Partitioning of Eu between augite and a highly spiked martian basalt composition as a function of oxygen fugacity (IW-1 to QFM): Determination of Eu2+/Eu3+ ratios by XANES

2010 ◽  
Vol 95 (2-3) ◽  
pp. 410-413 ◽  
Author(s):  
J.M. Karner ◽  
J.J. Papike ◽  
S.R. Sutton ◽  
P.V. Burger ◽  
C.K. Shearer ◽  
...  
Keyword(s):  
Oxygen Fugacity ◽  
Basalt Composition

The aeromagnetic mineralogy of igneous rocks

1979 ◽  
Vol 16 (6) ◽  
pp. 1281-1293 ◽  
Author(s):  
Stephen E. Haggerty
Keyword(s):  
Oxygen Fugacity ◽  
Igneous Rocks ◽  
Magnetic Minerals ◽  
Temperature Oxidation ◽  
Sulfur Fugacity ◽  
Rock Types ◽  
Magnetic Carriers ◽  
Highly Sensitive ◽  
Magnetic Signatures

Magnetic minerals in igneous rocks are dominated by phases in the system FeO–Fe2O3–TiO2 and the system Fe–Ni–S. Complex solid solutions within both systems yield divergent magnetic signatures, which are dependent on primary mineralogy, on deuteric cooling, and on post-depositional alteration of the host rock. Intrinsic parameters such as temperature, oxygen fugacity, and sulfur fugacity, have effective buffering capacities, which influence the ratios Fe2+:Fe3+; (Fe2+ + Fe3+):Ti; Fe:S; and (Fe + Ni):S. These ratios are highly sensitive to environmental conditions and correlate with magnetic property measurements. In addition, bulk chemistry plays a major role, and for igneous rocks a striking pattern emerges in which oxygen fugacity is related to SiO2 (i.e., from basic to acid suites) regardless of total pressure. Acidic suites (granites and rhyolites) are more highly oxidized than basic suites (gabbros and basalts); hence. ulvöspinel (Fe2TiO4)-rich and ilmenite (FeTiO3)-rich constituents are characteristic of the latter, whereas magnetite (Fe3O4)-rich and hematite (αFe2O3)-rich components are typical of the former as primary precipitated oxides. Deep-seated equilibration results in exsolution and in low-intensity states of oxidation, and this is in contrast to extrusive suites in which intense states of high temperature oxidation are prevalent. Olivine decomposition in extrusive rocks, and the formation of magnetite solid-solution members in plagioclase and pyroxene in plutonic rocks, yield single domain particles, which in some instances are the dominant magnetic carriers. Sulfide minerals are rare in continental extrusive suites, are more abundant in oceanic basalts and in hypabyssal minor intrusives, and peak in plutonic environments.Within the context of deep crustal magnetic anomalies, and in the determination of Curie isotherms, it is proposed that the primary and secondary mineralogy of plutonic ultramafic rocks be carefully re-evaluated based on current models of serpentinization. Metallic iron and metal alloys of Fe–Ni–Co–Cu are widely recognized in these rock types, and because these minerals have elevated Curie temperatures (620–1100 °C) the depth detection limits of aeromagnetic anomalies need not be constrained by the accepted value of 580 °C, the Curie temperature of magnetite.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

Distance to SN 1987A and the LMC

1999 ◽  
Vol 190 ◽  
pp. 549-554
Author(s):  
Nino Panagia
Keyword(s):  
Angular Size ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Distance Modulus ◽  
Absolute Size ◽  
Sn 1987A

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.

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