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Title1.8 billion years of fluid-crust interaction: a zircon oxygen isotope record for the lower crust, western Churchill Province, Canadian Shield
AuthorPetts, D C; Moser, D E; Longstaffe, F J; Davis, W JORCID logo; Stern, R A
SourceLithos issue 192-195, 2014 p. 259-270,
LinksSupplemental Data - Données supplémentaire (Excel, 54 KB)
Alt SeriesEarth Sciences Sector, Contribution Series 20130469
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf; html
ProvinceBritish Columbia; Northwest Territories; Nunavut; Manitoba; Saskatchewan
Lat/Long WENS-112.5000 -111.7500 55.0000 54.7625
SubjectsCumberland batholith; Chesterfield block; Central Heearne supracrustal belt; Athabasca mylonite zone; Pehnryn group; Piling group; Snowbird Tectonic; Wathaman batholith
ProgramGEM: Geo-mapping for Energy and Minerals Diamonds
AbstractThe western Churchill Province of the Canadian Shield experienced a prolonged and complex formation history (ca. 4.04 to 1.70 Ga), with evidence for multiple episodes of orogenesis and regional magmatic activity. Here we report on the oxygen isotopic compositions of garnet and zircon recovered from lower crustal xenoliths, which have U-Pb ages between ca. 3.5 to 1.7 Ga. Zircons from four metabasite xenoliths from the Rankin Inlet sample suite have ?18O values ranging from +5.7 to +8.6 ¿. Zircon from three metatonalite/anorthosite xenoliths and five metabasite xenoliths from the Repulse Bay sample suite have ?18O values of +5.6 to +8.3 ¿. High ?18O values (> +6.0¿) measured for the oldest igneous zircon cores (ca. 3.5 Ga and 3.0-2.6 Ga) from three metatonalite/anorthosite xenoliths indicate zircon crystallization from evolved metatonalite/anorthosite protolith magmas that were generated from or had assimilated supracrustal rocks, which interacted previously with surface-derived fluids. Mantle-like ?18O values of ca. 2.9-2.6 Ga igneous zircon cores from one metabasite xenolith suggest formation from a juvenile basaltic/gabbroic magma. The mantle-like ?18O values of ca. 2.0-1.9 Ga metamorphic cores from one metabasite xenolith indicate a basalt/gabbro protolith and localized reworking of the lower crust caused by regional-scale plate convergence. The wide range of ?18O values for ca. 1.75-1.70 Ga metamorphic rims (identified in all xenoliths) indicates regional transient heating and reworking of juvenile and evolved, supracrustal-derived crust, induced by magmatic underplating along the crust-mantle boundary.
Summary(Plain Language Summary, not published)
Diamonds are brought to the surface from deep (>100 km) regions beneath the continents in kimberlite pipes. Diamonds form as a function of the geological history of the area, but subsequent geological processes may lead to their destruction. Rare fragments of the deep continents may be carried to the surface along with diamonds in kimberlite. Study of the geochemical characteristics of these fragments allows assessment of the history that the continent experienced, and hence insight about the diamond potential of a region. This study describes complex minerals from the area beneath Rankin Inlet and Repulse Bay, Nunavut, that demonstrate significant disturbance of the deep crust more than 1 billion years after its initial formation.

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