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window.loswp.willEdgeCache = false; window.loswp.work = {"work":{"id":12356417,"created_at":"2015-05-12T12:53:55.241-07:00","from_world_paper_id":136311760,"updated_at":"2024-11-17T22:41:27.222-08:00","_data":{"grobid_abstract":"Lower ocean crust is primarily gabbroic, although 1-2% felsic igneous rocks that are referred to collectively as plagiogranites occur locally. Recent experimental evidence suggests that plagiogranite magmas can form by hydrous partial melting of gabbro triggered by seawater-derived fluids, and thus they may indicate early, high-temperature hydrothermal fluid circulation. To explore seawater-rock interaction prior to and during the genesis of plagiogranite and other late-stage magmas, oxygen-isotope ratios preserved in igneous zircon have been measured by ion microprobe. A total of 197 zircons from 43 plagiogranite, evolved gabbro, and hydrothermally altered fault rock samples have been analyzed. Samples originate primarily from drill core acquired during Ocean Drilling Program and Integrated Ocean Drilling Program operations near the Mid-Atlantic and Southwest Indian Ridges. With the exception of rare, distinctively luminescent rims, all zircons from ocean crust record remarkably uniform d 18 O with an average value of 5.2 ± 0.5% (2SD). The average d 18 O(Zrc) would be in magmatic equilibrium with unaltered MORB [d 18 O(WR) * 5.6-5.7%], and is consistent with the previously determined value for equilibrium with the mantle. The narrow range of measured d 18 O values is predicted for zircon crystallization from variable parent melt compositions and temperatures in a closed system, and provides no indication of any interactions between altered rocks or seawater and the evolved parent melts. If plagiogranite forms by hydrous partial melting, the uniform mantle-like d 18 O(Zrc) requires melting and zircon crystallization prior to significant amounts of water-rock interactions that alter the protolith d 18 O. Zircons from ocean crust have been proposed as a tectonic analog for [3.9 Ga detrital zircons from the earliest (Hadean) Earth by multiple workers. However, zircons from ocean crust are readily distinguished geochemically from zircons formed in continental crustal environments. Many of the [3.9 Ga zircons have mildly elevated d 18 O (6.0-7.5%), but such values have not been identified in any zircons from the large sample suite examined here. The difference in d 18 O, in combination with newly acquired lithium concentrations and published trace element data, clearly shows that the [3.9 Ga detrital zircons did not originate by processes analogous to those in modern mid-ocean ridge settings.","publication_date":"2011,,","grobid_abstract_attachment_id":"46225699"},"document_type":"paper","pre_hit_view_count_baseline":null,"quality":"high","language":"en","title":"Uniformly mantle-like δ 18 O in zircons from oceanic plagiogranites and gabbros","broadcastable":true,"draft":null,"has_indexable_attachment":true,"indexable":true}}["work"]; window.loswp.workCoauthors = [31054590]; window.loswp.locale = "en"; window.loswp.countryCode = "SG"; window.loswp.cwvAbTestBucket = ""; window.loswp.designVariant = "ds_vanilla"; window.loswp.fullPageMobileSutdModalVariant = "control"; window.loswp.useOptimizedScribd4genScript = false; window.loginModal = {}; window.loginModal.appleClientId = 'edu.academia.applesignon'; window.userInChina = "false";</script><script defer="" src="https://accounts.google.com/gsi/client"></script><div class="ds-loswp-container"><div class="ds-work-card--grid-container"><div class="ds-work-card--container js-loswp-work-card"><div class="ds-work-card--cover"><div class="ds-work-cover--wrapper"><div class="ds-work-cover--container"><button class="ds-work-cover--clickable js-swp-download-button" data-signup-modal="{"location":"swp-splash-paper-cover","attachmentId":46225699,"attachmentType":"pdf"}"><img alt="First page of “Uniformly mantle-like δ 18 O in zircons from oceanic plagiogranites and gabbros”" class="ds-work-cover--cover-thumbnail" src="https://0.academia-photos.com/attachment_thumbnails/46225699/mini_magick20190210-12283-uqekjs.png?1549810170" /><img alt="PDF Icon" class="ds-work-cover--file-icon" src="//a.academia-assets.com/images/single_work_splash/adobe_icon.svg" /><div class="ds-work-cover--hover-container"><span class="material-symbols-outlined" style="font-size: 20px" translate="no">download</span><p>Download Free PDF</p></div><div class="ds-work-cover--ribbon-container">Download Free PDF</div><div class="ds-work-cover--ribbon-triangle"></div></button></div></div></div><div class="ds-work-card--work-information"><h1 class="ds-work-card--work-title">Uniformly mantle-like δ 18 O in zircons from oceanic plagiogranites and gabbros</h1><div class="ds-work-card--work-authors ds-work-card--detail"><a class="ds-work-card--author js-wsj-grid-card-author ds2-5-body-md ds2-5-body-link" data-author-id="31054590" href="https://wisc.academia.edu/JohnValley"><img alt="Profile image of John Valley" class="ds-work-card--author-avatar" src="https://0.academia-photos.com/31054590/9107827/10158297/s65_john.valley.jpg" />John Valley</a></div><div class="ds-work-card--detail"><p class="ds-work-card--detail ds2-5-body-sm">2011</p><div class="ds-work-card--work-metadata"><div class="ds-work-card--work-metadata__stat"><span