共和盆地干热岩地热资源的成因机制:来自岩石放射性生热率的约束

共和盆地位于青藏高原东北缘,是我国重要的干热岩地热资源赋存区之一.成因机制研究是干热岩地热资源研究中最为基础与核心的工作之一,也是干热岩地热资源潜力精细评价和合理开发利用的重要依据.本文基于98块采自共和—贵德盆地岩石样品的放射性生热率数据,分析了盆地主要岩性岩石的放射性生热率分布特征,讨论了共和盆地干热岩地热资源的成因机制,并初步建立了干热岩地热资源的成因模式.研究表明,共和盆地恰卜恰地热区沉积岩（以泥岩和粉砂质泥岩为主）放射性生热率为1.21~2.02 μW·m^-3,平均值为1.67±0.29 μW·m^-3;以花岗岩和花岗岩闪长岩等为主的基底岩石的放射性生热率介于1.17~5.81 μW·m^-3之间,平均值为3.20±1.07 μW·m^-3.贵德盆地扎仓寺地热区沉积岩（以砂岩和泥质砂岩为主）放射性生热率为1.83~2.40 μW·m^-3,平均值为2.13±0.23 μW·m^-3;基底花岗质岩石的放射性生热率介于0.92~6.49 μW·m^-3之间,平均值为2.81±1.40 μW·m^-3.测试数据显示共和—贵德盆地基底花岗岩不存在高放射性生热率异常.但是,新生代以来印度—欧亚板块持续性陆-陆碰撞作用造成的壳内放射性生热元素富集层增厚,导致了花岗岩放射性生热率的热贡献量同步增大（30.3~40.5 mW·m^-2）,因此,花岗岩放射性生热可为共和盆地干热岩地热资源提供稳定的壳内热源基础.基于放射性生热率数据和热流配分研究,结合研究区已有地质-地球物理研究资料,本文认为壳内部分熔融层作为附加热源为共和盆地干热岩地热资源提供了重要的附加热流贡献.在此基础上,本文初步构建了共和盆地干热岩地热资源成因模式：加厚地壳花岗岩放射性生热与壳内部分熔融层供热.

     

The impact of well‐field configuration on contaminant mass removal and plume persistence for homogeneous versus layered systems

A three‐dimensional numerical model was used to simulate the impact of different well‐field configurations on pump‐and‐treat mass removal efficiency for large groundwater contaminant plumes residing in homogeneous and layered domains. Four well‐field configurations were tested, Longitudinal, Distributed, Downgradient, and natural gradient (with no extraction wells). The reductions in contaminant mass discharge (CMDR) as a function of mass removal (MR) were characterized to assess remediation efficiency. Systems whose CDMR‐MR profiles are below the 1:1 relationship curve are associated with more efficient well‐field configurations. For simulations conducted with the homogeneous domain, the CMDR‐MR curves shift leftward, from convex‐downward profiles for natural gradient and Longitudinal to first‐order behaviour for Distributed, and further leftward to a sigmoidal profile for the Downgradient well‐field configuration. These results reveal the maximum potential impacts of well‐field configuration on mass‐removal behaviour, which is attributed to mass‐transfer constraints associated with regions of low flow. In contrast, for the simulations conducted with the layered domain, the CMDR‐MR relationships for the different well‐field configurations exhibit convex‐upward profiles. The nonideal mass‐removal behaviour in this case is influenced by both well‐field configuration and back diffusion associated with low‐permeability units.     

S/P模式计算的冷却塔烟气抬升高度敏感性试验

德国VDI3784的S/P模式为三维流体动力学积分模式,其方程主要描述了无穷小体积元素的质量、动量、静态污染物质量浓度及能量的守恒。利用德国模式进行了冷却塔烟气排放不同参数、不同大气条件下烟气抬升高度的敏感性试验。结果表明：在影响烟气抬升高度的3个气象要素（风速、气温和湿度）中,风速和气温的变化对结果影响较大,而湿度影响较小。在D类稳定度,当环境风速从0.1 m/s增加到15.0 m/s时,抬升高度从711.7 m变为38.5 m。随着环境温度的升高,抬升高度明显单调变小;当稳定度为A类,环境温度从10升到40时,烟气抬升最大高度从688.9 m降低到45.1 m,降低了14倍多。而环境湿度的变化,对抬升高度的影响不是很明显。对于E类稳定度和F类稳定度,当环境湿度从20%增加到70%,最大抬升高度分别从115.3 m和84.6 m降到112.9 m和81.7 m,分别降低了3.43%和2.08%。在影响烟气抬升高度的其他3个因素（凉水塔直径、烟气出口速度和混合气体温度）中,混合气体温度的变化对结果影响较大,而凉水塔直径和烟气出口速度的影响较小。在各类稳定度条件下,当出口温度从20变到90时,烟气抬升高度增加1.2—13.3倍;在各类稳定度条件下,当凉水塔直径从30 m变到90 m,烟气抬升高度仅增加0.63—1.40倍;在各类稳定度条件下,当出口速度从2.5 m/s变到8.0 m/s,烟气抬升高度增加了0.24—0.74倍。     

