Name: Grade:
GEOL 101 - Physical Geology Laboratory
METAMORPHIC ROCKS PRELAB #6
PRELAB SECTION To be completed before labs
starts:
I. Introduction
& Purpose:
The purpose of this laboratory exercise
is to become familiar with identifying common metamorphic rocks and
understanding their depositional origin.
In this lab you will learn to identify metamorphic rocks in hand samples
from their physical properties. You will
become familiar with the most common metamorphic rock-forming minerals and
processes. The nature and origin of
metamorphic rocks, the major types of metamorphic rocks, and their structures,
and the connection between plate tectonics and metamorphic rocks in the rock
cycle will be explored.
II. General
Overview and Classification of Metamorphic Rocks
A. Defining Metamorphism:
Directions: Answer the following (from lecture and lab text: see page 133):
1) Define "metamorphism" _________________________________________________
2) Every metamorphic rock has a _________________ rock (or protolith) - the original rock
type that was metamorphosed into the resultant metamorphic rock, i.e. the source rock.
B. Conditions of Metamorphism:
Metamorphic rocks form as a result of changing crustal conditions, e.g. increasing pressures and/or
temperatures, that are between that of igneous and sedimentary rock-forming environments.
1). The four major agents of change that cause rocks to metamorphose (see page 133):
a) _____________ , b) _____________ , c) _____________ , and/or d) ______________
C. Processes of Metamorphism:
Metamorphic processes that are forming the metamorphic rocks occur at various scales within the
Earth, and the type of internal earth agents involved is used to define the type of metamorphism.
One type is related to magmatism, and the other type is related to faulting and mountain building.
1) The two major types of metamorphism that are agent-dependent (page 134):
a) ________________________ , and b) ________________________
____________________________________________________________________________________________________________________
1) Classification
and identification of metamorphic
rocks are based upon two major physical criteria:
a) ______________________ , and b) _______________________
2) Metamorphic rocks are divided into two major groups based on whether the rock has a layered
versus non-layered texture. See Figure 7.4, page 136. Special alternative names for these are:
a) Layered = ___________________ and b) Non-layered = ___________________
E. Foliated Metamorphic Rocks
1) Metamorphic rocks that possess a foliated and/or layered fabric have a crystalline texture
consisting of elongate and/or platy crystals that all share a preferred orientation within the rock.
Metamorphic rock s that have foliated/layered fabrics originate in two types of metamorphic
environments: Regional Metamorphism (RM) and Dynamic Metamorphism (DM).
2) There are four common types of metamorphic rock s that have foliated-layered textures. Each
foliation type is unique and represents a progressive increasing scale of intensity of regional
metamorphism as go from slate to gneiss. The textural character of foliated and/or layered
metamorphic rock can vary greatly as a function of 1) grain size, 2) degree of preferred
orientation of the rock's mineral crystals, and 3) degree of layered segregation of light minerals
from dark minerals.
3) The foliated/layered metamorphic rocks are classified primarily upon texture, with mineralogy
a secondary criteria. There are four visually distinctive types of foliated rocks (listed below).
Directions: Describe the texture and mineralogy of the four foliated rock types (see Figure 7.15)
Rock Name Textural Features Rock Mineralogy
1. Slate _______________________________________ ________________________
2. Phyllite ______________________________________ ________________________
3. Schist _______________________________________ ________________________
4. Gneiss _______________________________________ ________________________
Please note that there are infinite shades of gray between these four types no sharp divisions
1) Metamorphic rocks that have non-foliated (non-layered) textures originate in two types of
metamorphic environments: regional metamorphism (RM) and contact metamorphism (CM).
Note that
the nonfoliated metamorphic rocks that form by regional metamorphism RM are
mostly
mono-mineralic (mostly of one mineral type), having mineral crystals that are neither platy nor
tabular, such as quartz and calcite. Note that amphibolite and serpentinite may exhibit foliation.
