RVCC GCH GEOL157 Introduction to Geology Laboratory Manual GCH GEOL157...Title Microsoft PowerPoint...

RVCC GEOL 157 Introduction to GeologyProfessor Gregory C. Herman [email protected] Manual

GCH 2018-01

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Sources noted within

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RVCC GEOL 157 Introduction to Geology Lab Manual GCH 2018-01


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• LAB ROOM SC-219 is set up with five (5) student tables with four seat each.

•One Fischer-Scientific stereo microscope will be furnished per table during mineral and rock labs.

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PROJECTOR

LECTURN

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LAB ROOM SC-219 is set up with five tables, four seats per table.

• Laptop PCs are available to students if they do not have one or cannot use their own. Use of one’s own lap top is encouraged, as is the use of a optical mouse with a wheel (USB or Bluetooth) for Google Earth labs.

Paired wide-field eyepieces

Adjustable magnification

by rotating the

adjustable turret

Adjustable left eyepiece for focus

Adjustable knob used

to lower and raise the

microscope head

stage

Fischer-Scientific T1A STEREO MICROSCOPE


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Can transmit plain white light from above or

below the object placed

on stage (light switches

not shown)

• This lab is an introduction to minerals and spectroscopy, the latter being the scientific study of how light interacts with solid matter.

Minerals comprise Earth materials and are formed by :

1) the cooling of melted Earth material (molten magma) in Earth’s crust (solid) and

2) the precipitation of minerals from eithera) saturated, briny fluids (including microcrystalline forms of quartz and calcite) orb) biological accretion (seashells)

By the end of this lab you should have a working familiarity with the most-common rock forming minerals, including the 5 most abundant silicate rock-forming minerals (quartz, feldspar, mica, amphibole, and pyroxene) that comprise Earth’s crust. We will identify them separately from other common minerals that appear similar but are usually softer and formed from precipitation .

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Laboratory 2. Minerals and Spectroscopy

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Laboratory 2. Minerals

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Exercise 1. Handle and identify the 10 most common rock-forming minerals


• Carbonates (CO3)-2

•Sulfates (SO4)-2

•Phosphates (PO4)-3

Calcite (CaCO3) is the main constituent in the

sedimentary rock limestone

Gypsum (CaSO4 . H4O) is a main constituent in drywall

Turquoise CuAl6(PO4)4(OH)8·5H2O

derived from the shells and hard parts of marine organisms or are precipitated as seawater evaporates

derived from hydrothermal activity or are precipitated as saline-water

evaporates

derived from hydrothermal activity and igneous processes

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Laboratory 2. Mineral Cleavage

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http://slideplayer.com/slide/8711262/26/images/9/Types+of+Cleavage.jpg

Laboratory 2. Mineral Cleavage Types

Mohs Hardness Scale

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Adapted from Cronin, V. S., and Tasa, D., 11th Laboratory Manual in Physical Geology: Pearson, New York, NY, 426 p.


Silicate Minerals

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Quartz – No. 2 of the 5 most common rock-forming (silicate) minerals

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• Identify quartz, calcite, and gypsum by checking the type of habit, cleavage, and visual aspects that you observe

Quartz (silica SiO4)Calcite (carbonate CaCO3) Gypsum (sulfate SiO4)

NOTES:

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• Group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust. •Two cleavage directions at 900. •Hardness of 6 – 6.5.•Will not scratch glass or quartz.

•Microcline and orthoclase•Not usually clear. •Often salmon pink or white and milky. •Can also be aqua blue. •Can have wavy stripes of similar color that go through the mineral.

Alkali feldspars (K,Na)AlSi3O8

Plagioclase feldspars (Na,Ca)AlSi3O8•Albite to Anorthite solid-solution series•Individual crystals a range of colors between white and dark gray. •Exhibits striations•Can have wavy stripes of similar color that go through the mineral.

www.earthguide.ucsd.edu/mystery_detectives/media/flash/minerals_igneous/minerals_igneous.swf

FELDSPAR – No. 1 of the 5 most common rock-forming (silicate) minerals

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• Identify plagioclase and alkali feldspar by color, microscopic twinning, and mineral habit, hardness with respect to quartz and metal. Note any visual and physical aspects that you observe.

