Solubility and fluid-melt partitioning of Cl in hydrous phonolitic melts

Signorelli, S.; Carroll, M.

doi:10.1016/s0016-7037(00)00386-0

Cited by 131 publications

(76 citation statements)

References 38 publications

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“…A similar negative correlation of melt Cl contents with pressure has been observed in other experimental studies of evolved (rhyolitic, phonolitic) melt compositions saturated with aqueous fluid+hypersaline brine phases (e.g. Shinohara et al 1989;MØtrich and Rutherford 1992;Signorelli and Carroll 2000).…”

Section: Variation Of CL Solubility In Experimental Glassessupporting

confidence: 85%

Experimental constraints on the origin of chlorine emissions at the Soufrière Hills volcano, Montserrat

Signorelli

Carroll

2001

Bull Volcanol

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Experimental study of Cl solubility in a rhyolitic melt composition corresponding to the phenocryst-free matrix of the recently erupted Soufrire Hills andesite provides insights into the origin of Cl emitted to the atmosphere during the eruption. The experiments were done at 25±250 MPa, 860±890 C, and they involved equilibration of the estimated matrix composition [~71 wt.% SiO 2 , molar (Na 2 O+ K 2 O)/Al 2 O 3~0 .6] with a Cl-rich aqueous fluid or aqueous fluid+hydrosaline brine. The Cl concentrations in glasses from the experimental run products (0.48±0.68 wt.% Cl) are significantly higher than those observed in natural matrix glasses (~0.20 wt.% Cl) and melt inclusions (0.300.07 wt.% Cl). These results indicate that if the pre-eruptive Montserrat magma was vapour saturated, the vapour phase would have been Cl poor and there was not a co-existing hydrosaline brine. This interpretation, based on Cl solubility data, is supported by the observed coincidence between remote sensing measurements of Cl emissions (as HCl) and petrological estimates of Cl emissions based on the volume of magma extruded and Cl contents of melt inclusions and matrix glasses (with correction for groundmass crystallization during ascent). The Cl emissions during the Soufrire Hills eruption are thus proposed to simply reflect syn-eruptive degassing of magma during ascent.

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Section: Variation Of CL Solubility In Experimental Glassessupporting

confidence: 85%

Experimental constraints on the origin of chlorine emissions at the Soufrière Hills volcano, Montserrat

Signorelli

Carroll

2001

Bull Volcanol

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“…Experimental results show that Cl solubility has negative pressure dependence, thus implying that if magma coexists with Cl-bearing gas, Cl dissolves into the melt during magma decompression (Signorelli and Carroll 2000;Carroll 2005 and references therein). The effects of negative pressure-dependence of Cl solubility are however not significant in basaltic melts saturated with hydrosaline solutions, for P ranging between 0.1 and 200 MPa (Webster et al 1999;Bhalla et al 2002).…”

Section: The Role Of Volatiles Migrationmentioning

confidence: 99%

“…Many authors have experimentally derived fluid/melt D Cl for mafic melts at pressure of our interest (200 MPa) providing a wide range of values (0.9-18; Webster et al 1999;Signorelli and Carroll 2000;Wehrmann 2005;Alletti et al 2006;Bhalla et al 2002). For mass balance calculations we chose an averaged value of fluid/melt D Cl =10, similar to what was found by Signorelli and Carroll (2000) and , from which by using the average Cl concentration in CAL 1 glass we…”

Section: Appendixmentioning

confidence: 99%

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Volatile-induced magma differentiation in the plumbing system of Mt. Etna volcano (Italy): evidence from glass in tephra of the 2001 eruption

