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1.
The distribution of integrated resources of large and superlarge deposits (LSLDs) of rare earth elements (REEs) is compared to the current model of supercontinent cyclicity during Earth’s evolution. It is found that REE LSLDs are related predominantly to igneous complexes (carbonatite, nepheline syenites, syenite-alkaline granites, subalkaline granites), which are often additionally enriched in the hypergenic zone. A certain part of the resources is concentrated in independent hypergenic formations represented by placers and ion-adsorbed clays. Each supercontinent cycle—Kenoran, Columbian, Rodinian, Pangean, and Amasian—is expressed in the REE metallogeny in particular way: we revealed significant intercycle variations in the amount of REE LSLDs, the variety of their types, total accumulated resources, and some other characteristics. 相似文献
2.
Atkin E. V. Bulatov V.L. Vasiliev O. A. Voronin A. G. Gorbunov N. V. Grebenyuk V. M. Dorokhov V. A. Karmanov D. E. Kovalev I.M. Kudryashov I. A. Kurganov A.A. Merkin M. M. Panov A.D. Podorozhny D. M. Polkov D. A. Porokhovoi S. Yu. Sveshnikova L. G. Tkachev L.G. Tkachenko A. V. Turundaevskiy A. N. Filippov S. B. Shumikhin V. V. 《Astronomy Reports》2019,63(1):66-78
Astronomy Reports - Some results of studies of cosmic rays obtained during the NUCLEON space experiment in 2015–2017 are presented. This experiment was intended for direct measurements of the... 相似文献
3.
E. B. Sal’nikova A. M. Larin S. Z. Yakovleva A. B. Kotov V. A. Glebovitskii A. V. Tkachev I. V. Anisimova Yu. V. Plotkina B. M. Gorokhovskii 《Doklady Earth Sciences》2011,441(1):1479-1483
The U-Pb age of the manganotantalite from rare-metal pegmatites of the Vishnyakovskoe deposit (East Sayan Belt) has been assessed
at 1838 ± 3 Ma. The acquired data indicate the pegmatites of this deposit and associated granites of the Sayan complex belong
to the postcollision South Siberian igneous belt (1.88–1.84 Ga), which stretches along the southwestern frame of the Siberian
Craton by more than 2500 km, from the Yenisei Ridge to the Aldan Shield. Formation of this igneous belt is related to joining
(starting from about 1.9 Ga BP) of the series of continental microplates and island arcs to the Siberian Craton; this led
to final stabilization of the craton at about 1.8 Ga BP. 相似文献
4.
Yu Ye Joseph R. Smyth Steven D. Jacobsen Wendy R. Panero David A. Brown Tomoo Katsura Yun-Yuan Chang Joshua P. Townsend Przemyslaw Dera Sergey Tkachev Cayman Unterborn Zhenxian Liu Céline Goujon 《Contributions to Mineralogy and Petrology》2013,166(5):1375-1388
MgSiO3 akimotoite is stable relative to majorite-garnet under low-temperature geotherms within steeply or rapidly subducting slabs. Two compositions of Mg–akimotoite were synthesized under similar conditions: Z674 (containing about 550 ppm wt H2O) was synthesized at 22 GPa and 1,500 °C and SH1101 (nominally anhydrous) was synthesized at 22 GPa and 1,250 °C. Crystal structures of both samples differ significantly from previous studies to give slightly smaller Si sites and larger Mg sites. The bulk thermal expansion coefficients of Z674 are (153–839 K) of a 1 = 20(3) × 10?9 K?2 and a 0 = 17(2) × 10?6 K?1, with an average of α 0 = 27.1(6) × 10?6 K?1. Compressibility at ambient temperature of Z674 was measured up to 34.6 GPa at Sector 13 (GSECARS) at Advanced Photon Source Argonne National Laboratory. The second-order Birch–Murnaghan equation of state (BM2 EoS) fitting yields: V 0 = 263.7(2) Å3, K T0 = 217(3) GPa (K′ fixed at 4). The anisotropies of axial thermal expansivities and compressibilities are similar: α a = 8.2(3) and α c = 10.68(9) (10?6 K?1); β a = 11.4(3) and β c = 15.9(3) (10?4 GPa). Hydration increases both the bulk thermal expansivity and compressibility, but decreases the anisotropy of structural expansion and compression. Complementary Raman and Fourier transform infrared (FTIR) spectroscopy shows multiple structural hydration sites. Low-temperature and high-pressure FTIR spectroscopy (15–300 K and 0–28 GPa) confirms that the multiple sites are structurally unique, with zero-pressure intrinsic anharmonic mode parameters between ?1.02 × 10?5 and +1.7 × 10?5 K?1, indicating both weak hydrogen bonds (O–H···O) and strong OH bonding due to long O···O distances. 相似文献
5.
