Cation Leaching from the Basalt JB–1a by 2M NaCl Hydrothermal Solutions     

Etsuo UCHIDA  Ken TSUTSUI 《Resource Geology》2000,50(2):93-102

Abstract: The basalt JB–1a was reacted with 2M NaCl solutions, and the leaching behavior of the cations Na, K, Ca, Mg, Fe, Mn, Zn and Co was monitored. The experiments were carried out using standard cold-seal pressure vessels in the temperature range from 300 to 800C under the constant pressure of 1000 bars and also in the pressure range from 500 to 1000 bars at 600°C.
The concentrations of Fe, Mn, Zn and Co in the hydrothermal solutions increased significantly with increasing temperature and with decreasing pressure. The thermodynamic analysis of the experimental results suggests that this is due to the formation of trichloro-complexes and also partly due to the temperature dependence of ion exchange between augite and aqueous chloride solution. The Na concentration in the aqueous solution decreases with increasing temperature and with decreasing pressure. On the other hand, the behavior of K, Ca and Mg is complex and their concentrations seem to be controlled by the coexisting minerals.
Judging from the experimental results, it is concluded that the transition elements are effectively leached from the basalt under higher temperatures and lower pressures. This means that higher temperature and lower pressure conditions are preferable for the production of ore-forming hydrothermal solutions.  相似文献   

A tectono-geomorphic model of the hydrogeology of deeply weathered crystalline rock: Evidence from Uganda   总被引：7，自引：4，他引：3  

Richard Taylor  Ken Howard 《Hydrogeology Journal》2000,8(3):279-294

Deeply weathered crystalline rock forms important aquifers for public water supply throughout low-latitude regions of Africa, South America, and Asia, but these aquifers have considerable heterogeneity and produce low well yields. Aquifers occur in the bedrock and overlying weathered mantle and are the products of geomorphic activity of meteoric water, principally deep weathering and stripping. The fundamental relationship between the hydrogeology and geomorphology of these terrains has, however, remained unresolved. This study demonstrates the ability of a recently developed tectono-geomorphic model of landscape evolution in Uganda to explain the hydrogeological characteristics of two basins, as determined using a combination of textural analysis, slug tests, packer tests, and pumping tests. The geopetal imprint of long-term deep weathering and erosional unloading is identified in the vertical heterogeneity of the fractured-bedrock and weathered-mantle aquifers; horizontal heterogeneity is lithologically controlled. The two units form an integrated aquifer system in which the more transmissive (5–20 m²/d) and porous weathered mantle provides storage to underlying bedrock fractures (transmissivity, T, ≈1 m²/d). The thickness and extent of the more productive weathered-mantle aquifer are functions of contemporary geomorphic processes. The utility of the tectono-geomorphic model, applicable to deeply weathered environments, is that it coherently describes the basin-scale hydrogeological characteristics of these complex terrains. Received, June 1999/Revised, January 2000/Accepted, January 2000  相似文献   

黄河三角洲海区2010年潮波分布特征的数值预测   总被引：1，自引：0，他引：1  

郝琰  乐肯堂  刘兴泉 《海洋科学》2000,24(6):43-47

利用二维非线性数值模式,对三角洲邻近海域的潮汐潮流进行了模拟,并根据２０１０年黄河三角洲的预测岩线,预测了该海区２０１０年各主要分潮的分布特征以及最大可能流速分布。数值预测的结果显示２０１０年黄河口迫近海区的潮波分布与目前丰比将不会有显著变化。  相似文献   

Coupling behavior of shear deformation and end rotation of elastomeric seismic isolation bearings          下载免费PDF全文

Ken Ishii  Masaru Kikuchi  Takuya Nishimura  Cameron J. Black 《地震工程与结构动力学》2017,46(4):677-694

