The generation and evolution of the continental crust

Abstract

The continental crust is the archive of the geological history of the Earth. Only 7% of the crust is older than 2.5 Ga, and yet significantly more crust was generated before 2.5 Ga than subsequently. Zircons offer robust records of the magmatic and crust-forming events preserved in the continental crust. They yield marked peaks of ages of crystallization and of crust formation. The latter might reflect periods of high rates of crust generation, and as such be due to magmatism associated with deep-seated mantle plumes. Alternatively the peaks are artefacts of preservation, they mark the times of supercontinent formation, and magmas generated in some tectonic settings may be preferentially preserved. There is increasing evidence that depletion of the upper mantle was in response to early planetary differentiation events. Arguments in favour of large volumes of continental crust before the end of the Archaean, and the thickness of felsic and mafic crust, therefore rely on thermal models for the progressively cooling Earth. They are consistent with recent estimates that the rates of crust generation and destruction along modern subduction zones are strikingly similar. The implication is that the present volume of continental crust was established 2–3 Ga ago.

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

“…Previous research has indicated that zircons with δ 18 O values of b6.5‰ may not form from supracrustal melts, whereas zircons with δ 18 O values of N 6.5‰ are indicative of the significant involvement of supracrustal materials (e.g., Cavosie et al, 2005;Davidson et al, 2005;Valley et al, 2005;Hawkesworth and Kemp, 2006;Kemp et al, 2006;Fu et al, 2009;Hawkesworth et al, 2010;Lu et al, 2013). Although some of the PDL zircon δ 18 O values obtained in this study are higher than 6.5‰ (n = 28 of 159, Appendix C; Fig.…”

Iron formations: A global record of Neoarchaean to Palaeoproterozoic environmental history

“…It has been recognised for some time that the volume of continental crust was substantial in the early Archaean (see review by Hawkesworth et al, 2010), but to date it has been unclear how continental freeboard controlled the amount of emergent continental landmasses. Continental freeboard depends more on mantle temperature, crustal composition, and continental hypsometry (also temperature-dependent) than on the growth of continental crust.…”

Archean komatiite volcanism controlled by the evolution of early continents

“…The term "juvenile" refers to crustal material that plots on or close to the depleted mantle evolution line, suggesting derivation from a depleted mantle source. In contrast, "reworked" refers to the remobilization of preexisting crust by partial melting and/or erosion and sedimentation (25,26). Complete sample information, methodology, and geochemical datasets (U-Pb, Lu-Hf, and komatiite) are available in the Supporting Information, Figs.…”