Fig 1 - uploaded by Ágata Alveirinho Dias
Content may be subject to copyright.
(A) Area between the Pico Fracture Zone (PFZ) and the Oceanographer Fracture Zone (OFZ) along the Mid-Atlantic Ridge, south of Azores Triple Junction (TPA); (B) relief map showing the location of Mount Saldanha at a non-transform offset (NTO5) between FAMOUS-S and AMAR segments, and Rainbow at a non-transform offset below Mount Saldanha (NTO6), between AMAR and AMAR-S segments. These two sites are hosted on peridotite and serpentinized peridotite massifs. The relief map was prepared by J. Luis, N. Louren ̧o and M. Miranda and the non- transform offsets (dashed lines) and individual spreading axes (black lines) are projected according to Gr `cia et al. (2000) and Parson et al. (2000), respectively.
Source publication
The Saldanha hydrothermal field is located at the top of a serpentinized massif (Mount Saldanha, MS) at a non-transform offset (NTO5) along the Mid-Atlantic Ridge (MAR), south of the Azores. It is one of the rare known sites on a worldwide basis where direct evidence of low-temperature (7–9 °C) hydrothermal activity has been provided by direct obse...
Citations
... The hydrothermal, hydrogenous, and diagenetic fields in panel (a) are after Hein et al. (1994) and references therein. The vertical dashed line in panel (b) represents the Al/(Al + Fe + Mn) ratio of 0.4 that is used to identify the hydrothermal versus detrital contribution in sediments (Dias & Barriga, 2006). In this diagram, hydrothermal chemical sediments are enriched in Fe and Mn, whereas Al and Ti feature clastic or volcanic components. ...
Modern Fe‐Si oxyhydroxide deposits occur in global marine hydrothermal vent sites. Despite their role as biogenic substrates and potential ore resources, much remains unknown about their formation processes. Here, we apply analyses of major and trace elements as well as Sr‐Nd‐Pb‐Fe isotopes combined with ²³⁸U‐²³⁰Th dating to Fe‐Si oxyhydroxides obtained from several hydrothermal fields along the Southwest Indian Ridge. These mineralized oxyhydroxides primarily consist of poorly crystalline two‐line ferrihydrite and amorphous opal‐A, with lesser amounts of nontronite and birnessite. The ubiquitous and characteristic Fe‐rich ultrastructures in the oxyhydroxides directly indicate microbial activity. The ²³⁸U‐²³⁰Th dating constrains their crystallization ages from ca. 11,873 to 384 years old. The seawater‐like ⁸⁷Sr/⁸⁶Sr and varying ¹⁴³Nd/¹⁴⁴Nd ratios underline a high proportion of seawater mixed with hydrothermal fluids. The radiogenic Pb isotopic patterns suggest a primary derivation of Pb leached from substrate basalts and to a lesser extent Pb from seawater. Stable iron isotopic compositions for different oxyhydroxides display a remarkable range between −1.47 and 0.82‰, which were interpreted as reflecting the fractionation processes during the formation of the deposits under evolving depositional redox conditions. The partial oxidation of Fe(II) and the subsurface removal of isotopically heavy Fe oxyhydroxides are suggested to play a vital role in shifting the Fe isotopic signature toward more negative values. Given that these Fe‐Si oxyhydroxide deposits exhibit features similar to certain ancient iron formations (IFs), Fe isotope systematics of these deposits may hold significant potential for fingerprinting the biological Fe oxidation processes that drove IF deposition on early Earth.
... These concentrations were significantly higher than those of the BGS, but there were large differences in element concentrations among different samples. The Co concentration was relatively high (17 to 305 µg/g, with an average value of 115 µg/g), which distinguishes those from other hydrothermal fields [6,10,27,42]. Heavy metals such as Cu, Zn, Fe, Mn, and Co in the Xunmei sediments were much higher than those in the BGS (Table 1). In addition, the average Cu/Al, Zn/Al, and Co/Al ratios in the Xunmei sediments (6734, 2837, and 47, respectively) were higher than the average values in the BGS (22, 16, and 9, respectively). ...
