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The Rock Cycle. Sedimentary Processes 1 2) & 3) Sediments are transported and deposited 4.

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Presentation on theme: "The Rock Cycle. Sedimentary Processes 1 2) & 3) Sediments are transported and deposited 4."— Presentation transcript:

1 The Rock Cycle

2 Sedimentary Processes 1 2) & 3) Sediments are transported and deposited 4

3 Products of weathering PrimaryResidualDissolved Minerals MineralsIons FeldsparClay mineralsK +, Ca +2, Na + Aluminum hydroxide Fe-Mg mineralsHematite &Mg +2 Limonite QuartzQuartzSilica PrimarySolids thatIons that are carried Minerals remain in soil away in water ----------Detrital sediments------------------Chemical & biochemical sediments

4 Types of sediment Detrital – mineral & rock fragments Chemical – halite (NaCl) crystals that precipitate from water Biochemical – shells made of calcite (CaCO 3 ) by organisms that extract the ions from water

5 Detrital sedimentary rocks- classified by grain size differences Conglomerate Breccia Sandstone Shale All these rocks have clastic textures – the rocks are composed of particles (fragments) that are cemented together

6 Detrital sediments are sorted by the processes of transportation and deposition Well sortedPoorly sorted

7 Sands and sandstones can be used to interpret the erosional history of an area and the kinds of rocks that were eroded Well- sorted Poorly sorted “Mature” sediments have little feldspar. This means that the sediment was derived from weathered rocks or that the feldspar decomposed during transportation in water.

8 The same diagram is used to interpret the provenance (source rocks) of sediments

9 Placer deposit– accumulation of sand or gravel containing minerals that are highly resistant to chemical attack and economically valuable - gold, platinum, ilmenite, rutile, zircon, diamond, garnet, magnetite, corundum, monazite. These and other chemically resistant minerals are widely used to indicate the provenance of sediments, e.g. kyanite, sillimanite, staurolite indicate that metamorphic rocks were eroded. Diamonds indicate kimberlite; gold indicates hydrothermal veins, etc.

10 Chemical and biochemical sedimentary rocks Limestones – composed of calcite Travertine Coquina Chalk

11 Deep ocean sediments are mainly fine-grained biochemical sediment called oozes, with some hydrogenous (chemical) and terrigenous (wind or water borne) detrital sediment

12 Calcareous & siliceous ooze Manganese nodules are hydrogenous - they precipitate from deep ocean water when the Mn oxidizes: Mn +2 (dissolved) + O 2 + 2e - = MnO 2 (pyrolusite)

13 Banded Iron Formations – ancient (>2.5 billion year old) sedimentary deposits of iron- bearing minerals. These indicate that Earth’s early atmosphere was too poor in oxygen to oxidize iron at the site of weathering. Dissolved iron was transported in water: 4Fe +2 (dissolved) + 3O 2 = 2Fe 2 O 3 (hematite)

14 Phosphates form in shallow marine environments where dissolved PO 4 -3 is carried by upwelling of deep ocean water. These areas are biologically productive - many fossils are found, especially bone material.

15 Phosphate Mining of the Bone Valley Formation in Florida

16 Shallow basin with high rate of evaporation – Gulf of Mexico, Persian Gulf, ancient Mediterranean Sea, Red Sea Sequence is: calcite, gypsum, halite with increasing evaporation Evaporite minerals

17 Evaporites Gypsum Halite Seawater evaporation: 1)Calcite 2)Gypsum 3)Anhydrite 4)Halite (95% evaporation) 5)Sylvite 6)Other rare minerals Dolomite may form afterward by reaction of Mg +2 with calcite Continental waters: Borax & borates Nitrates

18 Salt dome Sulfur is produced by sulfate reducing bacteria which consume the oxygen in gypsum or anhydrite

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