How do metals escape from magmas to form porphyry-type ore deposits?

Vigneresse, Jean-Louis; Truche, Laurent; Richard, Antonin

doi:10.1016/j.oregeorev.2018.12.016

Cited by 26 publications

(6 citation statements)

References 246 publications

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“…The release of volcanic gases is thought to be related to decompression during eruptions (Edmonds, 2008). However, many observations indicate that the volatiles are saturated before the eruption, and these volatiles exacerbate subsequent eruptions (Gerlach & McGee, 1994; Vigneresse et al, 2019). The following evidence suggests that the MOT may contain a bubbly, water‐saturated shallow silicic magma reservoir.…”

Section: Discussionmentioning

confidence: 99%

The evolution of crystal‐poor rhyolite in the middle Okinawa Trough and its implications for the state of magma chamber

Luo,

Zeng,

Chen

et al. 2024

Geological Journal

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The crystal‐poor rhyolitic pumice is the product of extreme magma differentiation and is characterized by highly vesicular, honeycomb‐like structure. However, little is known about the evolutionary history and the time of volatile saturation of the pumice‐forming melt. A crystal‐poor rhyolitic pumice (TVG7‐1) has been collected from the Yoron Hole hydrothermal field in the middle Okinawa Trough, a young continental margin back‐arc basin in the western Pacific. This study conducted a detailed analysis on the texture and in situ chemical composition of plagioclase, orthopyroxene and Fe‐Ti oxides to reveal the evolution process, storage state and eruption triggers of eruptible silicic melt. Texture and zoning of specific minerals and mineral populations suggest a magmatic evolution history of open system. Additionally, the hollow reentrant texture, as well as results from plagioclase‐liquid hygrometers, confirm a water‐rich melt pocket. The exsolution of volatiles (H2O, etc.), in this melt pocket, will contribute to local oxidation conditions, which may have been recorded by the concordant behaviour of FeO and An in plagioclase. Then, the overpressure caused by volatile exsolution would destabilize the magma chamber, which will eventually be broken by magma mixing/recharge, and lead to violent melt evacuation. Consequently, crystal size distribution (CSD) provides a new perspective on understanding the kinetic effect of magma mixing/recharge in the Okinawa Trough, especially on the mineral populations. Our study reveals the petrogenesis of crystal‐poor rhyolite within the framework of the mush model, refines the magma evolution history and demonstrates that pumice magma reaches volatile saturation before the eruption.

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Section: Discussionmentioning

confidence: 99%

The evolution of crystal‐poor rhyolite in the middle Okinawa Trough and its implications for the state of magma chamber

Luo,

Zeng,

Chen

et al. 2024

Geological Journal

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“…Oxide production was monitored with 132 Th 16 O/ 132 Th ratios, which were always less than 0.2%. Twenty-two masses were monitored: 7 Li, 9 Be, 11 B, 23 Na, 27 Al, 29 Si, 30 Si, 31 P, 39 K, 43 Ca, 49 Ti, 55 Mn, 56 Fe, 63 Cu, 71 Ga, 74 Ge, 75 As, 88 Sr, 118 Sn, 121 Sb, 137 Ba, and 208 Pb. The dwelling time for 49 Ti was 0.1 s, and it was 0.01-0.03 s for the other masses.…”

Section: In-situ La-icp-ms Trace Elementsmentioning

confidence: 99%

“…They are one of the areas of focus of critical raw material studies [2]. The deposits are normally found along the convergent plate tectonic margins, formed via optimally-integrated magmatic and hydrothermal processes rooted in the subduction lithospheric mantle [3][4][5][6][7]. Despite several decades of studies, many details still await to be revealed, particularly regarding the mechanism of vein growth, reopening, and sulfide deposition [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Vein Formation and Reopening in a Cooling Yet Intermittently Pressurized Hydrothermal System: The Single-Intrusion Tongchang Porphyry Cu Deposit

