四川盆地地下卤水资源优势及综合开发前景

四川盆地地下卤水自震旦系至白垩系各层系皆有分布。卤水具有分布广泛、资源丰富、品质优异、高承压及气卤同产等优势特点,是四川得天独厚的液态矿产资源。卤水中含有K+、Br-I、-、B3+、Li+、Sr2+、Rb+等多种有用组分,皆为国家紧缺和紧俏物质,其含量多数可达工业开采品位,为优质化工原料水,经济价值极高,综合开发利用前景广阔。     

Stratigraphic evolution of a fluvial–eolian succession: The example of the Upper Jurassic—Lower Cretaceous Guará and Botucatu formations, Paraná Basin, Southernmost Brazil

The Guará and Botucatu formations comprise an 80 to 120 m thick continental succession that crops out on the western portion of the Rio Grande do Sul State (Southernmost Brazil). The Guará Formation (Upper Jurassic) displays a well-defined facies shift along its outcrop belt. On its northern portion it is characterised by coarse-grained to conglomeratic sandstones with trough and planar cross-bedding, as well as low-angle lamination, which are interpreted to represent braided river deposits. Southwards these fluvial facies thin out and interfinger with fine- to medium-grained sandstones with large-scale cross-stratification and horizontal lamination, interpreted as eolian dune and eolian sand sheets deposits, respectively. The Botucatu Formation is characterised by large-scale cross-strata formed by successive climbing of eolian dunes, without interdune and/or fluvial accumulation (dry eolian system). The contact between the Guará and the Botucatu formations is delineated by a basin-wide deflation surface (supersurface). The abrupt change in the depositional conditions that took place across this supersurface suggests a major climate change, from semi-arid (Upper Jurassic) to hyper-arid (Lower Cretaceous) conditions. A rearrangement of the Paraná Basin depocenters is contemporaneous to this climate change, which seems to have changed from a more restrict accumulation area in the Guará Formation to a wider sedimentary context in the Botucatu Formation.     

Preliminary evaluation of hydrochemistry of the Kalambaina Formation, Sokoto Basin, Nigeria

Hydrochemical investigations in the Kalambaina Formation have been initiated to determine potability and suitability of the shallow groundwater for domestic and agricultural uses. This limestone formation is an extensive aquifer supplying water to livestock and domestic wells in its outcrop areas. The aquifer is recharged by rainfall and discharges mainly into the Sokoto–Rima River system and lakes at Kware, Gwadabawa and Kalmalo in Nigeria. Because recharge to the aquifer is mainly from rainfall, the quality of the groundwater is controlled essentially by chemical processes in the vadose zone and locally by human activities. Water samples were taken at 11 sites comprising boreholes, dug wells and a spring and were chemically analysed for their major ion components. Hydrochemical results show water of fairly good quality. It is, however, hard and generally of moderate dissolved solids content. Concentration of the total dissolved solids is between 130 and 2,340 mg/l. Concentrations of ions vary widely but a high concentration of K⁺ is found in places. NO₃⁻ is on the higher side of the World Health Organization (WHO) permissible limits, indicating pollution in such areas. Groundwater chemistry is predominantly of two facies, namely the calcium–magnesium–bicarbonate and calcium–magnesium–sulphate–chloride facies. These facies probably evolved primarily as a result of dissolution of calcium and magnesium carbonates as well as some human/land-use activities.     

