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if ($a.is_logged_in() && $viewedUser.is_current_user()) { $('body').addClass('profile-viewed-by-owner'); } $socialProfiles = []</script><div id="js-react-on-rails-context" style="display:none" data-rails-context="{"inMailer":false,"i18nLocale":"en","i18nDefaultLocale":"en","href":"https://oxford.academia.edu/ChrisSiebert","location":"/ChrisSiebert","scheme":"https","host":"oxford.academia.edu","port":null,"pathname":"/ChrisSiebert","search":null,"httpAcceptLanguage":null,"serverSide":false}"></div> <div class="js-react-on-rails-component" style="display:none" data-component-name="ProfileCheckPaperUpdate" data-props="{}" data-trace="false" data-dom-id="ProfileCheckPaperUpdate-react-component-0ddfb780-da98-4ff9-bc0e-7a5f3675777f"></div> <div id="ProfileCheckPaperUpdate-react-component-0ddfb780-da98-4ff9-bc0e-7a5f3675777f"></div> <div class="DesignSystem"><div class="onsite-ping" id="onsite-ping"></div></div><div class="profile-user-info DesignSystem"><div class="social-profile-container"><div class="left-panel-container"><div class="user-info-component-wrapper"><div class="user-summary-cta-container"><div class="user-summary-container"><div class="social-profile-avatar-container"><img class="profile-avatar u-positionAbsolute" alt="Chris Siebert" border="0" onerror="if (this.src != '//a.academia-assets.com/images/s200_no_pic.png') this.src = '//a.academia-assets.com/images/s200_no_pic.png';" width="200" height="200" src="https://0.academia-photos.com/327766/354915/425562/s200_chris.siebert.jpg" /></div><div class="title-container"><h1 class="ds2-5-heading-sans-serif-sm">Chris Siebert</h1><div class="affiliations-container fake-truncate js-profile-affiliations"><div><a class="u-tcGrayDarker" href="https://oxford.academia.edu/">University of Oxford</a>, <a class="u-tcGrayDarker" href="https://oxford.academia.edu/Departments/Earth_Sciences/Documents">Earth Sciences</a>, <span class="u-tcGrayDarker">Post-Doc</span></div></div></div></div><div class="sidebar-cta-container"><button class="ds2-5-button hidden profile-cta-button grow js-profile-follow-button" data-broccoli-component="user-info.follow-button" data-click-track="profile-user-info-follow-button" data-follow-user-fname="Chris" data-follow-user-id="327766" data-follow-user-source="profile_button" data-has-google="false"><span class="material-symbols-outlined" style="font-size: 20px" translate="no">add</span>Follow</button><button class="ds2-5-button hidden profile-cta-button grow js-profile-unfollow-button" data-broccoli-component="user-info.unfollow-button" data-click-track="profile-user-info-unfollow-button" data-unfollow-user-id="327766"><span class="material-symbols-outlined" style="font-size: 20px" translate="no">done</span>Following</button></div></div><div class="user-stats-container"><a><div class="stat-container js-profile-followers"><p class="label">Followers</p><p class="data">48</p></div></a><a><div class="stat-container js-profile-followees" data-broccoli-component="user-info.followees-count" data-click-track="profile-expand-user-info-following"><p class="label">Following</p><p class="data">23</p></div></a><div class="js-mentions-count-container" style="display: none;"><a href="/ChrisSiebert/mentions"><div class="stat-container"><p class="label">Mentions</p><p class="data"></p></div></a></div><span><div class="stat-container"><p class="label"><span class="js-profile-total-view-text">Public Views</span></p><p class="data"><span class="js-profile-view-count"></span></p></div></span></div><div class="user-bio-container"><div class="profile-bio fake-truncate js-profile-about" style="margin: 0px;">My research focuses on the development and application of new geochemical and isotopic tracers particularly in marine geochemistry and paleoceanography, where I am focusing on the use of "non-traditional" or "heavy" stable isotopes (e.g. Mo, Ge, Fe, W, Ni). I am also applying these isotope tracers to other problems in Earth Sciences such as weathering processes, hydrothermal processes, biochemistry and evolution of our solar system.<br /><br />An example of my research is the application of stable heavy isotope fractionation (in particular molybdenum) as tracer in various archives to obtain records of past ocean redox- and terrestrial weathering conditions. In order to achieve this, I aim at understanding the basic processes controlling the sources, sinks and speciation of Mo and its isotopes in the hydro- and lithosphere systems and interfaces.<br /><div class="js-profile-less-about u-linkUnstyled u-tcGrayDarker u-textDecorationUnderline u-displayNone">less</div></div></div><div class="suggested-academics-container"><div class="suggested-academics--header"><p class="ds2-5-body-md-bold">Related Authors</p></div><ul class="suggested-user-card-list"><div class="suggested-user-card"><div class="suggested-user-card__avatar social-profile-avatar-container"><a href="https://independent.academia.edu/JonSOlafsson"><img class="profile-avatar u-positionAbsolute" border="0" alt="" src="//a.academia-assets.com/images/s200_no_pic.png" /></a></div><div class="suggested-user-card__user-info"><a class="suggested-user-card__user-info__header ds2-5-body-sm-bold ds2-5-body-link" href="https://independent.academia.edu/JonSOlafsson">Jon S 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class="ri-section-header"><span>Interests</span><a class="ri-more-link js-profile-ri-list-card" data-click-track="profile-user-info-primary-research-interest" data-has-card-for-ri-list="327766">View All (6)</a></div><div class="ri-tags-container"><a data-click-track="profile-user-info-expand-research-interests" data-has-card-for-ri-list="327766" href="https://www.academia.edu/Documents/in/Earth_Sciences"><div id="js-react-on-rails-context" style="display:none" data-rails-context="{"inMailer":false,"i18nLocale":"en","i18nDefaultLocale":"en","href":"https://oxford.academia.edu/ChrisSiebert","location":"/ChrisSiebert","scheme":"https","host":"oxford.academia.edu","port":null,"pathname":"/ChrisSiebert","search":null,"httpAcceptLanguage":null,"serverSide":false}"></div> <div class="js-react-on-rails-component" style="display:none" data-component-name="Pill" data-props="{"color":"gray","children":["Earth Sciences"]}" data-trace="false" 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data-dom-id="Pill-react-component-e5e132a0-a354-4a30-b8a0-b19c584a699c"></div> <div id="Pill-react-component-e5e132a0-a354-4a30-b8a0-b19c584a699c"></div> </a></div></div></div></div><div class="right-panel-container"><div class="user-content-wrapper"><div class="uploads-container" id="social-redesign-work-container"><div class="upload-header"><h2 class="ds2-5-heading-sans-serif-xs">Uploads</h2></div><div class="documents-container backbone-social-profile-documents" style="width: 100%;"><div class="u-taCenter"></div><div class="profile--tab_content_container js-tab-pane tab-pane active" id="all"><div class="profile--tab_heading_container js-section-heading" data-section="Papers" id="Papers"><h3 class="profile--tab_heading_container">Papers by Chris Siebert</h3></div><div class="js-work-strip profile--work_container" data-work-id="1117227"><div class="profile--work_thumbnail hidden-xs"><a class="js-work-strip-work-link" data-click-track="profile-work-strip-thumbnail" href="https://www.academia.edu/1117227/Quantifying_the_impact_of_freshwater_diatom_productivity_on_silicon_isotopes_and_silicon_fluxes_Lake_Myvatn_Iceland"><img alt="Research paper thumbnail of Quantifying the impact of freshwater diatom productivity on silicon isotopes and silicon fluxes: Lake Myvatn, Iceland" class="work-thumbnail" src="https://attachments.academia-assets.com/6880366/thumbnails/1.jpg" /></a></div><div class="wp-workCard wp-workCard_itemContainer"><div class="wp-workCard_item wp-workCard--title"><a class="js-work-strip-work-link text-gray-darker" data-click-track="profile-work-strip-title" href="https://www.academia.edu/1117227/Quantifying_the_impact_of_freshwater_diatom_productivity_on_silicon_isotopes_and_silicon_fluxes_Lake_Myvatn_Iceland">Quantifying the impact of freshwater diatom productivity on silicon isotopes and silicon fluxes: Lake Myvatn, Iceland</a></div><div class="wp-workCard_item"><span class="js-work-more-abstract-truncated">Keywords: silicon isotopes diatom biogenic Si dissolution groundwater Lake Myvatn Iceland Diatom ...