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51.
The solar wind at larger distances is known to be a multicomponent plasma. The different components, solar ions, pick-up ions, and anomalous ions, are without collisional coupling but they are all coupled to the intrinsic wave turbulences by nonlinear wave-particle interactions. Since quite a long time it is not understood why dynamical processes associated with the loading of the primary solar wind by secondary pick-up ions neither lead to a recognizable heating nor to a deceleration of the solar wind at larger distances. While the inefficient heating seems to be explained by the fact that pick-up ions do not assimilate quickly enough to the solar wind distribution function, the unobservable deceleration of the distant solar wind always remained mysterious. Different from all theoretical approaches up to now, here we intend to show that the wave-induced pick-up ion pressure has to be introduced into the equations of motion in an adequate non-polytropic form to correctly describe the multicomponent plasma dynamics. If this is done it becomes clear that the deceleration of the solar wind is considerably reduced or even vanishing. 相似文献
52.
Rainer?ThomasEmail author Hans-Jürgen?F?rster Karen?Rickers James?D.?Webster 《Contributions to Mineralogy and Petrology》2005,148(5):582-601
Quartz crystals from topaz–zinnwaldite–albite granites from Zinnwald (Erzgebirge, Germany) contain, in addition to primary and secondary fluid inclusions (FIs), abundant crystalline silicate-melt inclusions (MIs) with diameters up to 200 m. These MIs represent various stages of evolution of a highly evolved melt system that finally gave rise to granite-related Sn–W mineralization. The combination of special experimental techniques with confocal laser Raman-microprobe spectroscopy and EMPA permits precise measurement of elevated contents of H2O, F, and B in re-homogenized MIs. The contents of H2O and F were observed to increase from 3 to 30 and 1.9 to 6.4 wt%, respectively, during magma differentiation. However, there is a second MI group, very rich in H2O, with values up to 55 wt% H2O and an F concentration of approximately 3 wt%. Ongoing enrichment of volatiles H2O, F, B, and Cl and of Cs and Rb can be explained in terms of magma differentiation triggered by fractional crystallization and thus, is suggested to reflect elemental abundances in natural magmas, and not boundary-layer melts. Partitioning between melt and cogenetic fluids has further modified the magmatic concentrations of some elements, particularly Sn. The coexistence of two types of MIs with primary FIs indicates fluid saturation early in the history of magma crystallization, connected with a continuous sequestration of Sn, F, and B. The results of this study provide additional evidence for the extraordinary importance of the interplay of H2O, F, and B in the enrichment of Sn during magma differentiation by decreasing the viscosity of and increasing the diffusivity in the melts as well as by the formation of various stable fluoride complexes in the melt and coexisting fluid.
相似文献
Rainer ThomasEmail: Phone: +49-331-2881474 |
53.
Daniel?E.?HarlovEmail author Richard?Wirth Hans-Jürgen?F?rster 《Contributions to Mineralogy and Petrology》2005,150(3):268-286
In a series of timed experiments, monazite inclusions are induced to form in the Durango fluorapatite using 1 and 2 N HCl
and H2SO4 solutions at temperatures of 300, 600, and 900°C and pressures of 500 and 1,000 MPa. The monazite inclusions form only in
reacted areas, i.e. depleted in (Y+REE)+Si+Na+S+Cl. In the HCl experiments, the reaction front between the reacted and unreacted
regions is sharp, whereas in the H2SO4 experiments it ranges from sharp to diffuse. In the 1 N HCl experiments, Ostwald ripening of the monazite inclusions took
place both as a function of increased reaction time as well as increased temperature and pressure. Monazite growth was more
sluggish in the H2SO4 experiments. Transmission electron microscopic (TEM) investigation of foils cut across the reaction boundary in a fluorapatite
from the 1 N HCl experiment (600°C and 500 MPa) indicate that the reacted region along the reaction front is characterized
by numerous, sub-parallel, 10–20 nm diameter nano-channels. TEM investigation of foils cut from a reacted region in a fluorapatite
from the 1 N H2SO4 experiment at 900°C and 1,000 MPa indicates a pervasive nano-porosity, with the monazite inclusions being in direct contact
with the surrounding fluorapatite. For either set of experiments, reacted areas in the fluorapatite are interpreted as replacement
reactions, which proceed via a moving interface or reaction front associated with what is essentially a simultaneous dissolution–reprecipitation
process. The formation of a micro- and nano-porosity in the metasomatised regions of the fluorapatite allows fluids to permeate
the reacted areas. This permits rapid mass transfer in the form of fluid-aided diffusion of cations to and from the growing
monazite inclusions. Nano-channels and nano-pores also serve as sites for nucleation and the subsequent growth of the monazite
inclusions. 相似文献