GEOL MIDTERM 2 Flashcards
1
Q
The nature of the atomic bonds controls the characteristics of a mineral. True or false?
A
True.
2
Q
Diamond and graphite are both made entirely or carbon, so what makes them different?
A
Their structure is different.
3
Q
What is a tetrahedra bond?
A
When one atom is bound with 4 other atoms.
4
Q
What does polymorph describe?
A
When 2 minerals have the same composition, but a different structure.
5
Q
What are the 12 physical properties we can use to determine an exact mineral?
A
Colour
Streak
Luster
Hardness
Specific Gravity
Crystal Habit
Fracture/cleavage
Feel
Taste
Magnetic properties
Chemical reaction
Fluorescence.
6
Q
What is an anhedral crystal?
A
A crystal that’s grown in a tight space with no crystal faces.
7
Q
What’s a euhedral crystal?
A
A crystal that’s grown in an open cavity with good crystal faces.
8
Q
How do ionic bonds form?
A
By electrostatic attraction between an anion and a cation. Atoms bond because they want to reach a stable state.
9
Q
What are covalent bonds?
A
Where atoms share electrons. When orbitals of 2 atoms overlap and have no more than 2 electrons combined. The greater the overlap, the greater the bond.
10
Q
How are metallic bonds characterized?
A
Valence electrons are free to move from atom to atom throughout the crystal structure; they’re weakly held together. The metals are soft and malleable.
11
Q
How many minerals have been found on earth?
A
Over 4000.
12
Q
How are minerals classified?
A
By their dominant anion.
13
Q
What is the most dominant substance in almost the entire crust and mantle of the earth?
A
Silicates. They’re the first class of minerals.
14
Q
What is the second mineral class? What are their characteristics?
A
Oxides. Metal cations are bonded to oxygen. The most dominant ion is oxygen.
15
Q
What are banded ion formations?
A
A type of sedimentary rock that consists of alternating layers of ion oxides and iron-poor chert.
16
Q
What is the third mineral class? What are their characteristics?
A
Sulfides. Metal cations bound to a sulfide anion.
17
Q
What are metal ores?
A
Naturally occurring rocks/sediments that contain metals/metal compounds in sufficient amounts.
18
Q
What is the 4th mineral class? What are their characteristics?
A
Sulfates. They often form by evaporation of seawater.
19
Q
What is the most abundant halogen in earth’s crust?
A
Fluorine.
20
Q
What is a halogen?
A
Any of the 6 non-metallic elements.
They exhibit similar chemical behaviour and share properties with their compounds.
21
Q
What are halides?
A
Compounds that contain a halogen atom and one or more other elements.
They’re the 5th mineral class.
22
Q
What is the 6th mineral class?
A
Native metals: Pure metals
23
Q
What’s the 7th mineral class? What can they do?
A
Carbonates.
Can bond with cations, generally forming insoluble compounds.
24
Q
What is the 8th mineral class? What are its characteristics?
A
Silicate minerals.
Most dominant on earth.
Made of oxygen and silicone.
Also called the silicon-oxygen tetrahedron: 4 oxygen atoms are bonded with a central silicone atom.
25
What is a covalent bond? Why does it happen?
A chemical bond that involves the sharing of electron pairs between atoms.
Atoms bond because they want to obtain a stable electronic configuration.
26
How many subgroups of silicate minerals are there? How do they vary?
There's 5.
They vary by how silica tetrahedra share oxygen. (The amount of shared oxygen determines the Si:O ratio.
27
What are the 5 types of silicate minerals and their characteristics?
1. Independent Tetrahedra. Cations link around 2 or 3 tetrahedra, and the silica tetrahedra doesn't share oxygens.
2. Single Chains. A silica tetrahedra links to share 2 oxygens. 2 of the 3 oxygens are bound together to other tetrahedras. Ratio is 1:3
3. Double Chains. Silica tetrahedra alternates between sharing 2 and 3 oxygens. 2:7.
4. Sheet Silicates. Silica tetrahedra shares 3 oxygens, creating 2D flat sheets. They share oxygens at the base. One direction of perfect cleavage. 4:11.
