Crystal recycling in the steady-state system of the active Stromboli volcano: a 2.5-ka story inferred from in situ Sr-isotope and trace element data

Francalanci, L.; Avanzinelli, Riccardo; Nardini, I.; Tiepolo, Massimo; Davidson, Jon P.; Vannucci, R.

doi:10.1007/s00410-011-0661-0

Cited by 59 publications

(35 citation statements)

References 56 publications

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“…These values complete, and extend toward more radiogenic compositions the range reported for HP magmas erupted during the last 100 years (0.70626-0.70615 in Francalanci et al 2004Francalanci et al , 1999. The most radiogenic value (0.706598), determined for our oldest (third to seventh AD) lava sample, significantly exceeds that acquired for resorbed cores of plagioclase and pyroxene in recent HP scoria (up to 0.706346) and attains the highest, single, measurement for a plagioclase core reported in Francalanci et al (2011). This value almost matches the lower values (0.706625) derived for Neostromboli products by Tommasini et al (2007).…”

Section: Hp Magmasmentioning

confidence: 45%

“…5). Based on this evidence, we can also argue that the entrainment of crystal mushes, recycled minerals inherited from the previous activity and/or contamination by host rocks, as documented by Francalanci et al (2011) in the shallow plumbing system, are not capable of modifying appreciably the chemical and isotopic bulk compositions of HP magmas.…”

Section: Considerations About the Processes Of Magma Differentiationmentioning

confidence: 93%

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Geochemical heterogeneities and dynamics of magmas within the plumbing system of a persistently active volcano: evidence from Stromboli

2011

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We report here the most complete dataset for major and trace elements, as well as Sr isotopic compositions, of magmas erupted by Stromboli since the onset of present-day activity 1,800 years ago. Our data relate to both porphyritic scoria and lava originating in the uppermost parts of the feeding system, plus crystal-poor pumice produced by paroxysmal explosive eruption of deep-seated, fast ascending, magma. The geochemical variations recorded by Stromboli's products allow us to identify changes in magma dynamics affecting the entire plumbing system. Deep-seated magmas vary in composition between two end-members having different key ratios in strongly incompatible trace elements and Sr isotopes. These features may be ascribed to mantle source processes (fluid/melt enrichment, variable degrees of melting) and occasional contamination by deep, mafic, cumulates. Temporal trends reveal three phases during which magmas with distinct geochemical signatures were erupted. The first phase occurred between the third and fourteenth centuries AD and was characterised by the eruption of evolved magmas sharing geochemical and Sr isotopic compositions similar to those of earlier periods of activity (<12 ka-Neostromboli and San Bartolo). The second phase, which began in the sixteenth century and lasted until the first half of the twentieth century, produced more primitive, less radiogenic, magmas with the lowest Ba/La and Rb/ Th ratios of our dataset. The last phase is ongoing and is marked by a magma having the lowest Sr isotopic composition and highest Rb/Th ratio of the dataset. While this new magma can be clearly identified in the pumice erupted during the last two paroxysmal eruptions of 2003 and 2007, shallow degassed magma extruded during this time span records significant geochemical and isotopic heterogeneities. We thus suggest that the shallow reservoir has been only partially homogenised by this new magma influx. We conclude that compositional variations within the shallow magma system of a persistently active volcano provide only a biassed signal of ongoing geochemical changes induced by deep magma refilling. We argue that source changes can only be identified by interpreting the geochemistry of pumice, because it reliably represents magma transferred directly from deep portions of the plumbing system to the surface.

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Section: Hp Magmasmentioning

confidence: 45%

Section: Considerations About the Processes Of Magma Differentiationmentioning

confidence: 93%

Geochemical heterogeneities and dynamics of magmas within the plumbing system of a persistently active volcano: evidence from Stromboli

2011

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“…5, 9). This may indicate the passage of the proto-lp magma through a pre-existing crystal mush while ascending, with remobilisation and resorption of some older and possibly low-Mg# crystals (from previous more evolved magma), in agreement with antecrysts recycling in the Present-day activity (Francalanci et al, 2005(Francalanci et al, , 2012.…”

Section: A Working Model For Crystal Zoning and Mixing Dynamicsmentioning

confidence: 68%

“…The compositional uniformity of the whole magmatic system with time contrasts with chemical and isotopic heterogeneities at the mineral scale testified by complex textures in plagioclase and clinopyroxene. This heterogeneity is originated during the intricate processes of lp-hp magma mixing and antecryst recycling from a ∼2.4 ka old crystal mush (Francalanci et al, 2005(Francalanci et al, , 2012Bragagni et al, 2014). The erupted magmas of Epoch 6 reached the more evolved shoshonite composition only at the base of the Post-Pizzo sequence.…”

Section: Discussionmentioning

confidence: 99%

“…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. The prevalence of subgroup A2 clinopyroxenes, preserving a core of possible antecrystic origin, in the EP period may depend on the occurrence of a cumulated crystal mush formed in the plumbing system during the entire Epoch 6 (Francalanci et al, 2005(Francalanci et al, , 2012. Finally, other clinopyroxenes rims record the mafic triggering event associated with the initial phase of homogenisation (Figs.…”

Section: A Working Model For Crystal Zoning and Mixing Dynamicsmentioning

confidence: 99%

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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

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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...

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Exploring the mineralogical heterogeneities of the Louisville Seamount Trail

Dorais

2015

Geochem Geophys Geosyst

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Diopside phenocrysts of the Louisville Seamount Trail show an increase in Ti, Al, and Na with decreasing Mg/(Mg + Fe) as is typical for clinopyroxene in alkalic basalts. Chondrite‐normalized REE patterns of calculated liquids from LA‐ICPMS analyses are comparable to whole‐rock and glass values. Exceptions are clinopyroxene crystals from the Rigil Seamount, the second oldest seamount drilled at the northern end of the chain. Some crystals from this site are strongly zoned with distinct compositional boundaries between cores and mantles. The cores have high Mg/(Mg + Fe) and low Al and Ti concentrations compared to the mantles and phenocrysts. Major element, clinopyroxene discrimination diagrams indicate that the clinopyroxene mantles and phenocrysts crystallized from alkalic basalts. In contrast, the Mg‐rich cores have tholeiitic affinities. The REE abundances of the cores are similar to that of clinopyroxene from transitional tholeiites of the Kerguelen Archipelago. Calculated liquid La/Yb values for the cores have ratios that are similar to transitional tholeiites in Hawaii, whereas the mantles have higher La/Yb values similar to Hawaiian alkalic basalts. The major and trace element compositions of clinopyroxene cores from the Rigil seamount suggest that a transitional tholeiitic magma was present, but no evidence for Hawaiian shield‐type tholeiites was found. Plagioclase crystals from the Rigil seamount have 86Sr/86Sr from 0.70306 to 0.70363, within the range of FOZO. The transitional tholeiitic signature of the Mg‐rich clinopyroxene cores probably did not have a distinct source compared to other Louisville magmas, but more likely indicates a higher degree of partial melting (2–5%) of that FOZO source.

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Crystal recycling in the steady-state system of the active Stromboli volcano: a 2.5-ka story inferred from in situ Sr-isotope and trace element data

Cited by 59 publications

References 56 publications

Geochemical heterogeneities and dynamics of magmas within the plumbing system of a persistently active volcano: evidence from Stromboli

Geochemical heterogeneities and dynamics of magmas within the plumbing system of a persistently active volcano: evidence from Stromboli

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

Exploring the mineralogical heterogeneities of the Louisville Seamount Trail

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