... Regardless of the tectonic setting, the content of Mg in hydrothermal fluids is below the detection limit, except for Karei HF (2.5 mM) [45]. The higher MgO contents in the sediments of the Dragon Horn, Saladaha, and Rainbow HFs are due to the presence of a large amount of ultramafic debris [6,24,42], but the basement rocks in the Xunmei field are N-MORB [38], and no ultramafic rocks are exposed. Therefore, the enrichment of MgO cannot originate from the input of ultrabasic rock fragments. ...
... Therefore, the enrichment of MgO cannot originate from the input of ultrabasic rock fragments. ; Duanqiao-1 [27]; Saldanha and Rainbow [42]; Serpentinite [46]; Basalt: unpublished data (Guan Y). ...
The compositions of metalliferous sediments associated with hydrothermal vents can provide key geochemical data for locating seafloor sulfides. In this study, we present the geochemistry of seabed sediments from the Xunmei hydrothermal field (HF) in the South Mid-Atlantic Ridge (SMAR). The results indicate that the sediments are mainly composed of pelagic material (biogenic calcium components), basaltic debris, iron-manganese oxides, and hydrothermal components. The sediments are significantly enriched in Cu, Zn, Fe, and Co deriving from hydrothermal fluids, as well as Mn, V, Mo, U, and P, which are primarily scavenged from seawater. The northeastern Xunmei has the highest concentrations of Cu and Zn, while the northeastern, northern, and southern regions are characterized by great inputs of Fe. Manganese and Mo are mainly enriched in the western and southern parts and show a strong positive correlation, indicating that Mo is mainly scavenged by Mn oxides. Uranium, P, and Fe exhibit strong positive correlations, suggesting that they coprecipitate with Fe from hydrothermal plumes. Vanadium and Co are introduced into sediments in different ways: V is scavenged and coprecipitated by hydrothermal plumes, and Co is derived from sulfide debris. Based on the contents of Cu and Zn and Cu/Fe (0.159), Zn/Fe (0.158), and Fe/Mn (1440) ratios, it can be inferred that a high-temperature hydrothermal vent existed in northeastern Xunmei. In combination with the distribution patterns of the above elements, the hydrothermal vents in the southern part ceased erupting after a short period of activity. In addition, the high Mn anomaly and the high U/Fe ratios at the boundaries of the investigated area indicate the presence of a relatively oxidized environment in southwestern Xunmei.
... It can further give reliable information on the hydrothermal (e.g., primary and post-depositional) processes in the active and inactive hydrothermal systems. Several notable researchers [7][8][9][10][11][12][13][14][15][16][17][18][19] have applied the geochemical and mineralogical compositions of S, Pb, and Sr isotopic compositions to hydrothermal sediment to understand hydrothermal processes, as well as geological records on the reconstruction of hydrothermal processes. These authors have used hydrothermal sediment signatures to understand past information on the intensity of hydrothermal circulations and the relative proximity of sampling stations to hydrothermal flow zones. ...
