Based on a comprehensive analysis of kimberlite pipes of Angola, including the near surface structural setting, deep lithospheric structure, pipe morphology and emplacement, mineralogical and petrographic features, diamond characteristics and locations of secondary deposits four geographical regions have been outlined within Angola representing four types of diamond bearing potential. These areas include high diamond bearing potential pipes, possible potential, no potential, and unclear potential areas. It was found that the depth of magmatism and diamond potential of kimberlites increases from the Atlantic coast in southwestern Angola into the continent in the north-easterly direction. Areas prospective for the discovery of new primary diamond deposits have been identified.
The present article is written in response to the recent call of the United Nations for the enhanced international cooperation of different countries on global geodesy to build the Global Geodetic Reference Frame (GGRF). It reviews historical landmarks in the development of the State Geodetic Reference Frame on the territory of Russia over the last two centuries. It discusses major steps in creating the Russian terrestrial reference frame by both the ground-based and space geodesy methods relying upon the satellite observation techniques. Currently the State Geodetic Reference Frame undergoes a radical improvement in order to effectively implement the potential of modern satellite technologies through the use of the Global Navigation Satellite Systems (GNSS). We outline the current status of the National Geodetic Network in Russia, its hierarchical structure and accuracy. We pay a particular attention to the high-precision State Geodetic Coordinate System (GSK-2011), created simultaneously along with the global reference-ellipsoid, and designed for various types of users to conduct the land surveying and mapping in Russia. We also present the geocentric coordinate system (PZ-90.11) used for navigating space missions, solving various problems of global geodesy, and supporting the continuous operation of GLONASS. 相似文献
We have performed high-speed UBV photometric observations on the peculiar binary V Sagittae. Using three new eclipse timings we update the orbital ephemeris and convert it to a dynamical time-scale (TDB). We also searched for quasi-periodic oscillations but did not detect them. Using the Wilson–Devinney algorithm we have modelled the light curve to find the stellar parameters of V Sge. We find that the system is a detached binary but that the primary star is very close to filling its Roche lobe, while the secondary star fills 90 per cent of its Roche lobe volume. We find temperatures of the primary and the secondary star to be T 1=41 000 K and T 2=22 000 K. We find i =72° and masses of 0.8 M⊙ and 3.3 M⊙ for the primary and secondary stars respectively. De-archived Hubble Space Telescope ( HST ) spectroscopy of V Sge shows evidence of mass loss via a wind or winds. In addition we report radio observations of V Sge during an optical high state at 2 cm, 3.6 cm and 6 cm wavelengths. The 3.6 cm emission is increased by a factor of more than six compared with an earlier detection in a previous optical high state. 相似文献
We develop, calibrate and test a dataset intended to drive global ocean hindcasts simulations of the last five decades. This dataset provides surface meteorological variables needed to estimate air-sea fluxes and is built from 6-hourly surface atmospheric state variables of ERA40. We first compare the raw fields of ERA40 to the CORE.v1 dataset of Large and Yeager (2004), used here as a reference, and discuss our choice to use daily radiative fluxes and monthly precipitation products extracted from satellite data rather than their ERA40 counterparts. Both datasets lead to excessively high global imbalances of heat and freshwater fluxes when tested with a prescribed climatological sea surface temperature. After identifying unrealistic time discontinuities (induced by changes in the nature of assimilated observations) and obvious global and regional biases in ERA40 fields (by comparison to high quality observations), we propose a set of corrections. Tropical surface air humidity is decreased from 1979 onward, representation of Arctic surface air temperature is improved using recent observations and the wind is globally increased. These corrections lead to a significant decrease of the excessive positive global imbalance of heat. Radiation and precipitation fields are then submitted to a small adjustment (in zonal mean) that yields a near-zero global imbalance of heat and freshwater. A set of 47-year-long simulations is carried out with the coarse-resolution (2° × 2°) version of the NEMO OGCM to assess the sensitivity of the model to the proposed corrections. Model results show that each of the proposed correction contributes to improve the representation of central features of the global ocean circulation. 相似文献
Production from geothermal reservoirs in volcanic-igneous hydrothermal systems may be disturbed owing to the formation of
authigenic minerals that reduce primary porosity and infill fissure systems. Crystallization may be induced by natural processes
or human activity related to the reservoir exploitation. In volcanic and volcaniclastic rocks, zeolites and related authigenic
silicate minerals commonly develop. Two selected study sites—Pauzhetka geothermal field in Russia and Smrekovec volcanic complex
in Slovenia are characterized by extensive development of progressive stage medium- and low-temperature propylitization and
zeolitization with similar mineral assemblages that reduced original reservoir rock porosity and permeability. Retrograde
and overprinting reactions of argillitization commonly enhance porosity and permeability of rocks, but some other reactions,
like from prehnite to laumontite, from laumontite to heulandite, and from laumontite to analcime, encountered in the Smrekovec
volcanic complex reduced it appreciably. Retrograde reactions recognized in the study sites were not induced by the temperature
drop only, but were accompanied by the change in chemical composition of reacting fluids. Chemical composition of interstitial
waters produced from exploitation wells in the Pauzhetka geothermal field indicate that propylitic and zeolite facies alteration
is related to Na–Cl, slightly alkaline waters, while argillitization involved acidic thermal waters with more complex ion
composition. 相似文献
Doklady Earth Sciences - Satellite data on the total amount of cloud cover in integral parametrization of short-wave incoming fluxes to the Earth’s surface under mass calculations are... 相似文献