Date of Graduation

5-2016

Document Type

Thesis

Degree Name

Master of Science in Geology (MS)

Degree Level

Graduate

Department

Geosciences

Advisor

Gregory Dumond

Committee Member

Doy L. Zachry

Second Committee Member

Adriana Potra

Keywords

Earth sciences; Canada; Geochronology; La-icpms; Paragneiss; Provenance

Abstract

U-Pb crystallization ages of metamorphic and detrital zircons from all three paragneiss samples fall into the range of ca. 1.85-2.59 Ga, excluding two much older grains. Evidence suggests that the paragneiss of Grollier Lake record deformation exclusively from the Taltson and Trans-Hudson orogenies. It is apparent from geochronological data that the Taltson orogeny played an exceedingly larger role in the deformation of these rocks than the Trans-Hudson. Deposition of the paragneiss protoliths most likely culminated between ca. 2037-1994 Ma with metamorphism ceasing by 1852.1 ± 11.1 Ma. The oldest overgrowth considered to be concordant is 1994 ± 12 Ma and interpreted to represent the first signature of burial facilitated by the Taltson orogeny. U-Pb crystallization ages ranging from ca. 1872-1900 Ma can be attributed to metamorphisms from both the late Taltson or early Trans-Hudson orogenies given that the transition between these events is hard to delineate. Zircons dated > ca. 2.04 Ga are detrital in origin with U-Pb crystallization ages for these grains possibly being discordant as supported by the concordia diagrams. However, these ages can still be explained by provenance from sources such as the ca. 2.17-2.13 Ga Rutledge River basin to the west of Grollier Lake, and the ca. 2.3 Ga Arrowsmith subduction-related plutons north of Lake Athabasca. Older zircons (2955.6 ± 10.7 Ma and 3078 ± 13.9 Ma) in the migmatitic paragneiss are inferred to be inherited from Neoarchean and early Paleoproterozoic crust below. It is possible that rocks of the lower structural levels will record deformation from the Arrowsmith orogeny.

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