Cours petrographie-sedimentaire
Transcript of 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