Geology Review Chapter 7

What is an example of "Hydrolysis/HydraPon" reaction?

"Dry" Feldspar = Hydrous mineral (clay)

SiO2 Solubility in Water

- 25oC ? small! - 100oC <10ppm - 200oC 2400 ppm - 300oC 0.1 %

Production of Clastic Sedimentary Rocks:

- An example of is Sandstone because of detritus (Loose clasts). 1. Weathering: The grains from which clastic rocks form come from the disintegration of pre-existing bedrock into separate grains due to physical and chemical weathering. Abrasion occurs in this process (the process in which one material grinds away at another). 2. Erosion: The combination of processes that separate clasts from their original substance. Dissolution of outcrop faces in water, producing dissolved ions. 3. Transportation: The ability of a medium to carry sediment depends on its viscosity and velocity. Very fast-moving, turbulent water can transport very coarse clasts (cobbles and boulders), moderately fast moving water can carry only sand and gravel, and slowly moving water carries only silt and mud. Strong winds can move sand and dust, but gentle breeze carry only dust. They are transported by wind, water, or ice. 4. Deposition: The process by which sediment falls out of the medium (When the sediment settle out of wind or moving water). 5. Lithification: The transformation of loose sediment into solid rock through competition and cementation.

Sedimentary Structures:

- Are the structures formed during sediment deposition. - Bedding and Stratification - Ripple Marks/ Dunes/and Cross Bedding (Indicate that layers were deposited in a current),

Why doesn't quartz weather into something else?

- Because it is stable and no reaction occurs.

What is the most common natural acid in rain water:

- Carbonic Acid

What causes low PH in an aqueous solution?

- Carbonic acid breaks down into: (H+) + (HCO3-)

Dolostone:

- Contains mineral dolomite (CaMg[CO3]2) - Forms by a chemical reaction between solid calcite and magnesium-bearing groundwater. This may take place beneath lagoons along a shore soon after the limestone formed or a long time later, after the limestone has been buried deeply.

Mechanical Processes:

- Cracking: -Cracks open up and let fluids in. - React with Minerals at Surfaces. - Crystallized at High Pressure and Temp - Uplifed and Eroded by Low Press and Temp - Internal Stresses in Rocks - or Rock Bursts (open-pit mines)

What Causes Cracking in Hard Rocks?

- Exfoliation of Granites (natural, slow cracking)

What is the most common mineral in granite?

- Feldspar

Sedimentary Rock Texture:

- Fine Grained - Medium Grained - Coarse Grained

How do Aqueous Fluids dissolve Silicates?

- First, silicate Mineral surfaces are never "Dry" Unsatisfied bonds of Mineral Surfaces attract OH and H2O - "Reactions"!

Replacement Chert:

- Forms when other material is replaced by silica, e.g. petrified wood forms when silica rich fluids percolate through dead wood and the silica precipitates to replace the wood. Chert can also form through direct precipitation from silica rich fluids, e.g. agate is formed by the precipitation of silica in voids within a rock. Chert has the general physical properties of quartz.

Terrestrial (Non Marine) Sedimentary Environments:

- Glacial Environments - Mountain Stream Environments - Alluvial- fan Environment: Alluvial-Fan is a gently sloping apron of sediment dropped by an ephemeral stream at the base of a mountain in arid or semiarid regions. - Desert Environments - River Environments - Lake Environments

Organic Sedimentary Rocks:

- Has provided the fuel of modern industry and transportation, for organic chemicals can burn to produce energy. - Two types of organic sedimentary rocks: 1. Coal and 2. Oil Shale. - Coal: Is a black, combustible rock containing between 40% and 90% carbon; the remainder consists of clay and quartz. Coal is formed from plant remains that have been buried deeply. - Oil Shale: Is a shale that contains not only clay but also between 15% to 30% organic material in a form called kerogen which comes from the fats and proteins that made up the living part of plankton or algae.

Travertine (Chemical Limestone):

- Is a form of limestone deposited by mineral springs, especially hot springs. Consists of crystalline calcium carbonate (CaCO3) that precipitates directly from groundwater that has seeped out at the ground surface either into or cold water springs or on the walls of caves.

Coastal and Marine Sedimentary Environments:

- Marine Delta Deposits - Coastal Beach Sands - Shallow- Marine Clastic Deposits - Shallow water Carbonate Environments

Lignite:

- Often referred to as brown coal, is a soft brown combustible sedimentary rock formed from naturally compressed peat. It is considered the lowest rank of coal due to its relatively low heat content.

What are other iron bearing minerals?

- Olivine - Amphibals

Biochemical Limestone:

- Principal compound that makes up limestone is calcium carbonate. - The calcium carbonate is locked into the fossil shells and skeletons of marine organisms. As marine plants and animals die in the ocean, scavengers, waves or currents may break them apart, resulting in biochemical sediment comprised mainly of broken fragments of the original skeletons and shells. - Limestone originates from reef builders such as coral.

What does granite turn into?

- Quartz------ Quartz - K-feldspar----- Quartz, Ions, Clay - Ca-Na feldspar---- Quartz, Ions, Clay - Micas---- Clay, Ions

Abrasion During Transport:

- Subaerial abrasion (dunes) - Ice-transported sediments (Glaciers)

Saltation:

- The movement of hard particles such as sand over an uneven surface in a turbulent flow of air or water.

Chemical Sedimentary Rocks:

- These typically have a crystalline texture, partly formed during their original precipitation and partly when new crystals grow at the expense of old ones through the process of recrystallization. These precipitate from water solutions.

Biochemical Chert:

- This is made from cryptocrystalline quratz - Is formed when the siliceous skeletons of marine plankton are dissolved during diagenesis, with silica being precipitated from the resulting solution.

