Open-system dynamics and mixing in magma mushes

Bergantz, George W.; Schleicher, J.; Burgisser, Alain

doi:10.1038/ngeo2534

Cited by 168 publications

(143 citation statements)

References 28 publications

Supporting

Mentioning

134

Contrasting

Order By: Relevance

“…That is, the lava only experienced the recharge event that led to its removal from the reservoir. Our inference is consistent with simulations that show that the effects from recharge are likely to only be recorded in the crystal-rich part of the reservoir (19). The fact that older zircon rims are preserved throughout the magmatic history suggests that they were armored by (i) modal mineral phases or (ii) younger, subsequently resorbed rims, or that the melt-present part of the magma reservoir waxed and waned, permitting incorporation of some crystals from intermittently solidified margins before eruption (Fig.…”

Section: Significancesupporting

confidence: 78%

“…That intrusive magma volumes outweigh their extrusive counterparts is sufficient reason to assume that both may record different aspects of the reservoir's history (15)(16)(17)(18)(19); this is because melt-dominated volcanic rocks may only represent a volumetrically minor part of the magma reservoir, whereas plutonic rocks represent conditions in the crystaldominated bulk of the magma reservoir (18). To provide a physical context for our interpretive scheme, we point to simulations of Bergantz et al (19) that show that the full extent of thermal excursions caused by recharge is only recorded in the immediately adjacent crystal-rich portions of the reservoir.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Warm storage for arc magmas

Barboni

Boehnke

Schmitt

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

100

View full text Add to dashboard Cite

Felsic magmatic systems represent the vast majority of volcanic activity that poses a threat to human life. The tempo and magnitude of these eruptions depends on the physical conditions under which magmas are retained within the crust. Recently the case has been made that volcanic reservoirs are rarely molten and only capable of eruption for durations as brief as 1,000 years following magma recharge. If the "cold storage" model is generally applicable, then geophysical detection of melt beneath volcanoes is likely a sign of imminent eruption. However, some arc volcanic centers have been active for tens of thousands of years and show evidence for the continual presence of melt. To address this seeming paradox, zircon geochronology and geochemistry from both the frozen lava and the cogenetic enclaves they host from the Soufrière Volcanic Center (SVC), a long-lived volcanic complex in the Lesser Antilles arc, were integrated to track the preeruptive thermal and chemical history of the magma reservoir. Our results show that the SVC reservoir was likely eruptible for periods of several tens of thousands of years or more with punctuated eruptions during these periods. These conclusions are consistent with results from other arc volcanic reservoirs and suggest that arc magmas are generally stored warm. Thus, the presence of intracrustal melt alone is insufficient as an indicator of imminent eruption, but instead represents the normal state of magma storage underneath dormant volcanoes.volcano | eruption | arc magma | zircon D etermining the timescale of magma storage and remobilization in the upper crust is key to understanding the tempo and magnitude of volcanic eruptions (1-13). Whether a volcano can erupt is controlled by the recharge rate to the magma reservoir (13) (reservoir in this context refers to the portion of the igneous complex that is potentially eruptible), which in turn determines the duration of the "eruption window" [generally defined as the rheological state during which the subvolcanic reservoir is below ∼60% crystals and hence capable of eruption (4)]. However, estimates for how long this eruption window remains open vary over four orders of magnitude; this suggests either profound problems in assumptions underlying one or more of these estimates or a continuum of physical mechanisms that resist formulation of a unified model for the state of magma reservoirs before eruption (1-13). The preservation of sharp compositional gradients in plagioclase phenocrysts, assumed to have crystallized >10 ka before eruption, has recently been interpreted to indicate that arc volcanic reservoirs characteristically remain in "cold storage" at temperatures below the eruption window, possibly below the solidus, and thus only capable of erupting during brief recharge events (<10 ka) (1). In contrast, zircon dating and heat budget considerations are difficult to reconcile with this scenario; instead, they are consistent with continuously partially molten reservoirs capable of erupting (i.e., with melt portion ≥40%) ov...

show abstract

Section: Significancesupporting

confidence: 78%

mentioning

confidence: 99%

Warm storage for arc magmas

Barboni

Boehnke

Schmitt

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

100

View full text Add to dashboard Cite

show abstract

“…8a, b, d) and stepped (Fig. 8c) profiles cannot be conclusively assessed, although it could be related to different mixing regimes within tur- bulent flow fields (e.g., Misiti et al, 2009;Bergantz et al, 2015;Schleicher et al, 2016). The prevalent occurrence of multi-banded and the anomalous profiles among PP crystals may suggest a higher frequency of proto-lp magma injection(s) associated with slightly different efficiency of the turbulent mixing shortly before eruption.…”

Section: A Working Model For Crystal Zoning and Mixing Dynamicsmentioning

confidence: 97%

Rapid mixing and short storage timescale in the magma dynamics of a steady-state volcano

