Pyrite Varieties at Pobeda Hydrothermal Fields, Mid-Atlantic Ridge 17°07′–17°08′ N: LA-ICP-MS Data Deciphering

The massive sulfide ores of the Pobeda hydrothermal fields are grouped into five main mineral microfacies: (1) isocubanite-pyrite, (2) pyrite-wurtzite-isocubanite, (3) pyrite with minor isocubanite and wurtzite-sphalerite microinclusions, (4) pyrite-rich with framboidal pyrite, and (5) marcasite-pyrite. This sequence reflects the transition from feeder zone facies to seafloor diffuser facies. Spongy, framboidal, and fine-grained pyrite varieties replaced pyrrhotite, greigite, and mackinawite “precursors”. The later coarse and fine banding oscillatory-zoned pyrite and marcasite crystals are overgrown or replaced by unzoned subhedral and euhedral pyrite. In the microfacies range, the amount of isocubanite, wurtzite, unzoned euhedral pyrite decreases versus an increasing portion of framboidal, fine-grained, and spongy pyrite and also marcasite and its colloform and radial varieties. The trace element characteristics of massive sulfides of Pobeda seafloor massive sulfide (SMS) deposit are subdivided into four associations: (1) high temperature—Cu, Se, Te, Bi, Co, and Ni; (2) mid temperature—Zn, As, Sb, and Sn; (3) low temperature—Pb, Sb, Ag, Bi, Au, Tl, and Mn; and (4) seawater—U, V, Mo, and Ni. The high contents of Cu, Co, Se, Bi, Te, and values of Co/Ni ratios decrease in the range from unzoned euhedral pyrite to oscillatory-zoned and framboidal pyrite, as well as to colloform and crystalline marcasite. The trend of Co/Ni values indicates a change from hydrothermal to hydrothermal-diagenetic crystallization of the pyrite. The concentrations of Zn, As, Sb, Pb, Ag, and Tl, as commonly observed in pyrite formed from mid- and low-temperature fluids, decline with increasing crystal size of pyrite and marcasite. Coarse oscillatory-zoned pyrite crystals contain elevated Mn compared to unzoned euhedral varieties. Framboidal pyrite hosts maximum concentrations of Mo, U, and V probably derived from ocean water mixed with hydrothermal fluids. In the Pobeda SMS deposit, the position of microfacies changes from the black smoker feeder zone at the base of the ore body, to seafloor marcasite-pyrite from diffuser fragments in sulfide breccias. We suggest that the temperatures of mineralization decreased in the same direction and determined the zonal character of deposit.

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Insights into Extinct Seafloor Massive Sulfide Mounds at the TAG, Mid-Atlantic Ridge

Minerals ◽

10.3390/min8070302 ◽

2018 ◽

Vol 8 (7) ◽

pp. 302 ◽

Cited By ~ 4

Author(s):

Berit Lehrmann ◽

Iain Stobbs ◽

Paul Lusty ◽

Bramley Murton

Keyword(s):

Mineral Resources ◽

Massive Sulfide ◽

Economic Potential ◽

Black Smoker ◽

Iron Mineral ◽

Weathering Processes ◽

Mid Atlantic Ridge ◽

Third Dimension ◽

Seafloor Massive Sulfide ◽

Good Agreement

Over the last decade there has been an increasing interest in deep-sea mineral resources that may contribute to future raw metal supply. However, before seafloor massive sulfides (SMS) can be considered as a resource, alteration and weathering processes that may affect their metal tenor have to be fully understood. This knowledge cannot be obtained by assessing the surface exposures alone. Seafloor drilling is required to gain information about the third dimension. In 2016, three extinct seafloor massive sulfide mounds, located in the Trans-Atlantic Geotraverse (TAG) hydrothermal area of the Mid-Atlantic Ridge were drilled. A mineralogical and textural comparison of drill core and surface-grab samples revealed that in recent ceased mounds high-temperature copper assemblages typical for black smoker chimneys are still present whereas in longer extinct mounds the mineralogy is pre-dominated by an iron mineral assemblage. Zinc becomes remobilized early in the mound evolution and forms either a layer in the upper part of the mound or has been totally leached from its interior. Precipitation temperatures of sphalerite calculated using the Fe/Zn ratio can help to identify these remobilization processes. While the Fe/Zn ratios of primary sphalerites yield temperatures that are in very good agreement with fluid temperatures measured in white smokers, calculated temperatures for sphalerites affected by remobilization are too high for SMS. Overall drilling of SMS provides valuable information on the internal structure and mineralogy of the shallow sub-surface, however, additional drilling of SMS, at a greater depth, is required to fully understand the processes affecting SMS and their economic potential.

