This thesis has no Abstract
INTRODUCTION (pp.1-4)
Mineralogical, textural and chemical changes of ultramafic rocks in response to regional deformation and metamorphism are, at best, imperfectly known (Miyashiro, 1973, p. 30). In Vermont, which has an extremely prominent and well-exposed belt of ultramafics (fig. 1), investigation of these rocks has largely been directed toward such processes as serpentinization, steatitization, and the formation of metasomatic zones at the contacts with country rocks. With few exceptions, there is a lack of detailed descriptions of regional metamorphic textures, mineralogy, and structures developed in the Vermont ultramafic rocks.
It is the main purpose of this thesis to describe the mineralogical and textural changes that accompany regional metamorphism and deformation in the large ultramafic body at East Dover, Vermont. Serpentinization processes or the effects of hydrothermal alteration are not dealt with in detail, although some observations are made on these topics.
Two field seasons (1973-1974) were spent in an area approximately 6 x 3 km in and around East Dover, Vermont. When existing geologic maps of the area (Skehan, 1961; Vermont State Geologic map, 1961) were found to lack sufficient detail for these studies, field mapping was initiated to help correlate the petrology and structure of the body. Indeed, as mapping continued it became evident that complete analysis of the structural complexities of the body was far beyond the scope of this research. However, mapping of different rock types, measurement and description of the most prominent-foliations, and a preliminary analysis of folding in the body were carried out to provide basic structural data.
Structures in the country rocks at or near the contacts were studied to gain a better idea of the relationships of the ultramafic body to the country rocks. A preliminary comparison of structural elements in the ultramafic and country rocks was also attempted.
Only cursory petrographic examination of the country rocks was undertaken, mainly to determine the metamorphic grade and general rock types that surround the ultramafic body. The textures and mineralogy of the ultramafic rocks were studied in detail to provide information essential to interpreting the metamorphic and deformational history of the body. In this regard, previous petrographic work on these rocks was found to be inadequate and inaccurate.

Concluding Remarks:(pp.98-99)
In summary, the following can be said about the petrology of the East Dover ultramafic rocks:
1. The distribution of olivine textural and chemical variations, and chrome spinel textural. variations can be attributed to differing intensities of recrystallization.
2. Serpentinization is uniform over large areas of the ultramafic bodies but must be described as randomly developed with respect to the margins.
3. The only pyroxene now observed is metamorphic in origin (but may be pseudomorphic).
4. The distribution of magnetite is not simply related to the development of serpentine, as a simple serpentinization process would imply. It may, rather, be a function of removal of the iron component from olivine during recrystallization, or differing partial pressures of oxygen during serpentinization.
 5. A stage of tremolite development (uralitization) occurred at a different time than the development of T2 olivine and diopside.

TABLE OF CONTENTS
ACKNOWLEDGMENTS ii
LIST OF TABLES vi
LIST OF FIGURES vii
INTRODUCTION 1
REGIONAL GEOLOGIC SETTING 5
GEOLOGIC SETTING: THE EAST DOVER AREA 7
A SHORT HISTORY OF THE STUDY OF VERMONT ULTRAMAFIC ROCKS 8
Early Investigations 8
Later Investigations 10
A REVIEW OF PREVIOUS INVESTIGATIONS OF THE ULTRAMAFIC ROCKS AT EAST DOVER, VERMONT 13
MEGASCOPIC APPEARANCE OF THE ROCKS AT EAST DOVER 21
Country Rocks 21
Ultramafic Rocks 21
STRUCTURAL ASPECTS OF THE EAST DOVER ULTRAMAFIC BODIES AND SURROUNDING COUNTRY ROCKS 24
Foliations Visible in the Country Rocks Surrounding the Ultramafic Body 24
Folding Visible in the Country Rocks 30
B2 Folds 30
B3 Folds . 32
Lineations 32
Foliations Visible in the Ultramafic Rocks 33
Macroscopic Foliations 33
Microscopic Foliations 33
Folding Visible in the Ultramafic Rocks 37
Folds 1 37
Folds 2 38
Discussion of Contact Relationships, Mappcd Boundaries of the Ultramafic Bodies ard a Review of Previ ous Workers Mapped Boundaries 38
A Discussion. of Some Specific Structural Aspects of the Ultramafic Bodies at East Dover 41
Correlation of Structural Elements Between Country Rocks and the Ultramafic Rocks 45
Concluding Remarks 45
PETROLOGIC ASPECTS OF THE EAST DOVER ULTRAMAFIC BODIES AND SURROUNDING COUNTRY ROCKS 48
Petrography of the Country Rocks Surrounding And Contained Within the Ultramafic Rocks 48
Quartz-mica Schists (Metapelitic Rocks) 48
Quartz-epidote Amphibolites 49
Mica-albite (Porphyroblast) Schist 50
Petrography of the Ultramafic Rocks 53
Mineralogy of the Serpentinized Dunites 53
Serpentine 53
Discussion of serpentine distribution 57
Chlorite 57
Olivine 58
Chemical variations of olivines 67
Discussion of olivine textural and chemical variations 67
Chrome spinel and magnetite 70
Magnetite 80
Discussion of magnetite and chrome spinel textural variations 81
Clinopyroxene 84
Clinozoisite 90
Carbonate 91
Smectite 91
Mineralogy of the Clinozoisite-Hornblende Unit 91
The Ultramafic "Breccia" 91
Discussion and Summary of Petrologic Aspects 93
Primary assemblages 95
Metamorphic assemblages 96
Concluding Remarks 98
RELATIONSHIP OF MAGNETIC ANOMALIES TO PETROLOGY 100
APPENDIX I 107
X-ray Diffraction Methods Used To Determine Fo Content of Olivines 107
APPENDIX II 111
A Note On The Optical Determination Of 2V In High Mg Olivines (Fosterites) 111
Method 11l
Olivine Determinations 111
Discussion 111
REFERENCES 115

Hoffman, M.A., 1975. A Study of Some Petrologic and Structural Aspects of the East Dover Ultramafic Bodies, South Central Vermont. Unpublished MSc. thesis, State University of New York at Albany. 120pp., +viii; 1 folding plate (map).
University at Albany Science Library call number:  SCIENCE Oversize (*) QE 445 H63X

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