Document Type

Dissertation

Date of Award

1976

Keywords

Petrology, New York (State), Adirondack Mountains, Geology, Structural

Degree Name

Doctor of Philosophy (PhD)

Department

Geological Sciences

First Advisor

Rosemary J. Vidale

Second Advisor

Herman E. Roberson

Third Advisor

William D. MacDonald

Abstract

An outcrop geologic map of The Glen quadrangle has been produced at a scale of 1:24,000. This quadrangle is composed of a sequence of Precambrian rocks which were deformed and recrystallized under clinopyroxene-garnet granulite facies conditions during late Precambrian time. Metasedimentary rocks include calcic and dolomitic marble, metapelites, and metaquartzites. Rocks of known igneous origin include metagabbros, a metanorthosite-anorthositic metagabbro series, and minor unmetamorphosed diabase intrusives. In addition, there are a variety of mineralogically and texturally subdivided granitic-charnockitic gneisses of unknown origin. These rock sequences are correlated, where possible, with previous work in surrounding areas.

Estimates have been made of temperature and pressure conditions Hill during metamorphism. These are based on (1) the presence of sillimanite as the only aluminosilicate phase in the pelitic metasediments, and (2) a series of corona reactions in the olivine metagabbros which resulted in the formation of orthopyroxene + clinopyroxene + spinel, and garnet. The additional presence of associated garnet + clinopyroxene in other rock types precludes the possibility of the coronas having formed in cooling intrusives at temperatures higher than the surrounding rocks. Published experimental evidence, combined with field data, suggests temperatures and pressures of about 800-850° C. and 7-9 kb., and low PH2O.

A structural interpretation has been made which suggests a minimum of three superposed deformational events during metamorphism. An early isoclinal folding event (F1) was accompanied by the formation of an S1 foliation. The second event (F2) produced tight to open folds, and in some areas, an S2 foliation. The third event (F3) produced a broad warping of S2, and probably produced most of the mineral lineations in the quadrangle. A later event at low temperature and pressure produced numerous breccia zones, some of which have been interpreted as normal faults.

Comments

Plates 1-4 are available as additional files.

Additional Files
Plate 1.jpg (13936 kB)
Plate 2.jpg (3040 kB)
Plate 3.jpg (3605 kB)
Plate 4.jpg (2097 kB)
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