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Mineralization and Alteration of a Modern Seafloor Massive Sulfide Deposit Hosted in Mafic Volcaniclastic Rocks

Economic Geology ◽

10.5382/econgeo.4666 ◽

2019 ◽

Vol 114 (5) ◽

pp. 857-896 ◽

Cited By ~ 5

Author(s):

Melissa O. Anderson ◽

Mark D. Hannington ◽

Timothy F. McConachy ◽

John W. Jamieson ◽

Maria Anders ◽

...

Keyword(s):

Low Temperature ◽

Massive Sulfide ◽

Hydrothermal Fluids ◽

Sulfide Deposit ◽

Massive Sulfide Deposit ◽

Remotely Operated Vehicle ◽

Eruptive Fissure ◽

Seawater Sulfate ◽

Volcaniclastic Rocks ◽

Seafloor Massive Sulfide

Abstract Tinakula is the first seafloor massive sulfide deposit described in the Jean Charcot troughs and is the first such deposit described in the Solomon Islands—on land or the seabed. The deposit is hosted by mafic (basaltic-andesitic) volcaniclastic rocks within a series of cinder cones along a single eruptive fissure. Extensive mapping and sampling by remotely operated vehicle, together with shallow drilling, provide insights into deposit geology and especially hydrothermal processes operating in the shallow subsurface. On the seafloor, mostly inactive chimneys and mounds cover an area of ~77,000 m2 and are partially buried by volcaniclastic sand. Mineralization is characterized by abundant barite- and sulfide-rich chimneys that formed by low-temperature (<250°C) venting over ~5,600 years. Barite-rich samples have high SiO2, Pb, and Hg contents; the sulfide chimneys are dominated by low-Fe sphalerite and are high in Cd, Ge, Sb, and Ag. Few high-temperature chimneys, including zoned chalcopyrite-sphalerite samples and rare massive chalcopyrite, are rich in As, Mo, In, and Au (up to 9.26 ppm), locally as visible gold. Below the seafloor, the mineralization includes buried intervals of sulfide-rich talus with disseminated sulfides in volcaniclastic rocks consisting mainly of lapillistone with minor tuffaceous beds and autobreccias. The volcaniclastic rocks are intensely altered and variably cemented by anhydrite with crosscutting sulfate (± minor sulfide) veins. Fluid inclusions in anhydrite and sphalerite from the footwall (to 19.3 m below seafloor; m b.s.f.) have trapping temperatures of up to 298°C with salinities close to, but slightly higher than, that of seawater (2.8–4.5 wt % NaCl equiv). These temperatures are 10° to 20°C lower than the minimum temperature of boiling at this depth (1,070–1,204 m below sea level; m b.s.l.), suggesting that the highest-temperature fluids boiled below the seafloor. The alteration is distributed in broadly conformable zones, expressed in order of increasing depth and temperature as (1) montmorillonite/nontronite, (2) nontronite + corrensite, (3) illite/smectite + pyrite, (4) illite/smectite + chamosite, and (5) chamosite + corrensite. Zones of argillic alteration are distinguished from chloritic alteration by large positive mass changes in K2O (enriched in illite/smectite), MgO (enriched in chamosite and corrensite), and Fe2O3 (enriched in pyrite associated with illite/smectite alteration). The δ18O and δD values of clay minerals confirm increasing temperature with depth, from 124° to 256°C, and interaction with seawater-dominated hydrothermal fluids at high water/rock ratios. Leaching of the volcanic host rocks and thermochemical reduction of seawater sulfate are the primary sources of sulfur, with δ34S values of sulfides, from –0.8 to 3.4‰, and those of sulfate minerals close to seawater sulfate, from 19.3 to 22.5‰. The mineralization and alteration at Tinakula are typical of a class of ancient massive sulfide deposits hosted mainly by permeable volcaniclastic rocks with broad, semiconformable alteration zones. Processes by which these deposits form have never been documented in modern seafloor massive sulfide systems, because they mostly develop below the seafloor. Our study shows how hydrothermal fluids can become focused within permeable rocks by progressive, low-temperature fluid circulation, leading to a large area (>150,000 m2) of alteration with reduced permeability close to the seafloor. In our model, overpressuring and fracturing of the sulfate- and clay-cemented volcaniclastic rocks produced the pathways for higher-temperature fluids to reach the seafloor, present now as sulfate-sulfide veins within the footwall. In the geologic record, the sulfate (anhydrite) is not preserved, leaving a broad zone of intense alteration with disseminated and stringer sulfides typical of this class of deposits.

