Masters Theses

Abstract

"The Wallamatogus Pluton, Maine, exhibits systematic variation in grain size, mineralogy, and phenocryst abundance (alkali-feldspar) from the margin to the center of the pluton. Three facies are recognized: 1) outermost, seriate, coarse-grained (Owe), 2) porphyritic medium- to fine-grained (Dwp ), 3) innermost, fine-grained equigranular (Dwf). These facies are concentrically arranged and their contacts are gradational. Muscovite and biotite occur in all facies; the outer two facies contain garnet, and tourmaline. Muscovite and biotite grains within micaceous enclaves compositionally overlap primary muscovite, suggesting that they are early-crystallized accumulations. Muscovite in multiphase clusters and secondary muscovite compositionally overlap, suggesting formation during post-crystallization alteration. High strain zones occur locally in the pluton. Mica and plagioclase grains are kinked; garnet and feldspar grains fractured and separated; quartz is recrystallized and commonly fills cracks in feldspar. Deformed garnet grains have high Ca contents compared to those within micaceous enclaves and those exhibiting magmatic equilibrium indicating re-equilibration during subsequent deformation.

Temperature estimates for magmatic crystallization, and for deformation, are constrained from combined petrographic analyses and garnet-biotite geothermometry. Early crystallizing garnets record liquidus temperatures of ~800°C, whereas the composition of garnet rims yield near solidus temperatures of ~600°C. Deformed garnets record temperatures of 400 to 450°C. These results better constrain the geologic history of the Wallamatogus Pluton and also, the terrane in which it intruded"--Abstract, p. iii

Advisor(s)

John P. Hogan

Committee Member(s)

David Wronkiewicz
F. Scott Miller

Department(s)

Geosciences and Geological and Petroleum Engineering

Degree Name

M.S. in Geology and Geophysics

Publisher

University of Missouri--Rolla

Publication Date

Spring 2001

Pagination

x, 175 pages

Note about bibliography

Includes bibliographical references (pages 172-174)

Rights

© 2001 Joy Kathleen Drake, All rights reserved.

Document Type

Thesis - Open Access

File Type

text

Language

English

Thesis Number

T 7907

Print OCLC #

47769681

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