Potash–Forming Regularity of the Ordovician Marine Northern Shaanxi Salt Basin: Insight from Review and Prospect of the Deep Geology of the Ordos Basin

The Ordovician Northern Shaanxi Salt Basin(ONSSB), located in the east–central Ordos Basin, western North China Craton(NCC), is one of the largest marine salt basins yet discovered in China. A huge amount of halite deposited in the Mid-Ordovician Majiagou Formation, and potashcontaining indication and local thin layer of potash seam were discovered in O2 m65(6 th submember, 5 th member of the Majiagou Formation). This makes ONSSB a rare Ordovician potash-containing basin in the world, and brings new hope for prospecting marine solid potash in this basin. However, several primary scientific problems, such as the coupling relationship between ONSSB and the continent nucleus, how the high-precision basement fold controls the ONSSB, and how the basement faults and relief control ONSSB, are still unclear due to the limitations of the knowledge about the basement of the Ordos Basin. This has become a barrier for understanding the potash-forming regularity in the continental nucleus(CN) area in marine salt basin in China. Up to now, the material accumulation has provided ripe conditions for the answers to these questions. Latest zircon U-Pb ages for the basement samples beneath the Ordos Basin reveal that there exists a continental nucleus(Yi-Meng CN) beneath the northern Ordos Basin. And this brings light into the fact that the ONSSB lies not overlying on the YiMeng CN but to south Yi-Meng CN. Both do not have superimposed relationship in space. And borehole penetrating into the basement reached Palaeoproterozoic meta-sedimentary rocks, which suggests the ONSSB is situated in the accretion belt of Yi-Meng CN during geological history. Basement relief beneath the ONSSB area revealed by seismic tomography and aeromagnetic anomaly confirms the existence of basement uplift and faults, which provides tectonic setting for sedimentary center migration of the ONSSB. Comparative research with various data sources indicates that the expanding strata in the ONSSB adopted the shape of the basement folds. We found that the orientations of the potash sags showed high correlation with those of several basement and sedimentary cover faults in the ONSSB. The secondary depressions are also controlled by the faults. Comparative research between all the global salt basins and continental nuclei distribution suggests that distribution of the former is controlled by the latter, and almost all the salt basins developed in or at the margin of the continental nucleus area. The nature of the tectonic basement exerts a key controlling effect on potash basin formation. And on this basis we analyzed in detail the geological conditions of salt-forming and potash-forming in the ONSSB.     

基于流固耦合作用的某尾矿坝渗流稳定性分析

尾矿坝是矿山重要设施之一,其内部含有大量的水和尾矿,一旦失稳造成的损失不可估量。尾矿坝失稳有众多因素影响,但是坝内浸润线是最活跃的影响因素。本文基于流固耦合理论,建立某尾矿坝有限元计算模型,考虑坝内排水井的存在。模拟坝内不同工况下浸润线分布,对其静力稳定性及流固耦合作用下尾矿坝应力应变场进行分析,并将浸润线模拟位置与实际监测结果进行对比。揭示库内不同工况下浸润线变化规律以及与坝体稳定性之间的关系,并分析评价不同工况下尾矿坝的稳定性。最后,将渗流场与应力场进行流固耦合,模拟出365 d坝内应力位移分布,为尾矿坝施工及安全运行提供可靠的依据及技术支持。     

Comparison of the compositions of crystalline aluminosilicate rocks and their minerals in a planar triangular projection

The problem of comparison of the composition of crystalline rocks with the composition of the constituent minerals of these rocks is considered. It is proposed to present the composition of rocks and the compositions of the constituent minerals in the form of a triangle on the plane. The experience of presentation of compositions in phase diagrams was taken as a basis for the construction. Analysis of the crystallochemical characteristics of clinopyroxenes and garnets has shown that three parameters are enough for depicting the compositions of these and other minerals. For this purpose, similar composition components of rocks and their minerals are summarized in molecular proportions and are plotted on the triangle DO-1/2(R₂O3)-XO₂, where DO = (MgO + CaO + FeO + MnO + NiO + ...) + 1/4(Na₂O + Al₂O₃) + 1/4(K₂O + Al₂O₃), 1/2(R₂O₃) = 1/2(Al₂O₃ + Fe₂O₃ + Cr₂O₃ + ...) - (1/4(Na₂O + Al₂O₃) + 1/4(K₂O + Al₂O₃)), and XO₂ = SiO₂ + TiO₂. The compositions of minerals are expressed as the sums of their components: Ol = Fo + Fa + Lar + Neph + ..., Px = Di + En + Wol + Ged + Gip + Jd + Eg + ..., Ga = Pyr + Gross + Alm + Spe + Ski + Knr + Mj + ..., etc. A step-by-step calculation algorithm is proposed, which permits evaluation of the contents of bi- and trivalent iron during probe microanalyses of garnets and pyroxenes. Comparison of the compositions of deep-seated rocks and their minerals shows their good consistency. The proposed schematic projection permits a visual comparison of the compositions of rocks with low contents of carbonates and water, from ultrabasic (e.g., dunites) to acid (e.g., granites) ones.     

