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![Conceptual diagrams of hydrothermal scale formation within the vent pipe. a When the pipe is clogged by scale, isolation from the ambient seawater and subseafloor boiling, confirmed by fluid inclusion analyses, produces hydrothermal fluid with low sulfur fugacity (fS2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {f}_{S_2} $$\end{document}) that results in sphalerite with a high Fe content and the precipitation of the reddish-brown component rich in galena and chalcopyrite. b After scale removal, the flow of hydrothermal fluid from the pipe becomes more vigorous and promotes local entrainment of seawater beneath the seafloor, resulting in hydrothermal fluid with high fS2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {f}_{S_2} $$\end{document}, sphalerite with a low Fe content, and precipitation of dark, coarse-grained sphalerite. Ccp, chalcopyrite; Gn, galena; Sp, sphalerite](publication/345906219/figure/fig4/AS:963551422328872@1606739969889/Conceptual-diagrams-of-hydrothermal-scale-formation-within-the-vent-pipe-a-When-the-pipe.png)
Conceptual diagrams of hydrothermal scale formation within the vent pipe. a When the pipe is clogged by scale, isolation from the ambient seawater and subseafloor boiling, confirmed by fluid inclusion analyses, produces hydrothermal fluid with low sulfur fugacity (fS2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {f}_{S_2} $$\end{document}) that results in sphalerite with a high Fe content and the precipitation of the reddish-brown component rich in galena and chalcopyrite. b After scale removal, the flow of hydrothermal fluid from the pipe becomes more vigorous and promotes local entrainment of seawater beneath the seafloor, resulting in hydrothermal fluid with high fS2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {f}_{S_2} $$\end{document}, sphalerite with a low Fe content, and precipitation of dark, coarse-grained sphalerite. Ccp, chalcopyrite; Gn, galena; Sp, sphalerite
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Artificial hydrothermal vents, created by boreholes that discharge hydrothermal fluids and useful for observing secular changes in mineral precipitates and the chemical compositions of hydrothermal fluids, are periodically cleaned of scale deposits. Here, we report petrographic and geochemical features of hydrothermal scale with a concentric struct...
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... A geochemical reactor, called the Kuroko-ore (also called black ore, containing hydrothermal sulfide minerals enriched in sphalerite and galena) cultivation apparatus, was installed on the artificial hydrothermal vent at Hole C9017A during the cruise CK16-05. It consisted of an inflow pipe, a cultivation cell, four outlet pipes, and two P/T sensors (Fig. 1A), as previously reported (Nozaki et al., 2021;Kinoshita et al., 2022). Two P/T sensors with short and long probes were inserted into the inflow pipe (basal part of the cell) and the cultivation cell near its top, respectively. ...
Microbiologically influenced corrosion refers to the corrosion of metal materials caused or promoted by microorganisms. Although some novel iron-corrosive microorganisms have been discovered in various manmade and natural freshwater and seawater environments, microbiologically influenced corrosion in the deep sea has not been investigated in detail. In the present study, we collected slime-like precipitates composed of corrosion products and microbial communities from a geochemical reactor set on an artificial hydrothermal vent for 14.5 months, and conducted culture-dependent and -independent microbial community analyses with corrosive activity measurements. After enrichment cultivation at 37, 50, and 70°C with zero-valent iron particles, some of the microbial consortia showed accelerated iron dissolution, which was approximately 10- to 50-fold higher than that of the abiotic control. In a comparative analysis based on the corrosion acceleration ratio and amplicon sequencing of the 16S rRNA gene, three types of corrosion were estimated: the methanogen-induced type, methanogen–sulfate-reducing bacteria cooperative type, and sulfate-reducing Firmicutes-induced type. The methanogen-induced and methanogen–sulfate-reducing bacteria cooperative types were observed at 50°C, while the sulfate-reducing Firmicutes-induced type was noted at 37°C. The present results suggest the microbial components associated with microbiologically influenced corrosion in deep-sea hydrothermal systems, providing important insights for the development of future deep-sea resources with metal infrastructures.