</span><a class="js-work-more-abstract" data-broccoli-component="work_strip.more_abstract" data-click-track="profile-work-strip-more-abstract" href="javascript:;"><span> more </span><span><i class="fa fa-caret-down"></i></span></a><span class="js-work-more-abstract-untruncated hidden">Keywords: silicon isotopes diatom biogenic Si dissolution groundwater Lake Myvatn Iceland Diatom productivity in the oceans plays a crucial role in the carbon cycle, but is strongly dependent upon the continental silicon supply. However, the relative influence of weathering and biological processes on continental Si fluxes remains poorly constrained. This study aims to quantify the impact of terrestrial diatom productivity on Si fluxes to the ocean. Lake Myvatn in North Iceland is one of the most productive lakes in the Northern Hemisphere, with nutrient-rich waters almost uniquely sourced by groundwater. The primary production is mainly controlled by diatom growth but also by cyanobacteria, and the lake output is via a single river, thereby providing a relatively simple natural laboratory to quantify the impact of diatom growth on the chemistry and Si budget of lake waters. Silicon stable isotopes (δ 30 Si) provide a tracer of this biocycling, and have been measured in groundwater inputs to the lake, and in time-series monitoring of waters at the lake outlet. The δ 30 Si values at the outlet range from + 0.70 ± 0.08 to + 1.42 ± 0.06‰, which is significantly heavier than the groundwater input (average cold and hot springs: + 0.50 ± 0.17‰, 2SD) and consistent with the preferential uptake of light Si isotopes by diatoms. The δ 30 Si value at the outlet increases by up to 0.9‰ in spring and autumn relative to the Si isotope composition of the inflow. These seasonal diatom blooms can be modeled by an open system of Si uptake and affect Si fluxes at the outlet of the lake by up to 79%, or 53% integrated over the year. In the summer a shift to lighter δ 30 Si values is correlated with a higher pH, which results in dissolution of diatoms releasing light Si isotopes. From mass balance, this seasonal diatom dissolution affects Si fluxes by up to 33%, but is limited to 3.7% integrated over the year. These results clearly illustrate that biological activity can have a significant impact on both isotope composition and elemental abundance of continental derived Si. They also demonstrate the pH dependency of diatom dissolution and/or preservation, which is likely to affect not only the continental Si fluxes to the ocean but also the Si recycling in the oceans themselves.</span></div><div class="wp-workCard_item wp-workCard--actions"><span class="work-strip-bookmark-button-container"></span><a id="3a14ea6692b70fd06bb5cf6aa7ddfb80" class="wp-workCard--action" rel="nofollow" data-click-track="profile-work-strip-download" data-download="{"attachment_id":6880366,"asset_id":1117227,"asset_type":"Work","button_location":"profile"}" href="https://www.academia.edu/attachments/6880366/download_file?s=profile"><span><i class="fa fa-arrow-down"></i></span><span>Download</span></a><span class="wp-workCard--action visible-if-viewed-by-owner inline-block" style="display: none;"><span class="js-profile-work-strip-edit-button-wrapper profile-work-strip-edit-button-wrapper" data-work-id="1117227"><a class="js-profile-work-strip-edit-button" tabindex="0"><span><i class="fa fa-pencil"></i></span><span>Edit</span></a></span></span></div><div class="wp-workCard_item wp-workCard--stats"><span><span><span class="js-view-count view-count u-mr2x" data-work-id="1117227"><i class="fa fa-spinner fa-spin"></i></span><script>$(function () { var workId = 1117227; 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$(this).data('initialized', true); } }); $a.trackClickSource(".js-work-strip-work-link", "profile_work_strip") }); </script> <div class="js-work-strip profile--work_container" data-work-id="1117221"><div class="profile--work_thumbnail hidden-xs"><a class="js-work-strip-work-link" data-click-track="profile-work-strip-thumbnail" href="https://www.academia.edu/1117221/Sedimentary_Mo_isotope_record_across_the_Holocene_fresh_brackish_water_transition_of_the_Black_Sea"><img alt="Research paper thumbnail of Sedimentary Mo isotope record across the Holocene fresh–brackish water transition of the Black Sea" class="work-thumbnail" src="https://attachments.academia-assets.com/6880347/thumbnails/1.jpg" /></a></div><div class="wp-workCard wp-workCard_itemContainer"><div class="wp-workCard_item wp-workCard--title"><a class="js-work-strip-work-link text-gray-darker" data-click-track="profile-work-strip-title" href="https://www.academia.edu/1117221/Sedimentary_Mo_isotope_record_across_the_Holocene_fresh_brackish_water_transition_of_the_Black_Sea">Sedimentary Mo isotope record across the Holocene fresh–brackish water transition of the Black Sea</a></div><div class="wp-workCard_item"><span class="js-work-more-abstract-truncated">Mo isotope data on Black Sea sediments spanning the transition from Pleistocene oxic-limnic condi...</span><a class="js-work-more-abstract" data-broccoli-component="work_strip.more_abstract" data-click-track="profile-work-strip-more-abstract" href="javascript:;"><span> more </span><span><i class="fa fa-caret-down"></i></span></a><span class="js-work-more-abstract-untruncated hidden">Mo isotope data on Black Sea sediments spanning the transition from Pleistocene oxic-limnic conditions to the prevailing anoxic marine conditions are presented. Samples were taken from a gravity core collected at a water depth of 396 m. Samples deposited under oxic bottom water conditions range from d 98/95 Mo MOMO À2.2x to À1.95x (MOMO = Mean Ocean Molybdenum) while samples deposited under anoxic bottom water conditions range from d 98/95 Mo MOMO À 1x to À 0.54x. The change of sedimentary environment is also recorded in the Mo contents increasing from oxic to anoxic sediments. The Mo isotopic composition and invariably low Mo content of the oxic sediments deposited under oxic bottom water conditions are compatible with a pure detrital origin of the Mo, irrespective of whether the deposits are of limnic or brackish origin. Mo content and isotopic compositions are identical above and below a sulfidisation front, which originates from the diffusion of sulfur species and in-situ microbial activity after establishment of brackish bottom water conditions. Further, no signal of the overlaying sapropels is seen in the underlying sediments. Thus, transport of sulfur species has not mobilised Mo during diagenesis.</span></div><div class="wp-workCard_item wp-workCard--actions"><span class="work-strip-bookmark-button-container"></span><a id="9505ec0f4de00191c16005062ba9f5f4" class="wp-workCard--action" rel="nofollow" data-click-track="profile-work-strip-download" data-download="{"attachment_id":6880347,"asset_id":1117221,"asset_type":"Work","button_location":"profile"}" href="https://www.academia.edu/attachments/6880347/download_file?s=profile"><span><i class="fa fa-arrow-down"></i></span><span>Download</span></a><span class="wp-workCard--action visible-if-viewed-by-owner inline-block" style="display: none;"><span class="js-profile-work-strip-edit-button-wrapper profile-work-strip-edit-button-wrapper" data-work-id="1117221"><a class="js-profile-work-strip-edit-button" tabindex="0"><span><i class="fa fa-pencil"></i></span><span>Edit</span></a></span></span></div><div class="wp-workCard_item wp-workCard--stats"><span><span><span class="js-view-count view-count u-mr2x" data-work-id="1117221"><i class="fa fa-spinner fa-spin"></i></span><script>$(function () { var workId = 1117221; 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$(this).data('initialized', true); } }); $a.trackClickSource(".js-work-strip-work-link", "profile_work_strip") }); </script> <div class="js-work-strip profile--work_container" data-work-id="1117219"><div class="profile--work_thumbnail hidden-xs"><a class="js-work-strip-work-link" data-click-track="profile-work-strip-thumbnail" href="https://www.academia.edu/1117219/Oceanic_molybdenum_isotope_fractionation_Diagenesis_and_hydrothermal_ridge_flank_alteration"><img alt="Research paper thumbnail of Oceanic molybdenum isotope fractionation: Diagenesis and hydrothermal ridge-flank alteration" class="work-thumbnail" src="https://attachments.academia-assets.com/6880333/thumbnails/1.jpg" /></a></div><div class="wp-workCard wp-workCard_itemContainer"><div class="wp-workCard_item wp-workCard--title"><a class="js-work-strip-work-link text-gray-darker" data-click-track="profile-work-strip-title" href="https://www.academia.edu/1117219/Oceanic_molybdenum_isotope_fractionation_Diagenesis_and_hydrothermal_ridge_flank_alteration">Oceanic molybdenum isotope fractionation: Diagenesis and hydrothermal ridge-flank alteration</a></div><div class="wp-workCard_item"><span class="js-work-more-abstract-truncated">1] Isotopic analyses of dissolved molybdenum are presented for sediment pore waters from a reduci...