The Minor Element Endowment of Modern Sea-Floor Massive Sulfides and Comparison with Deposits Hosted in Ancient Volcanic Successions

Monecke, Thomas; Petersen, Sven; Hannington, Mark D.; Grant, Hannah; Samson, Iain M.

doi:10.5382/rev.18.11

Cited by 54 publications

(93 citation statements)

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“…The calculated temperatures are 303.5°C for the Longqi field and 286.7°C for the Duanqiao field. The incorporation of Cd into the sphalerite structure also favors higher temperatures (Chen et al, 1988;Cook, 2009;Monecke et al, 2016). The average Cd contents of undamaged sphalerite from the Longqi and Duanqiao fields are 1950 and 525.66 ppm, respectively (Table 1), supporting the above observation about temperature.…”

Section: Implication From Sulfide Chemistrysupporting

confidence: 74%

“…As mentioned above, sphalerites are significantly enriched in Cd (up to 7190 ppm in the Longqi field and up to 5870 ppm in the Duanqiao field). Since Cd 2+ also has an ionic radius similar to that of Zn 2+ , significant amounts of Cd can be incorporated into the sphalerite structure via a direct substitution, Cd 2+ ↔ Zn 2+ (Cook et al, 2009;Bonnet et al, 2016), especially at high temperatures (Chen et al, 1988;Cook, 2009;Monecke et al, 2016). In this study, sphalerites with the highest Cd contents from both Oct.…”

Section: Sphaleritementioning

confidence: 56%

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Mineralogy and Chemistry of Sulfides from the Longqi and Duanqiao Hydrothermal Fields in the Southwest Indian Ridge

Zhang

Hou

et al. 2018

Acta Geologica Sinica (Eng)

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Recent investigations found that hydrothermal activity and sulfide mineralization occurs along the Southwest Indian Ridge (SWIR). The Longqi and Duanqiao hydrothermal fields between 49° E and 53° E of the SWIR are two prospective mineralization areas discovered by Chinese scientists. With the aim to determine the mineralogical and chemical characteristics of sulfide minerals, we have conducted detailed studies for samples from the two areas using an optical microscope, X‐ray diffractometer, scanning electron microscope, and electron microprobe. The mineralization processes in the Longqi area are divided into three main stages: (1) the low‐medium‐temperature stage: colloform pyrite (Py I) + marcasite → euhedral pyrite (Py II), (2) the high‐temperature stage: isocubanite (±exsolved chalcopyrite) + pyrrhotite → coarse‐grained chalcopyrite (Ccp I), and (3) the medium–low‐temperature stage: sphalerite + fine‐grained chalcopyrite inclusions (Ccp II) → aggregates of anhedral pyrite (Py III) ± marcasite → Fe‐oxide (‐hydroxide) + amorphous silica. The mineralization processes in the Duanqiao area are divided into two main stages: (1) the medium–high‐temperature stage: subhedral and euhedral pyrite (Py I′) → coarse‐grained chalcopyrite (Ccp I′) and (2) the medium–low‐temperature stage: sphalerite → fine‐grained chalcopyrite (Ccp II′) + chalcopyrite inclusions (Ccp II′) → silica‐cemented pyrite (Py II′) + marcasite → Fe‐oxide + amorphous silica. We suggest that the fine‐grained chalcopyrite inclusions in sphalerite from Longqi and Duanqiao were formed by co‐precipitation and replacement mechanisms, respectively. Primary sphalerites from both fields are enriched in Fe (avg. 5.84 wt% for the Longqi field vs. avg. 3.69 wt% for the Duanqiao field), Co (avg. 185.56 ppm for the Longqi field vs. 160.53 ppm for the Duanqiao field), and Cd (avg. 1950 ppm for the Longqi field vs. avg. 525.26 ppm for the Duanqiao field). Cu contents in pyrite from the Duanqiao field (Py I′: avg. 849.23 ppm and Py II′: avg. 1191.11 ppm) tend to be higher than those from the Longqi field (Py I: avg. 26.67 ppm, Py II: avg. 445 ppm, and Py III: avg. 179.29 ppm). Chalcopyrite from both fields is enriched in Zn (Ccp I: avg. 3226.67 ppm, Ccp II: avg. 9280 ppm, Ccp I′: avg. 848 ppm, Ccp II′ (inclusions): avg. 1098 ppm, and Ccp II′ (fine‐grained): avg. 1795 ppm). The varying contents of Zn in the different pyrite and chalcopyrite generations may result from the zone refining process. An integrated study of the mineralogy and mineralogical chemistry suggests that the hydrothermal fluids of the Longqi area are likely conditioned with higher temperatures and relatively lower fO2 and fS2 than those of the Duanqiao area, but in contrast to the former, the latter is much affected by the compositions of the surrounding rocks.

