The Strel’tsovka uranium district: Isotopic geochronological (U-Pb,Rb-Sr,Sm-Nd) characterization of granitoids and their place in the formation history of uranium deposits

An isotopic geochronological study of Russia’s largest Strel’tsovka uranium district has been carried out. Polychronous granite generation, which determined the structure of the pre-Mesozoic basement, had important implications for the formation of volcanotectonic structural elements bearing economic uranium mineralization. The study of U-Pb, Rb-Sr, and Sm-Nd isotopic systems of whole-rock samples and minerals of granitic rocks allowed us to estimate the deportment of these systems in spatially conjugated granite-forming and hydrothermal processes differing in age and gave grounds for revising the age of granites pertaining to the Urulyungui Complex and refining the age of the Unda Complex.     

Set-asides for carbon sequestration: implications for permanence and leakage

This paper examines the potential role of forest set-asides in global carbon sequestration policy. While set asides that protect forests from timber harvests and land-use conversion may alleviate concerns with permanence, and they may provide large ancillary environmental benefits, they may also lead to large leakage. This paper uses a global land use and forestry model to examine the efficiency of three crediting schemes for set-asides. The results show that if set-asides are integrated into a global forestry carbon sequestration program that includes a wide range of other management options, then 300 million hectares of land would be set-aside, and up to 128 Pg C could be sequestered in global forests by 2105. Under alternative policies that focus exclusively on set-asides, more forestland can be set-asides, up to 3.2 billion hectare, but these policies invite large leakage in the near-term, and in the long-run, they less net carbon is removed from the atmosphere. Specifically, leakage is estimated to be 47–52%, depending on the policy, and by the end of the century, up to 17% less carbon will be sequestered in all forests.     

Cosmogenic radiocarbon as a means of studying solar activity in the past

A series of yearly data on the concentration of radioactive carbon ¹⁴C in tree rings measured at the Tbilisi State University in 1983–1986 and covering the time interval 1600–1940 is statistically analyzed. We find evidence for a 22-year cyclicity in the intensity of Galactic cosmic rays (GCRs) during the Maunder minimum of the solar activity (1645–1715), testifying that the solar dynamo mechanism continued to operate during this epoch. Variations of Δ¹⁴C on timescales of tens and hundreds of years correlate well with the corresponding variations of the GCR intensity and solar activity, making radiocarbon a reliable source of information on long-timescale variations of solar activity in the past. Short-timescale (<30 years) fluctuations of Δ¹⁴C may be appreciably distorted by time variations not associated directly with solar activity; probable origins of this distortion are discussed.     

Aklimaite, Ca4[Si2O5(OH)2](OH)4 · 5H2O, a new natural hydrosilicate from Mount Lakargi, the Northern Caucasus, Russia

A new mineral aklimaite, Ca₄[Si₂O₅(OH)₂](OH)₄ · 5H₂O, has been found near Mount Lakargi, Upper Chegem caldera, Kabardino-Balkaria, the Northern Caucasus, Russia, in the skarnified limestone xenolith in ignimbrite. This hydrothermal mineral occurs in a cavity of altered larnite skarn and is associated with larnite, calcium humite-group members, hydrogarnets, bultfonteinite, afwillite, and ettringite. Aklimaite forms transparent, colorless (or occasionally with pinkish tint) columnar or lath-shaped crystals up 3 × 0.1 × 0.01 mm in size, flattened on {001} and elongated along {010}; they are combined in spherulites. The luster is vitreous; the cleavage parallel to the {001} is perfect. D _calc = 2.274 g/cm³. The Mohs’ hardness is 3–4. Aklimaite is optically biaxial, negative, 2V _meas > 70°, 2V _calc = 78°, α = 1.548(2), β = 1.551(3), γ = 1.553(2). The IR and Raman spectra are given. The chemical composition (wt %, electron microprobe) is as follows: 0.06 Na₂O, 0.02 K₂O, 45.39 CaO, 0.01 MnO, 0.02 FeO, 24.23 SiO₂, 0.04 SO₃, 3.22 F, 27.40 H₂O_(calc.), ?1.36 -O=F₂; the total is 99.03. The empirical formula calculated on the basis of 2Si apfu with O + OH + F = 16 is as follows: (Ca_4.02Na_0.01)_Σ4.03[Si_2.00O_5.07(OH)_1.93][(OH)_3.16F_0.84] _Σ4.00 · 5H₂O. The mineral is monoclinic, space group C2/m, a = 16.907(5), b = 3.6528(8), c = 13.068(4) Å, β = 117.25(4)·, V= 717.5(4) ų, Z = 2. Aklimaite is representative of the new structural type, the sorosilicate with disilicate groups [Si₂O₅(OH)₂]. The strongest reflections in the X-ray powder patterns [d, Å (hkl)] are: 11.64(100)(001), 2.948(32)(310, 203), 3.073(20) ( $\bar 404$ , $\bar 311$ ), 2.320(12)(005, 510), 2.901 (11)(004), 8.30(10) $\left( {\bar 201} \right)$ . The type specimen is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.     