Evolution of the Bonneville shoreline scarp in west-central Utah: Comparison of scarp-analysis methods and implications for the diffusion model of hillslope evolution

Wave-cut pluvial shoreline scarps are ideal natural experiments in hillslope evolution because the ages of these scarps are often precisely known and because they form with a range of heights, alluvial textures, and microclimates (i.e., orientation). Previous work using midpoint-slope methods on pluvial scarps in the Basin and Range concluded that scarp evolution is nonlinear and microclimatically controlled. The purpose of this study was to further examine the influence of scarp height, texture and microclimate in an attempt to calibrate a nonlinear model of scarp evolution. To do this, over 150 profiles of the Bonneville shoreline in the adjacent Snake and Tule Valleys, west-central Utah were collected and analyzed by fitting the entire scarp profile to diffusion-equation solutions, taking into account uncertainty in the initial scarp angle. In contrast to previous studies, this analysis revealed no evidence for nonlinearity or microclimatic control. To understand the reason for this discrepancy, we undertook a systematic study of the accuracy of each scarp-analysis method. The midpoint-slope-inverse method was found to yield biased results, with systematically higher diffusion ages for young, tall scarps. The slope-offset method is unbiased but has limited resolution because it requires many scarp profiles to yield a single diffusion age. A method that incorporates the full scarp profile and uncertainty in the initial scarp angle was found to be the most accurate technique. The application of the full-scarp method to the Bonneville shoreline supports the use of a linear diffusion model for scarps up to 20 m in height. Scarp orientation had no discernable effect on diffusivity values. Soil texture was found to have a weak but significant inverse relationship with diffusivity values.     

Factors influencing the presence or absence of tributary-junction fans in the Iberian Range, Spain

This paper analyses the factors which influence the presence or absence of tributary-junction fans in the Iberian Range, northern Spain. Two valleys were selected, both characterised by wide variations in lithology, altitude, land use and plant cover. Two groups of factors were studied: those related to the internal characteristics of the drainage basins, which particularly control sediment generation; and those related to the characteristics of the depositional area which control accommodation space and main river power. Among the internal factors, the development of alluvial fans was related to: (i) the capacity of the basin to yield large volumes of sediment, (ii) the occurrence of intense human pressure until recent times, a good indicator of sediment yield, and (iii) the capacity of the basin to quickly increase discharge during rainstorms (discharge density and torrentiality). It is suggested that the areas that were intensively cultivated in the past, and have therefore been affected by intense erosion, have played a decisive role on the development of alluvial fans. This would imply that many of these alluvial fans have a relatively recent origin, perhaps related to the beginning of a widespread deforestation. The basins without alluvial fans are characterised by relatively steep hillslope gradients (that is, slopes that never were subjected to historical cultivation), low drainage densities and dense forest and shrub cover, mostly coinciding with high altitude basins composed of quartzite and shale bedrocks. Regarding the external factors, the shape, size and longitudinal gradient of the main river to which the fans are tributary are the most relevant conditioning factors determining the development of alluvial fans.     

The evolution of groundwater in the Tyrrell catchment, south-central Murray Basin, Victoria, Australia

The Tyrell catchment lies on the western margin of the Riverine Province in the south-central Murray Basin, one of Australia’s most important groundwater resources. Groundwater from the shallow, unconfined Pliocene Sands aquifer and the underlying Renmark Group aquifer is saline (total dissolved solids up to 150,000 mg/L) and is Na-Cl-Mg type. There is no systematic change in salinity along hydraulic gradients implying that the aquifers are hydraulically connected and mixing during vertical flow is important. Stable isotopes (¹⁸O+²H) and Cl/Br ratios indicate that groundwater is entirely of meteoric origin and salts in this system have largely been derived by evapotranspiration of rainfall with only minor halite dissolution, rock weathering (mainly feldspar dissolution), and ion exchange between Na and Mg on clays. Similarity in chemistry of all groundwater in the catchment implies relative consistency in processes over time, independent of any climatic variation. Groundwater in both the Pliocene Sands and Renmark Group aquifers yield ages of up to 25 ka. The Tyrrell Catchment is arid to semi-arid and has low topography. This has resulted in relatively low recharge rates and hydraulic gradients that have resulted in long groundwater residence times.     

