A missing link between ancient and active mafic-hosted seafloor hydrothermal systems – Magmatic volatile influx in the exceptionally preserved Mala VMS deposit, Troodos, Cyprus

Martin, Andrew J.; McDonald, Iain; Jenkin, Gawen R.T.; McFall, Katie; Boyce, Adrian J.; Jamieson, John; Macleod, Christopher

doi:10.1016/j.chemgeo.2021.120127

Cited by 18 publications

(27 citation statements)

References 110 publications

(255 reference statements)

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“…Herzig et al 1998;Huston et al 2011), where magmas are more volatile-rich relative to mafic-hosted mid-ocean ridge (MOR) environments (Wallace 2005). However, this signature was also recorded in an ancient mafic VMS deposit (Martin et al 2021). This sulfur isotope composition contrasts signatures typical of MOR environments, where δ 34 S values in sulfide minerals are positive, indicating a combination of sulfur from thermochemical sulfate reduction (TSR) of seawater at high temperatures (> 160 °C) in the presence of iron-bearing minerals and leaching of sulfur and primary igneous sulfide minerals from igneous host rocks (Ono et al 2007).…”

Section: Introductionmentioning

confidence: 96%

“…Variation in the sulfur isotope composition of pyrite has largely been constrained in Troodos VMS deposits using whole-rock analytical methods of sulfide minerals with the median composition for all Troodos VMS sulfide minerals of 4.6 ± 2.7‰ (1σ, n = 220) indicating that sulfur is primarily sourced from both the leaching of igneous sulfur/ sulfide and TSR of seawater (Hannington et al 1998;Parvaz 2014;Keith et al 2016a;Pedersen et al 2017;Martin et al 2020). However, significant variation is noted in the sulfur Mala is located in the SW of the ophiolite at the LPL/BG transitional horizon (after Martin et al 2018) isotope composition of pyrite across Troodos VMS deposits with the δ 34 S values of pyrite ranging from − 7.6 to 13.2‰ (Martin et al 2020(Martin et al , 2021. Samples of disseminated pyrite that occur within the volcanic stratigraphy exhibit significantly lower δ 34 S values than those typical for Troodos VMS deposits; pyrite is depleted in 34 S, with δ 34 S values ranging from − 22.2 to − 6.9‰.…”

Section: Introductionmentioning

confidence: 99%

“…The source of metals in volcanogenic massive sulfide (VMS) and actively forming seafloor massive sulfide (SMS) deposits remains poorly constrained and actively debated (Sillitoe et al 1996;Yang and Scott 1996;Jowitt et al 2012;Keith et al 2018;Martin et al 2020;Patten et al 2020). Principally, two metal sources can contribute to the metal budget of VMS deposits: leaching of metals from underlying host rocks during hydrothermal alteration (Richardson et al 1987;Jowitt et al 2012;Banerjee et al 2000;Patten et al 2017) and the addition of a magmatic volatile phase to the overlying hydrothermal system Scott 1996, 2002;de Ronde et al 2011;Martin et al 2020Martin et al , 2021Patten et al 2020). The relative contribution of metals from these two sources and how they change with system maturity (i.e.…”

Section: Introductionmentioning

confidence: 99%

“…However, very few studies utilize a combined approach (e.g. Rouxel et al 2004;Sharman et al 2015;Meng et al 2020;Martin et al 2021) that takes into consideration any systematic relationship between trace element enrichment profiles and the sulfur isotopic composition of sulfide minerals; this is especially true when considering the complex nature of different pyrite textures, generations (i.e. overgrowths) and variation that occurs at the scale of individual mineral grains.…”

Section: Introductionmentioning

confidence: 99%

“…In volatile-rich, subduction influenced VMS deposits, the systematic enrichment of certain metals such as Pb, As, Sb, Bi, Hg and Te (Wohlgemuth-Ueberwasser et al 2015); Se, Cu and Te (Keith et al 2016a); Bi and Te (Mathieu 2019); or Se, Cu, Te and Au (Martin et al 2021) have been proposed to indicate the addition of a metal-rich magmatic volatile phase to the hydrothermal system from degassing of shallow magma reservoirs (e.g. Huston et al 2011).…”

Section: Introductionmentioning

confidence: 99%

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Mineral-scale variation in the trace metal and sulfur isotope composition of pyrite: implications for metal and sulfur sources in mafic VMS deposits

et al. 2021

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The link between metal enrichment and the addition of a magmatic volatile phase in volcanogenic massive sulfide deposits and actively forming seafloor massive sulfide deposits remains poorly characterized. This is especially true when considering how metal, sulfur and fluid flux change with time. In this study, we combine in situ sulfur isotope (δ 34 S; n = 31) measurements with trace metal chemistry of pyrite (n = 143) from the Mala VMS deposit, Troodos, Cyprus. The aim of our study is to assess the links between volatile influx and metal enrichment and establish how, or indeed if, this is preserved at the scale of individual mineral grains. We classify pyrite based on texture into colloform, granular, disseminated and massive varieties. The trace metal content of different pyrite textures is highly variable and relates to fluid temperature and secondary reworking that are influenced by the location of the sample within the mound. The sulfur isotope composition of pyrite at Mala ranges from − 17.1 to 7.5‰ (n = 31), with a range of − 10.9 to 2.5‰ within a single pyrite crystal. This variation is attributed to changes in the relative proportion of sulfur sourced from (i) SO 2 disproportionation, (ii) thermochemical sulfate reduction, (iii) the leaching of igneous sulfur/sulfide and (iv) bacterial sulfate reduction. Our data shows that there is no correlation between δ 34 S values and the concentration of volatile elements (Te, Se) and Au in pyrite at Mala indicating that remobilization of trace metals occurred within the mound.

