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561.
Maria Aldona Augustyniak-Jabłokow Yurii V. Yablokov Bartłomiej Andrzejewski Wojciech Kempiński Szymon Łoś Krzysztof Tadyszak Mikhail Y. Yablokov Valentin A. Zhikharev 《Physics and Chemistry of Minerals》2010,37(4):237-247
The X-band EPR and magnetic susceptibility in the temperature range 4.2–300 K study of the shungite-I, natural nanostructured
material from the deposit of Shunga are reported. Obtained results allow us to assign the EPR signal to conduction electrons,
estimate their number, N
P, and evaluate the Pauli paramagnetism contribution to shungite susceptibility. A small occupation (~5%) of the localized
nonbonding π states in the zigzag edges of the open-ended graphene-like layers and/or on σ (sp
2+x
) orbitals in the curved parts of the shungite globules has been also revealed. The observed temperature dependence of the
EPR linewidth can be explained by the earlier considered interaction of conduction π electrons with local phonon modes associated
with the vibration of peripheral carbon atoms of the open zigzag-type edges and with peripheral carbon atoms cross-linking
different nanostructures. The relaxation time T
2 and diffusion time T
D are found to have comparable values (2.84 × 10−8 and 1.73 × 10−8 s at 5.2 K, respectively), and similar dependence on temperature. The magnetic measurements have revealed the suppression
of orbital diamagnetism due to small amount of large enough fragments of the graphene layers. 相似文献
562.
S. Mazur P. Aleksandrowski K. Turniak L. Krzemiński K. Mastalerz A. Górecka-Nowak L. Kurowski P. Krzywiec A. Żelaźniewicz M. C. Fanning 《International Journal of Earth Sciences》2010,99(1):47-64
The Carboniferous foreland basin of western Poland contains a coherent succession of late Viséan through Westphalian turbidites
derived from a uniform group of sources located within a continental magmatic arc. Detrital zircon geochronology indicates
that two main crustal components were present in the source area of Namurian A sediments. They represent Late Devonian and
Early Carboniferous ages, respectively. The detritus from Westphalian D beds is much more diversified and contains admixture
of Late Carboniferous zircons suggesting rapid unroofing of Variscan igneous intrusions in the hinterland between Namurian
A and Westphalian D times. Tectonic repetitions of tens of metres thick fault-bounded stratigraphic intervals, recorded in
several wells, provide evidence for compressional regime that occurred in the SW part of the Carboniferous basin not earlier
than during the Westphalian C and produced NW–SE trending folds, concordant with the structural grain of the adjacent, NE
part of the Bohemian Massif. 相似文献
563.
Experimental metasomatism of monazite and xenotime: mineral stability, REE mobility and fluid composition 总被引:2,自引:0,他引:2
Callum J. Hetherington Daniel E. Harlov Bartosz Budzyń 《Mineralogy and Petrology》2010,99(3-4):165-184
In this study a Th-bearing monazite from a Brazil beach sand, a low Th monazite from a Malawi carbonatite, and a xenotime from a pegmatite in northern Pakistan were experimentally metasomatised in a series of common metamorphic and igneous fluids at 600°C/500 MPa and 900°C/1000 MPa. Fluids included H2O, NaCl, and KCl brines, CaF2?+?H2O, 1m and 2m HCl, 1m and 2m H2SO4, 1m NaOH, and Na2Si2O5?+?H2O. The monazite show a variety of responses to the fluids ranging from no reaction (KCl?+?H2O) to small compositional changes and partial replacement of the monazite grain rim by Th-enriched monazite in the NaOH and (Na2Si2O5?+?H2O) experiments respectively. The other acid and brine fluids induced varying degrees of partial dissolution in the monazite and xenotime, but no compositional alteration. Partial replacement of monazite grain rims by Th-enriched monazite occurred only in the alkaline fluids as the result of a coupled dissolution-reprecipitation process. 相似文献