Sedimentary/Metamorphic Rocks Flashcards
Generating Sediment
1.) Weathering
2.) Erosion
Weathering
Surface or near-surface in-place breakdown of pre-existing rocks by physical and chemical processes
-more cracks/surface area=more to react with water or carbonic acid
Erosion
Breaking off/ Removal of Rock or sediment
-Grinding away and removal of the Earths surface materials by moving water, air, or ice
Physical Weathering
Joints-Naturally formed fracture in a rock with no displacement
Causes:
1.) Frost/Salt wedging
-expansion of water as it freezes
-formation of salts that expand the crack
2.) Biological Processes
-plant/tree roots growing in rock cracks which expand them
-Lichen which excrete organic acids (oxalic acid) can dissolve minerals (chemical weathering done by organism)
Chemical Weathering
1.) Dissolution: Water or weak carbonic acid dissolves minerals
2.) Hydrolysis: Breakdown of a mineral to a second mineral due to reacting with H2O or carbonic acid
(How Feldspar breaks down)
Clastic
Composed of fragments or grains derived from the breakdown of other rocks, later cemented together
Breccia: Angular clasts-not transported far
(deposited at alluvial fans)
Conglomerate: Rounded clasts-transported far; tumbled
(found at bends in rivers)
How are Sedimentary Rocks Formed?
1.) weathering
2.) Erosion
3.) Transportation
4.) Deposition
5.) Lithification/Diagenesis
Diagenesis
All physical, chemical, and biological processes that transfer sediment into sedimentary rocks and that alter the rock after the rock has formed.
Biochemical
Formed from material produces by living organisms
Biochemical Limestone:
-Calcium Carbonate from coral or shells
Chalk=form of limestone
Chert=Hard, dark, opaque rock composed of silica with amorphous or microscopic fine-grained textures.
Depositional environment=shallow and deep sea deposits (Where reefs and plankton would be)
Coal? Oil?
Organic Sedimentary
Formed from carbon-rich relicts of organisms
coal=vascular plant material
oil shale=clay + organic material, plankton (deep marine or lake; requires heat to form while fossilized)
Chemical
1.) Evaporites-salt deposits formed by precipitation of saline water (salt lakes)
2.) Travertine-chemical precipitated CaCO3
3.) Gypsum- Large crystals forming (CaSO4 + H2O)
Types of Sedimentary Rocks
1.) Clastic
2.) Biochemical
3.) Organic
4.) Chemical
Deposition Environments
Non-Marine:
*Clastic-
conglomerate=River Channel
Breccia=Alluvial Fans
Quartz + Sandstone= Dunes
Siltstone/Shale=Lakes and Floodplains
Marine:
Quartz sandstone= beaches and sand shelves
*Organic
-Oil/Shale=deep marine/lake
-Coal=Swamps
*Chemical
-evaporites=salt lakes
-Gypsum=desert
caves
Sedimentary Structures
1.) Bedding
2.) Ripple Marks and Cross Bedding
3.) Mud-Cracks
Transgression
Sea-level rise
Regression
Sea-level fall
Metamorphic Rocks
Rock changes physically or chemically by heat or pressure
Shale-> Schist
Protolith
original rock from which a metamorphic rock forms
(can be igneous or sed)
Effects of Metamorphism
1.) Recrystallization
2.) Metamorphic rxns/Phase changes
3.) Foliation
Recrystallization
Change in grain size due to metamorphism (Minerals remain the same)
Sandstone-> Quartzite
Metamorphic Rxns/Phase Change
Change i rocks minerology due to pressure and temp change
(New minerals grow through solid state rxns)
Shale-> Schist
Foliation
Development of layering due to preferential alignment of minerals as a result of stress on the rock \
(Can occur during new mineral growth or by realignment of existing minerals)
Three metamorphic settings
1.) Contact Metamorphism
2.) Regional Metamorphism
3.) Subduction-Related Metamorphism
Contact Metamorphism
Rock heated by intruding magma
-Low pressure, High temp
-often no foliation
Regional Metamorphism
Low pressure->High pressure
-Mountain belt
Subduction-Related Metamorphism
Blue Schist
High pressure, Low temp
Original Shale Minerals
Quartz, K-Feldspar, Plagioclase, Clay
Minerals produced by metamorphism of Shale
Chlorite, muscovite, biotite, garnet, staurolite, sillimanite