class="material-symbols-outlined" style="font-size: 20px" translate="no">visibility</span><p class="ds2-5-body-sm" id="work-metadata-view-count">…</p></div><div class="ds-work-card--work-metadata__stat"><span class="material-symbols-outlined" style="font-size: 20px" translate="no">description</span><p class="ds2-5-body-sm">21 pages</p></div><div class="ds-work-card--work-metadata__stat"><span class="material-symbols-outlined" style="font-size: 20px" translate="no">link</span><p class="ds2-5-body-sm">1 file</p></div></div><script>(async () => { const workId = 12356417; const worksViewsPath = "/v0/works/views?subdomain_param=api&work_ids%5B%5D=12356417"; const getWorkViews = async (workId) => { const response = await fetch(worksViewsPath); if (!response.ok) { throw new Error('Failed to load work views'); } const data = await response.json(); return data.views[workId]; }; // Get the view count for the work - we send this immediately rather than waiting for // the DOM to load, so it can be available as soon as possible (but without holding up // the backend or other resource requests, because it's a bit expensive and not critical). const viewCount = await getWorkViews(workId); const updateViewCount = (viewCount) => { try { const viewCountNumber = parseInt(viewCount, 10); if (viewCountNumber === 0) { // Remove the whole views element if there are zero views. document.getElementById('work-metadata-view-count')?.parentNode?.remove(); return; } const commaizedViewCount = viewCountNumber.toLocaleString(); const viewCountBody = document.getElementById('work-metadata-view-count'); if (!viewCountBody) { throw new Error('Failed to find work views element'); } viewCountBody.textContent = `${commaizedViewCount} views`; } catch (error) { // Remove the whole views element if there was some issue parsing. document.getElementById('work-metadata-view-count')?.parentNode?.remove(); throw new Error(`Failed to parse view count: ${viewCount}`, error); } }; // If the DOM is still loading, wait for it to be ready before updating the view count. if (document.readyState === "loading") { document.addEventListener('DOMContentLoaded', () => { updateViewCount(viewCount); }); // Otherwise, just update it immediately. } else { updateViewCount(viewCount); } })();</script></div><p class="ds-work-card--work-abstract ds-work-card--detail ds2-5-body-md">Lower ocean crust is primarily gabbroic, although 1-2% felsic igneous rocks that are referred to collectively as plagiogranites occur locally. Recent experimental evidence suggests that plagiogranite magmas can form by hydrous partial melting of gabbro triggered by seawater-derived fluids, and thus they may indicate early, high-temperature hydrothermal fluid circulation. To explore seawater-rock interaction prior to and during the genesis of plagiogranite and other late-stage magmas, oxygen-isotope ratios preserved in igneous zircon have been measured by ion microprobe. A total of 197 zircons from 43 plagiogranite, evolved gabbro, and hydrothermally altered fault rock samples have been analyzed. Samples originate primarily from drill core acquired during Ocean Drilling Program and Integrated Ocean Drilling Program operations near the Mid-Atlantic and Southwest Indian Ridges. With the exception of rare, distinctively luminescent rims, all zircons from ocean crust record remarkably uniform d 18 O with an average value of 5.2 ± 0.5% (2SD). The average d 18 O(Zrc) would be in magmatic equilibrium with unaltered MORB [d 18 O(WR) * 5.6-5.7%], and is consistent with the previously determined value for equilibrium with the mantle. The narrow range of measured d 18 O values is predicted for zircon crystallization from variable parent melt compositions and temperatures in a closed system, and provides no indication of any interactions between altered rocks or seawater and the evolved parent melts. If plagiogranite forms by hydrous partial melting, the uniform mantle-like d 18 O(Zrc) requires melting and zircon crystallization prior to significant amounts of water-rock interactions that alter the protolith d 18 O. Zircons from ocean crust have been proposed as a tectonic analog for [3.9 Ga detrital zircons from the earliest (Hadean) Earth by multiple workers. However, zircons from ocean crust are readily distinguished geochemically from zircons formed in continental crustal environments. Many of the [3.9 Ga zircons have mildly elevated d 18 O (6.0-7.5%), but such values have not been identified in any zircons from the large sample suite examined here. The difference in d 18 O, in combination with newly acquired lithium concentrations and published trace element data, clearly shows that the [3.9 Ga detrital zircons did not originate by processes analogous to those in modern mid-ocean ridge settings.