Determination of the distribution of size of irregularly shaped particles from laser diffractometer measurements

The formal stereological transformation equation for particle sieve size distribution from measurements in lower dimensional spaces is applied to laser diffractometer measurements. The transformation function for iron ore particles is measured experimentally, and modeled. The solution is tested against the measured transformation function data as well as synthetic composite distributions of the original sample. The natural size distribution of a sample taken from a grinding circuit stream was measured by a combination of standard sieving and cyclosizer, and the result is compared to the transformed size distribution calculated from laser diffractometer measurements. The stereological transformation technique performed well in all cases.     

Numerical analysis of the transformation of tsunami waves in the south crimea shelf area

The paper analyses the transformation of tsunami-type solitary waves, propagating from the abyssal part of the Black Sea towards its shelf zone. The study is performed by solving numerically unidimensional non-linear equations for non-dispersive long waves, using the finite-difference slope and shelf, with the full wave reflection prescribed at a 10 m depth contour. The non-linearity of the process is shown to throughly impact the reflection of waves by the shore and the shape of the reflected wave. Tsunami wave heights have been seen to increase by several times in the Black sea shelf area. Translated by Vladimir A. Puchkin.     

Incrustations and fumarolic condensates at kilauea volcano, Hawaii: field, drill-hole and laboratory observations

Hawaiian volcanoes characteristically have but few of the many types of minerals found in incrustations of other volcanic areas. In Hawaii sulfates resulting from air oxidation of volatiles predominate, and fluorides produced during rock alteration by fumarolic gases are prominent. Halides are generally found where reducing conditions exist in fumaroles and lava lake drill holes. The most common mineral types are sulfur, opaline silica, gypsum, ralstonite, and thenardite. Minerals from the same deposit are found to vary markedly in the content of the less abundant components. Condensates from vapor issuing from fumaroles show little quantitative relationship in component content to incrustations deposited at the same fumaroles. It is believed that an energetically favorable isomorphic substitution of some elements in the crystal lattice of a depositing mineral may lead to the build-up of a high concentration of an element from a lean vapor. Equilibrium calculations applied to condensate studies give a good quantitative approximation to the concentrations of the elements found in natural systems, but when applied to incrustations they serve only to indicate general compositional relations. Laboratory studies have shown the important role of chlorides in metal transfer in the gas phase in high-temperature aqueous systems, but only in the absence of oxygen. These studies also demonstrated the important role of HF in rock alteration and in the transfer of silica.     

Variations in statistical parameters of the <Emphasis Type="Italic">NmF</Emphasis>2 winter anomaly with latitude and solar activity

The maximal R ratios of the winter-to-summer NmF2 values of each ionosonde are calculated for a specified UT under daytime quiet geomagnetic conditions and at approximately equal levels of solar activity, based on foF2 measurement data of 98 ionosondes at mid- and low geomagnetic latitudes of the Northern and Southern hemispheres for 1957–2009. The P(R > 1) conditional probability of NmF2 winter anomaly observations, as well as the most probable RMP and average <R> of R values are calculated for low, moderate, and high solar activity on the base of foF2 measurements during the periods December 22 ± 30 days and June 21 ± 30 days. Variations in P(R > 1), RMP, and 〈R〉 with latitude and solar activity are analyzed.     

Storm surge mitigation through vegetation canopies

The paper of Reid and Whitaker (1976) on the effects of a vegetation canopy on flow of water is re-examined. Their assumptions on the equality of various drag coefficients are replaced by more realistic calculations. A new method for calculating wind stress on water is presented for the case when the vegetation extends above the water surface.For the case of vanishingly small water depth, it is shown that the horizontal stress is approximately constant in the vertical. This results in a diagnostic relationship for the water current as a function of the wind stress and bottom roughness.A new expression for the vertically averaged frictional force per unit mass is derived on the assumption that the friction velocity varies linearly with height. The vertical rate of change of friction velocity depends on the mean water current, the wind stress, the bottom roughness, and the water depth. This work has a possible application in the mitigation of storm surges.     

Relationship of atmospheric ozone profiles to solar magnetic activity

The observed relationship between atmospheric vorticity variations and solar magnetic sector boundary passages is examined for a possible connection via ionization changes affecting ozone distributions. A superposed epoch analysis was performed on Umkehr distributions for 18 years from Arosa, Switzerland, with use of more than 500 solar sector boundary passages as keyday zero. No significant responses are observed in any Umkehr level or in total observed ozone amounts. Further analyses on shorter records for Belsk, Poland, and Hohenpeissenberg, West Germany, corroborate these results. Another analysis for Arosa with about 100 type IV solar flares as keyday zero also shows no definitive trend. It is concluded that ozone distribution changes cannot be the primary causative mechanism for vorticity variations.Journal Paper No. J-8838 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project No. 1852.