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The oldest seafloor massive sulfide deposits at the Mid-Atlantic Ridge: 230Th/U chronology and composition

Geochronometria ◽

10.1515/geochr-2015-0009 ◽

2015 ◽

Vol 42 (1) ◽

Cited By ~ 7

Author(s):

Vladislav Kuznetsov ◽

Eriks Tabuns ◽

Kathrine Kuksa ◽

Georgy Cherkashov ◽

Fedor Maksimov ◽

...

Keyword(s):

Massive Sulfide ◽

Hydrothermal Activity ◽

Ocean Floor ◽

Hydrothermal Field ◽

Sulfide Deposits ◽

Massive Sulfides ◽

Geochemical Properties ◽

Geochemical Study ◽

Mid Atlantic Ridge ◽

Seafloor Massive Sulfide

Abstract A geochronological and geochemical study on 10 samples of seafloor massive sulfides (SMS) from the inactive Peterburgskoye hydrothermal field at the Mid-Atlantic Ridge (MAR) was carried out. The 230Th/U ages of the SMS are the oldest for the Quaternary hydrothermal ores ever found at the ocean floor. According to them the hydrothermal activity at Peterburgskoye field started at least 170 ka and continued down to 63 ka. The oldest hydrothermal ores from this field consist mainly of pyrite and chalcopyrite and have geochemical properties typical for SMS associated with basalts.

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Seafloor Massive Sulfide deposits discovered at the Mid-Atlantic Ridge - potential target for the ocean mining in the Area

OCEANS'11 MTS/IEEE KONA ◽

10.23919/oceans.2011.6106978 ◽

2011 ◽

Cited By ~ 1

Author(s):

Georgy Cherkashov

Keyword(s):

Massive Sulfide ◽

Sulfide Deposits ◽

Potential Target ◽

Massive Sulfide Deposits ◽

Mid Atlantic Ridge ◽

Seafloor Massive Sulfide ◽

Ocean Mining

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Seafloor Massive Sulfide Deposits of the Northern Equatorial Mid-Atlantic Ridge

Океанология ◽

10.7868/s0030157413050031 ◽

2013 ◽

Vol 53 (5) ◽

pp. 680-693 ◽

Cited By ~ 1

Author(s):

G. A. Cherkashov ◽

V. N. Ivanov ◽

V. I. Bel’tenev ◽

L. I. Lazareva ◽

I. I. Rozhdestvenskaya ◽

...

Keyword(s):

Massive Sulfide ◽

Sulfide Deposits ◽

Massive Sulfide Deposits ◽

Mid Atlantic Ridge ◽

Seafloor Massive Sulfide

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Variation scale and heterogeneity of the lead isotope composition in sulfides from hydrothermal fields of the Mid-Atlantic Ridge: Evidence from high-precision MC-ICP-MS isotopic data

Doklady Earth Sciences ◽

10.1134/s1028334x11040106 ◽

2011 ◽

Vol 437 (2) ◽

pp. 507-512 ◽

Cited By ~ 1

Author(s):

I. V. Chernyshev ◽

N. S. Bortnikov ◽

A. V. Chugaev ◽

V. N. Golubev ◽

Y. Fouquet ◽

...

Keyword(s):

High Precision ◽

Lead Isotope ◽

Isotope Composition ◽

Isotopic Data ◽

Lead Isotope Composition ◽

Icp Ms ◽

Mid Atlantic Ridge ◽

Hydrothermal Fields

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Comparative analysis of the mineral and chemical compositions of black smoker smoke at the TAG and Broken Spur hydrothermal fields, mid-Atlantic ridge

Geochemistry International ◽

10.1134/s0016702907070063 ◽

2007 ◽

Vol 45 (7) ◽

pp. 698-716 ◽

Cited By ~ 6

Author(s):

V. Yu. Rusakov

Keyword(s):

Comparative Analysis ◽

Chemical Compositions ◽

Black Smoker ◽

Mid Atlantic Ridge ◽

Hydrothermal Fields

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Tellurium-bearing minerals in clastic ores of Ybileynoe massive sulfide deposit (South Urals)

Геология рудных месторождений ◽

10.31857/s0016-777061239-71 ◽

2019 ◽

Vol 61 (2) ◽

pp. 39-71

Author(s):

A. S. Tseluyko ◽

V. V. Maslennikov ◽

N. R. Ayupova ◽

S. P. Maslennikova ◽

L. V. Danyushevsky

Keyword(s):