</p><div class="ds-work-card--button-container"><button class="ds2-5-button js-swp-download-button" data-signup-modal="{"location":"continue-reading-button--work-card","attachmentId":46225699,"attachmentType":"pdf","workUrl":"https://www.academia.edu/12356417/Uniformly_mantle_like_%CE%B4_18_O_in_zircons_from_oceanic_plagiogranites_and_gabbros"}">See full PDF</button><button class="ds2-5-button ds2-5-button--secondary js-swp-download-button" data-signup-modal="{"location":"download-pdf-button--work-card","attachmentId":46225699,"attachmentType":"pdf","workUrl":"https://www.academia.edu/12356417/Uniformly_mantle_like_%CE%B4_18_O_in_zircons_from_oceanic_plagiogranites_and_gabbros"}"><span class="material-symbols-outlined" style="font-size: 20px" translate="no">download</span>Download PDF</button></div><div class="ds-signup-banner-trigger-container"><div class="ds-signup-banner-trigger ds-signup-banner-trigger-premium-marketing"></div></div><div class="ds-signup-banner ds-signup-banner-premium-marketing"><div id="ds-signup-banner-close-button"><button class="ds2-5-button ds2-5-button--secondary ds2-5-button--inverse"><span class="material-symbols-outlined" style="font-size: 20px" translate="no">close</span></button></div><div class="premium-banner-content"><div class="left"><img src="//a.academia-assets.com/images/academia-logo-capital-white.svg" /><span>Get access to the world's latest research</span></div><div class="right"><div class="card free"><div class="header">Free</div><div class="feature-list"><div class="feature"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">check</span><span>Download one paper at a time</span></div><div class="feature"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">check</span><span>Save papers to bookmarks</span></div><div class="feature"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">check</span><span>Basic search</span></div></div><button class="ds2-5-button ds2-5-button--secondary ds2-5-button--small ds2-5-button--inverse ds2-5-button--full-width js-swp-download-button" data-signup-modal="{"location":"premium-banner-desktop-free"}">Sign up for free</button></div><div class="card premium"><div class="pill">Recommended</div><div class="header premium">Premium</div><div class="feature-list"><div class="feature"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">check</span><span>Get highly curated PDF packages</span></div><div class="feature"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">check</span><span>Track your impact with Mentions</span></div><div class="feature"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">check</span><span>Access advanced search filters</span></div><div class="feature"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">check</span><span>Support Academia’s mission</span></div><div class="feature"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">check</span><span>Create your personal website</span></div></div><button class="ds2-5-button ds2-5-button--small ds2-5-button--inverse ds2-5-button--full-width js-swp-download-button" data-signup-modal="{"location":"premium-banner-desktop-upgrade","submitText":"Try Premium for $1"}">Try Premium for $1</button></div></div></div></div><script>(() => { // Set up signup banner show/hide behavior: // 1. 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The geochemistry of 267 zircon grains was measured by sensitive high-resolution ion microprobe-reverse geometry at the USGS-Stanford Ion Microprobe facility. Three types of zircon are recognized based on texture and geochemistry. Most ocean crustal zircons resemble young magmatic zircon from other crustal settings, occurring as pristine, colorless euhedral (Type 1) or subhedral to anhedral (Type 2) grains. In these grains, Hf and most trace elements vary systematically with Ti, typically becoming enriched with falling Ti-in-zircon temperature. Ti-in-zircon temperatures range from 1,040 to 660°C (corrected for a TiO2 & 0.7, a SiO2 & 1.0, pressure & 2 kbar); intra-sample variation is typically *60-150°C. Decreasing Ti correlates with enrichment in Hf to *2 wt%, while additional Hf-enrichment occurs at relatively constant temperature. Trends between Ti and U, Y, REE, and Eu/Eu* exhibit a similar inflection, which may denote the onset of eutectic crystallization; the inflection is well-defined by zircons from plagiogranite and implies solidus temperatures of *680-740°C. A third type of zircon is defined as being porous and colored with chaotic CL zoning, and occurs in *25% of rock samples studied. These features, along with high measured La, Cl, S, Ca, and Fe, and low (Sm/La) N ratios are suggestive of interaction with aqueous fluids. Non-porous, luminescent CL overgrowth rims on porous grains record uniform temperatures averaging 615 ± 26°C (2SD, n = 7), implying zircon formation below the wet-granite solidus and under water-saturated conditions. Zircon geochemistry reflects, in part, source region; elevated HREE coupled with low U concentrations allow effective discrimination of *80% of zircon formed at modern MORs from zircon in continental crust. The geochemistry and textural observations reported here serve as an important database for comparison with detrital, xenocrystic, and metamorphosed mafic rock-hosted zircon populations to evaluate provenance.