Abstract. Many metallic mineral deposits have sufficient contrasts, particularly density, to be detectable using seismic methods. These deposits are sometimes significant for our society, economic growth and can help to accelerate the energy transition towards decarbonization. However, their exploration at depth requires high-resolution and sensitive methods. Following a series of 2D seismic trials, a sparse, narrow source-receiver azimuth, 3D seismic survey was conducted in the Blötberget mine, in central Sweden, covering an area of approximately 6 km² for deep targeting iron-oxide deposits and their host rock structures. The survey benefited from a collaborative work by putting together 1266 seismic recorders and a 32t vibrator generating 1056 shot points in a fixed geometry setup. A linear sweep ranging from 10–160 Hz and 20 s long was generated three times per shot point. Shots were fired at every 10 m where possible and receivers placed at every 10–20 m. Notable quality data were acquired although the area is dominated by swampy places as well as by built-up roads and historical tailings. The data processing had to overcome these challenges in particular for the static corrections and strong surface-waves. A tailored for hardrock-setting-processing workflow was developed for handling such a dataset, where the use of mixed 2D and 3D refraction static corrections were relevant. The resulting seismic volume is rich in terms of reflectivity with clear southeast dipping reflections originated from iron-oxide deposits extending vertically and laterally at least 300 m beyond what was known from boreholes. We estimate potential additional resources from the 3D reflection seismic experiment on the order of 10 Mt worth drilling for detailed assessments. The mineralization is crosscut by at least two major sets of northwest dipping reflections interpreted to be dominantly normal faults and responsible for much of the lowland in the Blötberget area. Moreover, these post-mineralization faults likely control the current 3D geometry of the deposits. Curved and submerged reflections interpreted from folds or later intrusions are also observed showing the geological complexity of the study area. The seismic survey also delineates the near-surface expression of a historical tailing as a by-product of refraction static corrections demonstrating why 3D seismic data. The sparse 3D survey illustrates that performing cost-effective reflection surveys for mineral exploration is achievable if they are conducted and planned carefully, systematically and based on earlier experiences.

中文翻译：

---

深度目标氧化铁矿床及其宿主岩石的稀疏3D反射地震勘测，卢德维卡矿山-瑞典

摘要。许多金属矿物沉积物具有足够的对比度，尤其是密度，可以使用地震方法进行检测。这些沉积物有时对我们的社会和经济增长具有重要意义，并且可以帮助加速向脱碳的能源过渡。但是，他们的深入勘探需要高分辨率和敏感的方法。在一系列2D地震试验之后，在瑞典中部的Blötberget矿进行了稀疏，狭窄的源接收方方位角3D地震勘测，覆盖了大约6 km ²用于深层定位的氧化铁矿床及其宿主岩石结构。这项调查得益于协作工作，将1266台地震记录仪和一台32t振动器组合在一起，以固定的几何结构产生了1056个点。每个发射点产生三次，范围从10–160 Hz到20 s的线性扫描。在可能的情况下，每10 m发射一次射击，每10– 20 m放置接收器。尽管该地区主要是沼泽地，人行道和历史尾矿，但仍获得了值得注意的质量数据。数据处理必须克服这些挑战，尤其是在静态校正和强表面波方面。为处理这样​​的数据集开发了针对硬岩镶嵌处理工作流的量身定制的应用程序，其中需要使用混合的2D和3D折射静态校正。所产生的地震量在反射率方面很丰富，东南向的清晰反射来自铁氧化物沉积物，这些氧化物在垂直和水平方向延伸至少超过了井眼已知的深度300m。我们估计3D反射地震实验的潜在额外资源约为10 Mt钻探量，以进行详细评估。矿化作用被至少两套西北倾斜反射的横切面解释为主要是正断层，是布洛特贝格地区大部分低地的原因。此外，这些矿化后的断层可能控制了矿床的当前3D几何形状。还观察到从褶皱或后来的侵入体解释的弯曲和淹没反射，显示了研究区域的地质复杂性。地震勘测还描绘了历史尾矿的近地表述，作为折射静态校正的副产品，从而说明了为什么使用3D地震数据。稀疏的3D调查表明，如果仔细，系统地并根据较早的经验进行和计划，则可以进行具有成本效益的矿物勘探反射调查。