Porphyry copper deposits

Hunt, John Paul

doi:10.1144/gsl.sp.1977.007.01.12

Cited by 34 publications

(3 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The behavior of volatile species in trans‐crustal magmatic mush systems also has implications for hydrothermal ore formation associated with arc volcanoes. Porphyry copper deposits are widely viewed as giant sulfur anomalies [ Hunt , ] and are therefore likely to be related in origin to the excess sulfur phenomenon of arc volcanoes [ Wallace , ]. Similarly, most porphyry copper deposits contain fluid inclusions of high salinity and metal content [ Bodnar et al ., ] testifying to the importance of chlorine‐rich fluids in mineralization.…”

Section: Discussionmentioning

confidence: 99%

Crustal‐scale degassing due to magma system destabilization and magma‐gas decoupling at Soufrière Hills Volcano, Montserrat

Christopher

Blundy

Cashman

et al. 2015

Geochem Geophys Geosyst

128

107

View full text Add to dashboard Cite

Activity since 1995 at Soufrière Hills Volcano (SHV), Montserrat has alternated between andesite lava extrusion and quiescence, which are well correlated with seismicity and ground deformation cycles. Large variations in SO 2 flux do not correlate with these alternations, but high and low HCl/SO 2 characterize lava dome extrusion and quiescent periods respectively. Since lava extrusion ceased (February 2010) steady SO 2 emissions have continued at an average rate of 374 tonnes/day (6 140 t/d), and incandescent fumaroles (temperatures up to 610 o C) on the dome have not changed position or cooled. Occasional short bursts (over several hours) of higher ( 10x) SO 2 flux have been accompanied by swarms of volcano-tectonic earthquakes. Strain data from these bursts indicate activation of the magma system to depths up to 10 km. SO 2 emissions since 1995 greatly exceed the amounts that could be derived from 1.1 km 3 of erupted andesite, and indicating extensive partitioning of sulfur into a vapour phase, as well as efficient decoupling and outgassing of sulfur-rich gases from the magma. These observations are consistent with a vertically extensive, crustal magmatic mush beneath SHV. Three states of the magmatic system are postulated to control degassing. During dormant periods (10 3 to 10 4 years) magmatic vapour and melts separate as layers from the mush and decouple from each other. In periods of unrest (years) without eruption, melt and fluid layers become unstable, ascend and can amalgamate. Major destabilization of the mush system leads to eruption, characterized by magma mixing and release of volatiles with different ages, compositions and sources.

show abstract

Section: Discussionmentioning

confidence: 99%

Crustal‐scale degassing due to magma system destabilization and magma‐gas decoupling at Soufrière Hills Volcano, Montserrat

Christopher

Blundy

Cashman

et al. 2015

Geochem Geophys Geosyst

128

107

View full text Add to dashboard Cite

show abstract

“…However, it is unlikely that only a single magma is involved. Famously, porphyry deposits have been referred to as sulfur anomalies (Hunt, 1977) or sulfur deposits with associated metals (Blundy et al, 2015), yet pre-eruptive sulfur concentrations in many dacitic-rhyolitic arc melts record low sulfur (<200ppm) (Hattori and Keith, 2001;Blundy et al, 2015 and references therein). There is also a well-established decoupling of S and Cl over a range of P-T-ƒO2 conditions reported in both natural and experimental studies (Lesne, et al, 2011;Wallace, P., 2005).…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Evolution of chalcophile elements in the magmas of the Bonin Islands

et al. 2019

View full text Add to dashboard Cite

show abstract

“…Gustafson (1979) noted that ''sulphur is genetically, if not economically, a more important factor than the metals [in formation of porphyry copper deposits]... Hunt (1977) pointed out, porphyry copper deposits are really large sulphur anomalies with lower Cu/S ratios than ordinary crustal rocks.'' Magmatic sulfur enrichment may be the critical process that ultimately leads to porphyry-type ore formation; copper and other metals may ''just go along for the ride'' and show less relative enrichment in the final ore deposit than does sulfur .…”

Section: Contributions Of Sulfur and Metals From Mafic Magmasmentioning

confidence: 99%

Contributions from mafic alkaline magmas to the Bingham porphyry Cu-Au-Mo deposit, Utah, USA

Maughan

Keith

Christiansen

et al. 2002

Mineralium Deposita

121

View full text Add to dashboard Cite

The Bingham porphyry Cu-Au-Mo deposit, Utah, may only be world-class because of substantial contributions of sulfur and metals from mafic alkaline magma to an otherwise unremarkable calc-alkaline system. Volcanic mafic alkaline rocks in the district are enriched in Cr, Ni, and Ba as well as Cu, Au, platinum group elements (PGE), and S. The bulk of the volcanic section that is co-magmatic with ore-related porphyries is dacitic to trachytic in composition, but has inherited the geochemical signature of high Cr, Ni, and Ba from magma mixing with the mafic alkaline rocks. The volcanic section that most closely correlates in time with ore-related porphyries is very heterogeneous containing clasts of scoriaceous latite, latitic, and minette, and flows of melanephelinite, shoshonite, and olivine latite in addition to volumetrically dominant dacite/trachyte. Bingham ore-related porphyries show ample evidence of prior mixing with mafic alkaline magmas. Intrusive porphyries that have not been previously well-studied have several chemical and mineralogical indications of magma mixing. These ''mixed'' lithologies include the hybrid quartz monzonite porphyry, biotite porphyry, and minette dikes. Even some of the more silicic latite and monzonite porphyries retain high Cr and Ba contents indicative of mixing and contain trace amounts of sapphire (<1 mm). The heterogeneous block and ash flow deposits also contain sapphire and are permissively correlated with the intrusions based on chemical, mineralogical, and isotopic data. Magma mixing calculations suggest about 10% of the monzonitic/latitic orerelated magma may have been derived from mafic alkaline magma similar to the melanephelinite. If the original S content of the mafic magma was about 2,000-4,000 ppm, comparable with similar magmas, then the mafic magma may have been responsible for contributing more than half of the S and a significant portion of the Cu, Au, and PGE in the Bingham deposit.

show abstract

Porphyry copper deposits

Cited by 34 publications

References 0 publications

Crustal‐scale degassing due to magma system destabilization and magma‐gas decoupling at Soufrière Hills Volcano, Montserrat

Crustal‐scale degassing due to magma system destabilization and magma‐gas decoupling at Soufrière Hills Volcano, Montserrat

Evolution of chalcophile elements in the magmas of the Bonin Islands

Contributions from mafic alkaline magmas to the Bingham porphyry Cu-Au-Mo deposit, Utah, USA

Contact Info

Product

Resources

About