Plagioclase feldspar (silicate (Na,Ca)AlSi3O8)

Twinning seen on face of large plagioclase sample

Alkali feldspar (K,Na)AlSi3O8)

NOTES:

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Cleavage habitLaboratory 2. Minerals

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Cleavage habitLaboratory 2. Minerals

• Identify the following minerals by color, and mineral habit, hardness with respect to quartz and metal and one another. Note any distinctive visual and physical aspects that you observe.

Mica (biotite and muscovite)

Pyroxene

Amphibole

Olivine/peridotite

NOTES:

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Laboratory 2 – Part B Spectroscopywww.impacttectonics.org/Gcherman/downloads/PHY120C/

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For this exercise, pick 3 minerals out of the box and use your manual and the Internet to make your best guess as to what it is. Write the name and a chemical formulae down.

Color

Habit

Cleavage

Hardness

Weight

Streak

Magnetic

Notes:

NameChemicalFormuale

Sample 1 Sample 2 Sample 3

Laboratory 2. Minerals Pick 3 Exercise

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Exercise 1. Identify the 10 most common rock-forming minerals

Gypsum (Alabaster) Muscovite

(mica)Gypsum

(crystalline)

Calcite (spar) Halite

Plagioclase feldspar

Milky quartz

Quartz crystals

Alkalifeldspar

(Orthoclase)

Pyroxene(Augite)

Amphibole (Hornblende)


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1) Igneous are derived from the hardening of molten magma (intrusive or volcanic, with felsic, intermediate, and mafic varieties)

2) Sedimentary are derived from detrital or chemical sediment, the products of mechanical and chemical weathering and chemical precipitation.

3) Metamorphic are the result of burial, increasing temperature and pressure, and fluid transfer processes during recrystallization (low, medium, and high grade)


• Igneous rock forms when hot magma cools and solidifies. Sedimentary rocks form when sediment is compacted and cemented together (lithified), or when minerals precipitate from solutions. Mechanical weathering and physical breakdown of a parent material (usually rock) produces clastic or detrital sediment, whereas chemical sediment is accreted through biological processes or precipitates directly from hydrothermal or briny waters. Metamorphic rocks are compacted, heated, pressurized, and altered from burial, thermal contact, and fluid transfer during recrystallization and alteration.

Laboratory 3. Igneous Rocks • Rocks are identified by their colors, textures, and other physical properties like

hardness, weight (density or specific gravity), magnetism (magnetite), and reactivity with acids (limestone and marble).

• The first exercise for this lab is to study and become familiar with 12 igneous rock specimens included in a Ward’s scientific rock kit, differentiating between those of plutonic (intrusive) and volcanic (extrusive) origin.

• A secondary exercise will be to examine the loose sample of igneous rocks held by RVCC, discuss them among your peers and professor, and categorize them.

• A third exercise will be to complete a puzzle depicting an ordered sequence of igneous rocks exposed in a mountainside using knowledge about the geological progression of igneous intrusions.

• By the end of this lab you should have a working familiarity with the principal types of igneous rocks, have identified the most common rock-forming minerals in the specimens, and seen the textures commonly found in the mafic, intermediate, and felsic rocks.

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PLUTONIC(intrusive varieties)

Laboratory 3. Igneous Rocks

+1 os

+2 os

os – oxidation state

An element having a +2 os (or charge) has

a higher electron affinity because it has twice the charge than

one with a +1 os.

• Calcium and magnesium (+2) are proportionately more abundant in mafic rocks that crystallize form magma first with slow cooling and crystal growth.

•Parent magma composition largely determines the composition of igneous rocks but a single magma can, however, yield different rock types.

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Texture in igneous rocks is related to cooling history; the slower the magma cools, the more coarse-grained the rock becomes.

