Other
Scientific paper
Nov 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007gecoa..71.5180t&link_type=abstract
Geochimica et Cosmochimica Acta, Volume 71, Issue 21, p. 5180-5190.
Other
3
Scientific paper
Local atomic structures of Re and radiogenic Os in molybdenite from the Onganja mine, Namibia, were examined using X-ray absorption fine structure (XAFS). Rhenium LIII-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) show that the oxidation state of Re, the interatomic distances between Re and the neighboring atoms, and the coordination number of Re to S are very similar to those of Mo in molybdenite. The results confirm that Re is present as Re(IV) in the Mo site in molybdenite. Measurement of LIII-edge XANES and EXAFS of a minor concentration (8.55 ppm) of radiogenic Os was accomplished in fluorescence mode by removing the interfering X-rays from Re and other elements using a crystal analyzer system. The data indicate that the oxidation state of radiogenic Os is Os(III) and Os(IV) and clearly different from Os(II) in natural sulfide minerals, such as OsS2 (erlichmanite). XANES data also suggest that radiogenic Os does not form a secondary Os phase, such as OsS2 or Os metal, in molybdenite. EXAFS of radiogenic Os was successfully simulated assuming that Os is present in the Mo site in molybdenite. The data are consistent with the XANES data; Os does not form Os phases in molybdenite. The EXAFS simulation showed that the interatomic distance between Os and S is 2.27 Å, which is 0.12 Å smaller than the distances of Re S and Mo S (2.39 Å) in molybdenite. Similar valences and ionic sizes of Re and Mo in molybdenite support the fact that large amounts of Re can be incorporated into the Mo site as has been observed in previous studies, whereas the different properties of Os compared to Mo and Re suggested here support much lower abundance of common Os in molybdenite. This makes molybdenite an ideal mineral for the Re Os geochronometer as shown in many studies. However, the shorter distance between radiogenic Os and S compared to those of Re S and Mo S in molybdenite suggests that the radiogenic Os has a smaller ionic size than Re(IV) and Mo(IV). Furthermore, Os may be partly present as Os(III). Smaller and lower charge Os can diffuse faster than larger and higher charge Re in molybdenite at a given set of conditions. Hence, our study provides an atomic-level explanation for the high mobility of Os compared to Re, which has been suggested by earlier workers using laser ablation ICP-MS.
Hattori Keiko H.
Suzuki Katsuhiko
Takahashi Yoshio
Tanida Hajime
Terada Yasuko
No associations
LandOfFree
An atomic level study of rhenium and radiogenic osmium in molybdenite does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with An atomic level study of rhenium and radiogenic osmium in molybdenite, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and An atomic level study of rhenium and radiogenic osmium in molybdenite will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-739820