metamorphic rock lab_____ metamorphic rock samples with identifying numbers/letters (one set per...

© 2018 Pearson Education, Inc.

METAMORPHIC ROCK LAB

• INTEGRATED SCIENE

• LAB 07

• Dr. Gregg Wilkerson and Larry Drennen


LABORATORY SEVENMetamorphic Rocks, Processes, and ResourcesActivities 7.1, 7.4

BIG IDEAS: Metamorphic rock has changed to a new and different form while in the solid state––without melting. Metamorphic change occurs because of increased heat, pressure, differential stress, or hot

water. The mineralogy and texture of a metamorphic rock can be used to interpret its geologic history. This

provides us with a glimpse of structural and tectonic events in the past, and helps us understand current

processes occurring beyond our direct observation below Earth’s surface. If the rock has undergone less

intense metamorphism, we can often infer what the rock was like before metamorphism. Metamorphic

rocks are widely used in the arts and construction industries and are sources of industrial minerals and

energy.

THINK ABOUT IT (Key Questions):• What do metamorphic rocks look like? How can they be classified into groups? (Activity 7.1)

• What are the characteristics of metamorphic rocks, and how are they formed? (Activity 7.2)

• How are rock composition and texture used to classify, name, and interpret metamorphic rocks?

(Activities 7.3 & 7.4)

• What can metamorphic rocks tell us about Earth’s history and the environments in which the rocks

formed? (Activity 7.5)


LABORATORY SEVENMetamorphic Rocks, Processes, and ResourcesActivities 7.1, 7.4

ACTIVITY 7.1: Metamorphic Rock Inquiry

No instructor-supplied materials are needed for this activity.

ACTIVITY 7.4: Hand Sample Analysis, Classification, and Origin

_____ metamorphic rock samples with identifying numbers/letters (one set per group of students)

_____ mineral analysis tools: pocket knife or steel masonry nails, wire nails, glass plates, streak plates, copper pipe or tubing, small magnets (one set per group of students)

_____ dropper bottle of dilute hydrochloric acid (1–3% HCl). If there is a sink in the room, it might be best to restrict the HCl testing to the sink where specimens can be washed and dried after being tested with acid.

INSTRUCTOR NOTES

Foliation. Metamorphic foliation develops as grains grow or plastically deform at high temperature in a differential stress field. New minerals grow at

equilibrium

with all of the relevant environmental variables (pressure, temperature, fluids, chemical/mineral composition, and so on). High-T crystal plasticity and

mineral phase equilibria are beyond this course level, so it takes thought and careful planning to provide students with useful concepts of foliation development that do not involve misconceptions.

Platy minerals (chlorite, micas) grow with their flat faces perpendicular to the greatest compressive stress. The flattening of a ball or cube of Silly

PuttyTM on a tabletop perpendicular to the force of gravity shows how a solid can slowly adjust its shape to a differential stress. This physical model

provides an analogy to the natural process of growing or plastically deforming mineral grains so that faces with a greater surface area are perpendicular to the greatest compressive stress; however, a putty is not a crystalline solid.

Other minerals adjust their size and shape to minimize the internal strain energy stored in their crystal lattices and grain boundaries. Higher flow

stresses result in smaller grain sizes due to dynamic recrystallization. The equant shape of soap bubbles is analogous to the least-energy shape for grain boundaries.

Foliation can also occur in ductile shear zones. The result is a rock called a mylonite, which forms because of localized shear deformation.

Be careful not to present physical models or suggest thought experiments that provide a misleading picture of how metamorphic foliation develops. It can be difficult to reverse a misconception after it takes hold in a novice geoscience student.

© 2018 Pearson Education, Inc.7-4© McGraw-Hill Education.

Metamorphic RocksMetamorphism = Change

Changes in mineral composition and/or texture that can occur in any solid rock

• Changes due to increasing temperature and/or pressure and/or the presence of fluids.

• Temperatures high enough to promote chemical reactions but not high enough to cause melting

• Similar temperatures found deep in crust or near magma chambers

© 2018 Pearson Education, Inc



7.1A 1. This rock has alternating layers of dark minerals and light minerals. The layers seem somewhat irregular.

2.This rock is a fine-grained material that has been folded without breaking the layers.

3. This rock is composed of white calcite mineral grains that are about equal in size.

4. This is a layered rock with a shiny surface that might be due to tiny grains of muscovite, and some much larger garnets.

5. This is a very fine-grained rock that has been folded on a small scale so it looks wrinkled. It is probably layered, and its shiny surface might be due to grains of muscovite along the layers.

6. This layered rock seems to have abundant coarse muscovite grains. The layers seem irregular rather than flat.

7.1B Reflect & Discuss Answers will vary widely. The most obvious groups are probably “layered” and “not layered.”



7.1A1. This rock has alternating layers of dark minerals and light minerals. The layers seem somewhat irregular.



2.This rock is a fine-grained material that has been folded without breaking the layers.



3. This rock is composed of white calcite mineral grains that are about equal in size



4. This is a layered rock with a shiny surface that might be due to tiny grains of muscovite, and some much larger garnets.



5. This is a very fine-grained rock that has been folded on a small scale so it looks wrinkled. It is probably layered, and its shiny surface might be due to grains of muscovite along the layers.



6. This layered rock seems to have abundant coarse muscovite grains. The layers seem irregular

rather than flat.




7.1B Reflect & Discuss Answers will vary widely. The most obvious groups are probably “layered” and “not layered.”


Metamorphic Rocks, Processes, and ResourcesActivity 7.4



Marble

X

LimestoneCalcite

Anthracite Coal

X

Bituminous Coal

Coal

Schist Shale

XMica, Quartz,

Feldspar

Slate ShaleClayLayeredX

Gneiss

X

GraniteMica, Quartz, Feldspar



Meta -Conglomerate

Phyllite

Conglomerate

Various – Clastic sedimentary rock

X

X

Mica Slate


Alternative Sample Set


2

3

4

5

Anthracite Coal

Schist

Slate

Gneiss

X

X

Shale

Shale

Granite

Bituminous Coal

X

XMica, Quartz,

Feldspar

Mica, Quartz, Feldspar

Coal

Clay


Layered

1

Quartzite

X

SandstoneQuartz sand


6


Marble

X

LimestoneCalcite


Metamorphic Rocks, Processes, and ResourcesExamples

metamorphic rock lab_____ metamorphic rock samples with identifying numbers/letters (one set per...

Documents