This paper presents a mechanical model for predicting the behavior of elastomeric seismic isolation bearings subject to combined end rotations and shear deformation. The mechanical model consists of a series of axial springs at the top, mid‐height and bottom of the bearing to vertically reproduce asymmetric bending moment distribution in the bearings. The model can take into account end rotations of the bearing, and the overall rotational stiffness includes the effect of the variation of vertical load on the bearing and the imposed shear deformation. Static bending tests under various combinations of vertical load and shear deformation were performed to identify the mechanical characteristics of bearings. The test results indicate that bearing rotational stiffness increases with increasing vertical load but decreases with increasing shear deformation. Simulation analyses were conducted to validate the new mechanical model. The results of analyses using the new model show very good agreement with experimental observations. A series of seismic response analyses were performed to demonstrate the dynamic behavior of top‐of‐column isolated structures, a configuration where the end rotations of isolation bearings are typically expected to be larger. The results suggest that the end rotations of elastomeric bearings used in practical top‐of‐column isolated structures do not reduce the stability limit of isolation system. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Innovative Contaminant Mass Flux Monitoring in an Aquifer Subject to Tidal Effects     

Pierre Jamin  Frédéric Cosme  Pierre Briers  Philippe Orban  Ken De Greene  Serge Brouyère 《Ground Water Monitoring & Remediation》2020,40(2):28-39

Exposure from groundwater contamination to aquatic receptors residing in receiving surface water is dependent upon the rate of contaminated groundwater discharge. Characterization of groundwater fluxes is challenging, especially in coastal environments where tidal fluctuations result in transient groundwater flows towards these receptors. This can also be further complicated by the high spatial heterogeneity of subsurface deposits enhanced by anthropogenic influences such as the mixing of natural sediments and backfill materials, the presence of subsurface built structures such as sheet pile walls or even occurrence of other sources of contaminant discharge. In this study, the finite volume point dilution method (FVPDM) was successfully used to characterize highly transient groundwater flows and contaminant mass fluxes within a coastal groundwater flow system influenced by marked tides. FVPDM tests were undertaken continuously for more than 48 h at six groundwater monitoring wells, in order to evaluate groundwater flow dynamics during several tide cycles. Contaminant concentrations were measured simultaneously which allowed calculating contaminant mass fluxes. The study highlighted the importance of the aquifer heterogeneity, with groundwater fluxes ranging from 10⁻⁷ to 10⁻³ m/s. Groundwater flux monitoring enabled a significant refinement of the conceptual site model, including the fact that inversion of groundwater fluxes was not observed at high tide. Results indicated that contaminant mass fluxes were particularly higher at a specific monitoring well, by more than three orders of magnitude, than at other wells of the investigated aquifer. This study provided crucial information for optimizing further field investigations and risk mitigation measures.  相似文献   

Ecology of Shallow Lakes, M. Scheffer     

Ken Irvine 《Journal of Paleolimnology》1999,22(3):331-333

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Hydrochemical Relation Between Shallow Groundwater with Elevated Fluoride and Groundwater in Underlying Carbonates     

Yan Dou  Ken Howard  Liwei Yang  Dong Wang  Li Guo 《Ground water》2020,58(6):1000-1011

In the arid to semi-arid district of Chengcheng, Weinan City, in central Shaanxi Province, diminishing groundwater reserves in the shallow Quaternary (QLB) aquifer and elevated fluoride in the similarly shallow Permo-Triassic (PTF) aquifer, have promoted interest in the development of groundwater resources in the deep but poorly understood Cambrian-Ordovician carbonate aquifer system (COC). To investigate the origin of the COC groundwaters and the relationship between the deep and shallower systems, a hydrochemical study was undertaken involving 179 major and minor ion analyses, 39 stable isotope analyses (δD and δ¹⁸O), and 14 carbon isotope analyses (¹⁴C and δ¹³C). PHREEQC 3.0 was used to investigate mixing. Hydrochemical data support the presence of a well-connected regional flow system extending southwards from the more mountainous north. Stable isotope data indicate that the COC groundwaters originate as soil zone infiltration, under a much cooler regime than is found locally today. This is confirmed by ¹⁴C, which indicates the groundwater to be palaeowater recharged during the late Pleistocene (∼10–12 ka B.P.). The presence of nitrate in the COC groundwaters suggests leakage from overlying shallow aquifers currently provides an additional source of COC recharge, with major faults possibly providing the primary pathways for downward vertical flow.  相似文献   

