batholith at depth</span></p>
New cards
11

Plutonic Bodies - Batholiths

-Largest plutonic rock body (>100km2).
-Smaller bodies called stocks
-
Broadly granitic in composition.
-
Typically form in orogenic belts
-
Deep roots. For some debate exists about the 3- shape/deeper structure
-
Magmas ascend at depth via plastic deformation of surroundings. At shallower depths ascend by stoping.
-Probably rise as diapir


-
Amount thermal energy to form and maintain batholith as it rises is high.
-
Most cases heat source is mantle-derived basaltic melts.
-Form in orogenic belts and some in continental hotspots & rifts

<p><span style="color: #000000">-Largest plutonic rock body (&gt;100km2).</span><span style="color: #000000"><br></span><span style="color: #000000">-Smaller bodies called stocks</span><span style="color: #000000"><br>-</span><span style="color: #000000">Broadly granitic in composition.</span><span style="color: #000000"><br>-</span><span style="color: #000000">Typically form in orogenic belts</span><span style="color: #000000"><br>-</span><span style="color: #000000">Deep roots. For some debate exists about the 3- shape/deeper structure</span><span style="color: #000000"><br>-</span><span style="color: #000000">Magmas ascend at depth via plastic deformation of surroundings. At shallower depths ascend by stoping.</span><span style="color: #000000"><br></span><span style="color: #000000">-Probably rise as diapir</span></p><p><span style="color: #000000"><br>-</span><span style="color: #000000">Amount thermal energy to form and maintain batholith as it rises is high.</span><span style="color: #000000"><br>-</span><span style="color: #000000">Most cases heat source is mantle-derived basaltic melts.</span><span style="color: #000000"><br></span><span style="color: #000000">-Form in orogenic belts and some in continental hotspots &amp; rifts</span></p>
New cards
12

Volcanic plugs

A volcanic plug: Stocks representing the cylindrical conduit and magma chamber
beneath volcanoes.

<p><span style="color: #000000">A volcanic plug: Stocks representing the cylindrical conduit and magma chamber</span><span style="color: #000000"><br></span><span style="color: #000000">beneath volcanoes.</span></p>
New cards
13

Volcanic plugs

volcanic neck: exposed portion of a plug, commonly remaining after the more easily eroded volcanics of the cone removed

<p><span style="color: #000000">volcanic neck: exposed portion of a plug, commonly remaining after the more easily eroded volcanics of the cone removed</span></p>
New cards
14

Ship Rock NM

Ship Rock NM the central feeder pipe of larger volcanic landform which has since
eroded away.

<p><span style="color: #000000">Ship Rock NM the central feeder pipe of larger volcanic landform which has since</span><span style="color: #000000"><br></span><span style="color: #000000">eroded away.</span></p>
New cards
15

Concordant Plutons: Laccoliths and Lopoliths

knowt flashcard image
New cards
16

Plutonic Bodies - Laccolith

-Sufficiently viscous (silicic) to limit magma flow along the horizon plane
-Shallow enough to lift the roof rock
-Much smaller than lopolith

New cards
17

Plutonic Bodies - Lopoliths


-Down warped (saucer-shaped) concordant mafic intrusion.

-Almost all Precambrian
-Much larger than laccolith
Bushveld complex in S. Africa largest at 300 km diameter and 8 km thick)
Took 200,000 years to cool
-Some associated with meteorite impact

New cards
18
term image
knowt flashcard image
New cards
19

Layered Mafic Intrusions: LMI form in regions of extensive magmatism

Characterized by igneous layering distinguishable by shifts in mineralogy, texture, or
composition

Many emplaced during the Precambrian, predominantly at the margins of ancient cratons during intervals of supercontinent accretion and destruction

<p></p><p><span style="color: #000000">Characterized by igneous layering distinguishable by shifts in mineralogy, texture, or</span><span style="color: #000000"><br></span><span style="color: #000000">composition</span></p><p><span style="color: #000000">Many emplaced during the Precambrian, predominantly at the margins of ancient cratons during intervals of supercontinent accretion and destruction</span></p>
New cards
20

Contacts of Plutons: Chilled margins:

Chilled margins: A margin of finer grain size resulting from rapid solidification of the pluton at the contact with wall rock (thermal effects)

<p><span style="color: #000000">Chilled margins: A margin of finer grain size resulting from rapid solidification of the pluton at the contact with wall rock (thermal effects)</span></p>
New cards
21

Contacts of Plutons

knowt flashcard image
New cards
22

Schelieren

Schelieren: Elongated or flattened mineral aggregates or ductile
heated xenoliths that produce disc-shaped mass

<p><span style="color: #000000">Schelieren: Elongated or flattened mineral aggregates or ductile</span><span style="color: #000000"><br></span><span style="color: #000000">heated xenoliths that produce disc-shaped mass</span></p>
New cards
23

Marginal foliations

Marginal foliations developed within a pluton as a result of differential motion across the contact.
If the intruding magma is sufficiently viscous and the country rock hot enough, the contact shear can also affect the country rock, rotating the foliation outside the pluton
into parallelism with the contact.
Discordant to Concordant

<p><span style="color: #000000">Marginal foliations developed within a pluton as a result of differential motion across the contact. </span><span style="color: #000000"><br></span><span style="color: #000000">If the intruding magma is sufficiently viscous and the country rock hot enough, the contact shear can also affect the country rock, rotating the foliation outside the pluton</span><span style="color: #000000"><br></span><span style="color: #000000">into parallelism with the contact.</span><span style="color: #000000"><br></span><span style="color: #000000">Discordant to Concordant</span></p>
New cards
24

