LINK<\/strong><\/a><\/p>\n\n\n\n“Earth is the only planet known to have continents, although how they formed and evolved is unclear. Here using the oxygen isotope compositions of dated magmatic zircon, we show that the Pilbara Craton in Western Australia, Earth\u2019s best-preserved Archaean (4.0\u20132.5 billion years ago (Ga)) continental remnant, was built in three stages. Stage 1 zircons (3.6\u20133.4\u2009Ga) form two age clusters with one-third recording submantle \u03b418O, indicating crystallization from evolved magmas derived from hydrothermally altered basaltic crust like that in modern-day Iceland1,2. Shallow melting is consistent with giant impacts that typified the first billion years of Earth history3,4,5. Giant impacts provide a mechanism for fracturing the crust and establishing prolonged hydrothermal alteration by interaction with the globally extensive ocean6,7,8. A giant impact at around 3.6\u2009Ga, coeval with the oldest low-\u03b418O zircon, would have triggered massive mantle melting to produce a thick mafic\u2013ultramafic nucleus9,10. A second low-\u03b418O zircon cluster at around 3.4\u2009Ga is contemporaneous with spherule beds that provide the oldest material evidence for giant impacts on Earth11. Stage 2 (3.4\u20133.0\u2009Ga) zircons mostly have mantle-like \u03b418O and crystallized from parental magmas formed near the base of the evolving continental nucleus12. Stage 3 (<3.0\u2009Ga) zircons have above-mantle \u03b418O, indicating efficient recycling of supracrustal rocks. That the oldest felsic rocks formed at 3.9\u20133.5\u2009Ga (ref. 13), towards the end of the so-called late heavy bombardment4, is not a coincidence.”<\/p>\n","protected":false},"excerpt":{"rendered":"
Tim E. Johnson, Christopher L. Kirkland, Yongjun Lu, R. Hugh Smithies, Michael Brown & Michael I. H. Hartnady Nature, Volume 608, pages 330\u2013335 (2022)Published: 10 August 2022 LINK “Earth is the only planet known to…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[112,90],"tags":[80,313,1866,2836,184,5728],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/31119"}],"collection":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=31119"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/31119\/revisions"}],"predecessor-version":[{"id":31120,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/31119\/revisions\/31120"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=31119"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=31119"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=31119"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}