New geological and geochemical data on the granitoids of the Uspensky massif in Southern Primorye

New geological, petrochemical, mineralogical, and geochemical data are presented on the Uspensky granitoid massif in Southern Primorye. The massif consists of the rocks of two associations: (1) the early association (103.3 ± 2.4 Ma) consisting of garnet-bearing biotite and two-mica granite-leucogranites and (2) the late association (99 ± 2 Ma) represented by biotite (±amphibole) granodiorites, melanogranites, and granites. The granitoids of both associations have moderate potassic alkalinity and elevated alumina contents but differ in the proportions of alumina, calcium, and alkalis. The garnet-bearing granite-leucogranites are characterized by the highest Rb, Th, and U contents and the lowest Sr, Ba, Hf, and Zr contents. The REE distribution patterns have a quasi-symmetric shape and deep Eu minimums. The melanogranites show higher Sr and Ba contents and, as granites, are characterized by asymmetric REE spectrums with an insignificant negative Eu anomaly. The porphyraceous granodiorites and granites are peculiar in their lowered Sr and Ba contents, while the granodiorites have lowered contents of K, REE, Zr, Hf, Th, and U; elevated Nb contents; and a distinctive Eu minimum.     

Line-profile microvariability in OB-star spectra: the Supergiant λ Cep (O6If(n))

We observed the bright O6If(n) supergiant λ Cep in 1997 with the 6-m optical telescope of the Special Astrophysical Observatory and in 2007 with the 1.8-m telescope of the Bohyunsan Optical Astronomy Observatory (South Korea). A total of 90 spectra of the star were acquired, with good time resolution (10 minutes), signal-to-noise ratios 150–300, and spectral resolutions of 45 000–60 000. We detected line-profile variations of H, HeI, and HeII lines. It is suggested that the detected variations are due to non-radial photospheric pulsations and the star’s rotation (rotational profile modulation).     

The Ol’cha gold-silver deposit: Tectonic setting,structure, and mineralogy

New data on the Paleozoic Ol’cha gold-silver deposit are given, including interpretation of its tectonic setting and mineralogical characteristization, the most complete to date. Strike-slip deformation is crucial for the formation of the ore field structure.     

New data on the structure of the sedimentary section on the Ita Mai Tai Guyot (Magellan Seamounts,Pacific Ocean)

The geological-prospecting investigations carried out by scientists from the Yuzhmorgeologiya State Scientific Center in the eastern segment of the Magellan Seamounts of the Pacific during the cruise of the R/V Gelendzhik in 2003–2010 brought new data on the topography of the Ita Mai Tai Guyot and its Lower Cretaceous-Pleistocene sedimentary section. The guyot is characterized by its complex irregular morphology with angular outlines being complicated by numerous relief mesoforms: spurs, scarps, and volcanic cones and domes. It is shown that the sedimentary cover was formed during a long period. The analysis of the organic macro- and microfaunal remains from the sedimentary rocks made it possible to define transgressive phases in the guyot’s development: the Albian-Cenomanian, the Late Campanian-Maastrichtian, and the late Paleocene-early Eocene. The oolitic limestone sequence recovered by DSDP Hole 202 is determined to be the Albian in age. Based on the original and published data, the geological development of the guyot was analyzed in comparison with other similar structures of the Magellan Seamounts.     

Fe- and Al-Rich metapelites of the Teiskaya Group, Yenisei Range: Geochemistry, protoliths, and the behavior of their material during metamorphism

The Fe- and Al-rich metapelite of the Teiskaya Group in the trans-Angara part of the Yenisei Range are characterized by variable P-T parameters of their metamorphism. Geochemical data on these rocks were used to reproduce the nature and composition of their protolith. The metapelites were determined to be redeposited and metamorphosed Precambrian weathering crusts of the kaolinite type, which were produced by the erosion of Archean rocks of predominantly acid (granitoid) composition in shallow-water continental-margin basins in a humid climate. These results are consistent with the results of the lithological-facies analysis and geodynamic reconstruction of the Precambrian geological evolution of complexes in the Yenisei range. Differences were revealed between the REE patterns in metapelites in various metamorphic zones caused by both the compositional heterogeneity of the protoliths and the prograde (in terms of pressure) mineral reactions of collision metamorphism with the predominant effects of various processes during different evolutionary stages.     

The thermal reaction of Venezuelan lateritic bauxites with glycerol

Goethite contained in lateritic bauxites or in artificial mineral admixtures is completely transformed into peculiar Fe-alkoxide compounds by reaction with glycerol at 245°C. Magnetic spinel oxides result from hydrolysis by boiling water of alkoxides obtained from the artificial admixtures. On the other hand, the production of magnetic spinel materials is not observed in alkoxides derived from natural lateritic samples. This may be caused by the high amount of Al substituting for Fe in these Venezuelan lateritic goethites.     

Solution thermochemistry of humic substances—I. Acid-base equilibria of humic acid

The technique of titration calorimetry has been used to characterize the acidic functional groups of humic acid. Both the concentrations of acidic functional groups and the thermodynamic parameters (pK_a, ΔH_a, etc.) for ionization of these functional groups were determined. The calculated values confirm the generally accepted opinion that humic acid contains both carboxyl and phenolic hydroxyl groups. Furthermore, at least one-third of the phenolic hydroxyl groups are not ortho to carboxyl groups and thus cannot participate in chelation of metal ions via salicylate-like complexing sites. The nature of the remaining two-thirds of the phenolic hydroxyl groups is still unknown.     

An ion-association model for PbO-SiO2 melts: interpretation of thermochemical,conductivity, and density data

We propose that within PbO-SiO₂ melts the component species PbO(1) and SiO₂(1) associate to form a lead orthosilicate complex [Pb₂SiO₄(1)] according to $\text{2PbO(1) + SiO}{}_2\text{(1)}\text{a}\text{?}\text{f Pb}{}_2\text{SiO}{}_4\text{(1)}$ The association constant (K) for the above reaction is near 30 at 900 and 1000°C On the premises that the enthalpy of the above reaction is the only contributor to the enthalpy of mixing and that three melt species [PbO(1), SiO₂(1), Pb₂SiO₄(1)] mix ideally (Raoult's Law obeyed), the partial molar properties and the integral mixing properties of the melt have been calculated and have been found to accurately reproduce the measured thermochemical data.The conductivity data and density data for PbO-SiO₂ melts have been calculated using the association model. The calculated data again are remarkably consistent with the experimental data.Other silicate-melt models have been reinterpreted and that of Toop and Samis is compatible with the proposed model. In fact the Toop and Samis model implicitly assumes the formation of orthosilicate species rather than condensed polymeric species.     

Paleocurrent and sedimentological studies in the Benue Trough,Nigeria

Paleocurrent analysis indicates an easterly and a westerly source, respectively, for the Cretaceous and Tertiary sediments in the middle and upper Benue Trough. Petrographic differentiation of the pre-Santonian and post-Santonian sediments is based on their feldspar contents. Petrographic evidence suggests that the Tertiary sediments are polycycled; this fact, coupled with the inferred westerly source, suggests that the present limits of the trough are not the paleolimits. Thus the rift boundary faults are probably further westward and eastward of the present trough margins.