{"id":479239,"date":"2026-10-15T05:52:14","date_gmt":"2026-10-15T12:52:14","guid":{"rendered":"https:\/\/climatescience.press\/?p=479239"},"modified":"2026-10-15T05:52:16","modified_gmt":"2026-10-15T12:52:16","slug":"earths-mantle-was-breathing-oxygen-billion-years-before-the-atmosphere","status":"publish","type":"post","link":"https:\/\/climatescience.press\/?p=479239","title":{"rendered":"Earth\u2019s Mantle Was \u201cBreathing\u201d Oxygen Billion Years Before the Atmosphere"},"content":{"rendered":"\n<figure class=\"wp-block-image size-large\"><img data-recalc-dims=\"1\" loading=\"lazy\" decoding=\"async\" width=\"723\" height=\"485\" data-attachment-id=\"479277\" data-permalink=\"https:\/\/climatescience.press\/?attachment_id=479277\" data-orig-file=\"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/0-Earths-Mantle-Was-Breathing-Oxygen-Billion-Years-Before-the-Atmosphere.jpg?fit=1168%2C784&amp;ssl=1\" data-orig-size=\"1168,784\" data-comments-opened=\"1\" data-image-meta=\"{&quot;credit&quot;:&quot;2b1cc96d-27cc-4727-a5bd-4dd746493e46&quot;,&quot;caption&quot;:&quot;Signature: 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&quot;}\" data-image-title=\"0 Earth\u2019s Mantle Was \u201cBreathing\u201d Oxygen Billion Years Before the Atmosphere\" data-image-description=\"\" data-image-caption=\"&lt;p&gt;Signature: 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&lt;\/p&gt;\n\" data-large-file=\"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/0-Earths-Mantle-Was-Breathing-Oxygen-Billion-Years-Before-the-Atmosphere.jpg?fit=723%2C485&amp;ssl=1\" src=\"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/0-Earths-Mantle-Was-Breathing-Oxygen-Billion-Years-Before-the-Atmosphere.jpg?resize=723%2C485&#038;ssl=1\" alt=\"A surreal landscape featuring a glowing pool of lava surrounded by dark volcanic rock, with shimmering blue streams of energy and crystalline formations emerging from the ground.\" class=\"wp-image-479277\" srcset=\"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/0-Earths-Mantle-Was-Breathing-Oxygen-Billion-Years-Before-the-Atmosphere.jpg?resize=1024%2C687&amp;ssl=1 1024w, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/0-Earths-Mantle-Was-Breathing-Oxygen-Billion-Years-Before-the-Atmosphere.jpg?resize=300%2C201&amp;ssl=1 300w, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/0-Earths-Mantle-Was-Breathing-Oxygen-Billion-Years-Before-the-Atmosphere.jpg?resize=768%2C516&amp;ssl=1 768w, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/0-Earths-Mantle-Was-Breathing-Oxygen-Billion-Years-Before-the-Atmosphere.jpg?resize=640%2C430&amp;ssl=1 640w, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/0-Earths-Mantle-Was-Breathing-Oxygen-Billion-Years-Before-the-Atmosphere.jpg?w=1168&amp;ssl=1 1168w\" sizes=\"auto, (max-width: 723px) 100vw, 723px\" \/><figcaption class=\"wp-element-caption\">AI generated by Grok<\/figcaption><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Scientists found evidence that Earth\u2019s mantle was interacting with (and being oxidized by) surface oxygen as early as ~3.4 billion years ago, roughly a billion years before the Great Oxidation Event permanently raised atmospheric oxygen levels around 2.3- 2.2 billion years ago.<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This comes from a University of Portsmouth- led international study published in<em> Nature Geoscience<\/em> (DOI: 10.1038\/s41561-026-02119-6; lead author Dr. Hugo Moreira). It builds on earlier 2023 work by the same group linking mantle chemistry changes to the Great Oxidation Event itself.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong>Key methods and findings<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Researchers analyzed tiny \u201ctime capsules\u201d:<\/strong> apatite mineral inclusions sealed inside durable zircon crystals from sanukitoid rocks (a distinctive type of magma linked to early subduction- like processes). Samples spanned more than 3 billion years and came from sites including the Pilbara Craton (Australia; ~3.42 and 2.9 Ga), Karelian and Kaapvaal Cratons (Finland and South Africa; ~2.7 Ga), S\u00e3o Francisco Craton (Brazil; ~2.13 Ga), and Scotland (~425 Ma).<a href=\"https:\/\/scienmag.com\/ancient-zircons-reveal-oxygen-was-quietly-oxidizing-earths-mantle-billions-of-years-ago\/\" target=\"_blank\" rel=\"noopener\">\u2060<\/a><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Zircons <\/strong>were dated precisely (some to exactly <strong>3.4 billion years old<\/strong>) using laser techniques at Portsmouth.