{"668651":{"#nid":"668651","#data":{"type":"event","title":"PhD Defense by Simin Zhao","body":[{"value":"\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003E\u003Cspan\u003E\u003Cstrong\u003ETITLE:\u003C\/strong\u003E Geochemical Constraints on the Formation of Authigenic Clay Minerals During Reverse Weathering\u003C\/span\u003E\u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003E\u003Cspan\u003E\u003Cstrong\u003ELocation: \u003C\/strong\u003EFord ES\u0026amp;T Building, Room L1114; \u003Cspan\u003E\u003Cspan\u003EOnline with \u003C\/span\u003E\u003C\/span\u003E\u003Cspan\u003E\u003Cspan\u003EMicrosoft\u003C\/span\u003E\u003C\/span\u003E \u003Ca href=\u0022https:\/\/teams.microsoft.com\/dl\/launcher\/launcher.html?url=%2F_%23%2Fl%2Fmeetup-join%2F19%3Ameeting_NDNjMzVkMGYtNzhhZS00ZTJiLTkyYTMtZTU0N2Y3YzM0ODYy%40thread.v2%2F0%3Fcontext%3D%257b%2522Tid%2522%253a%2522482198bb-ae7b-4b25-8b7a-6d7f32faa083%2522%252c%2522Oid%2522%253a%252250a0c604-71b2-47dc-8b25-5624bb3b5ce3%2522%257d%26anon%3Dtrue\u0026amp;type=meetup-join\u0026amp;deeplinkId=e6abd894-429b-424a-89dc-f7f20756f0ba\u0026amp;directDl=true\u0026amp;msLaunch=true\u0026amp;enableMobilePage=true\u0026amp;suppressPrompt=true\u0022\u003E\u003Cspan\u003E\u003Cspan\u003E\u003Cspan\u003ETeams Meeting\u003C\/span\u003E\u003C\/span\u003E\u003C\/span\u003E\u003C\/a\u003E\u003Cspan\u003E\u003Cspan\u003E (\u003C\/span\u003E\u003C\/span\u003E\u003Ca href=\u0022http:\/\/bitly.ws\/PrLV\u0022\u003E\u003Cspan\u003E\u003Cspan\u003E\u003Cspan\u003E\u003Cspan\u003Ehttp:\/\/bitly.ws\/PrLV\u003C\/span\u003E\u003C\/span\u003E\u003C\/span\u003E\u003C\/span\u003E\u003C\/a\u003E\u003Cspan\u003E\u003Cspan\u003E, \u003C\/span\u003E\u003C\/span\u003E\u003Cspan\u003E\u003Cspan\u003EMeeting ID:\u0026nbsp;295 412 478 941\u003C\/span\u003E\u003C\/span\u003E\u003Cspan\u003E; \u003Cspan\u003EPasscode:\u0026nbsp;Rgu7X5\u003C\/span\u003E\u003C\/span\u003E\u003Cspan\u003E\u003Cspan\u003E)\u003C\/span\u003E\u003C\/span\u003E\u003C\/span\u003E\u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003E\u003Cspan\u003E\u003Cstrong\u003ETime:\u003C\/strong\u003E \u003Cspan\u003E\u003Cspan\u003E9:00 AM-11:30 AM EST, \u003C\/span\u003E\u003C\/span\u003E\u003Cspan\u003E\u003Cspan\u003EA\u003Cspan\u003Eugust 18th, 2023\u003C\/span\u003E\u003C\/span\u003E\u003C\/span\u003E\u003C\/span\u003E\u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003E\u003Cspan\u003E\u003Cstrong\u003ECommittee members: \u003C\/strong\u003EDr. Yuanzhi Tang (Advisor), Dr. Martial Taillefert, Dr. Ellery Ingall, Dr. Chris Reinhard, Dr. Jeffrey Krause\u003C\/span\u003E\u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\r\n\r\n\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003E\u003Cspan\u003E\u003Cspan\u003E\u003Cstrong\u003EAbstract: \u003C\/strong\u003EThe formation of authigenic clay minerals from biogenic silica \u003Cspan\u003E(bSi) \u003C\/span\u003Ein marine sediments, termed reverse weathering (RW), \u003Cspan\u003Edescribes the formation of cation-rich aluminosilicate clay phases at the expense of bSi and detrital lithogenic minerals with concurrent sequestration of cations (e.g., Fe2+, Mg2+, and K+), consuming alkalinity and releasing CO2. The RW process \u003C\/span\u003Eacts as a globally significant sink for Si and other elements such as Fe. It is an important process for regulating ocean pH and atmospheric CO2 over geologic time scales.