Diamonds and rust at the Earth's core-mantle boundary

Scientists in ASU’s School of Earth and Space Exploration assist in discovery of potential 'diamond factory' that may have existed at the core-mantle boundary for billions of years

August 29, 2022

Steel rusts by water and air on the Earth’s surface. But what about deep inside the Earth’s interior?

The Earth’s core is the largest carbon storage on Earth – roughly 90% is buried there. Scientists have shown that the oceanic crust that sits on top of tectonic plates and falls into the interior (in a process called subduction) contains hydrous minerals, and can sometimes descend all the way to the core-mantle boundary. Illustration of iron-carbon alloy reacting with water at high pressure and high temperaturein the Earth’s deep mantle. The iron-carbon alloy reacted with water at high pressure and high temperature conditions related to the Earth’s deep mantle in a diamond-anvil cell. Download Full Image

The temperature at the core-mantle boundary is at least twice as hot as lava, and high enough that water can be released from the hydrous minerals. Therefore, a chemical reaction similar to rusting steel could occur at Earth’s core-mantle boundary.

Byeongkwan Ko, a recent Arizona State University PhD graduate, and his collaborators have been conducting experiments at the Advanced Photon Source at Argonne National Laboratory, where they compressed iron-carbon alloy and water together to the pressure and temperature expected for Earth’s core-mantle boundary, melting the iron-carbon alloy.

The team found that water and metal react and make iron oxides and iron hydroxides, just like rusting at Earth’s surface. However, they found that for the conditions of the core-mantle boundary, unlike rusting at Earth’s surface, carbon comes out of the liquid iron metal alloy and forms diamond.

Ko and his team published their findings in a paper in Geophysical Research Letters.

“Temperature at the boundary between the silicate mantle and the metallic core at 3,000 km depth reaches to (about 7,000 degrees Fahrenheit), which is sufficiently high for most minerals to lose H2O captured in their atomic-scale structures,” says Dan Shim, a professor at ASU's School of Earth and Space Exploration and a co-author on the paper. “In fact, the temperature is high enough that some minerals should melt at such conditions.”

Because carbon is an iron-loving element, significant carbon is expected to exist in the core, while the mantle is thought to have relatively low carbon. However, scientists have found that much more carbon exists in the mantle than expected. 

“At the pressures expected for the Earth's core-mantle boundary, hydrogen alloying with iron metal liquid appears to reduce solubility of other light elements in the core. Therefore, solubility of carbon, which likely exists in the Earth's core, decreases locally where hydrogen enters into the core from the mantle (through dehydration),” Shim says. “The stable form of carbon at the pressure-temperature conditions of the Earth's core-mantle boundary is diamond. So the carbon escaping from the liquid outer core would become diamond when it enters into the mantle.”

“Carbon is an essential element for life and plays an important role in many geological processes. The new discovery of a carbon transfer mechanism from the core to the mantle will shed light on the understanding of the carbon cycle in the Earth’s deep interior,” Ko says. “This is even more exciting given that the diamond formation at the core-mantle boundary might have been going on for billions of years since the initiation of subduction on the planet.”

Ko's new study shows that carbon leaking from the core into the mantle by this diamond formation process may supply enough carbon to explain the elevated carbon amounts in the mantle. Ko and his collaborators also predicted that diamond-rich structures can exist at the core-mantle boundary and that seismic studies might detect the structures because seismic waves should travel unusually fast for the structures.

“The reason that seismic waves should propagate exceptionally fast through diamond-rich structures at the core-mantle boundary is because diamond is extremely incompressible and less dense than other materials at the core-mantle boundary,” Shim says.

Ko and his team will continue investigating how the reaction can also change the concentration of the other light elements in the core, such as silicon, sulfur and oxygen, and how such changes can impact the mineralogy of the deep mantle.

Andrea Chatwood

Communications Specialist, The College of Liberal Arts and Sciences

New ASU center aims to showcase Muslim contributions, accomplishments in US

The Center of Muslim Experience in the United States draws on ASU's charter of inclusivity, public values and community impact

August 29, 2022

The recent launch of the Center of Muslim Experience in the United States (CME-US) at Arizona State Univerity reflects a pioneering endeavor to advance research and deepen public knowledge on the understudied history of Muslims in the United States and their many contributions to American society and culture.