</span><a class="js-work-more-abstract" data-broccoli-component="work_strip.more_abstract" data-click-track="profile-work-strip-more-abstract" href="javascript:;"><span> more </span><span><i class="fa fa-caret-down"></i></span></a><span class="js-work-more-abstract-untruncated hidden">1] Isotopic analyses of dissolved molybdenum are presented for sediment pore waters from a reducing sedimentary basin and for fluids from a low-temperature ridge flank hydrothermal system. d 98/95 Mo in these fluids range from 0.8 to 3.5% (relative to a laboratory standard), demonstrating that marine sedimentary reactions significantly fractionate Mo isotopes. Within the upper 3 cm of sediment, manganese oxide dissolution produces an isotopically light fluid relative to seawater (mean of four analyses = 2.1 ± 0.1% versus seawater = 2.3 ± 0.1%). Below 6 cm depth, authigenic Mo uptake results in an isotopically heavier fluid (up to 3.5%) indicating that reducing sediments are likely to be a net sink for isotopically light dissolved Mo. In contrast, fluid circulation within a low-temperature ridge-flank hydrothermal system is a source of isotopically light Mo to the ocean having an end-member fluid of $0.8%.</span></div><div class="wp-workCard_item wp-workCard--actions"><span class="work-strip-bookmark-button-container"></span><a id="654fdbc7d59aa4810785a0d4d093eecd" class="wp-workCard--action" rel="nofollow" data-click-track="profile-work-strip-download" data-download="{"attachment_id":6880333,"asset_id":1117219,"asset_type":"Work","button_location":"profile"}" href="https://www.academia.edu/attachments/6880333/download_file?s=profile"><span><i class="fa fa-arrow-down"></i></span><span>Download</span></a><span class="wp-workCard--action visible-if-viewed-by-owner inline-block" style="display: none;"><span class="js-profile-work-strip-edit-button-wrapper profile-work-strip-edit-button-wrapper" data-work-id="1117219"><a class="js-profile-work-strip-edit-button" tabindex="0"><span><i class="fa fa-pencil"></i></span><span>Edit</span></a></span></span></div><div class="wp-workCard_item wp-workCard--stats"><span><span><span class="js-view-count view-count u-mr2x" data-work-id="1117219"><i class="fa fa-spinner fa-spin"></i></span><script>$(function () { var workId = 1117219; 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$(this).data('initialized', true); } }); $a.trackClickSource(".js-work-strip-work-link", "profile_work_strip") }); </script> <div class="js-work-strip profile--work_container" data-work-id="1117218"><div class="profile--work_thumbnail hidden-xs"><a class="js-work-strip-work-link" data-click-track="profile-work-strip-thumbnail" href="https://www.academia.edu/1117218/Molybdenum_isotope_signatures_in_continental_margin_marine_sediments"><img alt="Research paper thumbnail of Molybdenum isotope signatures in continental margin marine sediments" class="work-thumbnail" src="https://attachments.academia-assets.com/6880316/thumbnails/1.jpg" /></a></div><div class="wp-workCard wp-workCard_itemContainer"><div class="wp-workCard_item wp-workCard--title"><a class="js-work-strip-work-link text-gray-darker" data-click-track="profile-work-strip-title" href="https://www.academia.edu/1117218/Molybdenum_isotope_signatures_in_continental_margin_marine_sediments">Molybdenum isotope signatures in continental margin marine sediments</a></div><div class="wp-workCard_item"><span class="js-work-more-abstract-truncated">We present molybdenum isotope data for four sediment profiles from continental margin settings. E...</span><a class="js-work-more-abstract" data-broccoli-component="work_strip.more_abstract" data-click-track="profile-work-strip-more-abstract" href="javascript:;"><span> more </span><span><i class="fa fa-caret-down"></i></span></a><span class="js-work-more-abstract-untruncated hidden">We present molybdenum isotope data for four sediment profiles from continental margin settings. Each profile has a distinctive average isotope composition ranging from d 98 / 95 Mo À 0.5x to 1.3x (relative to J and M laboratory standard). This range lies between the modern ocean water value (2.3x) and the values typical of Mo adsorbed onto Mn oxides (À 0.7x F 0.1x). An important finding of this study is the apparent co-variation between the Mo isotope composition and the accumulation rate of authigenic Mo under reducing conditions. This relationship suggests that the chemical processes responsible for Mo accumulation under reducing conditions produce an isotope signature in marine sediments. In addition to the relationship between Mo accumulation and the Mo isotope signature there is also a relationship between these parameters and the rate of organic carbon oxidation and burial. These relationships suggest that the Mo isotope signature of reducing sediments may serve as a tracer for the cycling of organic carbon in continental margin sediments; however, additional data will be required to refine any such relationships.</span></div><div class="wp-workCard_item wp-workCard--actions"><span class="work-strip-bookmark-button-container"></span><a id="21273664f8951ebd17f64ada5528a841" class="wp-workCard--action" rel="nofollow" data-click-track="profile-work-strip-download" data-download="{"attachment_id":6880316,"asset_id":1117218,"asset_type":"Work","button_location":"profile"}" href="https://www.academia.edu/attachments/6880316/download_file?s=profile"><span><i class="fa fa-arrow-down"></i></span><span>Download</span></a><span class="wp-workCard--action visible-if-viewed-by-owner inline-block" style="display: none;"><span class="js-profile-work-strip-edit-button-wrapper profile-work-strip-edit-button-wrapper" data-work-id="1117218"><a class="js-profile-work-strip-edit-button" tabindex="0"><span><i class="fa fa-pencil"></i></span><span>Edit</span></a></span></span></div><div class="wp-workCard_item wp-workCard--stats"><span><span><span class="js-view-count view-count u-mr2x" data-work-id="1117218"><i class="fa fa-spinner fa-spin"></i></span><script>$(function () { var workId = 1117218; 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$(this).data('initialized', true); } }); $a.trackClickSource(".js-work-strip-work-link", "profile_work_strip") }); </script> <div class="js-work-strip profile--work_container" data-work-id="1117215"><div class="profile--work_thumbnail hidden-xs"><a class="js-work-strip-work-link" data-click-track="profile-work-strip-thumbnail" href="https://www.academia.edu/1117215/PGE_Re_Os_and_Molybdenum_isotope_systematicsin_Archean_and_early_Proterozoic_sedimentary_systems_as_proxies_for_redox_conditions_of_the_early_Earth"><img alt="Research paper thumbnail of PGE, Re-Os and Molybdenum isotope systematicsin Archean and early Proterozoic sedimentary systems as proxies for redox conditions of the early Earth" class="work-thumbnail" src="https://attachments.academia-assets.com/6880220/thumbnails/1.jpg" /></a></div><div class="wp-workCard wp-workCard_itemContainer"><div class="wp-workCard_item wp-workCard--title"><a class="js-work-strip-work-link text-gray-darker" data-click-track="profile-work-strip-title" href="https://www.academia.edu/1117215/PGE_Re_Os_and_Molybdenum_isotope_systematicsin_Archean_and_early_Proterozoic_sedimentary_systems_as_proxies_for_redox_conditions_of_the_early_Earth">PGE, Re-Os and Molybdenum isotope systematicsin Archean and early Proterozoic sedimentary systems as proxies for redox conditions of the early Earth</a></div><div class="wp-workCard_item"><span class="js-work-more-abstract-truncated">Re-Os data and PGE concentrations as well as Mo concentrations and isotope data are reported for ...