Source origin and ore-controlling factors of hydrothermal sulfides from the Tianzuo hydrothermal field, Southwest Indian Ridge

Cao, Hong; Sun, Zhilei; Jiang, Zike; Dong, Aiguo; Wang, Geng; Zhang, Xilin; Li, Xin; Yan, Dan; Liu, Weiliang

doi:10.1016/j.oregeorev.2021.104168

Cited by 11 publications

(2 citation statements)

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“…This reflects the fact that high-temperature sulfides are much more abundant than low-temperature sulfides within the massive sulfide samples, and the influence of low-temperature sulfides for the δ 34 S values of CRS in these samples was therefore limited. This inference is consistent with the whole-rock data, which show that the bulk sulfide samples have δ 34 S values of 11.50‰-13.30‰ (Cao et al, 2021), as well as the mineralogical observations, which showed that the lowtemperature pyrite with negative δ 34 S values was minor and only occurred around early high-temperature sulfides (Ding et al, 2021(Ding et al, , 2022. These data indicate that the sulfur associated with the hightemperature sulfides within the THF was derived from the thermochemical reduction of pre-precipitated sulfate within deep reaction zones during the emplacement of gabbroic intrusions (Figure 7b).…”

Section: Sources Of Heavy Sulfur Within the Thfsupporting

confidence: 90%

“…Previous studies have identified high‐ and low‐temperature sulfide mineralization within the THF (Cao et al, 2018, 2021; Ding et al, 2021, 2022), both of which are characterized by extremely positive and negative δ 34 S values, respectively (Ding et al, 2021). However, the CRS in the massive sulfide samples from the THF has δ 34 S values of 10.90‰–10.98‰, which are inconsistent with the CRS compositions of peridotite in the study area (10.22‰; Figure 5).…”

Section: Discussionmentioning

confidence: 99%

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Sulfur sources for ultramafic‐hosted sulfide mineralization in the Tianzuo hydrothermal field, 63.5° E, South‐west Indian Ridge: Insights from sulfur and carbon isotopes

et al. 2022

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To date, discovered ultramafic-hosted seafloor massive sulfide (UM-SMS) deposits are rare, remain poorly understood in terms of their genesis, and typically form along slow-and ultraslow-spreading mid-oceanic ridges. The Tianzuo hydrothermal field (THF) is the only UM-SMS deposit identified so far along the ultraslow-spreading South-west Indian Ridge (SWIR). This study presents new detailed mineralogical and S-C isotopic data for serpentinized peridotite, gabbro, serpentinite, and sulfide ore samples from the THF and to provide new insights into the processes that formed the deposit. Chromium-reduced sulfur (CRS) and sulfate-sulfur (SS) in samples of serpentinized peridotite have positive δ 34 S values (up to 10.22‰ and 20.67‰, respectively). The CRS formed through thermochemical reduction of seawater sulfate during reactions between seawater and ultramafic rocks, whereas the SS most likely occurred as dissolved sulfate phases in seawater occupying the pore space of serpentinized peridotite after exposure at the seafloor. The serpentinite samples contain SS with δ 34 S values of 19.21‰-20.9‰, indicating infiltration by seawater that led to the deposition of seawater sulfate. The sulfide ores have acid-volatile sulfur (AVS), CRS, and SS δ 34 S values of 10.99‰-12.07‰, 2.34‰-10.98‰, and À4.13‰ to 2.76‰, respectively, indicating that the AVS and CRS within the samples are dominated by sulfur reduced from seawater sulfate (e.g., anhydrite) and leached from the surrounding wall rocks, although the re-oxidization of microbial-reduced sulfur most likely generated the sulfate with low and negative δ 34 S values. The total carbon and total organic carbon δ 13 C values of the THF samples are negative and range from À21.99‰ to À0.34‰ and À26.7‰ to À21.02‰, respectively, further suggesting that the samples record microbial activity. Gabbro samples have strongly negative AVS (À10.69‰) and CRS (À7.2‰) δ 34 S values, indicating that microbial-reduced sulfur derived from shallow levels in the crust was incorporated into the hydrothermal system that circulated through the deeper-seated gabbroic units. Our results suggest

