<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
<div class="" style="word-wrap:break-word; line-break:after-white-space"><font face="Georgia" class="" style="font-size:14px">Dear all,</font>
<div class=""><font face="Georgia" class="" style="font-size:14px"><br class="">
</font></div>
<div class=""><font face="Georgia" class=""><span class="" style="font-size:14px">Dr. James Eguchi will be visiting us from Feb. 25th-26th. Dr. Eguchi is a candidate for the faculty search in "Solid Earth Processes in the Lithosphere (Metamorphic Petrology)".</span></font></div>
<div class=""><font face="Georgia" class="" style="font-size:14px"><br class="">
</font></div>
<div class="">
<div class=""><font face="Georgia" class="" style="font-size:14px">I am attaching the title and abstract of Dr. Eguchi's talk. The talk is scheduled at <b class="">3:30 PM
</b><span class="">on</span><b class=""> 25th February 2020</b> (Tuesday) at</font><span class="" style="font-size:14px; font-family:Georgia"> </span><b class="" style="font-size:14px; font-family:Georgia">EOA 1044</b><span class="" style="font-size:14px; font-family:Georgia">.</span></div>
<div class=""><font face="Georgia" class="" style="font-size:14px"><br class="">
</font></div>
<div class=""><font face="Georgia" class="" style="font-size:14px">I am also attaching candidate's CV for your reference. If you would like additional information, please feel free to contact me. Also, if you would like to meet the candidate, please let me
know of your availability. I will try to schedule a meeting.</font></div>
<div class=""><font face="Georgia" class="" style="font-size:14px"><br class="">
</font></div>
<div class=""><font face="Georgia" class="" style="font-size:14px">I hope you are able to attend the talk.</font></div>
<div class=""><br class="">
</div>
<div class=""><font face="Georgia" class="" style="font-size:14px"><span class=""><b class="">Title:</b></span><b class=""> </b></font><span class="" style="text-align:justify"><font face="Georgia" class="" style="font-size:14px">Linking Earth’s surface and
interior carbon cycles – Implications for the history of oxygen and carbon isotopes</font></span></div>
<div class=""><font face="Georgia" class="" style="font-size:14px"><br class="">
</font></div>
<div class=""><font face="Georgia" class="" style="font-size:14px"><b class="">Abstract:</b> </font><font face="Georgia" class="" style="font-size:14px"><span lang="EN-GB" class="" style="text-align:justify; text-indent:14.2pt">The geologic record suggests
that large oxidation events may be associated with large, positive C isotope excursions, with two of the most</span></font></div>
<div class=""><font face="Georgia" class="" style="font-size:14px"><span lang="EN-GB" class="" style="text-align:justify; text-indent:14.2pt">notable examples occurring at the beginning and end of the Proterozoic. One way to explain the association of O<sub class="">2</sub> accumulation
and positive C isotope</span></font></div>
<div class=""><font face="Georgia" class="" style="font-size:14px"><span lang="EN-GB" class="" style="text-align:justify; text-indent:14.2pt">excursions is an increase in the fraction of carbon buried as organic carbon relative to inorganic carbonate (<i class="">f</i><sub class="">org</sub>).
However, studies have suggested that</span></font></div>
<div class=""><font face="Georgia" class="" style="font-size:14px"><span lang="EN-GB" class="" style="text-align:justify; text-indent:14.2pt">the Great Oxidation event may have preceded its associated carbon isotope excursion (Lomagundi event) by tens of millions
of years, making it difficult</span></font></div>
<div class=""><font face="Georgia" class="" style="font-size:14px"><span lang="EN-GB" class="" style="text-align:justify; text-indent:14.2pt">to explain both events by increased <i class="">f</i><sub class="">org</sub>. For this reason, some researchers have
proposed mechanisms which decrease oxygen sinks as the ultimate driver</span></font></div>
<div class=""><font face="Georgia" class="" style="font-size:14px"><span lang="EN-GB" class="" style="text-align:justify; text-indent:14.2pt">of O<sub class="">2</sub> accumulation in Earth’s atmosphere, but it is unclear how decreased oxygen sinks would also
result in a positive </span><span lang="EN-GB" class="" style="text-align:justify; text-indent:14.2pt">δ</span><sup class="" style="text-align:justify; text-indent:14.2pt"><span lang="EN-GB" class="">13</span></sup><span lang="EN-GB" class="" style="text-align:justify; text-indent:14.2pt">C
excursion.</span></font></div>
<div class=""><span lang="EN-GB" class="" style="font-size:14px; font-family:Georgia; text-align:justify; text-indent:14.2pt"><span class="x_Apple-tab-span" style="white-space:pre"></span>Here, I will present a new model which considers how the cycling of carbonates
and graphitized organic carbon in the mantle affects the evolution of</span></div>
