EAST TENNESSEE GEOLOGICAL SOCIETY

October 2024 Hybrid Meeting

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Monday, October 14, 2024
6:00 - 7:30 pm

Note: ETGS members will receive an email with info for logging into the meeting.
 

October Presentation

Pyrite Oxidation in Rocks: From Atomic Observation to Global Implications
 

By

Xin Gu
Geochemist
Oak Ridge National Laboratory (ORNL)


Abstract

Pyrite oxidation is a crucial reaction influencing geochemical cycles of iron, sulfur, carbon, and oxygen. To interpret pyrite oxidation throughout Earth's geologic history, we must first understand the current controls on its oxidation rate. We propose a model for pyrite oxidation across various scales: grain, clast, borehole, and watershed. At the atomic scale, the oxidation rate is limited by the interfacial reaction between oxygen and sulfide. At the pyrite grain scale, evidence suggests that oxygen diffusion to the oxidation front limits the rate. At the pedon scale, diffusion is constrained by fracture formation rates. Finally, at the borehole scale, the rate at which oxygenated water reaches unoxidized pyrite at depth is limited by the erosive removal of overlying soil and weathered rock. Thus, as the scale of observation increases, the rate-limiting step for pyrite oxidation transitions from chemical reaction → diffusion → fracturing → erosion.
 

Biography
 

Xin Gu is a broadly trained critical zone scientist with degrees in Environmental Engineering (B.E., Tsinghua University), Forest Resources (M.S., Penn State University), and Geosciences and Biogeochemistry (Ph.D., Penn State University). From 2018 to 2021, he worked at the Earth and Environmental Systems Institute at Penn State as a PostDoc and later as an Assistant Research Professor. Since 2021, he has been an experimental geochemist in the Environmental Division at Oak Ridge National Laboratory. His research focuses on how geochemical reactions at pore scales drive macroscopic processes such as chemical weathering, watershed hydrology, and landscape evolution.

 

 

Greetings, and welcome to the October 14, 2024 ETGS hybrid meeting.
 

If you attend via Zoom as a courtesy please mute your cell phone or the microphone in your laptop/tablet to minimize background noise and feedback echos. We will also make an effort to mute all participants - at least until the presentation is finished. Please use the chat feature to type any comments or questions you may have. We recommend that you send questions for the speaker to "everyone" so all participants can see the question. In the interest of time, we may hold the Q&A at the end of the presentation.

We will create an in-person and virtual attendance list. It is not always possible to tell who is participating on-line, especially for those joining by phone, so please email etgs@live.com to be listed on the attendance sheet. Let us know exactly how your name should appear on the list. We will add a note explaining the lack of signatures due to remote participation and have an ETGS officer sign as usual.

Thank you for your patience and understanding as we try this online format. As always, we welcome and appreciate your feedback and suggestions for improvement.

 

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President
David Carlone

Vice President
Open

Secretary
J. Brad Stephenson

Treasurer
Seaira Stephenson

Webmaster/Social Media Coordinator
Bob Gelinas

 

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Page updated October 14, 2024