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Section: Sources Of Heavy Sulfur Within the Thfsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Sulfur sources for ultramafic‐hosted sulfide mineralization in the Tianzuo hydrothermal field, 63.5° E, South‐west Indian Ridge: Insights from sulfur and carbon isotopes

et al. 2022

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Biogeochemical Characteristics of Hydrothermal Systems in the Indian Ocean

Prakash

Fernandes

Ingole

et al. 2022

Systems Biogeochemistry of Major Marine Biomes

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Mineralogy and trace element geochemistry of hydrothermal sulfides from the Ari vent field, Central Indian Ridge

et al. 2023

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The Ari vent field (AVF) is an ultramafic-hosted seafloor massive sulfide (SMS) deposit in the middle part of the Central Indian Ridge. In this paper, we describe the detailed mineralogy and geochemistry of hydrothermal sulfide samples from the AVF, which can be classified into Fe–Cu- and Cu-rich types based on the major sulfide minerals. Sulfide mineralisation of the former type comprises: (1) stage I, early deposition of magnetite, pyrrhotite, isocubanite, chalcopyrite, and subhedral–euhedral pyrite under high-temperature fluid conditions (> 335 °C); (2) stage II, deposition of colloform pyrite, sphalerite, galena, and electrum from low-temperature fluids (< 200 °C) during the later mineralisation stage; and (3) stage III, seawater alteration that caused the precipitation of uraninite and chalcocite. This indicates that the fluids in the AVF had decreasing temperature and ƒS2 and increasing ƒO2 as mineralisation proceeded. The Cu-rich sulfide samples have mineral assemblages and a paragenesis similar to those of the Fe–Cu-rich sulfide samples, but the higher proportion of isocubanite is indicative of relatively high-temperatures and reducing conditions during mineralisation. Bulk chemical compositions of the AVF sulfides are characterised by high U contents (up to 51.9 ppm) and a distinct Sn distribution (2.1–86.4 ppm) between the two different types of hydrothermal samples, which differ from those of other ultramafic-hosted sulfide deposits. The U content is controlled mainly by the precipitation of discrete uraninite grains (< 1 μm in size) on altered surfaces of pyrite and hematite. The oxidative alteration of Fe-bearing minerals caused the fixation of seawater-derived U. Laser ablation–inductively coupled plasma–mass spectrometry analysis showed that most trace elements occur in solid solution in the sulfide minerals, mainly controlled by the physicochemical conditions of the hydrothermal fluids (e.g. temperature, ƒS2, and ƒO2). In particular, a comparative analysis of other mid-ocean ridge systems shows that the ultramafic-hosted sphalerite and pyrite are more enriched in Sn as compared with those hosted by basaltic rocks. However, the Fe–Cu-rich sulfide samples of the AVF are Sn-poor (< 10.2 ppm), because pyrite is substantially depleted in Sn (mostly < 1 ppm) as compared with sphalerite, regardless of the effect of the ultramafic-hosted mineralisation. This indicates that in situ trace element analysis of sphalerite and pyrite, especially for Sn, can provide insights into the different hydrothermal mineralisation in basaltic- and ultramafic-hosted systems, which cannot necessarily be inferred from bulk analysis. Our comparison also suggests that the Sn contents of ultramafic-hosted SMS deposits would be a possible source of Sn for the ultramafic-hosted volcanogenic massive sulfide (UM-VMS) deposit. The δ34S values (+ 6.2 to + 8.5‰) of the pyrite record thermochemical sulfate reduction of seawater, which suggests that sulfur and most metals were predominantly leached from the associated host rocks with a contribution (29–40%) from reduced seawater sulfur. In conclusion, the AVF is a rock-dominated system that contains ultramafic-hosted mineralisation in the Central Indian Ridge.

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Source origin and ore-controlling factors of hydrothermal sulfides from the Tianzuo hydrothermal field, Southwest Indian Ridge

Cited by 11 publications

References 118 publications

Sulfur sources for ultramafic‐hosted sulfide mineralization in the Tianzuo hydrothermal field, 63.5° E, South‐west Indian Ridge: Insights from sulfur and carbon isotopes

Sulfur sources for ultramafic‐hosted sulfide mineralization in the Tianzuo hydrothermal field, 63.5° E, South‐west Indian Ridge: Insights from sulfur and carbon isotopes

Biogeochemical Characteristics of Hydrothermal Systems in the Indian Ocean

Mineralogy and trace element geochemistry of hydrothermal sulfides from the Ari vent field, Central Indian Ridge

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