<\/li>\n\n\n\n<li><strong>Sulfur oxidation states (S\u2076\u207a, S\u2074\u207a, S\u00b2\u207b)<\/strong> in the protected apatite inclusions were measured via sulfur K-edge micro- <strong>X- ray absorption near- edge structure (XANES) spectroscopy <\/strong>at the <strong>European Synchrotron Radiation Facility (ESRF)<\/strong> in France. These states act as a sensitive proxy for oxygen fugacity (how oxidizing the magma and mantle environment was).<a href=\"https:\/\/www.port.ac.uk\/news-events-and-blogs\/news\/earth-was-breathing-oxygen-billions-of-years-before-it-hit-the-atmosphere\" target=\"_blank\" rel=\"noopener\">\u2060<\/a><\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Results show a progressive increase in oxygen fugacity in the sub-arc mantle starting between ~3.4 and 3 billion years ago. The signature remained present across the studied interval and approached <strong>modern levels by ~2.1 billion years ago<\/strong>. This indicates that subduction was already recycling oxidized surface material (from early weathering and intermittent <strong>\u201cwhiffs\u201d<\/strong> <strong>of oxygen<\/strong>) deep into the mantle long before permanent atmospheric oxygenation.<a href=\"https:\/\/www.port.ac.uk\/news-events-and-blogs\/news\/earth-was-breathing-oxygen-billions-of-years-before-it-hit-the-atmosphere\" target=\"_blank\" rel=\"noopener\">\u2060<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The team ruled out alternative explanations (temperature and pressure variations, fractional crystallization, degassing) and noted that even small amounts of oxidized sulfur would have had a strong effect on the more reduced early mantle. <\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>They propose feedback:<\/strong> early oxidative recycling raised sub-arc mantle oxidation \u2192 more oxidizing volcanic gases \u2192 more felsic crust and intensified surface weathering \u2192 further contribution to long- term atmospheric oxygen buildup.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This provides the most continuous timeline yet of how surface oxygen and deep- Earth processes co-evolved. It supports the idea that plate tectonics (or early analogs) connected Earth\u2019s exterior and interior reservoirs far earlier than often assumed, helping create conditions for a habitable planet. <\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The work is curiosity- driven basic research into Earth\u2019s origins and the emergence of life, rather than an immediate practical application.<a href=\"https:\/\/www.port.ac.uk\/news-events-and-blogs\/news\/earth-was-breathing-oxygen-billions-of-years-before-it-hit-the-atmosphere\" target=\"_blank\" rel=\"noopener\">\u2060<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In short, the mantle was effectively <strong>\u201cbreathing\u201d<\/strong> (exchanging and responding to) oxygen via recycling processes a billion years before free oxygen dominated the atmosphere.<\/p>\n\n\n\n<figure class=\"wp-block-embed is-type-video is-provider-youtube wp-block-embed-youtube wp-embed-aspect-16-9 wp-has-aspect-ratio\"><div class=\"wp-block-embed__wrapper\">\n<span class=\"embed-youtube\" style=\"text-align:center; display: block;\"><iframe loading=\"lazy\" class=\"youtube-player\" width=\"723\" height=\"407\" src=\"https:\/\/www.youtube.com\/embed\/v_XkqfBCjb0?version=3&#038;rel=1&#038;showsearch=0&#038;showinfo=1&#038;iv_load_policy=1&#038;fs=1&#038;hl=en-US&#038;autohide=2&#038;wmode=transparent\" allowfullscreen=\"true\" style=\"border:0;\" sandbox=\"allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox\"><\/iframe><\/span>\n<\/div><figcaption class=\"wp-element-caption\"><br><strong>Earth&#8217;s First &#8216;Breath&#8217;<\/strong><\/figcaption><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong><em>Sanukitoid petrogenesis<\/em> refers to the origin and formation processes of a distinctive suite of intermediate to felsic igneous rocks (mainly diorites, monzodiorites, granodiorites, and related rocks) that are characteristic of the late Archean to early Paleoproterozoic (~3.0- 2.5 Ga, with some earlier examples from ~3.4- 2.9 Ga).<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">They mark a transitional phase in Earth\u2019s crustal evolution, bridging the dominant Archean tonalite- trondhjemite- granodiorite (TTG) magmatism and more modern- style calc- alkaline arc magmatism.