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Section: Implication From Sulfide Chemistrysupporting

confidence: 74%

Section: Sphaleritementioning

confidence: 56%

Mineralogy and Chemistry of Sulfides from the Longqi and Duanqiao Hydrothermal Fields in the Southwest Indian Ridge

Zhang

Hou

et al. 2018

Acta Geologica Sinica (Eng)

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“…Current studies, using bulk geochemical data from 95 sites published in the literature [5,6], suggest a global resource potential for modern SMS deposits along the neovolcanic zones of the seafloor of 600 million tons, with a median grade of 3 wt % Cu, 9 wt % Zn, 2 g/t Au, and 100 g/t Ag [5,6]. However, the geochemical data being used largely originated from easily recoverable, mainly The active TAG Mound, located in the southwest of the area, comprises two distinct zones.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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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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“…The majority of previous SMS studies have tended to focus on deposit reviews and site discovery [3][4][5]7,8], deposit structure [9], general geochemistry [10], and water chemistry [11] trends. The purpose of this study is to, for the first time, perform a dedicated mineralogical study and to discuss the methods of characterisation for mineralised material from a recently discovered sulphide-bearing hydrothermal vent on the Arctic Mid-Ocean Ridge (AMOR).…”

Section: Introductionmentioning

confidence: 99%

“…One site that shows potential for SMS-style mineralisation is the Loki's Castle (73°30′ N, 8° E), located on the ultraslow spreading (6)(7)(8)(9)(10)(11)(12)(13)(14)(15) mm/year [20]) AMOR, and discovered in 2008 [8]. The Loki's Castle is a site of active hydrothermal venting occurring just south of the junction between the Mohns and Knipovich Ridges, at 2400 m depth (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Characterisation of Mineralised Material from the Loki’s Castle Hydrothermal Vent on the Mohn’s Ridge

et al. 2018

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Loki's Castle on the Arctic Mid-Ocean Ridge (AMOR) is an area of possible seafloor massive sulphide (SMS)-style mineralisation under Norwegian jurisdiction, which, due to mounting social pressure, may be a strategic future source of base and precious metals. The purpose of this study is to characterise mineralised material from a hydrothermal vent system on the AMOR in detail for the first time, and to discuss the suitability of methods used; reflected light microscopy, X-ray diffraction (XRD), whole rock geochemistry, electron probe micro-analysis (EPMA), and QEMSCAN. The primary sulphide phases, identifiable by microscopy, are pyrite and marcasite with minor pyrrhotite and galena, but multiple samples from the Loki's Castle contain economically interesting quantities of copper (hosted in isocubanite and chalcopyrite) and zinc (hosted in sphalerite), as well as silver and gold. This reinforces the notion that slow spreading ridges may host significant base metal deposits. Micro-textures (chalcopyrite inclusions and exsolutions in sphalerite and isocubanite respectively) are typically undefinable by QEMSCAN, and require quantitative measurement by EPMA. QEMSCAN can be used to efficiently generate average grain size and mineral association data, as well as composition data, and is likely to be a powerful tool in assessing the effectiveness of SMS mineral processing.

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The Minor Element Endowment of Modern Sea-Floor Massive Sulfides and Comparison with Deposits Hosted in Ancient Volcanic Successions

Cited by 54 publications

References 0 publications

Mineralogy and Chemistry of Sulfides from the Longqi and Duanqiao Hydrothermal Fields in the Southwest Indian Ridge

Mineralogy and Chemistry of Sulfides from the Longqi and Duanqiao Hydrothermal Fields in the Southwest Indian Ridge

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

Characterisation of Mineralised Material from the Loki’s Castle Hydrothermal Vent on the Mohn’s Ridge

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