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Data on mineral-hosted melt, fluid, and crystalline inclusions were used to study the composition and evolution of melts that produced rocks of Changbaishan Tianchi volcano, China–North Korea, and estimate their crystallization parameters. The melts crystallized within broad ranges of temperature (1220–700°C) and pressure (3100–1000 bar), at a drastic change in the redox potential: Δ log \(f_{O_2}\) from NNO + 0.92 to +1.42 for the basalt melts, NNO –1.61 to –2.09 for the trachybasaltic andesite melts, NNO –2.63 to –1.89 for the comendite melts, and NNO –1.55 to –3.15 for the pantellerite melts. The paper reports estimates of the compositions of melts that produced the continuous rock series from trachybasalt to comendite and pantellerite. In terms of trace-element concentrations, all of the mafic melts are comparable with OIB magmas. The silicic melts are strongly enriched in trace elements and REE. The most strongly enriched melts contain concentrations of certain elements almost as high as in ores of these elements. The paper reports data on H2O concentrations in melts of different composition. It is demonstrated that the variations in the H2O concentrations were controlled by magma degassing. Data are reported on the Sr and Nd composition of the rocks. The deviations in the Sr isotopic composition are proportional to the 87Sr/86Sr ratio and could be produced in a melt with a high enough 87Sr/86Sr ratio during a geologically fairly brief time period. The evolution of melts that produced rocks of the volcano was controlled by crystallization differentiation of the parental basalt magmas at insignificant involvement of melt mixing and liquid immiscibility of silicate and sulfide melts. The alkaline salic rocks were generated in shallow-sitting (13–3.5 km) magmatic chambers in which the melts underwent profound differentiation that gave rise to pantellerites and comendites strongly enriched in trace elements (Th, Nb, Ta, Zr, and REE). Data on the composition of the magmas and parameters of their derivation are used to develop a generalized petrologic–geodynamic model for the origin of Changbaishan Tianchi volcano. 相似文献
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Water Resources - English-language publications on the assessment of hazards and risks in recreation water use are reviewed. The main themes and results of foreign studies into the effect of... 相似文献
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O. V. Andreeva 《Geology of Ore Deposits》2012,54(1):41-59
Mineral transformation of host rocks and localization of orebodies at the unconformity-type uranium deposits are considered
for the Karku deposit in the northern Ladoga region. It is shown that the great depth of uranium mineral formation and the
peculiar composition of host rocks, along with temperature and chemistry of fluids, played a critical role in variation of
lithostatic and fluid pressure, porosity, and permeability. The compaction of quartz sandstone and gravelstone, which are
typical host rocks at unconformity-type deposits, the development of microstylolithic sutures, conformal structures, pressure
solution and deposition of quartz in free pores gave rise to the closure or constraint of pore space and to increase in pore
pressure of fluids in the deep part of the Riphean troughs with approaching lithostatic loading. A transitional zone between
hydrostatic and lithostatic pressure controlled localization of orebodies and was decisive for uranium mineral formation.
This zone coincided with the Riphean-Paleoproterozoic unconformity and sank somewhat into the crystalline basement. Below
this transitional zone, the intergranular fluid was under a pressure that was close to the pressure on solid phases, i.e.,
P
tot ≈ P
fl. The reliability of this phenomenon is confirmed by cessation of pressure solution-redeposition of quartz and distinct deceleration
of dehydration of hydrous minerals. As is shown for the Karku deposit, the highly hydrated clay minerals of the illite-smectite
series are widespread in its subore portion and lacking at the supraore levels along with termination of quartz regeneration.
It is suggested that a zone of superhigh fluid pressure in deep parts of sedimentary basins constrains localization of uranium
orebodies by structural and stratigraphic unconformity between Riphean and Paleoproterozoic rocks. It is stated that altered
wall rocks at the unconformity-type uranium deposits cannot be identified with products of hydrothermal phyllic and argillic
alteration of host rocks at the medium- and low-temperature endogenic deposits. The main distinctions consist in lack of wall-rock
metasomatic reaction zoning and acid-alkaline evolution of solutions. All transformations of host rocks should be classified
as diverse manifestations of deep catagenesis of sedimentary sequences and buried regolith. The carbon and oxygen isotopic
compositions of calcite from host rocks at the Karku deposit are far from those of magmatic and hydrothermal carbonates. They
are characterized by a high δ18O = +17 to +25‰ and a high dispersion of δ13C = −1.5 to almost −15‰. No granitoid magmatism is known in the regions, where the unconformity-type uranium deposits occur.
Therefore, the rocks of the crystalline basement are the most probable source of uranium, which precipitated on the reductive
barrier as a product of interaction with bitumen contained in the Riphean basal beds. 相似文献
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N. A. Andreeva Yu. L. Zyskin O. R. Kalekin Yu. I. Neshpor A. A. Stepanyan V. P. Fomin N. N. Chalenko V. G. Shitov 《Astronomy Letters》2000,26(4):199-203
We present two-year-long observations of the flux of very-high-energy (~1012 eV) gamma rays from the active galactic nucleus Mk 501 performed with a Cherenkov detector at the Crimean Astrophysical Observatory. A gamma-ray flux from the object was shown to exist at confidence levels of 11 and 7 standard deviations for 1997 and 1998, respectively. The flux varied over a wide range. The mean flux at energies >1012 eV, as inferred from the 1997 and 1998 data, is (5.0±0.6)×10?11 and (3.7±0.6)×10?11 cm?2 s?1, respectively. The errors are the sum of statistical observational and modeling errors. The mean power released in the form of gamma rays is ~2×1043 erg s?1 sr?1. 相似文献
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Krupskaya V. V. Andreeva I. A. Sergeeva E. I. Cherkashev G. A. 《Lithology and Mineral Resources》2002,37(2):130-137
The submarine Haakon Mosby mud volcano was studied in detail during several cruises, resulting in the collection of an abundant and diverse lithological material. Comprehensive field and laboratory studies made it possible to identify different types of sediments with specific granulometric and pelite fraction (<0.005 mm) compositions, as well as the regularity of their spatial distribution relative to various morphostructural zones of the mud volcano. 相似文献
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Z. V. Andreeva 《Russian Meteorology and Hydrology》2013,38(2):113-118
Considered are the possibilities for detecting the zones of ecological problems of marine environment using the ocean color sensors data and the radar images. Presented are the peculiarities of satellite data interpretation and the experimental results indicating the spatial and temporal distribution of biogenic slicks and chlorophyll-a concentration as the indicators of ecological conditions in the marine environment. Proposed is the multiparameter correlation graph displaying the relationship between the ecological factors significant for studying the anthropogenic eutrophication. 相似文献