吉林伊通盆地莫里青断陷古近系双阳组储集层成岩作用研究

古近系双阳组是在吉林省伊通盆地莫里青断陷中，油气赋存的主要层位,储层主要为湖底扇和扇三角洲的砂体。依据双阳组储层的大量薄片、扫描电镜、粘土矿物分析的资料研究了该储集层的成岩作用。研究结果表明双阳组储集层：成岩作用经历了压实、压溶、胶结、交代和溶解6方面的作用。双储集层中的自生粘土矿物蒙皂石向伊利石转化具有明显的特征：主要演化过程经历了蒙皂石渐变带，第一迅速转化带和第二迅速转化带，相应的成岩作用阶段可划分为早成岩阶段B期、晚成岩阶段A1期和晚成岩阶段A2期。依据在垂向上的成岩变化,建立了莫里青断陷双阳组储集层的成岩作用演化序列。在垂向上成岩作用的类型和强度均存在明显的差异，造成了储层物性的垂向分带。     

REE/trace element characteristics of sandstone-type uranium deposits in the Ordos Basin

1 Introduction The Ordos Basin is the second largest sedimentary basin in China. During the last 10 years, a great progress has been achieved in the aspects of tectonic evolution, dynamics process, inner and outer geological processes during Mesozoic-Cen…     

裂缝性岩石裂缝扩展的光弹构造物理模拟——以南华北盆地户部寨沙河阶组为例

以南华北盆地户部寨第三系沙河阶组粉砂岩低渗透储层为例,总结了其中发育的5种类型构造裂缝组合,即:①南北向雁形张节理组成的共轭剪节理带;②东西向雁形张节理组成的共轭剪节理带;③缠结状多组剪切构造裂缝;④组合状交切的多组剪切构造裂缝及张裂缝;⑤散状无序排列的构造裂缝。在此基础上,建立光弹性试验构造物理模型,沿现应力场96°方向,均匀地对该模型逐步增加外载力。结果表明,沿各组合裂缝尖端分别形成对称于裂缝走向、且主轴垂直于裂缝的Ⅰ型等色线条纹;对称于裂缝走向、且主轴平行于裂缝走向的Ⅱ型条纹和斜交于裂缝走向的复合型(Ⅲ型)条纹。第①类组合裂缝尖端以Ⅰ型等色线条纹的拉张应力和张剪应力为主;第②类组合裂缝尖端以复合型(Ⅲ型)等色线条纹的挤压应力为主;第③、④和⑤类组合裂缝尖端的应力分布较为复杂。当模型外载荷接近1000kg时,裂缝尖端起裂,并开始发育显微裂缝,而当外载荷达1100-1200 kg时,沿裂缝尖端部位形成宏观裂缝,并开始扩展。5种类型的裂缝组合扩展发育程度由强至弱依次为:①,③,⑤,②,④。其中第①类共轭裂缝组合起裂最早,扩展最快,裂缝间的连通趋势最好,说明规则分布的构造裂缝组合,在垂直于外施加载衙时更易达到连通的目的。     

山西沁水盆地煤层气成藏的微观动力能条件研究

煤层气成藏的微观动力能条件主要包括煤储层的孔隙—裂隙系统、煤储层的生气作用和储气作用两个方面。以山西沁水盆地为例,深入剖析了煤储层的孔隙—裂隙系统及其发育历程、煤储层的生气作用与能量聚散,阐明了煤层气成藏的微观动力能对成藏效应的控制作用。结果表明:构造作用对储层渗透率具有明显的控制作用,成烃增压致使能量聚集,成为盖层突破作用的主要驱动力,而能量放散则主要是通过煤储层孔隙—裂隙系统的产生、发展。根据上述研究成果,沁水盆地煤层气成藏的地质区划结果为:盆地南部的有利区带为阳城和晋城的北部地区,包括潘庄、樊庄、郑庄等地区;盆地中部的有利区带为安泽—沁源地区,位于盆地西斜坡的中南部;盆地北部的可能有利区带为寿阳东南部地区,位于榆次东北部和阳泉西南部之间。