Secular change in lifetime of granitic crust and the continental growth: A new view from detrital zircon ages of sandstones

查看全文 作　　者：Hikaru [1]Sawada;Yukio [1]Isozaki;Shuhei [2]Sakata;Takafumi [3]Hirata;Shigenori [4]Maruyama

机构地区：[1]Department of General System Studies,The University of Tokyo;[2]Earth-Life Science Institute(ELSI),Tokyo Institute of Technology;[3]Department of Chemistry,Gakushuin University;[4]Geochemical Research Center,The University of Tokyo

出　　处：《Geoscience Frontiers》索引2018年第9卷第4期,共17页

基　　金：supported by Japan Society of Promotion of Science (JSPS KAKENHI Grants-in-Aid for Scientific Research Grant Nos. 23224012, 26106002, and 26106005) from the Japanese Ministry of Education, Science, Sports, Technology, and Culture 摘　　要：U-Pb ages of detrital zircons were newly dated for 4 Archean sandstones from the Pilbara craton in Australia, Wyoming craton in North America, and Kaapvaal craton in Africa. By using the present results with previously published data, we compiled the age spectra of detrital zircons for 2.9, 2.6, 2.3,1.0, and0.6 Ga sandstones and modern river sands in order to document the secular change in age structure of continental crusts through time. The results demonstrated the following episodes in the history of continental crust:(1) low growth rate of the continents due to the short cycle in production/destruction of granitic crust during the Neoarchean to Paleoproterozoic(2.9-23 Ga),(2) net increase in volume of the continents during Paleo-to Mesoproterozoic(2.3-1.0 Ga), and(3) net decrease in volume of the continents during the Neoproterozoic and Phanerozoic(after 1.0 Ga). In the Archean and Paleoproterozoic, the embryonic continents were smaller than the modern continents, probably owing to the relatively rapid production and destruction of continental crust. This is indeed reflected in the heterogeneous crustal age structure of modern continents that usually have relatively small amount of Archean crusts with respect to the post-Archean ones. During the Mesoproterozoic, plural continents amalgamated into larger ones comparable to modern continental blocks in size. Relatively older crusts were preserved in continental interiors, whereas younger crusts were accreted along continental peripheries.In addition to continental arc magmatism, the direct accretion of intra-oceanic island arc around continental peripheries also became important for net continental growth. Since 1.0 Ga, total volume of continents has decreased, and this appears consistent with on-going phenomena along modern active arc-trench system with dominant tectonic erosion and/or arc subduction. Subduction of a huge amount of granitic crusts into the mantle through time is suggested, and this requires re-consideration of the mantle composition and heterogeneity. 关键词：锆石年龄直接生长花岗石大陆外壳岩屑沙岩太古代

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Secular change in lifetime of granitic crust and the continental growth: A new view from detrital zircon ages of sandstones

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