Abstract
AbstractThe strong resilience of the mineral zircon and its ability to host a wealth of isotopic information make it the best deep-time archive of Earth's continental crust. Zircon is found in most felsic igneous rocks, can be precisely dated and can fingerprint magmatic sources; thus, it has been widely used to document the formation and evolution of continental crust, from pluton- to global-scale. Here, we present a review of major contributions that zircon studies have made in terms of understanding key questions involving the formation of the continents. These include the conditions of continent formation on early Earth, the onset of plate tectonics and subduction, the rate of crustal growth through time and the governing balance of continental addition v. continental loss, and the role of preservation bias in the zircon record.Supplementary material:A compilation used in this study of previously published detrital zircon U-Pb-Hf isotope data are available at http://www.geolsoc.org.uk/SUP18791
Highlights
The strong resilience of the mineral zircon and its ability to host a wealth of isotopic information make it the best deep-time archive of Earth’s continental crust
The youngest estimates of modern-day-style plate tectonics are in the Neoproterozoic, and are based on the first existence of lithological associations that we find in the recent past (Stern 2005, 2008; Hamilton 2011), such as ophiolites, blueschists and accretionary melanges
This paper discusses a number of topics that are hotly debated and still contentious, such as the onset of continent formation, plate tectonics and crustal growth rate
Summary
Evolved signatures (see Fig. 5); these were interpreted as evidence for differentiation of the Earth into large volumes of granitic continental crust and a residual depleted mantle (Harrison et al 2005). Zeh et al (2014) noted this marked change, interpreting it as the large-scale formation of new crust after 4.1 Ga, with the prior period featuring internal reworking of crust formed at 4.5 Ga. continued trend of juvenile addition (i.e. zircons with 1Hf near the depleted mantle) that begins around 3.9 Ga (see Figs 1 & 6). Zeh et al (2014) noted this marked change, interpreting it as the large-scale formation of new crust after 4.1 Ga, with the prior period featuring internal reworking of crust formed at 4.5 Ga These authors noted the possibility that this change around the Hadean/ Archaean boundary may reflect the onset of plate tectonics, but are careful to not make any bold claims. Valley et al (2005) compiled a database (n 1⁄4 1200) of all the published zircon d18O data at that time, and noted a broad similarity of mantle-like to moderately elevated
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