</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"On the occurrence, trace element geochemistry, and crystallization history of zircon from in situ ocean lithosphere","attachmentId":48285224,"attachmentType":"pdf","work_url":"https://www.academia.edu/7935010/On_the_occurrence_trace_element_geochemistry_and_crystallization_history_of_zircon_from_in_situ_ocean_lithosphere","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/7935010/On_the_occurrence_trace_element_geochemistry_and_crystallization_history_of_zircon_from_in_situ_ocean_lithosphere"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="1" data-entity-id="12356181" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/12356181/Oxygen_isotope_ratios_and_rare_earth_elements_in_3_3_to_4_4_Ga_zircons_Ion_microprobe_evidence_for_high_sup_18_sup_O_continental_crust_and_oceans_in_the_Early_Archean">Oxygen isotope ratios and rare earth elements in 3.3 to 4.4 Ga zircons: Ion microprobe evidence for high ��< sup> 18</sup> O continental crust and oceans in the Early Archean</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="32816813" href="https://curtin.academia.edu/SimonWilde">Simon A Wilde</a><span>, </span><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="5479732" href="https://colgate.academia.edu/WilliamPeck">William Peck</a><span>, </span><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="31054590" href="https://wisc.academia.edu/JohnValley">John Valley</a></div><p class="ds-related-work--metadata ds2-5-body-xs">2001</p><p class="ds-related-work--abstract ds2-5-body-sm">Ion microprobe analyses of oxygen isotope ratios in Early Archean (Hadean) zircons (4.0-to 4.4-Ga) reveal variable magmatic ␦ 18 O values, including some that are high relative to the mantle, suggesting interaction between magmas and already-formed continental crust during the first 500 million yr of Earth's history. The high average ␦ 18 O value of these zircons is confirmed by conventional analysis. A metaconglomerate from the Jack Hills in the Yilgarn Craton (Western Australia) contains detrital zircons with ages Ͼ 4.0 Ga (Compston and Pidgeon, 1986) and one crystal that is 4.40-Ga old . The newly discovered 4.40-Ga grain is the oldest recognized terrestrial mineral. The Jack Hills metaconglomerate also contains a large 3.3-to 3.6-Ga-old zircon population with an average ␦ 18 O value of 6.3 Ϯ 0.1‰ (1 s.e., ; n ϭ 32 spot analyses). Two 4.15-Ga zircons have an average ␦ 18 O of 5.7 Ϯ 0.2‰ (n ϭ 13). In addition, a 4.13-Ga zircon has an average ␦ 18 O of 7.2 Ϯ 0.3‰ (n ϭ 8) and another 4.01-Ga zircon has an average ␦ 18 O of 6.8 Ϯ 0.4‰ (n ϭ 10). The oldest grain (4.40 Ga) is zoned with respect trace element composition (especially LREE), and intensity of cathodoluminescence, all of which correlate with oxygen isotope ratios (7.4‰ vs. 5.0‰). High LREE and high-␦ 18 O values from the 4.01-to 4.40-Ga grains are consistent with growth in evolved granitic magmas (␦ 18 O(WR) ϭ 8.5 to 9.5‰) that had interacted with supracrustal materials. High ␦ 18 O values show that low-temperature surficial processes (i.e., diagenesis, weathering, or low-temperature alteration) occurred before 4.0 Ga, and even before 4.40 Ga, shortly following the hypothesized date of core differentiation and impact of a Mars-sized body to form the Moon at ϳ4.45 Ga. This is the first evidence of continental crust as early as 4.40 Ga and suggests differentiation during the period of intense meteorite bombardment of the early Earth. The magnitude of water and rock interaction that would be necessary to cause the high ␦ 18 O values suggests the presence of liquid water and thus the possibility of an ocean at 4.40 Ga.</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"Oxygen isotope ratios and rare earth elements in 3.3 to 4.4 Ga zircons: Ion microprobe evidence for high ��\u003c sup\u003e 18\u003c/sup\u003e O continental crust and oceans in the Early Archean","attachmentId":46225761,"attachmentType":"pdf","work_url":"https://www.academia.edu/12356181/Oxygen_isotope_ratios_and_rare_earth_elements_in_3_3_to_4_4_Ga_zircons_Ion_microprobe_evidence_for_high_sup_18_sup_O_continental_crust_and_oceans_in_the_Early_Archean","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/12356181/Oxygen_isotope_ratios_and_rare_earth_elements_in_3_3_to_4_4_Ga_zircons_Ion_microprobe_evidence_for_high_sup_18_sup_O_continental_crust_and_oceans_in_the_Early_Archean"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="2" data-entity-id="24604346" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/24604346/Oxygen_isotope_ratios_and_rare_earth_elements_in_3_3_to_4_4_Ga_zircons_Ion_microprobe_evidence_for_high_%CE%B418O_continental_crust_and_oceans_in_the_Early_Archean">Oxygen isotope ratios and rare earth elements in 3.3 to 4.4 Ga zircons: Ion microprobe evidence for high δ18O continental crust and oceans in the Early Archean</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="30027441" href="https://independent.academia.edu/ColinGraham2">Colin Graham</a></div><p class="ds-related-work--metadata ds2-5-body-xs">Geochimica et Cosmochimica Acta, 2001</p><p class="ds-related-work--abstract ds2-5-body-sm">Ion microprobe analyses of oxygen isotope ratios in Early Archean (Hadean) zircons (4.0-to 4.4-Ga) reveal variable magmatic ␦ 18 O values, including some that are high relative to the mantle, suggesting interaction between magmas and already-formed continental crust during the first 500 million yr of Earth's history. The high average ␦ 18 O value of these zircons is confirmed by conventional analysis. A metaconglomerate from the Jack Hills in the Yilgarn Craton (Western Australia) contains detrital zircons with ages Ͼ 4.0 Ga (Compston and Pidgeon, 1986) and one crystal that is 4.40-Ga old . The newly discovered 4.40-Ga grain is the oldest recognized terrestrial mineral. The Jack Hills metaconglomerate also contains a large 3.3-to 3.6-Ga-old zircon population with an average ␦ 18 O value of 6.3 Ϯ 0.1‰ (1 s.e., ; n ϭ 32 spot analyses). Two 4.15-Ga zircons have an average ␦ 18 O of 5.7 Ϯ 0.2‰ (n ϭ 13). In addition, a 4.13-Ga zircon has an average ␦ 18 O of 7.2 Ϯ 0.3‰ (n ϭ 8) and another 4.01-Ga zircon has an average ␦ 18 O of 6.8 Ϯ 0.4‰ (n ϭ 10). The oldest grain (4.40 Ga) is zoned with respect trace element composition (especially LREE), and intensity of cathodoluminescence, all of which correlate with oxygen isotope ratios (7.4‰ vs. 5.0‰). High LREE and high-␦ 18 O values from the 4.01-to 4.40-Ga grains are consistent with growth in evolved granitic magmas (␦ 18 O(WR) ϭ 8.5 to 9.5‰) that had interacted with supracrustal materials. High ␦ 18 O values show that low-temperature surficial processes (i.e., diagenesis, weathering, or low-temperature alteration) occurred before 4.0 Ga, and even before 4.40 Ga, shortly following the hypothesized date of core differentiation and impact of a Mars-sized body to form the Moon at ϳ4.45 Ga. This is the first evidence of continental crust as early as 4.40 Ga and suggests differentiation during the period of intense meteorite bombardment of the early Earth. The magnitude of water and rock interaction that would be necessary to cause the high ␦ 18 O values suggests the presence of liquid water and thus the possibility of an ocean at 4.40 Ga.</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"Oxygen isotope ratios and rare earth elements in 3.3 to 4.4 Ga zircons: Ion microprobe evidence for high δ18O continental crust and oceans in the Early Archean","attachmentId":44933870,"attachmentType":"pdf","work_url":"https://www.academia.edu/24604346/Oxygen_isotope_ratios_and_rare_earth_elements_in_3_3_to_4_4_Ga_zircons_Ion_microprobe_evidence_for_high_%CE%B418O_continental_crust_and_oceans_in_the_Early_Archean","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/24604346/Oxygen_isotope_ratios_and_rare_earth_elements_in_3_3_to_4_4_Ga_zircons_Ion_microprobe_evidence_for_high_%CE%B418O_continental_crust_and_oceans_in_the_Early_Archean"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="3" data-entity-id="80725116" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/80725116/Morphology_and_impurity_elements_of_zircon_in_the_oceanic_lithosphere_at_the_Mid_Atlantic_ridge_axial_zone_6_13_N_Evidence_of_specifics_of_magmatic_crystallization_and_postmagmatic_transformations">Morphology and impurity elements of zircon in the oceanic lithosphere at the Mid-Atlantic ridge axial zone (6°–13° N): Evidence of specifics of magmatic crystallization and postmagmatic transformations</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="3603435" href="https://independent.academia.edu/LeonidAranovich">Leonid Aranovich</a></div><p class="ds-related-work--metadata ds2-5-body-xs">Petrology, 2017</p><p class="ds-related-work--abstract ds2-5-body-sm">⎯The paper presents newly obtained original data on the morphology, internal structure (as seen in cathodoluminescence images, CL), and composition of more than 400 zircon grains separated from gabbroids and plagiogranites (OPG) sampled at the axial zone of the Mid-Atlantic Ridge (MAR). The zircons were analyzed for REE by LA-ICP-MS and for Hf, U, Th, Y, and P by EPMA. Magmatic zircon in the gabbroids crystallized from differentiating magmatic melt in a number of episodes, as follows from systematic rimward increase in the Hf concentration, and also often from the simultaneous increase in the (U + Th) and (Y + P) concentrations. These tendencies are also discernible (although much less clearly) in zircons from the OPG. Zircon in the OPG is depleted in REE compared to the least modified zircons in the gabbro, which suggests that the OPG were derived via partial melting of gabbro in the presence of seawater-derived concentrated aqueous salt fluid. Another reason for the REE depletion might be simultaneous crystallization of zircon and apatite. The CL-dark sectors, which are found in practically all of the magmatic zircon grains, have Y/P (a.p.f.u.) 1 which most likely resulted from OH accommodation in the zircon structure, a fact suggesting that the OPG parental melt contained water. High-temperature hydrothermal processes induced partial to complete recrystallization of zircon (via dissolution-reprecepitation), a process that was associated with ductile and brittle deformations of the zircon-hosting rocks. The morphology of the hydrothermal zircons varies depending on pH and silica activity in the fluid from weakly corroded subhedral crystals with typical vermicular microtopography of the crystal faces to completely modified grains of colloform structure. Geochemically, the earlier hydrothermal transformations of the zircons resulted in their enrichment in La and other LREE, except only Ce, whose concentration, conversely, decreases compared to that of the unmodified magmatic zircons. The hydrothermal zircon displays a reduced Ce anomaly and its most altered domains typically host minute inclusions of xenotime, U and Th oxides and silicates, and occasionally also baddeleyite, which suggests that the hydrothermal fluid was reduced and highly alkaline. These features were acquired by the seawater-derived fluid when it circulated within the axial MAR zone area due to phase separation in the H 2 O-NaCl system and particularly as a result of fluid interaction with the abyssal peridotites of oceanic core complexes. Our data demonstrate that zircon is a sensitive indicator of tectonic and physicochemical processes in the oceanic crust.