The recycling of supracrustal materials,and in particular hydrated rocks,has a profound impact on mantle composition and thus on the formation of continental crust,because water modifies the physical properties of lithological systems and the mechanisms of partial melting and fractional fractionation.On the modern Earth,plate tectonics offers an efficient mechanism for mass transport from the Earth's surface to its interior,but how far this mechanism dates back in the Earth's history is still uncertain.Here,we use zircon oxygen(O)isotopes to track recycling of supracrustal materials into the magma sources of early Archean igneous suites from the Kaapvaal Craton,southern Africa.The mean δ18O values of zircon from TTG(tonalite-trondhjemite-granodiorite)rocks abruptly increase at the Paleo-Mesoarchean boundary(ca.3230 million years ago;Ma),from mantle zircon values of 5‰-6‰ to approaching 7.1‰,and this increase occurs in≤3230 Ma rocks with elevated Dy/Yb ratios.The 18O enrichment is a unique signature of low-temperature water-rock interaction on the Earth's surface.Because the later phase was emplaced into the same crustal level as the older one and TTG magmas would derive from melting processes in the garnet stability field(＞40 km depth),we suggest that this evident shift in TTG zircon O isotopic compositions records the onset of recycling of the mafic oceanic crust that underwent seawater hydrothermal alteration at low temperature.The onset of the enhanced recycling of supracrustal materials may also have developed elsewhere in other Archean cratons and reflects a significant change in the tectonic realm during craton formation and stabilization,which may be important processes for the operation of plate tectonics on early Earth.

Xiaolei Wang;Ming Tang;Jeff Moyen;Di Wang;Alfred Kr?ner;Chris Hawkesworth;Xiaoping Xia;Hangqiang Xie;Carl Anhaeusser;Axel Hofmann;Junyong Li;Linsen Li

State Key Laboratory for Mineral Deposits Research,School of Earth Sciences and Engineering,Nanjing University,Nanjing 210023,China;School of Earth and Space Sciences,Peking University,Beijing 100871,China;Laboratoire Magmas et Volcans UMR6524,Université de Lyon,UJM-UCA-CNRS-IRD,Saint Etienne 42023,France;Institut für Geowissenschaften,Universit?t Mainz,Mainz 55099,Germany;Department of Earth Sciences,University of Bristol,Bristol BS8 1RJ,UK;State Key Laboratory of lsotope Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;SHRIMP Center,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Economic Geology Research Unit,University of the Witwatersrand,Johannesburg 2050,South Africa;Department of Geology,University of Johannesburg,Johannesburg 2006,South Africa

国家科学评论（英文版）

[1]Xiaolei Wang;Ming Tang;Jeff Moyen;Di Wang;Alfred Kr?ner;Chris Hawkesworth;Xiaoping Xia;Hangqiang Xie;Carl Anhaeusser;Axel Hofmann;Junyong Li;Linsen Li-.The onset of deep recycling of supracrustal materials at the Paleo-Mesoarchean boundary)[J].国家科学评论（英文版）,2022(03):106-114

Mesoarchean,Kaapvaal

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