</span><a class="js-work-more-abstract" data-broccoli-component="work_strip.more_abstract" data-click-track="profile-work-strip-more-abstract" href="javascript:;"><span> more </span><span><i class="fa fa-caret-down"></i></span></a><span class="js-work-more-abstract-untruncated hidden">Re-Os data and PGE concentrations as well as Mo concentrations and isotope data are reported for suites of fine clastic sediments and black shales from the Barberton Greenstone Belt, South Africa (Fig Tree and Moodies Groups, Ga), the Belingwe Greenstone Belt, Zimbabwe (Manjeri Formation, ca. 2.7 Ga) and shales from the Witwatersrand, Ventersdorp and Transvaal Supergroups, South Africa ranging from 2.95 to 2.2 Ga. Moderately oxidizing conditions are required to mobilize Re and Mo in the environment, Mo fractionation only occurs in solution, and these parameters thus have potential use as paleoredox proxies for the early Earth.</span></div><div class="wp-workCard_item wp-workCard--actions"><span class="work-strip-bookmark-button-container"></span><a id="b1f217887af743b31c5dfb3e1782182b" class="wp-workCard--action" rel="nofollow" data-click-track="profile-work-strip-download" data-download="{"attachment_id":6880220,"asset_id":1117215,"asset_type":"Work","button_location":"profile"}" href="https://www.academia.edu/attachments/6880220/download_file?s=profile"><span><i class="fa fa-arrow-down"></i></span><span>Download</span></a><span class="wp-workCard--action visible-if-viewed-by-owner inline-block" style="display: none;"><span class="js-profile-work-strip-edit-button-wrapper profile-work-strip-edit-button-wrapper" data-work-id="1117215"><a class="js-profile-work-strip-edit-button" tabindex="0"><span><i class="fa fa-pencil"></i></span><span>Edit</span></a></span></span></div><div class="wp-workCard_item wp-workCard--stats"><span><span><span class="js-view-count view-count u-mr2x" data-work-id="1117215"><i class="fa fa-spinner fa-spin"></i></span><script>$(function () { var workId = 1117215; 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$(this).data('initialized', true); } }); $a.trackClickSource(".js-work-strip-work-link", "profile_work_strip") }); </script> <div class="js-work-strip profile--work_container" data-work-id="1117200"><div class="profile--work_thumbnail hidden-xs"><a class="js-work-strip-work-link" data-click-track="profile-work-strip-thumbnail" href="https://www.academia.edu/1117200/Molybdenum_isotope_records_as_a_potential_new_proxy_for_paleoceanography"><img alt="Research paper thumbnail of Molybdenum isotope records as a potential new proxy for paleoceanography" class="work-thumbnail" src="https://attachments.academia-assets.com/6880174/thumbnails/1.jpg" /></a></div><div class="wp-workCard wp-workCard_itemContainer"><div class="wp-workCard_item wp-workCard--title"><a class="js-work-strip-work-link text-gray-darker" data-click-track="profile-work-strip-title" href="https://www.academia.edu/1117200/Molybdenum_isotope_records_as_a_potential_new_proxy_for_paleoceanography">Molybdenum isotope records as a potential new proxy for paleoceanography</a></div><div class="wp-workCard_item"><span class="js-work-more-abstract-truncated">New high-precision isotope ratios of dissolved Mo in seawater from different ocean basins and dep...</span><a class="js-work-more-abstract" data-broccoli-component="work_strip.more_abstract" data-click-track="profile-work-strip-more-abstract" href="javascript:;"><span> more </span><span><i class="fa fa-caret-down"></i></span></a><span class="js-work-more-abstract-untruncated hidden">New high-precision isotope ratios of dissolved Mo in seawater from different ocean basins and depths show a homogeneous isotope composition ('mean ocean water 98 Mo/ 95 Mo' (MOMO)), as expected from its long ocean residence time (800 kyr). This composition appears to have been constant for the past 60 Myr at a 1^3 Myr time resolution as indicated from thick sections of Fe^Mn crusts from the Atlantic and Pacific. These records yield a constant offset from MOMO (average of 33.1 and 32.9x). They are similar to our new data on recent oxic Mo sinks: pelagic sediments and six Fe^Mn crust surface layers range from 32.7 to 32.9x and 32.7 to 33.1x, respectively. Recent suboxic Mo sinks from open ocean basins display heavier and more variable isotope ratios (30.7 to 31.6x relative to MOMO). Crustal Mo sources were characterized by measuring two granites (and a mild acid leach of one granite), seven volcanic rocks and two clastic sediments. All show a narrow range of compositions (32.0 to 32.3x). These data indicate that isotope fractionation by chemical weathering and magmatic processes is insignificant on a global scale. They therefore represent good estimates of the composition of dissolved Mo input to the oceans and that of the average continental crust. Thus, the Mo input into the oceans appears to be distributed into lighter oxic sinks and heavier reducing sinks. This is consistent with steady-state conditions in the modern ocean. The constant isotope offset between oxic sediments and seawater suggests that the relative amounts of oxic and reducing Mo removal fluxes have not varied by more than 10% over the last 60 Myr. An equilibrium fractionation process is proposed assuming that Mo isotope fractionation occurs between (dominant) MoO 23 4 and (minor) Mo(OH) 6 species in solution, of which the latter is preferentially scavenged. ß</span></div><div class="wp-workCard_item wp-workCard--actions"><span class="work-strip-bookmark-button-container"></span><a id="491dac1799d64306b3b57903ed39dd2a" class="wp-workCard--action" rel="nofollow" data-click-track="profile-work-strip-download" data-download="{"attachment_id":6880174,"asset_id":1117200,"asset_type":"Work","button_location":"profile"}" href="https://www.academia.edu/attachments/6880174/download_file?s=profile"><span><i class="fa fa-arrow-down"></i></span><span>Download</span></a><span class="wp-workCard--action visible-if-viewed-by-owner inline-block" style="display: none;"><span class="js-profile-work-strip-edit-button-wrapper profile-work-strip-edit-button-wrapper" data-work-id="1117200"><a class="js-profile-work-strip-edit-button" tabindex="0"><span><i class="fa fa-pencil"></i></span><span>Edit</span></a></span></span></div><div class="wp-workCard_item wp-workCard--stats"><span><span><span class="js-view-count view-count u-mr2x" data-work-id="1117200"><i class="fa fa-spinner fa-spin"></i></span><script>$(function () { var workId = 1117200; 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$(this).data('initialized', true); } }); $a.trackClickSource(".js-work-strip-work-link", "profile_work_strip") }); </script> <div class="js-work-strip profile--work_container" data-work-id="1117192"><div class="profile--work_thumbnail hidden-xs"><a class="js-work-strip-work-link" data-click-track="profile-work-strip-thumbnail" href="https://www.academia.edu/1117192/Determination_of_Molybdenum_Isotope_Fractionation_by_Double_Spike_MC_ICP_MS"><img alt="Research paper thumbnail of Determination of Molybdenum Isotope Fractionation by Double Spike MC-ICP-MS" class="work-thumbnail" src="https://attachments.academia-assets.com/6880150/thumbnails/1.jpg" /></a></div><div class="wp-workCard wp-workCard_itemContainer"><div class="wp-workCard_item wp-workCard--title"><a class="js-work-strip-work-link text-gray-darker" data-click-track="profile-work-strip-title" href="https://www.academia.edu/1117192/Determination_of_Molybdenum_Isotope_Fractionation_by_Double_Spike_MC_ICP_MS">Determination of Molybdenum Isotope Fractionation by Double Spike MC-ICP-MS</a></div><div class="wp-workCard_item"><span class="js-work-more-abstract-truncated">1] Abstract: Molybdenum isotopic compositions are precisely determined by MC-ICP-MS measurements ...