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong>Geochemical Characteristics<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Sanukitoids are defined by a dual \u201cmantle and crust\u201d signature:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Mantle- compatible elements:<\/strong> High MgO (typically 1.5\u20139 wt%), Mg# (molecular Mg\/ (Mg and Fe) \u2248 45\u201365 or higher in primitive members), Ni (&gt;100 ppm in many definitions), Cr (&gt;100- 200 ppm).<\/li>\n\n\n\n<li><strong>Incompatible elements:<\/strong> Strong enrichment in <strong>large- ion lithophile elements (LILE)<\/strong>, especially K\u2082O (1.5\u20135 wt%), Ba, and Sr (Ba and Sr often &gt;1,000\u20131,400 ppm); high light rare- earth elements (LREE); relatively high K\u2082O\/Na\u2082O compared with TTGs; fractionated REE patterns with low HREE and no or minor Eu anomalies.<a href=\"https:\/\/www.sciencedirect.com\/science\/article\/abs\/pii\/S0024493709004575\" target=\"_blank\" rel=\"noopener\">\u2060<\/a><\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Classic strict definition (Stern et al., 1989) focused on SiO\u2082 55\u2013- 60 wt% with the above traits, but the broader <strong>\u201csanukitoid suite and series\u201d<\/strong> includes more evolved members produced by fractional crystallization. High- Ti and low- Ti varieties are sometimes distinguished.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">They resemble high- Mg andesites (sanukites) from the Setouchi volcanic belt in Japan, hence the name.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong>Petrogenetic Models<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">The consensus is that sanukitoids form by interaction between mantle peridotite and a recycled crustal component (typically TTG- like or slab- derived felsic melts, possibly with fluids and\/or sediments). <\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Two main (not mutually exclusive) pathways are debated:<\/strong><\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Two- stage (metasomatism and later melting) process (most widely invoked)<\/strong>\n<ul class=\"wp-block-list\">\n<li><strong>Stage 1:<\/strong> Subduction- related fluids and or silicate melts (from partial melting of subducted oceanic crust and metabasite, often eclogite- facies, \u00b1 sediments) metasomatize the mantle wedge or subcontinental lithospheric mantle. This creates enriched domains (e.g., amphibole- or phlogopite- bearing veins).<\/li>\n\n\n\n<li><strong>Stage 2:<\/strong> Later thermal perturbation (slab break-off, mantle plume, or continued subduction heating) causes partial melting of this metasomatized peridotite, generating the sanukitoid parental magma.<a href=\"https:\/\/www.researchgate.net\/publication\/245540483_The_sanukitoid_series_Magmatism_at_the_Archaean-Proterozoic_transition\" target=\"_blank\" rel=\"noopener\">\u2060<\/a><\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>One- stage (assimilation and reaction) process<\/strong>\n<ul class=\"wp-block-list\">\n<li>TTG- like or hydrous eclogite melts directly react with and assimilate mantle peridotite during ascent, producing hybrid melts with the characteristic dual geochemistry.<a href=\"https:\/\/orca.cardiff.ac.uk\/id\/eprint\/178323\/1\/2025spencerlphd.pdf\" target=\"_blank\" rel=\"noopener\">\u2060<\/a><\/li>\n<\/ul>\n<\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">Recent Ti- isotope studies (\u03b4\u2074\u2079Ti) of primitive sanukitoids show elevated values requiring a hydrous metabasite (eclogite) melt component formed in equilibrium with residual rutile. This favors fluid- fluxed melting of eclogite in a subduction- like setting and indicates parental magmas were water- rich and relatively oxidized, comparable to modern arc magmas.<a href=\"https:\/\/www.sciencedirect.com\/science\/article\/pii\/S0012821X24004990\" target=\"_blank\" rel=\"noopener\">\u2060<\/a><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Melting conditions are typically high- pressure (&gt;1- 2.5 GPa, corresponding to ~35- 80 and km depth), hydrous, and oxidized. Differentiation often involves amphibole \u00b1 plagioclase \u00b1 orthopyroxene fractionation, sometimes at lower pressures where a distinct cotectic may control the series.