Solid Solution ◽

Massive Sulfide ◽

Sulfide Deposit ◽

South Urals ◽

Massive Sulfide Deposit ◽

Black Smoker ◽

Fine Grained ◽

Intermediate Solid Solution ◽

Sedimentation Processes

At the well preserved Yubileynoe VMS deposit (South Urals), sulfide breccias and turbidites contain abundant tellurides represented by hessite, coloradoite, altaite, volynskite, stutzite, petzite, calaverite as well as phases of intermediate solid solution tellurobismuthite – rucklidgeite. There is three generation of tellurides were highlighted: 1) primary hydrothermal tellurides in the fragments of chalcopyrite and sphalerite of chalcopyrite-rich black smoker chimneys; 2) authigenic tellurides in pseudomorphic chalcopyrite and veins of chalcopyrite after fragments of colloform and granular pyrite; 3) authigenic tellurides in pyrite nodules. Authigenic tellurides are widespread in pyrite-chalcopyrite turbidites. In sulfide turbidites and gravelites with fragments of sphalerite-pyrite, pyrite-sphalerite paleosmoker chimneys and clasts of colloform and fine-grained seafloor hydrothermal crusts, primary hydrothermal and authigenic tellurides are less common. Siliceous siltstones intercalated with sulfide turbidites contain pyrite nodules, which peripheral parts contain inclusions of epigenetic tellurides. It is assumed that the source of tellurium for authigenic tellurides were fragments of colloform pyrite and hydrothermal chalcopyrite of pyrite-chalcopyrite chimneys, which dissolved during post-sedimentation processes. The main concentrators of tellurium in clastic ores are pseudomorphic chalcopyrite, which inherits high contents of Te, Bi, Au, Ag, Co, Ni, As from the substituted colloform pyrite, and varieties of granular pyrite, containing microinclusions of tellurobismuthite (Bi, Te), petzite (Au, Ag, Te), altaite (Pb, Te), coloradoite and hessite (Ag, Te).

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Prospectivity Mapping for Magmatic-Related Seafloor Massive Sulfide on the Mid-Atlantic Ridge Applying Weights-of-Evidence Method Based on GIS

Minerals ◽

10.3390/min11010083 ◽

2021 ◽

Vol 11 (1) ◽

pp. 83

Author(s):

Lushi Liu ◽

Jilong Lu ◽

Chunhui Tao ◽

Shili Liao

Keyword(s):

Massive Sulfide ◽

Spreading Rate ◽

Mineral Prospectivity Mapping ◽

Spreading Ridges ◽

Mid Atlantic Ridge ◽

Slow Spreading ◽

Mineral Prospectivity ◽

Seafloor Massive Sulfide ◽

Crust Thickness ◽

Prospectivity Mapping

The Mid-Atlantic Ridge belongs to slow-spreading ridges. Hannington predicted that there were a large number of mineral resources on slow-spreading ridges; however, seafloor massive sulfide deposits usually develop thousands of meters below the seafloor, which make them extremely difficult to explore. Therefore, it is necessary to use mineral prospectivity mapping to narrow the exploration scope and improve exploration efficiency. Recently, Fang and Shao conducted mineral prospectivity mapping of seafloor massive sulfide on the northern Mid-Atlantic Ridge, but the mineral prospectivity mapping of magmatic-related seafloor massive sulfide on the whole Mid-Atlantic Ridge scale has not yet been carried out. In this study, 11 types of data on magmatic-related seafloor massive sulfide mineralization were collected on the Mid-Atlantic Ridge, namely water depth, slope, oceanic crust thickness, large faults, small faults, ridge, bedrock age, spreading rate, Bouguer gravity, and magnetic and seismic point density. Then, the favorable information was extracted from these data to establish 11 predictive maps and to create a mineral potential model. Finally, the weights-of-evidence method was applied to conduct mineral prospectivity mapping. Weight values indicate that oceanic crust thickness, large faults, and spreading rate are the most important prospecting criteria in the study area, which correspond with important ore-controlling factors of magmatic-related seafloor massive sulfide on slow-spreading ridges. This illustrates that the Mid-Atlantic Ridge is a typical slow-spreading ridge, and the mineral potential model presented in this study can also be used on other typical slow-spreading ridges. Seven zones with high posterior probabilities but without known hydrothermal fields were delineated as prospecting targets. The results are helpful for narrowing the exploration scope on the Mid-Atlantic Ridge and can guide the investigation of seafloor massive sulfide resources efficiently.

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