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951.
I. Yu. Melekestseva V. A. Kotlyarov P. V. Khvorov V. N. Ivanov V. E. Beltenev I. G. Dobretsova 《Geology of Ore Deposits》2010,52(8):800-810
The porous fine-grained to microcrystalline copper-zinc ore of the Semenov-2 hydrothermal field, a site in the Semenov hydrothermal
cluster discovered in 2007 (13°31′N, MAR), is anomalously enriched in Au (22–188 ppm) and Ag (127–1787 ppm). Chalcopyrite,
isocubanite, würtzite, and opal are major minerals; sphalerite, marcasite, pyrite, and covellite are auxiliary; and galena,
pyrrhotite, native gold, silver telluride, barite, and aragonite are sporadic. Gold containing 0.31 to 23.07 wt % Ag occurs
as up to 9-μm-sized subhedral, dendritelike, and elongated grains mostly hosted in opal and less frequently in sphalerite
and in pores within isocubanite-chalcopyrite aggregate. An elongated grain (2 × 4 μm in size) of the Ag-Te phase was found
in a pore. So far only basalts have been dredged from the Semenov-2 field, but anomalous gold and silver concentrations suggest
the influence of ultramafic rocks; the latter were found 1.5 km westward, in the Semenov-1 hydrothermal field. Mineral assemblage
and morphology of gold particles indicate its primary origin in contrast to the hydrothermal fields hosted in basalts, where
gold is a product of remobilization. Zonal gold grains, found on oceanic floor for the first time, are characterized by low
Ag content in the cores and high Ag content in the outer rims, reflecting variation in formation conditions. 相似文献
952.
I. V. Pekov N. V. Zubkova N. V. Chukanov A. E. Zadov V. G. Grishin D. Yu. Pushcharovsky 《Geology of Ore Deposits》2010,52(7):584-590
A new mineral, yegorovite, has been identified in the late hydrothermal, low-temperature assemblage of the Palitra hyperalkaline pegmatite at Mt. Kedykverpakhk, Lovozero alkaline pluton, Kola Peninsula, Russia. The mineral is intimately associated with revdite and megacyclite, earlier natrosilite, microcline, and villiaumite. Yegorovite occurs as coarse, usually split prismatic (up to 0.05 × 0.15 × 1 mm) or lamellar (up to 0.05 × 0.7 × 0.8 mm) crystals. Polysynthetic twins and parallel intergrowths are typical. Mineral individuals are combined in bunches or chaotic groups (up to 2 mm); radial-lamellar clusters are less frequent. Yegorovite is colorless, transparent with vitreous luster. Cleavage is perfect parallel to (010) and (001). Fracture is splintery; crystals are readily split into acicular fragments. The Mohs hardness is ~2. Density is 1.90(2) g/cm3 (meas) and 1.92 g/cm3 (calc). Yegorovite is biaxial (?), with α = 1.474(2), β = 1.479(2), and γ = 1.482(2), 2V meas > 70°, 2V calc = 75°. The optical orientation is X ∧ a ~ 15°, Y = c, Z = b. The IR spectrum is given. The chemical composition determined using an electron microprobe (H2O determined from total deficiency) is (wt %): 23.28 Na2O, 45.45 SiO2, 31.27 H2Ocalc; the total is 100.00. The empirical formula is Na3.98Si4.01O8.02(OH)3.98 · 7.205H2O. The idealized formula is Na4[Si4O8(OH)4] · 7H2O. Yegorovite is monoclinic, space group P21/c. The unit-cell dimensions are a = 9.874, b= 12.398, c = 14.897 Å, β = 104.68°, V = 1764.3 Å3, Z = 4. The strongest reflections in the X-ray powder pattern (d, Å (I, %)([hkl]) are 7.21(70)[002], 6.21(72)[012, 020], 4.696(44)[022], 4.003(49)[211], 3.734(46)[\(\bar 2\) 13], 3.116(100)[024, 040], 2.463(38)[\(\bar 4\)02, \(\bar 2\)43]. The crystal structure was studied by single-crystal method, R hkl = 0.0745. Yegorovite is a representative of a new structural type. Its structure consists of single chains of Si tetrahedrons [Si4O8(OH)4]∞ and sixfold polyhedrons of two types: [NaO(OH)2(H2O)3] and [NaO(OH)(H2O)4] centered by Na. The mineral was named in memory of Yu. K. Yegorov-Tismenko (1938–2007), outstanding Russian crystallographer and crystallochemist. The type material of yegorovite has been deposited at the Fersman Mineralogical Museum of Russian Academy of Sciences, Moscow. 相似文献
953.
