Interpretation of regional geophysical data for mapping subsurface geology and hydrogeology

解释区域地球物理数据以绘制地下地质和水文地质图

• 批准号: RGPIN-2014-04888
• 负责人: Smith, Richard
• 金额: $ 3.13万
• 依托单位: Laurentian University of Sudbury
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=588080
• 关键词: Interpretation; regional; geophysical; data; mapping

An important component of the resource exploration process is the collection of regional airborne geophysical data. When integrated with geological and geochemical data, an interpreter can use the geophysics to select sites for more detailed work that will assist in the discovery of minerals, hydrocarbons and groundwater. My research program is to develop innovative tools that will substantially improve the efficacy of airborne magnetic and electromagnetic methods. Airborne data are normally collected along flight traverses with samples every 5 to 15 m, but the traverses can be 100 m apart or more. These data are interpolated between the lines to generate a data set on a uniform “grid”. This interpolation process generally works well, but narrow features that trend at angles oblique to the flight lines are not well sampled, so the grid is not a good representation of the underlying geology, showing aliasing artifacts. The first project is to have a student develop a computer algorithm that is capable of generating a grid free of artifacts that better represents the underlying geology. This new algorithm would provide geoscientists with tools that they could use on a daily basis to generate better grids and hence understand the sub-surface geology and find earth resources more effectively. The second project will be for a graduate student to use the improved gridded data to determine the underlying geological source. The SLUTH method, developed previously, is good for estimating the depth to faults or dykes. A theoretical development would allow a student to develop an innovative new method for interpreting the depth and thickness of the geological feature. Airborne electromagnetic data are most important when looking for discrete highly conductive bodies. The way to determine if the conductive body is a valuable mineral deposit is to drill a hole aimed to intersect the body. A drill hole will only intersect the target if the depth and orientation of the target can be estimated correctly from the electromagnetic data. Project 3 will build on theoretical work that shows that the electromagnetic response of a body at an arbitrary inclination (dip) can be decomposed into the response of horizontal and vertical dipoles at the same depth. This enables a simple interpretation scheme to be developed for electromagnetic data that is similar to the automatic schemes used for magnetic data. It might also be possible to extend the theory to the case of arbitrary strike direction. A fourth project would involve calculating the response of the discrete conductor below conductive overburden, which is very important for exploring for resources in the "ring of fire" area in northern Ontario, an area where nickel and cobalt have recently been discovered. The fifth project would allow airborne electromagnetic data to be processed so as to directly map water in the subsurface using magnetic resonance imaging (MRI). These MRI methods are used with ground systems, but a cruder form of the technique that uses existing airborne electromagnetic data might be used to select areas that would warrant follow up with a ground system. The first four projects will develop into further projects in subsequent grant applications to improve our ability to map geology, understand geological processes, monitor the environment and explore for scarce mineral deposits. The fifth project is a proof of concept project; the technology will be further developed in subsequent grants, developing a cost effective technique for regional exploration for water. With the growing population on the planet and the development in Africa and Asia, water and mineral resources will be in strong demand and monitoring the environment will be very important.

资源勘探过程的一个重要组成部分是收集区域机载地球物理数据。 当与地质和地球化学数据相结合时，解释人员可以利用地球物理学来选择地点进行更详细的工作，这将有助于发现矿物、碳氢化合物和地下水。 我的研究计划是开发创新工具，大幅提高机载磁力和电磁方法的效率。 机载数据通常沿飞行轨迹收集，每 5 至 15 m 采样一次，但轨迹间隔可能为 100 m 或更远。 这些数据在线之间进行插值，以在统一的“网格”上生成数据集。 这种插值过程通常效果很好，但以与飞行线倾斜的角度趋势的狭窄特征没有得到很好的采样，因此网格不能很好地表示底层地质，显示出混叠伪影。 第一个项目是让学生开发一种计算机算法，能够生成不含人工制品的网格，更好地代表底层地质。 这种新算法将为地球科学家提供日常使用的工具，以生成更好的网格，从而了解地下地质并更有效地寻找地球资源。 第二个项目将让研究生使用改进的网格数据来确定潜在的地质来源。 先前开发的 SLUTH 方法适用于估计断层或堤坝的深度。 理论发展将使学生能够开发出一种创新的新方法来解释地质特征的深度和厚度。 在寻找离散的高导电体时，机载电磁数据最为重要。 确定导电体是否是有价值的矿藏的方法是钻一个旨在与导电体相交的孔。 仅当可以根据电磁数据正确估计目标的深度和方向时，钻孔才会与目标相交。 项目 3 将建立在理论工作的基础上，该工作表明物体在任意倾斜（倾角）下的电磁响应可以分解为同一深度处的水平和垂直偶极子的响应。 这使得能够为电磁数据开发一个简单的解释方案，该方案类似于用于磁数据的自动方案。 也有可能将该理论扩展到任意打击方向的情况。 第四个项目将涉及计算导电覆盖层下方分立导体的响应，这对于勘探安大略省北部“火环”地区的资源非常重要，该地区最近发现了镍和钴。 第五个项目将允许处理机载电磁数据，以便使用磁共振成像（MRI）直接绘制地下水图。 这些 MRI 方法与地面系统一起使用，但使用现有机载电磁数据的更粗略的技术形式可能用于选择需要地面系统跟进的区域。 前四个项目将在后续拨款申请中发展为进一步的项目，以提高我们绘制地质图、了解地质过程、监测环境和勘探稀有矿藏的能力。 第五个项目是概念验证项目；该技术将在后续赠款中得到进一步发展，为区域水资源勘探开发一种具有成本效益的技术。 随着地球上人口的增长以及非洲和亚洲的发展，对水和矿产资源的需求将会强劲，环境监测将变得非常重要。