Marine sediments found in the Mid-Ocean Ridges serve as repositories for both naturally occurring (geogenic) and human-generated (anthropogenic) metals. Understanding the geochemistry and processes of these sediments is crucial for assessing their source, compositional end-members, and environmental impact. This study applied geochemical ratios and proxies to representative samples from the Carlsberg Ridge, Indian Ocean, to determine the influence of hydrothermal circulations on the near-vent hydrothermal sediments (NVS) and ridge flank sediments (RFS) and the potential effect of toxic trace metals on the benthic ecosystems. The bulk chemical compositions of seven representative hydrothermal indicator metals (Ca, Al, Ti, Fe, Mn, Cu, and Zn) and seven representative toxic trace metals (Pb, Ni, Co, Cr, As, Cd, and Co) were analyzed at the A laboratory services in Guangzhou, China, by Agilent 7700 Inductively Couple Plasma Mass Spectrometer (ICPMS). The geochemical signatures Fe/(Al + Fe + Mn) > 0.5; Al/(Al + Fe + Mn) < 0.3; (Fe + Mn)/Al > 2.5; and (Fe + Mn)/Ti > 25 affirm the proximity of the NVS and the distal position of RFS to the Wocan vent site in the Carlsberg Ridge, Indian Ocean. The pollution indices, ecological risk index, and sediment quality guidelines showed low to moderate contamination, low to moderate severity, and low to moderate ecological risk of As, Cd, Sb, Pb, Ni, Co, and Cr to the benthic ecosystems at RFS. This is an indication of low to moderate anthropogenic influence from hydrothermal venting to the ridge flank sediment (RFS). This study has shown that an understanding of background and threshold concentrations can guide the development of strategies to reduce the impact of human activities on marine ecosystems..
... Previously, numerous studies have been conducted on the mineralogy and geochemistry of metalliferous sediments, and some indicators for identifying metalliferous sediments have been proposed (e.g., Boström, 1973;Strakhov, 1976;Lisitzin et al., 1976). However, most of these studies have been performed in basalt-hosted hydrothermal systems with only a few in ultramafic-hosted settings (e.g., Cave et al., 2002;Dias and Barriga, 2006;Dias et al., 2011;Liao et al., 2019). This is not conducive to a comprehensive characterization of metalliferous sediments in both settings and to proposing appropriate prospecting indicators for SMS deposits. ...
As the most widespread hydrothermal products in the oceans, metalliferous sediments are particularly useful in prospecting for seafloor massive sulfide (SMS) deposits. A comparative study of metalliferous sediments from two types of hydrothermal fields and the background sediments along the Carlsberg Ridge has been performed to reveal their hydrothermal signatures and to determine the prospecting indicators for SMS deposits. Cu-Fe-Zn sulfides, sulfates, Fe-oxides, and Fe-oxyhydroxides are dominant in the near-vent sediments from the basalt-hosted hydrothermal fields. The near-vent sediments from the ultramafic-hosted field are abundant in detrital minerals of ultramafic source in addition to the minerals mentioned above in the basalt-hosted fields. Sulfide minerals with large grains are mainly deposited close to the vent, and as the distance from the vent increases, the grain size and abundance of the minerals rapidly decrease. Geochemically, the near-vent sediments in the basalt-hosted hydrothermal fields are abundant in Fe, Cu, Zn, Ag, Pb, Mo, Co, U, V, and P, whereas the sediments from the ultramafic-hosted system are enriched in Fe, Mn, Cu, Zn, Ag, Pb, Mo, Co, Mg, Ni, Cr, U, V, and P. The enrichment of these elements and element ratios, such as (Fe + Mn)/Al, Fe/Ti, Al/(Al + Fe + Mn), Cu/Fe, Zn/Fe, U/Fe, and V/Fe, can be indicators of the intensity of the hydrothermal inputs and the distance to the SMS deposits. Temporal and spatial variations of hydrothermally derived elements (e.g., Fe, Cu, Zn, and Pb) in sediment cores can serve as effective tools for reconstructing the hydrothermal history, evaluating the mineralization potential, and tracing inactive/buried SMS deposits. Finally, a prospecting model and method for SMS deposits is proposed based on the prospecting indicators revealed by the sediment study, combined with other prospecting indicators generally used during marine exploration. The results can provide guidance for the prospecting of hydrothermal fields and SMS deposits.
... Owing to the very low concentration of inorganic carbon in serpentinization fluids, the most feasible origin for this 13 C depletion is the oxidation of methane [105]. The rare rock fragments characterized by altered ultramafic lithoclasts (serpentinites) and claystone are in part similar to those described in Saldanha sediments, a hydrothermal site of the MAR partly supported by serpentinization processes [106]. ...