</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"Morphology and impurity elements of zircon in the oceanic lithosphere at the Mid-Atlantic ridge axial zone (6°–13° N): Evidence of specifics of magmatic crystallization and postmagmatic transformations","attachmentId":87012214,"attachmentType":"pdf","work_url":"https://www.academia.edu/80725116/Morphology_and_impurity_elements_of_zircon_in_the_oceanic_lithosphere_at_the_Mid_Atlantic_ridge_axial_zone_6_13_N_Evidence_of_specifics_of_magmatic_crystallization_and_postmagmatic_transformations","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/80725116/Morphology_and_impurity_elements_of_zircon_in_the_oceanic_lithosphere_at_the_Mid_Atlantic_ridge_axial_zone_6_13_N_Evidence_of_specifics_of_magmatic_crystallization_and_postmagmatic_transformations"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="4" data-entity-id="25015853" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/25015853/Magmatic_%CE%B418O_in_4400_3900_Ma_detrital_zircons_A_record_of_the_alteration_and_recycling_of_crust_in_the_Early_Archean">Magmatic δ18O in 4400–3900 Ma detrital zircons: A record of the alteration and recycling of crust in the Early Archean</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="32816813" href="https://curtin.academia.edu/SimonWilde">Simon A Wilde</a></div><p class="ds-related-work--metadata ds2-5-body-xs">Earth and Planetary Science Letters, 2005</p><p class="ds-related-work--abstract ds2-5-body-sm">Ion microprobe analyses of y 18 O in 4400-3900 Ma igneous zircons from the Jack Hills, Western Australia, provide a record of the oxygen isotope composition of magmas in the earliest Archean. We have employed a detailed analysis protocol aimed at correlating spatially related micro-volumes of zircon concordant in U/Pb age with y 18 O and internal zoning. Simultaneous analysis of 18 O and 16 O with dual Faraday cup detectors, combined with frequent standardization, has yielded data with improved accuracy and precision over prior studies, and resulted in a narrower range of what is interpreted as magmatic y 18 O in N 3900 Ma zircons. Preserved magmatic y 18 O values from individual zircons (Zrc) range from 5.3x to 7.3x (VSMOW), and increasingly deviate from the mantle range of 5.3 F 0.3x as zircons decrease in age from 4400 to 4200 Ma. Elevated y 18 O (Zrc) values up to 6.5x occur as early as 4325 Ma, which suggests that evolved rocks were incorporated into magmas within~230 Ma of Earth's accretion. Values of magmatic y 18 O (Zrc) as high as 7.3x are recorded in zircons by 4200 Ma, and are common thereafter. The protoliths of the magmas these zircons crystallized in were altered by low temperature interaction with liquid water near EarthTs surface. These results provide the strongest evidence yet for the existence of liquid water oceans and supracrustal rocks by approximately 4200 Ma, and possibly as early as 4325 Ma. The range of magmatic y 18 O values in the 4400-3900 Ma zircons is indistinguishable from Archean igneous zircons, suggesting similar magmatic processes occurred over the first two billion years of recorded Earth history. Zircons with sub-solidus alteration histories, identified by the presence of disturbed internal zoning patterns, record y 18 O values both below (4.6x) and above (10.3x) the observed range for primary magmatic zircon, and are unreliable indicators of Early Archean magma chemistry. D</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"Magmatic δ18O in 4400–3900 Ma detrital zircons: A record of the alteration and recycling of crust in the Early Archean","attachmentId":45340869,"attachmentType":"pdf","work_url":"https://www.academia.edu/25015853/Magmatic_%CE%B418O_in_4400_3900_Ma_detrital_zircons_A_record_of_the_alteration_and_recycling_of_crust_in_the_Early_Archean","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/25015853/Magmatic_%CE%B418O_in_4400_3900_Ma_detrital_zircons_A_record_of_the_alteration_and_recycling_of_crust_in_the_Early_Archean"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="5" data-entity-id="76475270" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/76475270/Perspectives_on_the_origin_of_plagiogranite_in_ophiolites_from_oxygen_isotopes_in_zircon">Perspectives on the origin of plagiogranite in ophiolites from oxygen isotopes in zircon</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="47910480" href="https://independent.academia.edu/CraigGrimes2">Craig Grimes</a></div><p class="ds-related-work--metadata ds2-5-body-xs">Lithos, 2013</p><p class="ds-related-work--abstract ds2-5-body-sm">The formation of oceanic plagiogranite has been attributed primarily to either 1) extreme fractional crystallization of a mantle melt, or 2) partial melting of hydrated mafic crust, with support for the latter from field evidence and recent melting experiments. Remelting of hydrothermally-altered ocean crust could yield rocks (and minerals) with diverse primary magmatic δ 18 O values forming proximal to the magmatic center where crustal growth is occurring. To constrain the magmatic δ 18 O of a wide range of silicic rocks in oceanic crust and evaluate their petrogenesis, we characterized the δ 18 O of zircons in 22 plagiogranite samples (tonalite and trondhjemite) from 8 different ophiolites and one dacite sampled along the East Pacific Rise using Secondary Ion Mass