Lab11 - Geol 331: Igneous & Metamorphic...

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Unformatted text preview: Geol 331: Igneous & Metamorphic Petrology El-Shazly, 2002 1 Lab 11 Metamorphism of Pelites In this lab, you will examine thin sections representing the metamorphism of pelitic rocks under two different facies series (in two separate problems) spanning the subgreenschist to granulite facies. Although both problems are fictive (i.e., I put together these samples in order to simplify things), the sequences displayed by these samples are commonly encountered in nature. I should also add that most of the samples you will study here were collected from the Blue Ridge in the southern Appalachians. I will give you a very brief outline of the geology and tectonic evolution of the southern Appalachians (Fig. 1) during the lab, from which you will understand why I opted to simplify the problem, and make it fictive. Problem 1: High T, low P facies series The mapped area contains a pelitic unit (e.g. shale) intruded by a large plutonic body. The dashed lines on the map are "isograds" or metamorphic zone boundaries. Sample numbers and their locations are given in Arabic numerals. Sample 77: 1- List the minerals occurring in this sample 2- What is the general texture of this sample? 1268 8900127 92AES1 x 77 78 Geol 331: Igneous & Metamorphic Petrology El-Shazly, 2002 2 Sample 78 1- List the minerals occurring in this sample 2- What is the general texture of this sample? How does it differ from that of sample 77? 3- Plot the peak metamorphic mineral assemblages of 77 & 78 on an AFM (or any other suitable) projection. (Assume that the feldspar in these two samples is in part K-spar). 92AES1 1- List the minerals occurring in this sample 2- What is the general texture of this sample? 3- Plot the peak metamorphic mineral assemblage on an AFM (or any other suitable) projection. 4- By comparing the AFM diagram for this sample with that for sample 92AES2, predict a reaction that could be responsible for the observed change in mineralogy. (You can check your results against Fig. 3). 5- On the P-T diagram provided (Fig. 3), show the stability range of the mineral assemblage of this sample. Geol 331: Igneous & Metamorphic Petrology El-Shazly, 2002 3 8900127 1- List the minerals occurring in this sample 2- What is the general texture of this sample?...
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This note was uploaded on 02/28/2012 for the course GLY 421 taught by Professor Staff during the Fall '11 term at Marshall.

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Lab11 - Geol 331: Igneous & Metamorphic...

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