than at seawater temperature (e.g., Chandra and Gerson, 2010; Fallon et al., 2017). Then, if the long-lived LT activity identified in the TAG hydrothermal field reveals to be a common process in other hydrothermal fields hosting old SMS deposits, this process should be considered in future studies on biogeochemical cycles of metals in the deep ocean. In addition, such sustained LT activity (10°C–30°C) in a sulfide-rich environment (i.e., SMS) may support diverse mesophilic microbial populations for long durations (Zeng et al., 2021).

## 5.7 Defining active, inactive, and extinct SMS deposits: insight from the TAG hydrothermal field

With increasing interest in polymetallic sulfides, part of the scientific community working on hydrothermal systems calls for the protection of active hydrothermal sites (Van Dover et al., 2018). As a consequence, potential mining activity would be focused on so-called inactive/extinct sites, though only few studies have been carried out on these deposits. Some authors recently advocated for research efforts to propose a classification of inactive and extinct deposits/vent fields that could help for mining regulations (Jamieson and Gartman, 2020; Van Dover et al., 2020). To our knowledge, the International Seabed Authority (ISA) has only proposed a definition for inactivity and extinction at vent-scale with distinction based on potential hydrothermal rejuvenation from mining activity (ISBA/25/LTC/6 Rev.2, 2022). Jamieson and Gartman (2020) argued that the term “extinct” should be only used for deposits hosted in an inactive vent field for which the probability of hydrothermal rejuvenation is low (but not certain). Considering that TAG hydrothermal mounds are all linked to the same heat source and a common detachment fault system that controls the hydrothermal circulation, Jamieson and Gartman (2020) classified the TAG field as hydrothermally active. This recommendation is relevant, particularly now knowing that all hydrothermal zones in the TAG field exhibit temperature anomalies. However, defining the extent of a single hydrothermal vent field (i.e., cluster(s) of deposits related to a common heat source and/or subseafloor permeability) may be challenging. That is true for TAG, where the location of the heat source and by extension the pattern of hydrothermal circulation is now disputed (e.g., McCaig et al., 2010; Guo et al., 2023). Moreover, the question of geological continuity may arise if inactive sulfide deposits are discovered toward the LTZ at depths shallower than the detachment fault termination (approximately 3,300 m, Graber et al., 2020). As a consequence, considering knowledge gaps and based on a precautionary approach, all known and to-be-discovered deposits belonging to the TAG area (including HTZ and LTZ, i.e., approximately 45 km²) should be grouped within a single field or district classified as hydrothermally active.

For an inactive field, Jamieson and Gartman (2020) proposed a set of indicators such as the absence of an upright chimney, relatively flat mound, lack of fluid venting, and absence of a vent biological community that may be important to distinguish extinct sites from inactive sites. These criteria are most likely diagnostic for prolonged HT hydrothermal inactivity. The discovery of a long-lived low-temperature hydrothermal activity in the TAG area

indicates that deposits with flat morphologies, no more standing chimneys, and a thick Fe–Mn hydrothermal crust may still host hydrothermal activity. Since the episodicity of low-temperature activity is not known, documentation and dating of LT precipitates should be considered to improve the definition of inactivity and extinction. New data arising from active and inactive hydrothermal field exploration programs are essential to fill gaps in scientific knowledge regarding the geology and ecology of inactive/extinct SMS deposits.

## 6 Conclusion

Extensive dive exploration, sampling, and measurements coupled with high-resolution acoustic data provide new insights on the nature of mafic-hosted SMS deposits as well as their spatial and temporal distribution and evolution in the TAG hydrothermal field. Our conclusions can be summarized as follows:

1) Thirteen new hydrothermal deposits were discovered including six large (>5,000 m²) deposits. The TAG hydrothermal field currently hosts 28 hydrothermal mounds accumulating 21.1 Mt of hydrothermal materials deposited above the seafloor.

2) Large and mature SMS deposits are mostly characterized by low copper and zinc concentrations compared to mafic-hosted volcanogenic massive sulfides. This questions the economic potential of large mafic-hosted SMS deposits in slow-spreading ridge settings.

3) LT activity (3°C–29°C) is identified in eight different areas including five newly discovered zones of diffuse venting. The spatial distribution of present sites of venting questions the geometry of sub-surface circulation patterns within the hanging wall and should be considered in future 3D flow modeling.

