Cours petrographie-sedimentaire

Sedimentary Petroology

SedimentologyThe study of the processes that erode, transport and

deposit sedimentsSedimentary Petrology

The study of the characteristics and origin of

sedimentary rocks.Stratigraphy

The study of the origin, relationship, and extent of

rock layers (strata).

Sedimentary Rocks on Earth

ShaleSandstoneSiltstone LimestoneConglom.

What do Sedimentary Rocks Record?

Magma

Igneous Rocks

Sedimentary Rocks

Metamorphic Rocks

Sediment

Crystallization Melting

Metamorphism

Lithification

Weathering

Erosion

Transport

Deposition

What do Sedimentary Rocks Record?

•Source (Provenance) of sediment•Erosion and Transport Agent•Depositional Environment•Paleogeography/Tectonic Setting•Diagenesis (what happened after deposition)

Rock Identification is based on:

•CompositionWhat minerals make up the rock?

•TextureWhat is the shape, size and orientation of the mineral grains that make up the rock?

Types of Sedimentary Rocks

Detrital Chemical

OrganicClasticTexture Crystalline

Texture

Detrital Rock Composition

Detrital Rocks• Lithic Fragments

• Quartz• Clay Minerals• Fossil Fragments

• Rust Minerals• Orthoclase• Muscovite / Biotite

Note About Sediment Composition:Weathering

The sediments that make up sedimentary rocks are produced by:

Mechanical & Chemical Weathering

Mechanical Weathering

Chemical Weathering

MineralStability

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.)

Interpretation of Composition

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

Note About What Causes Detrital

Rock Color•Grain SizeSmaller is often darker

•CompositionCarbon - black or brownQuartz - tan, clear, whiteOrthoclase - orange

•Depositional EnvironmentIron on land - redIron in deep, oxygen poor water - green

MajorMajor SedimentarySedimentary RockRock TypesTypes

• SiliciclasticSiliciclastic• VolcaniclasticVolcaniclastic• CarbonatesCarbonates (evaporites/chemical,(evaporites/chemical, non-non-skeletal,skeletal, skeletal)skeletal)

SiliciclasticSiliciclastic SedimentarySedimentary RocksRocks

• QQ == quartzquartz• FF == feldsparsfeldspars• RR == lithiclithic fragmentsfragments

•   (includes(includes chert)chert)

SedimentarySedimentary RocksRocks

• ““Mature”Mature” rocksrocks• (mineralogicall(mineralogicallyy stable)stable) EnrichedEnriched inin quartzquartz andand

• clayclay mineralsminerals

SiliciclasticSiliciclastic SedimentarySedimentary RocksRocks

• ““Immature”Immature” rocksrocks• (mineralogically(mineralogically unstable)unstable) EnrichedEnriched inin feldsparsfeldspars andand

• unstableunstable rockrock fragmentsfragmentsGrainGrain roundingrounding 

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

MatrixMatrix versusversus CementCement

• Cement:Cement: aa chemicalchemical precipitateprecipitate betweenbetween grainsgrains formedformed fromfrom pore-waterpore-water longlong afterafter depositiondeposition

MatrixMatrix versusversus CementCement

MatrixMatrix HeterogeneousHeterogeneous ChemicallyChemically impureimpure DrapesDrapes overover grainsgrainsXNXNPredatesPredates cementscementsGenerallyGenerally darkdark inin colorcolor

MatrixMatrix versusversus CementCement• MatrixMatrix• ™™ HeterogeneousHeterogeneous• ™™ ChemicallyChemically impureimpure• ™™ DrapesDrapes overover grains*grains*• ™™ PredatesPredates cementscements• ™™ GenerallyGenerally darkdark inin color*color*•

CementCement™™ 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

Thin-sectionThin-section PhotomicrographsPhotomicrographs

LES MINERAUX EN CATODOLUMENESCENCE