郯庐断裂带早白垩世火山岩的K-Ar年龄及其构造意义

安徽肥东龙山和山东沂水道托火山岩的K-Ar全岩年龄分别为119.2±2.3Ma和114.8±1.0Ma,明显晚于郯庐断裂带左行平移时间(143.3±1.3Ma),与断裂带内张八岭隆起北段侵入岩中黑云母的⁴⁰Ar-³⁹Ar坪年龄(120~128Ma),以及南段肥东—巢湖地区的花岗岩中锆石定年结果(106.9~121.4Ma)一致,可能是断裂带伸展活动的产物。     

2022年10—12月全球火山活动简报

<正>0全球火山活动概况2022年10—12月全球共有67座火山出现活动,其中,警戒级别Ⅰ级的火山15座,警戒级别Ⅱ级的火山21座,警戒级别Ⅲ级的火山27座,警戒级别Ⅳ级的火山4座(表1)。从空间分布上看,绝大多数活动火山位于环太平洋火山带上,少数分布在地中海火山带西南段,个别活动火山处于板块交汇处和板块内部(图1);从分布国家来看,活动火山多集中在美国、俄罗斯、印度尼西亚、日本等国;“一带一路”沿线有7座火山出现活动,其中,印度尼西亚5座,意大利2座。2022年10—12月全球火山活动水平有所减弱,     

山东省烟台市观水镇白垩纪基岩裂隙水供水可行性分析

近年来,由于地下水污染问题加剧,山东省烟台市观水镇生活用水矛盾日益突出,急需寻找优质地下水缓解当地居民用水问题。通过水文地质调查、地球物理勘探、实施探采结合井、抽水试验和水质化验等手段,初步查明了观水镇及附近区域的蓄水构造类型及赋存规律,圈定了优质地下水的富水地段,论证了白垩纪基岩裂隙水供水可行性,为政府相关部门决策、解决村民吃水问题提供科学建议。     

Bedrock surface roughness and the distribution of subglacially precipitated carbonate deposits: implications for formation at Glacier de Tsanfleuron,Switzerland

Two carbonate deposits are identified on the exposed bedrock surface in the forefield of Glacier de Tsanfleuron, Switzerland: macrocrystalline sparite and microcrystalline micrite. Comparison of the distributions of these forms with lee-side slope facets identified by high-pass filtering of a flow-parallel bedrock profile at a range of frequencies reveals two significant results. First, while the distribution of sparite is consistent with formation in the lee side of subglacial bedrock hummocks, that of micrite is not. This contrasts with previous investigations in which both sparite and micrite have been considered to form by mineral concentration and precipitation during the refreezing of regelation-related basal meltwaters in the lee side of bedrock hummocks. Alternative mechanisms of micrite formation involving carbonate deposition and/or precipitation within subglacial bedrock hollows are proposed. Second, the distribution of sparite is most strongly correlated with the distribution of lee-side slope facets identified by filtering at a frequency equivalent to a hummock wavelength of c. 0·1 m. This correspondence indicates empirically that pressure-related melting and refreezing (regelation) operates most effectively around bedrock hummocks that are shorter than c. 0·1 m. © 1998 John Wiley & Sons, Ltd.     

试论水文地质纲要图的涵意

随着按图幅开展的1:5万水文地质调查工作的推进,水文地质图的编制愈显重要。如何编制易读、准确的水文地质图是摆在水文地质工作者面前的一个课题。通过多年探索,笔者针对基岩山区提出了水文地质纲要图的概念与内涵,并在沂蒙山区1:5万水文地质图编制中进行了尝试和探索。结果表明,以地下水系统为对象的区域性水文地质纲要图作为水文地质图的镶图,可使读者从地下水系统角度掌握区域水文地质条件及地下水运动规律,并且有助于图幅内容的理解。     

火山岩—侵入岩的联系

关于侵入岩和火山岩二者之间的联系,已有上百年的争论。该争论主要集中于中—酸性岩,对于长英质火山岩的岩浆来源目前主要有2种观点：（1）由花岗质岩浆的“晶粥”中的熔体抽离而来;（2）与同期侵入岩无关,具有独立的岩浆形成过程。近些年来,随着高精度定年测试方法的进步和地球物理等研究方式的介入,对长英质火山岩和侵入岩二者的成因联系有了新的认知,“晶粥”模型和“穿地壳岩浆系统”受到较多关注,但同时也带来了新的矛盾和问题。文章系统总结了火山岩与侵入岩联系的不同观点、历史沿革、以及不同研究方法引起的争议,展望了该领域未来研究前景;提出大数据总体上展现出的长英质火山岩和侵入岩之间强烈的地球化学相似性,但这种总体上的相似性并不排除特定区域某个火山—侵入杂岩中的火山岩和侵入岩之间存在地球化学的差异,并在成因上符合“晶粥”模型。文章指出,深部探测、原位精细分析和实验模拟是火山岩—侵入岩成因联系研究方面有望取得突破的重要研究方向,而将火山岩—侵入岩形成机制与大陆演化和环境变迁等问题的研究有机结合可能是未来的重要研究领域。     

Geochemical characteristics of ores and surface waters for environmental risk assessment in the Pinpet iron deposit,southern Shan State,Myanmar