基于耦合协调视角的河北省旅游产业与区域经济一体化发展研究

在定性分析河北省旅游产业与区域经济发展现状的基础上,以耦合函数为基础,构建旅游产业与区域经济发展水平的耦合协调度模型,通过对相关指标数据的实证分析得出:11个地级市中仅秦皇岛的旅游产业与区域经济处于勉强协调,其他地级市则处于濒临失调状态中,故河北省整体耦合协调水平很低,区域经济尚未对旅游产业发展提供有力反哺。在此结论基础上,就如何深化一体化发展提出4个发展路径,以期为河北省旅游产业的快速发展提供有效指导。     

区域旅游流网络结构与环境响应研究——以京津冀地区为例

旅游流对区域旅游开发规划具有重要指导作用,如何实现旅游流与区域经济、社会、自然环境的协调发展成为许多地区亟待思考的问题。该文借助社会网络理论和方法研究区域旅游流网络结构体系,从经济、社会、自然环境角度分析区域旅游流网络结构的环境影响因子;通过构建耦合协调度模型测量环境因子对区域旅游流网络结构的影响强度,并利用Moran指数对区域旅游流网络结构与环境的耦合协调度进行全局及局部自相关分析。最后以京津冀地区为例,探查该地区旅游流网络结构与环境的响应效果,为区域旅游流网络结构优化提供决策参考。     

川东北中—下三叠统流体动力场及成藏成钾耦合机理

川东北地区是近年来的找钾重点区。本文研究了三叠系嘉陵江组和雷口坡组的卤水储层特征、卤水化学特征和地下流体动力场,结果表明:川东北地区嘉陵江组和雷口坡组卤水储层主要为裂缝-溶孔型和白云岩型,属低孔低渗储层;宣汉—达州—开县—开江一带为中上扬子区的一个咸化凹陷,发育巨厚蒸发岩层,并且正好为流体越流浓缩成藏成矿区;该地区的卤水矿化度和钾离子含量较高,K+、Br+等离子含量达到卤水工业开采指标。综合分析川东北地区地下流体(气、水)的动力学特征,揭示地下流体动力场是二次富钾成矿的主要机制,在这一机制下,地层中封存的通过海水浓缩初始富钾形成的原始沉积水进一步浓缩富钾,并运聚至合适的构造-地层圈闭中,造就了该地区具备上气下水的耦合成藏成钾条件,有望成为"气钾兼探"的重要耙区。     

The Cosmolian program for simulating aeolian dynamics and its application to central Australia

The wide spatial coverage of sand dunes in continental interiors makes the understanding of their activity and accumulation history valuable for palaeoenvironmental reconstructions and the interpretation of landscape evolution. Nevertheless, the study of aeolian landscape development at the million-year timescale is hampered by the complex interaction of factors determining dune migration and the inherently self-destructive nature of their chronostratigraphy, thus limiting the applicability of traditional dating methods. This study presents a standalone program that simulates aeolian transport based on luminescence-derived chronologies coupled with numerical modelling of the accumulation of cosmogenic nuclides. This integrative approach to modelling the history of aeolian landforms reveals phases of emergence of aeolian sand into the landscape, and provides a data-based scheme that facilitates the morphodynamical study of aeolian processes over multiple timescales and up to several millions of years. The application of the program for reanalysing previously reported data from the Australian Simpson Desert reveals multiple pulses of sand dispersion into central Australia at 3.8–3.4, 2.9–2.5 and 1.5–1 Ma, corresponding to pronounced changes in climatic conditions and landscape deformation events. The synchronicity of the results with the established environmental framework that would promote the production and aeolian distribution of sand exemplifies the applicability of process-based modelling in constructing a timeframe of key landscape evolution events in arid environments by studying aeolian deposits. The dependence of the parameters used to determine environmental settings on sand transportation patterns additionally makes the program a powerful tool to further investigate the triggers and mechanisms of aeolian processes.     

