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Iso Grades, Index Minerals, Facies Series - Lecture Notes | GEOL 320, Lab Reports of Geology

Central Washington University (CWU)Geology
Prof. Christopher Mattinson

Material Type: Lab; Professor: Mattinson; Class: Rocks and Minerals; Subject: Geology; University: Central Washington University; Term: Unknown 2008;

Typology: Lab Reports

Pre 2010

Uploaded on 08/18/2009

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GEOL 320-Metamorphism
1
NAME ________________________
Rocks and Minerals
Lab 8: Isograds, Index Minerals, Facies Series, P-T-t paths, and other
Fun Topics
DUE DATES
At the beginning of lab next week.
OBJECTIVES
To define how protolith and facies impact mineral assemblages
To review and analyze the following concepts: index mineral, isograd, facies, metamorphic
facies series/metamorphic field gradient
To determine how metamorphism impacts texture
To explain P-T-t paths
To define equilibrium and metastable state
ASSIGNMENT (ANSWER QUESTIONS DIRECTLY ON LAB. IF NECESSARY
ATTACH SEPARATE SHEETS.)
1. [12 points] List four of the main protolith types for metamorphic rocks and contrast the minerals one would find
if each of these protoliths was metamorphosed to the greenschist facies.
PROTOLITH 1:
PROTOLITH 2:
PROTOLITH 3:
PROTOLITH 4:
pf3
pf4
pf5
pf8

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Download Iso Grades, Index Minerals, Facies Series - Lecture Notes | GEOL 320 and more Lab Reports Geology in PDF only on Docsity!

NAME ________________________

Rocks and Minerals

Lab 8: Isograds, Index Minerals, Facies Series, P-T-t paths, and other

Fun Topics

DUE DATES

At the beginning of lab next week.

OBJECTIVES

 To define how protolith and facies impact mineral assemblages

 To review and analyze the following concepts: index mineral, isograd, facies, metamorphic

facies series/metamorphic field gradient

 To determine how metamorphism impacts texture

 To explain P-T-t paths

 To define equilibrium and metastable state

ASSIGNMENT (ANSWER QUESTIONS DIRECTLY ON LAB. IF NECESSARY

ATTACH SEPARATE SHEETS.)

  1. [12 points] List four of the main protolith types for metamorphic rocks and contrast the minerals one would find if each of these protoliths was metamorphosed to the greenschist facies. PROTOLITH 1: PROTOLITH 2: PROTOLITH 3: PROTOLITH 4:
  1. For the four main protoliths defined in your text, answer the following questions assuming that the relevant metamorphic facies is greenschist. It may help to refer to the mineral formulae in your text, found on pgs. 362-363. a. [3 points] Explain why actinolite is more likely to form from a mafic protolith whereas tremolite is more likely to form from an ultramafic protolith. b. [2 points] Why is muscovite found in metamorphosed mudrocks (pelites)? c. [2 points] Why is calcite only found in metamorphosed calcareous rocks? d. [5 points] What evidence is there that water-rich fluids are typically present either during formation of these protoliths and/or during greenschist metamorphism?
  2. This question is designed to allow you to contrast the conditions of amphibolite vs. eclogite facies metamorphism. Answer the questions below. a. [4 points] Describe the differences in P-T conditions for these two facies. Be specific—give P and T ranges for both.
  1. Refer to Figure 17-2 in your text (pg. 342) and associated reading and class notes. Based on these, answer the following questions. a. [4 points] Define index mineral and isograd. b. [4 points] Figure 17-2 illustrates the Barrovian Zones. Describe what these zones are and why they are important. c. [6 points] Figure 1 is a very simple representation of a metamorphic map. Based on the information given, draw in appropriate isograds for the index minerals garnet, staurolite, kyanite, sillimanite. One rock specimen represents each metamorphic zone. Describe how P and T change in this terrane and where one would expect to find the highest grade metamorphic rocks and why. Hand in figure 1 with your lab. Based on your examination of the map and hand specimens, identify the map symbol corresponding to each index mineral: _____garnet, _____staurolite, _____kyanite, _____sillimanite.
  1. Based on our discussions in class and your reading, answer the following questions about facies series (the equivalent “modern” term is metamorphic field gradient). a. [3 points] Define facies series/metamorphic field gradient. b. [4 points] List two examples of facies series and describe the differences between the two. Be specific about the differences. c. [3 points] Explain the importance of the concept of facies series/metamorphic field gradient.
  2. An important consideration in understanding metamorphism involves the path that a particular rock package takes during its full metamorphic history. Because time is involved, this path is commonly referred to as a P-T-t (Pressure, Temperature, time) path. Refer to pages 348-350 and Figure 17-10 in your text. a. [3 points] Identify the three phases in a typical regional metamorphic P-T-t path b. [9 points] For each of these phases, and describe the P-T changes that occur and explain why the P-T path looks the way it does.
  1. We have recently discussed the concepts of metamorphic assemblages and reactions. Define the following terms: a. [3 points] equilibrium b. [3 points] metastable state