会徽——地质学会的文化表达

会徽是一种行业标识、一段历史烙印、一个学术品牌,它作为一种信息载体,以简单、形象、易识别的图像表达了学术团体的学术宗旨和使命,同时彰显了学术团体的工作目标、学术精神等科学文化内涵。笔者等以中国地质学会会徽为分析案例,通过与东西方几个代表性国家地质学会的文化宗旨与会徽内涵的比较,探讨会徽在学会科学文化建设中的作用。     

The role of inherited extensional fault segmentation and linkage in contractional orogenesis: a reconstruction of Lower Cretaceous inverted rift basins in the Eastern Cordillera of Colombia

Lower Cretaceous early syn‐rift facies along the eastern flank of the Eastern Cordillera of Colombia, their provenance, and structural context, reveal the complex interactions between Cretaceous extension, spatio‐temporal trends in associated sedimentation, and subsequent inversion of the Cretaceous Guatiquía paleo‐rift. South of 4°30′N lat, early syn‐rift alluvial sequences in former extensional footwall areas were contemporaneous with fan‐delta deposits in shallow marine environments in adjacent hanging‐wall areas. In general, footwall erosion was more pronounced in the southern part of the paleorift. In contrast, early syn‐rift sequences in former footwall areas in the northern rift sectors mainly comprise shallow marine supratidal sabkha to intertidal strata, whereas hanging‐wall units display rapid transitions to open‐sea shales. In comparison with the southern paleo‐rift sector, fan‐delta deposits in the north are scarce, and provenance suggests negligible footwall erosion. The southern graben segment had longer, and less numerous normal faults, whereas the northern graben segment was characterized by shorter, rectilinear faults. To the east, the graben system was bounded by major basin‐margin faults with protracted activity and greater throw as compared with intrabasinal faults to the west. Intrabasinal structures grew through segment linkage and probably interacted kinematically with basin‐margin faults. Basin‐margin faults constitute a coherent fault system that was conditioned by pre‐existing basement fabrics. Structural mapping, analysis of present‐day topography, and balanced cross sections indicate that positive inversion of extensional structures was focused along basin‐bounding faults, whereas intrabasinal faults remained unaffected and were passively transported by motion along the basin‐bounding faults. Thus, zones of maximum subsidence in extension accommodated maximum elevation in contraction, and former topographic highs remained as elevated areas. This documents the role of basin‐bounding faults as multiphased, long‐lived features conditioned by basement discontinuities. Inversion of basin‐bounding faults was more efficient in the southern than in the northern graben segment, possibly documenting the inheritance and pivotal role of fault‐displacement gradients. Our observations highlight similarities between inversion features in orogenic belts and intra‐plate basins, emphasizing the importance of the observed phenomena as predictive tools in the spatiotemporal analysis of inversion histories in orogens, as well as in hydrocarbon and mineral deposits exploration.     

Wave moment geodynamics

The work presents a review of natural-science representations on the rotary motion of matter and its piecewise structure. Development of dense GPS-networks allowed to experimentally confirm the concept of block structures of the geophysical environment and to prove rotary character of block movement. An analysis of both the migration of earthquake sources and the movement of sections of tectonic plates’ borders has allowed to reveal general properties of such movements and to prove their wave nature. It is shown that within the limits of rotational model, blocks and plates are interconnected among themselves by the elastic long-range fields forming a uniform planetary geodynamic field. It is offered to use the geodynamic solutions of rotational model in the one class of phenomena as a basis at the construction of a new geological paradigm — wave moment geodynamics.     

