Haley, James T. (2014) 1.3 Ga bimodal volcanism in Southeastern Labrador: Fox Harbour. Masters thesis, Memorial University of Newfoundland.
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The Fox Harbour bimodal volcanic package, newly discovered in 2010 during exploration by Search Minerals Inc. for rare earth elements (REE) is located in southeastern Labrador (northern Grenville Province). This package of rocks consists of three separate belts, known as the Road Belt, MT Belt, and South Belt. They are highly deformed, with an age of formation of 1.3 Ga, determined via U-Pb analysis of zircon from rhyolitic units. A metamorphic age of 1.05 Ga has also been determined for this package of rocks, which is taken to represent time that the Grenville Orogeny affected this area, exposing it to amphibolite facies metamorphism. The Grenville Orogeny is responsible for much of the observed deformation. The MT Belt has undergone the most exploration, due to the fact that the Foxtrot Deposit is located in this belt. This means that a detailed stratigraphy is available, and a much better correlation between rock types and lithogeochemistry is possible for this belt. Geochemically, many of the rhyolite units are peralkaline, determined geochemically, and by the presence of sodic amphiboles and sodic pyroxenes. The REE-bearing mineral in the volcanic units was determined to be a Y-Nb oxide called fergusonite, determined via electron probe micro-analysis (EPMA). Although not analyzed, allanite is also an important REE-bearing mineral found in all mineralized units. Zircon was also analyzed via EPMA, revealing that a zircon population consisting of large microporous grains was different than the general population observed in Fox Harbour. These microporous grains are believed to be 1.05 Ga based on the limited success in obtaining U-Pb dates from them. In-situ determinations of Hf isotopes on the 1.3 Ga zircon crystals reveal that partial melting of 1.5 to 1.9 Ga felsic crustal sources derived the Fox Harbour volcanic units. In-situ Hf determinations of the 1.05 Ga zircon crystal population suggest that these zircon have the same Hf-crustal evolution array for 1.5 to 1.9 Ga sources. This suggests that the 1.05 Ga metamorphism event was a closed system for Lu-Hf, and that there was no flux of REE into or out of the rocks during metamorphism.
|Item Type:||Thesis (Masters)|
|Additional Information:||Includes bibliographical references.|
|Department(s):||Science, Faculty of > Earth Sciences|
|Geographic Location:||Fox Harbour (N.L.)|
|Library of Congress Subject Heading:||Igneous rocks--Newfoundland and Labrador--Fox Harbour--Analysis; Metamorphism (Geology)--Newfoundland and Labrador--Fox Harbour; Mineralogy, Determinative--Newfoundland and Labrador--Fox Harbour; Rare earth metals--Newfoundland and Labrador--Fox Harbour|
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