<\/p>\n\n\n\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong>Geodynamic Significance<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Sanukitoids appear mainly near the Archean- Proterozoic transition and are linked to the progressive cooling of Earth and the evolution of subduction:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Early Archean:<\/strong> High heat production favored extensive slab melting \u2192 pure TTG magmas with limited mantle interaction.<\/li>\n\n\n\n<li><strong>Late Archean:<\/strong> Reduced slab melting \u2192 more interaction with the mantle wedge \u2192 sanukitoids (hybrids).<\/li>\n\n\n\n<li><strong>Post ~2.5 Ga: <\/strong>Predominantly fluid- fluxed melting of the mantle wedge (modern- style arcs), with slab melts rarer.<a href=\"https:\/\/www.cambridge.org\/core\/journals\/earth-and-environmental-science-transactions-of-royal-society-of-edinburgh\/article\/sanukitoid-series-magmatism-at-the-archaeanproterozoic-transition\/455EDAA942E6614C47A637ACC150D071\" target=\"_blank\" rel=\"noopener\">\u2060<\/a><\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">They are therefore key evidence for the onset or maturation of plate- tectonic (or proto- subduction) processes, deep crust- mantle recycling, and the changing nature of continental crust growth. <\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In the context of the recent <em>Nature Geoscience<\/em> study on mantle oxidation, sanukitoids serve as excellent monitors of <strong>sub- arc mantle redox state<\/strong> because their sources record metasomatism by recycled surface materials.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Modern Analogues and Distribution<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Phanerozoic high- Mg diorites, vaugnerites, appinites, and some post-collisional I- type granitoids share similarities and may represent analogues. Archean examples occur worldwide (e.g., Superior Province, Pilbara, Kaapvaal, Karelian, North China, Amazonian\/Caraj\u00e1s, Yilgarn, and S\u00e3o Francisco cratons).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In summary, sanukitoid petrogenesis records hybridization between depleted mantle and recycled crustal melts and fluids in a subduction- related setting under hotter Archean conditions. <\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This dual signature makes them invaluable for tracking early Earth geodynamics, mantle metasomatism, and the co- evolution of crust and mantle.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img data-recalc-dims=\"1\" loading=\"lazy\" decoding=\"async\" width=\"723\" height=\"407\" data-attachment-id=\"479260\" data-permalink=\"https:\/\/climatescience.press\/?attachment_id=479260\" data-orig-file=\"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/image-95.png?fit=1024%2C576&amp;ssl=1\" data-orig-size=\"1024,576\" data-comments-opened=\"1\" data-image-title=\"image\" data-image-description=\"\" data-image-caption=\"\" data-large-file=\"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/image-95.png?fit=723%2C407&amp;ssl=1\" src=\"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/image-95.png?resize=723%2C407&#038;ssl=1\" alt=\"Close-up of an orange mineral rock on a textured surface with small pebbles and dust.\" class=\"wp-image-479260\" srcset=\"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/image-95.png?w=1024&amp;ssl=1 1024w, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/image-95.png?resize=300%2C169&amp;ssl=1 300w, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/image-95.png?resize=768%2C432&amp;ssl=1 768w, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/image-95.png?resize=640%2C360&amp;ssl=1 640w\" sizes=\"auto, (max-width: 723px) 100vw, 723px\" \/><figcaption class=\"wp-element-caption\"><a href=\"https:\/\/scienmag.com\/ancient-zircons-reveal-oxygen-was-quietly-oxidizing-earths-mantle-billions-of-years-ago\/\">Ancient Zircons Reveal Oxygen Was Quietly Oxidizing Earth&#8217;s Mantle<\/a><\/figcaption><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"has-large-font-size wp-block-paragraph\"><strong>Progressive oxidative weathering raised sub-arc mantle fugacity on the Archaean Earth<\/strong><\/p>\n\n\n\n<h3 class=\"wp-block-heading has-medium-font-size\"><strong>Abstract (summary)<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">In the modern Earth, sub- arc mantle oxygen fugacity is linked to addition of sulfur species by slab fluids. It has been unclear to what extent volatile recycling controlled redox changes in the early Earth.