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781.
The standard enthalpies of formation of FeS (troilite), FeS2 (pyrite), Co0.9342S, Co3S4 (linnaeite), Co9S8 (cobalt pentlandite), CoS2 (cattierite), CuS (covellite), and Cu2S (chalcocite) have been determined by high temperature direct reaction calorimetry at temperatures between 700 K and 1021 K. The following results are reported: $$\Delta {\rm H}_{f,FeS}^{tr} = - 102.59 \pm 0.20kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,FeS}^{py} = - 171.64 \pm 0.93kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,Co_{0.934} S} = - 99.42 \pm 1.52kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,Co_9 S_8 }^{ptl} = - 885.66 \pm 16.83kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,Co_3 S_4 }^{In} = - 347.47 \pm 7.27kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,CoS_2 }^{ct} = - 150.94 \pm 4.85kJ mol^{ - 1} ,$$ $$\Delta {\rm H}_{f,Cu_2 S}^{cc} = - 80.21 \pm 1.51kJ mol^{ - 1} ,$$ and $$\Delta {\rm H}_{f,CuS}^{cv} = - 53.14 \pm 2.28kJ mol^{ - 1} ,$$ The enthalpy of formation of CuFeS2 (chalcopyrite) from (CuS+FeS) and from (Cu+FeS2) was determined by solution calorimetry in a liquid Ni0.60S0.40 melt at 1100 K. The results of these measurements were combined with the standard enthalpies of formation of CuS, FeS, and FeS2, to calculate the standard enthalpy of formation of CuFeS2. We found \(\Delta {\rm H}_{f,CuFeS_2 }^{ccp} = - 194.93 \pm 4.84kJ mol^{ - 1}\) . Our results are compared with earlier data given in the literature; generally the agreement is good and our values agree with previous estimates within the uncertainties present in both. 相似文献
782.
W. L. F. Brinkmann Dr. H. Hahn H. Schick J. W. Fachbereich Geowissenschaften 《GeoJournal》1987,14(3):331-338
Two lakes, Lake Gänseweiher (LGW) and Lake Fechenheimer Weiher (LFW) occupy groundwater filled abandoned gravel pits which serve as fishing grounds and are part of recreational areas, respectively.Both lakes are cut into a near-surface groundwater aquifer, which is located in the pleistocene River Main gravel terrace t6. They are sealed at the base by miocene clays and above by overlying flood deposits of the River Main. The latter provide protection from pollutants derived from wet and dry deposition of atmospheric contaminants.Groundwater chemistry determines the pool of dissolved constituents in lake water. The temporal and spatial distribution patterns of chemical compounds in lake water are brought about by endo-biogenic processes, of which the indicators are nitrate-nitrogen and dissolved silica. The latter illustrates an instantaneous response to pulses of diatom blooms.Both lakes are eutrophic (polytrophic) according to the classification guidelines presented in literature. 相似文献
783.
Dolgikh G. I. Dolgikh S. G. Vasilevskaya L. N. Lisina I. A. 《Doklady Earth Sciences》2020,490(1):18-22
Doklady Earth Sciences - The interaction between the atmosphere and the lithosphere in the minute range of periods is considered. The technique of assessment of the influence of atmospheric... 相似文献
784.
Yu. L. Gulbin 《Geology of Ore Deposits》2016,58(7):559-567
The objective of this study is to provide insights into the REE and Y behavior during garnet porphyroblast formation in staurolite-bearing schists as a constituent of Late Paleoproterozoic metapelites of the Ladoga Complex. The MnNCKFMASH P–T pseudosection for a single sample and Grt–Bt thermometry indicate that the garnet core grew at 520°C and under 7.0–7.2 kbar in the Grt–Bt–Pl–Chl–Ms–Zo field, whereas the garnet rim was equilibrated at 590–600°C and under 3.5–4.0 kbar. The measured zoning profiles are strongly depleted in REE + Y in the garnet core containing high Mn and Ca concentrations. The intermediate zone of garnet is enriched in La, Ce, Pr, and Nd (inner LREE + Nd annulus), as well as in Dy, Er, Yb, Lu, and Y (outer HREE + Y + Dy annulus). According to pseudosection analysis, these peaks were probably produced owing to breakdown of epidote-group minerals (allanite, REE-rich epidote) at T < 535°C and P > 6.5 kbar. Towards the rim, the HREE + Y contents gradually decrease, whereas MREE (Sm, Eu, Gd) display an inverse trend. The rim also exhibits a negative Eu anomaly. The former tendency reflects an increase in temperature during garnet crystallization and partitioning of elements between garnet and monazite. It is thought that the latter is linked to oppositely directed change in garnet-monazite partition coefficients for HREE and MREE with increasing temperature. 相似文献
785.
