Geological Conditions of the Formation and Dissociation of Gas Hydrates in the Sea of Okhotsk: Tectonic and Genetic Aspects

Lithology and Mineral Resources - The paper is dedicated to gas hydrate fields and active underwater gas seeps found in the Sea of Okhotsk. The study of geological conditions of the generation and...     

Synchrotron-excited luminescence of natural zircon

The luminescence properties of two single zircon crystals from kimberlite of Yakutia have been studied, excited by the DORIS HASYLAB synchrotron, Germany, within energy range from the visible to the soft X-ray region (5–25, 50–200, and 500–620 eV) at temperatures of 300 and 10 K. The luminescence spectra in the range of 2.5 to 6.0 eV and excitation spectra of the main bands have been examined, the physical nature of the luminescence centers has been discussed, and the luminescence properties of a crystal containing growth (radiation) structural defects and a crystal with the same impurities but annealed in air at 1200°C are compared. The zoned structure of the mineral has been considered and the value of the energy gap (E _g) in the mineral has been estimated at 7.1 eV. Two groups of luminescence bands caused by impurities of intrinsic (growth, radiation) nature (E _max = 2.1, 2.7–2.8, and 3.2–3.3 eV) and matrix luminescence (E _max = 4.4−4.7 and 5.4 eV) probably with the participation of excitons were distinguished on the basis of selective excitation of zircon with different synchrotron energies relative to the gap value (E _excit < E _g, E _excit ∼ E _g, and E _excit ≫ E _g). The short-lived component with a response time of 4 ns has been revealed in the afterglow of zircon in the region of 5.4 eV.     

Evaporation and energy balance estimates over a large inland lake in the Tibet-Himalaya

The process of evaporation from the lake surface is one of the main mechanisms in the energy and water budgets of the lake hydrologic cycle, and an essential component of the water balance especially for inland lakes. In this study, using routine meteorological data as input, a one-layer potential evaporation model was employed to simulate evaporation and energy fluxes over Lake Yamdrok Yumco, the largest high-elevation inland lake in the mountain area of the Tibet-Himalaya in China. Then, the calculation results were compared with the measured values from a big pan evaporator of 20 m² near the lake. The results show that the average annual input radiation flux R ^↓ is 128.2 W m⁻², the lake storage heat flux G is 19.4 W m⁻², the sensible heat flux H is 20.4 W m⁻² and the latent heat flux lE is 107.8 W m⁻². The R ^↓ and G exhibit similar seasonal variations. The lE reaches a maximum in October, lagging nearly 4 months behind the R ^↓ and the G, which indicates the large heat capacity of the lake. The simulated annual evaporation ranges from 1,113.2 to 1,429.1 mm and its mean value is 1,252.5 mm during 1961–2005. The simulated annual evaporation is in good agreement with the measured value, and the measured average lake temperature is as expected when compared with the measured lake surface temperature.     

The first data on the Early Proterozoic sialic basement in the eastern West Siberian Platform (studies of the Tyn&#x27;yar rhyolite–granite pluton)

Despite the long history of research, the presence of Precambrian complexes in the West Siberian basement has not been proven. The Tyn'yarskaya 100 and Tyn'yarskaya 101 wells were drilled in the Vakh–Elogui interfluve, in the eastern West Siberian Plate (eastern Khanty-Mansi Autonomous District). At a depth of 1790 m, they stripped a rhyolite extrusion, which graded into A-type alkali granitoids with rare-metal and REE mineralization (thorite, thorogummite, pitchblende, REE-carbonates, chevkinite, and others) downsection. This volcanoplutonic complex is Early Permian (K–Ar age, ～ 270 Ma; Rb–Sr age, 275.7 Ma; Sm–Nd age, 276 Ma; U–Pb age, 277 Ma). Some zircon grains from granites are much older (2049 ± 23 Ma, SHRIMP II), suggesting a relationship between the Early Permian granitic magma and the ancient matter. This might have been a granite-metamorphic basement, the partial melting of which produced the Tyn'yar rhyolite–granite body. The Sm–Nd model ages also suggest the participation of a Precambrian substratum in the formation of the rocks under study. Thus, it is quite possible that the Tyn'yar area is underlain by a Proterozoic (～ 2 Ga) sialic basement, which is an edge of the Siberian Platform thinned by Late Proterozoic–Early Paleozoic rifting and extension.     

青土湖地区9500a BP以来的环境变化研究

通过对青土湖地区ZY剖面的代用指标分析,研究了该区9500aBP以来的气候环境变化.在9500～6700aBP期间,剖面为风成砂沉积,平均粒径、磁化率、碳酸盐含量和C/N代用指标值均出现了的最低值,代表了湖泊干涸状态下强烈的风力搬运堆积,反映为一种暖干的古气候环境;6700～5800aBP期间,为碳酸盐粉砂质粘土沉积,代用指标的值均为高值,指示高水位、暖湿的古气候环境;5800～2700aBP为碳酸盐粉砂沉积,代用指标的值均表现为中等,代表了低水位状态下的碳酸盐沉积,反映夏季风减弱,区域降水量减少;2700～1100aBP期间为沼泽沉积,此时湖泊水量变化是以人为因素为主还是自然因素为主,需要进一步研究.     

Analysis of the “Ulitka” noise background as an anti-coincidence filter for the OGRAN gravitational-wave antenna

An analysis of experimental data from the ??Ulitka?? high-frequency gravitational-gradient meter installed in the underground Baksan Neutrino Observatory of the Russian Academy of Sciences is presented, focusing on the planned use of this instrument as an ??anti-coincidence filter?? for the OGRAN gravitational-wave antenna. The statistics of the Ulitka noise background over a year??s observing are analyzed, and compared with the background measured earlier when Ulitka was located on the territory of the Sternberg Astronomical Institute in Moscow. A reduction in the rate of occurrence of large nonthermal spikes is noted. We have found associations between earthquakes and excitations of the seismically isolated high-frequency mode of the longitudinal oscillations of Ulitka.