Simulation of spatially-distributed copper pollution in a large river basin using the ECOMAG-HM model

The semi-distributed physically-based model ECOMAG-HM was developed to simulate cycling of heavy metals in large river basins: on the surface, and in soil, groundwater and river water. The model was applied to study the spatial distribution and temporal dynamics of copper concentrations in watercourses of the Nizhnekamskoe Reservoir watershed in Russia. This watershed is characterized by high background concentrations of heavy metals due to wide occurrence of ore deposits and considerable concentrations of ore-parent elements in rocks. The model was found to adequately reproduce the spatial variation of the mean annual copper concentrations at different monitoring points of the river network. The mean annual specific copper washoff, with the surface and subsurface components of river runoff, and the total copper washoff from the watershed into the river network were calculated and mapped. The contributions of natural and anthropogenic factors to river water pollution by copper were evaluated.     

Modelling Internal Solitary Waves in the Coastal Ocean

In the coastal oceans, the interaction of currents (such as the barotropic tide) with topography can generate large-amplitude, horizontally propagating internal solitary waves. These waves often occur in regions where the waveguide properties vary in the direction of propagation. We consider the modelling of these waves by nonlinear evolution equations of the Korteweg–de Vries type with variable coefficients, and we describe how these models are used to describe the shoaling of internal solitary waves over the continental shelf and slope. The theories are compared with various numerical simulations.     

Secular dynamics of S-type planetary orbits in binary star systems: applicability domains of first- and second-order theories

We analyse the secular dynamics of planets on S-type coplanar orbits in tight binary systems, based on first- and second-order analytical models, and compare their predictions with full N-body simulations. The perturbation parameter adopted for the development of these models depends on the masses of the stars and on the semimajor axis ratio between the planet and the binary. We show that each model has both advantages and limitations. While the first-order analytical model is algebraically simple and easy to implement, it is only applicable in regions of the parameter space where the perturbations are sufficiently small. The second-order model, although more complex, has a larger range of validity and must be taken into account for dynamical studies of some real exoplanetary systems such as \(\gamma \) Cephei and HD 41004A. However, in some extreme cases, neither of these analytical models yields quantitatively correct results, requiring either higher-order theories or direct numerical simulations. Finally, we determine the limits of applicability of each analytical model in the parameter space of the system, giving an important visual aid to decode which secular theory should be adopted for any given planetary system in a close binary.     

Uranium Behavior in the Process of Primary Pitchblende Ores Alteration by the Post‐ore Hydrothermal Solutions: An Application to Assessment of Uranium Migration from Underground Spent Nuclear Fuel Repositories

It has been shown that the main uranium ore mineral, pitchblende (uranium dioxide), is a natural analog of synthetic uraninite (also uranium dioxide), which constitutes 96% of spent nuclear fuel (SNF). Geochronological studies of the U‐Pb isotope systems in unaltered pitchblende from the orebodies reveal that these systems remained completely closed over the entire period (approximately 135 Ma) since the formation of the deposits. The bulk of the primary uranium ores within the Streltsovskoye ore field was influenced to various degrees by post‐ore hydrothermal solutions that led to pitchblende spherulites being replaced by pseudomorphs of an amorphous phase with a U‐Si composition; this phase also re‐precipitated in veinlets proximal to the pitchblende pseudomorphs. A technique specially developed by the authors was used to carry out quantitative counts of the abundance of uranium minerals by calculating the uranium mass balance in one of the orebodies subjected to hydrothermal alteration. The calculations reveal minimal uranium loss from the orebody. Uranium liberated in the process of the pseudomorphic replacement of pitchblende was immediately fixed, in situ, in the newly formed coffinite‐like amorphous U‐Si phase as a result of the development of an efficient geochemical barrier that prevented the long‐distance migration of uranium. In assessing the long‐term safety of underground SNF repositories, the results of the present study give us confidence that SNF uraninite, in terms of the preservation of its integrity as a mineral phase, provides for the reliable long‐term isolation of uranium, transuranium elements, and fission products that are “sealed” in the uraninite matrix. In the case of the mineral transformation of the uraninite matrix by hydrothermal solutions, the liberated uranium would be efficiently immobilized by the newly formed amorphous U‐Si phase.     

