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Reverse time migration (RTM) imaging of iron-oxide deposits in the Ludvika mining area, Sweden
Solid Earth ( IF 3.4 ) Pub Date : 2020-10-26 , DOI: 10.5194/se-2020-181
Yinshuai Ding , Alireza Malehmir

Abstract. To discover or delineate mineral deposits and other geological features such as faults and lithological boundaries in their host rocks, seismic methods are a qualified choice, given their resolution power at depth. One major goal for seismic methods is to produce a reliable image of the subsurface given the typical discontinuous geology in crystalline environment with low signal-to-noise ratio. In this study, we investigate the usefulness of reverse time migration (RTM) imaging algorithm in hardrock environment by applying it to a legacy 2D dataset, which was acquired in the Ludvika mining area of central Sweden. We provide a how-to solution for applications of RTM in future and similar datasets. When using the RTM imaging technique properly, it is possible to obtain high-fidelity seismic images of the subsurface. Due to good amplitude preservation in the RTM image, the imaged reflectors provide indications to infer their geological origin. Aside from the chosen seismic imaging algorithm, we illustrate that two other important factors for successful RTM imaging workflows are the suitable acquisition and careful data pre-processing. Exemplified with the Ludvika legacy data, the RTM method allows imaging the iron-oxide deposits at a great level of detail down to 1200 m depth as shown from previous studies. It also provides much-improved images of the lithological contacts and crosscutting features relative to the mineralized sheets. Some of the imaged crosscutting features are considered to be crucial when interpreting large-scale geological structures of the site and the likely disappearance of mineralization at depth. The RTM imaging workflows have the potential to be used on hardrock seismic data and for deep targeting mineral deposits, a key message we would like to deliver in this article.

中文翻译:

瑞典卢德维卡矿区氧化铁矿床的逆时偏移(RTM)成像

摘要。为了发现或描绘其沉积岩中的矿床和其他地质特征(例如断层和岩性边界),考虑到其在深度上的分辨能力,地震方法是一种合格的选择。地震方法的一个主要目标是在低信噪比的晶体环境中,在典型的不连续地质条件下,产生地下的可靠图像。在这项研究中,我们通过将反向时间偏移(RTM)成像算法应用于遗留的2D数据集来研究其在硬岩环境中的有效性,该数据集是在瑞典中部的Ludvika矿区获得的。我们为RTM在未来和类似数据集中的应用提供了一个解决方案。正确使用RTM成像技术时,可以获得地下的高保真地震图像。由于RTM图像中的振幅保持良好,因此成像的反射器可提供推断其地质起源的指示。除了选择的地震成像算法之外,我们还说明了成功的RTM成像工作流程的另外两个重要因素是合适的采集和仔细的数据预处理。以Ludvika的遗留数据为例,RTM方法可以对低至1200 m深度的大量铁氧化物成像,如先前研究所示。它也提供了相对于矿化板的岩性接触和横切特征的大大改进的图像。在解释现场的大规模地质结构以及深部矿化的可能消失时,一些成像的横断面特征被认为是至关重要的。
更新日期:2020-10-30
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