Jeffrey Nittrouer and Hongbo Ma -Yellow River research highlighted in China Daily

http://usa.chinadaily.com.cn/world/2017-05/23/content_29466587.htm

 

Audrey Odwuor, an Earth Science graduating senior, receives the 2017 Dr. Mae C. Jemison Award for Academic Achievement and Public Service

Deep Subduction of Organic Carbon Helped Atmospheric Oxygen Rise

Study: Early organic carbon got deep burial in mantle

Petrology experiments support tectonic role in Earth’s ‘great oxidation event’

Rice University petrologists who recreated hot, high-pressure conditions from 60 miles below Earth’s surface have found a new clue about a crucial event in the planet’s deep past.

Earth's atmosphere, as seen in 2003 from the International Space Station

Earth’s atmosphere, as seen in 2003 from the International Space Station, hasn’t always contained large amounts of oxygen. Petrologists from Rice University and the Carnegie Institution recreated hot, high-pressure conditions from 60 miles below Earth’s surface in search of new clues about the “great oxidation event” that added large amounts of oxygen to the atmosphere around 2.4 billion years ago. (Photo courtesy of ISS Expedition 7 Crew, EOL, NASA)

Their study describes how fossilized carbon — the remains of Earth’s earliest single-celled creatures — could have been subsumed and locked deep in Earth’s interior starting around 2.4 billion years ago — a time when atmospheric oxygen rose dramatically. The paper appears online this week in the journal Nature Geoscience.

“It’s an interesting concept, but in order for complex life to evolve, the earliest form of life needed to be deeply buried in the planet’s mantle,” said Rajdeep Dasgupta, a professor of Earth science at Rice. “The mechanism for that burial comes in two parts. First, you need some form of plate tectonics, a mechanism to carry the carbon remains of early life-forms back into Earth. Second, you need the correct geochemistry so that organic carbon can be carried deeply into Earth’s interior and thereby removed from the surface environment for a long time.”

At issue is what caused the “great oxidation event,” a steep increase in atmospheric oxygen that is well-documented in countless ancient rocks. The event is so well-known to geologists that they often simply refer to it as the “GOE.” But despite this familiarity, there’s no scientific consensus about what caused the GOE. For example, scientists know Earth’s earliest known life, single-celled cyanobacteria, drew down carbon dioxide from the atmosphere and released oxygen. But the appearance of early life has been pushed further and further into the past with recent fossil discoveries, and scientists now know that cyanobacteria were prevalent at least 500 million years before the GOE.

Megan Duncan

Megan Duncan (Photo by Jeff Fitlow/Rice University)

“Cyanobacteria may have played a role, but the GOE was so dramatic — oxygen concentration increased as much as 10,000 times — that cyanobacteria by themselves could not account for it,” said lead co-author Megan Duncan, who conducted the research for her Ph.D. dissertation at Rice. “There also has to be a mechanism to remove a significant amount of reduced carbon from the biosphere, and thereby shift the relative concentration of oxygen within the system,” she said.

Removing carbon without removing oxygen requires special circumstances because the two elements are prone to bind with one another. They form one of the key components of the atmosphere — carbon dioxide — as well as all types of carbonate rocks.

Dasgupta and Duncan found that the chemical composition of the “silicate melt” — subducting crustal rock that melts and rises back to the surface through volcanic eruptions — plays a crucial role in determining whether fossilized organic carbon, or graphite, sinks into the mantle or rises back to the surface through volcanism.

Schematic depiction of the efficient deep subduction of organic carbon

This schematic depicts the efficient deep subduction of organic (reduced) carbon, a process that could have locked significant amounts of carbon in Earth’s mantle and resulted in a higher percentage of atmospheric oxygen. Based on new high-pressure, high-temperature experiments, Rice University petrologists argue that the long-term sequestration of organic carbon from this process began as early as 2.5 billion years ago and helped bring about a well-known buildup of oxygen in Earth’s atmosphere — the “Great Oxidation Event” — about 2.4 billion years ago. (Image courtesy of R. Dasgupta/Rice University)

Duncan, now a research scientist at the Carnegie Institution in Washington, D.C., said the study is the first to examine the graphite-carrying capacity of a type of melt known as rhyolite, which is commonly produced deep in the mantle and carries significant amounts of carbon to the volcanoes. She said the graphite-carrying capacity of rhyolitic rock is crucial because if graphite is prone to hitching a ride back to the surface via extraction of rhyolitic melt, it would not have been buried in sufficient quantities to account for the GOE.

“Silicate composition plays an important role,” she said. “Scientists have previously looked at carbon-carrying capacities in compositions that were much more magnesium-rich and silicon-poor. But the compositions of these rhyolitic melts are high in silicon and aluminum and have very little calcium, magnesium and iron. That matters because calcium and magnesium are cations, and they change the amount of carbon you can dissolve.”

Dasgupta and Duncan found that rhyolitic melts could dissolve very little graphite, even when very hot.

“That was one of our motivations,” said Dasgupta, professor of Earth science. “If subduction zones in the past were very hot and produced a substantial amount of melt, could they completely destabilize organic carbon and release it back to the surface?

“What we showed was that even at very, very high temperatures, not much of this graphitic carbon dissolves in the melt,” he said. “So even though the temperature is high and you produce a lot of melt, this organic carbon is not very soluble in that melt, and the carbon gets buried in the mantle as a result.

