Presentation Title

X-ray mapping of Carbonaceous Chondrites: A Hunt for Carbonate Minerals

Faculty Mentor

Prof. Kevin McKeegan

Start Date

17-11-2018 12:30 PM

End Date

17-11-2018 2:30 PM

Location

CREVELING 43

Session

POSTER 2

Type of Presentation

Poster

Subject Area

physical_mathematical_sciences

Abstract

One way to go back in time to the formation of the solar system is to study meteorites. We can learn about the materials that formed the solar system and the processes that occurred during and after the formation of asteroids and planets by studying the mineralogy, chemistry, and isotopic compositions of meteorites. A particularly interesting group of meteorites is the carbonaceous chondrites, especially its subgroup, the CM chondrites. CM chondrites contain volatile elements, organic matter, and experienced fluid-rock interaction in an asteroid prior to delivery to Earth. This interaction gave rise to carbonate minerals, which are strong evidence for the presence of liquid water. These carbonates can be analyzed to learn more about the conditions in these water-rich bodies. In this project, we investigated the CM chondrites Murchison and QUE97990 to search for carbonates. By using a scanning electron microscope (SEM), we produced maps of polished surfaces of each meteorite that can be interpreted to study major element chemistry and mineralogy at the microscopic scale. We obtained x-ray maps of the samples to identify the carbonate grains, which on closer analysis at higher magnification was revealed to have calcium in high abundance, followed by oxygen and carbon; the carbonates here were calcites. We plan to follow up with SEM scans of additional CM meteorites exhibiting different degrees of aqueous alteration. Isotopic analyses of these carbonates using the ion microprobe will then give us more information on the formation conditions of carbonates, and help us understand the alteration processes that took place on these meteorites.

Summary of research results to be presented

With the aid of the BSE and x-ray maps, we found not more than forty carbonates on the given samples of the CM meteorites. The mineralogical characterization of these carbonates is given by the spectra generated from the EDS technique. The relative heights of the peaks, which give the intensity of the x-rays generated, describes the relative abundance of the elements in the meteorite. It can be seen from x-ray spectra taken from carbonates that calcium (Ca) is the most abundant, followed by oxygen (O) and carbon (C) indicating that the carbonates in these CM meteorites are primarily calcite (CaCO3), consistent with previous studies. Characteristics like mineralogy, microstructure, presence or absence of inclusions, and the details of any rims are used to distinguish carbonates and classify them. These images and primary classification help to quantify carbonates for further isotopic analyses to understand the aqueous alteration processes on these meteorites.

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Nov 17th, 12:30 PM Nov 17th, 2:30 PM

X-ray mapping of Carbonaceous Chondrites: A Hunt for Carbonate Minerals

CREVELING 43

One way to go back in time to the formation of the solar system is to study meteorites. We can learn about the materials that formed the solar system and the processes that occurred during and after the formation of asteroids and planets by studying the mineralogy, chemistry, and isotopic compositions of meteorites. A particularly interesting group of meteorites is the carbonaceous chondrites, especially its subgroup, the CM chondrites. CM chondrites contain volatile elements, organic matter, and experienced fluid-rock interaction in an asteroid prior to delivery to Earth. This interaction gave rise to carbonate minerals, which are strong evidence for the presence of liquid water. These carbonates can be analyzed to learn more about the conditions in these water-rich bodies. In this project, we investigated the CM chondrites Murchison and QUE97990 to search for carbonates. By using a scanning electron microscope (SEM), we produced maps of polished surfaces of each meteorite that can be interpreted to study major element chemistry and mineralogy at the microscopic scale. We obtained x-ray maps of the samples to identify the carbonate grains, which on closer analysis at higher magnification was revealed to have calcium in high abundance, followed by oxygen and carbon; the carbonates here were calcites. We plan to follow up with SEM scans of additional CM meteorites exhibiting different degrees of aqueous alteration. Isotopic analyses of these carbonates using the ion microprobe will then give us more information on the formation conditions of carbonates, and help us understand the alteration processes that took place on these meteorites.