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Using sulfur K -edge micro- X- ray absorption near- edge structure (\u03bc-XANES) spectroscopy, the authors measured the relative abundances of S\u2076\u207a, S\u2074\u207a, and S\u00b2\u207b in apatite inclusions hosted in geochemically characterized and precisely dated zircons from sub- arc sanukitoid magmas spanning 3.4 billion years of Earth history.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Key results:<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The <strong>sub- arc mantle <\/strong>shows a marked increase in <strong>oxygen fugacity (fO\u2082) <\/strong>between 3.4 and 3.0 Ga.<\/li>\n\n\n\n<li>It is substantially more oxidized than the unaltered ambient upper mantle.<\/li>\n\n\n\n<li>This cannot be explained by fractional crystallization, degassing, or intrinsic mantle processes.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">The authors propose that progressive oxidative weathering increased the proportion of oxidized sulfur recycled into mantle- wedge sources. <\/p>\n\n\n\n<p class=\"wp-block-paragraph\">This established a feedback between subduction of surface materials and progressively more oxidized arc magmatism. <\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Early subduction involving inorganic oxidation and intermittent <strong>\u201cwhiffs\u201d<\/strong> of oxygen between 3.4 and 2.7 Ga may have driven an early rise in sub-arc mantle fugacity <strong><em>before<\/em> the Great Oxidation Event<\/strong> (GOE, ~2.3-2.2 Ga), reaching conditions comparable to the modern Earth by ~2.1 Ga.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Methods highlights<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Samples:<\/strong> Geochemically coherent sanukitoids (metasomatized- mantle- derived magmas) from the Pilbara Craton (Australia; 3.42 and 2.9 Ga), Karelian Craton (Finland; 2.7 Ga), Kaapvaal Craton (South Africa; 2.7 Ga), S\u00e3o Francisco Craton (Brazil; 2.13 Ga), and Northern Highland Terrane (Scotland; 0.425 Ga).<\/li>\n\n\n\n<li>Protected apatite inclusions inside zircon crystals acted as unaltered <strong>\u201ctime capsules\u201d<\/strong>.<\/li>\n\n\n\n<li>337 analyses on 39 apatite inclusions + 213 analyses on 65 matrix apatites, performed at the European Synchrotron Radiation Facility (ESRF, ID21 beamline).<\/li>\n\n\n\n<li>S\u2076\u207a\/S_total ratios converted to \u0394FMQ (deviation from the fayalite- magnetite- quartz buffer) using an experimental oxybarometer.<\/li>\n\n\n\n<li>Supporting<strong> U- Pb dating<\/strong>, trace- element, and oxygen- isotope data on the host zircons.<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Broader implication<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">This provides the first continuous record showing that surface oxidative weathering products were already being recycled into the deep Earth via early subduction- like processes more than a billion years before permanent atmospheric oxygenation. The mantle was not a passive spectator; it participated in a feedback loop that helped shape the conditions leading to a habitable, <strong>oxygenated Earth<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Scientists found evidence that Earth\u2019s mantle was interacting with (and being oxidized by) surface oxygen as early as ~3.4 billion years ago, roughly a billion years before the Great Oxidation Event permanently raised atmospheric oxygen levels around 2.3- 2.2 billion years ago.<\/p>\n<p>Sanukitoid petrogenesis refers to the origin and formation processes of a distinctive suite of intermediate to felsic igneous rocks (mainly diorites, monzodiorites, granodiorites, and related rocks) that are characteristic of the late Archean to early Paleoproterozoic (~3.0- 2.5 Ga, with some earlier examples from ~3.4- 2.9 Ga).<\/p>\n<p>Early subduction involving inorganic oxidation and intermittent \u201cwhiffs\u201d of oxygen between 3.4 and 2.7 Ga may have driven an early rise in sub-arc mantle fugacity before the Great Oxidation Event (GOE, ~2.3-2.2 Ga), reaching conditions comparable to the modern Earth by ~2.1 Ga.