</span><a class="js-work-more-abstract" data-broccoli-component="work_strip.more_abstract" data-click-track="profile-work-strip-more-abstract" href="javascript:;"><span> more </span><span><i class="fa fa-caret-down"></i></span></a><span class="js-work-more-abstract-untruncated hidden">1] Abstract: Molybdenum isotopic compositions are precisely determined by MC-ICP-MS measurements using a Mo double spike. The double spike is added prior to chemical purification, so that laboratory and instrumental mass fractionations are separated from natural mass-dependent fractionation. Fractionation is determined on four Mo mass ratios, providing an internal consistency check. The external standard reproducibility is at 0.06 per mil on the 98 Mo/ 95 Mo ratio (2 standard deviation)). Using a normal microconcentric nebuliser with a cyclonic spray chamber, the minimum quantity of Mo is $1 mg for high-precision results. A hydrothermal molybdenite shows fractionation of À0.3 per mil on the 98 Mo/ 95 Mo ratio relative to our standard (Johnson Matthey, 1000 mg/mL (0.3%) ICP standard solution, lot 602332B). Fine-grained sediments show fractionation of 0.1 and À0.3 per mil on the 98 Mo/ 95 Mo ratio. The observed Mo isotope fractionation is small but resolvable with the presented high-resolution technique. , 2001. Determination of molybdenum isotope fractionation by doublespike multicollector inductively coupled plasma mass spectrometry,</span></div><div class="wp-workCard_item wp-workCard--actions"><span class="work-strip-bookmark-button-container"></span><a id="ef1a79e50a78a9036748f068022d4434" class="wp-workCard--action" rel="nofollow" data-click-track="profile-work-strip-download" data-download="{"attachment_id":6880150,"asset_id":1117192,"asset_type":"Work","button_location":"profile"}" href="https://www.academia.edu/attachments/6880150/download_file?s=profile"><span><i class="fa fa-arrow-down"></i></span><span>Download</span></a><span class="wp-workCard--action visible-if-viewed-by-owner inline-block" style="display: none;"><span class="js-profile-work-strip-edit-button-wrapper profile-work-strip-edit-button-wrapper" data-work-id="1117192"><a class="js-profile-work-strip-edit-button" tabindex="0"><span><i class="fa fa-pencil"></i></span><span>Edit</span></a></span></span></div><div class="wp-workCard_item wp-workCard--stats"><span><span><span class="js-view-count view-count u-mr2x" data-work-id="1117192"><i class="fa fa-spinner fa-spin"></i></span><script>$(function () { var workId = 1117192; 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$(this).data('initialized', true); } }); $a.trackClickSource(".js-work-strip-work-link", "profile_work_strip") }); </script> </div><div class="profile--tab_content_container js-tab-pane tab-pane" data-section-id="140048" id="papers"><div class="js-work-strip profile--work_container" data-work-id="1117227"><div class="profile--work_thumbnail hidden-xs"><a class="js-work-strip-work-link" data-click-track="profile-work-strip-thumbnail" href="https://www.academia.edu/1117227/Quantifying_the_impact_of_freshwater_diatom_productivity_on_silicon_isotopes_and_silicon_fluxes_Lake_Myvatn_Iceland"><img alt="Research paper thumbnail of Quantifying the impact of freshwater diatom productivity on silicon isotopes and silicon fluxes: Lake Myvatn, Iceland" class="work-thumbnail" src="https://attachments.academia-assets.com/6880366/thumbnails/1.jpg" /></a></div><div class="wp-workCard wp-workCard_itemContainer"><div class="wp-workCard_item wp-workCard--title"><a class="js-work-strip-work-link text-gray-darker" data-click-track="profile-work-strip-title" href="https://www.academia.edu/1117227/Quantifying_the_impact_of_freshwater_diatom_productivity_on_silicon_isotopes_and_silicon_fluxes_Lake_Myvatn_Iceland">Quantifying the impact of freshwater diatom productivity on silicon isotopes and silicon fluxes: Lake Myvatn, Iceland</a></div><div class="wp-workCard_item"><span class="js-work-more-abstract-truncated">Keywords: silicon isotopes diatom biogenic Si dissolution groundwater Lake Myvatn Iceland Diatom ...</span><a class="js-work-more-abstract" data-broccoli-component="work_strip.more_abstract" data-click-track="profile-work-strip-more-abstract" href="javascript:;"><span> more </span><span><i class="fa fa-caret-down"></i></span></a><span class="js-work-more-abstract-untruncated hidden">Keywords: silicon isotopes diatom biogenic Si dissolution groundwater Lake Myvatn Iceland Diatom productivity in the oceans plays a crucial role in the carbon cycle, but is strongly dependent upon the continental silicon supply. However, the relative influence of weathering and biological processes on continental Si fluxes remains poorly constrained. This study aims to quantify the impact of terrestrial diatom productivity on Si fluxes to the ocean. Lake Myvatn in North Iceland is one of the most productive lakes in the Northern Hemisphere, with nutrient-rich waters almost uniquely sourced by groundwater. The primary production is mainly controlled by diatom growth but also by cyanobacteria, and the lake output is via a single river, thereby providing a relatively simple natural laboratory to quantify the impact of diatom growth on the chemistry and Si budget of lake waters. Silicon stable isotopes (δ 30 Si) provide a tracer of this biocycling, and have been measured in groundwater inputs to the lake, and in time-series monitoring of waters at the lake outlet. The δ 30 Si values at the outlet range from + 0.70 ± 0.08 to + 1.42 ± 0.06‰, which is significantly heavier than the groundwater input (average cold and hot springs: + 0.50 ± 0.17‰, 2SD) and consistent with the preferential uptake of light Si isotopes by diatoms. The δ 30 Si value at the outlet increases by up to 0.9‰ in spring and autumn relative to the Si isotope composition of the inflow. These seasonal diatom blooms can be modeled by an open system of Si uptake and affect Si fluxes at the outlet of the lake by up to 79%, or 53% integrated over the year. In the summer a shift to lighter δ 30 Si values is correlated with a higher pH, which results in dissolution of diatoms releasing light Si isotopes. From mass balance, this seasonal diatom dissolution affects Si fluxes by up to 33%, but is limited to 3.7% integrated over the year. These results clearly illustrate that biological activity can have a significant impact on both isotope composition and elemental abundance of continental derived Si. They also demonstrate the pH dependency of diatom dissolution and/or preservation, which is likely to affect not only the continental Si fluxes to the ocean but also the Si recycling in the oceans themselves.</span></div><div class="wp-workCard_item wp-workCard--actions"><span class="work-strip-bookmark-button-container"></span><a id="3a14ea6692b70fd06bb5cf6aa7ddfb80" class="wp-workCard--action" rel="nofollow" data-click-track="profile-work-strip-download" data-download="{"attachment_id":6880366,"asset_id":1117227,"asset_type":"Work","button_location":"profile"}" href="https://www.academia.edu/attachments/6880366/download_file?s=profile"><span><i class="fa fa-arrow-down"></i></span><span>Download</span></a><span class="wp-workCard--action visible-if-viewed-by-owner inline-block" style="display: none;"><span class="js-profile-work-strip-edit-button-wrapper profile-work-strip-edit-button-wrapper" data-work-id="1117227"><a class="js-profile-work-strip-edit-button" tabindex="0"><span><i class="fa fa-pencil"></i></span><span>Edit</span></a></span></span></div><div class="wp-workCard_item wp-workCard--stats"><span><span><span class="js-view-count view-count u-mr2x" data-work-id="1117227"><i class="fa fa-spinner fa-spin"></i></span><script>$(function () { var workId = 1117227; 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$(this).data('initialized', true); } }); $a.trackClickSource(".js-work-strip-work-link", "profile_work_strip") }); </script> <div class="js-work-strip profile--work_container" data-work-id="1117221"><div class="profile--work_thumbnail hidden-xs"><a class="js-work-strip-work-link" data-click-track="profile-work-strip-thumbnail" href="https://www.academia.edu/1117221/Sedimentary_Mo_isotope_record_across_the_Holocene_fresh_brackish_water_transition_of_the_Black_Sea"><img alt="Research paper thumbnail of Sedimentary Mo isotope record across the Holocene fresh–brackish water transition of the Black Sea" class="work-thumbnail" src="https://attachments.academia-assets.com/6880347/thumbnails/1.jpg" /></a></div><div class="wp-workCard wp-workCard_itemContainer"><div class="wp-workCard_item wp-workCard--title"><a class="js-work-strip-work-link text-gray-darker" data-click-track="profile-work-strip-title" href="https://www.academia.edu/1117221/Sedimentary_Mo_isotope_record_across_the_Holocene_fresh_brackish_water_transition_of_the_Black_Sea">Sedimentary Mo isotope record across the Holocene fresh–brackish water transition of the Black Sea</a></div><div class="wp-workCard_item"><span class="js-work-more-abstract-truncated">Mo isotope data on Black Sea sediments spanning the transition from Pleistocene oxic-limnic condi...