scholarly journals Trace element proxies and mineral indicators of hydrothermal fluid composition and seafloor massive sulfide deposit formation processes

2017 ◽  
Author(s):  
Guy N. Evans
Keyword(s):  
Trace Element ◽  
Hydrothermal Fluid ◽  
Massive Sulfide ◽  
Sulfide Deposit ◽  
Fluid Composition ◽  
Formation Processes ◽  
Massive Sulfide Deposit ◽  
Deposit Formation ◽  
Seafloor Massive Sulfide

scholarly journals Subseafloor Alteration of a Modern Mafic-Volcaniclastic Hosted Seafloor Massive Sulfide Deposit

2020 ◽  
Author(s):  
Melissa. O Anderson ◽  
Mark Hannington ◽  
Timothy McConachy ◽  
John Jamieson ◽  
Thor Hansteen ◽  
...  
Keyword(s):  
Massive Sulfide ◽  
Sulfide Deposit ◽  
Massive Sulfide Deposit ◽  
Seafloor Massive Sulfide

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

2019 ◽  
Vol 114 (5) ◽  
pp. 857-896 ◽  
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.

scholarly journals Mineralogical and geochemical features of pyrite nodules of sulfide turbidites from the Talgan Cu–Zn massive sulfide deposit (South Urals)

2019 ◽  
pp. 518-539
Author(s):  
N. R. Ayupova ◽  
V. V. Maslennikov ◽  
D. A. Artemyev ◽  
I. A. Blinov
Keyword(s):  
Trace Element ◽  
Host Rock ◽  
Inner Core ◽  
Outer Zone ◽  
Massive Sulfide ◽  
Intermediate Zone ◽  
Sulfide Deposit ◽  
South Urals ◽  
Massive Sulfide Deposit ◽  
The Core

Pyrite nodules were found in thin-layered sulfide ores localized at the flanks of the Talgan Cu‒Zn massive sulfide deposit (South Urals). The nodules consist of (1) an inner core of microgranular pyrite with inclusions of authigenic sulfides and host rock minerals, (2) an intermediate zone of anhedral and subhedral pyrite metacrystals, (3) an outer zone formed by parallel subhedral pyrite crystals and (4) dioctahedral chlorite rimming the pyrite crystals of zone 3. Each zone exhibits specific trace element association, which is identified using LA ICP-MS micromapping. The trace element content of pyrite significantly (by 13 orders of magnitude) decreases in a range of microgranular pyrite of the core an- and subhedral pyrite crystals of the intermediate zone subhedral pyrite crystals of the outer zone (average values, ppm): 131069 Zn, 241001783 Pb, 1323134 As, 10271.81 Co, 4564 Ni, 39038 Ag, 0.10.01 Au, 550.6 Te, 9.80.6 Bi. The subhedral pyrite crystals of the outer zone are enriched (ppm, up to) in Cu (8367), Sb (1627) and Mn (734) relative to microgranular pyrite of the core. The extremely high trace element contents are related to the inclusions of authigenic chalcopyrite, sphalerite, fahlore, gold and silver minerals. The host rock components of the nodules include quartz, calcite, chlorite, illite and REE minerals. The ore clasts of distal sulfide turbidites mixed with hyaloclastites, which were altered during dia- and anadiagenesis, were the source of ore material for the nodules.

scholarly journals Geology and Geochemistry of the VOLPA Seafloor Massive Sulfide Deposit, Niua Volcano, Tonga

2020 ◽  
Author(s):  
Talia Moum ◽  
Melissa. O Anderson ◽  
John Jamieson ◽  
Richard Parkinson ◽  
Elizabeth Austin
Keyword(s):  
Massive Sulfide ◽  
Sulfide Deposit ◽  
Massive Sulfide Deposit ◽  
Seafloor Massive Sulfide
Sign in / Sign up

Export Citation Format

Share Document