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•Typically, the coarsest-grained rocks formed in deep crustal chambers after rising out of the mantle where it can accumulate and pond at the base of the crust or in the crust, or deep in the roots of crustal mountain where rocks begin to melt from burial and heat. They become exposed at the surface Eons after formation from crustal tectonics.

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Exercise 1. An Igneous Rock Collection by Ward’s Scientific

Basalt

Diorite

Gabbro

Granite

Obsidian

Pegmatite

Peridotite

Pumice

Rhyolite (2)

Scoria

Syenite

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NOTES: NOTES:


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NOTES:


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Granite (Felsic)

Diorite (Intermediate)

Gabbro-Basic

RVCC loose plutonic material



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Rhyolite (Felsic)

Basalt-basic

Scoria

RVCC loose volcanic material

obsidian

Andesite (Intermediate)

Volcanic

bomb

Tuff



_____ SS - red sandstone _______ B - basalt dike leading to basalt flow ______ D - diorite stock and sills ______Gr – granite ________ Pg – pegmatite ______ Gb – Gabbro

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Exercise 1. An Igneous Rock Collection by Ward’s Scientific

1.Obsidian

2. Pumice

3. Scoria

4.Basalt

5. Rhyolite

6. Rhyolite

7. Granite

8. pegmatite

9. Andesite

10. Diorite

11. Gabbro

12. Peridotite

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Laboratory 5a. Sedimentary Rocks•The two primary types of sediment are chemical and detrital.

•Sediment becomes lithified into sedimentary rocks by cementation and compaction.

•Chemical sediment consists of minerals precipitated from solution by inorganic processes and from accretion by biological organisms.

•Chemical sedimentary rocks (limestone, coal, microcrystalline quartz) are formed from chemical sediment.

•Detrital sediment consists of solid particles, products of mechanical weathering.

•Detrital sedimentary rocks are formed from detrital sediment

•Both chemical and detrital sediment and sedimentary rock can contain fossils, some being macroscopic (visible to the naked eye) and microscopic (viewable to humans only through magnification).


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• The primary exercise for this lab is to study and become familiar with 12 sedimentary rock types included in a Ward’s scientific rock kit including those of detrital and chemical origin.

• A secondary exercise will be to examine the loose samples of detrital and chemical sediment and rocks held by RVCC, discuss them among your peers and professor, and categorize them.

• A third exercise will quiz you as to some common and primary sedimentary features seen in sedimentary rocks

• By the end of this lab you should have an introductory familiarity with the principal types of sedimentary rocks, including the terminology and methods of discriminating between clastic (detrital) and chemical varieties, including microcrystalline forms of quartz and calcium carbonate.

Laboratory 5a. Sedimentary Rocks

Chemical sedimentary rocks are:

a) Precipitated directly from fresh

or sea water by biological

accretion,

b) Precipitated directly from

chemically saturated water in

fresh, marine, and hydrothermal

environments, or

c) Formed in bogs or swamps from

the accumulation of dead organic

matter (animal and vegetation)

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Laboratory 5a. Chemical Sedimentary Rocks

Checklist:

Limestone (CaCO3 in it’s pure form) is generally soft, gray to cream colored, will react with HCL, and is softer than metal, and can contains marine fossils (coquinas, sea shells, coral, etc.).Dolomite is similar to limestone but is commonly has some Mg+2 replacing Ca+2, can have an orange tint from also having some Fe+2, is slightly harder than limestone, is less reactive to HCL

For coal, recognize the peat lignite coal transition and the bituminous versus anthracite types. Bituminous is lower grade, has more sulfur (yellow mineral) and is not as shiny. Anthracite of higher ‘grade’ as it burns cleaner and gives off more energy.

Differentiate among cryptocrystalline quartz and limestone that are precipitated out of hydrothermal solutions or saturated waters.

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Laboratory 5a. Chemical Sedimentary Rocks

a) Detrital sedimentary rocks are transported and deposited by running water, wind, or glacial ice.

b) Most are composed of silica grains and/or mineral and rock fragments, and are therefore differentiated using grain size.

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Common cementing agents are silica and calcium carbonate.