<\/p>\n","protected":false},"author":121246920,"featured_media":479277,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_coblocks_attr":"","_coblocks_dimensions":"","_coblocks_responsive_height":"","_coblocks_accordion_ie_support":"","advanced_seo_description":"Discover how Earth's mantle was oxidized by surface oxygen 3.4 billion years ago, long before atmospheric changes impacted life.","jetpack_seo_html_title":"Earth's Mantle: Breathing Oxygen Billions of Years Ago","jetpack_seo_noindex":false,"jetpack_seo_schema_type":"","_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_wpcom_ai_launchpad_first_post":false,"_jetpack_hide_featured_image":false,"_jetpack_featured_image_duplicate_dismissed":0,"_jetpack_feature_clip_id":0,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"jetpack_post_was_ever_published":false},"categories":[1],"tags":[691840525,691846399,691846398,691846389,691845641,691846394,691846397,691846393,691846390,691846392,691846396,691846391,691846400,691846388,691846395],"class_list":["post-479239","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uncategorized","tag-atmospheric-chemistry","tag-time-capsules","tag-before-the-great-oxidation-event","tag-european-synchrotron-radiation-facility-esrf","tag-geochemistry","tag--xanes","tag-oxygen-fugacity-fo","tag-precambrian-geology","tag-sanukitoid-petrogenesis","tag-sub-arc-mantle-redox-state","tag-sub-arc-sanukitoid-magmas","tag-tonalite-trondhjemite-granodiorite-ttg-2","tag-u-pb-dating","tag-x-ray-absorption-near-edge-structure-xanes-spectroscopy","tag-zircons","fallback-thumbnail"],"jetpack_publicize_connections":[],"jetpack_likes_enabled":true,"jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/paxLW1-20FF","jetpack-related-posts":[{"id":447081,"url":"https:\/\/climatescience.press\/?p=447081","url_meta":{"origin":479239,"position":0},"title":"Subduction on a Cooling Planet Drove the Stepwise Rise of Atmospheric Oxygen","author":"uwe.roland.gross","date":"05\/28\/2026","format":false,"excerpt":"Supercontinent cycles\u2014 the periodic assembly and breakup of Earth's major landmasses\u2014have been linked to oxygenation events through tectonic, erosional, volcanic, and biogeochemical feedback.","rel":"","context":"In \"biogeochemical model (COPSE)\"","block_context":{"text":"biogeochemical model (COPSE)","link":"https:\/\/climatescience.press\/?tag=biogeochemical-model-copse"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/05\/0-Subduction-on-a-Cooling-Planet-Drove-the-Stepwise-Rise-of-Atmospheric-Oxygen.jpg?fit=1168%2C784&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/05\/0-Subduction-on-a-Cooling-Planet-Drove-the-Stepwise-Rise-of-Atmospheric-Oxygen.jpg?fit=1168%2C784&ssl=1&resize=350%2C200 1x, 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just pristine melts straight from the mantle. They incorporated a lot of \"sun- baked ocean leftovers\"\u2014recycled oceanic crust and sediments that had been altered at the surface by seawater and the ancient atmosphere.","rel":"","context":"In \"Earth's rock cycle\"","block_context":{"text":"Earth's rock cycle","link":"https:\/\/climatescience.press\/?tag=earths-rock-cycle"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/05\/0-Earth-Was-Recycling-Billions-of-Years-Before-It-Was-Cool-Evidence-from-Ancient-Continents.jpg?fit=1168%2C784&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/05\/0-Earth-Was-Recycling-Billions-of-Years-Before-It-Was-Cool-Evidence-from-Ancient-Continents.jpg?fit=1168%2C784&ssl=1&resize=350%2C200 1x, 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that a vast \u201cGreat Escarpment of Laurentia\u201d\u2014a kilometre-high cliff system stretching thousands of kilometres across ancient North America\u2014helps explain the Grand Canyon\u2019s Great Unconformity (the famous gap of more than a billion years in the rock record).","rel":"","context":"In \"\u201cGreat Escarpment of Laurentia\u201d\"","block_context":{"text":"\u201cGreat Escarpment of Laurentia\u201d","link":"https:\/\/climatescience.press\/?tag=great-escarpment-of-laurentia"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/08\/0-Ancient-Mega-Cliff-Across-North-America-May-Explain-Grand-Canyons-Missing-Billion-Years.jpg?fit=1168%2C784&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/08\/0-Ancient-Mega-Cliff-Across-North-America-May-Explain-Grand-Canyons-Missing-Billion-Years.jpg?fit=1168%2C784&ssl=1&resize=350%2C200 1x, 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Antarctica developed a major ice sheet ~34 million years ago, while Earth was still ~5\u00b0C warmer than today and why the Arctic lagged by tens of millions of years.","rel":"","context":"In \"Continental breakup\"","block_context":{"text":"Continental