</span><a class="js-work-more-abstract" data-broccoli-component="work_strip.more_abstract" data-click-track="profile-work-strip-more-abstract" href="javascript:;"><span> more </span><span><i class="fa fa-caret-down"></i></span></a><span class="js-work-more-abstract-untruncated hidden">Mo isotope data on Black Sea sediments spanning the transition from Pleistocene oxic-limnic conditions to the prevailing anoxic marine conditions are presented. Samples were taken from a gravity core collected at a water depth of 396 m. Samples deposited under oxic bottom water conditions range from d 98/95 Mo MOMO À2.2x to À1.95x (MOMO = Mean Ocean Molybdenum) while samples deposited under anoxic bottom water conditions range from d 98/95 Mo MOMO À 1x to À 0.54x. The change of sedimentary environment is also recorded in the Mo contents increasing from oxic to anoxic sediments. The Mo isotopic composition and invariably low Mo content of the oxic sediments deposited under oxic bottom water conditions are compatible with a pure detrital origin of the Mo, irrespective of whether the deposits are of limnic or brackish origin. Mo content and isotopic compositions are identical above and below a sulfidisation front, which originates from the diffusion of sulfur species and in-situ microbial activity after establishment of brackish bottom water conditions. Further, no signal of the overlaying sapropels is seen in the underlying sediments. Thus, transport of sulfur species has not mobilised Mo during diagenesis.</span></div><div class="wp-workCard_item wp-workCard--actions"><span class="work-strip-bookmark-button-container"></span><a id="9505ec0f4de00191c16005062ba9f5f4" class="wp-workCard--action" rel="nofollow" data-click-track="profile-work-strip-download" data-download="{"attachment_id":6880347,"asset_id":1117221,"asset_type":"Work","button_location":"profile"}" href="https://www.academia.edu/attachments/6880347/download_file?s=profile"><span><i class="fa fa-arrow-down"></i></span><span>Download</span></a><span class="wp-workCard--action visible-if-viewed-by-owner inline-block" style="display: none;"><span class="js-profile-work-strip-edit-button-wrapper profile-work-strip-edit-button-wrapper" data-work-id="1117221"><a class="js-profile-work-strip-edit-button" tabindex="0"><span><i class="fa fa-pencil"></i></span><span>Edit</span></a></span></span></div><div class="wp-workCard_item wp-workCard--stats"><span><span><span class="js-view-count view-count u-mr2x" data-work-id="1117221"><i class="fa fa-spinner fa-spin"></i></span><script>$(function () { var workId = 1117221; 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$(this).data('initialized', true); } }); $a.trackClickSource(".js-work-strip-work-link", "profile_work_strip") }); </script> <div class="js-work-strip profile--work_container" data-work-id="1117219"><div class="profile--work_thumbnail hidden-xs"><a class="js-work-strip-work-link" data-click-track="profile-work-strip-thumbnail" href="https://www.academia.edu/1117219/Oceanic_molybdenum_isotope_fractionation_Diagenesis_and_hydrothermal_ridge_flank_alteration"><img alt="Research paper thumbnail of Oceanic molybdenum isotope fractionation: Diagenesis and hydrothermal ridge-flank alteration" class="work-thumbnail" src="https://attachments.academia-assets.com/6880333/thumbnails/1.jpg" /></a></div><div class="wp-workCard wp-workCard_itemContainer"><div class="wp-workCard_item wp-workCard--title"><a class="js-work-strip-work-link text-gray-darker" data-click-track="profile-work-strip-title" href="https://www.academia.edu/1117219/Oceanic_molybdenum_isotope_fractionation_Diagenesis_and_hydrothermal_ridge_flank_alteration">Oceanic molybdenum isotope fractionation: Diagenesis and hydrothermal ridge-flank alteration</a></div><div class="wp-workCard_item"><span class="js-work-more-abstract-truncated">1] Isotopic analyses of dissolved molybdenum are presented for sediment pore waters from a reduci...</span><a class="js-work-more-abstract" data-broccoli-component="work_strip.more_abstract" data-click-track="profile-work-strip-more-abstract" href="javascript:;"><span> more </span><span><i class="fa fa-caret-down"></i></span></a><span class="js-work-more-abstract-untruncated hidden">1] Isotopic analyses of dissolved molybdenum are presented for sediment pore waters from a reducing sedimentary basin and for fluids from a low-temperature ridge flank hydrothermal system. d 98/95 Mo in these fluids range from 0.8 to 3.5% (relative to a laboratory standard), demonstrating that marine sedimentary reactions significantly fractionate Mo isotopes. Within the upper 3 cm of sediment, manganese oxide dissolution produces an isotopically light fluid relative to seawater (mean of four analyses = 2.1 ± 0.1% versus seawater = 2.3 ± 0.1%). Below 6 cm depth, authigenic Mo uptake results in an isotopically heavier fluid (up to 3.5%) indicating that reducing sediments are likely to be a net sink for isotopically light dissolved Mo. In contrast, fluid circulation within a low-temperature ridge-flank hydrothermal system is a source of isotopically light Mo to the ocean having an end-member fluid of $0.8%.</span></div><div class="wp-workCard_item wp-workCard--actions"><span class="work-strip-bookmark-button-container"></span><a id="654fdbc7d59aa4810785a0d4d093eecd" class="wp-workCard--action" rel="nofollow" data-click-track="profile-work-strip-download" data-download="{"attachment_id":6880333,"asset_id":1117219,"asset_type":"Work","button_location":"profile"}" href="https://www.academia.edu/attachments/6880333/download_file?s=profile"><span><i class="fa fa-arrow-down"></i></span><span>Download</span></a><span class="wp-workCard--action visible-if-viewed-by-owner inline-block" style="display: none;"><span class="js-profile-work-strip-edit-button-wrapper profile-work-strip-edit-button-wrapper" data-work-id="1117219"><a class="js-profile-work-strip-edit-button" tabindex="0"><span><i class="fa fa-pencil"></i></span><span>Edit</span></a></span></span></div><div class="wp-workCard_item wp-workCard--stats"><span><span><span class="js-view-count view-count u-mr2x" data-work-id="1117219"><i class="fa fa-spinner fa-spin"></i></span><script>$(function () { var workId = 1117219; 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dispatcherData = { dispatcher: window.WowProfile.dispatcher, downloadLinkId: "654fdbc7d59aa4810785a0d4d093eecd" } } $('.js-work-strip[data-work-id=1117219]').each(function() { if (!$(this).data('initialized')) { new WowProfile.WorkStripView({ el: this, workJSON: {"id":1117219,"title":"Oceanic molybdenum isotope fractionation: Diagenesis and hydrothermal ridge-flank alteration","internal_url":"https://www.academia.edu/1117219/Oceanic_molybdenum_isotope_fractionation_Diagenesis_and_hydrothermal_ridge_flank_alteration","owner_id":327766,"coauthors_can_edit":true,"owner":{"id":327766,"first_name":"Chris","middle_initials":null,"last_name":"Siebert","page_name":"ChrisSiebert","domain_name":"oxford","created_at":"2011-02-09T20:10:08.626-08:00","display_name":"Chris Siebert","url":"https://oxford.academia.edu/ChrisSiebert"},"attachments":[{"id":6880333,"title":"","file_type":"pdf","scribd_thumbnail_url":"https://attachments.academia-assets.com/6880333/thumbnails/1.jpg","file_name":"McManus2002.pdf","download_url":"https://www.academia.edu/attachments/6880333/download_file","bulk_download_file_name":"Oceanic_molybdenum_isotope_fractionation.pdf","bulk_download_url":"https://d1wqtxts1xzle7.cloudfront.net/6880333/McManus2002-libre.pdf?1390848530=\u0026response-content-disposition=attachment%3B+filename%3DOceanic_molybdenum_isotope_fractionation.pdf\u0026Expires=1740534097\u0026Signature=gfZ00N8oSdExet0~67dsS6-AMymTw8YwZQK1xFKpVfc2iR0IORTgIQzYPkiIKUqf7Msh7JCUz4BZuLDcoqHRCMw8An5FrRZpyybHYDp63RLcHUNNvzqiP5IQfJpUhaOj9C2GszpRYTAuLjSOCoC6jCPWDPqdePTaFArSjJDcZTgvRAzqwbgypwR8pmUidCmvAJ0qaYbmw4EMzdpIKT5JSgR0k3cBSZZLood0O8j~A7WKMlzVD7NMPddd3ayPTWMj1Zr~Mpxriopz5jZeBi2utQsRzfqD2wSy5zMojLonyYwi2fu0Y9CaNC0MERavYksXGvdZdZCdDBtsAtpfC-jwRw__\u0026Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA"}]}, dispatcherData: dispatcherData }); $(this).data('initialized', true); } }); $a.trackClickSource(".js-work-strip-work-link", "profile_work_strip") }); </script> <div class="js-work-strip profile--work_container" data-work-id="1117218"><div class="profile--work_thumbnail hidden-xs"><a class="js-work-strip-work-link" data-click-track="profile-work-strip-thumbnail" href="https://www.academia.edu/1117218/Molybdenum_isotope_signatures_in_continental_margin_marine_sediments"><img alt="Research paper thumbnail of Molybdenum isotope signatures in continental margin marine sediments" class="work-thumbnail" src="https://attachments.academia-assets.com/6880316/thumbnails/1.jpg" /></a></div><div class="wp-workCard wp-workCard_itemContainer"><div class="wp-workCard_item wp-workCard--title"><a class="js-work-strip-work-link text-gray-darker" data-click-track="profile-work-strip-title" href="https://www.academia.edu/1117218/Molybdenum_isotope_signatures_in_continental_margin_marine_sediments">Molybdenum isotope signatures in continental margin marine sediments</a></div><div class="wp-workCard_item"><span class="js-work-more-abstract-truncated">We present molybdenum isotope data for four sediment profiles from continental margin settings. E...