Magma–serpentinite interaction as the origin of diatremes: a case study from the Hyblean Plateau (southeastern Sicily)

Manuella, Fabio Carmelo; Carbone, Serafina; Ferlito, Carmelo; Hovland, Martin

doi:10.1007/s00531-015-1257-0

Cited by 7 publications

(6 citation statements)

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“…The thermodynamic aspects of the interaction between mafic magmas and serpentinites at crustal depths, chiefly related to the formation of diatreme systems, were discussed by [17]. Here we tentatively address the same issue from the geochemical and petrologic perspectives, focusing on the non-explosive interaction processes, even though no quantitative approach is allowed, because of the obvious disequilibrium conditions of the invoked processes.…”

Section: Discussionmentioning

confidence: 99%

“…In this respect, [16] put forward, in a preliminary way, the hypothesis that the Hyblean diatremic eruptions resulted from the explosive interaction between serpentinite bodies and upwelling mafic magma at shallow/middle crustal depths. Manuella et al [17] later developed and substantiated such a hypothesis, particularly addressing the thermodynamic aspects of the process.…”

Section: Discussionmentioning

confidence: 99%

“…The second hypothesis suggests the crustal origin of the volatiles, which relates to the interaction of an original, volatile-poor, mafic magma with crustal rocks bearing abundant hydrous minerals (e.g., serpentinites). The breakdown of the hydrous minerals yields huge quantities of volatiles (mostly supercritical H 2 O), which can flush into the melt [16,17]. Here, we provide information about this problem by the petrographic and geochemical study of a silicate glass vein in a partially serpentinized peridotite xenolith from the Valle Guffari tuff-breccia deposit (Sicily, Southern Italy), recalling the notion that the "very small" can be helpful to understand the "very large" [18].…”

Section: Introductionmentioning

confidence: 99%

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A Volcanological Paradox in a Thin-Section: Large Explosive Eruptions of High-Mg Magmas Explained Through a Vein of Silicate Glass in a Serpentinized Peridotite Xenolith (Hyblean Area, Sicily)

2019

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Ultramafic magmas (MgO ≥ 18 wt%) are generally thought to be primary mantle melts formed at temperatures in excess of 1600 °C. Volatile contents are expected to be low, and accordingly, high-Mg magmas generally do not yield large explosive eruptions. However, there are important exceptions to low explosivity that require an explanation. Here we show that hydrous (hence, potentially explosive) ultramafic magmas can also form at crustal depths at temperatures even lower than 1000 °C. Such a conclusion arose from the study of a silicate glass vein, ~1 mm in thickness, cross-cutting a mantle-derived harzburgite xenolith from the Valle Guffari nephelinite diatreme (Hyblean area, Sicily). The glass vein postdates a number of serpentine veins already existing in the host harzburgite, thus reasonably excluding that the melt infiltrated in the rock at mantle depths. The glass is highly porous at the sub-micron scale, it also bears vesicles filled by secondary minerals. The distribution of some major elements corresponds to a meimechite composition (MgO = 20.35 wt%; Na2O + K2O < 1 wt%; and TiO2 > 1 wt%). On the other hand, trace element distribution in the vein glass nearly matches the nephelinite juvenile clasts in the xenolith-bearing tuff-breccia. These data strongly support the hypothesis that an upwelling nephelinite melt (MgO = 7–9 wt%; 1100 ≤ T ≤ 1250 °C) intersected fractured serpentinites (T ≤ 500 °C) buried in the aged oceanic crust. The consequent dehydroxilization of the serpentine minerals gave rise to a supercritical aqueous fluid, bearing finely dispersed, hydrated cationic complexes such as [Mg2+(H2O)n]. The high-Mg, hydrothermal solution "flushed" into the nephelinite magma producing an ultramafic, hydrous (hence, potentially explosive), hybrid magma. This hypothesis explains the volcanological paradox of large explosive eruptions produced by ultramafic magmas.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Volcanological Paradox in a Thin-Section: Large Explosive Eruptions of High-Mg Magmas Explained Through a Vein of Silicate Glass in a Serpentinized Peridotite Xenolith (Hyblean Area, Sicily)

2019

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“…12 quartz fragments must be ascribed only to quartzite clasts belonging to the alloctonous unit of the Numidian Flysch cropping out near that lava flow (Manuella et al, 2016). In addition, Sapienza et al (2007) reported the finding of several zircon grains in a metasomatite blackwall-type xenolith from Valle Guffari (Fig.…”

Section: Accepted Manuscriptmentioning

confidence: 97%

“…We selected a harzburgite xenolith (diameter of about 10 cm, comparable to that of Hyblean xenoliths ranging from 5 to 30 cm; Manuella et al, 2016), as representative of the Hyblean peridotite xenolith suite, which was sampled at Valle Guffari ( Fig. 1 Observations were made in backscattered electron mode, under high vacuum conditions at 20 kV accelerating voltage and 0.2 nA beam current.…”

Section: Petrographymentioning

confidence: 99%