5. Framework Silicates. All 4 oxygens in each silica tetrahedron are shared. 1:2.
28
What are the 5 ways minerals can form? Explain and give an example.
1. Solidifaction from a melt. Crystals grow when the melt cools, and liquid freezes to form a solid. (EX, as lava cools, minerals start to crystallize).
2. Precipitation from a solution. Seeds form when a solution becomes saturated. (EX, evaporating water leaves salt behind).
3. Solid-state diffusion. Chemical reactions at different temperature and pressure conditions result in new minerals at the expense of the old. Also known as metamorphism; if you change the structure, you change the mineral.
4. Biomineralization. (EX, Skeletons of dinosaurs).
5. Precipitating directly from a gas. (EX, When volcanic gases are releases, they can cool rapidly and undergo chemical changes which results in solid mineral crystals.
29
What is a 'seed' when talking about the formation of a mineral?
Microscopic crystals grow by bonding ions and molecules in a liquid solution to a pre-existing solid surface.
30
What is the mineral formation process, starting with a seed?
Atoms migrate to the seed and attach to its outer face. Growth moves the faces outward from the centre. The shape reflects the crystal's atomic order.
They grow from the centre outwards, and when they touch each other, it deforms the faces.
31
What are the 3 mineral destruction processes?
1. Melting. (Heat breaks the bonds holding atoms together).
2. Dissolving. (Solvents break atomic bonds).
3. Chemical Reactions with other Minerals. (Reactive minerals break bonds). Metamorphism.
32
What is the difference between a gemstone and a gem?
A gemstone is a mineral with special value, and a gem is a cut and polished stone that's created for jewelry.
33
How deep are diamonds found in the upper mantle?
Around 150 km deep.
Pure carbon is compressed into the diamond structure, and they're found in kimberlite pipes.
34
What are rocks?
Naturally occurring solid aggregates of minerals.
35
What is igneous rock? How does it form? What's an example?
It's the melting of rocks in the hot, deep crust and upper mantle.
It forms through crystallization
EX, Granite.
36
What is a sedimentary rock? How does it form? What's an example?
It's the weathering and erosion of rocks exposed at the surface.
It forms through deposition, burial, and lithification.
EX, sandstone.
37
What's a metamorphic rock? How does it form? What's an example?
Changing a sedimentary rock into a different type of rock.
It is rocks under high pressures and temperatures in the deep crust and upper mantle.
It forms through the recrystallization of new minerals in a solid state.
EX, Gniess.
38
How do extrusive igneous rocks form? Example?
When lava erupts at the surface and cools rapidly. They're fine-grained/glassy-textured rocks.
EX, Basalt.
39
How do intrusive igneous rocks form? Example?
When magma intrudes into unmelted rock below the surface and cools slowly. The slow cooking allows large crystals to grow.
They're coarse-grained rocks.
EX, Granite.
40
What are the 7 stages of how a sedimentary rock is formed?
1. Particles and dissolved substances are created by weathering.
2. They're transported downhill/downstream by erosion.
3. They're deposited as layers or sediment.
4. They form parallel layers/bedding.
5. Buried sediments are lithified by compaction and cementation.
6. Siliciclastic sediments form (made of rock fragments)
7. Chemical and biological sediments may be precipitated directly from seawater or by organisms.
(As a sediment grows, it'll get buried, and the pressure will increase to push the sediment together, forming a sedimentary rock.)
41
What is uplift?
Bringing rocks up to form mountains.
42
The environment you're in doesn't affect the type of new rock you form. True or false?
False. It dictates the type of new rock that can form.
43
What is magma?
The melted rock below the ground.
44
What is lava?
The melted rock that has reached the surface.
Volcanic rock can bring molten rock to the surface.
45
When does the lava freeze?
At high temperatures; 1,100 to 650 degrees, depending on its composition.
As lava cools, it darkens, which is why basalt is so dark in colour.
Melted rock can cool below or above ground.