4) Shimme The distribution, morphology, mineralogy, and geochemistry of the hydrothermal deposits can be used to propose a new chronologic framework of the sulfide formation. HT activity was mainly focused in the ring zone and the Nautilus zone until 50 kyrs ago. A migration of HT activity to the Alvin zone, MIR zone (e.g., MIR mound), and active mound is likely since 50 kyrs, including different periods of activity (50–40 kyrs, 20–10 kyrs, 5 kyrs, 3,000–500 yrs, and 60 yrs) and inactivity. Excluding the recent rejuvenation of the Active mound at 60 yrs, last HT hydrothermal activity of the TAG field was focused in the western part of the MIR mound and at Shinkai mound, New Mound #2 and #3, and Mont de reliques.

5) Widespread LT crusts covering old flattened SMS mounds indicate that LT hydrothermal events can occur long after ceasing of the last HT hydrothermal activity. This finding indicates that old SMS deposits might be discovered to the east toward the LTZ. Long-lived LT hydrothermal activity (>140 kyrs to present) is a major process in the evolution and aging of SMS mounds in the TAG hydrothermal field, and its consequences on the fate of metals and microbial processes should be investigated in the future.

6) As already mentioned by Jamieson and Gartman (2020), none of the hydrothermal deposits belonging to the TAG area should
be considered extinct. Without additional constraints on the sub-surface fluid flow pathways, all deposits should be grouped in a single hydrothermal field (including the HTZ and LTZ) classified as “active.”

Further exploration to the north of the Shimmering zone and east of the Alvin, Nautile, and MIR zones is needed to fully understand the extension of the TAG SMS district. New radiometric dating of sulfides, Mn oxides, and aragonite of well-localized samples is also of prime importance to better constrain the temporal evolution of the TAG hydrothermal field. Knowing the spatial and temporal distribution of active, weakly active, and inactive SMS deposits would help constrain the present and past upflow zones and hence evolution of convection cell(s) associated with the development of detachment fault systems.

## Data availability statement

The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found in the article/Supplementary Material.

## Author contributions

E-LP: conceptualization, investigation, writing—original draft, and writing—review and editing. MP: writing—review and editing. A-SA: data curation, methodology, and writing—review and editing. AB: formal analysis, validation, and writing—review and editing. SC: formal analysis and writing—review and editing. FB: formal analysis and writing—review and editing. VA: formal analysis and writing—review and editing. CG: data curation, formal analysis, and writing—review and editing. AG: formal analysis and writing—review and editing. DP: formal analysis and writing—review and editing. MR: formal analysis and writing—review and editing. TG: writing—review and editing. LG: formal analysis and writing—review and editing. CC: writing—review and editing. M-AC: writing—review and editing. YF: supervision and writing—review and editing.

## References

Bohnenstiehl, D. R., and Kleinrock, M. C. (2000). Fissuring near the TAG active hydrothermal mound, 26°N on the Mid-Atlantic Ridge. *J. Volcanol. Geotherm. Res.* 98, 33–48. doi:10.1016/S0377-0273(99)00192-4

Bonatti, E., Kraemer, T., and Rydell, H. (1972). Classification and genesis of submarine iron-manganese deposits, in, *Ferromanganese Deposits of the Ocean Floor*. Editor D. R. Horn (Washington D.C., United States: Seabed Assessment Program, IDOE, NSF), 149–166.

Cambon, M. -A. (2014). BICOSE cruise. *RV Pourquoi pas?* doi:10.17600/14000100

Canales, J. P., Sohn, R. A., and deMartin, B. J. (2007). Crustal structure of the Trans-Atlantic Geotraverse (TAG) segment (Mid-Atlantic Ridge, 26°10′N): implications for the nature of hydrothermal circulation and detachment faulting at slow spreading ridges. *Geochem. Geophys. Geosyst.* 8, Q08004. doi:10.1029/2007GC001629

Cathles, L. M. (2011). What processes at mid-ocean ridges tell us about volcanogenic massive sulfide deposits. *Min. Deposita* 46, 639–657. doi:10.1007/s00126-010-0292-9

Chandra, A. P., and Gerson, A. R. (2010). The mechanisms of pyrite oxidation and leaching: a fundamental perspective. *Surf. Sci. Rep.* 65, 293–315. doi:10.1016/j.surfrep.2010.08.003

## Funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. The HERMINE2 expedition (2022) was carried out thanks to the France 2030 government funding for the “deep sea”—“Projet Mission DMA et CCZ”—ANR-22-MAFM-001.”

