Experimental data on the speciation of sulfur as a function of oxygen fugacity in basaltic melts

Jugo, Pedro J.; Luth, Robert W.; Richards, Jeremy P.

doi:10.1016/j.gca.2004.07.011

Cited by 261 publications

(119 citation statements)

References 24 publications

(45 reference statements)

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“…Jégo et al (2010) report much lower solubility values (30-240 ppb Au) in S-free dacitic compositions at 4 kbar and 1000˚C, but also show an increase of melt Au contents with fO 2 in a way consistent with the dissolution of gold as both Au 1+ and Au 3+ species. In presence of 5 sulfur, Simon et al (2007) report gold solubility values up to 1100 ppb in Cl-bearing haplogranitic melt at ~NNO (800°C, 1-1.5 kbar) and Jugo et al (2005) give evidence for a solubility on the order of ~500 ppb in anhydrous basaltic melt (1300°C, 10 kbar) in reducing conditions, while a solubility value of ~800 ppb is reported by Bezmen et al (1994) in the Bushveld Complex melt (1300°C, 4 kbar, ~NNO). Those three solubility values are noticeably lower than those obtained by Jégo and Pichavant (2012) in dacitic compositions (1000°C, 4 kbar), which range from 1200 to 4250 ppb Au at ~NNO-1 and from 865 to 2400 ppb at ~NNO+1.5, depending mainly on the melt S content.…”

Section: Introductionmentioning

confidence: 94%

“…The behavior of sulfur in silicate melts is known to be highly complex, especially because of the change of speciation from reduced sulfur (sulfide, S 2-) to oxidized sulfur (sulfate, SO 4 2-) which occurs over a relatively narrow fO 2 range, typically of ~2-3 fO 2 log units (e.g., Jugo et al, 2005;Baker and Moretti, 2011;Yang, 2012). A large number of studies --among others, Jugo (2009) and Botcharnikov et al (2011), showed that sulfur solubility increases rapidly with fO 2 when fO 2 is at the sulfide/sulfate transition, i.e.…”

Section: Speciation and Dissolution Of Sulfurmentioning

confidence: 99%

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Is gold solubility subject to pressure variations in ascending arc magmas?

Jégo

Nakamura

Kimura

et al. 2016

Geochimica et Cosmochimica Acta

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Magmas play a key role in the genesis of epithermal and porphyry ore deposits, notably by providing the bulk of ore metals to the hydrothermal fluid phase. It has been long shown that the formation of major deposits requires a multi-stage process, including the concentration of metals in silicate melts at depth and their transfer into the exsolved ore fluid in more superficial environments. Both aspects have been intensively studied for most of noble metals in subsurface conditions, whereas the effect of pressure on the concentration (i.e., solubility) of those metals in magmas ascending from the sublithospheric mantle to the shallow arc crust has been quite neglected. Here, we present new experimental data aiming to constrain the processes of gold (Au) dissolution in subduction-linked magmas along a range of depth. We have conducted hydrous melting experiments on two dacitic/adakitic magmas at 0.9 and 1.4GPa and ~1000°C in an end-loaded piston cylinder apparatus, under fO 2 conditions close to NNO as measured by solid Co-Pd-O sensors. Experimental charges were carried out in pure Au containers, the latter serving as the source of gold, in presence of variable amounts of H 2 O and, for half of the charges, with elemental sulfur (S) so as to reach sulfide saturation. Au concentrations in melt quenched to glass were determined by LA-ICPMS. When compared to previous data obtained at lower pressures and variable redox conditions, our results show that in both S-free and sulfide-saturated systems pressure has no direct, detectable effect on melt Au solubility. Nevertheless, pressure has a strong, negative effect on sulfur solubility. Since gold dissolution is closely related to the behaviour of sulfur in reducing and moderately oxidizing conditions, pressure has therefore a significant but indirect effect on Au solubility.The present study confirms that Au dissolution is mainly controlled by fO 2 in S-free melts and 3 by a complex interplay of fO 2 and melt S 2-concentration in sulfide-saturated melts, at given temperature. In addition, we propose that the transition from sulfide (S 2-) to sulfate (S 6+ ) species in melt is shifted towards more oxidizing conditions when pressure and the degree of melt polymerization increase. If this is true, this may have important consequences during mantle melting and magma ascent. In particular, if mantle melting occurred in moderately oxidizing conditions, a small degree of partial melting would allow the primary melts to become Au-enriched but the relatively high pressure would move the sulfide-sulfate transition to more oxidizing conditions, making the primary melts saturated with sulfide phases that would sequester gold from the melt. During magma ascent, the decreasing pressure would favour the destabilization of sulfides and the release of gold to the silicate melt. However, at shallow levels, decreasing pressure, magma evolution, and varying redox conditions would be continuously competing to concentrate or fractionate gold.

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Section: Introductionmentioning

confidence: 94%

Section: Speciation and Dissolution Of Sulfurmentioning

confidence: 99%

Is gold solubility subject to pressure variations in ascending arc magmas?

