Silica hydrate preserved with δ18O-rich quartz in high-temperature hydrothermal quartz in the high sulfidation copper-gold deposit at El Indio, Chile

Tanner, Dominique; Henley, Richard W.; Mavrogenes, John; Holden, Peter; Mernagh, Terrence P.

doi:10.1016/j.chemgeo.2014.11.005

Cited by 5 publications

(3 citation statements)

References 53 publications

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“…2) Opal-A cannot survive at magmatic temperatures for more than a few tens of minutes, and will dehydrate and convert to more crystalline forms (Figures 9, 10). At geothermal temperatures (150-250 • C), its preservation is only temporary as it will ultimately convert to more thermodynamically stable phases (Herrington and Wilkinson, 1993;Lynne et al, 2006;Tanner et al, 2015). 3) ORP are common within pumices and glassy particles within laharic sediments from the 1817 eruption of Kawah Ijen.…”

Section: Discussion Primary Observationsmentioning

confidence: 99%

“…Opal itself can contain up to 15 wt% H 2 O (Tanner et al, 2015). Kaolinite contains about 14 wt% H 2 O as do many other clays found in the advanced argillic environment.…”

Section: Speculations On the Connection Between Phreatomagmatic Activmentioning

confidence: 99%

“…Often termed "vuggy quartz" or "vuggy silica" rocks when exposed after uplift and erosion, they presumably originate from protracted water-rock reaction where residual silica remains, with or without associated sulfates such as alunite and barite (Hedenquist and Taran, 2013). Amorphous silica can also form during decompression and quenching of hot hydrous fluids in magmatic and hydrothermal environments at temperatures up to 400 • C (Williamson et al, 2002;Tanner et al, 2015) or during cooling of silica-saturated waters in hot-spring environments (Fournier and Rowe, 1966;Rodgers et al, 2004). Occasionally, acid-altered rocks bearing amorphous silica are expelled directly from the subvolcanic environment during phreatomagmatic eruptions (Christenson and Wood, 1993;Wood, 1994;Christenson et al, 2010;van Hinsberg et al, 2010a;Mayer et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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Opal-A in Glassy Pumice, Acid Alteration, and the 1817 Phreatomagmatic Eruption at Kawah Ijen (Java), Indonesia

et al. 2018

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At Kawah Ijen (Indonesia), vigorous SO 2 and HCl degassing sustains a hyperacid lake (pH ∼0) and intensely alters the subsurface, producing widespread residual silica and advanced argillic alteration products. In 1817, a VEI 2 phreatomagmatic eruption evacuated the lake, depositing a widespread layer of muddy ash fall, and sending lahars down river drainages. We discovered multiple types of opaline silica in juvenile low-silica dacite pumice and in particles within co-erupted laharic sediments. Most spectacular are opal-replaced phenocrysts of plagioclase and pyroxene adjacent to pristine matrix glass and melt inclusions. Opal-bearing pumice has been found at numerous sites, including where post-eruption infiltration of acid water is unlikely. Through detailed analyses of an initial sampling of 1817 eruption products, we find evidence for multiple origins of opaline materials in pumice and laharic sediments. Evidently, magma encountered acid-altered materials in the subsurface and triggered phreatomagmatic eruptions. Syn-eruptive incorporation of opal-alunite clasts, layered opal, and fragment-filled vesicles of opal and glass, all suggest magma-rock interactions in concert with vesiculation, followed by cooling within minutes. Our experiments at magmatic temperature confirm that the opaline materials would show noticeable degradation in time periods longer than a few tens of minutes. Some glassy laharic sedimentary grains are more andesitic than the main pumice type and may represent older volcanic materials that were altered beneath the lake bottom and were forcefully ejected during the 1817 eruption. A post-eruptive origin remains likely for most of the opal-replaced phenocrysts in pumice. Experiments at 25 • C and 100 • C reveal that when fresh pumice is bathed in Kawah Ijen hyperacid fluid for 6 weeks, plagioclase is replaced without altering either matrix glass or melt inclusions. Moreover, lack of evidence for high-temperature annealing of the opal suggests that post-eruption alteration of pumice is more likely than pre-eruption envelopment of Lowenstern et al. Opal in Glassy Pumice euhedral opal-replaced phenocrysts in dacitic melt. At Ijen and elsewhere, the ascent of magma into hydrous acid-altered mineral assemblages (e.g., opal, kaolinite, alunite) could induce rapid dehydration of hydrous minerals and amorphous materials, generating considerable steam and contributing to magmatic-hydrothermal and phreatomagmatic explosions.

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Section: Discussion Primary Observationsmentioning

confidence: 99%

“…Opal itself can contain up to 15 wt% H 2 O (Tanner et al, 2015). Kaolinite contains about 14 wt% H 2 O as do many other clays found in the advanced argillic environment.…”

Section: Speculations On the Connection Between Phreatomagmatic Activmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Opal-A in Glassy Pumice, Acid Alteration, and the 1817 Phreatomagmatic Eruption at Kawah Ijen (Java), Indonesia

et al. 2018

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High-sulfidation veins in the Jiama porphyry system, South Tibet

et al. 2020

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Sulfur isotope and trace element systematics of zoned pyrite crystals from the El Indio Au–Cu–Ag deposit, Chile

Tanner

Henley

Mavrogenes

et al. 2016

Contrib Mineral Petrol

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crystals in high-temperature feeder zones range from −3.19 to 1.88 ‰ (±0.5 ‰), consistent with sublimation directly from a high-temperature magmatic vapor phase. Late pyrite crystals are distinctly more enriched in δ 34 S than early pyrite (δ 34 S = 0.05-4.77 ‰, ±0.5 ‰), as a consequence of deposition from a liquid phase at lower temperatures. It is unclear whether the late pyrite was deposited from a small volume of liquid condensate, or a larger volume of hydrothermal fluid. Both types of pyrite exhibit intracrystalline δ 34 S variation, with a range of up to 3.31 ‰ recorded in an early pyrite crystal and up to 4.48 ‰ in a late pyrite crystal. Variations in δ 34 S pyrite at El Indio did not correspond with changes in trace element geochemistry. The lack of correlation between trace elements and δ 34 S, as well as the abundance of microscale mineral inclusions and vugs in El Indio pyrite indicate that the trace element content of pyrite at El Indio is largely controlled by nanoscale, syndepositional mineral inclusions. Co and Ni were the only elements partitioned within the crystal structure of pyrite. Cu-rich oscillatory zones in early pyrite likely formed by nanoscale inclusions of Cu-rich sulfosalts or chalcopyrite, evidence of deposition from a fluid cyclically saturated in ore metals. This process may be restricted to polymetallic high-sulfidation-like deposits.

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Silica hydrate preserved with δ18O-rich quartz in high-temperature hydrothermal quartz in the high sulfidation copper-gold deposit at El Indio, Chile

Cited by 5 publications

References 53 publications

Opal-A in Glassy Pumice, Acid Alteration, and the 1817 Phreatomagmatic Eruption at Kawah Ijen (Java), Indonesia

Opal-A in Glassy Pumice, Acid Alteration, and the 1817 Phreatomagmatic Eruption at Kawah Ijen (Java), Indonesia

High-sulfidation veins in the Jiama porphyry system, South Tibet

Sulfur isotope and trace element systematics of zoned pyrite crystals from the El Indio Au–Cu–Ag deposit, Chile

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