基于Chebyshev多项式的非对称走时Kirchhoff叠前时间偏移角道集求取

地震射线走时的求取方法是叠前时间偏移研究的核心问题之一,也是影响计算时间域角道集角度精确性的关键因素之一.本文基于Kirchhoff叠前时间偏移,应用第一类切比雪夫多项式,对弯曲射线对称走时加以改进,引进非对称项,优化后得到切比雪夫非对称走时方程,与高精度走时进行比较和误差分析,再将该走时求取方法应用于时间域角道集的求取中,得到地下较真实的入射角.通过模型计算和实际地震资料处理证明,此种非对称走时及其角道集的求取方法具有精度高、计算量少的优点.     

Observations and conceptual modelling of morphological coupling in a double sandbar system

Nearshore sandbars, located in <10 m water depth, can contain remarkably periodic alongshore undulations in both cross‐shore position and depth. In a double sandbar system, the alongshore spacing of these morphological patterns in the inner sandbar may be identical to those in the outer sandbar. Although this morphological coupling has been observed previously, its frequency and predominance remain unclear. In this paper, we use a 9.3‐year dataset of daily low‐tide time exposure images from the double‐barred beach at Surfers Paradise (Gold Coast, Australia) to analyse the temporal and spatial characteristics of morphological coupling within a double sandbar system. We distinguish five types of morphological coupling between the inner and outer sandbars, of which four coincide with a downstate progression of the outer bar. Coupling is either in‐phase (with a landward perturbation of the inner bar facing an outer‐bar horn) or out‐of‐phase (with a seaward perturbation of the inner bar facing an outer‐bar horn), where the coupled inner‐bar features either consist of rip channels or, predominantly, perturbations of the low‐tide terrace. Cross‐correlation of the image‐derived inner‐ and outer‐bar patterns shows coupling to be a common phenomenon in the double sandbar system studied here, with coupling in 40% of the observations. In contrast to previous observations of sandbar–shoreline coupling at single‐barred beaches, in‐phase coupling (85% of all coupled bar patterns) predominates over out‐of‐phase coupling (15%). Based on our observations and bathymetries assimilated from the images for a restricted set of coupling events, we hypothesize that the angle of offshore wave incidence, wave height and depth variations along the outer sandbar determine the type of flow pattern (cell circulations versus meandering currents) above the inner bar and hence steer the type of coupling. Copyright © 2012 John Wiley & Sons, Ltd.     

(Dis)Connectivity in catchment sediment cascades: a fresh look at the sediment delivery problem

The concept of the sediment delivery problem was introduced into the literature in 1983 by Des Walling. This concept describes how only a fraction of sediment eroded within a catchment will reach the basin outlet and be represented as sediment yield, and that sediment storage mechanisms operating within a catchment explain this discrepancy. Since this paper was published, geomorphologists have been examining in great detail the fate of sediment eroded from the landsurface, and the pathways and timeframes of sediment transport and storage in catchments. However, to fully understand the internal dynamics of sediment flux requires a ‘fresh look at the sediment delivery problem’. A framework is required that can incorporate the various processes involved in sediment movement from source areas through a basin to its outlet, and can take account of the spatial distribution of, and timeframes over which, these processes operate. This paper presents a conceptual framework for analysis of catchment (dis)connectivity that incorporates both spatial and temporal variability in the operation of the sediment cascade. This approach examines where blockages occur to disrupt these longitudinal, lateral and vertical linkages in catchments. Depending on the position of blockages (termed buffers, barriers and blankets), and their sediment residence time, various parts of a catchment may be actively contributing sediment to the sediment cascade and be switched on, or inactive and switched off. This paper discusses how such a framework can be used to model response times to disturbance and explain the manifestation of geomorphic change in catchments. The paper then highlights challenges geomorphologists face in applying such a framework to understand the internal dynamics of the catchment sediment cascades, and forecast how environmental change might affect the operation of sediment fluxes into the future. Copyright © 2012 John Wiley & Sons, Ltd.