## Acknowledgments

The authors thank the crews of R/V Pourquoi pas? and Nautile HOV and all participants of the BICOSE, HERMINE, and HERMINE2 cruises for their assistance at sea. We thank reviewers J-II, JK and JJ for their thoughtful comments and suggestions, which significantly improved the quality of this paper.

## Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

## Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors, and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

## Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/feart.2024.1304993/full#supplementary-material

Cherkashev, G. A., Ivanov, V. N., Bel'tenev, V. I., Lazareva, L. I., Rozhdestvenskaya, I. I., Samovarov, M. L., et al. (2013). Massive sulfide ores of the northern equatorial Mid-Atlantic Ridge. *Oceanology* 53, 607–619. doi:10.1134/S0001437013050032

Cherkashov, G., Poroshina, I., Stepanova, T., Ivanov, V., Bel'tenev, V., Lazareva, L., et al. (2010). Seafloor massive sulfides from the northern equatorial Mid-Atlantic Ridge: new discoveries and perspectives. *Mar. Georesources Geotechnol.* 28, 222–239. doi:10.1080/1064119X.2010.483308

Conly, A. G., Scott, S. D., and Bellon, H. (2011). Metalliferous manganese oxide mineralization associated with the boléo Cu-Co-Zn district, Mexico. *Econ. Geol.* 106, 1173–1196. doi:10.2113/econgeo.106.7.1173

Dekov, V., Boycheva, T., Hålenius, U., Petersen, S., Billström, K., Stummeyer, J., et al. (2011). Atacamite and paratacamite from the ultramafic-hosted Logatchev seafloor vent field (14°45′N, Mid-Atlantic Ridge). *Chem. Geol.* 286, 169–184. doi:10.1016/j.chemgeo.2011.05.002

Delaney, J. R., Robigou, V., McDuff, R. E., and Tivey, M. K. (1992). Geology of a vigorous hydrothermal system on the Endeavour segment, Juan de Fuca Ridge. *J. Geophys. Res.* 97, 19663–19682. doi:10.1029/92jb00174
be considered extinct. Without additional constraints on the sub-surface fluid flow pathways, all deposits should be grouped in a single hydrothermal field (including the HTZ and LTZ) classified as "active."

Further exploration to the north of the Shimmering zone and east of the Alvin, Nautile, and MIR zones is needed to fully understand the extension of the TAG SMS district. New radiometric dating of sulfides, Mn oxides, and aragonite of well-localized samples is also of prime importance to better constrain the temporal evolution of the TAG hydrothermal field. Knowing the spatial and temporal distribution of active, weakly active, and inactive SMS deposits would help constrain the present and past upflow zones and hence evolution of convection cell(s) associated with the development of detachment fault systems.

## Data availability statement

The datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found in the article/Supplementary Material.

## Author contributions

E-LP: conceptualization, investigation, writing—original draft, and writing—review and editing. MP: writing—review and editing. A-SA: data curation, methodology, and writing—review and editing. AB: formal analysis, validation, and writing—review and editing. SC: formal analysis and writing—review and editing. FB: formal analysis and writing—review and editing. VA: formal analysis and writing—review and editing. CG: data curation, formal analysis, and writing—review and editing. AG: formal analysis and writing—review and editing. DP: formal analysis and writing—review and editing. MR: formal analysis and writing—review and editing. TG: writing—review and editing. LG: formal analysis and writing—review and editing. CC: writing—review and editing. M-AC: writing—review and editing. YF: supervision and writing—review and editing.

## References

Bohnenstiehl, D. R., and Kleinrock, M. C. (2000). Fissuring near the TAG active hydrothermal mound, 26°N on the Mid-Atlantic Ridge. *J. Volcanol. Geotherm. Res.* 98, 33–48. doi:10.1016/S0377-0273(99)00192-4

Bonatti, E., Kraemer, T., and Rydell, H. (1972). Classification and genesis of submarine iron-manganese deposits, in, *Ferromanganese Deposits of the Ocean Floor*. Editor D. R. Horn (Washington D.C., United States: Seabed Assessment Program, IDOE, NSF), 149–166.

