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TitleUranium-lead geochronology of eastern Meta Incognita Peninsula, southern Baffin Island, Nunavut
AuthorRayner, N M
SourceCanada-Nunavut Geoscience Office, Summary of Activities 2015, 2015 p. 95-106
LinksOnline - En ligne
Year2015
Alt SeriesEarth Sciences Sector, Contribution Series 20150293
PublisherCanada-Nunavut Geoscience Office
Documentserial
Lang.English
Mediapaper
File formatpdf
ProvinceNunavut
NTS25P; 25I
AreaMeta Incognita Peninsula; Baffin Island
Lat/Long WENS-66.0000 -64.0000 64.0000 62.0000
Subjectsgeochronology; radiometric dating; uranium lead dating; uranium lead dates; Precambrian; Proterozoic
Illustrationslocation maps; photographs; plots; photomicrographs
ProgramBaffin Bedrock Mapping, GEM2: Geo-mapping for Energy and Minerals
AbstractThis paper presents new U-Pb geochronology data from three sedimentary rocks and three plutonic rocks collected during recent bedrock geological mapping of eastern Meta Incognita Peninsula, Baffin Island, Nunavut. A quartzite (sample 14SAB-S013A), contiguous with the type area of the Lake Harbour Group near Kimmirut, is characterized by an exclusively Archean detrital zircon profile, dominated by ca. 2.82 Ga detritus. Calcareous quartzite from the central part of the peninsula (sample 14SAB-O103B) includes detrital ages of 2.7 Ga, 2.6-2.5 Ga, 2.35 Ga, 2.1 Ga and 1.93-1.91 Ga. The maximum age of deposition of the calcareous quartzite is 1913 ±17 Ma. A grey, sandy quartzite horizon (sample 14SABR108B), from an outcrop of psammite/leucogranite, is dominated by Orosirian age (2050-1800Ma) zircon. Acomponent of ca. 1.85 Ga zircon is interpreted to reflect partialmelting and emplacement of nearby leucogranite.Given their proximity to the type area, and similar lithological association and geological setting, the metasedimentary rocks on eastern Meta Incognita Peninsula are correlated with the Lake Harbour Group. A megacrystic biotite-orthopyroxene monzogranite (sample 14SAB-O071A) is interpreted to have crystallized at 1845 ±19Ma. Amegacrystic biotite-magnetite monzogranite (sample 14SAB-R62A) is interpreted to have a crystallization age of 1865 ±10Ma, with an older 1896Ma component representing an inherited or possibly autocrystic phase.Apink, sugarytextured biotite-magnetite monzogranite (sample 14SAB-O049A) is cautiously interpreted to have crystallized at 1871 ±4 Ma followed bymetamorphism that resulted in resetting of zircon U-Pb systematics. Despite their relatively simple and homogeneous appearance in the field, complex geochronological results made interpretation of the crystallization ages of plutonic phases from Meta Incognita Peninsula challenging. The highest grade, most deformed samples discussed in this paper yielded the youngest ages. This emphasizes the need for careful field observations of crosscutting relationships when establishing a field chronology for plutonic rocks.
Summary(Plain Language Summary, not published)
Knowledge of the age of rocks (geochronology) is critical in the making of a geologic map as it allows scientists to add the measurement of time to their field observations and permits comparisons with rocks elsewhere of similar age and appearance. This report presents ages from 6 samples across eastern Meta Incognita Peninsula, southern Baffin Island, as part of a geological mapping project led by the Geological Survey of Canada in partnership with the Canada-Nunavut Geoscience Office. The results include ages for metamorphosed sedimentary rocks across the entire width of eastern Meta Incognita Peninsula which are shown to be Paleoproterozoic in age (approx. 2 billion years). These rocks are prospective for base and/or precious metals and are similar in age and appearance to sedimentary rocks to the west near Kimmirut that host coloured gemstones. The results presented in this report contribute to the overall understanding of the geological framework and mineral exploration potential of Meta Incognita Peninsula, thereby reducing risk to exploration and resource development.
GEOSCAN ID297293