Sedgwick and his trilobite     

Ken McNamara 《Geology Today》2014,30(4):142-146

Standing on guard at the entrance to the Palaeozoic section of the University of Cambridge's Sedgwick Museum is a bronze statue of the man after whom the museum was named—the 7th Woodwardian Professor, the Reverend Adam Sedgwick. In one hand he holds his trusty geological hammer, in the other is a rock. Sedgwick, the man who unraveled many of the mysteries of the early Palaeozoic rocks of Wales, looks as if he has just cracked a piece of rock off an outcrop. Yet, rather incongruously, he is swathed in his academic gown—our man is clearly both the consummate field geologist and the academic.  相似文献   

Non-ENSO interannual rainfall variability in central Chile during austral winter     

Aldo Montecinos  Michael V. Kurgansky  Cristian Muñoz  Ken Takahashi 《Theoretical and Applied Climatology》2011,106(3-4):557-568

The first principal component (PC1) of seasonal rainfall anomalies in central Chile during winter (June–August) is used to analyze the circulation anomalies related to wet and dry conditions, when near-normal or neutral SST anomalies are observed in the equatorial Pacific, i.e., during non-ENSO conditions. Eight wet and eight dry winter seasons were defined as the upper and lower terciles of PC1 for 24 non-ENSO winters in the period 1958–2000. Unlike the single process attributed to ENSO, during non-ENSO winter seasons, there are several sources triggering or modifying the propagation of the stationary waves that impact the rainfall regime in central Chile. Unfortunately, the multiple processes that seem to be involved in the modulation of the interannual rainfall variability in central Chile, as seen in this work, limit the predictability of rainfall during non-ENSO conditions.  相似文献   

Evaluation of the use of paleotsunami deposits to reconstruct inundation distance and runup heights associated with prehistoric inundation events,Crescent City,southern Cascadia margin     

Curt D. Peterson  Gary A. Carver  Ken M. Cruikshank  Hans F. Abramson  Carolyn E. Garrison‐Laney  Lori A. Dengler 《地球表面变化过程与地形》2011,36(7):967-980

Historic‐ and prehistoric‐tsunami sand deposits are used to independently establish runup records for tsunami hazard mitigation and modeled runup verification in Crescent City, California, located in the southern Cascadia Subduction Zone. Inundation from historic (1964) farfield tsunami (~5–6 m runup height) left sand sheet deposits (100–200 m width) in wetlands located behind a low beach ridge [3–4 m elevation of the National Geodetic Vertical Datum of 1988 (NAVD88)]. The most landward flooding lines (4·5–5 m elevation) in high‐gradient alluvial wetlands exceed the 1964 sand sheet records of inundation by 1–2 m in elevation. The most landward flooding in low‐gradient alluvial wetlands exceed the corresponding sand sheet record of inundation distance by 1000 m. Nevertheless, the sand sheet record is an important proxy for high‐velocity inundation. Sand sheet deposition from the 1964 historic tsunami closely corresponds to the landward extent of large debris transport and structural damage in the Crescent City waterfront. The sand sheet deposits provide a proxy for maximum hazard or ‘kill zone’ in the study area. Six paleotsunami sand sheets (0·3–3 ka) are recorded in the back‐ridge marshes in Crescent City, yielding a ~450 year mean recurrence interval for nearfield Cascadia tsunami. Two paleotsunami sand deposit records, likely correlated to Cascadia ruptures between 1·0 and 1·5 ka, are traced to 1·2 km distance and 9–10 m elevation, as adjusted for paleo‐sea level. The paleotsunami sand deposits demonstrate at least twice the runup height, and four times the inundation distance of the farfield 1964 tsunami sand sheet in the same marsh system. The preserved paleotsunami deposits in Crescent City are compared to the most landward flooding, as modeled by other investigators from a predicted Cascadia (~ Mw 9) rupture. The short geologic record (~1·5 ka) yields slightly lower runup records than those predicted for the modeled Mw 9 rupture scenario in the same marsh, but it generally verifies predicted maximum tsunami runup for use in the planning of emergency response and rapid evacuation. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献