2007

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Mount Etna volcano was shaken during the summer 2001 by one of the most singular eruptive episodes of the last centuries. For about 3 weeks, several eruptive fractures developed, emitting lava flows and tephra that significantly modified the landscape of the southern flank of the volcano. This event stimulated the attention of the scientific community especially for the simultaneous emission of petrologically distinct magmas, recognized as coming from different segments of the plumbing system. A stratigraphically controlled sampling of tephra layers was performed at the most active vents of the eruption, in particular at the 2,100 m (CAL) and at the 2,550 m (LAG) scoria cones. Detailed scanning electron microscope and energy dispersive x-ray spectrometer (SEM-EDS) analyses performed on glasses found in tephra and comparison with lava whole rock compositions indicate an anomalous increase in Ti, Fe, P, and particularly of K and Cl in the upper layers of the LAG sequence. Mass balance and thermodynamic calculations have shown that this enrichment cannot be accounted for by "classical" differentiation processes, such as crystal fractionation and magma mixing. The analysis of petrological features of the magmas involved in the event, integrated with the volcanological evolution, has evidenced the role played by volatiles in controlling the magmatic evolution within the crustal portion of the plumbing system. Volatiles, constituted of H 2 O, CO 2 , and Cl-complexes, originated from a deeply seated magma body (DBM). Their upward migration occurred through a fracture network possibly developed by the seismic swarms during the period preceding the event. In the upper portion of the plumbing system, a shallower residing magma body (ABT) had chemical and physical conditions to receive migrating volatiles, which hence dissolved the mobilized elements producing the observed selective enrichment. This volatile-induced differentiation involved exclusively the lowest erupted portion of the ABT magma due to the low velocity of volatiles diffusion within a crystallizing magma body and/or to the short time between volatiles migration and the onset of the eruption. Furthermore, the increased amount of volatiles in this level of the chamber strongly affected the eruptive behavior. In fact, the emission of these products at the LAG vent, towards the end of the eruption, modified the eruptive style from classical strombolian to strongly explosive.

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“…Therefore, in view of clear evidence for higher SO 2 contents in volatiles derived from alkaline as opposed to calc-alkaline magmas (Bailey and Hampton 1990;Hedenquist 1995), and enhanced chlorine solubilities in alkali-rich, silica-poor magmas (e.g. phonolite; Signorelli and Carroll 2000), the paucity of advanced argillic lithocaps and high-sulphidation deposits in alkaline igneous provinces does not appear to reflect a prevalence of unsuitable volatile compositions. The profusion of magmatically derived SO 2 is further emphasised by the greater abundance of anhydrite and, locally, even celestite in the lowsulphidation epithermal deposits of alkaline parentage (e.g.…”

Section: Traditional Deposit Typesmentioning

confidence: 99%

Some metallogenic features of gold and copper deposits related to alkaline rocks and consequences for exploration

Sillitoe¹

2002

Mineralium Deposita

128

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Porphyry copper-gold, skarn copper-gold, sediment-hosted (Carlin-style) gold, breccia pipe, lowsulphidation epithermal gold, pluton-related (mesothermal or orogenic) gold vein and volcanogenic massive sulphide deposits associated with alkaline rocks are commonly broadly similar to those hosted by their calcalkaline counterparts. In contrast, porphyry molybdenum-gold deposits are confined to alkaline igneous centres. Alkaline suites are notably deficient in highsulphidation epithermal gold deposits and even in the advanced argillic lithocaps which host them. This is surprising, given that the required oxidised sulphur species are seemingly more abundant than in calc-alkaline igneous centres. Highly efficient buffering of acidic fluid by metasomatised alkaline rocks may offer a viable explanation. All types of intrusion-related zinc deposits also appear to be poorly developed in alkaline provinces.

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Solubility and fluid-melt partitioning of Cl in hydrous phonolitic melts

Cited by 131 publications

References 38 publications

Experimental constraints on the origin of chlorine emissions at the Soufrière Hills volcano, Montserrat

Experimental constraints on the origin of chlorine emissions at the Soufrière Hills volcano, Montserrat

Volatile-induced magma differentiation in the plumbing system of Mt. Etna volcano (Italy): evidence from glass in tephra of the 2001 eruption

Some metallogenic features of gold and copper deposits related to alkaline rocks and consequences for exploration

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