Classification related to tectonic timing of intrusion

Related to Orogenic / subduction processes
Post-tectonic
After a metamorphic event, cross-cut deformation (lack deformational features ass. w/ met event) and overprint metamorphism


Syn-tectonic
During orogenic event.
Related to regional metamorphism foliation,continuous w/ emplacement
True granites associated with migmatites and gneiss


Pre-tectonic (rare)
Emplacement prior to an orogenic event. Imprinted by met.
MOR or Arc-related volcanism/plutonism

New cards
25

Additional Classification related to depth of intrusion

Pressure and Temperature of country rock


Epizonal : Brittle and Cool country rock
Shallow level < 8 Km (~3 kb, 0.3 Gpa)
Low T - <300 °C
Post-tectonic
Discordant – sharp contacts, tend to be smaller surface exposure
Contact metamorphic zone (high T low P)

Mesozonal – Low grade regional metamorphic rocks
Transitional (5-15 km, 300-500 °C)
Sharp-gradational contact; discordant or concordant
syn- or post- tectonics

Catazonal: Regional Metamorphism, hi-P and T (migmatites)
Deep Crustal levels >10 km
High T (> 400 -600°C)
Syn-tectonic, gradational contacts with no chilling margins
Conformable, deformation common

<p><span style="color: #000000">Pressure and Temperature of country rock</span></p><p><span style="color: #000000"><br></span><span style="color: #000000">Epizonal : Brittle and Cool country rock</span><span style="color: #000000"><br></span><span style="color: #000000">Shallow level &lt; 8 Km (~3 kb, 0.3 Gpa)</span><span style="color: #000000"><br></span><span style="color: #000000">Low T - &lt;300 °C</span><span style="color: #000000"><br></span><span style="color: #000000">Post-tectonic</span><span style="color: #000000"><br></span><span style="color: #000000">Discordant – sharp contacts, tend to be smaller surface exposure</span><span style="color: #000000"><br></span><span style="color: #000000">Contact metamorphic zone (high T low P)</span></p><p><span style="color: #000000">Mesozonal – Low grade regional metamorphic rocks</span><span style="color: #000000"><br></span><span style="color: #000000">Transitional (5-15 km, 300-500 °C)</span><span style="color: #000000"><br></span><span style="color: #000000">Sharp-gradational contact; discordant or concordant</span><span style="color: #000000"><br></span><span style="color: #000000">syn- or post- tectonics</span><span style="color: #000000"><br></span></p><p><span style="color: #000000">Catazonal: Regional Metamorphism, hi-P and T (migmatites)</span><span style="color: #000000"><br></span><span style="color: #000000">Deep Crustal levels &gt;10 km</span><span style="color: #000000"><br></span><span style="color: #000000">High T (&gt; 400 -600°C)</span><span style="color: #000000"><br></span><span style="color: #000000">Syn-tectonic, gradational contacts with no chilling margins</span><span style="color: #000000"><br></span><span style="color: #000000">Conformable, deformation common</span><span style="color: #000000"><br></span></p><p></p>
New cards
26

Magma Ascent and emplacement

knowt flashcard image
New cards
27

Diapir

Diapir: a mobile mass that rises andmpierces the layers above it.
Diapiric Rise Model: Rising through ductile country rocks or rely on fractures or other weaknesses in the rocks

<p><span style="color: #000000">Diapir: a mobile mass that rises andmpierces the layers above it.</span><span style="color: #000000"><br></span><span style="color: #000000">Diapiric Rise Model: Rising through ductile country rocks or rely on fractures or other weaknesses in the rocks</span></p>
New cards
28
New cards
29
New cards
30
New cards
31
New cards
32
New cards
33
New cards
34
New cards
35
New cards
36
New cards
37
New cards
38
New cards
39
New cards
40
New cards
41
New cards
42
New cards
43
New cards
44
New cards

Explore top notes

note Note
studied byStudied by 64 people
213 days ago
4.7(3)
note Note
studied byStudied by 26 people
891 days ago
5.0(1)
note Note
studied byStudied by 25 people
514 days ago
5.0(1)
note Note
studied byStudied by 4 people
688 days ago
5.0(1)
note Note
studied byStudied by 16 people
903 days ago
5.0(1)
note Note
studied byStudied by 10 people
760 days ago
5.0(1)
note Note
studied byStudied by 67 people
701 days ago
5.0(4)
note Note
studied byStudied by 44 people
758 days ago
5.0(3)

Explore top flashcards

flashcards Flashcard (92)
studied byStudied by 11 people
841 days ago
4.0(1)
flashcards Flashcard (116)
studied byStudied by 10 people
800 days ago
5.0(1)
flashcards Flashcard (43)
studied byStudied by 15 people
3 days ago
5.0(1)
flashcards Flashcard (57)
studied byStudied by 17 people
750 days ago
5.0(2)
flashcards Flashcard (40)
studied byStudied by 2 people
177 days ago
5.0(1)
flashcards Flashcard (71)
studied byStudied by 42 people
385 days ago
5.0(4)
flashcards Flashcard (82)
studied byStudied by 41 people
88 days ago
5.0(1)
flashcards Flashcard (222)
studied byStudied by 29 people
646 days ago
5.0(1)
robot