Review paper: Exploration geophysics for intrusion‐hosted rare metals

Igneous intrusions, notably carbonatitic–alkalic intrusions, peralkaline intrusions, and pegmatites, represent significant sources of rare‐earth metals. Geophysical exploration for and of such intrusions has met with considerable success. Examples of the application of the gravity, magnetic, and radiometric methods in the search for rare metals are presented and described. Ground gravity surveys defining small positive gravity anomalies helped outline the shape and depth of the Nechalacho (formerly Lake) deposit within the Blatchford Lake alkaline complex, Northwest Territories, and of spodumene‐rich mineralization associated with the Tanco deposit, Manitoba, within the hosting Tanco pegmatite. Based on density considerations, the bastnaesite‐bearing main ore body within the Mountain Pass carbonatite, California, should produce a gravity high similar in amplitude to those associated with the Nechalacho and Tanco deposits. Gravity also has utility in modelling hosting carbonatite intrusions, such as the Mount Weld intrusion, Western Australia, and Elk Creek intrusion, Nebraska. The magnetic method is probably the most successful geophysical technique for locating carbonatitic–alkalic host intrusions, which are typically characterized by intense positive, circular to sub‐circular, crescentic, or annular anomalies. Intrusions found by this technique include the Mount Weld carbonatite and the Misery Lake alkali complex, Quebec. Two potential carbonatitic–alkalic intrusions are proposed in the Grenville Province of Eastern Quebec, where application of an automatic technique to locate circular magnetic anomalies identified several examples. Two in particular displayed strong similarities in magnetic pattern to anomalies accompanying known carbonatitic or alkalic intrusions hosting rare‐metal mineralization and are proposed to have a similar origin. Discovery of carbonatitic–alkalic hosts of rare metals has also been achieved by the radiometric method. The Thor Lake group of rare‐earth metal deposits, which includes the Nechalacho deposit, were found by follow‐up investigations of strong equivalent thorium and uranium peaks defined by an airborne survey. Prominent linear radiometric anomalies associated with glacial till in the Canadian Shield have provided vectors based on ice flow directions to source intrusions. The Allan Lake carbonatite in the Grenville Province of Ontario is one such intrusion found by this method. Although not discovered by its radiometric characteristics, the Strange Lake alkali intrusion on the Quebec–Labrador border is associated with prominent linear thorium and uranium anomalies extending at least 50 km down ice from the intrusion. Radiometric exploration of rare metals hosted by pegmatites is evaluated through examination of radiometric signatures of peraluminous pegmatitic granites in the area of the Tanco pegmatite.     

Multi‐dimensional analyses of the SEAM controlled source electromagnetic data—the story of a blind test of interpretation workflows

Using a subset of the SEG Advanced Modeling Program Phase I controlled‐source electromagnetic data, we apply our standard controlled‐source electromagnetic interpretation workflows to delineate a simulated hydrocarbon reservoir. Experience learned from characterizing such a complicated model offers us an opportunity to refine our workflows to achieve better interpretation quality. The exercise proceeded in a blind test style, where the interpreting geophysicists did not know the true resistivity model until the end of the project. Rather, the interpreters were provided a traditional controlled‐source electromagnetic data package, including electric field measurements, interpreted seismic horizons, and well log data. Based on petrophysical analysis, a background resistivity model was established first. Then, the interpreters started with feasibility studies to establish the recoverability of the prospect and carefully stepped through 1D, 2.5D, and 3D inversions with seismic and well log data integrated at each stage. A high‐resistivity zone is identified with 1D analysis and further characterized with 2.5D inversions. Its lateral distribution is confirmed with a 3D anisotropic inversion. The importance of integrating all available geophysical and petrophysical data to derive more accurate interpretation is demonstrated.     

月球线性构造分类体系研究

月球线性构造是月球科学研究中的重要组成部分,建立月球线性构造分类体系是月球地质图编研的关键。前人对月球线性构造的分类研究主要基于月表的形貌特征,划分的线性构造类型参差不齐,尚未形成一个公认的、规范的、具有普适性的线性构造分类体系,以至于分类结果的可对比性差、参考性和易操作性较低,不利于月球线性构造纲要图的编制。并且月球线性构造的概念混乱、术语不统一,存在"同物异名、同词异义、异词同义、涵义不明"的现象,不利于全球性的统一制图和成果的展示及使用。鉴于此,本文采用多指标组合的分类方法,以成因机制和形貌特征作为主要指标,兼顾物质组成,再结合线性构造形成的动力学机制,建立了符合月球动力学演化背景的、统一规范的线性构造类型划分的新方案,避免了单以形貌特征为依据来分类出现的混乱状态,具有较好的科学性和可操作性。将月球的线性构造类型划分为:内动力地质作用形成的线性构造,包括皱脊、月溪、地堑、断裂;外动力地质作用形成的线性构造,包括坑缘断裂和坑底断裂,以及多成因机制、多动力来源作用形成的特殊类型如坑链等。在此基础上,并利用多源遥感数据建立了易于判别且具有代表性的线性构造识别标志,可为全月球线性构造的统一制图提供识别依据。     