With a student-centered approach, CME-US will facilitate belonging for Muslim students at ASU and work to build mutually beneficial partnerships between Muslim communities across the country and university. The center will be housed in the School of Historical, Philosophical and Religious Studies and is part of the humanities division in The College of Liberal Arts and Sciences. Portrait of Yasmin Saikia and Chad Haines, co-directors of the Center of Muslim Experience at ASU. Yasmin Saikia and Chad Haines, co-directors of the Center of Muslim Experience in the United States. Download Full Image

​​“In creating the vision of CME-US, we were inspired by ASU’s mission of being ‘measured not by whom we exclude, but rather by whom we include and how they succeed,’ and by its commitment to research defined by public value,” says Chad Haines, associate professor of religious studies at the School of Historical, Philosophical and Religious Studes and co-director of CME-US. “These values connect with Islamic ethics of acceptance and working for the social good that is evident in Muslim American communities and their experiences, providing CME-US a unique opportunity to bridge diverse worlds and advance ASU’s mission.” 

In the first three years, Haines and co-director Yasmin Saikia, Hardt-Nickachos Chair in Peace Studies at the Center for the Study of Religion and Conflict and professor of history in the School of Historical, Philosophical and Religious Studies, will work to develop a faculty- and student-led academic project and write a report on “Global Phoenix and Muslim Lives and Contributions.” The study will document the long history of Muslims in the Valley and their richly diverse cultures, along with their many contributions to making Phoenix a uniquely global city.

In addition, they plan to conduct a “Connections” seminar bringing together faculty, graduate students and journalists to work on writing about Muslims from a new perspective for wider public dissemination. All of this work will lead to the creation of a digital virtual museum on Muslim experiences in the United States.

“The Muslim contribution to world history and culture would be difficult to overstate – and the Muslim experience in the United States has helped to shape the nation,” says Jeffrey Cohen, dean of humanities. “ASU has a population of over 8,000 Muslim faculty, staff and students. They deserve to have their stories, histories and rich cultures valued and shared. Under the leadership of Dr. Haines and Dr. Saikia, CME-US will change the narrative, both locally and nationally, to ensure that the Muslim experience in the U.S. receives the attention it deserves.”

“By creating a space for students to share their own stories, both Muslim and non-Muslim students will benefit from knowing one another and learning to appreciate that socio-cultural differences can benefit improved community-building locally,” Haines ssays.

The CME-US will also highlight the diversity and creativity of Muslim Americans and their contributions to American culture by organizing events and performances. The center plans to host poetry readings and musical performances, curate exhibits documenting Muslim lives and invite Muslim stand-up comics, actors, inspirational speakers and writers to ASU for public events.

Haines and Saikia have coedited three books: “Women and Peace in the Islamic World,” “People’s Peace” and their forthcoming book, “On Othering.”

“The focus of our books is on sustainable peace forged by everyday lived ethics between people rather than the Band-Aid solutions of conflict management by international organizations that dominate the field of peace studies. We decided to focus our work on the most misrepresented group in the United States – the Muslims – and tell their story from their perspective to transform the relationship between Muslims and the wider American public,” Saikia says.

Saikia, who is Muslim by birth and a naturalized American citizen, says “at the heart of the many misconceptions of Islam are Muslim women. This needs addressing and discussing so we can transform the skewed image and show the reality of how Muslim women in America are contributing to multiple facets of American community life and well-being.”

The center will develop workshops, public lectures and community outreach to schools and local organizations to educate and advance scholarship of ASU faculty and graduate students on Amercian Muslim women.

Combining ASU’s power as the largest university in the country, the support of ASU’s administration and Arizona’s vibrant and fastest-growing local Muslim community, Saikia and Haines look forward to the work ahead.

They said their aim is to show how Muslim experiences can contribute to making the United States a more dynamic and inclusive country.

Andrea Chatwood

Communications Specialist, The College of Liberal Arts and Sciences