Mudcracked siltstone

Laboratory 5a. Detrital Sedimentary Rocks

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Laboratory 5a. Detrital Sedimentary Rocks

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Exercise 1. A Sedimentary Rock Collection by Ward’s Scientific

13 White chert

14 Siltstone

15 Coquina

16 Qtz conglomerate

17 Red sandstone

18 Very-fine gray

sandstone

19 Gray limestone

20 Black shale

21 Shell limestone

22 Dolomite

23 Travertine

(dripstone)

24 Gypsum

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Checklist:

Recognize increasing grain size of mudstone siltstone sandstone conglomerate.

Conglomerate contains rounded grains whereas breccia contains angular grains

The degree of rounding and sorting of grains in the various samples and discuss the significance with respect to transport distance.

Those cemented with calcium carbonate are commonly more friable and can react with dilute HCL whereas silica-cemented ones are harder and nonreactive to HCL.

Mudstone and shale differ because the latter has initial layering, or fissility, by the preferred alignment of play minerals during early phases of burial and compaction.

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Laboratory 5. Detrital Sedimentary Rocks

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Laboratory 5b. Metamorphic Rocks• Metamorphism is the change of minerals or geologic texture (distinct arrangement of minerals)

in pre-existing rocks (protoliths), without the protolith melting into liquid magma (a solid-state change). The change occurs primarily due to heat (Temperature), pressure (P), and the introduction of chemically active fluids (F).

• New mineral growth results from changing geological conditions (F-T-P) accompanying burial, tectonism, and plutonic igneous activity.

• Three categories of metamorphic rocks are identified by their minerals, fabrics, textures, weight, and color.

• Low-grade metamorphic rocks like quartzite, slate, and low-grade marble may or may not be foliated are more dense, hard, and mineralized than sedimentary protoliths. Low-grade metamorphic rocks can have remnant primary, sedimentary structures and grains still visible.

• The preservation of primary sedimentary structures (like bedding, ripple marks, and mud cracks) decreases with metamorphic grade because the degree of recrystallization increases from medium-grade schist, through high-grade gneiss into partially melted migmatite, the latter resembling igneous plutonic rocks, and containing many of the same mineral assemblages. Gneisses more than schists have distinct mineral banding between iron-rich (dark) and silica-rich (light) mineral layers.


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Laboratory 5b. Metamorphic and Crustal Rocks

• The first exercise for this lab is to study and become familiar with 12 metamorphic rock types included in a Ward’s scientific rock kit including those of low-, medium-, and high-grade varieties.

• A second exercise is to examine the loose samples of metamorphic rocks held by RVCC, discuss them among your peers and professor, and categorize them.

• A third exercise is to examine the various loose collections of crustal rocks as a review before the exam.

• By the end of this lab you should have a working familiarity with the principal types of crustal rocks, including the names of the principle sediment and rock types.


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Exercise 1. A Metamorphic Rock Collection by Ward’s Scientific

25. Gneiss

26. Pink gneiss

27. Schist

28. Garnet schist

29. Hornblende gneiss

30. Red quartzite

31. Red slate

32. Gray slate

33. White marble

34. Pink marble

35. Serpentinite

36. Soapstone

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Laboratory 5b. Low-Grade Metamorphic Rocks

Checklist:

The transition of lime rocks to different types of marble (foliated and non-foliated)

Hornfels are sedimentary rocks that have been altered and mineralized by hydrothermal solutions percolating through them.

The transition from sandstone to quartzite (foliated and non-foliated).

The transition of mudrocks from mudstone argillite phyllite

Those cemented with calcium carbonate are commonly more friable, are softer than steel, and react with weak acid, whereas silica-cemented ones are harder than metal and don’t react with acid.

Quartzite and marble can look very similar, but metal scratches marble but not quartzite.

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Laboratory 5b. Low-Grade Metamorphic Rocks

Schist is a medium-grade metamorphic rock with medium to large, flat, sheet-like grains in a preferred orientation (nearby grains are roughly parallel). It is defined by having more than 50% platy and elongated minerals, often finely interleaved with quartz and feldspar.