What drives the cementation of SiO2 (Quartz) into sedimentary rocks?

-Driven by hydrogen protons (Low PH), as potassium ions remain in the solution as salts.

By some estimates, 70% to 85% of all the sedimentary rocks on Earth are: And 15% to 25% are carbonate biochemical or chemical rocks:

-Siliceous or argillaceous clastic rocks. -carbonate biochemical or chemical rocks.

Two types of Biochemical Sedimentary Rocks:

1. Biochemical Limestone 2. Biochemical Chert

Classes of Sedimentary Rocks (Origin):

1. Clastic Sedimentary Rock: Consists of cemented-together clasts, soid fragments and grains broken off of pre-existing rocks. Ex: Sandstone (Loose clasts) 2. Biochemical Sedimentary Rock: Consists of shells grown by organisms. Ex: Limestone 3. Organic Sedimentary Rock: Consists of carbon-rich relicts of cellular material from plants or other organisms. Ex: Coal and Oil Shale 4. Chemical Sedimentary Rock: Comes from minerals that precipitated directly from surface-water solutions. Ex: Rock Salt

What are the three processes of weathering:

1. Mechanical Process: Cracking, Abrasion, Freeze Thaw 2. Biochemical Process: Biochemistry 3. Chemical Process: Reactions of minerals and fluids.

Two categories of depositional environment:

1. Terrestrial 2. Marine

What is the chemical formula for Fe- bearing Pyroxene?

4 (Fe2+)SiO3 + 2 H2O + O2 = 4(Fe3+)O(OH) + 4SiO2 Pyroxene + Water + Oxygen = Goethite" + Quartz hydrated iron mineral (yellow) buff/brown ss

The chemical equation of weathering feldspar.

4 KAlSi3O8 + (4H+) + (2 H2O ) = (4K+) + Al4Si4O10(OH)8 + 8 SiO2 K-feldspar + in soln in soln "Kaolinite" Quartz clay mineral

Sedimentary Basins:

A depression, created as a consequence of subsidence, that fills with sediment.

Stratigraphic Formation:

A sequence of strata that is distinctive enough to be traced as a package across a fairly large region.

Bed:

A single layer of sediment or sedimentary rock with a recognizable top and bottom.

Depositional Sequence:

A succession of strata deposited during a cycle of transgression and regression.

Diagenesis:

All of the physical, chemical, and biological processes that transform sediment into sedimentary rock and that alter the rock after the rock has formed.

Ripple Marks:

Are relatively small elongated ridges that form on a bed surface at right angles to the direction of current flow.

What is the chemical equation of when you weather plagioclase?

Ca-feldspar + H+ + Water = Ca ions in Solution + clay + Quartz.

Intracontinental Basins:

Develop in the interiors of continents, initially because of subsidence over a rift, perhaps over an old rift.

What causes cracking in hard rocks?

Exfoliation of Granites: Mechanical Processes which is when it cracks the rock open allowing fluids in that react with the surface. Mechanical frost wedging.

Passive-Margin Basins

Form along the edges of continents that are not plate boundaries. It is when the ocean rises over the edges of the continent.

Rift Basins:

Form in continental rifts, regions where the lithosphere has been stretched. Imagine pulling on either end of a block of clay with your hands- as the clay stretches, the central region of the block thins and sinks lower than the ends.

Foreland Basin:

Form on the continent side of a mountain belt because the forces produced during convergence or collision push large slice of rock up faults and onto the surface of the continent.

What is the chemical formula for carbonic acid:

H2O + CO2 = H2CO3

Quartz in Water:

H4SiO4

What are the reactions for when you are converting hematite to goethite? Not sure

Hydration and reduction reaction which is when you go from Fe2 to Fe3. 2 Fe3+O(OH) = Fe2+2O3 + H2O

What type of reactions is the weathering of Iron bearing pyroxene?

Hydration reaction and Oxidation Reaction

Dry pyroxene weathers into?

Hydrous fine-grained mineral

Cross Bed:

Internal laminations in a bed, inclined at an angle to the main bedding; cross beds are a relict of the slip far of dunes or ripples.

Sedimentary Rock:

Is rock that forms at or near the surface of the Earth in one of several ways: By the cementing together of loose fragments/grains, or by the cementing together of shells and shell fragments. These tell the history of the Earth.

Turbidities:

Is the geologic deposit of a turbidity current, which is a type of sediment gravity flow responsible for distributing vast amounts of clastic sediment into the deep ocean. These are triggered by earthquakes or storms.

Mud Cracks:

Is when mud layers dry up after deposition, it then cracks into roughly hexagonal plates that typically curl up at their edges. These indicate that the sediment layer was exposed to the air and dried out on occasion.

Dune:

Looks like a ripple but is larger. It is a pile of sand generally formed by deposition from the wind.

Cross Beds and Dunes:

Only form in a current.

Bedding or stratification:

Overall arrangement of sediment into a sequence of beds. Its the layering and stratification in sedimentary rocks. Strata looks like like bands or stripes across a cliff face.

What are the reactions for when you are converting goethite to hematite? Not sure

Oxidation and dehydration reactions which is when you go from Fe3 to Fe2. 2 Fe3+O(OH) = Fe2+2O3 + H2O

Transgression:

The inland migration of shoreline resulting from a rise in sea level. Terrestrial sediments are progressively buried by coastal sediments, and then coastal sediments are buried by deeper-water sediment.

Regression:

The seaward migration of a shoreline caused by a lowering of sea letter.

Subsidence:

The vertical sinking of the Earth's surface in a region, relative to a reference plane.

Evaporites:

Thick salt deposits that form as a consequence of precipitation from saline water. - When 80% of seawater trapped in a bin evaporates, gypsum forms, and when 90% of the water evaporates, halite precipitates.