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Geology of the Anorthosite Massif in Chester County, Pennsylvania


O'Neill, Bernard Joseph (1952) Geology of the Anorthosite Massif in Chester County, Pennsylvania. Master's thesis, California Institute of Technology. doi:10.7907/CNT4-DT95.


The major objectives of this study have been to distinguish any variation within the anorthosite and to determine its age relationship with the adjacent rocks. Two distinct facies comprise the pre-Cambrian Honeybrook anorthosite: (1) a relatively pure anorthosite facies, and (2) a chilled border facies which is more mafic than the pure anorthosite facies. Quartz-monzonite of pre-Cambrian age has enveloped and penetrated the Honeybrook anorthosite, causing severe alteration in the anorthosite and forming a hybrid rock. The anorthosite is also intruded by a pre-Cambrian pegmatite dike. Metadiabase dikes of pre-Cambrian age cut both the anorthosite and quartz-monzonite. The structure of the anorthosite is doubtful. The meager data suggests a possible domical body. The primary magma yielding the anorthosite complex is assumed to have had the composition of gabbroic anorthosite. An upper chilled border of this composition developed. By gravity stratification during crystallization the mafic crystals settled to form gabbro and the plagioclase crystals remained suspended to form anorthosite.

Item Type:Thesis (Master's thesis)
Subject Keywords:(Geology); anorthosite, massif, Honeybrook Quadrangle, Appalachian Highlands, Piedmont province, Blue Ridge Mountains
Degree Grantor:California Institute of Technology
Division:Geological and Planetary Sciences
Major Option:Geology
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Engel, Albert Edward John (advisor)
  • Jahns, Richard H. (advisor)
Thesis Committee:
  • Unknown, Unknown
Defense Date:1 January 1952
Additional Information:Supplemental Files Information: Geology of the Honeybrook anorthosite, Pennsylvania: Supplement 1 from "Geology of the anorthosite massif in Chester County, Pennsylvania" (Thesis). Date(s) Collected: 1951. Geographic Location Bounding Box: -75.75 Degrees East; -75.87 Degrees West; 40.117 Degrees North; 40.05 Degrees South.
Record Number:CaltechTHESIS:04012010-091458107
Persistent URL:
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URLURL TypeDescription 1 in CaltechDATA: Geology of the Honeybrook anorthosite, Pennsylvania
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:5671
Deposited By: Tony Diaz
Deposited On:16 Apr 2010 21:45
Last Modified:11 May 2023 22:17

Thesis Files

PDF - Final Version
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PDF (Geologic map) - Supplemental Material
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