Automatic interpretation of digital maps

In the past, the availability and/or the acquisition of spatial data were often the main problems of the realization of spatial applications. Meanwhile this situation has changed: on one hand, comprehensive spatial datasets already exist and on the other hand, new sensor technologies have the ability to capture fast and with high quality large amounts of spatial data. More and more responsible for the increasing accessibility of spatial data are also collaborative mapping techniques which enable users to create maps by themselves and to make them available in the internet. However, the potential of this diversity of spatial data can only hardly be utilized. Especially maps in the internet are represented very often only with graphical elements and no explicit information about the map’s scale, extension and content is available. Nevertheless, humans are able to extract this information and to interpret maps. For example, it is possible for a human to distinguish between rural and industrial areas only by looking at the objects’ geometries. Furthermore, a human can easily identify and group map objects that belong together. Also the type, scale and extension of a map can be identified under certain conditions only by looking at the objects’ geometries. All these examples can be subsumed under the term “map interpretation”. In this paper it is discussed how map interpretation can be automated and how automatic map interpretation can be used in order to support other processes. The different kinds of automatic map interpretation are discussed and two approaches are shown in detail.     

The First James K. Mitchell Lecture In situ soil testing: from mechanics to interpretation†

The current use of fundamental mechanics in developing rational interpretation methods for deriving soil properties from in situ test results is reviewed and evaluated. The focus is on some of the most widely used in situ test devices including cone penetrometers with and without pore pressure measurements (CPTU and CPT), self-boring and cone pressuremeters (SBPMT and CPMT), and flat dilatometers (DMT). In situ tests in both cohesive and frictional soils for measuring strength and stiffness properties, in situ state parameters, consolidation coefficients, stress history, and in situ stresses are considered in detail.     

霍州矿区隐伏断裂（带）活动性氡气测试成果解释分析

采用断层气体测试方法,对霍州盆地矿区内几条主要的隐伏断裂（带）及其活动性进行了测试。进而对该区典型的氡气测试成果剖面作了解释分析,并判别了隐伏断裂（带）的空间分面具主其相对活动强弱与活动水平等有关断裂活动性问题。     

低孔低渗储层渗透率测井解释模型研究

采用岩心分析数据与测井曲线相结合的方法,引入泥质含量参数配合声波时差进行多元线性回归分析。建立鄂尔多斯盆地研究区低孔低渗储层渗透率测井解释模型。根据泥质含量特征二次分类后进行多元线性回归,建立两个渗透率测井解释模型相关性良好,对应于研究区两种不同的沉积微相特征;测井解释渗透率与岩心实测渗透率匹配良好,解释模型满足研究区精度要求。在沉积微相背景约束条件下,对研究区储层选择合理参数多元线性回归建立渗透率测井解释模型,可以使低孔低渗储层渗透率解释达到良好应用效果。     

基于无人机影像的辽宁农居建筑物提取技术与应用研究

本研究以实地调研数据为基准,无人机影像数据分析为验证,进行了基于无人机识别能力范畴的辽宁农居建筑结构类型划分,并根据区域结构类型比例、影像特性等指标优化了农居遥感解译标志整体参数,提取了不同建筑结构的不同解译标志阈值区间,并基于无人机低空正射影像DOM、数字表面模型DSM制定改进型DSM提取算法处理流程与代码,利用Python语言及开发环境完成了遥感影像要素提取与评估系统开发应用。通过最优组合解译标志获取无人机影像解译一致性系数Kappa=0.723,表明制定的解译标志特征对获得具有较好一致性的房屋结构类型具备一定的可行性。以改进型DSM提取算法为核心的建筑物提取软件提取建筑的整体精度为75%,基本满足地震应急需求。     

瞬变电磁法在富盛铅锌矿上的应用

简要介绍了瞬变电磁法原理和特点、WDC－2B型瞬变电磁勘探系统及其野外工作方法。在充分考虑富盛铅锌矿地质矿产和物性特征的基础上，重点应用重叠回线装置，研究已知矿体上方的瞬变电磁响应特征及其与地质矿产的联系，提出了在富盛铅锌矿地质物性条件下，瞬变电磁响应模式为“上凹下凸”，同时对矿区外围发现的瞬变电磁响应异常，结合矿区的地质物性资料进行了初步解释。     

Perspectives on Quaternary outreach and aspirations for the future

Outreach arising from the study of the British Quaternary offers many benefits for society, especially because of its relevance for understanding contemporary environmental issues and environmental change. Outreach is also important for the long-term health of the academic discipline and research agenda. Through engaging with the formal education system, institutions, policy makers, planners and with the public at large, Quaternary specialists can do much to advance interest in and appreciation of the British landscape and its Quaternary record. This opinion and review article considers the importance and benefits of outreach in its many forms, makes the case for practitioners to continue and increase their involvement, offers examples of good practice, and sets out aspirations for the future.