1.8 billion years of fluid-crust interaction: A zircon oxygen isotope record for the lower crust, western Churchill Province, Canadian Shield

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• 作者：Duane C. Petts^a ; ^{petts@ualberta.ca" class="auth_mail} ; Desmond E. Moser^a ; Frederick J. Longstaffe^a ; William J. Davis^b ; Richard A. Stern^c
• 关键词：Oxygen isotopes ; Zircon ; Churchill Province ; Lower crust ; Granulite xenoliths ; Archean craton evolution
• 刊名：Lithos
• 出版年：April, 2014
• 年：2014
• 卷：192-195
• 期：Complete
• 页码：259-270
• 全文大小：1978 K

文摘

The 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 and 1.7 Ga. Overall, zircon from four metabasite xenoliths from the Rankin Inlet sample suite have 未¹⁸O values ranging from + 5.5 to + 8.6鈥? Zircon from three metatonalite/anorthosite xenoliths and five metabasite xenoliths from the Repulse Bay sample suite have 未¹⁸O values of + 5.6 to + 8.3鈥? High 未¹⁸O values (> + 6.0鈥? for the oldest igneous zircon cores (ca. 3.5 Ga and 3.0-2.6 Ga) indicate that their metatonalite/anorthosite protolith magmas were generated from, or had assimilated, supracrustal rocks that interacted previously with surface-derived fluids. Igneous zircon cores (ca. 2.9-2.6 Ga) from one metabasite xenolith have 未¹⁸O values of + 5.6 to + 6.4鈥? which suggests a formation from a mantle-derived basaltic/gabbroic magma. Metamorphic zircon cores (ca. 2.0-1.9 Ga) from one metabasite xenolith commonly have 未¹⁸O values between + 6.0 and + 6.3鈥? which is indicative of a basalt/gabbro protolith and localized reworking of the lower crust caused by regional-scale plate convergence. The wide range of 未¹⁸O values (+ 5.5 to + 8.3鈥? for ca. 1.75-1.70 Ga metamorphic zircon rims (identified in all xenoliths) indicates regional transient heating and reworking of mantle- and supracrustal-derived crust, induced by magmatic underplating along the crust-mantle boundary.