</span><a class="js-work-more-abstract" data-broccoli-component="work_strip.more_abstract" data-click-track="profile-work-strip-more-abstract" href="javascript:;"><span> more </span><span><i class="fa fa-caret-down"></i></span></a><span class="js-work-more-abstract-untruncated hidden">We present molybdenum isotope data for four sediment profiles from continental margin settings. Each profile has a distinctive average isotope composition ranging from d 98 / 95 Mo À 0.5x to 1.3x (relative to J and M laboratory standard). This range lies between the modern ocean water value (2.3x) and the values typical of Mo adsorbed onto Mn oxides (À 0.7x F 0.1x). An important finding of this study is the apparent co-variation between the Mo isotope composition and the accumulation rate of authigenic Mo under reducing conditions. This relationship suggests that the chemical processes responsible for Mo accumulation under reducing conditions produce an isotope signature in marine sediments. In addition to the relationship between Mo accumulation and the Mo isotope signature there is also a relationship between these parameters and the rate of organic carbon oxidation and burial. These relationships suggest that the Mo isotope signature of reducing sediments may serve as a tracer for the cycling of organic carbon in continental margin sediments; however, additional data will be required to refine any such relationships.</span></div><div class="wp-workCard_item wp-workCard--actions"><span class="work-strip-bookmark-button-container"></span><a id="21273664f8951ebd17f64ada5528a841" class="wp-workCard--action" rel="nofollow" data-click-track="profile-work-strip-download" data-download="{"attachment_id":6880316,"asset_id":1117218,"asset_type":"Work","button_location":"profile"}" href="https://www.academia.edu/attachments/6880316/download_file?s=profile"><span><i class="fa fa-arrow-down"></i></span><span>Download</span></a><span class="wp-workCard--action visible-if-viewed-by-owner inline-block" style="display: none;"><span class="js-profile-work-strip-edit-button-wrapper profile-work-strip-edit-button-wrapper" data-work-id="1117218"><a class="js-profile-work-strip-edit-button" tabindex="0"><span><i class="fa fa-pencil"></i></span><span>Edit</span></a></span></span></div><div class="wp-workCard_item wp-workCard--stats"><span><span><span class="js-view-count view-count u-mr2x" data-work-id="1117218"><i class="fa fa-spinner fa-spin"></i></span><script>$(function () { var workId = 1117218; 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dispatcherData = { dispatcher: window.WowProfile.dispatcher, downloadLinkId: "21273664f8951ebd17f64ada5528a841" } } $('.js-work-strip[data-work-id=1117218]').each(function() { if (!$(this).data('initialized')) { new WowProfile.WorkStripView({ el: this, workJSON: {"id":1117218,"title":"Molybdenum isotope signatures in continental margin marine sediments","internal_url":"https://www.academia.edu/1117218/Molybdenum_isotope_signatures_in_continental_margin_marine_sediments","owner_id":327766,"coauthors_can_edit":true,"owner":{"id":327766,"first_name":"Chris","middle_initials":null,"last_name":"Siebert","page_name":"ChrisSiebert","domain_name":"oxford","created_at":"2011-02-09T20:10:08.626-08:00","display_name":"Chris Siebert","url":"https://oxford.academia.edu/ChrisSiebert"},"attachments":[{"id":6880316,"title":"","file_type":"pdf","scribd_thumbnail_url":"https://attachments.academia-assets.com/6880316/thumbnails/1.jpg","file_name":"Siebertetal2006.pdf","download_url":"https://www.academia.edu/attachments/6880316/download_file","bulk_download_file_name":"Molybdenum_isotope_signatures_in_contine.pdf","bulk_download_url":"https://d1wqtxts1xzle7.cloudfront.net/6880316/Siebertetal2006-libre.pdf?1390848522=\u0026response-content-disposition=attachment%3B+filename%3DMolybdenum_isotope_signatures_in_contine.pdf\u0026Expires=1740534097\u0026Signature=CjxSI~ghQOMG52tYZ0UyAZL6uAO9Akot49IdeXWpNt7yLCR6c9b4GvwAibwEwm7TbChFxuZrdWGOdpUf7~iQAYej-YwvKLX0efaU-A~DKAh2H24wyJH6EnYxnKqKwSRNp6fgP5oU1wwtYejv5Scwj347WaCgxCHtRfYBuznM30Xn5XbFhY2Ef7QnHzGRWMhyxwgD8-suMuNH96XbZlRN-yXolyL6KvRs7E7hgTPhTbEW-kx2VPG9QIcBsTpzdFYIpS9UL7ff9XyHzwOl4SRmDwTGalQb8c1zDAI7lyS0Y6BzskO1boWRZQOrEbpnXu6OhW5ea90XBZ9SzbBRNMZqVA__\u0026Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA"}]}, dispatcherData: dispatcherData }); $(this).data('initialized', true); } }); $a.trackClickSource(".js-work-strip-work-link", "profile_work_strip") }); </script> <div class="js-work-strip profile--work_container" data-work-id="1117215"><div class="profile--work_thumbnail hidden-xs"><a class="js-work-strip-work-link" data-click-track="profile-work-strip-thumbnail" href="https://www.academia.edu/1117215/PGE_Re_Os_and_Molybdenum_isotope_systematicsin_Archean_and_early_Proterozoic_sedimentary_systems_as_proxies_for_redox_conditions_of_the_early_Earth"><img alt="Research paper thumbnail of PGE, Re-Os and Molybdenum isotope systematicsin Archean and early Proterozoic sedimentary systems as proxies for redox conditions of the early Earth" class="work-thumbnail" src="https://attachments.academia-assets.com/6880220/thumbnails/1.jpg" /></a></div><div class="wp-workCard wp-workCard_itemContainer"><div class="wp-workCard_item wp-workCard--title"><a class="js-work-strip-work-link text-gray-darker" data-click-track="profile-work-strip-title" href="https://www.academia.edu/1117215/PGE_Re_Os_and_Molybdenum_isotope_systematicsin_Archean_and_early_Proterozoic_sedimentary_systems_as_proxies_for_redox_conditions_of_the_early_Earth">PGE, Re-Os and Molybdenum isotope systematicsin Archean and early Proterozoic sedimentary systems as proxies for redox conditions of the early Earth</a></div><div class="wp-workCard_item"><span class="js-work-more-abstract-truncated">Re-Os data and PGE concentrations as well as Mo concentrations and isotope data are reported for ...</span><a class="js-work-more-abstract" data-broccoli-component="work_strip.more_abstract" data-click-track="profile-work-strip-more-abstract" href="javascript:;"><span> more </span><span><i class="fa fa-caret-down"></i></span></a><span class="js-work-more-abstract-untruncated hidden">Re-Os data and PGE concentrations as well as Mo concentrations and isotope data are reported for suites of fine clastic sediments and black shales from the Barberton Greenstone Belt, South Africa (Fig Tree and Moodies Groups, Ga), the Belingwe Greenstone Belt, Zimbabwe (Manjeri Formation, ca. 2.7 Ga) and shales from the Witwatersrand, Ventersdorp and Transvaal Supergroups, South Africa ranging from 2.95 to 2.2 Ga. Moderately oxidizing conditions are required to mobilize Re and Mo in the environment, Mo fractionation only occurs in solution, and these parameters thus have potential use as paleoredox proxies for the early Earth.