Geochemistry and Protolith Determination of the Hypersthene-Quartz-Oligoclase Gneiss from the Hudson Highlands, New York
Date of Award
Master of Science (MS)
College of Science and Mathematics
Earth and Environmental Studies
Thesis Sponsor/Dissertation Chair/Project Chair
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).
Miller, Kathleen, "Geochemistry and Protolith Determination of the Hypersthene-Quartz-Oligoclase Gneiss from the Hudson Highlands, New York" (2014). Theses, Dissertations and Culminating Projects. 545.