<div class=""><span lang="EN-GB" class="" style="font-size:14px; font-family:Georgia; text-align:justify; text-indent:14.2pt">atmospheric oxygen and the carbon isotope record of marine carbonates. The model assumes that increased volcanic CO<sub class="">2</sub> emissions
drive increased</span></div>
<div class=""><span lang="EN-GB" class="" style="font-size:14px; font-family:Georgia; text-align:justify; text-indent:14.2pt">burial and subduction of carbonates and organic C. When this process is coupled with preferential release of subducted carbonates at
arc volcanoes and deep recycling of graphitized organic carbon to ocean island volcanoes it can explain the association and enigmatic timing of the GOE and Lomagundi Event. Notably, this model does not rely on any changes to <i class="">f</i><sub class="">org</sub> to
change </span><span lang="EN-GB" class="" style="font-size:14px; font-family:Georgia; text-align:justify; text-indent:14.2pt">δ</span><sup class="" style="font-family:Georgia; text-align:justify; text-indent:14.2pt"><span lang="EN-GB" class="">13</span></sup><span lang="EN-GB" class="" style="font-size:14px; font-family:Georgia; text-align:justify; text-indent:14.2pt">C</span><sub class="" style="font-family:Georgia; text-align:justify; text-indent:14.2pt"><span lang="EN-GB" class="">carb. </span></sub><span lang="EN-GB" class="" style="font-size:14px; font-family:Georgia; text-align:justify; text-indent:14.2pt">The
model’s initial response to increased C subduction fluxes is</span><span lang="EN-GB" class="" style="font-size:14px; font-family:Georgia; text-align:justify; text-indent:14.2pt"> increased CO<sub class="">2</sub> emissions at arcs (carbonate-enriched, high </span><span lang="EN-GB" class="" style="font-size:14px; font-family:Georgia; text-align:justify; text-indent:14.2pt">δ</span><sup class="" style="font-family:Georgia; text-align:justify; text-indent:14.2pt"><span lang="EN-GB" class="">13</span></sup><span lang="EN-GB" class="" style="font-size:14px; font-family:Georgia; text-align:justify; text-indent:14.2pt">C),
shifting </span><span lang="EN-GB" class="" style="font-size:14px; font-family:Georgia; text-align:justify; text-indent:14.2pt">δ</span><sup class="" style="font-family:Georgia; text-align:justify; text-indent:14.2pt"><span lang="EN-GB" class="">13</span></sup><span lang="EN-GB" class="" style="font-size:14px; font-family:Georgia; text-align:justify; text-indent:14.2pt">C
of atmospheric volcanic CO<sub class="">2</sub> inputs to higher values. </span><span lang="EN-GB" class="" style="font-size:14px; font-family:Georgia; text-align:justify; text-indent:14.2pt">δ</span><sup class="" style="font-family:Georgia; text-align:justify; text-indent:14.2pt"><span lang="EN-GB" class="">13</span></sup><span lang="EN-GB" class="" style="font-size:14px; font-family:Georgia; text-align:justify; text-indent:14.2pt">C<sub class="">carb</sub> continues
to increase until the increased flux of subducted organic C is released at intra-plate ocean islands, returning global CO<sub class="">2</sub> emissions at different volcanic settings to their steady-state ratios, ending the </span><span lang="EN-GB" class="" style="font-size:14px; font-family:Georgia; text-align:justify; text-indent:14.2pt">δ</span><sup class="" style="font-family:Georgia; text-align:justify; text-indent:14.2pt"><span lang="EN-GB" class="">13</span></sup><span lang="EN-GB" class="" style="font-size:14px; font-family:Georgia; text-align:justify; text-indent:14.2pt">C
excursion. Increased CO<sub class="">2</sub> emissions in the model can be caused by major tectonic transitions such as a transition from stagnant/sluggish lid to plate tectonics. This contribution provides a link between Earth’s evolving tectonics, atmospheric
evolution, and the C isotope record.</span></div>
<div class=""><font face="Georgia" class="" style="font-size:14px"><br class="">
</font></div>
<div class=""><font face="Georgia" class="" style="font-size:14px">Thank you</font></div>
<div class=""><font face="Georgia" class="" style="font-size:14px">Mainak</font></div>
<div class=""><font face="Georgia" class="" style="font-size:14px"><br class="">
</font></div>
</div>
<div class="">
<div dir="auto" class="" style="word-wrap:break-word; line-break:after-white-space">
<div style="color:rgb(0,0,0); font-family:Helvetica; font-size:12px; font-style:normal; font-variant-caps:normal; font-weight:normal; letter-spacing:normal; text-align:start; text-indent:0px; text-transform:none; white-space:normal; word-spacing:0px; text-decoration:none">
</div>
</div>
</div>
</div>
<div class="" style="word-wrap:break-word; line-break:after-white-space">
<div class="">
<div dir="auto" class="" style="word-wrap:break-word; line-break:after-white-space">
<div style="color:rgb(0,0,0); font-family:Helvetica; font-size:12px; font-style:normal; font-variant-caps:normal; font-weight:normal; letter-spacing:normal; text-align:start; text-indent:0px; text-transform:none; white-space:normal; word-spacing:0px; text-decoration:none">
</div>
</div>
</div>
<br class="">
</div>
</body>
</html>