Mining operations in the Pinpet Fe deposit, which is the second‐largest Fe deposit in Myanmar, are currently suspended, in part because of possible contamination of heavy metals and hazardous elements (e.g., Fe, As, Cu, Zn, and U) into the surrounding aquatic environment and associated public concern. However, a scientific investigation of the source and degree of contamination in streams near the deposit has not yet been conducted. Therefore, we quantified heavy‐metal and hazardous‐element concentrations of stream waters and sediments in stream beds, and measured the speciation and concentration of these metals in deposit Fe ores using the sequential extraction method, to better understand the influence of mining activities on the surrounding environment. Geochemical results for Nan‐tank‐pauk stream and its tributaries indicate that the chemical compositions of their waters are controlled by carbonate bedrock and that no detectable contamination has occurred as a result of mining activity or hematite and limonite ore beneficiation processes in either the wet or dry seasons. All measured heavy‐metal and hazardous‐element concentrations were below the World Health Organization standards for drinking water and the proposed national drinking water quality standards in Myanmar. Bulk chemical compositions of stream‐bed and tailings dam sediments show that As, Zn, and Cu concentrations are similar to those in uncontaminated sediments. Results of bulk mineralogical and chemical analyses of ore samples reveal that some limonite ore samples contain substantial amounts of As (up to 2 wt%). However, sequential extraction results indicate that most (>90%) of the As in these As‐rich ores is hosted in insoluble fractions (e.g., crystalline Fe hydroxides and clays). Therefore, arsenic is unlikely to be released into the aquatic environment by interacting with water during ore beneficiation processes should the mine resume operations.     

Weathering and erosion of fractured bedrock systems

We explore the contribution of fractures (joints) in controlling the rate of weathering advance for a low‐porosity rock by using methods of homogenization to create averaged weathering equations. The rate of advance of the weathering front can be expressed as the same rate observed in non‐fractured media (or in an individual block) divided by the volume fraction of non‐fractured blocks in the fractured parent material. In the model, the parent has fractures that are filled with a more porous material that contains only inert or completely weathered material. The low‐porosity rock weathers by reaction‐transport processes. As observed in field systems, the model shows that the weathering advance rate is greater for the fractured as compared to the analogous non‐fractured system because the volume fraction of blocks is < 1. The increase in advance rate is attributed both to the increase in weathered material that accompanies higher fracture density, and to the increase in exposure of surface of low‐porosity rock to reaction‐transport. For constant fracture aperture, the weathering advance rate increases when the fracture spacing decreases. Equations describing weathering advance rate are summarized in the ‘List of selected equations’. If erosion is imposed at a constant rate, the weathering systems with fracture‐bounded bedrock blocks attain a steady state. In the erosional transport‐limited regime, bedrock blocks no longer emerge at the air‐regolith boundary because they weather away. In the weathering‐limited (or kinetic) regime, blocks of various size become exhumed at the surface and the average size of these exposed blocks increases with the erosion rate. For convex hillslopes, the block size exposed at the surface increases downslope. This model can explain observations of exhumed rocks weathering in the Luquillo mountains of Puerto Rico. Published 2017. This article is a U.S. Government work and is in the public domain in the USA     

MICROSTRUCTURAL FEATURES AND IMPLICATIONS OF FAULT GOUGE FROM THE FAULTS OF BEDROCK REGION IN THE CENTRAL-NORTHERN JIANGXI PROVINCE,CHINA

How to survey fault activity and determine seismogenic structures in a relatively stable and bedrock-distributed region is a challenging research work. Ruichang-Tonggu Fault and Yifeng-Jingdezhen Fault, distributed mainly at the pre-Cenozoic bedrock region, show the geological evidences of activity in the Quaternary and they are two important tectonic belts for the occurrence of moderate earthquakes in the central-northern Jiangxi Province. Fault gouge stripes can be found on the outcrop sections of the two faults. The imageries of the microstructures of fault gouge show abundant phenomena about the structural deformation, and it is clear that the fault gouge was formed by structural activity. As to the deformation modes, there are not only the Y-shears and R1-shears, which represent the localized-brittle deformation, but also the P-foliations, which reflect the ductile deformation in the microstructures of fault gouge. These features demonstrate that the micro-scale rapid deformation can exist in the seismogenic structure at the near-surface in the occurrence process of moderate earthquakes very possibly. The microstructures of soft material from the fault outcrop section at the southern segment of Hukou-Xingan Fault, which is inactive in the Quaternary, reflects that the soft material from the fault zone can also be the products of rainwater leaching and filling, or weathering in the later periods. Based on the macroscopic observation in the field, it is sometimes difficult to distinguish the differences of structurally-formed or non-structurally formed soft gunk in the fault zones, however, their differences in the microstructure on the slices grinded indoor are obvious. The relatively stable bedrock areas in South China often are not only favorable for the siting of major projects, such as nuclear power plant in China, but also the economically-developed, densely populated, urban agglomeration areas. The study of microstructure of fault gouge provides a technical reference approach for the identification of fault activity and the determination of seismogenic structure of moderate-strong earthquakes in assessing the seismotectonic environment in these regions.