Cambon, M. -A. (2014). BICOSE cruise. *RV Pourquoi pas?* doi:10.17600/14000100

Canales, J. P., Sohn, R. A., and deMartin, B. J. (2007). Crustal structure of the Trans-Atlantic Geotraverse (TAG) segment (Mid-Atlantic Ridge, 26°10′N): implications for the nature of hydrothermal circulation and detachment faulting at slow spreading ridges. *Geochem. Geophys. Geosyst.* 8, Q08004. doi:10.1029/2007GC001629

Cathles, L. M. (2011). What processes at mid-ocean ridges tell us about volcanogenic massive sulfide deposits. *Min. Deposita* 46, 639–657. doi:10.1007/s00126-010-0292-9

Chandra, A. P., and Gerson, A. R. (2010). The mechanisms of pyrite oxidation and leaching: a fundamental perspective. *Surf. Sci. Rep.* 65, 293–315. doi:10.1016/j.surfrep.2010.08.003

## Funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. The HERMINE2 expedition (2022) was carried out thanks to the France 2030 government funding for the “deep sea”—“Projet Mission DMA et CCZ”—ANR-22-MAFM-001.”

## Acknowledgments

The authors thank the crews of R/V Pourquoi pas? and Nautile HOV and all participants of the BICOSE, HERMINE, and HERMINE2 cruises for their assistance at sea. We thank reviewers J-II, JK and JJ for their thoughtful comments and suggestions, which significantly improved the quality of this paper.

## Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

## Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors, and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

## Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/feart.2024.1304993/full#supplementary-material

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Cherkashov, G., Poroshina, I., Stepanova, T., Ivanov, V., Bel'tenev, V., Lazareva, L., et al. (2010). Seafloor massive sulfides from the northern equatorial Mid-Atlantic Ridge: new discoveries and perspectives. *Mar. Georesources Geotechnol.* 28, 222–239. doi:10.1080/1064119X.2010.483308

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Dekov, V., Boycheva, T., Hålenius, U., Petersen, S., Billström, K., Stummeyer, J., et al. (2011). Atacamite and paratacamite from the ultramafic-hosted Logatchev seafloor vent field (14°45′N, Mid-Atlantic Ridge). *Chem. Geol.* 286, 169–184. doi:10.1016/j.chemgeo.2011.05.002

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Pelletier, E., and Cathalot, C. (2022). HERMINE2 cruise. *RV Pourquoi pas?* doi:10.17600/18001851

Pelletier, E., Fouquet, Y., Etoubleau, J., Cheron, S., Labanieh, S., Josso, P., et al. (2017). Ni-Cu-Co-rich hydrothermal manganese mineralization in the Wallis and Futuna back-arc environment (SW Pacific). *Ore Geol. Rev.* SI:Marine mineral deposits New Resour. base, precious, Crit. metals 87, 126–146. doi:10.1016/j.oregeorev.2016.09.014

Petersen, S., Herzig, P. M., and Hannington, M. D. (2000). Third dimension of a presently forming VMS deposit: TAG hydrothermal mound, Mid-Atlantic Ridge, 26°N. *Mineral. Deposita* 35, 233–259. doi:10.1007/s001260050018
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Petersen, S., Kuhn, K., Kuhn, T., Augustin, N., Hékinian, R., Franz, L., et al. (2009). The geological setting of the ultramafic-hosted Logatchev hydrothermal field (14°45′N, Mid-Atlantic Ridge) and its influence on massive sulfide formation. *Lithos, Recent Dev. seafloor petrology Tect.* 112, 40–56. doi:10.1016/j.lithos.2009.02.008

Purdy, G. M., Sempere, J.-C., Schouten, H., Dubois, D. L., and Goldsmith, R. (1990). Bathymetry of the mid-atlantic ridge, 24°-31°N: a map series. *Mar. Geophys. Res.* 12, 247–252. doi:10.1007/BF02428196