M. A. Akhmet’ev N. I. Zaporozhets A. I. Iakovleva G. N. Aleksandrova V. N. Beniamovsky T. V. Oreshkina Z. N. Gnibidenko Zh. A. Dolya 《Stratigraphy and Geological Correlation》2010,18(6):635-659
The analysis of the main biospheric events that took place in West Siberia and the Arctic region during the Early Paleogene
revealed the paleogeographic and paleobiogeographic unity of marine sedimentation basins and close biogeographic relations
between their separate parts. Most biotic and abiotic events of the first half of the Paleogene in the Arctic region and West
Siberia were synchronous, unidirectional, and interrelated. Shelf settings, sedimentation breaks, and microfaunal assemblages
characteristic of these basins during the Paleogene are compared. The comparative analysis primarily concerned events of the
Paleocene-Eocene thermal maximum (PETM) and beds with Azolla (aquatic fern). The formation of the Eocene Azolla Beds in the Arctic region and West Siberia was asynchronous, although it proceeded in line with a common scenario related
to the development of a system of estuarine-type currents in a sea basin partly isolated from the World Ocean. 相似文献
954.
955.
This paper addresses the geochemical features of the noble metal disseminated sulfide and Timagnetite mineralization in the rocks of the Kalar group of autonomous gabbro-anorthosite massifs. The investigations suggest that this mineralization was formed in two stages. The first stage is related to the gabbroanorthosites proper and may be promising for low-sulfide PGE mineralization as well as PGE-bearing Ti-magnetite mineralization, while the second stage is linked to the ultrabasic intrusions associated with copper-nickel or chromite mineralization accompanying by PGE. The horizons of low-sulfide mineralization in the gabbro-anorthosites and copper-nickel mineralization in the dunite-pyroxenites are characterized by the Pd predominance over Pt, while the Cr-bearing and Ti-magnetite ores show the Pt predominance over Pd. 相似文献
956.
Jebel Khariz, the largest central vent volcano on the south Arabian coast, lies 60 miles (95 km) to the west of Aden and was probably active during the Upper Miocene. The volcanic edifice originally covered some 350 sq. miles (900 km2) and consists of an older, radially dipping main cone sequence of rhyolites, trachytes, basalts and olivine basalts and a younger, horizontal caldera sequence mainly of intermediate lavas, that infilled the caldera subsequent to its formation at a late stage in the history of the volcano. The Khariz volcanic suite, ranging in composition from olivine basalts to per-alkali rhyolites of comenditic affinity, was probably produced by fractionation, in a low pressure regime, of a mildly alkali olivine basalt magma. Noting the abundance of peralkali volcanics associated with the African rift system in Kenya, Ethiopia and on the margins of the Red Sea and the Gulf of Aden, it is tentatively suggested that, at times, the sub-crustal mechanism, responsible for the rift development, might also produce an environment where fusion of the earth’s mantle gave rise to a relatively rare, mildly alkali, ‘parental’ basaltic magma. 相似文献
957.
P. I. Tokarev 《Bulletin of Volcanology》1971,35(1):230-242
The general relationships of the structure of the Kurile-Kamchatka zone are examined. The chain of volcanoes forms a true arc with the radius of 1884 km. The focal layer of earthquakes along the whole arc extends to depth with an angle of 48° ± 5°, and is a part of the surface of a circular cone. The energy of earthquakes at intervals of depth 0–100 km, 101–300 km, and 301–650 km is on the average distributed equally along the whole arc and in time. The activity of volcanoes of the whole zone in time is also rather evenly distributed. The energy lost from the earth’s interior during the volcanic eruptions is not less than the energy emitted as elastic waves during tectonic earthquakes. 相似文献
958.
When evaporation from the surfaces of a region is limited by the availability of moisture the resultant changes in the temperature and humidity of the overpassing air are reflected in the potential evaporation. Such interactions have provided the basis for the progressive development of a model in which the regional evaporation, a product of climatic, soil moisture and vegetative processes, is estimated from its effects on potential evaporation or on representative climatological observations. Further improvements are presented and the results are tested with previously published hydrologic and climatologic data from twenty river catchments in Canada and Ireland. These catchments have a range in annual runoff of approximately zero to one meter and a range of snow cover duration from almost zero to six months. Comparison of model predictions with precipitation less runoff estimates for five year periods provides reasonable evidence for the validity of the model with a maximum deviation of 44 mm yr−1, or 9%, and a standard error of estimate of 26 mm yr−1. Seasonal comparisons permit insights into the variability of catchment storage and the effects of climate and topograpy on regional evaporation. 相似文献
959.
960.
Attention to detail is essential for the reduction of pollution. By detective work, a river purification board has been able to track down an important single source of PCB contamination of its sewage sludge and institute remedial action. 相似文献