46
What are the 2 subsections of extrusive igneous rock?
1. Lava flows (Streams or mounds of cooled melts)
2. Pyroclastic debris (Cooled fragments; materials that blasted out of a volcano.)
47
What is volcanic ash versus volcanic rock?
Volcanic Ash: Fine particles of volcanic glass.
Volcanic Rock: Chunks fragmented by an eruption.
48
Where does partial melting happen?
In the crust and upper mantle. It cannot occur on the surface because the conditions aren't good.
49
What is decompression melting?
A decrease in pressure.
The base of the crust is hot enough to melt the mantle rock, but because of the high pressure, the rocks that would melt are kept solid.
50
Pressure drops when hot rock is carried at shallower depths to a shallower crustal level. Where are 3 places this can happen?
Mantle plumes (Over time, it'll travel upwards and break through the crust to create a hot spot volcano)
Beneath rifts (A continental rift is where the lithosphere is stretched and the crust creates a bumpy dip; a rift)
Under mid-ocean ridges (When the plates are spread apart)
51
What is flux melting/addition of volatiles?
It occurs when volatiles are introduced to the hot mantle. A lithosphere sinks below another lithosphere, bringing the surface material with it, which creates volatiles.
52
What do volatiles do?
They lower the melting temperature of hot rocks.
Common volatiles have H20 and CO2.
They're released from the crust and the asthenosphere melts.
53
What does subduction do?
It carries the water into the mantle and melts the rocks.
A subduction zone is when one lithosphere sinks beneath another.
54
What does rising magma carry with it and what does it do?
It carries the mantle heat with it, which raises the temperature in nearby crustal rock, which then melts.
Magma rises and pulls at the base of the crust.
55
What 3 things is magma made of?
Solid (Solidified mineral crystals are carried in the melt)
Liquid (The melt itself is made of mobile ions)
Gases (Driven off extrusive lava, but it remains in the melt of magma)
56
Rock is made of aggregates of minerals. True or false?
True.
57
What are the 2 main groups of magma?
Dry Magma (Scarce volatiles)
Wet magma (Up to 15% volatiles)
58
What are the 5 common gases associated with magma?
1. Water vapour
2. Carbon dioxide
3. Sulfur dioxide
4. Nitrogen
5. Hydrogen
59
What are the 4 major magma types and what are their silica percentages?
1. Felsic (Feldspar and silica). 66-76% silica
2. Intermediate. 52-66% silica
3. Mafic (Magma that's high in iron and magnesium, but low silica). 45-52%
4. Ultramafic (Highest in iron and magnesium, but low silica). 38-45%
60
What is viscosity?
Resistance of magma to flow.
61
What 4 things cause magmas to chemically vary?
Initial source rock compositions (The most important one)
Partial melting
Assimilation
Magma Mixing
62
How does source rock dictate the initial magma composition?
If you melt the mantle, you'll produce either ultra-mafic or mafic magma.
If you melt the crust, you'll produce either mafic, intermediate, or felsic magma.
63
What minerals melt first/last?
Silica-rich minerals melt first, and Si-poor minerals melt last, so partial melting yields silica-rich magma.
64
What does removing magma from its source create?
Felsic magma or mafic residue.
Felsic minerals melt first.
65
How does the assimilation of magma work?
Magma melts the wall rock that it passes through, and mafic magma rises because it's more dense.
66
What are xenoliths?
Wall rock. Blocks of these fall into magma so that you have 2 magmas; xenolith and the original.
Assimilation alters the magma composition.
67
What 3 things does an igneous rock's cooling rate depend on?
1. Depth (Deeper is hotter). Deep plutons lose heat slowly.
2. Shape. Spherical bodies cool slowly and tabular cools faster.
3. Groundwater. Circulating water removes heat.
68
What is fractional crystallization?
When early crystals settle because of gravity.
Changes the composition.
69
The original melt is mafic, but as they settle out, the remaining magma becomes very felsic. True or false?
True.
70
What is Bowen's Reaction Series? What's a continuous/discontinuous series?
