Creation of a continent recorded in zircon zoning

Abstract

We have discovered a robust microcrystalline record of the early genesis of North American lithosphere preserved in the U-Pb age and oxygen isotope zoning of zircons from a lower crustal paragneiss in the Neoarchean Superior province. Detrital igneous zircon cores with δ 18 O values of 5.1‰-7.1‰ record creation of primitive to increasingly evolved crust from 2.85 ± 0.02 Ga to 2.67 ± 0.02 Ga. Sharp chemical unconformity between cores and higher δ 18 O (8.4‰-10.4‰) metamorphic overgrowths as old as 2.66 ± 0.01 Ga dictates a rapid sequence of arc unroofi ng, burial of detrital zircons in hydrosphere-altered sediment, and transport to lower crust late in upper plate assembly. The period to 2.58 ± 0.01 Ga included ~80 m.y. of high-temperature (~700-650 °C), nearly continuous overgrowth events refl ecting stages in maturation of the subjacent mantle root. Huronian continental rifting is recorded by the youngest zircon tip growth at 2512 ± 8 Ma (~ 600 °C) signaling magma intraplating and the onset of rigid plate behavior. This >150 m.y. microscopic isotope record in single crystals demonstrates the sluggish volume diffusion of U, Pb, and O in zircon throughout protracted regional metamorphism, and the consequent advances now possible in reconstructing planetary dynamics with zircon zoning.

Age and isotopic geochemical characteristics of Archean carbonatites and alkaline rocks of the Baltic shield

“…The age of intrusion is constrained by the time span of 2.68-2.62 Ga, while granulite facies metamorphism occurred between 2.66 and 2.64 Ga [Percival, Krogh, 1983;Krogh, 1993;Ashwal, Myers, 1994]. It is noteworthy that metamorphism of the low-crustal rocks took place soon after formation of the granite-greenstone association at the upper crustal level (2.73-2.67 Ga) [Corfu, 1987;Corfu, Ayres, 1991;Davis, 2002;Moser et al, 2008]. Sedimentary rocks dated at 2.48 Ga unconformably overlie Superior Province granites, indicating that erosion developed prior to ~2.5 Ga.…”

Zircon Alteration in Wall Rock of Pamour and Hoyle Pond Au Deposits, Abitibi Greenstone Belt: Constraints on Timescales of Fluid Flow from Depth-Profiling Techniques

“…Deep crustal metamorphism in the Superior province occurred during orogen parallel mid-to lower crustal ductile flow from 2660 to 2630 Ma, which closely followed Kenoran polyphase shortening and folding of all crustal levels (Moser et al, 2008). Similarly, upper crustal greenschist facies metamorphism of Abitibi rocks occurred between 2677 and 2643 Ma, culminating at 2660 Ma, which is coeval with midcrustal granulitization exposed in the Kapuskasing structural zone to the west (Powell et al, 1995a;Moser et al, 2008).…”

“…Similarly, upper crustal greenschist facies metamorphism of Abitibi rocks occurred between 2677 and 2643 Ma, culminating at 2660 Ma, which is coeval with midcrustal granulitization exposed in the Kapuskasing structural zone to the west (Powell et al, 1995a;Moser et al, 2008). Many Abitibi metamorphic textures and fabrics record the final tectonic strain field of the evolving orogen, and the geometry and nature of the isograds indicate that metamorphism was synchronous with and/or slightly postdated late deformation (Powell et al, 1995a).…”

Oxygen isotope and trace element geochemistry of zircons from porphyry copper system: Implications for Late Triassic metallogenesis within the Yidun Terrane, southeastern Tibetan Plateau

“…Instead, the oxygen isotope and trace element (TE) compositions of non-metamict magmatic zircon are likely to be preserved, meaning that these minerals can provide crucial information on magma genesis and compositional characteristics of the magma during zircon crystallization (e.g., Peck et al, 2001;Wilde et al, 2001;Zheng et al, 2004Zheng et al, , 2007Belousova et al, 2006;Scherer et al, 2007;Moser et al, 2008), primarily as a result of the refractory nature of zircon and the extremely low diffusivity of oxygen within zircons in most crustal environments (e.g., Valley et al, 1994;Cherniak et al, 1997aCherniak et al, , 1997bCherniak and Watson, 2003;Peck et al, 2003;Valley, 2003;Page et al, 2007;Bowman et al, 2011;Bindeman et al, 2013;Bindeman et al, 2014). This study is the first to use zircon chemistry to examine the petrogenesis of Late Triassic magmas within the Yidun Terrane and explore the ore-forming potential of this magmatic event.…”