[meteorite-list] Microprobe Assists in Identifying Chemical Elements of Solids

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri Jun 9 00:07:13 2006
Message-ID: <200606082028.NAA07246_at_zagami.jpl.nasa.gov>

http://chronicle.uchicago.edu/060608/microprobe.shtml

The University of Chicago Chronicle
June 8, 2006
Vol. 25 No. 18
    
Microprobe assists in identifying chemical elements of solids
By Steve Koppes

The Electron Microprobe Laboratory has helped mining companies
prospect for diamonds in Brazil and Canada, determine the
composition of meteorites from deep space, and study a deadly
disease in Turkey. And as one of the shared instrument facilities
supported by the Office of the Vice President for Research and for
Argonne National Laboratory, it is accepting new clients from
across campus and from Argonne.

The microprobe can determine the type and amount of almost any
chemical element found within a one-micron patch of sample,
according to laboratory Director Ian Steele. A micron, one
millionth of a meter, is just a small fraction the width of a
human hair.

"You'll see this machine periodically in CSI. They come up with a
composition of the dirt the person walked in, or something like
that," he said.

The samples Steele receives are more likely to be a chunk of
metal, a meteorite or a piece of bone. The vacuum condition under
which the beam operates excludes the analysis of fluids and soft
organic materials.

When the microprobe's electron beam hits a sample, the electrons
slow, generating X-rays from the sample itself. "The type and
number of X-rays are proportional to the element and the amount of
that element," Steele explained.

The University, with partial support from the National Science
Foundation, purchased the instrument in 1986 for $400,000. "There
are probably a hundred of these at universities in the United
States, and another hundred in industry," Steele said. His clients
in the past have included archaeologists from the University's
Oriental Institute, art historians from the Art Institute of
Chicago, and scientists at universities in Illinois, Indiana and
Wisconsin.

Lawrence Grossman, Professor in Geophysical Sciences, the Enrico
Fermi Institute and the College, and Steven Simon, Senior Research
Associate in Geophysical Sciences, rely heavily upon the electron
microprobe to study meteorites. The chemical data locked within
meteorite grains holds detailed information about how the sun and
planets condensed from the gas cloud that formed the solar system.

The microprobe also helps mining companies locate diamond
deposits. "They don't actually look for diamonds. They look for
minerals that are known to occur with diamonds," Steele said.
Armed with Steele's data, the companies can follow the
mineralogical trail of garnet, pyroxene, ilmenite and chromite
washing downstream from some unknown source of diamonds.

>From the University Hospitals, Steele has analyzed a variety of
biomedical samples, including kidney stones, particles extracted
from fluids or lodged in lung tissue. "You can analyze the
particles embedded in the lung," said Grossman, the faculty member
who oversees the laboratory. The lung tissue itself consists of
carbon, hydrogen and oxygen, all elements that the microprobe
cannot detect.

Steele is currently working with a doctor who studies
mesothelioma, a deadly disease of the lungs usually associated
with asbestos exposure. But in a region of central Turkey called
Cappodocia, the culprit is the mineral erionite.

"It's the most carcinogenic mineral, according to the World Health
Organization," Steele said. "Hence, half the people in this area
die of mesothelioma. In the average population it's much less than
1 percent."

The physicians who have studied mesothelioma in Cappodocia have
learned that the disease has a genetic component. Some entire
families fall victim to the disease, while families living next
door escape unharmed. To further nail down what role genetics
plays in the disease, Steele is helping to determine whether the
erionite in the fatal rock dwellings differs in any way from the
homes where healthy families live.

They all live in caves and houses made of volcanic rock erupted
from a volcano 30 miles distant. "That's the thing that keeps
spewing out a rock called tuff," Steele said. "It's a relatively
soft rock, easy to work with and hence used for house construction."

Unfortunately, the tuff contains erionite grains that the local
people breathe into their lungs. "These grains are typically like
little needles, just like asbestos," Steele said. "When you get
mesothelioma, you die. There's no cure."

Fees for using the microprobe lab start at $300 a day, and that's
probably a bargain. "You can get huge amounts of information in a
day," Grossman said. For more information, call Steele at (773)
702-8109.
Received on Thu 08 Jun 2006 04:28:35 PM PDT