... The surface structure, texture, and precipitated minerals on the adsorption sheets were observed by field emission-scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS) 30 . The element concentrations on the adsorption sheets and in the precipitate were determined by inductively coupled plasma-mass spectrometry (ICP-MS) with the mixed acid digestion method 31,32 (Supplementary Table S1). The chemical composition of the hot spring water source at Obuki was determined by ion chromatography (IC) and ICP-atomic emission spectrometry (ICP-AES) 33 (Supplementary Table S2), and the chemical composition of the hot spring water in the test water tank was determined by ICP-MS at Japan Agency for Marine-Earth Science and Technology (JAM-STEC) 34 (Supplementary Table S3) and by ICP-MS and high-resolution (HR)-ICP-MS at Activation Laboratories Ltd., a commercial analytical service (Supplementary Table S4). ...
... The residue was dissolved in 5 mL of Milli-Q deionised water combined with 4 mL HNO 3 and 1 mL HCl, and then further diluted to 1:100 or 1:20 by mass (total dilution factor ~ 20,000 or ~ 200) before introduction into the ICP-MS system. Details of these analytical procedures, including instrumental drift and mass interference correction methods, are reported in Takaya et al. 31 and Nozaki et al. 32 ...
Gold (Au), as one of the most precious metal resources that is used for both industrial products and private ornaments, is a global investment target, and mining companies are making huge investments to discover new Au deposits. Here, we report in situ Au adsorption in an acidic hot spring by a unique adsorption sheet made from blue-green algae with a high preferential adsorption ability for Au. The results of in situ Au adsorption experiments conducted for various reaction times ranging from 0.2 h to 7 months showed that a maximum Au concentration of 30 ppm was adsorbed onto the blue-green algal sheet after a reaction time of 7 months. The Au concentration in the hot spring water was below the detection limit (< 1 ppt); therefore, Au was enriched by preferential adsorption onto the blue-green algal sheet by a factor of more than ~ 3 × 10⁷. Thus, our gold recovery method has a high potential to recover Au even from an Au-poor solution such as hot spring water or mine wastewater with a low impact on the environment.
... Among these, seafloor massive sulfide deposits, which are composed of sulfide chimneys and mounds, form in close proximity to submarine hydrothermal vents. Since these deposits are rich in various base, precious, and critical metals [1], [2], [7], [8], [9], they have attracted attention as potential sources of minerals that are essential for sustainable society in the future [2], [10], [11]. Moreover, seafloor massive sulfide deposits also attract attention as an analogue of metal deposits on land that formed over a geological time scale of hundreds of millions of years [7]. ...
Seafloor massive sulfide deposits have attracted attention as a mineral resource, as they contain a wide variety of base, precious, and other valuable critical metals. Previous studies have shown that signatures of hydrothermal activity can be detected by a multibeam echo sounder (MBES), which would be beneficial for exploring sulfide deposits. Although detecting such signatures from acoustic images is currently performed by skilled humans, automating this process could lead to improved efficiency and cost effectiveness of exploration for the seafloor deposits. Herein, we attempted to establish a method for automated detection of MBES water column anomalies using deep learning models. First, we compared the “Mask R-CNN” and “YOLO-v5” detection model architectures, wherein YOLO-v5 yielded higher F1 scores. We then compared the number of training classes and found that models trained with two classes (signal and noise) exhibited superior performance compared with models trained with only one class (signal). Finally, we examined the number of trainable parameters and obtained the best model performance when the YOLO-v5l model with a large trainable parameters was used in the two-class training process. The best model had a precision of 0.928, a recall of 0.881, and an F1 score of 0.904. Moreover, this model achieved a low false alarm rate (less than 0.7%) and had a high detection speed (20−25 ms per frame), indicating that it can be applied in the field for automatic and real-time exploration of seafloor hydrothermal deposits.