Spectrometry (SIMS). The δ 18 O values of 202 magmatic zircons from ophiolites range from 3.9 to 5.6‰ (n = 244 spots; average 4.9 ± 0.6‰; 2SD), extending ~1‰ below typical zircon in equilibrium with mantle and from gabbroic massifs along slow-spreading mid-ocean ridges (4.7-5.9‰). East Pacific Rise dacite zircons range from 4.6 to 5.0‰ (n = 12 spots). Plagiogranite from the dike-gabbro transition zone of the northern Oman Ophiolite yield the lowest δ 18 O(Zrn), with rock-average values of 4.3-5.0‰. The low-δ 18 O values are best explained by remelting of crust altered by hydrothermal fluids with seawater-like isotopic compositions at high temperatures, possibly due to vertical migration of the boundary between an active magma chamber and a vigorous high-temperature hydrothermal system in the overlying crust. If the partial melt was assimilated into a fractionating melt lens with MORB-like δ 18 O, as envisioned for km-scale plagiogranite bodies in Oman, up to 20% contamination by a protolith with δ 18 O = 2‰ would be required. Previous oxygen isotope constraints from quartz in Oman plagiogranite suggested melting of both high and low δ 18 O crust had occurred; comparison of quartz-zircon pairs indicates that quartz has been modified in most samples, and we find no evidence for the involvement of high-δ 18 O rocks during plagiogranite formation.</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"Perspectives on the origin of plagiogranite in ophiolites from oxygen isotopes in zircon","attachmentId":84172316,"attachmentType":"pdf","work_url":"https://www.academia.edu/76475270/Perspectives_on_the_origin_of_plagiogranite_in_ophiolites_from_oxygen_isotopes_in_zircon","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/76475270/Perspectives_on_the_origin_of_plagiogranite_in_ophiolites_from_oxygen_isotopes_in_zircon"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="6" data-entity-id="12356176" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/12356176/Evidence_from_detrital_zircons_for_the_existence_of_continental_crust_and_oceans_on_the_Earth_4_4_Gyr_ago">Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="55204412" href="https://independent.academia.edu/WilliamPeck2">William Peck</a><span>, </span><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="31054590" href="https://wisc.academia.edu/JohnValley">John Valley</a></div><p class="ds-related-work--metadata ds2-5-body-xs">2001</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago","attachmentId":46225760,"attachmentType":"pdf","work_url":"https://www.academia.edu/12356176/Evidence_from_detrital_zircons_for_the_existence_of_continental_crust_and_oceans_on_the_Earth_4_4_Gyr_ago","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/12356176/Evidence_from_detrital_zircons_for_the_existence_of_continental_crust_and_oceans_on_the_Earth_4_4_Gyr_ago"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="7" data-entity-id="58347899" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/58347899/Zircon_in_gabbroids_from_the_axial_zone_of_the_Mid_Atlantic_ridge_Markov_Deep_6_N_Correlation_of_geochemical_features_with_petrogenetic_processes">Zircon in gabbroids from the axial zone of the Mid-Atlantic ridge, Markov Deep, 6° N: Correlation of geochemical features with petrogenetic processes</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="3603435" href="https://independent.academia.edu/LeonidAranovich">Leonid Aranovich</a></div><p class="ds-related-work--metadata ds2-5-body-xs">Petrology, 2013</p><p class="ds-related-work--abstract ds2-5-body-sm">This paper reports the results of detailed petrological-geochemical study of zircons and host rocks that were dredged from the Markov Deep area in the slow spreading Mid Atlantic ridge. The rocks are rep resented by variably cataclased gabbronorite with veinlets of oceanic plagiogranite (OPG) as well as leuco cratic gabbro (primitive gabbro) and hornblende Fe-Ti oxide gabbronorite (ferrogabbro) without OPG. The studied zircons differ in morphology, inner structure, set of mineral inclusions (ingrowths), and content of trace elements. Compositional heterogeneity is also observed within individual grains. The REE distribution patterns in zircons are characterized by gentle growth from LREE to HREE, with prominent positive Ce anomaly and negative Eu anomaly, and in general fall in the range of zircons from magmatic rocks. Oceanic zircons clearly differ from continental populations in the U/Yb-Y and U/Yb-Hf discrimination diagrams, primarily, due to their lower U/Yb ratio at wide variations of Y and Hf contents. Zircons that contain inclu sions of acid glass and hence, crystallized from OPG melt are relatively depleted in REE, especially HREE. This indicates that OPG was formed by partial melting of gabbro in the presence of concentrated water-salt fluid, which extracted REE from the plagiogranite melt. Zircons from gabbroids devoid of OPG inclusions have higher total REE contents than zircons from OPG. Late hydrothermal alterations of zircon are distinctly established by the formation of neogenic collomorphic (porous) texture and/or by composition of mineral inclusions and accompanied by significant enrichment in La. Heterogeneous distribution of Ti in zircon may be caused not only by a change in its crystallization temperature, but also variations in silica to titanium oxide activity ratios in the rocks during interaction with hydrothermal solution of variable acidity. A complex study of structural-morphological and geochemical features of oceanic zircons and phase composition of host rocks and inclusions provides insight into processes leading to the crystallization and subsequent evolution of this mineral in the rocks of oceanic lithosphere.