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Rona, P. A., Hannington, M. D., Raman, C. V., Thompson, G., Tivey, M. K., Humphris, S. E., et al. (1993b). Active and relict sea-floor hydrothermal mineralization at the TAG hydrothermal field, Mid-Atlantic Ridge. *Econ. Geol.* 88, 1989–2017. doi:10.2113/gsecongeo.88.8.1989

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Rona, P. A., McGregor, B. A., Betzer, P. R., Bolger, G. W., and Krause, D. C. (1975). Anomalous water temperatures over Mid-Atlantic Ridge crest at 26° North latitude. *Deep Sea Res. Oceanogr. Abstr.* 22, 611–618. doi:10.1016/0011-7471(75)90048-0

Rona, P. A., Petersen, S., Becker, K., Von Herzen, R. P., Hannington, M. D., Herzig, P. M., et al. (1996). Heat flow and mineralogy of TAG relict high-temperature hydrothermal zones: mid-Atlantic Ridge 26°N, 45°W. *Geophys. Res. Lett.* 23, 3507–3510. doi:10.1029/96GL03257

Rona, P. A., Thompson, G., Mottl, M. J., Karson, J. A., Jenkins, W. J., Graham, D., et al. (1984). Hydrothermal activity at the trans-atlantic geotraverse hydrothermal field, mid-Atlantic Ridge crest at 26°N. *J. Geophys. Res.* 89, 11365–11377. doi:10.1029/JB089iB13p11365

Sánchez-Mora, D., Jamieson, J., Cannat, M., Escartín, J., and Barreyre, T. (2022). Age and rate of accumulation of metal-rich hydrothermal deposits on the seafloor: the lucky strike vent field, Mid-Atlantic Ridge. *J. Geophys. Res. Solid Earth* 127, e2022JB024031. doi:10.1029/2022JB024031

Scott, R. B., Rona, P. A., McGregor, B. A., and Scott, M. R. (1974). The TAG hydrothermal field. *Nature* 251, 301–302. doi:10.1038/251301a0

Sempéré, J.-C., Purdy, G. M., and Schouten, H. (1990). Segmentation of the Mid-Atlantic Ridge between 24°N and 30°40′N. *Nature* 344, 427–431. doi:10.1038/344427a0

Smith, D. K., and Cann, J. R. (1990). Hundreds of small volcanoes on the median valley floor of the Mid-Atlantic Ridge at 24–30° N. *Nature* 348, 152–155. doi:10.1038/348152a0

Szitkar, F., Dyment, J., Petersen, S., Bialas, J., Klischies, M., Graber, S., et al. (2019). Detachment tectonics at Mid-Atlantic Ridge 26°N. *Sci. Rep.* 9, 11830–11838. doi:10.1038/s41598-019-47974-z

Thompson, G., Mottl, M. J., and Rona, P. A. (1985). Morphology, mineralogy and chemistry of hydrothermal deposits from the TAG area, 26°N Mid-Atlantic Ridge. *Chem. Geol.* 49, 243–257. doi:10.1016/0009-2541(85)90159-7

Tivey, M. A., Schouten, H., and Kleinrock, M. C. (2003). A near-bottom magnetic survey of the Mid-Atlantic Ridge axis at 26°N: implications for the tectonic evolution of the TAG segment. *J. Geophys. Res. Solid Earth* 108. doi:10.1029/2002JB001967

Tivey, M. K., Humphris, S. E., Thompson, G., Hannington, M. D., and Rona, P. A. (1995). Deducing patterns of fluid flow and mixing within the TAG active hydrothermal mound using mineralogical and geochemical data. *J. Geophys. Res.* 100, 12527–12555. doi:10.1029/95JB00610

Van Dover, C. L., Arnaud-Haond, S., Gianni, M., Helmreich, S., Huber, J. A., Jaeckel, A. L., et al. (2018). Scientific rationale and international obligations for protection of active hydrothermal vent ecosystems from deep-sea mining. *Mar. Policy* 90, 20–28. doi:10.1016/j.marpol.2018.01.020

Van Dover, C. L., Colaço, A., Collins, P. C., Croot, P., Metaxas, A., Murton, B. J., et al. (2020). Research is needed to inform environmental management of hydrothermally inactive and extinct polymetallic sulfide (PMS) deposits. *Mar. Policy* 121, 104183. doi:10.1016/j.marpol.2020.104183