It discovered that minerals solidify in a specific series. Certain minerals will only form at a certain temperature.
A continuous series forms plagioclase minerals, and a discontinuous series is when minerals start and stop forming.
Example: Olivine to pyroxene to biotite.
71
Magma tends to sink downwards. True or false?
False. It tends to rise upward, which transfers mass from deep to shallower parts of the earth.
72
Why is magma a crucial process in the earth's system?
Because it provides the raw materials needed for soil, atmosphere, and ocean.
73
What does lower viscosity do and how is it generated?
It eases movement and is generated by a higher temperature, lower silicate content, and higher volatile content.
74
How can we describe igneous rocks?
By their colour, texture, and composition.
75
What is a crystalline?
Interlocking crystals that fit together like a jigsaw puzzle.
76
What does fragmental rock mean?
It's pieces of pre-existing rocks that're often shattered.
77
What is a crystalline texture?
Interlocking mineral grains from the solidifying melt that reveals the cooling history.
78
What are the 4 types of rocks that form from cooling?
1. Aphanitic/fine-grained rocks (Rapid cooling, so extrusive crystals don't have time to grow).
2. Phaneritic/coarse-grained rocks (Slow cooling, so intrusive crystals have a long time to grow.)
3. Porphyritic textured rocks (A mix of coarse and fine crystals, so there was a 2-stage cooling history).
4. Pegmatitic rocks (Exceptionally coarse-grained)
79
How do glassy textures form?
From the rapid cooling (quenching) of lava.
80
What are the different compositions of igneous rocks?
Felsic, mafic, ultramafic, and intermediate.
81
What are the different textures of igneous rocks?
Fine, coarse, porphyry, and pegmatitic.
82
What does pyroclastic mean?
It's composed of fragments from violent eruptions.
83
What are the 2 major subdivisions of tabular intrusions?
Sill (Injected parallels to rock layering)
Dike (Cuts across rock layering and spreads the rock sideways).
84
What's a batholith?
A massive, discordant body of rock formed by the solidification of magma beneath the earth's surface.
They mark former subdivisions.
85
Where does sedimentary rock form? How can it form?
At or near the earth's surface.
Can form by cementing loose clasts/fragments of pre-existing rock, by cementing loose shells and shell fragments together, by accumulation of organic matter from living organisms, and by precipitation of minerals dissolved in water.
86
What does each layer of a sedimentary rock record?
They each record a history of the environment it was formed in. Layers only occur in the upper part of the crust (Below, there's no sedimentary rock).
87
What are basement rocks? What covers them?
They're made of igneous and metamorphic rock, and sedimentary rocks cover them.
88
What do sedimentary rocks contain?
Coal, petroleum, and natural gas.
89
What are the 4 classes of sedimentary rock?
1. Clastic (Loose rock fragments/clasts that're cemented together)
2. Biochemical (Cemented shells of organisms)
3. Transportation (The dispersal of solid particles and ions)
4. Deposition (Setting out of transporting liquid)
5. Lithification (The final stage; transforming it into a solid rock)
90
What does lithification do? What are its 2 stages?
It transforms loose sediment into solid rock.
1. Compaction (Burial adds pressure to sediment, squeezing out the air and water and compressed sediment grains)
2. Cementation (Minerals grow in pore spaces, often quartz or calcite. They precipitate from groundwater and glue sediments together. They act like glue, forming grains into a solid rock).
91
How are clastic sedimentary rocks classified?
By their clast/grain size, clast composition, angularity and sphericity, sorting, and the characters of the cement (what minerals make up the rock)
92
What is clast composition?
The mineral makeup of sediments.
Clasts can be individual minerals or rock fragments.
93
What is the character of cement?
The minerals that fill sediment pores.
Different clastic sedimentary rocks have different cements.
94
What are the 2 different rock fragments you can have?
1. Breccia (Angular rock fragments)
2. Conglomerate (Rounded rock fragments)
95
What is a microcrystalline?
A crystallized substance of rock that contains small crystals which aren't visible to the naked eye.