786.
We solve a plane problem of linear baroclinic seiches in closed rotating basins of variable depth with two-layer density stratification.
In the long-wave approximation, we get a boundary-value problem for a system of ordinary differential equations and propose
a numerical procedure for finding internal seiches. The analytic solutions of the problem are obtained for a basin of constant
depth. The numerical analysis of seiches is performed for the distributions of depth corresponding to the zonal and meridional
sections of the Black Sea and model basins including the cases of a shelf zone and an underwater ridge. It is shown that the
baroclinic seiches become more intense in shallow-water regions and that the intense longshore currents caused by Earth’s
rotation are formed in the shelf zones and over the underwater ridges. 相似文献
787.
788.
Wind erosion of soil is an appreciable but unstudied event following fires in cold desert. We examined aeolian transport of sediment for 1 year following fire in semi-arid shrub steppe on loess soils in southern Idaho, USA. Sediment collectors were used to determine horizontal mass transport of soil and saltation sensors and anemometers were used to determine saltation activity (fraction of time having saltation) and threshold wind speed in an area burned in August and an unburned control site. Horizontal mass transport (per 30-day period) was negligible in the unburned area, but in the burned area was 5.40 kg m?1 in October and decreased to 2.80 kg m?1 in November and 0.32 kg m?1 in December. Saltation activity was high enough to determine threshold wind speeds only in the burn site during fall, when values ranged from 10.0 to 10.6 m s?1. Sediment flux and saltation activity in the burned site became much less pronounced following the emergence of herbaceous vegetation in the spring. Post-fire sediment flux in the shrub steppe we examined was of greater magnitude but shorter duration than post-fire fluxes in warm deserts or sandier regions that experience more frequent wind erosion. 相似文献
789.
Active tectonics and erosional unloading at the eastern margin of the Tibetan Plateau 总被引:14,自引:0,他引:14
Alexander L. Densmore LI Yong Michael A. Ellis ZHOU Rongjun 《山地科学学报》2005,2(2):146-154
Introduction The eastern margin of the Tibetan Plateau, adjacent to the Sichuan Basin (Figure 1), has become a testing ground for a variety of models that contrast mechanisms of extrusion and crustal thickening associated with the India-Asia collision (Avouac and Tapponnier 1993, England and Houseman 1986),but that also address the extent to which the upper crust and upper mantle are coupled (Royden et al. 1997, Holt 2000). The margin is characterized by topographic relief of over 5 km an… 相似文献
790.
F. L. Brazhalovich M. I. Klyuchnikov A. I. Lukyanov 《Geography and Natural Resources》2016,37(3):264-270
We examine the phenomenon of “collapsed” states by using, as an example, Somalia that is being faced with a vast array of problems: collapse of state institutes, civil war, separatism, terrorism, radical Islamism, and piracy. It is found that clannishness and tribalism of Somali society are complicating the process of political settlement and national reconciliation. It is pointed out that some of the tribes and groups, including under the action of external forces, are actually forming the country’s political space. It is shown that the pseudo-state entities in Somalia are unstable, and their boundaries of “flowing” so that they are incapable of exercising a full control over the territory. It is emphasized that the problem of Islamic extremism can be treated as deriving from failure of the state institutes; the peak of activity and territorial expansion of Islamist groups in the country is now in the past, and the area of their activity is bounded by the area inhabited by the Somali ethnos. It is found that the piracy problem is determined by the geographical location of Somalia, and its solution is impossible without the reestablishment of the state institutes and the economic system of the country. Two potential cores of reestablishment of Somali statehood have been revealed: Federal Government in Mogadishu as well as the Autonomous Republic of Puntland. It is forecasted that the international community will be gradually recognizing the Republic of Somaliland. It is concluded that the federalization of the country as declared by authorities is formal in character but yields first results implying that the negotiation process between the groups of clans has been led into a political channel. 相似文献