breakup","link":"https:\/\/climatescience.press\/?tag=continental-breakup"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/08\/0-Ancient-Mantle-Waves-Lifted-Antarcticas-Mountains%E2%80%94and-Helped-Freeze-the-Continent.jpg?fit=1168%2C784&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/08\/0-Ancient-Mantle-Waves-Lifted-Antarcticas-Mountains%E2%80%94and-Helped-Freeze-the-Continent.jpg?fit=1168%2C784&ssl=1&resize=350%2C200 1x, 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beneath the Pacific Triangle, the Pacific Ocean\u2019s oldest preserved oceanic crust (about 160\u2013180 million years old). The oldest large- scale oceanic crust still preserved on the seafloor is in the western Pacific Ocean, specifically in the region known as the Pacific\u2026","rel":"","context":"In \"\u201cfossilized\u201d traces\"","block_context":{"text":"\u201cfossilized\u201d traces","link":"https:\/\/climatescience.press\/?tag=fossilized-traces"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/0-Ancient-Mantle-Flow-Fossilized-Beneath-Earths-Oldest-Ocean-Floor.jpg?fit=1168%2C784&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/0-Ancient-Mantle-Flow-Fossilized-Beneath-Earths-Oldest-Ocean-Floor.jpg?fit=1168%2C784&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/0-Ancient-Mantle-Flow-Fossilized-Beneath-Earths-Oldest-Ocean-Floor.jpg?fit=1168%2C784&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/0-Ancient-Mantle-Flow-Fossilized-Beneath-Earths-Oldest-Ocean-Floor.jpg?fit=1168%2C784&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/0-Ancient-Mantle-Flow-Fossilized-Beneath-Earths-Oldest-Ocean-Floor.jpg?fit=1168%2C784&ssl=1&resize=1050%2C600 3x"},"classes":[]},{"id":443773,"url":"https:\/\/climatescience.press\/?p=443773","url_meta":{"origin":479239,"position":5},"title":"Mantle Helium Reveals a New Tectonic Rift Awakening in Southern Africa","author":"uwe.roland.gross","date":"05\/12\/2026","format":false,"excerpt":"The East African Rift System (EARS or EAR) is one of the most significant active continental rift zones on Earth. It represents a divergent tectonic plate boundary where the African Plate is slowly splitting into the Nubian Plate (west) and the Somali Plate (east), with additional microplates involved (e.g., Victoria,\u2026","rel":"","context":"In \"22\u201325 million years ago (Miocene)\"","block_context":{"text":"22\u201325 million years ago (Miocene)","link":"https:\/\/climatescience.press\/?tag=22-25-million-years-ago-miocene"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/05\/0-Mantle-Helium-Reveals-a-New-Tectonic-Rift-Awakening-in-Southern-Africa.jpg?fit=1168%2C784&ssl=1&resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/05\/0-Mantle-Helium-Reveals-a-New-Tectonic-Rift-Awakening-in-Southern-Africa.jpg?fit=1168%2C784&ssl=1&resize=350%2C200 1x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/05\/0-Mantle-Helium-Reveals-a-New-Tectonic-Rift-Awakening-in-Southern-Africa.jpg?fit=1168%2C784&ssl=1&resize=525%2C300 1.5x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/05\/0-Mantle-Helium-Reveals-a-New-Tectonic-Rift-Awakening-in-Southern-Africa.jpg?fit=1168%2C784&ssl=1&resize=700%2C400 2x, https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/05\/0-Mantle-Helium-Reveals-a-New-Tectonic-Rift-Awakening-in-Southern-Africa.jpg?fit=1168%2C784&ssl=1&resize=1050%2C600 3x"},"classes":[]}],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/climatescience.press\/wp-content\/uploads\/2026\/10\/0-Earths-Mantle-Was-Breathing-Oxygen-Billion-Years-Before-the-Atmosphere.jpg?fit=1168%2C784&ssl=1","_links":{"self":[{"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/posts\/479239","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/users\/121246920"}],"replies":[{"embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=479239"}],"version-history":[{"count":44,"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/posts\/479239\/revisions"}],"predecessor-version":[{"id":479285,"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/posts\/479239\/revisions\/479285"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=\/wp\/v2\/media\/479277"}],"wp:attachment":[{"href":"https:\/\/climatescience.press\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=479239"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=479239"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/climatescience.press\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=479239"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}