Let (Ω,
μ
) be a measurable space with a
σ
-finite continuous measure,
μ
(Ω) = ∞. A linear operator
T
:
L
1
(Ω) +
L
∞
(Ω) →
L
1
(Ω) +
L
∞
(Ω) is called a
Dunford–Schwartz operator
if ∥
T
(
f
)∥
1
≤ ∥
...f
∥
1
(respectively, ∥
T
(
f
)∥
∞
≤ ∥
f
∥
∞
) for all
f
∈
L
1
(Ω) (respectively,
f
∈
L
∞
(Ω)). If {
T
t
}
t
≥0
is a strongly continuous in
L
1
(Ω) semigroup of Dunford–Schwartz operators, then each operator
A
t
(
f
) =
1
t
∫
t
0
T
s
f
d
s
∈
L
1
Ω
,
f
∈
L
1
(Ω) has a unique extension to a Dunford–Schwartz operator, which is also denoted by
A
t
,
t
> 0. It is proved that in a completely symmetric space
E
(Ω) ⊈
L
1
of measurable functions on (Ω,
μ
) the means
A
t
converge strongly as
t
→ +∞ for each strongly continuous in
L
1
(Ω) semigroup {
T
t
}
t
≥0
of Dunford–Schwartz operators if and only if the norm ∥·∥
E
(Ω)
is order continuous.
Some F-rich granitic rocks show anomalous, nonchondritic ratios of Y/Ho, extreme negative Eu anomalies, and unusual, discontinuous, segmented chondrite-normalised plots of rare earth elements (REE). ...The effects of F-rich fluids have been proposed as one of the explanations for the geochemical anomalies in the evolved granitic systems, as the stability of nonsilicate complexes of individual rare earths may affect the fluid-melt element partitioning. The lanthanide tetrad effect, related to different configurations of 4f-electron subshells of the lanthanide elements, is one of the factors affecting such complexing behaviour. We present the first experimental demonstration of the decoupling of Y and Ho, and the tetrad effect in the partitioning of rare earths between immiscible silicate and fluoride melts. Two types of experiments were performed: dry runs at atmospheric pressure in a high-temperature centrifuge at 1100 to 1200°C, and experiments with the addition of H
2O at 700 to 800°C and 100 MPa in rapid-quench cold-seal pressure vessels. Run products were analysed by electron microprobe (major components), solution-based inductively coupled plasma mass spectrometry (ICP-MS) (REE in the centrifuged runs), and laser ablation ICP-MS (REE and Li in the products of rapid-quench runs). All the dry centrifuge runs were performed at super-liquidus, two-phase conditions. In the experiments with water-bearing mixtures, minor amounts of aqueous vapour were present in addition to the melts. We found that lanthanides and Y concentrated strongly in the fluoride liquids, with two-melt partition coefficients reaching values as high as 100–220 in water-bearing compositions. In all the experimental samples, two-melt partition coefficients of lanthanides show subtle periodicity consistent with the tetrad effect, and the partition coefficient of Y is greater than that of Ho. One of the mixtures also produced abundant fluorite (CaF
2) and cryolite (Na
3AlF
6) crystals, which enabled us to study fluorite-melt and cryolite-melt REE partitioning. REE concentrations in fluorite are high and comparable to those in the fluoride melt. However, fluorite-melt partition coefficients appear to depend mostly on ionic radii and show neither significant tetrad anomalies, nor differences in Y and Ho partitioning. In contrast, REE concentrations in cryolite are low (∼5–10 times lower than in the silicate melt), and cryolite-melt REE partitioning shows very strong tetrad and Y-Ho anomalies. Our results imply that Y-Ho and lanthanide tetrad anomalies are likely to be caused mainly by aluminofluoride complexes, and the tetrad REE patterns in natural igneous rocks can result from fractionation of F-rich magmatic fluids.
This experimental study examines relationships between alternative evolution paths of basaltic liquids (the so-called Bowen and Fenner trends), and silicate liquid immiscibility. Synthetic analogues ...of natural immiscible systems exhibited in volcanic glasses and melt inclusions were used as starting mixtures. Conventional quench experiments in 1 atm gas mixing furnaces proved unable to reproduce unmixing of ferrobasaltic melts, yielding instead either turbid, opalescent glasses, or crystallization of tridymite and pyroxenes. In contrast, experiments involving in situ high-temperature centrifugation at 1000g (g = 9·8 m/s2) did yield macroscopic unmixing and phase separation. Centrifugation for 3–4 h was insufficient to complete phase segregation, and resulted in sub-micron immiscible emulsions in quenched glasses. For a model liquid composition of the Middle Zone of the Skaergaard intrusion at super-liquidus temperatures of 1110–1120°C, centrifugation produced a thin, silicic layer (64·5 wt% SiO2 and 7·4 wt% FeO) at the top of the main Fe-rich glass (46 wt% SiO2 and 21 wt% FeO). The divergent compositions at the top and bottom were shown in a series of static runs to crystallize very similar crystal assemblages of plagioclase, pyroxene, olivine, and Fe–Ti oxides. We infer from these results that unmixing of complex aluminosilicate liquids may be seriously kinetically hampered (presumably by a nucleation barrier), and thus conventional static experiments may not correctly reproduce it. In the light of our centrifuge experiments, immiscibility in the Skaergaard intrusion could have started already at the transition from the Lower to the Middle Zone. Thus, magma unmixing might be an important factor in the development of the Fe-enrichment trend documented in the cumulates of the Skaergaard Layered Series.