96
What is limestone and what are the 3 types? Where does it form?
Sedimentary rocks that're made almost entirely of clacite and aragonite.
1. Fossiliferous limestone (Has visible fossil shells)
2. Micrite (Fine carbonate mud)
3. Chalk (Made of plankton shells)
Biochemical limestone forms in a warm, tropical, shallow, clear, marine water.
97
What is chert?
A rock made of crystalline quartz.
The silica in pore fluids solidifies into a gel, which precipitates as nodules or beds.
Has all the properties of quartz.
98
What are chemical sedimentary rocks? What are the 4 classes?
Comprised of minerals that precipitate from water solution.
1. Evaporites
2. Travertine
3. Dolostone
4. Replacement chert
99
What are evaporites?
Rock formed from evaporated sea or lake water.
100
What is travertine?
Calcium carbonate precipitates from ground water where it reaches the surface. Ex) Thermal hot springs and caves.
101
What is dolostone?
Limestone that's altered by magnesium-rich fluids. Has a sugary texture and often weathers a buff, tan colour.
102
What is replacement chert?
Nonbiogenic and doesn't originate from living organisms.
Cryptocrystalline silica gradually replaces calcite, long after limestone is deposited.
103
What are organic sedimentary rocks?
They're made of organic carbon; the soft tissues of living things.
104
What are the 4 stages of coal formation?
1. Accumulation of plant material
2. Partial decomposition into peat
3. Shallow burial forms lignite
4. Deeper burial forms bituminous coal.
105
What are peat and lignite?
Peat is an accumulation of partially decayed vegetation/organic matter
Lignite is a soft, brown, combustible, sedimentary rock.
106
What are sedimentary structures?
Features on sediments at/near the time of deposition.
Bedding and stratification; surface features on bedding layers.
107
What is lamination?
Arrangement of grains within bedding layers.
108
What is a bedding plane and a strata?
A bedding plane is the boundary between 2 beds
A strata is several beds together.
109
All sedimentary rock must form a bed. True or false?
True.
110
What is conglomerate?
When parts form together to create a whole, but still have distinct parts, like gravel.
111
What can cause bedding forms to change?
Climate, water depth, current velocity, sediment source, and sediment supply.
112
What are ripple marks and dunes?
Ripple marks are cm-scale ridges and troughs. Develop perpendicular to flow.
Dines are the same as ripple marks, but much larger. Form from water or wind. Ranges from 10's of cms to 100's of meters.
113
What are slip faces?
The lee side of a dune where there's a slope.
114
What are cross beds made from?
Ripple and dune migration. The orientation of the cross bed indicated the wind direction at the time of deposition.
115
Where are turbidity currents and graded beds formed?
In deep basins that receive periodic pulses of turbid water. They flow chaotically downslope. As the pulse slows, water loses velocity and the grains settle. Coarsest materials settle first, then medium, then fine materials.
116
What are 3 bed surface markings?
1. Mudcracks (When mud dries, it makes polygonal plates and the edges curl up)
2. Scour Marks (Troughs eroded in soft mud by rapid current flow)
3. Fossils
117
What are depositional environments? Why do the environments vary? What're the 3 environments?
Locations were sediment accumulates.
They vary because they have different chemical, physical, and biological characteristics.
Environments: Terrestrial, coastal, and marine.
118
What are terrestrial environments? What are examples of this environment?
When sediment is deposited above sea level.
EX, glacial environments, mountain stream environments, alluvial fans, sand-dune environments, river environments, lakes, and deltas.
119
What are varves?
Thin stripes of alternating finer and coarser sediment reflect the seasonal changes in sedimentation.
120
What are marine environments? What are examples of this environment?
When sediment is deposited at/below sea level.
Ex, delta, coastal beach sands, shallow-marine, clastic deposits, shallow water carbonate environments, and deep marine deposits.
121
What are carbonates?
Shells of organisms.
122
What are basins?
Special planes where sediment accumulates.
123
Where do sedimentary basins form?
Where tectonic activity creates space. It creates spaces for the sediment to settle in.
