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TitleDeciphering the effects of zircon deformation and recrystallization to resolve the age and heritage of an Archean mafic granulite complex
AuthorRayner, N M; Sanborn-Barrie, M; Moser, D E
SourceMicrostructural geochronology: planetary records down to atom scale; by Moser, D E (ed.); Corfu, F (ed.); Darling, J R (ed.); Reddy, S M (ed.); Tait, K (ed.); Geophysical Monograph Series 232, 2018 p. 225-245, https://doi.org/10.1002/9781119227250.ch10
Year2018
Alt SeriesEarth Sciences Sector, Contribution Series 20160324
PublisherAmerican Geophysical Union
Edition1
Documentserial
Lang.English
Mediapaper; on-line; digital
File formatpdf
ProvinceNunavut
NTS45N/09; 45N/10; 45N/11; 45N/14; 45N/15; 45N/16; 45O/09; 45O/12; 45O/13; 45O/15; 45O/16; 45P; 46A; 46B; 46C/01; 46C/02; 46C/03; 46C/06; 46C/07; 46C/08; 46C/09; 46C/10; 46C/11; 46C/14; 46C/15; 46C/16; 46F/01; 46F/02; 46F/03; 46F/06; 46F/07; 46F/08; 46G/03; 46G/04
AreaSouthampton Island
Lat/Long WENS -85.5000 -80.0000 65.5000 63.5000
Subjectsgeochronology; geochemistry; tectonics; radiometric dating; uranium lead dating; zircon; geological history; tectonic history; tectonic evolution; crustal evolution; crystallization; magmatism; metamorphism; deformation; foliation; recrystallization; intrusions; emplacement; stress analyses; thermal history; strain; bedrock geology; lithology; metamorphic rocks; granulites; gneisses; mafic rocks; ultramafic rocks; metasedimentary rocks; marbles; silicates; semipelites; psammites; igneous rocks; intrusive rocks; granites; monzo-granites; granodiorites; monzonites; pegmatites; diorites; anorthosites; peridotites; pyroxenites; gabbros; sedimentary rocks; ironstone; inclusions; metamorphic facies; amphibolite facies; granulite facies; structural features; folds; antiforms; synforms; shear zones; faults, transcurrent; electron microscope analyses; electron diffraction analyses; trace element analyses; textural analyses; heavy mineral analyses; craton; crustal studies; crystallography; rock analyses, rare earth elements; Archean; Laurentia; Superior Province; Rae Craton; Kokumiak River Suite; ion microprobe analysis; cathodoluminescence analyses; syenogranites; leucodiorites; microstructural analyses; sensitive high-resolution ion microprobe analyses (SHRIMP); Precambrian; Proterozoic
Illustrationsgeoscientific sketch maps; photographs; photomicrographs; tables; Concordia diagrams; plots; geochemical plots; geochronological charts
ProgramRae Province, Boothia-Somerset, GEM2: Geo-mapping for Energy and Minerals
ProgramStrategic Investments in Northern Economic Development (SINED)
ProgramNSERC Natural Sciences and Engineering Research Council of Canada
Abstract(Summary)
Southampton Island, Nunavut, Canada, is uniquely situated to provide critical insight into the architecture and evolution of northeast Laurentia. However, extensive metamorphism at mid?crustal, upper amphibolite- to granulite-facies conditions has resulted in complex U-Pb systematics and challenges in establishing igneous versus metamorphic histories. Resolution of ambiguous geochronological results through integration of ion microprobe analyses and electron microscopy is applied to two texturally, chemically and morphologically distinct zircon populations from a high-grade layered mafic complex. Whereas U-Pb ion probe results for anhedral zircon grains define a discordia with an upper intercept of ca. 3.08 Ga and a lower intercept of ca. 1.80 Ga, equant grains yield a single age population at 1869 ± 8 Ma. The U-Pb data allow either an upper intercept crystallization age affected by Paleoproterozoic reworking, or an inherited component within a 1.87 Ga intrusion. Spatially correlated cathodoluminescence (CL), electron backscatter diffraction (EBSD), and ion probe trace element analyses support the former scenario. Regional deformational stresses combined with heating have created mildly deformed yet pervasively net-textured, inclusion-rich domains of up to 100% Pb loss sometimes accompanied by changes in the concentrations of other trace elements. This work highlights the utility of microstructural analysis of zircon to determine crustal affinity and gain insight into regional craton-scale evolution.
Summary(Plain Language Summary, not published)
This manuscript was invited for inclusion in the GSA Monograph entitled "Microstructural geochronology; lattice to atom-scale records of planetary evolution". It explores a unique zircon microstructure found in a mafic granulite from Arctic Canada and its associated complex U-Pb and trace element systematics. This was accomplished through an integrated ion probe (U-Pb and REE analyes) and electron microscopy (CL and EBSD) study. This work demonstrates how U-Pb ages, geochemical variations, microstructural measurement and textural observations of zircon can be integrated to arrive at reliable interpretations of complex data and to explain the sequence of mechanism that affected the zircons. It also highlights the importance of micro-scale studies on understanding big-picture questions about tectonics and regional geology in Nunavut.
GEOSCAN ID299655