01 - Rock Classification

Question 1

Definition

Rock

Answer 1

naturally occurring aggregates of one (monomineralic) or more minerals (polymineralic).

Question 2

Three major rock groups

Answer 2

Igneous rocks -> magmatites

Metamorphic rocks -> metamorphites

Sedimentary rocks -> sediments

Question 3

Three main processes of rock cycle

Answer 3

1. Erosion & sedimentation
2. Melting & recrystallization
3. Sink & recrystallization

Question 4

Igneous rocks:

three types by occurence and position in crust

Answer 4

plutonic

volcanic

subvolcanic

Question 5

Igneous rocks:

classification according to chemical / mineralogical composition

distingluishes .. (4)

Answer 5

• felsic or silicic rocks (granite, rhyolite) -> acid
• intermediate rocks (granodiorite, diorite, dacite, andesite)
• mafic rocks (basalt, gabbro) -> basic
• ultramafic rocks (peridotite, dunite)

Question 6

Igneous rocks:
Streckeisen in Exercise 1
Mafic & Ultramafic clasification -> Bilder angucken
TAS

Answer 6

Streckeisen in Exercise 1
Mafic & Ultramafic clasification -> Bilder angucken
TAS

Question 7

Metamorphic rocks:

classification … (4)

Answer 7

• in low, medium, high grade
• in metamorphic facies zones (mineral paragenesis)
• after textures (slate, schist, gneiss, fels)
• after origin (contact-, regional-, subduction-, shock-)

Question 8

classification in low, medium, high grade:

Sort with increasing metamorphic grade:

• schist
• gneiss
• slate
• blueschist
• phyllite
• migmatite

Answer 8

Low grade:

1. slate
2. phyllite

Intermediate grade:

3. blueschist
4. schist

High grade:

5. gneiss
6. migmatite

Question 9

in metamorphic facies zones:

name the 3 major types of metamorphic series

Answer 9

1. High P/T Series
2. Medium P/T Series
3. Low P/T Series

Question 10

in metamorphic facies zones:

1. High P/T Series - facies?

Answer 10

Zeolite

• > Blueschist
• > Eclogite

(high increasing P and low increasing T)

Question 11

in metamorphic facies zones:

2. Medium P/T Series - facies?

Answer 11

Zeolite

• > Greenschist
• > Amphibolite
• > Granulite

(increasing P and increasing T)

Question 12

in metamorphic facies zones:

3. Low P/T Series - facies?

Answer 12

Zeolite

• > Hornfels (Ab-Ep -> Hornblende -> Pyroxene)
• > Sanidinite or Granulite

( low increasing pressure and high ingreasing T

Question 13

Sedimentary rocks:

name the 3 major rock classes

Answer 13

1. clastic
2. chemical
3. organic

Question 14

Sedimentary rocks - clastic:

formation processes

Answer 14

• erosion, reworking, transportation
• deposition & sedimentation
• compaction and diagenetic processes

Question 15

Sedimentary rocks - clastic:

what does the physical properties strongly depend on?

(was red marked in lecture)

Answer 15

1. Textural properties:
   - particel dimensions
   - size
   - shape
   - spatial orientation
2. mineral composition
   - presence and effect of clay minerals

Question 16

Sedimentary rocks - clastic:

Grain size classification

Answer 16

< 0.002 mm Clay

0. 002 - 0.0063 mm Silt
1. 0063 - 2.0 mm Sand
2. 0 - 63 mm Gravel

> 63 mm Boulder

Question 17

Sedimentary rocks - clastic:

Q,F,L classification

Answer 17

Q - quartz
F - feldspar
L - lithoclasts
and matrix

< 5% matrix:

• > Quartz arenite (Q)
• > Feldspatic arenite (F,Q)
• > Lithic arenites (L,Q)

5-50% matrix
Wackes

> 50% matrix:
shales/Mudrocks

Question 18

Sedimentary rocks - clastic:

Shale

Answer 18

mixture of:

clay, silt (some sand) sized particles

Question 19

Sedimentary rocks - clastic:

Clays - structure

Answer 19

alumosilicates with sheet structure and different stacking combinations:

1. tetrahedral unit with central Si-atom and surrounding O
2. octahedral unit with central Al and surrounding O atoms and OH groups

Question 20

Sedimentary rocks - clastic:

Clays - examples

Answer 20

Kaolinite (Al)

Illite (K,Al)

Montmorillonite (Ca,Na,Al,Mg,Fe, H2O-layer )

Chlorite (Mg,Al,Fe)

Question 21

Sedimentary rocks - clastic:

Clays - how are exchangeable cations measured ?