Estimating turbidity and total suspended matter in the Adour River plume (South Bay of Biscay) using MODIS 250-m imagery

The Basque coastal waters (South Bay of Biscay) are directly influenced by the Adour River freshwater plume. The Adour outflow leads to important variations of suspended matter concentrations and turbidity, which in turn may affect biological productivity and water quality. This study aims at both developing specific algorithms and testing the efficiency of atmospherically corrected MODIS-Aqua 250-m surface reflectance product (MYD09) to map total suspended matter concentrations and turbidity within the Adour coastal region. First, regional empirical algorithms based on in-situ data were tested to retrieve the concentration of total suspended matter and turbidity from the remote sensing reflectance. Then, the respective sensitivity of MODIS surface reflectance bands 1 and 2 for water quality application was investigated as well as the quality of atmospheric corrections. Finally, selected algorithms were applied to the MYD09 product. The resulting 250-m resolution maps were then compared to 1000-m maps produced by IFREMER and comparisons between satellite measurements and in-situ sampling points were performed. Results show that MODIS-Aqua band 1 (620–670 nm) is appropriate for predicting turbidity and total suspended matter concentrations using polynomial regression models, whilst band 2 is unadapted. Comparison between total suspended matter concentration 250-m resolution maps and mineral suspended matter 1000-m maps (generated by IFREMER) produced consistent results. A high correlation was obtained between turbidity measured in-situ and turbidity retrieved from MODIS-Aqua satellite data.     

地幔柱与岩石圈相互作用过程的数值模拟

地幔柱的研究是地球科学研究的热点之一.本文主要集中研究地幔柱与岩石圈的相互作用过程.基于质量守恒方程、动量守恒方程和能量守恒方程,通过有限元数值方法可以计算得到地幔柱与岩石圈相互作用的温度场、速度场和有效黏度等的时空图.本文的流变本构模型主要基于非牛顿流体的有效黏度模型,通过数值模拟计算分析了地幔柱与岩石圈相互作用过程,着重讨论了地壳流变结构对此过程的影响.数值模拟结果显示,地幔柱与岩石圈的相互作用分为三个阶段:地幔柱上升期,时间持续到0.2 Ma,平均速度为2.75 m·a-1,地幔柱顶部地形开始向上隆起;地幔柱与岩石圈纵向作用期,时间从0.2 Ma到0.26 Ma,地幔柱上升的平均速度为0.83 m·a-1,地表地形隆升达到最大值;地幔柱与岩石圈横向作用期,0.26 Ma以后,岩石圈开始剪切变形,地幔柱水平运动速度为0.47 m·a-1,当剪切变形达到一定程度,岩石圈底部开始出现拆沉作用.当下地壳流变强度比较小时,上地壳的流变结构控制着地幔柱顶部地表地形隆起程度,流变强度越大,隆升高度越小;而下地壳的流变结构控制着地幔柱两侧地表地形的下沉幅度,下地壳流变强度越小,下沉幅度越大.最后,讨论了数值模拟对峨眉山大火成岩省地幔柱发展演化的应用.     

Simulations of spatial variability in particle‐size emissions during wind erosion events

This study simulates how spatial variations in particle‐size emissions from a playa affect bulk and size‐resolved dust concentration profiles during two contrasting wind erosion events (a small local and a large regional event) in the Channel Country, Lake Eyre Basin, Australia. The regional event had higher dust concentration as a result of stronger frontal winds and higher erodibility across the playa. For each event, two emission scenarios are simulated to determine if measured size‐resolved dust concentration profiles can be explained by spatial variability in source area emissions. The first scenario assumes that particle‐size emissions from source areas occur at a uniform rate, while the second scenario assumes that particle‐size emissions vary between and within source areas. The uniform emission scenario, reproduced measured bulk dust concentration profiles (R² = 0·93 regional and R² = 0·81 local), however simulated size‐resolved dust concentration profiles had poor statistical fits to measured size‐resolved profiles for each size class (the highest were R² = 0·5 regional and R² = 0·3 local). For the differential particle‐size emission scenario, the fit to the measured bulk dust concentration profiles is improved (R² = 0·97 regional and R² = 0·83 local). However, the fit to the size‐resolved profiles improved dramatically, with the lowest being R² = 0·89 (regional) and R² = 0·80 (local). Particle‐size emission models should therefore be tested against both bulk and size‐resolved dust concentration profiles, since if only bulk dust concentration profiles are used model performance may be over‐stated. As the source areas in the first 90 m upwind of the tower were similar for both events, the percentage contributions of each particle‐size class to total emissions can be compared. The contribution of each particle‐size class was similar even though the wind speed, turbulence and dust concentrations were significantly different; suggesting that the contribution of each particle‐size to the total emitted dusts is not related to wind speed and turbulence. Copyright © 2012 John Wiley & Sons, Ltd.     

