NASA Technical Reports Server NTRS 20140010586: Diversity in C-Xanes Spectra Obtained from Carbonaceous Solid Inclusions from Monahans HaliteReportar como inadecuado



 NASA Technical Reports Server NTRS 20140010586: Diversity in C-Xanes Spectra Obtained from Carbonaceous Solid Inclusions from Monahans Halite


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Monahans meteorite H5 contains fluid inclusion- bearing halite NaCl crystals 1. Microthermometry and Raman spectroscopy showed that the fluid in the inclusions is an aqueous brine and they were trapped near 25degC 1. Their continued presence in the halite grains requires that their incorporation into the H chondrite asteroid was post metamorphism 2. Abundant solid inclusions are also present in the halites. The solid inclusions include abundant and widely variable organics 2. Analyses by Raman microprobe, SEM-EDX, synchrotron X-ray diffraction and TEM reveal that these grains include macromolecular carbon similar in structure to CV3 chondrite matrix carbon, aliphatic carbon compounds, olivine Fo99-59, high- and low-Ca pyroxene, feldspars, magnetite, sulfides, lepidocrocite, carbonates, diamond, apatite and possibly the zeolite phillipsite 3. Here we report organic analyses of these carbonaceous residues in Monahans halite using C-, N-, and O- X-ray absorption near edge structure XANES. Samples and Methods: Approximately 100 nm-thick sections were extracted with a focused ion beam FIB at JSC from solid inclusions from Monahans halite. The sections were analyzed using the scanning transmission X-ray microscope STXM on beamline 5.3.2.2 at the Advanced Light Source, Lawrence Berkeley National Laboratory for XANES spectroscopy. Results and Discussion: C-XANES spectra of the solid inclusions show micrometer-scale heterogeneity, indicating that the macromolecular carbon in the inclusions have complex chemical variations. C-XANES features include 284.7 eV assigned to aromatic C=C, 288.4-288.8 eV assigned to carboxyl, and 290.6 eV assigned to carbonate. The carbonyl features obtained by CXANES might have been caused by the FIB used in sample preparation. No specific N-XANES features are observed. The CXANES spectra obtained from several areas in the FIB sections include type 1and2 chondritic IOM like, type 3 chondritic IOM like, and none of the above. The natures of the macromolecular carbon in the solid inclusions observed by C-XANES are consistent with the previous studies showing that the carbonaceous solid inclusions have not originated from Monahans parent body 1-3, and have various origins, including various chondritic meteorite parent bodies as well as other unknown sources.



Autor: NASA Technical Reports Server (NTRS)

Fuente: https://archive.org/







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