Answer 21

by cation exchange capacity (CEC)

Smectite/ Montmorillonite HIGH

Kaolinite LOW

Question 22

Sedimentary rocks - chemical:

Carbonates & Evaporate rocks - Formation

Answer 22

chemical and biochemical precipitation depending on environments:

• typically warm
• shallow
• clear marine water in low latitudes

Question 23

Sedimentary rocks - chemical:

Carbonates & Evaporate rocks - Sources of secondary porosity

Answer 23

• fracturing
• solution
• chemical replacement

Question 24

Sedimentary rocks - chemical:

Carbonates - most abundant carbonate minerals

Answer 24

• calcite CaCO3
• dolomite CaMg(CO3)2

also:

• anhydrite
• chert
• quartz

+ accessory (phosphates etc.)

Question 25

Sedimentary rocks - chemical: Carbonates - post-depositional processes

Answer 25

dissolution cementation recrystallization dolomitization (increasing porosity) replacement

Question 26

Sedimentary rocks - chemical: Carbonates - Classification after Dunham (Kendall in slides)

Answer 26

Picture in Lecture: Mudstone (mud-supported, < 10% grains) Wackestone (mud-supported, > 10 % grains) Packstone (grain-supported, with mud) Grainstone (grain-supported, without mud) Boundstone (bound at deposition, intergrown, lamination)

Question 27

Texture includes ..

Answer 27

grain size size distribution shape packing

Question 28

What does the grain diameter depend on

Answer 28

particles with non-spherical shape depend on technique of determination 1) sieve analysis: minimum cross-sectional axis 2) image or laser scanning: numerical algorithm for representive size distribution

Question 29

Slide 23: Grain size distribution: | well and poorly sorted

Answer 29

well: mainly one size occur poorly: wide range of different sizes

Question 30

Particle size depend on ..

Answer 30

environmental setting tronsporting agent length and time during transport depositional conditions

Question 31

Phi-scale

Answer 31

phi = -log_2(d) with d in mm

Question 32

median grain size

Answer 32

midpoint at d50 (at 50%)

Question 33

grain sorting S_0

Answer 33

how narrow distribution is: S_0 = (d25/d75)^1/2

Question 34

Skewness S_k

Answer 34

symmetry: S_k = (d25*d75)/d50^2

Question 35

Sieving analysis:

Answer 35

sediment pass through series of stacked sieve meshes (by agitation) wet or dry Sieve catch grains larger than mesh size fractions were weighted o get percentages relative to whole sample

Question 36

Atterberg method

Answer 36

by sedimentation or settling measures rate of sedimentation of particles suspended in liquid not useful for < 5 mikrometer

Question 37

Laser diffraction

Answer 37

measures angular dependence of laser light scattered by particles

Question 38

Stereology mean intercept length of a sphere

Answer 38

3D interpretation of 2D cross sections 0.667 as fraction of diameter was Homework

Question 39

Borehole imaging

Answer 39

1. Optical imaging 2. Acoustic imaging 3. Electrical imaging

Question 40

Borehole imaging 1. Optical imaging

Answer 40

Optical & hyperspectral scanning: - > downhole scanning - > core scanning (360 °) - > 3D Channel Spectral data

Question 41

CT-scanning

Answer 41

use a x-ray source -> through object and scanned by detector on other side numelrical agorithm to construct 2D cross section x-ray attenuation proportional to density determination of porosity

Question 42

Classification of rock properties: direc interest for application (4)

Answer 42

- reservoir properties (porosity, saturation, permeability) - geochemical properties (deformation, strength) - mineralogical characteristics (shale content, fractional min. composition) - content of substances of interest (ore content)

Question 43

Classification of rock properties: measured by geophysical methods

Answer 43

(elastic/seismic, density, electical, nuclear)

Question 44

Scalar properties

Answer 44

- porosity - fluid saturation - density - nuclear cross-sections

Question 45

Tensorial properties

Answer 45

- permeability - deformation modulus - strength properties - elastic, electrical, thermal, magnetic properties

Question 46

Routine core (plug) analysis

Answer 46

- Porosity (photo) - permeability (CT scan) - grain density (fluids) - gamma

Question 47

Special core analysis

Answer 47

- capillary pressure - nuclear magnetic resonance - electrical properties - acoustic properties - clay minerals - specific tests

Question 48

isotropic anisotropic homogenious inhomogenious

Answer 48

isotropic-homogeneous: OOO anisotropic-homogeneous: 000 Isotropic-inhomogenieous: °oO Anisotropic-inhomogeneous: 0o0