Przemyslaw Dera Jawad Nisar Rajeev Ahuja Sergey Tkachev Vitali B. Prakapenka 《Physics and Chemistry of Minerals》2013,40(2):183-193
The nickel arsenide (B81) and related crystal structures are among the most important crystallographic arrangements assumed by Fe and Ni compounds with light elements such as Si, O, S, and P, expected to be present in planetary cores. Despite the simple structure, some of these materials like troilite (FeS) exhibit complex phase diagrams and rich polymorphism, involving significant changes in interatomic bonding and physical properties. NiP (oP16) represents one of the two principal structure distortions found in the nickel arsenide family and is characterized by P–P bonding interactions that lead to the formation of P2 dimers. In the current study, the single-crystal synchrotron X-ray diffraction technique, aided by first principles density functional theory (DFT) calculations, has been applied to examine the compression behavior of NiP up to 30 GPa. Two new reversible displacive phase transitions leading to orthorhombic high-pressure phases with Pearson symbols oP40 and oC24 were found to occur at approximately 8.5 and 25.0 GPa, respectively. The oP40 phase has the primitive Pnma space group with unit cell a = 4.7729(5) Å, b = 16.6619(12) Å, and c = 5.8071(8) Å at 16.3(1) GPa and is a superstructure of the ambient oP16 phase with multiplicity of 2.5. The oC24 phase has the acentric Cmc21 space group with unit cell a = 9.695(6) Å, b = 5.7101(9) Å, and c = 4.7438(6) Å at 28.5(1) GPa and is a superstructure of the oP16 phase with multiplicity of 1.5. DFT calculations fully support the observed sequence of phase transitions. The two new phases constitute logical next stages of P sublattice polymerization, in which the dilution of the P3 units, introduced in the first high-pressure phase, decreases, leading to compositions of Ni20(P3)4(P2)4 and Ni12(P3)4, and provide important clues to understanding of phase relations and transformation pathways in the NiAs family. 相似文献
6.
Doklady Earth Sciences - Niobium metallogeny over the course of geological history has been considered on the basis of data from 45 largest deposits in the world belonging to any of three... 相似文献
7.
The distribution of integrated resources of large and superlarge mineral deposits (LSLDs) of silver, where the main part of industrially recoverable silver reserves is concentrated, is compared with the existing model of supercontinent cyclicity over the geological history of the Earth. It is found that each supercontinent cycle (Kenoran, Columbian, Rodinian, Pangean, and Amasian) is particularly expressed in the silver metallogeny. The significant intercycle variations in the numbers of LSLDs, diversity of types of these deposits, accumulated resources, mean tenors of silver in ores, and some other numerically expressible characteristics are revealed. These variations correlate with a number of geohistorical changes in the conditions under which endogenous and exogenous geological processes run. 相似文献
8.
New Estimates of the Merger Rate of Primordial Black Holes with Allowance for Clustering Dark Matter
Astronomy Letters - The merger rate of primordial black holes (PBHs) is numerically estimated by taking into account the gravitational interaction of PBHs with clustering cold dark matter (DM). The... 相似文献
9.
Joshua P. Townsend Yun-Yuan Chang Xiaoting Lou Miguel Merino Scott J. Kirklin Jeff W. Doak Ahmed Issa Chris Wolverton Sergey N. Tkachev Przemyslaw Dera Steven D. Jacobsen 《Physics and Chemistry of Minerals》2013,40(5):447-453
At ambient conditions, witherite is the stable form of BaCO3 and has the aragonite structure with space group Pmcn. Above ~10 GPa, BaCO3 adopts a post-aragonite structure with space group Pmmn. High-pressure and high-temperature synchrotron X-ray diffraction experiments were used to study the stability and equation of state of post-aragonite BaCO3, which remained stable to the highest experimental P–T conditions of 150 GPa and 2,000 K. We obtained a bulk modulus K 0 = 88(2) GPa with $K'$ = 4.8(3) and V 0 = 128.1(5) Å3 using a third-order Birch-Murnaghan fit to the 300 K experimental data. We also carried out density functional theory (DFT) calculations of enthalpy (H) of two structures of BaCO3 relative to the enthalpy of the post-aragonite phase. In agreement with previous studies and the current experiments, the calculations show aragonite to post-aragonite phase transitions at ~8 GPa. We also tested a potential high-pressure post–post-aragonite structure (space group C222 1 ) featuring four-fold coordination of oxygen around carbon. In agreement with previous DFT studies, ΔH between the C222 1 structure and post-aragonite (Pmmn) decreases with pressure, but the Pmmn structure remains energetically favorable to pressures greater than 200 GPa. We conclude that post–post-aragonite phase transformations of carbonates do not follow systematic trends observed for post-aragonite transitions governed solely by the ionic radii of their metal cations. 相似文献
10.