124
What are rift basins?
Divergent (pull-apart) plate boundaries. The crust things by stretching and rotational normal faulting. The space between rifs.
125
What are passive margin basins?
The continental edge that's far from a plate boundary.
126
What are foreland basins?
The craton side of a collisional mountain belt. Fills with debris eroded off of mountains.
127
What is transgression?
Flooding due to sea levels rising. Sediment belts shift landward, and strata 'deepens' upward.
128
What is regression?
Exposure due to the sea level falling. Depositional belts shift seaward and strata 'shallows' upward. Sediments are mostly eroded.
129
What is diagenesis?
Physical, chemical, and biological changes to sediment.
An important term in sedimentary rock. As sediments are buried, the pressure and temperature rise.
130
What is the temperature between burial and metamorphism?
Around 300 degrees
131
When the rock changes, it's no longer burial, but metamorphism. True or false?
True.
132
What are metamorphic rocks?
Rocks that have undergone solid-state alternation of a protolith.
The metamorphic changes occur slowly in the solid-state.
Solid-state: When a rock doesn't form from solidification or freezing of a melt.
133
What are metamorphic changes due to?
Changes in pressure, temperature, tectonic stresses, and the amount of reactive water.
134
What's a foliation plane? What is foliation?
Layering in the metamorphic rock; a change in texture.
Foliation is a planar fabric that cuts through the rock.
135
What 5 processes can happen during metamorphism?
1. Recrystallization (Mineral changes in size and shape, but the mineral identity/composition doesn't change)
2. Phase change (New minerals form with the same chemical formula, but have a different crystal structure.)
3. Neocrystallization (New crystals emerge from the old)
4. Pressure solution (Mineral grains partially dissolve where their surfaces press together.
5. Plastic deformation (Mineral grains soften and deform, and the mineral changes shape without breaking)
136
What is metamorphism due to heat? What are the 3 sources of heat?
Most metamorphism occurs between 250 and 850 degrees, and the depth can vary with tectonic setting.
3 sources of heat: Geothermal gradient (T increases as you go deeper), Magmatic Intrusions (Heat from the intrusive rock breaks the wall rock), and Tectonic Compression (Friction of mountains and continents colliding creates heat)
137
What is solid-state diffusion?
Migration of atoms between grains.
138
What is metamorphism due to pressure?
Pressure increases with depth in the crust at a rate of 270-300 bars/km. Metamorphism occurs mostly in the 2-12 kbar range.
139
What is the stability of a mineral referring to?
The ability of a mineral to form and survive.
140
What is metamorphism due to compression?
Compression is stress that's greater in one direction. It's a common result of tectonic forces.
141
What is metamorphism due to shear?
Shear is stress that moves a material sideways, smearing it out.
142
What is metamorphism due to compression AND shear?
When applied together, it causes mineral grains to change shape.
143
What do equant and inequant mean? What are the 2 types of inequant shapes?
Equant means it's roughly equal in all dimensions.
Inequant means the dimensions aren't the same.
The 2 types are platy (pancake-like) and elongate (like a cigar; one dimension is larger)
144
What is the development of preferred orientation?
It causes rocks to change shape without breaking. When minerals grow in a preferred orientation, it means they're aligning parallel to each other and perpendicular to the compression.
145
What is hydrothermal fluid metamorphism?
Hot water dissolves ions and volatiles, and these fluids facilitate metamorphism by speeding up chemical reactions and altering the rock.
146
What is metasomatism?
Hydrothermal alteration.
147
What are the 2 major subdivisions of metamorphic rocks?
1. Foliated, giving the rock a streaked/striped appearance and sometimes provides weakness where a rock can break. An alignment of inequant grains/compositional banding.
2. Non-foliated, where no planar fabric is evident.
148
What is metaconglomerate?
Metamorphosed conglomerate. Pebbles and cobbles are flattened by pressure solution and plastic deformation.
149
What is metamorphic differentiation?
When minerals segregate into layers.
150
What is compositional banding?
When chemical reactions segregate the light and dark layers.