Basaltic thermals and Subplinian plumes: Constraints from acoustic measurements at Shishaldin volcano, Alaska

The 1999 basaltic eruption of Shishaldin volcano (Alaska, USA) included both Strombolian and Subplinian activity, as well as a “pre-Subplinian” phase interpreted as the local coalescence within a long foam in the conduit. Although few visual observations were made of the eruption, a great deal of information regarding gas velocity, gas flux at the vent and plume height may be inferred by using acoustic recordings of the eruption. By relating acoustic power to gas velocity, a time series of gas velocity is calculated for the Subplinian and pre-Subplinian phases. These time series show trends in gas velocity that are interpreted as plumes or, for those signals lasting only a short time, thermals. The Subplinian phase is shown to be composed of a thermal followed by five plumes with a total expelled gas volume of .The initiation of the Subplinian activity is probably related to the arrival of a large overpressurised bubble close to the top of the magma column. A gradual increase in low-frequency (0.01–0.5 Hz) signal prior to this “trigger bubble” may be due to the rise of the bubble in the conduit. This delay corresponds to a reservoir located at ≈3.9 km below the surface, in good agreement with studies on other volcanoes.The presence of two thermal phases is also identified in the middle of the pre-Subplinian phase with a total gas release of and . Gas velocity at the vent is found to be and for the Subplinian plumes and the pre-Subplinian thermals respectively.The agreement is very good between estimates of the gas flux from modelling the plume height and those obtained from acoustic measurements, leading to a new method by which eruption physical parameters may be quantified. Furthermore, direct measurements of gas velocity can be used for better estimates of the flux released during the eruption.     

Earthquake swarms and local crustal spreading along major strike-slip faults in California

Earthquake swarms in California are often localized to areas within dextral offsets in the linear trend in active fault strands, suggesting a relation between earthquake swarms and local crustal spreading. Local crustal spereading is required by the geometry of dextral offsets when, as in the San Andreas system, faults have dominantly strike-slip motion with right-lateral displacement. Three clear examples of this relation occur in the Imperial Valley, Coso Hot Springs, and the Danville region, all in California. The first two of these areas are known for their Holocene volcanism and geothermal potential, which is consistent with crustal spreading and magmatic intrusion. The third example, however, shows no evidence for volcanism or geothermal activity at the surface.     

Siting criteria for heat extraction from hot dry rock; Application to Switzerland

For selecting possible hot dry rock extraction sites for geothermal energy applications, the following criteria have been considered: (i) depth to the crystalline basement, (ii) temperatures at depth, (iii) pattern of regional stress field and (iv) natural permeability (=degree of fracturing) of basement rocks. A contour map of the basement topography is presented. From outcrops at the nothern border of Switzerland (crystalline rocks of the Black Forest massif, mainly granites and gneisses of Hercynian age) the basement dips gently toward the SE under the Mesozoic and Tertiary sediments of the Molasse Basin and reaches its maximum depth (7 km) underneath the front of the Alps. Some 30 km further SE the basement rocks appear at the surface (Aar- and Gotthard-massif, Penninic units), where they are deformed and fractured to a great extent. Temperature-depth profiles have been obtained by model calculations. Locally increased heat product on (in granite batholiths) at the base of the Molasse Basin, combined with the blanketing effect of the overlying sediments, could raise the temperatures to 150–170°C at a depth of 5 km. According to earthquake fault-plane solutions (P-axes) the regional stress field in the area of the Swiss Alps and in its northern Foreland is characterized by the maximum horizontal compression oriented N(150±20)°E in the upper crust.In situ stress determinations (overcoring experiments) show that considerable excess horizontal compressive stress is present in the Alpine crust (up to 200 bar). The deep Alpine tunnels exhibited considerable fracturing of crystalline rocks at depths greater than 1–2 km. Information about the degree of fracturing has also been obtained by refraction profiles. The velocitydepth functions show lower than normal velocities in the uppermost 1.5 km, indicating that the rocks there are fractured. A 30–40 km wide region, running along the axis of the Molasse Basin (which coincides with the majority of the population and most of the industry of Switzerland) would provide the best hot dry rock sites.Paper presented at the Second NATO-CCMS Meeting on Dry Hot Rock Geothermal Energy, 28–30 June 1977, Los Alamos, New Mexico, USA. Contribution No. 198, Institute of Geophysics ETH Zurich.     

华北地幔亚热柱型地震机理探讨

中国是一个多地震的国家,以地震多、震级大、损失惨重为特征。介绍了西太平洋与欧亚大陆间的洋-陆俯冲带型地震;印度次大陆与喜马拉雅陆-陆碰撞型地震和华北地幔亚热柱拆离滑脱型地震等3种地震基本类型,并侧重探讨了华北地幔亚热柱外围拆离滑脱带型地震的发震构造、形成机制和地震模型。