Date of Award

5-2014

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Science and Mathematics

Department/Program

Earth and Environmental Studies

Thesis Sponsor/Dissertation Chair/Project Chair

Matthew Gorring

Committee Member

Stefanie Brachfeld

Committee Member

Michael Kruge

Abstract

The hypersthene-quartz-oligoclase gneiss of the Hudson Highlands, NY mapped by Dodd (1965) has been of unknown origin due to complex field relations resulting from metamorphism and deformation during the Ottawan Orogeny, and a lack of geochemical data. The rock types in the Hudson Highlands and New Jersey Highlands are grouped into four general categories: metasedimentary gneisses, metaigneous gneisses, quartzofeldspathic gneisses, and syn-tectonic intrusive granitoid rocks (Dodd, 1965). Major element geochemistry and mineralogy of the Losee Metamorphic Suite of the physically contiguous New Jersey Highlands is similar to that of the hypersthene-quartzoligoclase gneiss of the Hudson Highlands. Based on the high A120 3, CaO, Na20/K20 ratios, and mineralogical similarities between these units suggests an igneous protolith is likely the source of the hypersthene-quartz-oligoclase gneiss rather than a sedimentary protolith. Geochemical diagrams reveal that the hypersthene-quartz-oligoclase gneiss is of calc-alkaline affinity, ranges in composition from basalt to dacite, and is indicative of a convergent margin tectonic setting. Trace element data plotted on multi-element diagrams and Rare Earth Element (REE) plots are indicative of a continental arc subduction zone setting for the hypersthene-quartz-oligoclase gneiss. Variable heavy rare earth element (HREE) enrichment and depletion in the samples indicates that crystal fractionation from a single parent magma was unlikely. Rather, the REE patterns suggest that the magmas that formed the hypersthene-quartz-oligoclase gneiss were generated from different source rocks (e.g. upper mantle and lower mafic continental crust) and at varied depths in a continental arc setting (Winter, 2010).

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