White, S. N., Humphris, S. E., and Kleinrock, M. C. (1998). New observations on the distribution of past and present hydrothermal activity in the TAG area of the Mid-Atlantic Ridge (26°08′N). *Mar. Geophys. Res.* 20, 41–56. doi:10.1023/A:1004376229719

Zeng, X., Alain, K., and Shao, Z. (2021). Microorganisms from deep-sea hydrothermal vents. *Mar. Life Sci. Technol.* 3, 204–230. doi:10.1007/s42995-020-00086-4

Zhao, M., Canales, J. P., and Sohn, R. A. (2012). Three-dimensional seismic structure of a Mid-Atlantic Ridge segment characterized by active detachment faulting (Trans-Atlantic Geotraverse, 25°55′N-26°20′N). *Geochem. Geophys. Geosyst.* 13, Q0AG13. doi:10.1029/2012GC004454

Zonenshain, L. P., Kuzmin, M. I., Lisitsin, A. P., Bogdanov, Yu. A., Baranov, B. V. (1989). Tectonics of the mid-Atlantic rift valley between the TAG and MARK areas (26–24°N): evidence for vertical tectonism. *Tectonophysics* 159, 1–23. doi:10.1016/0040-1951(89)90167-4
Petersen, S., Krätschell, A., Augustin, N., Jamieson, J., Hein, J. R., and Hannington, M. D. (2016). News from the seabed – geological characteristics and resource potential of deep-sea mineral resources. *Mar. Policy* 70, 175–187. doi:10.1016/j.marpol.2016.03.012

Petersen, S., Kuhn, K., Kuhn, T., Augustin, N., Hékinian, R., Franz, L., et al. (2009). The geological setting of the ultramafic-hosted Logatchev hydrothermal field (14°45′N, Mid-Atlantic Ridge) and its influence on massive sulfide formation. *Lithos, Recent Dev. seafloor petrology Tect.* 112, 40–56. doi:10.1016/j.lithos.2009.02.008

Purdy, G. M., Sempere, J.-C., Schouten, H., Dubois, D. L., and Goldsmith, R. (1990). Bathymetry of the mid-atlantic ridge, 24°-31°N: a map series. *Mar. Geophys. Res.* 12, 247–252. doi:10.1007/BF02428196

Rona, P. A., Bogdanov, Y. A., Gurvich, E. G., Rimski-Korsakov, N. A., Sagalevitch, A. M., Hannington, M. D., et al. (1993a). Relict hydrothermal zones in the TAG hydrothermal field, mid-Atlantic Ridge 26°N, 45°W. *J. Geophys. Res.* 98, 9715–9730. doi:10.1029/93JB00552

Rona, P. A., Hannington, M. D., Raman, C. V., Thompson, G., Tivey, M. K., Humphris, S. E., et al. (1993b). Active and relict sea-floor hydrothermal mineralization at the TAG hydrothermal field, Mid-Atlantic Ridge. *Econ. Geol.* 88, 1989–2017. doi:10.2113/gsecongeo.88.8.1989

Rona, P. A., Klinkhammer, G., Nelsen, T. A., Trefry, J. H., and Elderfield, H. (1986). Black smokers, massive sulphides and vent biota at the Mid-Atlantic Ridge. *Nature* 321, 33–37. doi:10.1038/321033a0

Rona, P. A., McGregor, B. A., Betzer, P. R., Bolger, G. W., and Krause, D. C. (1975). Anomalous water temperatures over Mid-Atlantic Ridge crest at 26° North latitude. *Deep Sea Res. Oceanogr. Abstr.* 22, 611–618. doi:10.1016/0011-7471(75)90048-0

Rona, P. A., Petersen, S., Becker, K., Von Herzen, R. P., Hannington, M. D., Herzig, P. M., et al. (1996). Heat flow and mineralogy of TAG relict high-temperature hydrothermal zones: mid-Atlantic Ridge 26°N, 45°W. *Geophys. Res. Lett.* 23, 3507–3510. doi:10.1029/96GL03257

Rona, P. A., Thompson, G., Mottl, M. J., Karson, J. A., Jenkins, W. J., Graham, D., et al. (1984). Hydrothermal activity at the trans-atlantic geotraverse hydrothermal field, mid-Atlantic Ridge crest at 26°N. *J. Geophys. Res.* 89, 11365–11377. doi:10.1029/JB089iB13p11365