Richard

Pironon

et al. 2023

Geosciences

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Porphyry deposits are the dominant sources of copper and major sources of several base and precious metals. They are commonly formed via the repeated emplacement of hydrous magmas and associated fluid exsolution. As a result, mineralized hydrothermal veins may undergo multiple deposition and reopening processes that are not fully accounted for by existing fluid models. The Tongchang porphyry Cu deposit is a rare example of being related to a single intrusion. The simplicity in intrusive history provides an ideal starting point for studying fluid processes in more complex multi-intrusion porphyry systems. Detailed scanning electron microscope (SEM) cathodoluminescence imaging (CL) revealed rich microtextures in quartz and anhydrite that point to a fluid timeline encompassing early quartz deposition followed by fluid-aided dynamic recrystallization, which was succeeded by an intermediate stage of quartz dissolution and subsequent deposition, and ended with a late stage of continuous quartz deposition, brecciation, and fracturing. Vein reopening is more common than expected. Fifteen out of seventeen examined vein samples contained quartz and/or anhydrite that was older or younger than the vein age defined by vein sequences. Thermobarometry and solubility analysis suggests that the fluid events occurred in a general cooling path (from 650 °C to 250 °C), interspersed with two episodes of fluid pressurization. The first episode occurred at high-T (>500 °C), under lithostatic conditions alongside dynamic recrystallization, whereas the second one took place at a lower temperature (~400 °C), under lithostatic to hydrostatic transition conditions. The main episode of chalcopyrite veining took place subsequent to the second overpressure episode at temperatures of 380–300 °C. The results of this study reaffirm that thermal and hydraulic conditions are the main causative factors for vein reopening and growth in porphyry deposits.

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“…Magmas in post-subduction settings are derived from the subcontinental lithospheric mantle that was previously metasomatized during arc magmatism, possibly leading to an enrichment in chalcophile elements and a high ore-forming potential (Richards, 2011;Holwell et al, 2019). The water-rich (≥4 wt.%) and oxidized (ΔFMQ = 0 to +2) character of these magmas enhances the partitioning of metals into exsolving magmatic fluids, which may feed porphyry-epithermal systems in the upper crust (Sillitoe, 2010;Lee et al, 2012;Vigneresse et al, 2019;Richards, 2022). High-K calc-alkaline to alkaline igneous rocks that host a hydrothermal system have a high capacity to buffer the fluid pH towards higher values due to fluid-rock interaction (Kouzmanov and Pokrovski, 2012;Smith et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

In-situ trace element and S isotope systematics in pyrite from three porphyry-epithermal prospects, Limnos Island, Greece

Börner

Keith²,

Bücker³

et al. 2022

Front. Earth Sci.

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Porphyry-epithermal systems associated with high-K calc-alkaline to alkaline igneous host rocks may be prospective for the recovery of Te among related elements like Cu, Ag, and Au. Limnos Island, as part of the Tethyan magmatic belt, is such an example, where (telescoped) porphyry-epithermal mineralization is accompanied by different alteration-styles reflecting various hydrothermal processes. Here, we present in-situ S isotope and trace element data of pyrite, which records the fluid evolution from the early porphyry to the late epithermal stage in three distinct prospects (Fakos, Kaspakas, Sardes) on Limnos Island. Pyrite in the sericitic alteration of Fakos mainly formed from single-phase magma-derived fluids lacking evidence for phase separation, as reflected by relatively constant δ34S (about −4‰) and Co/Ni (0.1-1) values. By contrast, in the sericitic alteration of Kaspakas and the following epithermal stages, an influence of boiling is implied by negative δ34S values to −15‰, significant intergrain δ34S variations (>3‰), highly variable Co/Ni (100-0.01) and As/Co (10-0.001) in pyrite. Higher δ34S values (above −4‰) in porphyry pyrite from Sardes and partly in the other two hydrothermal systems are related to mixing between magmatic S, and S which was transported through deeply circulated seawater and/or meteoric water. We propose that fluid-rock interaction buffered the pH to higher values, which enhanced the solubility of Au and Te. Subsequent boiling processes caused the Au deposition, whereas Te partitioned into the vapor and finally precipitated upon condensation into meteoric water. This process is accompanied by continuous cooling during fluid ascent from 780°C to <300°C, as indicated by increasing Sb, Tl, and Pb in pyrite from the porphyry to the epithermal stage. Consequently, the in situ δ34S and trace element analysis allows to constrain the depositional environment of economic metals like Au and Te in porphyry-epithermal prospects.

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How do metals escape from magmas to form porphyry-type ore deposits?

Cited by 26 publications

References 246 publications

The evolution of crystal‐poor rhyolite in the middle Okinawa Trough and its implications for the state of magma chamber

The evolution of crystal‐poor rhyolite in the middle Okinawa Trough and its implications for the state of magma chamber

Vein Formation and Reopening in a Cooling Yet Intermittently Pressurized Hydrothermal System: The Single-Intrusion Tongchang Porphyry Cu Deposit

In-situ trace element and S isotope systematics in pyrite from three porphyry-epithermal prospects, Limnos Island, Greece

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