مواد و معدنی تشکیل شده توسط هوازدگی

مواد و معدنی تشکیل شده توسط هوازدگی

اسلاید 1: Minerals formed by weathering

اسلاید 2: Sedimentary Processes1) Weathering & erosion2) Transport & 3) deposition4) Lithification

اسلاید 3: Weathering: decomposition and disintegration of rock Product of weathering is regolith or soil Regolith or soil that is transported is called sediment Movement of sediment is called erosion

اسلاید 4: Weathering ProcessesChemical Weathering- Decomposition of rock as the result of chemical attack. Chemical composition changes. Mechanical Weathering -Disintegration of rock without change in chemical composition

اسلاید 5: Mechanical WeatheringFrost wedgingAlternate heating and coolingDecompression causes jointing

اسلاید 6: Chemical Weathering ProcessesHydrolysis - reaction with water (new minerals form)Oxidation - reaction with oxygen (rock rusts)Dissolution - rock is completely dissolvedMost chemical weathering processes are promoted by carbonic acid:H2O +CO2 = H2CO3 (carbonic acid)

اسلاید 7: Oxidation can affect any iron bearing mineral, for example, ferromagnesian silicates which react to form hematite and limoniteOxidation

اسلاید 8: Oxidation of pyrite and other sulfide minerals forms sulfuric acid which acidifies surface water and rainPyrite + oxygen + water = sulfuric acid + goethite(iron sulfide) (iron oxide)

اسلاید 9: HydrolysisFeldspar + carbonic acid +H2O= kaolinite (clay) + dissolved K (potassium) ion + dissolved bicarbonate ion+ dissolved silicaClay is a soft, platy mineral, so the rock disintegrates

اسلاید 10: Products of weatheringClay minerals further decompose to aluminum hydroxides (bauxite) and dissolved silica.

اسلاید 11: Controls on rates of weatheringRelative resistance of primary minerals to chemical weatheringClimate – especially:availability of water (for chemical weathering), temperature (increases reaction rates), and vegetation (which increases the availability of carbonic acid)

اسلاید 12: A soil profile develops slowly over time

اسلاید 13: Soil classification 1) Laterite or oxisol Forms in a hot, humid climate. Soil is deep red, hard and infertile. Plants recycle nutrients in a thin A and O horizon.

اسلاید 14: Deforestation removes the fertile organic layer. The underlying soil is infertile, dries to brick-like hardness when it dries out, and is difficult to cultivate. Aluminum (from bauxite) and iron (from limonite) can be mined from these soils.

اسلاید 15: Soil classification2) Alfisols and mollisols: Form in warm or cool, temperate climates. Soil is grey and clay-rich, fertile. Alfisols are forest soils, mollisols form in grasslands

اسلاید 16: Soil map of worldGreens – Alfisols & mollisolsRed – OxisolsTan - Aridosols

اسلاید 17: Minerals formed by weathering: (pages 191-192)Clay minerals: kaolinite, smectite (Na, Ca), illite (K) (pages 255-256)Aluminum oxides and hydroxides: gibbsite, diaspore, boehmite (consituents of bauxite) (pages 371-374)Iron oxides and hydroxides: hematite, goethite, lepidocrosite, limoniteMn oxides and hydroxides (bog ores or wad): pyrolusite, romanechite, manganite, other