Sánchez-Mora, D., Jamieson, J., Cannat, M., Escartín, J., and Barreyre, T. (2022). Age and rate of accumulation of metal-rich hydrothermal deposits on the seafloor: the lucky strike vent field, Mid-Atlantic Ridge. *J. Geophys. Res. Solid Earth* 127, e2022JB024031. doi:10.1029/2022JB024031

Scott, R. B., Rona, P. A., McGregor, B. A., and Scott, M. R. (1974). The TAG hydrothermal field. *Nature* 251, 301–302. doi:10.1038/251301a0

Sempéré, J.-C., Purdy, G. M., and Schouten, H. (1990). Segmentation of the Mid-Atlantic Ridge between 24°N and 30°40′N. *Nature* 344, 427–431. doi:10.1038/344427a0

Smith, D. K., and Cann, J. R. (1990). Hundreds of small volcanoes on the median valley floor of the Mid-Atlantic Ridge at 24–30° N. *Nature* 348, 152–155. doi:10.1038/348152a0

Szitkar, F., Dyment, J., Petersen, S., Bialas, J., Klischies, M., Graber, S., et al. (2019). Detachment tectonics at Mid-Atlantic Ridge 26°N. *Sci. Rep.* 9, 11830–11838. doi:10.1038/s41598-019-47974-z

Thompson, G., Mottl, M. J., and Rona, P. A. (1985). Morphology, mineralogy and chemistry of hydrothermal deposits from the TAG area, 26°N Mid-Atlantic Ridge. *Chem. Geol.* 49, 243–257. doi:10.1016/0009-2541(85)90159-7

Tivey, M. A., Schouten, H., and Kleinrock, M. C. (2003). A near-bottom magnetic survey of the Mid-Atlantic Ridge axis at 26°N: implications for the tectonic evolution of the TAG segment. *J. Geophys. Res. Solid Earth* 108. doi:10.1029/2002JB001967

Tivey, M. K., Humphris, S. E., Thompson, G., Hannington, M. D., and Rona, P. A. (1995). Deducing patterns of fluid flow and mixing within the TAG active hydrothermal mound using mineralogical and geochemical data. *J. Geophys. Res.* 100, 12527–12555. doi:10.1029/95JB00610

Van Dover, C. L., Arnaud-Haond, S., Gianni, M., Helmreich, S., Huber, J. A., Jaeckel, A. L., et al. (2018). Scientific rationale and international obligations for protection of active hydrothermal vent ecosystems from deep-sea mining. *Mar. Policy* 90, 20–28. doi:10.1016/j.marpol.2018.01.020

Van Dover, C. L., Colaço, A., Collins, P. C., Croot, P., Metaxas, A., Murton, B. J., et al. (2020). Research is needed to inform environmental management of hydrothermally inactive and extinct polymetallic sulfide (PMS) deposits. *Mar. Policy* 121, 104183. doi:10.1016/j.marpol.2020.104183

White, S. N., Humphris, S. E., and Kleinrock, M. C. (1998). New observations on the distribution of past and present hydrothermal activity in the TAG area of the Mid-Atlantic Ridge (26°08′ N). *Mar. Geophys. Res.* 20, 41–56. doi:10.1023/A:1004376229719

Zeng, X., Alain, K., and Shao, Z. (2021). Microorganisms from deep-sea hydrothermal vents. *Mar. Life Sci. Technol.* 3, 204–230. doi:10.1007/s42995-020-00086-4

Zhao, M., Canales, J. P., and Sohn, R. A. (2012). Three-dimensional seismic structure of a Mid-Atlantic Ridge segment characterized by active detachment faulting (Trans-Atlantic Geotraverse, 25°55′N-26°20′N). *Geochem. Geophys. Geosyst.* 13, Q0AG13. doi:10.1029/2012GC004454

Zonenshain, L. P., Kuzmin, M. I., Lisitsin, A. P., Bogdanov, Yu. A., Baranov, B. V. (1989). Tectonics of the mid-Atlantic rift valley between the TAG and MARK areas (26–24°N): evidence for vertical tectonism. *Tectonophysics* 159, 1–23. doi:10.1016/0040-1951(89)90167-4