geol lab Metamorphic Rocks

Description

This week we will finish up our studies with the Rock Kit as we review Metamorphic Rocks (Rocks #38-48 in your Rock Kit).

These rocks give us a constant reminder that our planet earth is applying heat and pressure to all of the existing rocks and changing their appearance. Likewise, God is constantly wanting to change us in the image of His son Jesus Christ. Unlike rocks, God allows us to choose His way.

Laboratory # 7 (Lab Manual)

“Metamorphic Rocks”

Objectives:

A. Be able to describe and interpret textural and compositional features of metamorphic rocks.

B. Be able to determine the names, parent rocks, and uses of common metamorphic rocks, based on their textures and mineralogical compositions.

C. Infer regional geologic history and the relationship of metamorphic facies to plate tectonics using index minerals, pressure-temperature diagrams, and geologic maps.

• There are several different pictures of metamorphic rocks on your lab manual chapter. You will w ant to study these closely as they will help you in identifying your metamorphic rock samples.

Part 1: Activity 7.1 (Parts A and B)

Part 2: Rock Identification (Activity 7.4):

The PowerPoint file for the Lab does a good job of walking you through the identification of metamorphic rocks. You will be developing an Excel Chart and identifying your metamorphic rocks in your rock and mineral kit. Please make sure when you list your specimen number on your Excel Chart that you list them in numerical order using the same numbers that are attached to the specimen.

Determine if the rock is foliated or nonfoliated, Step 1.

• If foliated, determine the degree or type of foliation: slaty, phyllitic
• (pronounced phi lit ic), schistose (be very careful with this pronunciation), or gneissic (nice ic). You will identify the type of foliation by writing the type under the foliated area under the “texture” column for each specimen.
• Once you know the type of foliation, you know the rock name for foliated rocks.

If the rock is nonfoliated, you must identify the main mineral. We are looking at basically the same minerals that we did with sedimentary rocks and the same diagnostic properties still work. You may want to go back to Laboratory 3 to review the minerals.

• If quartz, the rock name is quartzite.
• If calcite or dolomite, the rock name is marble.
• If talc, the rock name is soapstone.
• If coal, the rock name is anthracite coal.
• If hornblende and plagioclase, the rock name is amphibolite.
• If serpentine (a source of jade), the rock name is serpentinite.
• If mineral is uncertain and the rock is dark, the rock name is hornfels.

To determine the parent rock, you may use the Step 3 In addition to the parent rock listed for the foliated rocks, you can use the following:

• Parent of Gneiss = schist
• Parent of Schist = phyllite
• Parent of Phyllite = slate
• Parent of Slate = shale

In this way, you can see the progression of degree of metamorphism. Slightly metamorphosed shale becomes slate. Add a little more pressure, heat, and time, and the slate becomes phyllite. Continue the process and get schist, then gneiss.

* For the last column on your chart, “Uses,” use Step 5.

*Metamorphic rocks are pretty. Enjoy working with them.

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