Cours petrographie-sedimentaire

1. Sedimentary Petroology

2. Sedimentology
The study of the processes that erode,
transport and deposit sediments
Sedimentary Petrology
The study of the characteristics and origin of
sedimentary rocks.
Stratigraphy
The study of the origin, relationship, and
extent of rock layers (strata).

3. Sedimentary Rocks on Earth
Shale Sandstone Siltstone LimestoneConglom.

4. What do Sedimentary Rocks Record?
Magma
Igneous Rocks
Sedimentary Rocks
Metamorphic Rocks
Sediment
Crystallization Melting
Metamorphism
Lithification
Weathering
Erosion
Transport
Deposition

5. What do Sedimentary Rocks Record?
•Source (Provenance) of sediment
•Erosion and Transport Agent
•Depositional Environment
•Paleogeography/Tectonic Setting
•Diagenesis (what happened after deposition)

6. Rock Identification is based on:
• Composition
What minerals make
up the rock?
• Texture
What is the shape, size
and orientation of the
mineral grains that
make up the rock?

7. Types of Sedimentary Rocks
Detrital Chemical
Organic
Clastic
Texture Crystalline
Texture

8. Detrital Rock Composition
Detrital Rocks
• Lithic Fragments
• Quartz
• Clay Minerals
• Fossil Fragments
• Rust Minerals
• Orthoclase
• Muscovite / Biotite

9. Note About Sediment Composition:
Weathering
The sediments that make up sedimentary rocks are produced by:
Mechanical & Chemical Weathering

10. Mechanical Weathering

11. Chemical Weathering

12. Mineral
Stability

13. Products of Weathering
• Lithic (Rock) Fragments
(granite, basalt,schist, etc.)
• Dissolved Ions
(Calcium, Potassium, Sodium, etc.)
• Rust Minerals (Hematite, Goertite, etc.)
• Clay Minerals
(Bentonite, Montmorillonite, etc.)
• Residual Minerals
(Quartz, Orthoclase, Muscovite, etc.)

14. Interpretation of Composition
Detrital Rocks:
• Source of Sediment (Provenance)
• Exposure to Weathering
(Distance of Transport)
(Type of Climate)

15. Note About What Causes
Detrital Rock Color
• Grain Size
Smaller is often darker
• Composition
Carbon - black or brown
Quartz - tan, clear, white
Orthoclase - orange
• Depositional Environment
Iron on land - red
Iron in deep, oxygen poor water - green

16. MajorMajor SedimentarySedimentary RockRock TypesTypes
• SiliciclasticSiliciclastic
• VolcaniclasticVolcaniclastic
• CarbonatesCarbonates (evaporites/chemical,(evaporites/chemical, non-non-
skeletal,skeletal, skeletal)skeletal)

17. SiliciclasticSiliciclastic SedimentarySedimentary RocksRocks
• QQ == quartzquartz
• FF == feldsparsfeldspars
• RR == lithiclithic fragmentsfragments
• (includes(includes chert)chert)

18. SedimentarySedimentary RocksRocks
• ““Mature”Mature” rocksrocks
• (mineralogically(mineralogically
stable)stable) EnrichedEnriched inin
quartzquartz andand
• clayclay mineralsminerals

19. SiliciclasticSiliciclastic SedimentarySedimentary RocksRocks
• ““Immature”Immature” rocksrocks
• (mineralogically(mineralogically
unstable)unstable) EnrichedEnriched inin
feldsparsfeldspars andand
• unstableunstable rockrock fragmentsfragments
GrainGrain roundingrounding

20. MatrixMatrix versusversus CementCement
• Matrix:Matrix: fine-grained*fine-grained* materialmaterial depositeddeposited
simultaneouslysimultaneously withwith
• largerlarger particles.particles. GenerallyGenerally appearsappears asas
darker-coloureddarker-coloured detritusdetritus betweenbetween grainsgrains

21. MatrixMatrix versusversus CementCement
• Cement:Cement: aa chemicalchemical precipitateprecipitate betweenbetween
grainsgrains formedformed fromfrom pore-waterpore-water longlong afterafter
depositiondeposition

22. MatrixMatrix versusversus CementCement
MatrixMatrix
HeterogeneousHeterogeneous
ChemicallyChemically impureimpure
DrapesDrapes overover grainsgrains
XNXN
PredatesPredates cementscements
GenerallyGenerally darkdark inin colorcolor

23. MatrixMatrix versusversus CementCement
• MatrixMatrix
• ™™ HeterogeneousHeterogeneous
• ™™ ChemicallyChemically impureimpure
• ™™ DrapesDrapes overover grains*grains*
• ™™ PredatesPredates cementscements
• ™™ GenerallyGenerally darkdark inin color*color*
•
™™ HomogeneousHomogeneous
™™ ChemicallyChemically purepure
™™ LinesLines porespores
™™ SpecificSpecific fabricsfabrics (acicular,(acicular,
drusy,drusy, overgrowthsovergrowths etc.)etc.)
™™ MultiphasedMultiphased
™™ ZonedZoned
CementCement
™™ HomogeneousHomogeneous
™™ ChemicallyChemically purepure
™™ LinesLines pores*pores*
™™ SpecificSpecific fabricsfabrics
™™ MultiphasedMultiphased
™™ ZonedZoned

24. Thin-sectionThin-section PhotomicrographsPhotomicrographs

30. LES MINERAUX EN
CATODOLUMENESCENCE