Date of Award

8-2010

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 L. Gorring

Committee Member

Michael A. Kruge

Committee Member

Richard A. Volkert

Abstract

The Pompton Pink Granite is a small (~1 km2), post-orogenic granitoid body located in the New Jersey Highlands. It is a mildly peraluminous (ASI or aluminum saturation index, A/CNK = molar Al2O₃ / (CaO + Na₂O + K₂O) > 1.0) pluton composed of microcline, microperthite, quartz, oligoclase, epidote, biotite, and magnetite and is classified as a granite based on its mineral and geochemical composition using standard IUGS classification schemes. The Pompton Pink Granite shows similar major-element geochemistry to other A-type granitoids found in the New Jersey Highlands, but its trace­ element geochemistry distinguishes it from these other suites. The Pompton Pink Granite's high SiO₂ (72-74.5 wt%), total alkali (K₂O + Na₂O) > 9 wt%, K₂O/Na₂O ratio (2.0-3.1), Ba/Sr (3.3-7.3), FeOt/ (FeOt + MgO) (0.78 to 0.91), low CaO (0.6-1.3 wt%) and low Cr, Ni (< 8 ppm) are consistent with an A-type granite affinity, however the depletion in high-field-strength elements (HFSE) (Y + Nb < 6 ppm), Ga (< 17 ppm), relatively low total abundance of rare-earth-elements (REE) (43 to 464 ppm), and strong positive europium anomalies (Eu/Eu*= 1.5 to 11.8; only one sample, PPGl 1, has Eu/Eu* = 0.8) are distinctly different from typical A-type granites. The smooth variation and negative correlation between total REE content and positive Eu/Eu* is interpreted to be the result of variable loss of melt from a granitic crystal-liquid mush after emplacement as small, lense-shaped pods by a filter pressing and/or compaction process. One sample (PPG11) is considered to be the closest representative to the parental magma for the rest of the Pompton Pink Granite based on its high total REE content and small negative Eu anomaly. This sample has the strongest A-type geochemical affinity, but still retains a HFSE depleted signature, and thus it can be theorized that rocks similar to the calc-alkaline Losee Metamorphic Suite may have partially melted to produce the Pompton Pink Granite after the end of the main pulse of the Ottawan Orogeny.

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