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TitleFrobisher suite mafic, ultramafic and layered mafic-ultramafic sills, southern Baffin Island, Nunavut
AuthorLiikane, D A; St-Onge, M R; Rayner, N MORCID logo; Kjarsgaard, B AORCID logo; Ernst, R E; Kastek, N
SourceCanada-Nunavut Geoscience Office, Summary of Activities no. 2015, 2015 p. 21-32 Open Access logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20150317
PublisherNatural Resources Canada
File formatpdf
NTS26B/09; 26B/10; 26B/11; 26B/12; 26B/13; 26B/14; 26B/15; 26B/16; 26C; 26F; 26G; 26J; 26K
AreaBaffin Islands
Lat/Long WENS -70.0000 -66.0000 67.0000 64.0000
Subjectsgeneral geology; regional geology; economic geology; geochemistry; geochronology; structural geology; bedrock geology; metasedimentary rocks; orogenic regions; mafic metavolcanic rocks; metagabbros; metamorphic facies; amphibolite facies; granulite facies; ultramafic metavolcanics; sulphide deposits; sills; Baffin Island; Frobisher suite; Igneous Province; Ordovician; Paleozoic; Proterozoic; Precambrian
Illustrationslocation maps; photographs; photomicrographs; geochemical charts; geochronological charts
ProgramGEM2: Geo-mapping for Energy and Minerals Baffin Bedrock Mapping
Released2015 01 01
AbstractThis paper summarizes the 2015 field observations on the Frobisher suite of mafic and mafic-ultramafic sills of southern Baffin Island. In addition, it presents preliminary geochemical data from mafic/ultramafic samples collected during the 2014 field season on Meta Incognita Peninsula (see St-Onge et al. (2015) for report on 2014 field observations), as well as U-Pb geochronological results for a leucogabbroic sample from the upper portion of a layered mafic-ultramafic sill. The Frobisher suite sills are emplaced into the psammitic to pelitic metasedimentary strata of the Paleoproterozoic Lake Harbour Group, and vary in thickness from meters to one hundred meters. Layering within both mafic and mafic-ultramafic bodies was observed from centimeter- to meter-scale, and disseminated sulphides were noted in both the sills, and in some cases, the adjacent host psammite. Compositionally, the sills vary from pyroxenite/peridotite at the base, to gabbro/leucogabbro at the top. Similar sills have been documented throughout southern Baffin Island (including Foxe, Hall, & Meta Incognita peninsulas), and a mantle-derived magmatic province of this size may represent a new Large Igneous Province (LIP). A M.Sc. thesis characterizing the mafic, ultramafic, and layered mafic-ultramafic sills of the Frobisher suite using petrological, geochemical and geochronological analyses is currently being completed, and will be used to compare and improve existing regional tectonic models of middle Paleoproterozoic extension in the eastern Trans-Hudson Orogen.
Summary(Plain Language Summary, not published)
During 2015, geological observations, measurements, and sampling were completed on the newly recognized Frobisher suite, Baffin Island, Nunavut. This suite occurs as a group of sheet-like rock units (sills) that were intruded into older, rusty sedimentary rocks. A number of sills are hundreds of meters in thickness, and extend for several kilometers along the surface. Within individual sills, the rock type can vary from dark brown, dense rocks at the base to lighter, salt and pepper texture rocks at the top, with small but visible amounts of metals (sulphides) present. Similar rocks exist in northern Quebec, where they are associated with mineral deposits. Geochemistry from samples collected on Meta Incognita peninsula, reveal that there are four different groups of rocks within the Frobisher suite. To what degree these groups differ, especially with regard to mineral deposit potential, remains to be determined. Dating the Frobisher suite was attempted, but the complexity of the results only allow for a determination that these rocks are younger than 1900 million years.

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