Uncovering the deep structure of the Koillismaa Layered Intrusion Complex, Finland using a novel 3D seismic survey

Malinowski, Michał; Karinen, Tuomo; Autio, Uula; Heinonen, Suvi; Singh, Brij; Górszczyk, Andrzej; Sito, Łukasz; the SEEMS DEEP Working Group,

doi:10.5194/se-16-1437-2025

Articles | Volume 16, issue 11

https://doi.org/10.5194/se-16-1437-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

Seismic imaging from the lithosphere to the near surface

https://doi.org/10.5194/se-16-1437-2025

© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 16, issue 11

Research article

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20 Nov 2025

Research article | Highlight paper |

| 20 Nov 2025

Uncovering the deep structure of the Koillismaa Layered Intrusion Complex, Finland using a novel 3D seismic survey

Michał Malinowski, Tuomo Karinen, Uula Autio, Suvi Heinonen, Brij Singh, Andrzej Górszczyk, Łukasz Sito, and the SEEMS DEEP Working Group

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Final revised paper (published on 20 Nov 2025)
Preprint (discussion started on 07 Jul 2025)

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-3111', Anonymous Referee #1, 23 Jul 2025

The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3111/egusphere-2025-3111-RC1-supplement.pdf

Citation: https://doi.org/10.5194/egusphere-2025-3111-RC1
- AC1: 'Reply on RC1', Michal Malinowski, 27 Sep 2025
  
  I would like to thank Reviewer 1 for a very positive evaluation of our manuscript. Most of the comments left in the annotated manuscript were implemented in the revised version.
  Below, we add some additional explanation.
  Regarding the comment on p.19, L316 on the “circular reasoning” related to the work of Deemer and Hurich. In fact, we first refer to the paper of Deemer & Hurich (1994), where the authors are performing the modelling of seismic response of mafic intrusions. In the commented sentence, we refer to a 1997 paper, where the authors specifically describe layered series of Sonkndal-Bjerkreim intrusion.
  Regarding the comment about the Fresnel zone migration (p. 20, L344), we don’t specifically mention this type of migration, however the cited reference of Singh et al (2019) includes a comparison of standard Kirchhoff PreSDM and Fresnel Volume Migration.
  On behalf of the authors,
  Michal Malinowski
  
  Citation: https://doi.org/10.5194/egusphere-2025-3111-AC1
RC2:
'Comment on egusphere-2025-3111', Anonymous Referee #2, 29 Jul 2025

The work by Malinowski et al introduces the results of a newly acquired 3D seismic survey along thee known Koillismaa intrusion in Finland. The work starts with an overview of relevant references, compilation of existing petrophysical data to constrain the origin of reflectivity as seen in the 3D seismic results, along with incorporating existing density information and gravity inversion to validate the results further. The 3D results are incorporated together with 2D seismic and potential field inversion results acquired along the same site into a Common Earth Model of the site, offering new insight into its geological evolution, along with discussing the origin of reflectors seen in a broader sense.

Although 5D interpolation was used to improve the coherency of the reflections seen in the 3D seismic data, given the terrain difficulty, along with the authors themselves discussing the potential artifact zones introduced by this step, and as seen in the results themselves, I find this step relevant and appropriately applied and enhancing the reflectors with minimal artifact introduction.

Overall, I really enjoyed reading this paper and congratulate the authors on an excellent work. Besides very few technical comments, find it publication ready.

Keep up the good work!

Citation: https://doi.org/10.5194/egusphere-2025-3111-RC2
- AC2: 'Reply on RC2', Michal Malinowski, 27 Sep 2025
  
  I want to thank Reviewer 2 for a very positive evaluation of our manuscript. Most of the comments left in the annotated manuscript were implemented in the revised version.
  Below, we add some additional explanation.
  Comment on Figure 2. It is not possible to add the vertical axis, as the lithologies are roughly sorted by their depth occurrence. Still, they are repeated throughout the drillhole, e.g., diabase occurs at ca. 500-600 m depth, but also at ca. 900 and 1300 m depth.
  Comment on the depth axis in Figure 3. The vertical axis shows “structural height”, which, in the case of the layered intrusions, is counted from the bottom of the layered series (see Karinen, 2010).
  Comment on Figure 5: regarding the origin of "ringing" seen at approximately 125 Hz? We don’t have a clear answer to that. We can speculate that it is because of the sensor response, which is supposed to be flat till ca. 125 Hz. When merging the data, the system is by default applying a high-cut filter above 125 Hz; however, in our case, this filter was removed to improve the high-frequency response.
  Comment on p. 15 regarding the work of Gislason et al. This is discussed in depth in a companion paper by Singh et al. 2025: there are similarities between the two collocated profiles shot in 2018 and 2023; however, the 2023 data show much more continuous reflections, and the overall data quality is much higher.
  On behalf of the authors,
  Michal Malinowski
  
  Citation: https://doi.org/10.5194/egusphere-2025-3111-AC2

Peer review completion

AR – Author's response | RR – Referee report | ED – Editor decision | EF – Editorial file upload

AR by Michal Malinowski on behalf of the Authors (27 Sep 2025) Author's response Author's tracked changes Manuscript

ED: Publish as is (04 Oct 2025) by Christopher Juhlin

ED: Publish as is (07 Oct 2025) by CharLotte Krawczyk (Executive editor)

AR by Michal Malinowski on behalf of the Authors (13 Oct 2025)

Executive editor

The presented seismic exploration experiment exhibits the potential of using a low-cost survey design for 3-D imaging of the subsurface. In this case study, a deep layered intrusion and its feeder system are investigated. The new insights into the tectonic evolution and mineralization potential of the studied region in Finland evidences a complex, layered system rather than a simple magma channel. Furthermore, a major fault is identified that may influence how the development of mineral deposits in the area are interpreted. In summary, this work offers new tools and insights for exploring valuable underground resources in hard rock environments. This is a timely scientific result not only for Europe but has influence on people's sustainable living worldwide.