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Sedimentary rocks: Why bother?

Sedimentary rocks: Why bother?. Sedimentary processes for economic mineral formation. WEATHERING AND EROSIONAL PROCESSES More soluble materials are removed by intense leaching Less soluble materials are concentrated to form RESIDUAL DEPOSITS Example: Bauxite (aluminum ore).

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Sedimentary rocks: Why bother?

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  1. Sedimentary rocks: Why bother?

  2. Sedimentary processes for economic mineral formation WEATHERING AND EROSIONAL PROCESSES More soluble materials are removed by intense leaching Less soluble materials are concentrated to form RESIDUAL DEPOSITS Example: Bauxite (aluminum ore)

  3. WEATHERING AND EROSIONAL PROCESSES CONTD. Lighter or less dense materials are removed by erosion (“winnowing”) Heavier minerals such as gold, diamond etc. are concentrated as PLACER DEPOSITS on riverbeds Example: Gold deposits in California (Great American gold rush) http://history.sandiego.edu/gen/~jross/goldrush.html

  4. http://www.goldrush.com/~joann/

  5. WEATHERING AND EROSIONAL PROCESSES Sand and gravel deposits by glaciers and rivers Example: Gravel mines in Michigan and Wisconsin http://www.geo.msu.edu/geo333/sand&gravel.html

  6. http://www.geo.msu.edu/geo333/sand&gravel.html

  7. CHEMICAL SEDIMENTARY DEPOSITS Banded Iron formation: or the result of global air pollution 3.8 – 1.8 Billion years ago Commonly accepted explanation for formation indicate introduction of free oxygen in the atmosphere due to photosynthesis Oxygen reacted with iron and deposited iron oxide Example: BIF in the Great Lakes Region

  8. CHEMICAL SEDIMENTARY DEPOSITS CONTD. More saline Less saline EVAPORITE deposits form when shallow marine or saline lakes dry up Common evaporite minerals are Halite (NaCl), gypsum (CaSO4.2H2O), sylvite (KCl) etc. Example: Great Salt Lake, Utah Railway track http://earth.jsc.nasa.gov/sseop/efs/photoinfo.pl?PHOTO=STS51B-35-96

  9. Precipitation from metal-rich fluids Hypersaline waters are produced during lithification processes This water dissolves trace amounts of lead, zinc, copper present in the sediments This solution is produced at 150 – 350º C Ultimately this solution forms metallic sulfide deposits Example: Mines in SW Wisconsin

  10. Biological/mysterious deposits Phosphate deposits in Florida Deep ocean polymetallic nodules (mostly manganese, but can have Ni, Cu, Co, Fe… etc.) And lastly… FOSSIL FUELS!!!!!!

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