J-dek

Question 1

Hvordan kan vi få folding i de forskjellige strukturelle lagene:

• På/nær overflaten
• Midtre skorpe
• Nedre skorpe (undre)

Answer 1

På/nær: I sand, lava (ryolittisk)
Midtre: Leirstein, sandstein (10 km) og gneis (20 km)
Undre: Migmatitt (ca. 40 km), eklogitt (> 50 km)

Question 2

Hva er den viktigste terminologien for folder?

Answer 2

• Vendepunkt, amplitude, bølgelengde

- Hengsellinje, hengselpunkt, foldesjenkel, åpningsvinkel, foldeakseplan

Question 3

Hva er forskjellen på de forskjellige folde-formene?

Answer 3

Synform (U) og antiform (n) har ukjent stratigrafi.

Synklin og antiklin har kjent stratigrafi, og synklin har yngst lag mot midten.

Question 4

Nevn de forskjellige åpningsvinklene en fold kan ha.

Answer 4

Isoklinal (30 - 0)
Tett (70-30)
Åpen (120 - 70)
Svært åpen (180 -120)

Question 5

Hva er forskjellen på parallelle folder og similære?

Answer 5

Parallelle folder har konstant tykkelse på laget, mens similære folder har ikke.

Question 6

Hvordan kan du kjenne igjen forskjellen på symmetriske og asymmetriske folder?

Answer 6

Symmetriske har ikke dip på foldeakseplan, mens asymmetriske har dip. Det vil si at asymmetriske folder har forskjellige foldesjenkler.

Question 7

Hva er primære fabrics?

Answer 7

Sedimentære, magmatiske, salt-diapir

Question 8

Hva er “tectonites”?

Answer 8

Rocks with a penetrative tectonic fabric

Question 9

Hva er forskjellen på S og L tectonite?

Answer 9

S: Foliasjon dominert
L: Lineasjon dominert

Question 10

Hva er foliasjon?

Answer 10

Any sort of planar or semi-planar fabric in a rock:

- Bedding, cleavage, schistosity, gneissosity

Question 11

What is phyllites?

Answer 11

When lower green schist facies is reached, white mica and chlorite is formed. White mica contains more K and AL than illite and is better ordered.

Phyllitic cleavage is intermediate between slaty and schistosity.

Question 12

What is schist?

Answer 12

Middle greenschist facies where coarser grained mica is formed. The resulting foliation is called schistosity.

Question 13

What is gneissic layering?

Answer 13

At amphibolite to granulite facies conditions, where muscovite disappears and so does the schistosity.

Question 14

Name some types of lineations.

Answer 14

Form lineations: Fold hinge, necks at buodins

Surface lineations: skjæringslineasjon, fiberlineasjon, striasjoner

Mineral lineasjoner

Question 15

Name the three types of orogen styles.

Answer 15

Accretionary, collision and intracratonic

Question 16

Name the two types of accretionary orogens with examples.

Answer 16

Retreating (modern Western Pacific) and advancing (Andes).

Question 17

What is retreating (accretionary) orogen?

Answer 17

Western Pacific - type

• Long-term extension in response to lower plate retreat.
• Driven by negative buoyancy of down going slab
• Trench rollback
• Develop back-arc basins, upper plate extension
• Rifting of continental ribbons
• Magma can rise directly to the surface (mafic-felsic, bimodal)

Question 18

What is advancing (accretionary) orogen?

Answer 18

Andean type

• Overriding plate advances toward the downgoinf plate at rate equal or greater than the rate of lower plate slab retreat
• Widespread crustal shortening and uplift
• Resulting in a foreland fold and thrust belt
• Strike-slip motion common
• Subduction erosion: accretionary prism
• Large earthquakes
• Slow magma rise: since fractures are closed; causes large fractionation: intermediate to felsic rocks.

Question 19

Difference between retreating and advancing?

Answer 19

Have different velocities of slab retreat rates.

Question 20

Name 4 continent-continent.

Answer 20

1. India-Asia (Himalaya)
2. Laurentia - Baltika (Caledonides)
3. Adria - Europe (Alps)
4. E-W Gondwana

Question 21

What happens during continent-continent?

Answer 21

Crustal thickening, with high-P metamorphism

Eventually delimitation of orogen root, asthenosphere upwelling meling, granites gravitational collapse

Question 22

Hva er sammenhengen mellom temperatur og størrelse på orogen?

Answer 22

Large orogens are often hot, small orogens are often cold

Question 23

Describe c-c of the Caledonides.

Answer 23

440 Ma: Retreating accretionary early history of Caledonides, volcanic arc outside Laurentia.

430 Ma: Collision of island arc terrane with Baltica.

420-410 Ma: Collision Baltica-Laurentia: Caledonides

Question 24

What is orogenic gravitational collapse?

Answer 24

Orogens cannot grow in height forever, when a certain thickness is reached they tend to collapse under their own weight.

Question 25

What is indentation tectionics (lateral extrusion, escape)?

Answer 25

Indenter: Competent (stiff) block deforms another less competent (weaker) block.

Lateral extrusion: blocks that escape (move) laterally, away from the collision zone

Ex. India-Asia, North Anatolian Fault

Question 26

Hva er et godt eksempel på strike-slip forkastning?

Answer 26

San Andreas Forkastningen v/USA

Question 27

Hva er transform forkastning?

Answer 27

Forkastning som kun er aktiv mellom rygg-segmenter