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Laboratory 5b. Medium-Grade Metamorphic Rocks

Gneiss is a high grade metamorphic rock, meaning that it has been subjected to higher temperatures and pressures than schist. It is formed by the metamorphosis of granite, or sedimentary rock. Gneiss displays distinct foliation, representing alternating layers composed of different minerals.

Migmatite is a rock that is a mixture of metamorphic rock and igneous rock. It is created when a metamorphic rock such as gneiss partially melts, and then that melt recrystallizes into an igneous rock, creating a mixture of the unmelted metamorphic part with the recrystallized igneous part.

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Laboratory 5b. High-Grade Metamorphic Rocks


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Laboratory 5b. Medium to High-Grade Metamorphic Rocks

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Note:

Metamorphic rocks form when minerals in a sedimentary or igneous rocks rock begin to recrystallize into new mineral forms when it is subjected to changes (usually increases) in temperature and pressure from burial or through interaction with groundwater.

The transition from sedimentary rocks into low-grade metamorphic rocks is gradual as rocks become more deeply buried and heated through time, therefore it is sometimes difficult to tell if a mudrock is sedimentary or low-grade metamorphic without microscopy. Similarly the transition from limestone into a marble sometimes requires microscopic work.

Generally speaking, metamorphic rocks are more compact and dense than their sedimentary precursor rocks, have foliation caused by mineral banding or layering that can be seen with the naked eye. But this isn’t the case for pure quartz or limestone rocks that can be mono-minerallic and therefore locally lack visible foliation.

Laboratory 5b. High-Grade Metamorphic RocksRVCC GEOL 157 Introduction to Geology Lab Manual GCH 2018-01

garnet

A.

B.

C.

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Laboratory 5b. Crustal Rocks

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Laboratory 8. Geological Primary and Secondary Structures

• The first exercise for this lab is to study and become familiar with different sets of secondary structures that I supply from my personal rock collection.

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PROJECTOR

LECTURN

Faults• Different rocks

containing examples of rock fractures, cleavage, folds, and faults will be placed on lab tables to study and discuss.

• After an introductory lecture about the different classes of structures, groups of four or five students will rotate to each table in about 10-minute intervals to inspect each set of rocks.

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Laboratory 8. Cleavage Strains

A) A slab of rock with height (H) and length (L) Sedimentary beds in profile (side view)

B) A cleaved slab of rock with shortening of ~ 10% from pressure solution and/or recrystallization and no simple shear.

C) A cleaved slab of rock with cleaved lithons rotated 30o

from simple shear resulting in lengthening (~ 10%) and flattening (~2%).

lithon

Cleavage selvage plane L

H

L1

DL

L2

Rocks become strained from applied stresses of tectonic movements or sedimentary loading. Cleavage is one type of strain mechanism. The loss of rock material from cleavage development can produce bulk changes in the shape of a rock slab, depending upon whether there is shear involved or just simple shortening.

H1= H2

H3 < H2

Shortening only

Shortening, shearing, and flattening

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Axial-planar, spaced cleavage

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Laboratory 8. Fault Strains and Fabrics

• A cleaved slab of rock with lithons rotated 30o from simple shear resulting in lengthening(~10%) and flattening (~2%).

Rocks can become faulted with planar discontinuities that separate individual lithons, or fault slices that nestle among themselves with 3D geometries resembling slip cleavage. The transition from slip cleavage to faulting is a matter of scale and definition.


L2

H3 < H2

• Progressive strains from shearing, rotation, flattening, and imbrication of lithons occur in fault zones or shear zones.

• In 3D, faulted lithons become nestled together like bunches of aligned watermelon seeds slipping past each other.

Shortening, shearing, and flattening

Lithons become progressively smaller

with higher strains

Larger faults

Apparent normal slip (flattening and lengthening)

Apparent reverse slip (thickening and shortening)

OR lithon

Fault planes appear as tip lines in profile

• Cleaved and faulted Lithons are elliptical in profile and terminate in 3D at tip lines.

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