... MΩ cm) combined with 4 mL HNO3 and 1 mL HCl, then diluted to 1:100 by mass (total dilution factor ~20,000) before being introduced into the ICP-QMS instrument. Details of these analytical procedures, including instrumental drift and mass interference correction methods, are reported in Takaya et al. (2018) and Nozaki et al. (2021b). ...
Better understanding metallogenesis in oceanic crust depends on costly sea-floor drilling projects in areas where metal-bearing deposits, such as sea-floor massive sulfide deposits, are currently forming. In 2018, International Ocean Discovery Program (IODP) Expedition 376 recovered drill cores from an active hydrothermal field at Brothers volcano, in the Kermadec arc. These provide insight into the formation of mineral deposits along arcs, the structure and permeability of hydrothermal sites, and the relationship between the discharge of magmatic fluids and the deep biosphere. We report whole-rock major and trace element compositions and the Re-Os isotope geochemistry of hydrothermally altered volcanic rocks in a core from Hole U1530A, extending 453 m beneath the sea floor, and unaltered volcanic rocks in cores from four other drilling sites, and interpret these data to better understand subseafloor mixing of hydrothermal fluids and ambient seawater. The core exhibits more radiogenic 187Os/188Os values than typical basal values in four intervals. We propose two causal mechanisms of these radiogenic values: (1) mixing between seawater and hydrothermal fluid, associated with abundant deposition of sulfide or sulfate minerals; and (2) ingress of seawater with radiogenic 187Os/188Os values, associated with abundant chlorite and high porosity. Extreme Os enrichments up to 61.5 ppb are interpreted as the result of mobilization of Os as OsO4 or OsF6 and transport by volcanic gas, which also affected the Re-Os geochemistry of the rocks from the other Expedition 376 holes. Mobilization and transport of Os by volcanic gas may be an appreciable factor in the influx of unradiogenic Os into the ocean.
... Major elements (Na, Mg, Al, P, K, Ca, Ti, Mn, and Fe) were analyzed together with the trace elements. Details of these analytical procedures are reported in Takaya et al. (2018) and Nozaki et al. (2021). ...
Despite the widespread use of Re–Os isotopes in various geoscience fields, relatively little is known about the behavior of Re and Os during fluid-mediated hydrothermal alteration of igneous rocks in the (sub)seafloor, especially in an intraoceanic arc setting. Here, we provide a depth profile of Re–Os geochemistry at Site U1527, located on the NW caldera rim of the Brothers volcano hydrothermal field in the Kermadec arc and drilled during International Ocean Discovery Program (IODP) Expedition 376 in 2018. Volcaniclastic rocks from Hole U1527C that had experienced various degrees of high- and low-temperature hydrothermal alteration were analyzed for bulk chemical composition and Re–Os isotopes. The concentration of Re varied from 0.172 to 18.7 ppb, and that of Os from 9.7 to 147.1 ppt. Hydrothermal alteration usually resulted in Re uptake by rocks, but a part of Re was released into the ocean by later oxidative weathering. Compared with Re, Os mobility resulting from hydrothermal alteration was limited. The relatively homogenous ¹⁸⁷Os/¹⁸⁸Os values (0.13–0.14) of the original volcaniclastic rocks were altered, becoming slightly more radiogenic (up to 0.212), by the addition of seawater-derived radiogenic Os by (1) Os precipitation induced by seawater–hydrothermal fluid mixing, which was accompanied by enrichment with Ba (barite precipitation) as well as by the highest Re and Os concentrations in the profile, and (2) adsorption of seawater-derived radiogenic Os onto Fe hydroxide without any corresponding enrichment of Ba, Re, or Os. Compared with high temperature-altered zones of mid-ocean ridge basalt, the altered samples in this study showed intense Re enrichment, presumably reflecting abundant pyrite precipitation in a Re-rich magmatic–hydrothermal environment unique to the arc setting. The results at Hole U1527 may suggest that subseafloor high-temperature alteration can be a sink for Re degassed from magma. The altered rock may also be a source of Re in the ocean as a result of subsequent low-temperature alteration.