2) As noted above, the non-foliated (non-layered) metamorphic rocks consist of equant shaped
mineral crystals that have no preferred orientation or arrangement. These rocks have a massive,
homogenous "crystalline" texture, much like that of either, phaneritic granite, or aphanitic basalt.
The non-foliated metamorphic rocks are classified primarily upon mineral composition.
3) There are four common types of metamorphic rock s that have non-foliated/ non-layered fabrics:
Directions: Describe the texture and mineralogy of the four non-foliated rock types (see Fig. 7.15)
Rock
Name Textural
Features Rock
Mineralogy
1. Quartzite _______________________________________ ________________________
2. Marble _______________________________________ ________________________
3. Amphibolite ____________________________________ ________________________
4.
Serpentinite ____________________________________ ________________________
METAMORPHIC ROCKS IDENTIFICATION - IN-LAB SECTION
I. Preliminary Examination
of the Metamorphic Rock Types:
A. Introduction: The instructor has assembled 2 reference collections of metamorphic rocks for
you to become familiarized with the two major types of metamorphic rocks: foliated and nonfoliated.
Directions: Carefully study each rocks: 1) physical characteristics, including texture and
composition, and 2) metamorphic origin: the rocks metamorphic environment and parent rock.
Make observational notes of the samples. Discuss your observations with your group.
A. Exercise 1 - Sample Group X has representative hand samples of each of
the foliated rock
types. Study each sample carefully and make some
brief descriptions of the rock's character
(texture,
foliated fabric & minerals). Carefully
study pages 137-139 for reference.
Observational
Notes
Sample #s X1 and X2 = Slate
_____________________________________________________
Sample #s X3 and X4 =Phyllite
_____________________________________________________
Sample
#s X5, and X6 = Schist _____________________________________________________
Sample #s X7 and X8 = Gneiss ____________________________________________________
B. Exercise 2 Compare and contrast the foliated
metamorphic rocks in Sample Collection
X.
Question: How does slate differ from both phyllite and
schist?
Question: How does gneiss differ from the other three foliated rocks?
Question: What are the main criteria you use to distinguish between these four
rock types?
III. Non-Foliated-Non-Layered
Metamorphic Rocks
A. Exercise 1 - Sample
Collection Y has representative
hand samples of the nonfoliated rock
types. For each hand sample, briefly describe the rock's
character (texture, fabric, minerals)
Observational
Notes
Sample #s Y1 = Quartzite
____________________________________________________
Sample #s Y2 = Marble
______________________________________________________
Sample
#s Y3 = Amphibolite __________________________________________________
Sample #s Y4 = Serpentinite
_________________________________________________
B. Exercise 2 Compare and contrast nonfoliated
metamorphic rocks in Sample
Collection Y.
Question: How does quartzite differ from marble? How are they similar?
Question: How does amphibolite differ from serpentinite? How are they similar?
Question: What are the main criteria you use to distinguish between these four
rock types?
IV. Procedure for Describing and
Identifying Metamorphic Rocks:
A 4-Step chart for the analysis and
classification of metamorphic rocks is found in Figure 2.33
on page
32 . Use this chart, and the additional
directions found on page 32 to help you learn to
identify
metamorphic rocks both, in hand sample and in the field.
A. Four-step Identification
Procedure - A brief description of
the 4 determinant steps:
Step 1: Texture = a) Foliated or Non-Foliated? AND b) Coarse-, medium-, or fine-grained?
Step 2: Rock Composition = Identifiable Minerals?
Step
3: Name the Rock.
Step
4: Name the Most Likely Parent
Rock.
V. Identifying 9 Unknown
Metamorphic Hand Samples
Instructions: Sample Collection Z has nine unknown metamorphic rock samples. Using the
4-step procedure outlined above, complete the worksheet chart below for all eight unknown samples.
Be sure to Circle only the appropriate texture and mineralogy. List rock name and parent rock.