Recent studies in the ocean depths have discovered a large number of organisms and microorganisms that live in extreme environments of hydrothermal vents and cold seeps obtaining their energy through anaerobic oxidation of methane (AOM) process through a microbial consortium capable of reducing sulfate and oxidizing methane simultaneously. On the surface, the fossil record of this type of chemosynthetic community has made it possible to establish the link between the tectonic plate dynamics with the origin of mineral deposits or sediments formed on the oceanic ridges and attached to the continents. The foregoing could be supported by the 13C and 18C stable isotopes analysis that has been carried out in the fossil record of rocks and sediments attached to the continents and the study of stable isotopes that is currently carried out in submersibles at mid-ocean ridges around the world. The relationship between current values and the fossil record is key to understanding, among others, the methane contribution to the environment and its variation throughout time. Cerro Matoso is a recent case that permitted linked the recent hydrothermal activity in the mid-ocean ridge, with those of the ancient ones.
... Hydrothermal activities have been documented worldwide throughout the Pacific, North Atlantic and Indian oceans Dias and Barriga, 2006;Fouquet et al., 1998;Kelley et al., 2001) since first observation of hydrothermal vents and associated massive sulfides in 1977 (Corliss et al., 1979). However, the majority of southern Mid-Atlantic Ridge (SMAR) remains unexplored. ...
... These concentrations were significantly higher than those of the BGS, but there were large differences in element concentrations among different samples. The Co concentration was relatively high (16.63 to 304.6 ppm, with an average of 114.9 ppm), which distinguishes it from other hydrothermal sediments in the field [8,12,29,43]. Heavy metals such as Cu, Zn, Fe, Mn, and Co in the Xunmei sediments were much higher than those in the BGS (Table 1). In addition, the average Cu/Al, Zn/Al, and Co/Al ratios in the Xunmei sediments (6734, 2837, and 47.09, respectively) were higher than the average values in the BGS (21.88, 15.96, and 8.98, respectively). ...
... Regardless of the tectonic background, the content of Mg in hydrothermal fluids is less than 1 ppm [46]. The higher MgO contents in the sediments of the Dragon Horn, Saladaha, and Rainbow HFs is due to the presence of a large amount of ultramafic debris [8,26,43], but the basement rocks in the Xunmei field are N-MORB [40], and no ultramafic rocks are exposed. Therefore, the enrichment of MgO cannot originate from the input of ultrabasic rock fragments. ...
... (4) The F4 factor is closely related to Zn and Cu and is primarily associated with sulfides, representing the contribution of sulfide chimney fragments. Data sources: Endeavour: [12]; Dragon Horn: [8]; DHF: [29]; Saladaha and Rainbow: [43]; Serpentinite: [47]; Basalt: unpublished data. ...
The compositions of metalliferous sediments which is associated with hydrothermal vents can provide reliable geochemical indicators for the exploration of seafloor sulfides. In this study, surface sediments from the Xunmei hydrothermal field (HF) on the South Mid-Atlantic Ridge (SMAR) were selected, and their major and trace elements were analysed. The results showed that the sediments are composed of pelagic material (calcium biogenic components), basaltic debris, iron-manganese oxides, and a mixture of hydrothermal components. Additionally, the sediments were found to be significantly enriched in Cu, Zn, Fe and Co derived from hydrothermal sources, as well as Mn, V, Mo, U and P, which are primarily scavenged from seawater. The Cu and Zn concentrations are highest in the northeastern part of Xunmei, while the northeastern, northern, and southern parts are characterized by great inputs of hydrothermal Fe. Manganese and Mo are mainly enriched in the western and southern parts and show a strong positive correlation, indicating that Mo is mainly scavenged by Mn oxides. There are high positive correlations among U, P, and Fe, indicating their coprecipitation with Fe from hydrothermal plumes. Vanadium and Co are introduced into sediments in two ways, i.e., V is scavenged and coprecipitates from hydrothermal plumes, and Co is derived from sulfide debris. Based on the variations in Cu and Zn contents and in the Cu/Fe (0.159), Zn/Fe (0.158), and Fe/Mn (1440) ratios, it can be inferred that a high-temperature hydrothermal vent existed in northeastern Xunmei. In combination with the distribution patterns of the above elements, the hydrothermal vents in the southern part ceased erupting after a short period of activity. In addition, the high Mn anomaly and the high U/Fe ratios at the boundaries of the investigated area indicate the presence of a relatively oxidized environment in southwestern Xunmei.