p>Seafloor massive sulfide deposits have attracted attention as a mineral resource, as they contain a wide variety of base, precious, and other valuable critical metals. Previous studies have shown that signatures of hydrothermal activity can be detected by a multi-beam echo sounder (MBES), which would be beneficial for exploring sulfide deposits. Although detecting such signatures from acoustic images is currently performed by skilled humans, automating this process could lead to improved efficiency and cost effectiveness of exploration for seafloor deposits. Herein, we attempted to establish a method for automated detection of MBES water column anomalies using deep learning models. First, we compared the “Mask R-CNN” and “YOLO-v5” detection model architectures, wherein YOLO-v5 yielded higher F1 scores. We then compared the number of training classes and found that models trained with two classes (signal and noise) exhibited superior performance compared with models trained with only one class (signal). Finally, we examined the number of trainable parameters and obtained the best model performance when the YOLO-v5l model with a large number of trainable parameters was used in the two-class training process. The best model had a precision of 0.928, a recall of 0.881, and an F1 score of 0.904. Using this method, the detection speed was 20−25 ms per frame, which is faster than the pace at which MBES images can generally be generated. Therefore, our best model can be applied in the field for automatic and real-time exploration of seafloor hydrothermal deposits.
This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessible.
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p>Seafloor massive sulfide deposits have attracted attention as a mineral resource, as they contain a wide variety of base, precious, and other valuable critical metals. Previous studies have shown that signatures of hydrothermal activity can be detected by a multi-beam echo sounder (MBES), which would be beneficial for exploring sulfide deposits. Although detecting such signatures from acoustic images is currently performed by skilled humans, automating this process could lead to improved efficiency and cost effectiveness of exploration for seafloor deposits. Herein, we attempted to establish a method for automated detection of MBES water column anomalies using deep learning models. First, we compared the “Mask R-CNN” and “YOLO-v5” detection model architectures, wherein YOLO-v5 yielded higher F1 scores. We then compared the number of training classes and found that models trained with two classes (signal and noise) exhibited superior performance compared with models trained with only one class (signal). Finally, we examined the number of trainable parameters and obtained the best model performance when the YOLO-v5l model with a large number of trainable parameters was used in the two-class training process. The best model had a precision of 0.928, a recall of 0.881, and an F1 score of 0.904. Using this method, the detection speed was 20−25 ms per frame, which is faster than the pace at which MBES images can generally be generated. Therefore, our best model can be applied in the field for automatic and real-time exploration of seafloor hydrothermal deposits.
This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessible.
</p
We observed temperature variations over 10 months within a Kuroko ore (hydrothermal sulfide) cultivation apparatus installed atop a 50‐m‐deep borehole drilled in the Noho hydrothermal system in the mid‐Okinawa Trough, southwestern Japan, for monitoring of hydrothermal fluids and in situ mineral precipitation experiments. Temperature and pressure in the apparatus fluctuated with the tidal period immediately after its installation. Initially, the average temperature was 75–76°C and the amplitude of the semidiurnal tidal temperature modulation was ∼0.3°C. Four months later, the amplitude of tidal temperature modulation had gradually increased to 4°C in synchrony with an average temperature decrease to ∼40°C. Numerical modeling showed that both the increase in tidal amplitude and the decrease in average temperature were attributable to a gradual decrease in inflow to the apparatus, which promoted conductive cooling through the pipe wall. The reduced inflow was probably caused by clogging inside the apparatus, but we cannot rule out a natural cause, because the drilling would have significantly decreased the volume of hot fluid in the reservoir. The temperature fluctuation phase lagged the pressure fluctuation phase by ∼150°. Assuming that the fluctuations originated from inflow from the reservoir, we conducted 2D numerical hydrothermal modeling for a poroelastic medium. To generate the 150° phase lag, the permeability in the reservoir needed to exceed that in the ambient formation by ∼three orders of magnitude. The tidal variation phase can be a useful tool for assessing the hydrological state and response of a hydrothermal system.