Unknown Metamorphic
Rock Hand Samples Worksheet Collection Z
a) Texture: Foliated or Non-foliated? AND Fine-Grained. or Medium-Gr. or Coarse-Gr.?
b) Mineralogy: Quartz; Feldspar; Mica; Amphibole; Carbonate; Garnet; Serpentine; None Obs.
c) Other distinctive features = ______________________________________________________
d) Rock name _______________________________
e) Most likely parent rock ______________________________
a) Texture: Foliated or Non-foliated? AND Fine-Grained. or Medium-Gr. or Coarse-Gr.?
b) Mineralogy: Quartz; Feldspar; Mica; Amphibole; Carbonate; Garnet; Serpentine; None Obs.
c) Other distinctive features = ______________________________________________________
d) Rock name _______________________________
e) Most likely parent rock ______________________________
a) Texture: Foliated or Non-foliated? AND Fine-Grained. or Medium-Gr. or Coarse-Gr.?
b) Mineralogy: Quartz; Feldspar; Mica; Amphibole; Carbonate; Garnet; Serpentine; None Obs.
c) Other distinctive features = ______________________________________________________
d) Rock name _______________________________
e) Most likely parent rock ______________________________
a) Texture: Foliated or Non-foliated? AND Fine-Grained. or Medium-Gr. or Coarse-Gr.?
b) Mineralogy: Quartz; Feldspar; Mica; Amphibole; Carbonate; Garnet; Serpentine; None Obs.
c) Other distinctive features = ______________________________________________________
d) Rock name _______________________________
e) Most likely parent rock ______________________________
a) Texture: Foliated or Non-foliated? AND Fine-Grained. or Medium-Gr. or Coarse-Gr.?
b) Mineralogy: Quartz; Feldspar; Mica; Amphibole; Carbonate; Garnet; Serpentine; None Obs.
c) Other distinctive features = ______________________________________________________
d) Rock name _______________________________
e) Most likely parent rock ______________________________
Sample#
Z6
a) Texture: Foliated or Non-foliated? AND Fine-Grained. or Medium-Gr. or Coarse-Gr.?
b) Mineralogy: Quartz; Feldspar; Mica; Amphibole; Carbonate; Garnet; Serpentine; None Obs.
c) Other distinctive features = ______________________________________________________
d) Rock name _______________________________
e) Most likely parent rock ______________________________
a) Texture: Foliated or Non-foliated? AND Fine-Grained. or Medium-Gr. or Coarse-Gr.?
b) Mineralogy: Quartz; Feldspar; Mica; Amphibole; Carbonate; Garnet; Serpentine; None Obs.
c) Other distinctive features = ______________________________________________________
d) Rock name _______________________________
Most likely parent rock ______________________________e)
a) Texture: Foliated or Non-foliated? AND Fine-Grained. or Medium-Gr. or Coarse-Gr.?
b) Mineralogy: Quartz; Feldspar; Mica; Amphibole; Carbonate; Garnet; Serpentine; None Obs.
c) Other distinctive features = ______________________________________________________
d) Rock name _______________________________
e) Most likely parent rock ______________________________
Sample# Z9
a) Texture: Foliated or Non-foliated? AND Fine-Grained. or Medium-Gr. or Coarse-Gr.?
b) Mineralogy: Quartz; Feldspar; Mica; Amphibole; Carbonate; Garnet; Serpentine; None Obs.
c) Other distinctive features = ______________________________________________________
d) Rock name _______________________________
e) Most likely parent rock ______________________________
VI. METAMORPHIC Rock
Laboratory Reflection
Directions:
Write a reflection (minimum 100 words in length) about your experience
in doing the rock exercises lab today.
Include the following: 1) What was the purpose of the lab?; 2) What did you learned from this laboratory?; 3) What
did you find interesting? 4) What were the problems and challenges you
encountered; and 5) Your opinion on how this lab was
designed and executed.