A geophysical survey of the Spitsbergen Margin and surrounding areas

New geophysical information including multichannel seismic profiling data obtained by the PGO Sevmorgeologia Ministry of Geology of the former USSR, Murmansk during 1984–1988 is discussed and interpreted in this study. The deep structure, sedimentary cover and stratigraphy of the Spitsbergen Continental Margin, considered to be a passive margin, i.e. divergent in the northern part and strike-slip in the western part, is described.Two genetically different types of plateaus on the continental margin, Yermak in the north and Spitsbergen (Vestnesa) in the west, have been identified.The entire extent of the continental slope of the northern part of the Spitsbergen Continental Margin in the Eurasia Basin is underlain by attenuated continental crust, while at the base of the Southwest Continental Margin, the oceanic crust along almost the entire extent is observed. The sedimentary cover, up to 10 km thick within the West Spitsbergen Continental Margin, is likewise observed. Within the North Spitsbergen Margin, however, it does not exceed 3.5 km in thickness.The extension and deposition within the West Spitsbergen Margin began in early Oligocene, while the rifting with accompanying sedimentation within the North Spitsbergen Continental Margin started probably in Early Cretaceous.     

Three Decades of Seismic Activity at Mt. Vesuvius: 1972–2000

We analyse the seismic catalogue of the local earthquakes which occurred at Somma-Vesuvius volcano in the past three decades (1972–2000). The seismicity in this period can be described as composed of a background level, characterised by a low and rather uniform rate of energy release and by sporadic periods of increased seismic activity. Such relatively intense seismicity periods are characterised by energy rates and magnitudes progressively increasing in the critical periods. The analysis of the b value in the whole period evidences a well-defined pattern, with values of b progressively decreasing, from about 1.8 at the beginning of the considered period, to about 1.0 at present. This steady variation indicates an increasing dynamics in the volcanic system. Within this general trend it is possible to identify a substructure in the time sequence of the seismic events, formed by the alternating episodes of quiescence and activity. The analysis of the source moment tensor of the largest earthquakes shows that the processes at the seismic source are generally not consistent with simple double-couples, but that they are compatible with isotropic components, mostly indicating volumetric expansion. These components are shown to be statistically significant for most of the analysed events. Such focal mechanisms can be interpreted as the effect of explosion phenomena, possibly related to volatile exsolution from the crystallising magma. The availability of a reduced amount of high quality data necessary for the inversion of the source moment tensor, the still limited period of systematic observation of Vesuvius micro-earthquakes and, above all, the absence of eruptive events during such interval of time, cannot obviously permit the outlining of any formal premonitory signal. Nevertheless, the analysis reported in this paper indicates a progressively evolving dynamics, characterised by a generally increasing trend in the seismic activity in the volcanic system and by a significant volumetric component of recent major events, thus posing serious concern for a future evolution towards eruptive activity.     

Wavelet analysis for the regional-residual and local separation of potential field anomalies

A method based on the discrete wavelet transform was applied to the regional-residual separation of potential fields and to the filtering of local anomalies. A specific space-scale wavelet analysis, called multiresolution analysis, allowed decomposition of the signal with respect to a vast range of scales. Different analysing wavelets were applied to anomalies in both synthetic and real cases, but the more appropriate basis needed to be chosen by requiring the maximum compactness for the multiresolution analysis. Moreover, since such analysis was found not to be shift-invariant, the same criterion was applied to choosing the best signal shift. Application of the technique to both synthetic and real cases produced an optimal space-scale representation of the fields and a consistent regional-residual separation. Furthermore, the space localization allowed a variety of filtered signals to be obtained, each one with a specific scale and local area content. Fourier and wavelet analyses were both applied to the filtering out of the intense Etna anomaly from the aeromagnetic field of Sicily. The wavelet method was more powerful, suppressing only the Etna volcano anomaly and leaving the rest of the map practically unchanged.