</span></div><div class="wp-workCard_item wp-workCard--actions"><span class="work-strip-bookmark-button-container"></span><a id="b1f217887af743b31c5dfb3e1782182b" class="wp-workCard--action" rel="nofollow" data-click-track="profile-work-strip-download" data-download="{"attachment_id":6880220,"asset_id":1117215,"asset_type":"Work","button_location":"profile"}" href="https://www.academia.edu/attachments/6880220/download_file?s=profile"><span><i class="fa fa-arrow-down"></i></span><span>Download</span></a><span class="wp-workCard--action visible-if-viewed-by-owner inline-block" style="display: none;"><span class="js-profile-work-strip-edit-button-wrapper profile-work-strip-edit-button-wrapper" data-work-id="1117215"><a class="js-profile-work-strip-edit-button" tabindex="0"><span><i class="fa fa-pencil"></i></span><span>Edit</span></a></span></span></div><div class="wp-workCard_item wp-workCard--stats"><span><span><span class="js-view-count view-count u-mr2x" data-work-id="1117215"><i class="fa fa-spinner fa-spin"></i></span><script>$(function () { var workId = 1117215; 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$(this).data('initialized', true); } }); $a.trackClickSource(".js-work-strip-work-link", "profile_work_strip") }); </script> <div class="js-work-strip profile--work_container" data-work-id="1117200"><div class="profile--work_thumbnail hidden-xs"><a class="js-work-strip-work-link" data-click-track="profile-work-strip-thumbnail" href="https://www.academia.edu/1117200/Molybdenum_isotope_records_as_a_potential_new_proxy_for_paleoceanography"><img alt="Research paper thumbnail of Molybdenum isotope records as a potential new proxy for paleoceanography" class="work-thumbnail" src="https://attachments.academia-assets.com/6880174/thumbnails/1.jpg" /></a></div><div class="wp-workCard wp-workCard_itemContainer"><div class="wp-workCard_item wp-workCard--title"><a class="js-work-strip-work-link text-gray-darker" data-click-track="profile-work-strip-title" href="https://www.academia.edu/1117200/Molybdenum_isotope_records_as_a_potential_new_proxy_for_paleoceanography">Molybdenum isotope records as a potential new proxy for paleoceanography</a></div><div class="wp-workCard_item"><span class="js-work-more-abstract-truncated">New high-precision isotope ratios of dissolved Mo in seawater from different ocean basins and dep...</span><a class="js-work-more-abstract" data-broccoli-component="work_strip.more_abstract" data-click-track="profile-work-strip-more-abstract" href="javascript:;"><span> more </span><span><i class="fa fa-caret-down"></i></span></a><span class="js-work-more-abstract-untruncated hidden">New high-precision isotope ratios of dissolved Mo in seawater from different ocean basins and depths show a homogeneous isotope composition ('mean ocean water 98 Mo/ 95 Mo' (MOMO)), as expected from its long ocean residence time (800 kyr). This composition appears to have been constant for the past 60 Myr at a 1^3 Myr time resolution as indicated from thick sections of Fe^Mn crusts from the Atlantic and Pacific. These records yield a constant offset from MOMO (average of 33.1 and 32.9x). They are similar to our new data on recent oxic Mo sinks: pelagic sediments and six Fe^Mn crust surface layers range from 32.7 to 32.9x and 32.7 to 33.1x, respectively. Recent suboxic Mo sinks from open ocean basins display heavier and more variable isotope ratios (30.7 to 31.6x relative to MOMO). Crustal Mo sources were characterized by measuring two granites (and a mild acid leach of one granite), seven volcanic rocks and two clastic sediments. All show a narrow range of compositions (32.0 to 32.3x). These data indicate that isotope fractionation by chemical weathering and magmatic processes is insignificant on a global scale. They therefore represent good estimates of the composition of dissolved Mo input to the oceans and that of the average continental crust. Thus, the Mo input into the oceans appears to be distributed into lighter oxic sinks and heavier reducing sinks. This is consistent with steady-state conditions in the modern ocean. The constant isotope offset between oxic sediments and seawater suggests that the relative amounts of oxic and reducing Mo removal fluxes have not varied by more than 10% over the last 60 Myr. An equilibrium fractionation process is proposed assuming that Mo isotope fractionation occurs between (dominant) MoO 23 4 and (minor) Mo(OH) 6 species in solution, of which the latter is preferentially scavenged. ß</span></div><div class="wp-workCard_item wp-workCard--actions"><span class="work-strip-bookmark-button-container"></span><a id="491dac1799d64306b3b57903ed39dd2a" class="wp-workCard--action" rel="nofollow" data-click-track="profile-work-strip-download" data-download="{"attachment_id":6880174,"asset_id":1117200,"asset_type":"Work","button_location":"profile"}" href="https://www.academia.edu/attachments/6880174/download_file?s=profile"><span><i class="fa fa-arrow-down"></i></span><span>Download</span></a><span class="wp-workCard--action visible-if-viewed-by-owner inline-block" style="display: none;"><span class="js-profile-work-strip-edit-button-wrapper profile-work-strip-edit-button-wrapper" data-work-id="1117200"><a class="js-profile-work-strip-edit-button" tabindex="0"><span><i class="fa fa-pencil"></i></span><span>Edit</span></a></span></span></div><div class="wp-workCard_item wp-workCard--stats"><span><span><span class="js-view-count view-count u-mr2x" data-work-id="1117200"><i class="fa fa-spinner fa-spin"></i></span><script>$(function () { var workId = 1117200; 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$(this).data('initialized', true); } }); $a.trackClickSource(".js-work-strip-work-link", "profile_work_strip") }); </script> <div class="js-work-strip profile--work_container" data-work-id="1117192"><div class="profile--work_thumbnail hidden-xs"><a class="js-work-strip-work-link" data-click-track="profile-work-strip-thumbnail" href="https://www.academia.edu/1117192/Determination_of_Molybdenum_Isotope_Fractionation_by_Double_Spike_MC_ICP_MS"><img alt="Research paper thumbnail of Determination of Molybdenum Isotope Fractionation by Double Spike MC-ICP-MS" class="work-thumbnail" src="https://attachments.academia-assets.com/6880150/thumbnails/1.jpg" /></a></div><div class="wp-workCard wp-workCard_itemContainer"><div class="wp-workCard_item wp-workCard--title"><a class="js-work-strip-work-link text-gray-darker" data-click-track="profile-work-strip-title" href="https://www.academia.edu/1117192/Determination_of_Molybdenum_Isotope_Fractionation_by_Double_Spike_MC_ICP_MS">Determination of Molybdenum Isotope Fractionation by Double Spike MC-ICP-MS</a></div><div class="wp-workCard_item"><span class="js-work-more-abstract-truncated">1] Abstract: Molybdenum isotopic compositions are precisely determined by MC-ICP-MS measurements ...</span><a class="js-work-more-abstract" data-broccoli-component="work_strip.more_abstract" data-click-track="profile-work-strip-more-abstract" href="javascript:;"><span> more </span><span><i class="fa fa-caret-down"></i></span></a><span class="js-work-more-abstract-untruncated hidden">1] Abstract: Molybdenum isotopic compositions are precisely determined by MC-ICP-MS measurements using a Mo double spike. The double spike is added prior to chemical purification, so that laboratory and instrumental mass fractionations are separated from natural mass-dependent fractionation. Fractionation is determined on four Mo mass ratios, providing an internal consistency check. The external standard reproducibility is at 0.06 per mil on the 98 Mo/ 95 Mo ratio (2 standard deviation)). Using a normal microconcentric nebuliser with a cyclonic spray chamber, the minimum quantity of Mo is $1 mg for high-precision results. A hydrothermal molybdenite shows fractionation of À0.3 per mil on the 98 Mo/ 95 Mo ratio relative to our standard (Johnson Matthey, 1000 mg/mL (0.3%) ICP standard solution, lot 602332B). Fine-grained sediments show fractionation of 0.1 and À0.3 per mil on the 98 Mo/ 95 Mo ratio. The observed Mo isotope fractionation is small but resolvable with the presented high-resolution technique. , 2001. Determination of molybdenum isotope fractionation by doublespike multicollector inductively coupled plasma mass spectrometry,</span></div><div class="wp-workCard_item wp-workCard--actions"><span class="work-strip-bookmark-button-container"></span><a id="ef1a79e50a78a9036748f068022d4434" class="wp-workCard--action" rel="nofollow" data-click-track="profile-work-strip-download" data-download="{"attachment_id":6880150,"asset_id":1117192,"asset_type":"Work","button_location":"profile"}" href="https://www.academia.edu/attachments/6880150/download_file?s=profile"><span><i class="fa fa-arrow-down"></i></span><span>Download</span></a><span class="wp-workCard--action visible-if-viewed-by-owner inline-block" style="display: none;"><span class="js-profile-work-strip-edit-button-wrapper profile-work-strip-edit-button-wrapper" data-work-id="1117192"><a class="js-profile-work-strip-edit-button" tabindex="0"><span><i class="fa fa-pencil"></i></span><span>Edit</span></a></span></span></div><div class="wp-workCard_item wp-workCard--stats"><span><span><span class="js-view-count view-count u-mr2x" data-work-id="1117192"><i class="fa fa-spinner fa-spin"></i></span><script>$(function () { var workId = 1117192; 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