... The isotopic composition of sediments discloses the nature of hydrothermal vent systems, including chemical composition, source and temperature of the fluids, source of the heat, seawater/fluid interactions, and organic matter composition and origin (Cave et al., 2002;Dias and Barriga 2006;Dekov et al., 2008;Eickmann et al., 2014;Liao et al., 2018Liao et al., , 2019Lim et al., 2022). Our research provides the first insights into the isotopic composition of sediments from the PB, PTF, and AR vent systems. ...
The functional diversity of fungi remains poorly explored in the deep-sea, particularly in hydrothermal vents. Here, we approached this gap through the analysis of stable isotopes of carbon (δ¹³C), nitrogen (δ¹⁵N), and sulfur (δ³⁴S) of fourteen isolates obtained from three deep-sea vent systems of the southern Gulf of California. The δ¹³C results indicated that 60% of the isolates relied on mixed carbon sources fixed by the Calvin-Benson-Bassham and the reductive Tricarboxylic Acid (rTCA) cycles, whereas 40% relied exclusively on rTCA carbon. The δ¹⁵N and δ³⁴S values suggested a dependence on local and external nitrogen sources and the assimilation of chemosynthetic and photosynthetic inputs. Fungal δ¹³C and δ¹⁵N overlapped with those of primary and secondary vent macroconsumers, implying the assimilation of bacterial and invertebrate necromass and their ecological role as parasites. These findings provide insights into the unexplored trophic versatility of fungi in chemosynthetic ecosystems, highlighting their importance in deep-sea trophic dynamics.
... Metalliferous sediments, developed in the modern hydrothermal activity zones of mid-oceanic ridges, are described in numerous works of researchers in Russia and abroad (Dias and Barriga, 2006;Feely et al., 1992;German et al., 1993;Gidrotermal'nye …, 1992;Gordeev et al., 1993;Gurvich, 1998Gurvich, , 2006Lisitsyn, 1978;Lisitsyn et al., 1990;Metallonosnye osadki …, 1976;Metz et al., 1988;Mills and Elderfield, 1993;Mottl and McConachy, 1990;Rudnitsky and Elderfield, 1993;Rusakov, 2007Rusakov, , 2009and others). These works are focused on sediments formed during the precipitation of ore components from the plume or during the destruction of hydrothermal sulfide edifices. ...
... Various structural-morphological types of iron hydroxides could be formed under different conditions: 1) in the plume under the influence of oxygencontaining seawater (Dias, 2006;Feely et al., 1992;Gordeev et al, 1993;Gurvich, 1998Gurvich, , 2006Krasnov et al., 1992;Rusakov, 2007Rusakov, , 2009Sudarikov et al., 2014;and others); 2) in the sediment due to halmyrolysis (Hannington et al., 1988;Maslennikov et al., 2023); and 3) under the influence of fluids percolating in sediments suggested by the formation of brown spots and ferruginous crusts on the sediment surface (Gablina, 2022;Gablina et al., 2017). Discrepancy in the composition of these morphological types and their formation condition is the subject of further research. ...