Jégo

Nakamura

Kimura

et al. 2016

Geochimica et Cosmochimica Acta

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“…7A). This is accomplished by precisely measuring the sulfur Kα peak position and comparing it to those for pure sulfate and sulfide (Carroll and Rutherford, 1988;Nilsson and Peach, 1993;Wallace and Carmichael, 1994;Metrich and Clocchiatti, 1996;Matthews et al, 1999a;Jugo et al, 2005). These studies permitted definition of the relationship between magmatic oxygen fugacity and the %S 6+ in the glass, providing an independent means of assessing magmatic oxygen fugacity (Fig.…”

Section: Experimental Confirmation Of Igneous Anhydrite Stabilitymentioning

confidence: 99%

Primary igneous anhydrite: Progress since its recognition in the 1982 El Chichón trachyandesite

Luhr

2008

Journal of Volcanology and Geothermal Research

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“…The Andersen et al (1993;QUILF program) 2-oxide oxybarometer usually shows more reducing values than those calculated with the Sauerzapf et al (2008) oxybarometer (0.8-1.2 log units more reduced considering that ΔNNO ≈ ΔFMQ -0.7; Jugo et al, 2005) except for dolerites (Table T2). Redox estimates indicate highly oxidizing conditions for granoblastic basalts, gabbroic lithologies, and albitites with ΔNNO values ranging from +1.97 to +2.66 (according to Sauerzapf et al, 2008) and ΔFMQ values ranging from +1.49 to +2.57 (according to Andersen et al, 1993).…”

Section: Redox Conditionsmentioning

confidence: 78%

Data report: lithologic diversity, mineral composition, and temperature and redox conditions in ODP/IODP Hole 1256D-a study of sand and gravels recovered during IODP Expedition 335

Abily¹,

Python²

2016

Proceedings of the IODP

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This data report presents an uncommon study of fine drill cuttings (sand and gravels) recovered from hole maintenance operations in Ocean Drilling Program/Integrated Ocean Drilling Program (IODP) Hole 1256D (East Pacific Rise) during Expedition 335. Drill cuttings represent an integrated sampling of the entire hole and offer the opportunity to study the petrological characteristics of the various lithologies making up the upper oceanic crust. We selected the fine-grained fraction of cuttings coming from 12 pipe deployments (runs) and conducted microscopic observations (mineralogy and texture), image processing, electron microprobe analyses (~4400 analyses), and oxythermobarometry calculations on 16-25 grain-mount thin sections.This study shows that drill cuttings sample all of the lithologies in the hole (glass, aphyric and phyric basalts, dolerite, gabbro, diorite, gabbronorite, albitite, and three kinds of granoblastic basalt) but overrepresent non-or poorly recovered materials like albitites and granoblastic basalts. Drill cuttings are thus a good alternative to study these "rare" lithologies. Based on the composition of the main minerals and the oxythermobarometry calculations, two major lithologic groups were defined in the cuttings: a basaltic lavas-dolerites group and a gabbroic lithologies-granoblastic basalts group. Basaltic lavas (glass and basalts) and dolerites are characterized by Mg-augites rich in Al 2 O 3 , Cr 2 O 3 , and TiO 2 ; MgO-rich plagioclases with a mean composition of An 60-70 ; and titanomagnetites. Their Fe-Ti oxides (magnetite and ilmenite) indicate relatively reducing conditions (ΔNNO = -1.26 to -0.80), and clinopyroxenes in dolerites give a mean equilibrium temperature of 1017°C. Gabbroic lithologies and granoblastic basalts are characterized by Ca-rich clinopyroxenes (augites and diopsides) depleted in Al 2 O 3 , Cr 2 O 3 , and TiO 2 ; MgO-poor plagioclases with a mean composition of An 50-60 ; and Ti-poor magnetites. Oxybarometers give oxidizing (ΔNNO = -0.08 to +0.58) to very oxidizing (ΔNNO = +1.97 to +2.38) conditions for these lithologies, and their pyroxenes indicate high (909°C-985°C) to relatively high (783°C-888°C) mean temperatures according to the thermometer considered. Albitites show equivalent mineral compositions and temperature and redox conditions to gabbroic lithologies and granoblastic basalts. They are, however, characterized by albitic plagioclases (An 0-20 ) and usually display slightly lower temperatures (780°C) and higher ΔNNO values (+2

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Experimental data on the speciation of sulfur as a function of oxygen fugacity in basaltic melts

Cited by 261 publications

References 24 publications

Is gold solubility subject to pressure variations in ascending arc magmas?

Is gold solubility subject to pressure variations in ascending arc magmas?

Primary igneous anhydrite: Progress since its recognition in the 1982 El Chichón trachyandesite

Data report: lithologic diversity, mineral composition, and temperature and redox conditions in ODP/IODP Hole 1256D-a study of sand and gravels recovered during IODP Expedition 335

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