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mineral-scale variation in the trace metal and sulfur isotope composition of pyrite: implications for metal and sulfur sources in mafic VMS deposits

et al. 2021

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Light Stable Isotopes in Volcanic-Hosted Massive Sulfide Ore Systems

Huston

LaFlamme

Beaudoin

et al. 2023

Mineral Resource Reviews

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Volcanic-hosted massive sulfide (VHMS) deposits, the ancient analogues of “black smoker” deposits that currently form on the seafloor, are the products of complex mineral systems involving the interaction of seawater with the underlying volcanic pile and associated magmatic intrusions. Light stable isotopes, particularly those of oxygen, hydrogen and sulfur, have had a strong influence in determining sources of ore fluids and sulfur as well as elucidating geological processes important in the VHMS mineral systems. Oxygen and hydrogen isotope data indicate that evolved seawater was the dominant ore-forming fluid in VHMS mineral systems through geological time, although a small proportion of deposits, including high sulfidation and tin-rich deposits, may have a significant, or dominant, magmatic-hydrothermal fluid component. Higher-temperature (> 200 °C) interaction of evolved seawater alters the rock pile below the seafloor, producing δ18O depletion anomalies at the deposit and district scales that can be used as a vector to ore. In contrast, lower-temperature hydrothermal alteration results in δ18O-enriched zones that commonly cap mineralized positions. An apparent decrease in the degree of high temperature 18O depletion with time may relate to the increasing importance of felsic-dominated host successions in younger deposits. δ18O anomalies have potential as an exploration tool, and have contributed directly to discovery. The other important contribution of stable isotopes to understanding the VHMS mineral system is quantification of the contribution of sulfur sources. Conventional δ34S data, when combined with Δ33S data acquired using recently developed technologies, indicate that the dominant sulfur source is igneous sulfur, either leached from the volcanic pile or introduced as a magmatic volatile (these sources are not distinguishable). The thermochemical reduction of seawater sulfate is also an important, but subordinate, sulfur source. Estimation of the proportion of seawater sulfate with geological age indicate that, on average, it has increased from 5–10% in the Archean to 20–25% in the Phanerozoic. This most likely reflects the increase in seawater sulfate contents through geological time. Although untested as an exploration tool, variations in sulfur isotope data may have utility is discriminating fertile from barren sulfide accumulations or providing vectors to ores at the deposits scale. As exploration tools, light stable isotopes suffer from a relatively high cost and slow turn-around time. If these limitations can be overcome, and new analytical methods can be developed, light stable isotopes may emerge as another tool for exploration, particularly as discoveries are made at greater depth and under cover.

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Trace metal and sulfur cycling in a hydrothermally active arc volcano: deep-sea drilling of the Brothers volcano, Kermadec arc, New Zealand

et al. 2022

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Brothers volcano, located on the Kermadec arc north of New Zealand, hosts two geochemically distinct hydrothermal systems. The NW Caldera and Upper Cone hydrothermal fields exhibit distinct fluid compositions that are significantly influenced by seawater and magmatic volatiles, respectively. In this study, we present trace metal chemistry and sulfur isotope compositions of pyrite within hydrothermally-altered volcanic rocks recovered from drill cores at depths of up to 429 m below the seafloor collected during the International Ocean Discovery Program's Expedition 376. Magmatic volatile-influenced alteration resulting in pyrophyllite ± natroalunite assemblages occurs at the Upper Cone and at the NW Caldera below 189 m. At the NW Caldera, a later seawater-derived hydrothermal fluid overprints magmatic volatile alteration forming chlorite-rich alteration. Pyrite at the Upper Cone is fine-grained, euhedral and enriched in Cu, As, Sb, Pb and Pt and has an average δ 34 S composition of -5.5 ± 2.9‰ (1σ, n= 32). In contrast, pyrite associated with pyrophyllite-rich alteration at the older NW Caldera site is coarse-grained, subhedral and has higher Co, Se, Te and Bi contents but a comparable average δ 34 S value of -4.8 ± 5.5‰ (1σ, n= 26). The difference in trace metal content between pyrite from pyrophyllite ± natroalunite assemblages at the NW Caldera and Upper Cone site indicates a change in the trace metal enrichment signature of pyrite with the age of the hydrothermal system. Pyrite from chlorite-rich alteration (NW Caldera) is depleted in Cu, Te and Bi relative to all magmatic volatile-influenced pyrite but has a similar average δ 34 S composition of -4.6 ± 3.5‰ (1σ, n= 20). The similarity in trace metal enrichment signature and average δ 34 S composition of pyrite, regardless of associated alteration mineral assemblage shows that the initial magmatic volatile trace metal signature and sulfur isotope composition of pyrite is preserved during fluid overprinting. The lower content of Cu, Te and Bi in pyrite from chlorite-rich alteration confirms the importance of seawater-derived hydrothermal fluids in metal mobilization and consequent formation of hydrothermal precipitates at the seafloor.

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A missing link between ancient and active mafic-hosted seafloor hydrothermal systems – Magmatic volatile influx in the exceptionally preserved Mala VMS deposit, Troodos, Cyprus

Cited by 18 publications

References 110 publications

Mineral-scale variation in the trace metal and sulfur isotope composition of pyrite: implications for metal and sulfur sources in mafic VMS deposits

Mineral-scale variation in the trace metal and sulfur isotope composition of pyrite: implications for metal and sulfur sources in mafic VMS deposits

Light Stable Isotopes in Volcanic-Hosted Massive Sulfide Ore Systems

Trace metal and sulfur cycling in a hydrothermally active arc volcano: deep-sea drilling of the Brothers volcano, Kermadec arc, New Zealand

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