Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Earth Systems 3209 Unit: 3 Earth’s Materials Reference: Chapters 2, 3, 6, 7; Appendix A & B

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Chemical Sedimentary Rocks Unit 3: Topic 4.5 Focus on....  identifying the processes that form chemical sedimentary rocks.  contrasting precipitates vs. evaporites.  identifying different chemical sedimentary rocks and the environment in which they form.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Chemical Sedimentary Rocks  These rocks form as a result of chemical weathering dissolving chemicals and transporting it in solution. When conditions are right, these dissolved chemicals change back into a solid through the processes of: 1)Precipitation 2) Evaporation  Evaporation and Precipitation often work together. As water evaporates, chemicals in solution will precipitate. Example: Rock Salt (Halite).  These rocks can also form where ground water dissolves chemicals and precipitates the material in certain environments.  An example of this process would be the formation of stalactites and stalagmites.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador vPrecipitates  Process where a change in environmental conditions cause chemicals dissolved in solution, to fall out of solution wich forms a solid material.  Results from a change in environmental conditions, such as: Temperature Concentration Chemical changes  Most common in shallow water environments. ChemicalSedimentary Rocks (Precipitation)

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Examples of chemical sedimentary rocks include: 1)Limestone  10% of all sedimentary rocks (by volume)  Most abundant chemical sedimentary rock  Composed primarily of calcite (calcium carbonate CaCO 3 )  Formed by marine organisms (corals, clams, algae)  Some deposited directly out of ocean or other waters  Most abundant chemical precipitate rock which forms in shallow marine waters. Often contain shell fossils. Chemical Sedimentary Rocks (Precipitation)

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Chemical Sedimentary Rocks (Precipitation) Examples of chemical sedimentary rocks include: 2)Dolomite  CaMg(CO 3 ) 2, Calcium Magnesium Carbonate.  Dolomite appears to form in many different types of environments.  Dolomite is used as an ornamental stone and a concrete aggregate.  It is an important Petroleum reservoir rock.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Chemical Sedimentary Rocks (Precipitation) Examples of chemical sedimentary rocks include: 3) Travertine  A kind of limestone deposited by springs.  Groundwater traveling through limestone beds dissolves calcium carbonate and as this dissolved matter precipitates it builds up travertine deposits.  "Travertine" is sometimes used to mean cavestone, the calcium carbonate rock that makes up stalactites and other cave formations.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador 3)Travertine  Stalactite: icicle-like pendants that hang from the ceilings of caverns and form where water seeps through cracks above.  Stalagmite: mound shaped deposits that form on the floors of caverns and build upwards toward the ceilings. Chemical Sedimentary Rocks (Precipitation)

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador  Evaporites  Process where there is a change in state from a liquid to a gas, water evaporates.  Chemicals dissolved in the liquid (water) are left behind as a solid material.  Most common in marine environments, but can also form in some lakes.  Examples include; Salt (Halite), Gypsum and Sylvite. Chemical Sedimentary Rocks (Evaporites)

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Chemical Sedimentary Rocks (Evaporites) Examples of chemical sedimentary rocks include: 4) Rock Salt  Consist of the mineral Halite.  Forms by evaporation of shallow seas and lagoons that have high concentrations of halite in solution. The mineral precipitates out of solution as the water evaporates.  Common use is table salt and road salt.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Chemical Sedimentary Rocks (Evaporites) Examples of chemical sedimentary rocks include: 5)Rock Gypsum  Consist of the mineral Gypsum.  Forms by evaporation of shallow seas and lagoons that have high concentrations of gypsum in solution. The mineral precipitates out of solution as the water evaporates.  "Common use is plaster and gyproc (drywall).

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador EnvironmentRock Types Shallow Marinegypsum, halite (rock salt), sylvite, limestone, dolomite Deep Marine (Ocean) limestone, dolostone, chert CaveTravertine (stalactites and stalagmites) Summary Chemical Sedimentary Environments

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Example 1: Which is an icicle-like, depositional feature common to cave ceilings? (A) breccia(B) stalactite (C) stalagmite(D) travertine Which is a chemical sedimentary rock? (A) conglomerate(B) limestone (C) sandstone(D) shale

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Example 2: Under which condition would a chemical sedimentary rock form? (A)cementing of sand and pebbles (B)compaction of sand and clay (C)hot chemical fluids changing a minerals composition (D)precipitation of dissolved materials into solid form

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Your Turn... Take the time and complete the following questions... (Solutions to follow) Questions: Using an example, describe the formation of chemical sedimentary rocks.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Solutions... Questions: Answer: Dissolved chemicals in solution (water) can form solid minerals by precipitating out of solution or as a result of evaporation. Example: Salt water has an accumulation of salt dissolved in the oceans. In shallow marine environments, where water evaporates, the salt (halite) precipitates and forms rock salt. Using an example, describe the formation of chemical sedimentary rocks.

Copyright © 2014 All rights reserved, Government of Newfoundland and Labrador Summary... Overview of Points covered:  Chemical Sedimentary rocks include;  Limestone  Dolomite  Travintine  Rock Salt  Rock Gypsum  Chemical Sedimentary environments include;  Shallow Marine  Deep Marine (Ocean)  Caves