LE3 .A278 2009

2009

Barr, Sandra

Acadia University

Master of Science

Masters

Geology

Earth & Environmental Sciences

The Late Silurian Landry Brook and Dickie Brook plutons and Charlo plutonic suite underlie a combined area of approximately 80 km2 in the northeastern part of the Ganderian Tobique-Chaleur tectonostratigraphic belt in northern New Brunswick. The Landry Brook pluton consists of gabbro to quartz diorite, medium-grained and porphyritic granodiorite, quartz monzodiorite to monzogranite, and monzogranite. A quartz monzodiorite sample yielded a U-Pb (zircon) crystallization age of 419.63 ± 0.23 Ma. The granodioritic units which host porphyry-type Cu-Mo mineralization are likely Early Devonian and not related to the main pluton. The Dickie Brook pluton consists of comagmatic leucogabbro to quartz gabbro, diorite to quartz diorite and quartz monzodiorite to monzogranite which yielded a U-Pb (zircon) crystallization age of 418 ± 1 Ma. REE-bearing apatite-diopside-magnetite veins at the northeastern margin of the pluton may have formed from exsolved phosphorus-rich hydrothermal fluids during cooling of the pluton. The Charlo plutonic suite is a group of small plutons and dykes located west of the Dickie Brook and Landry Brook plutons which consists mainly of diabase, quartz monzonite to monzogranite, rhyolite porphyry dated at 418 ± 1 Ma, and dacite porphyry. The dacite porphyry may be younger and cogenetic with the granodioritic units associated with the Landry Brook pluton. Chemical trends indicate that the quartz monzodiorite to monzogranite unit of the Landry Brook pluton, all of the units of the Dickie Brook pluton, and the quartz monzodiorite to monzogranite of the Charlo plutonic suite, as well as the volcanic host rocks of the Bryant Point and Benjamin formations, are co-magmatic. They formed during slab break-off and extension in the waning stages of the Salinic orogeny caused by the collision of Ganderia and Laurentia.

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https://scholar.acadiau.ca/islandora/object/theses:201