What is limestone?
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Transcript of What is limestone?
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What is limestone?
Limestone = a biochemical sedimentary rock made up mostly of calcium carbonate
MineralCrystal system Formula Remarks
Calcite Rhombohedral CaCO3 Dominant limestone mineral, especially in rocks older than Cenozoic
Aragonite
Orthorhombic CaCO3 Dominant mineral in Recent carbonate sediments; alters readily to calcite
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How do limestones form?Most limestones are simply the cemented remains of marine shellsLimestone “anatomy” Grains
Skeletal particles, ooids, peloids Lime mud
Microscopic crystals produced by calcareous algae and through abrasion of larger particles
Cement Inorganically precipitated CaCO3 crystals
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Skeletal grains
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ooids
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peloids
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Lime mud
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Calcite cement
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Factors affecting precipitation of CaCO3 in sea water
Factor Type of change Physical effect Effect on CaCO3
Temperature Increase Loss of CO2, increase in pH
Increase precipitation
Pressure Decrease Loss of CO2, increase in pH
Increase precipitation
Salinity Decrease Decrease activity of “foreign” cations
Increase precipitation
Photosynthesis Removes CO2 from sea water; pH increases
Increase precipitation
Bacterial activity
Catalyzes CaCO3 precipitation Increase precipitation
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Where do limestones form?
Because CaCO3 precipitates most readily in warm, well lit, agitated water of normal marine salinity…..most limestones form in shallow, tropical depositional environments e.g., Bahamas, central America, Persian
Gulf, NW shelf of Australia, Great Barrier Reef, Malaysia, Indonesia, etc.
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Modern CaCO3 depositional environments
*Note: Although cool water carbonatesAre forming in many places, they arehighly prone to dissolution and thereforedo not become major limestone accumulations
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Caicos Platform
high-energysand shoals
Prevailing
winds
Reef tract
Quiet water
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North America during the Devonian Period
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Iowa during the Devonian Period
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What are limestone products?
Whole rock Crushed limestone Dolomitic limestone
Burned lime (calcium oxide) High calcium lime Dolomitic lime
Hydrated lime (calcium hydroxide)
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How is limestone used?
Construction Soil stabilization Flue Gas DesulfurizationSteel Production (flux for blast furnaces)Glass ProductionWater Treatment Waste TreatmentPaper Production (filler) Chemical Production Masonry, Mortars and Other Building Materials