The work is devoted to the study of ore minerals from the surface horizon of ore-bearing sediments in the Pobeda hydrothermal cluster using the following methods: optical microscopy, scanning electron microscopy, and X-ray spectral microanalysis. It was found that ore minerals are represented by fragments of Cu-Fe sulfides (isocubanite, chalcopyrite, and pyrite), newly formed iron hydroxides, and atacamite. In addition, barite and edaphogenic material as talcified silicate clasts, sometimes with sulfide inclusions, are present. Structural-morphological types of iron hydroxides are distinguished. Based on the hydrophysical data, the location of assumed active hydrothermal vent in the Pobeda-3 ore occurrence area was updated. Distribution of the studied minerals depending on the location relative to active hydrothermal vents is described. Decrease in the size and amount of hydrothermal mineral clasts and edaphogenic material, as well as increase in the degree of sulfide replacement by iron hydroxides, were observed when moving away from the sources. Moreover, decrease in the Cu/Fe ratio in the chemical composition of Cu-Fe sulfides is also noted. An unidentified phase of Cu 3.57-4.22 Fe 1.71-2.19 S 4.99-5.31 with the chalcopyrite lamellas was established in the surface horizon of the column at station 37L245g.
... Metalliferous sediments, developed in the modern hydrothermal activity zones of mid-oceanic ridges, are described in numerous works of researchers in Russia and abroad (Dias and Barriga, 2006;Feely et al., 1992;German et al., 1993;Gidrotermal'nye …, 1992;Gordeev et al., 1993;Gurvich, 1998Gurvich, , 2006Lisitsyn, 1978;Lisitsyn et al., 1990;Metallonosnye osadki …, 1976;Metz et al., 1988;Mills and Elderfield, 1993;Mottl and McConachy, 1990;Rudnitsky and Elderfield, 1993;Rusakov, 2007Rusakov, , 2009and others). These works are focused on sediments formed during the precipitation of ore components from the plume or during the destruction of hydrothermal sulfide edifices. ...
... Various structural-morphological types of iron hydroxides could be formed under different conditions: 1) in the plume under the influence of oxygencontaining seawater (Dias, 2006;Feely et al., 1992;Gordeev et al, 1993;Gurvich, 1998Gurvich, , 2006Krasnov et al., 1992;Rusakov, 2007Rusakov, , 2009Sudarikov et al., 2014;and others); 2) in the sediment due to halmyrolysis (Hannington et al., 1988;Maslennikov et al., 2023); and 3) under the influence of fluids percolating in sediments suggested by the formation of brown spots and ferruginous crusts on the sediment surface (Gablina, 2022;Gablina et al., 2017). Discrepancy in the composition of these morphological types and their formation condition is the subject of further research. ...
The work is devoted to the study of ore minerals of the surface horizon of ore-bearing sediments of the Pobeda hydrothermal cluster. The following methods were used: optical microscopy, scanning electron microscopy, and X-ray spectral microanalysis. It was found that ore minerals are represented by fragments of copper and iron sulfides (isocubanite, chalcopyrite, and pyrite), newly formed iron hydroxides, and atacamite. In addition, barite and edaphogenic material in the form of silicate clasts, sometimes with sulfide inclusions, are present. Structural and morphological types of iron hydroxides are distinguished. On the basis of hydrophysical data, the location of the assumed active hydrothermal source in the area of the Pobeda-3 ore occurrence was updated. The distribution of studied minerals depending on the location relative to active hydrothermal vents is described. A decrease in the size and amount of hydrothermal mineral clasts and edaphogenic material and an increase in the degree of sulfide replacement by iron hydroxides were observed at a distance from the sources. Also, a decrease in the Cu/Fe ratio in the chemical composition of copper and iron sulfides is observed when moving away from the source. An unidentified phase of Cu3.57‒4.22Fe1.71‒2.19S4.99‒5.31 with lamellae of chalcopyrite inclusions was established in the surface horizon of the column at 37L245g.