\u003Cspan\u003E However, the \u003C\/span\u003Eformation mechanism, kinetics, and phases of authigenic clay during RW has long puzzled the geochemical community and\u003Cspan\u003E much remains unknown, owing to the \u003C\/span\u003E\u003Cspan\u003Eintrinsic\u003C\/span\u003E\u003Cspan\u003E challenges to trace and characterize authigenic clay formation during RW. \u003C\/span\u003EThis dissertation develops a framework of understanding for authigenic clay formation in the RW process by s\u003Cspan\u003Eystematically investigating the potential geochemical triggers, identifying the product phases, and unrevealing the reaction rates and mechanisms under well-controlled laboratory conditions. \u003C\/span\u003EDissolved Fe2+ and Al were identified as triggers for authigenic clay formation from bSi. The formation mechanism was identified to occur through (1) dissolution of Fe and Al minerals and bSi for dissolved Fe2+, Al, and dissolved Si (DSi) inputs, and (2) reprecipitation of these species via homogeneous or heterogenous precipitation and transformation. Authigenic clay formation rates, mechanism, and steps were constrained by initial DSi concentration, dissolved Fe2+ and Al concentration, and the presence of substrates. \u003Cspan\u003EThe authigenic phase type and crystallinity are constrained by reactant type and concentration (e.g., solid Al mineral phase for sufficient Al supply or limited sporadic dissolved Al input spikes, dissolved \u003C\/span\u003EFe2+ \u003Cspan\u003Econcentration), the presence of substrates, and reaction time. The observed authigenic phase includes \u003C\/span\u003EFe-bearing mica, berthierine, chamosite, and Fe-Al layered double hydroxide, allophane-like Al-Si gel precursor phase, hisingerite-like Fe(II)-Si gel precursor phase, and Fe-smectite. The results shed light on authigenic clay formation during RW and provide bases to refine Earth system models and quantify the impacts of RW in regulating global biogeochemical cycles and sinks, CO2 dynamics, and global climate.\u003C\/span\u003E\u003C\/span\u003E\u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n","summary":"","format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003E\u003Cspan\u003E\u003Cspan\u003E\u003Cspan\u003EGeochemical Constraints on the Formation of Authigenic Clay Minerals During Reverse Weathering\u003C\/span\u003E\u003C\/span\u003E\u003C\/span\u003E\u003C\/p\u003E\r\n","format":"limited_html"}],"field_summary_sentence":[{"value":"Geochemical Constraints on the Formation of Authigenic Clay Minerals During Reverse Weathering"}],"uid":"27707","created_gmt":"2023-08-01 13:36:24","changed_gmt":"2023-08-01 13:36:24","author":"Tatianna Richardson","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2023-08-18T09:00:00-04:00","event_time_end":"2023-08-18T11:30:00-04:00","event_time_end_last":"2023-08-18T11:30:00-04:00","gmt_time_start":"2023-08-18 13:00:00","gmt_time_end":"2023-08-18 15:30:00","gmt_time_end_last":"2023-08-18 15:30:00","rrule":null,"timezone":"America\/New_York"},"location":"Ford ES\u0026T Building, Room L1114; Online with Microsoft Teams Meeting","extras":[],"groups":[{"id":"221981","name":"Graduate Studies"}],"categories":[],"keywords":[{"id":"100811","name":"Phd Defense"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[{"id":"1788","name":"Other\/Miscellaneous"}],"invited_audience":[{"id":"78771","name":"Public"}],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}