The process was fast and furious, he added.
"The magnesite veins are very white, homogenous and composed of very tiny crystals, so they probably formed quickly, perhaps instantaneously," del Real explained. "The ultramafic rocks appear shattered and broken, which means that this was a violent event."
Back at the lab, the Stanford scientists conducted an isotopic analysis of the magnesite samples collected at the mine. The results suggest that when the San Andreas fault opened, magnesite formed 1 kilometer below the surface as temperatures rose from about 53 degrees Fahrenheit (12 degrees Celsius) to 86 F (30 C). Such low temperatures should make it relatively easy for scientists to convert atmospheric CO2 into pure magnesite. But del Real and his colleagues have yet to replicate the process experimentally.
"If we inject CO2 from a power plant or other point source into ultramafic rock, we would expect it to form magnesite," he said. "But when we try to make magnesite in the laboratory at low temperatures, it fails to form."
For carbon sequestration to succeed, scientists will also have to figure out a way to make ultramafic rock permeable. "There is no way that CO2 or anything else will flow through these rocks," del Real said. He will discuss the problem of permeability at the AGU meeting on Dec. 10 at 10:20 a.m. PT in Moscone Center South, room 301.
"In our research, we combine a big tectonics approach with the minute thermodynamic behavior of fluids," del Real said. "So we go from the very large scale to the very small scale."
|Contact: Mark Shwartz|