19) Metamorphic textures

0.0(0)
studied byStudied by 0 people
learnLearn
examPractice Test
spaced repetitionSpaced Repetition
heart puzzleMatch
flashcardsFlashcards
Card Sorting

1/13

encourage image

There's no tags or description

Looks like no tags are added yet.

Study Analytics
Name
Mastery
Learn
Test
Matching
Spaced

No study sessions yet.

14 Terms

1
New cards

lineation

alignment of elongate minerals to make a linear fabric
stretching of non platy (amphibole/feldspar)
end view doesn’t look stretched

2
New cards

rock cleavage

tendency of a rock to break along parallel surfaces
mostly for low grade meta rocks, slaty minerals

3
New cards

axial plane cleavage

alignment of platy minerals normal to the major compressive stress responsible for the folding, parallel to the axial plane

if stress is horizontal we expect to see vertical cleavage

<p>alignment of platy minerals normal to the major compressive stress responsible for the folding, parallel to the axial plane</p><p>if stress is horizontal we expect to see vertical cleavage</p>
4
New cards

granoblastic

like array of bubbles
no pore space or sediment between any of the grains
recrystallized textures

5
New cards

porphyroblastic

fast growing porphyroblasts grow bigger than rest of crystals
grew in solid state within a fine grain as a result of compression
usually euhedral
garnet and staurolite are common in metapelites

6
New cards

poikiloblastic

porphyroblasts with abundant inclusions
inclusions inside are older, then larger mineral grew around it

7
New cards

crenulation cleavage

small scale folding of an earlier formed metamorphic fabric causing ripple or wavy appearance (crenulation)

8
New cards

pressure shadows

halo of minerals surrounding a porphyroblast differing from the matrix
commonly quartz, coarser than matrix

9
New cards

deformation twins

result of metamorphism and stress
common in calcite, plagioclase, and pyrx

differ from igneous polysynthetic twinning bc aren’t as straight, tend to taper, and may only be found in part of the grain

10
New cards

explain pre- syn- post- tectonic

porphyroblasts can grow at diff times during the history of the meta rock

porphs formed pre-tectonic will have foliation wrapped around them
porphs formed syn-tectonic will have foliation semi-wrapped around them, rotated
porphs formed post-tectonic will have foliation included in them

spiral is shear force syn-tectonic

<p>porphyroblasts can grow at diff times during the history of the meta rock</p><p>porphs formed pre-tectonic will have foliation wrapped around them<br>porphs formed syn-tectonic will have foliation semi-wrapped around them, rotated<br>porphs formed post-tectonic will have foliation included in them</p><p>spiral is shear force syn-tectonic</p>
11
New cards

details on migmatites

between igneous and meta rocks
form under extreme temp conds during prograde meta, partial melting
complicated folding
commonly occur within extremely deformed rocks expressing base of eroded mountain belts
light coloured leucosome within dark coloured melanosome

12
New cards

explain dynamic crystallization in fault zones

cataclasis: deformation of the rock caused by fracture and rotation of mineral grains
Ex: cataclastic breccia (formed in a fault)

comminution: breaking down into smaller size, crushing up, pulverizing

things at top are fairly easily eroded

<p>cataclasis: deformation of the rock caused by fracture and rotation of mineral grains<br>Ex: cataclastic breccia (formed in a fault)</p><p>comminution: breaking down into smaller size, crushing up, pulverizing</p><p>things at top are fairly easily eroded</p>
13
New cards

mylonite

ductile process, smearing out. parent rock is granite
protomylonite: not much grainsize reduction
ultramylonite: super finegrained, very smeared

14
New cards

porphyroclast

large mineral in finer grained matrix
clast older than matrix
relic of previous rock
occur in rock that have undergone shear
can be used to determine sense of shear
different from porphyroblast