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Mass-Independent Sulfur Isotope Records from the Hamersley Basin Austrlaia
| Content Provider | Semantic Scholar |
|---|---|
| Author | Ono, Shimpei Rumble, Douglas Iii Pavlov, Alexander A. Eigenbrode, Jennifer L. Kasting, James F. Lindsay, J. Murray Freeman, Katherine H. |
| Copyright Year | 2003 |
| Abstract | An orthorhombic Mg-perovskite is generally accepted to be the dominant phase of the Earth’s lower mantle. Information on its density and bulk and shear modulus under various pressures and temperatures is, therefore, of prime importance in determining the composition and properties of the lower mantle. Experimental reports of the bulk modulus of Al-bearing orthorhombic Mgperovskite remain controversial. In previous studies of EOS for orthorhombic perovskite, chemical compositions were simple. However, the chemical composition of natural orthorhombic perovskite seems to be complicate. I investigated the pressure-volume EOS of orthorhombic perovskite possessing natural composition, which had some minor components, such as FeO, Al2O3, TiO2, CaO, and Na 2O. The minor components of natural rock systems often play an important role in determining the physical properties of minerals. In this study, I used a laser-heated diamond anvil cell (LHDAC), which made it possible to acquire precise data on a sample of Al-bearing Mg-perovskite under high pressure. I also used intense x-rays from a synchrotron radiation source. I investigated the pressure-volume EOS of orthorhombic perovskite possessing the pyrolytic (KLB-1 peridotite) composition up to a pressure of 80 GPa. To determine the elastic parameters, the P-V data were fitted to the Birch-Murnaghan equation of state. When Ko’ = 4 and Anderson’s EOS of Au was used, the value of bulk modulus, Ko, was determined to be 272(8) GPa. Although Mg-perovskite is the dominant phase in the Earth’s lower mantle, other phases, such as Ca-perovskite and magnesiowüstite, should be considered to understand the dynamics of the lower mantle. The EOS of KLB-1 peridotite, which is composed of Mg-perovskite, Ca-perovskite, and magnesiowüstite in the lower mantle, was determined using the reliable EOS of each phase. The BirchMurnaghan equation of state of KLB-1 peridotite was calculated at room temperature: volume of Vo = 22.80 cm/mol, a bulk modulus of Ko = 269 GPa, and its pressure derivative of K ’ = 4.0. The density of KLB-1 peridotite at lower mantle conditions was also calculated for various temperatures. The calculated densities were then compared with seismologically derived average density profiles of the mantle. For a mantle temperature is of 2000 K at the top of the lower mantle, the density of the KLB-1 peridotite composition was found to be 0.4% lower than the seismologically determined density of PREM. This density mismatch is very small compared with the uncertainties in the experimental measurements and analysis. Therefore, our study suggests that the KLB-1 peridotite seems to be the bulk composition of the upper part of the lower mantle. Mass-Independent Sulfur Isotope Records from the Hamersley Basin, Austrlaia S. ONO, D. RUMBLE, A. PAVLOV , J. EIGENBRODE, J. KASTING, J. LINDSAY, AND K. FREEMAN Geophysical Laboratory, Carnegie Institute of Washington, Washington DC 20015, USA (s.ono@gl.ciw.edu) LASP/University of Colorado, Duane Physics Building, 392 UCB Boulder, CO 80309 Astrobiology Research Center, the Pennsylvania State University, PA 16802 Johnson Space Center, Houston, TX 77058 |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | https://goldschmidtabstracts.info/2003/362.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