</p><div class="ds-related-work--ctas"><button class="ds2-5-text-link ds2-5-text-link--inline js-swp-download-button" data-signup-modal="{"location":"wsj-grid-card-download-pdf-modal","work_title":"Zircon in gabbroids from the axial zone of the Mid-Atlantic ridge, Markov Deep, 6° N: Correlation of geochemical features with petrogenetic processes","attachmentId":72804371,"attachmentType":"pdf","work_url":"https://www.academia.edu/58347899/Zircon_in_gabbroids_from_the_axial_zone_of_the_Mid_Atlantic_ridge_Markov_Deep_6_N_Correlation_of_geochemical_features_with_petrogenetic_processes","alternativeTracking":true}"><span class="material-symbols-outlined" style="font-size: 18px" translate="no">download</span><span class="ds2-5-text-link__content">Download free PDF</span></button><a class="ds2-5-text-link ds2-5-text-link--inline js-wsj-grid-card-view-pdf" href="https://www.academia.edu/58347899/Zircon_in_gabbroids_from_the_axial_zone_of_the_Mid_Atlantic_ridge_Markov_Deep_6_N_Correlation_of_geochemical_features_with_petrogenetic_processes"><span class="ds2-5-text-link__content">View PDF</span><span class="material-symbols-outlined" style="font-size: 18px" translate="no">chevron_right</span></a></div></div><div class="ds-related-work--container js-wsj-grid-card" data-collection-position="8" data-entity-id="12356276" data-sort-order="default"><a class="ds-related-work--title js-wsj-grid-card-title ds2-5-body-md ds2-5-body-link" href="https://www.academia.edu/12356276/Correlated_microanalysis_of_zircon_Trace_element_sup_18_sup_O_and_U_Th_Pb_isotopic_constraints_on_the_igneous_origin_of_complex_3900Ma_detrital_grains">Correlated microanalysis of zircon: Trace element, ��< sup> 18</sup> O, and U��Th��Pb isotopic constraints on the igneous origin of complex> 3900Ma detrital grains</a><div class="ds-related-work--metadata"><a class="js-wsj-grid-card-author ds2-5-body-sm ds2-5-body-link" data-author-id="31054590" href="https://wisc.academia.edu/JohnValley">John Valley</a></div><p class="ds-related-work--metadata ds2-5-body-xs">2006</p><p class="ds-related-work--abstract ds2-5-body-sm">The origins of >3900 Ma detrital zircons from Western Australia are controversial, in part due to their complexity and long geologic histories. Conflicting interpretations for the genesis of these zircons propose magmatic, hydrothermal, or metamorphic origins. To test the hypothesis that these zircons preserve magmatic compositions, trace elements [rare earth elements (REE), Y, P, Th, U] were analyzed by ion microprobe from a suite of >3900 Ma zircons from Jack Hills, Western Australia, and include some of the oldest detrital zircons known (4400-4300 Ma). The same $20 lm domains previously characterized for U/Pb age, oxygen isotope composition (d 18 O), and cathodoluminescence (CL) zoning were specifically targeted for analysis. The zircons are classified into two types based on the light-REE (LREE) composition of the domain analyzed. Zircons with Type 1 domains form the largest group (37 of 42), consisting of grains that preserve evolved REE compositions typical of igneous zircon from crustal rocks. Grains with Type 1 domains display a wide range of CL zoning patterns, yield nearly concordant U/Pb ages from 4400 to 3900 Ma, and preserve a narrow range of d 18 O values from 4.7& to 7.3& that overlap or are slightly elevated relative to mantle oxygen isotope composition. Type 1 domains are interpreted to preserve magmatic compositions. Type 2 domains occur in six zircons that contain spots with enriched light-REE (LREE) compositions, here defined as having chondrite normalized values of La N > 1 and Pr N > 10. A subset of analyses in Type 2 domains appear to result from incorporation of sub-surface mineral inclusions in the analysis volume, as evidenced by positively correlated secondary ion beam intensities for LREE, P, and Y, which are anti-correlated to Si, although not all Type 2 analyses show these features. The LREE enrichment also occurs in areas with discordant U/Pb ages and/or high Th/U ratios, and is apparently associated with past or present radiation damage. The enrichment is not attributed to hydrothermal alteration, however, as oxygen isotope ratios in Type 2 domains overlap with magmatic values of Type 1 domains, and do not appear re-set as might be expected from dissolution or ion-exchange processes operating at variable temperatures. Thus, REE compositions in Type 2 domains where mineral inclusions are not suspected are best interpreted to result from localized enrichment of LREE in areas with past or present radiation damage, and with a very low fluid/rock ratio. Correlated in situ analyses allow magmatic compositions in these complex zircons to be distinguished from the effects of secondary processes. These results are additional evidence for preservation of magmatic compositions in Jack Hills zircons, and demonstrate the benefits of detailed imaging in studies of complicated detrital zircons of unknown origin. 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