Metamorphic - Geomorphology student copy PDF

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Geomorphology student copy...

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Metamorphic Rocks Lab Read Ch. 7 of your lab book (pgs. 185-196). Please do not Google your answers. Utilizing your lab book will be of benefit because your answers are more likely to be correct. This lab is to be answered in YOUR OWN WORDS. You will be asked to open the Metamorphic Lab Pictures ppt (this is different than the Metamorphic Rocks Intro ppt) to complete parts of this lab. Part I: Minerals and Textures Sample 1: Granite vs. Gneiss What type of rock is granite (bold or highlight your answer)? Metamorphic

Sedimentary

Igneous

What are some common felsic minerals in Granite (review pg. 130, Figure 5.16 (pg. 135)? -Quartz, Potassium feldspar, muscovite A. Compare Granite with Gneiss. How are these samples similar? How are they different? Be specific. -Gneiss Is the metamorphic version of granite and also the movement and texture are different. But they are similar as they are made up of feldspar

B. What is the texture of the Gneiss? How does that texture develop (pg. 193)? -The texture is phaneritic and the texture develops from differential stress and gneissic banding

Minerals in Metamorphic Rocks A. List 2 common rock forming minerals found in Metamorphic Rocks (pg. 190 – review Igneous Rocks Lab). Calcite and Quartz B. What are 4 common metamorphic minerals that are considered index minerals that help define metamorphic zones (pg. 190)? -kyanite, garnet, staurolite, sillimanite C. See slide 3 of the Metamorphic Rocks Lab ppt. Which 2 minerals from the picture interest you? Write down the mineral name below and research something interesting or a use for the mineral. a. Mineral 1: -Garnet. Garnet dates back to the Egyptians. b. Mineral 2: Serpentine. Serpentine aids in meditation and spiritual exploration

D. Look at Figure 7.10 (pg. 193). This figure shows you the progressive metamorphic grade of a clay-rich protolith (shale). What does the presence of the mineral in spot #1 indicate about the GRADE of a metamorphic rock. Bold or highlight your answer. Low

Intermediate

High

Part II: Using observation of rock textures to determine the “grade” of metamorphism (pgs. 191-193 and Metamorphic Rocks Lab Pictures PPT). The most common sediments for your sample rocks are fine grained sedimentary rocks (shales, siltstones, wackes). When these sedimentary rocks are metamorphosed at convergent margins they make a “grade” or series of metamorphic rocks. They all contain MICAS as their principal mineral +/- some quartz and iron oxides. You are given a set of unknown rocks labelled Sample 2-5. Using their sample numbers, place the rocks in the sequence of increasing metamorphic grade. As heat and pressure increase:

Shale → _______3_______ → ______4________→ ______2________ → _______5_______ → Melt

A. What is a protolith? The original rock that undergoes metamorphism.

B. What observation(s) did you use to place your samples in order of increasing grade? (Ex. Texture, composition, foliation, etc.) To look at the highest grade we looked at luster. Four had more foliation which meant it had higher stress which meant it has a higher grade. 5 and 2 were shiny as well, which gave them a higher grade. C. Describe what happens to the mineral size and orientation as you progress from LOW to HIGH grade metamorphism? The grains are bigger if the grade is higher. You can see the texture and such for the orientation when it goes high to low

D. Figure 7.3 (Slide 9) shows regional metamorphism pressure and temperature gradients with various metamorphic rocks. Look at the typical geothermal gradient line (dotted green line) and provide estimate depths and temperatures for the following rocks in the table: Metamorphic Rock

Depth (Km)

Temp (Co)

Type Slate 5 200 Phyllite 10 300 Schist 15 450 Gneiss 20 600 E. Explain what happened to make the grain size (in your samples/chart) change and the micas to become parallel or subparallel. (pg. 193) - The temperature and pressure increased for grain size F. Relating back to plate tectonics; what type of plate boundary might this (sequence of metamorphic rocks) occur? A convergent plate boundary would occur. Part III: Lab activity of practicing identification: Using the link http://www.profharwood.x10host.com/GEOL101/Labs/Metamorf/index.htm Select a sample to identify by clicking on the numbers 1-8 An image of the sample will appear; identify the Texture, Foliation, Composition, Parent Rock and Rock Type by clicking on the options given in the ‘Metamorphic Rock Identification Chart’. It really helps to have read your lab book and completed the first part of the lab before starting this section. Then click on ‘Grade identification’ to see if your identification was correct. If you miss anything, go back and have it fixed. You can also do acid and hardness test. Complete the table below for all the eight samples. Sample #1 has been done for you. Metamorphic identification chart Sample #

Texture

Foliation

Composition

Parent rock

Rock name

1

Foliated

Gneissic banding

Feldspar, mica, quartz

schist

Gneiss

2

Foliated

Schistose

Mica, quartz

slate

schist

3

calcite

limestone

marble

4

NonFoliated Foliated

slaty

mica

mudstone

slate

5

Foliated

schistose

Mica, quartz

Slate

Schist

6

NonFoliated

Quartz, mica, chlorite

sandstone

quartzite

7

Foliated

carbon

mudstone

Phyllite

8

NonFoliated

carbon

Bituminous coal

Anthracite

Phyletic...