Rajdeep Dasgupta

Rajdeep Dasgupta (Photo by Jeff Fitlow/Rice University)

“What is neat is that with the onset and the expected tempo of crustal burial into the deep mantle starting just prior to the GOE, and with our experimental data on the efficiency of deep burial of reduced carbon, we could model the expected rise of atmospheric oxygen across the GOE,” Dasgupta said.

The research supports the findings of a 2016 paper by fellow Rice petrologist Cin-Ty Lee and colleagues that suggested that plate tectonics, continent formation and the appearance of early life were key factors in the development of an oxygen-rich atmosphere on Earth.

Duncan, who increasingly focuses on exoplanetary systems, said the research could provide important clues about what scientists should look for when evaluating which exoplanets could support life.

The research is supported by the National Science Foundation and the Deep Carbon Observatory.

About Jade Boyd

Jade Boyd is science editor and associate director of news and media relations in Rice University’s Office of Public Affairs.

 

Cin-Ty Lee- 2017 Guggenheim Fellow

Rice’s Cin-Ty Lee wins Guggenheim Fellowship

Earth scientist will study how and when continents emerged from oceans

Rice University Earth scientist Cin-Ty Lee has won a prestigious Guggenheim Fellowship to investigate how and when continents emerged from the oceans and the effect of their emergence on the evolution of whole-Earth cycling of life-giving nutrients.

Lee is one of 173 scholars, artists and scientists — and the only Earth scientist — chosen as 2017 Guggenheim Fellows. The fellows represent 49 disciplines and 64 academic institutions and were chosen from nearly 3,000 applicants. Funded by the John Simon Guggenheim Memorial Foundation, the fellowships are awarded on the basis of achievements and exceptional promise to allow scholars to pursue their work with creative freedom.

Lee joined Rice in 2002 and is a professor and chair of the Department of Earth Science. He studies the compositions of rocks to reconstruct how Earth’s interior, surface, atmosphere and life have evolved over time. Specifically, his interests lie in understanding how mountains and continents form, how Earth’s deep interior has differentiated and how deep-Earth processes modulate long-term climate and Earth’s habitability.In addition to researching the emergence and impact of continents, Lee will use the Guggenheim funding to explore crystal growth and kinetics in magmatic and hydrothermal conditions.

Lee has a B.A. from the University of California, Berkeley and a Ph.D. from Harvard University. He has published more than 100 papers on a wide range of topics, including whole-Earth carbon cycling, the rise of atmospheric oxygen, the formation of ore deposits, coupling between magmatism and erosion, the temperature of Earth’s mantle and the origin of granites. He is a fellow of the Mineralogical Society of America and the Geological Society of America and has been awarded the Kuno Medal from the American Geophysical Union, the Clarke Medal from the Geochemical Society, the Donath Medal from the Geological Society of America and a Packard Fellowship.

Lee is also a world-renowned field ornithologist who spends much of his spare time painting birds and traveling the world in search of birds. He has published numerous articles on field identification of such difficult complexes as Arctic and Pacific loons, female orioles, American and Siberian pipits and dowitchers. He is currently working on a new guide to the identification of Empidonax flycatchers. He donates his paintings, teaches courses and leads field trips to benefit conservation-oriented nonprofit organizations and local schools.

Guggenheim Fellowships have been awarded annually since 1925. Each fellow is awarded a grant to help provide them with blocks of time in which they can work with as much creative freedom as possible. Grants have no special conditions attached and fellows may spend their grant funds in any manner they deem necessary to do their work.

see more : Rice’s Cin-Ty Lee wins Guggenheim Fellowship

Sarah Gerenday receives HGS Undergraduate Scholarship

The Houston Geological Society Undergraduate Scholarship Foundation have chosen Sarah Gerenday to receive a scholarship for the 2016-2017 academic year. The scholarship goal is to provide financial support for applicants in their endeavor towards a career in geoscience.

Sarah Gerenday is an undergraduate Senior with diverse interests and talents ranging from donating time to social programs in support of medical research and minority student recruiting, to international choir residency at St. Mary’s Cathedral in Edinburgh.

In the summer of 2015, Sarah was granted the the opportunity to participate in a Department of Energy sponsored Science Undergraduate Laboratory Internship at Argonne National Lab’s Applied Geoscience and Environmental Management section. That effort will support Sarah’s goal to continue with graduate research focused on the safety and effectiveness of combined geological and industrial endeavors, using geologic knowledge to develop efficient plans that minimize environmental impact.

Currently, Sarah is working on a senior honors thesis that studies the physical and geochemical history of peridotite zenoliths from kimberlites in the Kaapvaall craton in South Africa.

The HGS Foundation Trustees have invited Sarah and a faculty representative to attend the February 13th dinner meeting where they will honor all the scholarship winners.

Dr. Albert Bally awarded a Doctor Honoris Causa from the University of Fribourg (Switzerland)

Rice wins 1st Place Poster at AAPG Student Expo 2016

expo_2016-20

Pankaj Khanna, PhD Candidate, won the 1st Place Poster award at the AAPG Student Expo, Houston 2016.

Poster title – ‘ Uppermost Pleistocene coralgal Reefs and Upper Cambrian microbial bioherms: Morphologies and sea-level induced evolution’