A scientific drilling project in the Bushveld Igneous Complex in South Africa has been proposed to contribute to the following scientific topics of the International Continental Drilling Program ...(ICDP): large igneous provinces and mantle plumes, natural resources, volcanic systems and thermal regimes, and deep life. An interdisciplinary team of researchers from eight countries met in Johannesburg to exchange ideas about the scientific objectives and a drilling strategy to achieve them. The workshop identified drilling targets in each of the three main lobes of the Bushveld Complex, which will integrate existing drill cores with new boreholes to establish permanently curated and accessible reference profiles of the Bushveld Complex. Coordinated studies of this material will address fundamental questions related to the origin and evolution of parental Bushveld magma(s), the magma chamber processes that caused layering and ore formation, and the role of crust vs. mantle in the genesis of Bushveld granites and felsic volcanic units. Other objectives are to study geophysical and geodynamic aspects of the Bushveld intrusion, including crustal stresses and thermal gradient, and to determine the nature of deep groundwater systems and the biology of subsurface microbial communities.
In this chapter we describe in details the permeabilized cell and skinned fiber techniques and their applications for studies of mitochondrial function in vivo. The experience of more than 10 years ...of research in four countries is summarized. The use of saponin in very low concentration (50-100 microg/ml) for permeabilisation of the sarcolemma leaves all intracellular structures, including mitochondria, completely intact. The intactness of mitochondrial function in these skinned muscle fibers is demonstrated in this work by multiple methods, such as NADH and flavoprotein fluorescence studies, fluorescence imaging, confocal immunofluorescence microscopy and respiratory analysis. Permeabilized cell and skinned fiber techniques have several very significant advantages for studies of mitochondrial function, in comparison with the traditional methods of use of isolated mitochondria: (1) very small tissue samples are required; (2) all cellular population of mitochondria can be investigated; (3) most important, however, is that mitochondria are studied in their natural surrounding. The results of research by using this method show the existence of several new phenomenon--tissue dependence of the mechanism of regulation of mitochondrial respiration, and activation of respiration by selective proteolysis. These phenomena are explained by interaction of mitochondria with other cellular structures in vivo. The details of experimental studies with use of these techniques and problems of kinetic analysis of the results are discussed. Examples of large-scale clinical application of these methods are given.
The search for microinclusions of light platinoids (Ru and Pd) in samples of the Bushveld intrusion complex (South Africa) and corresponding examination are performed by scanning X-ray fluorescence ...analysis at the SR XRF experimental station with the help of the VEPP-3 storage ring at the Collective-Use Center “Siberian Synchrotron and Terahertz Radiation Center” based at the Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences. The samples are prepared as plane parallel ground plates 2 mm in thickness. First, one-dimensional scanning with a wide beam (1 × 20 mm) of monochromatic radiation with an excitation energy of 20 and 30 keV is performed. Then, the region with higher contents of light platinoids is two-dimensionally scanned with a beam (30 × 45 μm) which is focused with a polycapillary lens. Sample surface mapping enables identification of a few individual particles 50–100 μm in size with a high Pd content. The potential for micro-XAFS investigation of an individual particle is demonstrated.
•The rocks crystallized from 18O- and D-depleted magma.•The rocks are products of fractional crystallization from a single parental magma.•Hydrothermal processes were responsible for the change in ...δ18O values.
The Belaya Zima alkaline–carbonatite complex in the East Sayan Mountains, Russia, is a multiphase concentric intrusion, which comprises diverse alkaline silicate rocks and carbonatites. Melteigites are the earliest products of crystallization and they are followed by ijolites–urtites, nepheline syenites, and finally, calcite, calcite–dolomite and ankerite carbonatites. In this paper, we present new geochronological data (Ar–Ar method), chemical and stable isotope (H, C and O) compositions of the main rock-forming minerals in carbonatites and the silicate rocks of the complex. The Ar–Ar dating of phlogopite from ankerite carbonatites is consistent with the age of syenite emplacement and implies that the silicate rocks and carbonatites are likely to be comagmatic. The evolutionary trends of pyroxene, fluorapatite, amphibole and phlogopite are consistent with fractional crystallization from a single parental magma. Primary Nb mineralization is represented by pyrochlore, whereas columbite-(Fe) is a replacement product of pyrochlore at the post magmatic, hydrothermal stage. At that stage, interaction of calcite carbonatites with hydrothermal fluids resulted in the formation of hydrothermal paragenesis comprising dolomite–ankerite, monazite-(Ce), ancylite-(Ce), minerals of burbankite group and Ca–REE fluorcarbonates. The hydrothermal processes were also responsible for cation leaching from pyrochlore, the replacements of phlogopite by tetraferriphlogopite and early Ca-rich pyroxene by aegirine. The stable isotope data suggest that the rocks crystallized from a 18O-depleted magma. Shifts toward higher δ18O values relative to the primary compositions are commonly observed in minerals from carbonatites, which is attributed to hydrothermal processes.
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