Petrone

Braschi

Francalanci

et al. 2018

Earth and Planetary Science Letters

View full text Add to dashboard Cite

Steady-state volcanic activity implies equilibrium between the rate of magma replenishment and eruption of compositionally homogeneous magmas, lasting for tens to thousands of years in an open conduit system. The Present-day activity of Stromboli volcano (Aeolian Islands, Southern Italy) has long been recognised as typical of a steady-state volcano, with a shallow magmatic reservoir (highly porphyritic or hp-magma) continuously refilled by more mafic magma (with low phenocryst content or lp-magma) at a constant rate and accompanied by mixing, crystallisation and eruption. Our aim is to clarify the timescale and dynamics of the plumbing system at the establishment of the Present-day steady-state activity (<1.2 ka) to pinpoint the onset of the steady-state regime. We investigated the Post-Pizzo (PP) pyroclastic sequence (∼1.7-1.5 ka) and one of the Early Paroxysms (EP) of the Present-day activity, focusing on the clinopyroxene population. Whole rock and clinopyroxene compositional variation among the PP and EP magmas is consistent with the time progression of the Stromboli system towards more mafic and lower 87 Sr/ 86 Sr compositions, pointing to the chemical and isotopic signature of the Present-day activity. Clinopyroxenes from both PP and EP record a complex history with compositional zoning that reflects growth in three different melt domains: a high-Mg# proto-lp recharging magma, a low-Mg# proto-hp resident magma, and a transient intermediate-Mg# magma. These are the result of complex turbulent flow fields and mixing regimes produced by repeated injections of the proto-lp magma in the shallow proto-hp magma reservoir. During the PP period the magmatic system was already able to regain the pre-input proto-hp composition, gradually changing toward a less evolved signature after the injection(s) of the more mafic proto-lp magma, owing to efficient (days to a few years) stirring and melt homogenisation (i.e., homogenisation time < residence time).Based upon Fe-Mg diffusion in clinopyroxene the total residence time during PP and EP periods, from the arrival of the mafic magma in the shallow system until the eruption, ranges from 1 to ∼50 years. Longer residence times (up to 150 years) have been recorded in the initial phase of the PP sequence, possibly testifying to the transition from a closed-to the open-conduit, steady-state regime of the Present-day activity. Some clinopyroxenes from the PP recorded the mafic triggering event of the feeding proto-lp magma occurring within few months to a few days before eruption. Remarkably, other clinopyroxene portions crystallised and captured the rapid timescales (a few days) of the on-going mixing and homogenisation process between the proto-lp and the proto-hp magmas leading to the eruption. The modelling of clinopyroxene zoning events at Stromboli provides evidence for growth and storage in three different melt domains, and sets robust constraints on their residence time from lp-magma recharge(s) to eruption, along with the timescales of melt homogenisation and triggerin...

show abstract

“…Moreover, the HPRD lavas include abundant mafic enclaves with a texture of acicular amphibole and plagioclase that attests to quench crystallisation upon injection in the cooler (rhyo)dacitic host (Bacon 1986;Vanderkluysen et al 2005a;Braschi et al 2014) and hence supports mafic recharge as a likely eruption trigger (Bachmann et al 2012;Braschi et al 2012Braschi et al , 2014. Magma mingling and disaggregation of the enclaves leads to crystal transfer from the enclaves to the (rhyo)dacitic host and vice versa and can thus account for the complex zoning patterns recorded by HPRD crystals as well as similar, often bimodal plagioclase distributions in the enclaves and hosts (Humphreys et al 2009;Braschi et al 2014;Bergantz et al 2015). Given their textural and compositional similarity, it is likely that all HPRD units originated from a shallow crystal-rich mush system that was reactivated by mafic recharge and that this process was not restricted solely to the youngest PFI domes on Nisyros.…”

Section: Discussionmentioning

confidence: 99%

“…Such hybrid andesites are believed to tap shallow, crystalrich mush systems that have stalled in the upper crust due to decompression-induced degassing and rapid crystallisation (e.g., Blundy and Cashman 2005;Annen et al 2006;Bachmann and Huber 2016). Due to their high viscosity, these mush systems spend the majority of the time close to the solidus in an uneruptible state, but can be rapidly remobilised and erupted in response to recharge by a volatilerich mafic magma (e.g., Cooper and Kent 2014;Parmigiani et al 2014;Bergantz et al 2015). Field relationships and textures of the HPRD (rhyo)dacites are very similar to these hybrid, reactivated mushes.…”

Section: Discussionmentioning

confidence: 99%

A mineral and cumulate perspective to magma differentiation at Nisyros volcano, Aegean arc

Klaver

Matveev

Berndt

et al. 2017

Contrib Mineral Petrol

View full text Add to dashboard Cite

and these appear to be derived from the lower crust (0.5-0.8 GPa). The suppressed stability of plagioclase and early saturation of amphibole in these cumulates are indicative of high-pressure crystallisation from primitive hydrous melts (≥ 3 wt% H 2 O). Clinopyroxene in these cumulates has Al 2 O 3 contents up to 9 wt% due to the absence of crystallising plagioclase, and is subsequently consumed in a peritectic reaction to form primitive, Al-rich amphibole (Mg# > 73, 12-15 wt% Al 2 O 3 ). The composition of these peritectic amphiboles is distinct from trace element-enriched interstitial amphibole in shallower cumulates. Phenocryst compositions and assemblages in both suites differ markedly from the cumulates. Phenocrysts, therefore, reflect shallow crystallisation and do not record magma differentiation in the deep arc crust.

show abstract

Open-system dynamics and mixing in magma mushes

Cited by 168 publications

References 28 publications

Warm storage for arc magmas

Warm storage for arc magmas

Rapid mixing and short storage timescale in the magma dynamics of a steady-state volcano

A mineral and cumulate perspective to magma differentiation at Nisyros volcano, Aegean arc

Contact Info

Product

Resources

About