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NMSU geology professor studies C02 storage in rocks in Norway

Carbon is considered the basic building block for all life on the planet and it occurs in large volumes on Earth where is cycles through the atmosphere, oceans, soils, and rocks. Most people are likely familiar with carbon storage in the atmosphere in the form of carbon dioxide gas (CO2). However, a large amount of CO2 is in fact stored in solid form in rocks that make up the outer layers of the Earth's crust.

People sitting, crouching standing on large rocks
Team members collect rock samples in Norway. (Photo courtesy of Brian Hampton)
Wide shot of landscape with base camp and bodies of water
Base camp for the research team, which included Brian Hampton from NMSU's Geology Department, in Norway.
Two men and two women standing on rock with snowcapped mountains behind them
Brian Hampton and team members in Norway. (Courtesy Photo)

Brian Hampton, NMSU assistant professor of geology in the College of Arts and Sciences recently co-authored a paper in the journal "Nature Communications" that analyzed how solid CO2 is stored in iron- and magnesium-bearing (ultramafic) igneous rocks through the process of carbonation.

"The natural process of CO2 transfer from the atmosphere to rocks occurs on slow, geologic time scales, but recent work is showing that this process could potentially be geo-engineered to sequester CO2 on much faster, human times scales" Hampton said. "This is exciting as it provides an additional avenue for long-term solid storage of atmospheric greenhouse gasses through the process of carbonation in ultramafic rocks".

For part of this project, Hampton and an international team of faculty and students from NMSU, Texas A&M, MIT, Woods Hole Oceanographic Institute, as well as researchers from Norway, Japan, and British Columbia traveled to the remote, mountainous backcountry of northern Norway to document this process in the field.

"Our current understanding on the reaction mechanisms that take place during the carbonation process are based on previous studies in the lab on small, hand-specimens of rock" Hampton said. "The goals of our study were to build on what has been documented in the lab and see if we could recognize, through both geologic and geophysical field approaches, where and how carbonation of rocks has taken place on both small and large scales in natural geologic settings".

While ultramafic rocks are not rare on Earth, most originate and are found on the ocean floor which makes them difficult to access for field studies. However, occurrences of ultramafic rocks are quite common in the highest mountain belts on Earth due to the collision of continental tectonic plates that results in the closing of ocean basins which brings these oceanic rocks to the surface.

"The mountainous backcountry of Norway is an excellent natural laboratory to study carbonation in ultramafic rocks due to an early Paleozoic collisional mountain-building event that exposed ancient ultramafic oceanic crust" Hampton said.

For part of their study, Hampton and colleagues presented the first geophysical characterization of carbonation across scales ranging from sub-millimeter to multi-kilometer scale by combined approaches of aeromagnetic, outcrop, and thin-section microscope mapping of carbonation fronts.

"What we documented is that at all scales, magnetic anomalies associated with carbonation change in a predictable manner across reaction fronts" Hampton said. "It also is clear that the abundance of magnetic minerals associated with the carbonation process directly correlate with the reaction process which causes a signal that can be recognized through geophysical field techniques." Results from this study provide a foundation for characterizing the extent and degree of ultramafic rock carbonation on both long and short time periods."

By far, the largest amount of carbon on Earth is stored in solid form in sedimentary rocks and much of Hampton's research at NMSU is on where sediment is sourced and how it is transported, deposited, and organized in sedimentary basins.

"Much of my research focus at NMSU is on how sedimentary rocks are organized in the Earth's subsurface which has applications for the exploration and extraction of hydrocarbon and water resources that are housed in these rocks" Hampton said. "This project was especially exciting for me in that I had the chance to branch out and explore how carbon in the form of solid CO2 is stored in ultramafic igneous rock and how this process may be a pathway for mitigating the effects of greenhouse gasses".

Much of Hampton's sedimentology and tectonics research at NMSU includes field work in remote mountain belts throughout parts of North America including the Alaska Range in southern Alaska. Hampton and colleagues would like to purse similar field-based studies on the carbonation process in parts of Alaska where ultramafic rocks are exposed.

Hamptonís paper can be found at https://www.nature.com/articles/s41467-017-01610-4.