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PetrologyPetrology
The study of the properties of rocks and the The study of the properties of rocks and the
processes behind their formationprocesses behind their formation
Recognition and description of rocksRecognition and description of rocks
Interpretation of their origin and historyInterpretation of their origin and history
InstructorInstructor
Michael F. SheridanMichael F. Sheridan email:email:
• [email protected]@geology.buffalo.edu
Homepage:Homepage:• http://www.eng.buffalo.edu/~mfshttp://www.eng.buffalo.edu/~mfs
Office hours:Office hours:• We & Th 1:00-2:00 PMWe & Th 1:00-2:00 PM
FundamentalsFundamentals
ClassificationClassification
Changing States (Equilibrium)Changing States (Equilibrium)
Plate Tectonics & PetrologyPlate Tectonics & Petrology
ThermodynamicsThermodynamics
KineticsKinetics
Magmatic Rock BodiesMagmatic Rock Bodies
Study of rocks in hand sampleStudy of rocks in hand sample
Descriptive PetrochemistryDescriptive Petrochemistry
Origin and evolution of magmasOrigin and evolution of magmas
Interpretative PetrochemistryInterpretative Petrochemistry
Study of rocks in hand sampleStudy of rocks in hand sample
FabricFabric
Rock forming mineralsRock forming minerals
ClassificationClassification
Sequence of mineral formationSequence of mineral formation
Degree of perfection of formDegree of perfection of form
Inclusion within other mineralsInclusion within other minerals
Chemical zonationChemical zonation
Signs of deformationSigns of deformation
Secondary growthSecondary growth
Alteration to secondary mineralsAlteration to secondary minerals
Rock forming mineralsRock forming minerals
FeldsparsFeldspars QuartzQuartz Pyroxenes Pyroxenes OlivinesOlivines AmphibolesAmphiboles MicasMicas FeldspathoidsFeldspathoids
ClassificationClassification
LeucocraticLeucocratic
FelsicFelsic
SilicicSilicic
MaficMafic
UltramaficUltramafic
Rock SuitesRock Suites
Mafic and ultramafic Mafic and ultramafic
Calc-alkalineCalc-alkaline
Highly alkalineHighly alkaline
Descriptive PetrochemistryDescriptive Petrochemistry
Chemical analysesChemical analyses
• Major elementsMajor elements
• Trace elementsTrace elements
Relation of chemistry to mineralogyRelation of chemistry to mineralogy
Chemical classificationChemical classification
Silica concentrationSilica concentration
• Acid >66%Acid >66%
• Intermediate 52-66%Intermediate 52-66%
• Basic 45-52%Basic 45-52%
• Ultrabasic <45%Ultrabasic <45%
Silica saturationSilica saturation
OversaturatedOversaturated
• compatible with quartzcompatible with quartz
SaturatedSaturated
• Neither undersaturated minerals nor quartzNeither undersaturated minerals nor quartz
UndersaturatedUndersaturated
• undersaturated mineralsundersaturated minerals
Alkali/Aluminum saturationAlkali/Aluminum saturation
Relative to feldspar compositionRelative to feldspar composition
• NaAlSiNaAlSi33OO88
PeralkalinePeralkaline
PeraluminousPeraluminous
Calc-alkalineCalc-alkaline
CIPW normCIPW norm
DefinitionDefinition
How calculatedHow calculated
Use in classificationUse in classification
Chemistry of rocksChemistry of rocks
Major elementsMajor elements
Trace elementsTrace elements
CIPW normCIPW norm
From Mineral Composition to From Mineral Composition to Rock CompositionRock Composition
Determine the minerals presentDetermine the minerals present
estimate their abundanceestimate their abundance
Calculate the rock composition using proper Calculate the rock composition using proper
weightingsweightings
Interpretative PetrochemistryInterpretative Petrochemistry
Models of crystallizationModels of crystallization
Concepts of magma movementConcepts of magma movement
Secondary alterationSecondary alteration
Ultramafic rock bodiesUltramafic rock bodies
Petrography of gabbroic and ultramafic Petrography of gabbroic and ultramafic
rocksrocks
Nature of PlutonsNature of Plutons
Oceanic subalkaline basaltic to ultramafic Oceanic subalkaline basaltic to ultramafic
associationsassociations
OphiolitesOphiolites
Petrography of gabbroic and Petrography of gabbroic and ultramafic rocksultramafic rocks
GeneralGeneral• phaneritic grain sizephaneritic grain size• may be nearly monomineralicmay be nearly monomineralic
– PyroxenePyroxene– OlivineOlivine– PlagioclasePlagioclase
FabricFabric• Slow sequential growthSlow sequential growth• Hypidiomorphic granularHypidiomorphic granular
Petrography of gabbroic and Petrography of gabbroic and ultramafic rocksultramafic rocks
ClassificationClassification
AlterationAlteration
• deuteric and hydrothermal alterationdeuteric and hydrothermal alteration
• SerpentineSerpentine
• Secondary iron oxideSecondary iron oxide
• brucite & talcbrucite & talc