文献翻译竞赛题目
Part Ⅰ
We have described our approach in chronicling the Mesozoic and Cenozoic history of sea level fluctuations from various parts of the world. Our objective has been to make the cycle charts public in the most expedient manner possible. In this article we have not attempted to address the important issues of the causes of sea level change, the absolute magnitude of the sea level rises and falls through time, the implication of these changes for the continental margin and deep-sea sedimentary budgets, or their influence on hydrography, climate, and biotic distribution and evolution.
A cursory comparison, for example, could not establish a clear relation between oceanic sedimentation rates and sea level fluctuations. A comparison of Neogene sea level cycles with known intervals of widespread gaps in deep-sea sedimentation reveals, however, that these gaps are coincident either with the downlap surfaces(condensed sections) of major and medium magnitudes (which represent periods of maximum flooding of the shelves) or with sequence boundaries (which represent sea level drops), depending on whether the hiatuses are caused by carbonate dissolution or by erosion and removal of sediments from the sea floor. A recent study has shown that in the central equatorial Pacific, the major breaks in Neogene sedimentation correspond to regionally correlatable and synchronous seismic reflectors. When compared to our sea level cycles, these reflectors also correspond to condensed sections of major and medium magnitude. The reflectors are caused by carbonate dissolution or diagenesis and are related to changes in the ocean chemistry. Obviously,there may be a cogent connection between sea level fluctuations and shifts in the quality of deep ocean water. We suggest the following scenario to explain this correspondence between the two opposite phases(highstand and lowstand) of the sea level cycle and deep-sea hiatuses.
During the highstand, after a prominent sea level rise, the terrigenous sediments are trapped on the inner shelf, starving the outer shelf and slope. The sequestering of carbonate on the inner shelf may lead to reduced dissolved carbonate in seawater, and the resulting rise in calcite compensation depth (CCD) would lead to increased dissolution in the deeper parts of the basins. This reduction in carbonate during highstand would explain the correlation of dissolution hiatuses with condensed sections (times of maximum flooding of the shelves). The sea level elevation would also lead to climatic equitability and the weakening of latitudinal thermal gradients, which in turn would result in reduced current activity both at the surface and on the sea bottom. After a marked sea level fall, on the other hand, the inner shelf is bypassed, and sediments are directly transported to the outer shelf or slope. The resulting increase in carbonate content of the seawater and the lowering of CCD would reduce carbonate dissolution.But the climatic inequitability and strengthened thermal gradients during the lowstand would lead to intensified circulation and increased bottom water activity, causing widespread erosion on the sea floor. This process explains the correspondence of the erosional hiatuses to sequence boundaries.
Part Ⅱ
The time when the Ural Mountains began up lifting again came in the Pliocene (Puchkov and Danukalova, 2009). It is most important as the time of placer final formation. Once created during the previous epochs, placers could not simply disappear, dissipate or shift horizontally under influence of a deep erosion, but could be just redeposited into new transversal valleys (Shilo, 2002). On the other hand, the importance of this epoch for formation of placers should not be overestimated. The previous, platform stage, with its long epochs of weathering, river transportation and near-shore sediment differentiation was much more productive.
In compliance with the above, in the areas of intense syn-orogenic erosion of the Urals, one can expect presence of only “secondary”, redeposited placers; the “primary”, predominantly Mesozoic placers are preserved at lower topographic levels; they occur in the Transuralian areas. In turn, the Mesozoic placers are attracted to an intersection of ancient valleys and zones of primary mineralization. Thus, the most usual gold-placer primary sources are thought to be quartz lodes (Koroteev and Sazonov, 2005).
The reworked placers are not the only type of deposits formed during the neotectonic epoch. For example, in the Quaternary time in the Chelyabinsk area was formed the uranium deposit of a new type (Sanarka), situated in a river valley over a weathering crust of granites (Khokhryakov, 2004).
The neotectonic stage had a special effect on redistribution of liquid and gaseous deposits (oil, gas, condensate, mineral and drinking water and, as a special case, formation of thermal gases of Jangan-Tau) (Puchkov and Abdrakhmanov, 2003).
The velocity of movement of oil and condensate could be considerable. As it is shown for the exhausted oil deposits, after some period of rest, they can show a partial recovery of resources (Kinzebulatovo oil deposit in the South Urals and some deposits of Chechnya in the Greater Caucasus).
The dynamics of underground waters of the Urals and adjacent territories experienced a great influence of orogenic processes (the modern Urals plays a manifold role as a repository of fracture waters, regulator of water distribution, influencing water pressure in the basins around the Urals). Nevertheless, the most important stage of formation of water chemistry in the Volga–Urals basin was the extensive Early Permian halogenesis. The surficial waters in the early Permian basin became very dense, due to high concentration of salts. This caused an intense density inversion and quick and strong salification of deep horizons of the basin. The brines were stratified and metamorphosed during the Meso-and Cenozoic times. The penetration of brines into the Proterozoic and Paleozoic (pre-Kungurian) strata also caused a metasomatic dolomitization of limestones with increase in their filtration capacity,which was important for formation of hydrocarbon plays.
The last, but not the least, are the man-made, “technogenic” deposits, formed as a result of human mining activity. Very often, gigantic waste dumps and tailings of beneficiation plants of activemining enterprises contain useful components that can play now, or in the future, a role of new deposits, though currently they produce a negative impact on atmosphere and water. Even waters formed under waste heaps in some cases may attract attention not only as an environmental menace, but also as a mineral source.
Part Ⅲ
If one takes the molecular weight to be lower than 1500 Daltons, then, it is clear that molecular weight itself cannot fully describe many behaviors of petroleum liquid containing asphaltenes. These liquids exhibit the effect of asphaltene as if asphaltenes were large molecules. Recent investigation suggests that these effects may be attributed to polarity and charge-like interactions.
The above-mentioned microscopic parameters, molecular weight, polarity, charge-like interactions, are more relevant to downstream refinery than to upstream productions. This is because it is believed that the asphaltene form aggregates in a refining process. These asphaltene aggregates can entrap lighter components, thereby hindering the refining yield. To improve the refining yield, it is necessary to open up the aggregates to enhance the refining yield. This requires thorough characterization of asphaltene structure, average molecular weight, aggregation, and the energies involved in the aggregation process.
The ultimate parameter for resolving refining asphaltene problem is to quantitatively evaluate the energies involved in the self-association process. It is a difficult subject and is still an open question. A possible route is to determine the molecular weight, the aggregate size, and packing conditions of the aggregates so that a corresponding thermodynamic model can be developed to account for the energies into the self-association process. Once the model is established experiments needed to determine the relevant parameters can be conducted. For example, molecular weight can be measured using mass spectroscopy; the size of the asphaltene aggregates can be determined accurately using scattering techniques. Figure 5 shows a typical scattering spectrum (the intensity distribution function) of an asphaltene solution. One can extract structure of asphaltene from the intensity distribution function.
