Chapter 10 Stratigraphy and geological evolution of the Lipari volcanic complex (central Aeolian archipelago)

Forni, Francesca; Lucchi, Federico; Peccerillo, Angelo; Tranne, Claudio Antonio; Rossi, Paola; Frezzotti, Maria Luce

doi:10.1144/m37.10

Cited by 81 publications

(145 citation statements)

References 91 publications

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“…Compositionally the lava is calc-alkaline, and contains approximately 74 wt.% SiO 2 , 5 wt.% K 2 O and b1 wt.% H 2 O (Pichler, 1980;Gottsman & Dingwell, 2001;Davì et al, 2010;Lanzo et al, 2010). A high alkali content and an eruptive temperature of N850°C (Cas & Wright, n.d.;Davì, 2007) have been used to explain the anomalous length of the RR, as these factors lower magma viscosity and increase mobility of obsidian flows (Davì et al, 2011;Forni et al, 2013).…”

Section: Rocche Rosse Flow Descriptionmentioning

confidence: 99%

“…Rather shear deformation processes occurring down to microscopic scales during weeks of surface flow (Gottsman & Dingwell, 2001) overprint any flow-scale morphology. The dominant effect of surface deformation on observed textures may be a symptom of the high-alkali calc-alkaline composition and high eruptive temperature, which produce a less viscous and more mobile obsidian lava, prolonging viscous flow (Davì, 2007;Davì et al, 2011;Forni et al, 2013). Using the model of (Giordano et al, 2008), RR composition data from (Gottsman & Dingwell, 2001) and an eruptive temperature of 850 C (Cas & Wright, n.d.;Davì, 2007), a melt viscosity on the order of 10 8 -10 9 Pa s is calculated for the RR.…”

Section: Role Of Heterogeneities On Structural Evolution Of An Obsidimentioning

confidence: 99%

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Unravelling textural heterogeneity in obsidian: Shear-induced outgassing in the Rocche Rosse flow

Shields

Mader

Caricchi

et al. 2016

Journal of Volcanology and Geothermal Research

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Obsidian flow emplacement is a complex and understudied aspect of silicic volcanism. Of particular importance is the question of how highly viscous magma can lose sufficient gas in order to erupt effusively as a lava flow. Using an array of methods we study the extreme textural heterogeneity of the Rocche Rosse obsidian flow in Lipari, a 2 km long, 100 m thick,~800 year old lava flow, with respect to outgassing and emplacement mechanisms. 2D and 3D vesicle analyses and density measurements are used to classify the lava into four textural types: 'glassy' obsidian (b15% vesicles), 'pumiceous' lava (N 40% vesicles), high aspect ratio, 'shear banded' lava (20-40% vesicles) and low aspect ratio, 'frothy' obsidian with 30-60% vesicles. Textural heterogeneity is observed on all scales (m to μm) and occurs as the result of strongly localised strain. Magnetic fabric, described by oblate and prolate susceptibility ellipsoids, records high and variable degrees of shearing throughout the flow. Total water contents are derived using both thermogravimetry and infrared spectroscopy to quantify primary (magmatic) and secondary (meteoric) water. Glass water contents are between 0.08-0.25 wt.%. Water analysis also reveals an increase in water content from glassy obsidian bands towards 'frothy' bands of 0.06-0.08 wt.%, reflecting preferential vesiculation of higher water bands and an extreme sensitivity of obsidian degassing to water content. We present an outgassing model that reconciles textural, volatile and magnetic data to indicate that obsidian is generated from multiple shear-induced outgassing cycles, whereby vesicular magma outgasses and densifies through bubble collapse and fracture healing to form obsidian, which then re-vesiculates to produce 'dry' vesicular magma. Repetition of this cycle throughout magma ascent results in the low water contents of the Rocche Rosse lavas and the final stage in the degassing cycle determines final lava porosity. Heterogeneities in lava rheology (vesicularity, water content, microlite content, viscosity) play a vital role in the structural evolution of an obsidian flow and overprint flow-scale morphology. Post-emplacement hydration also depends heavily on local strain, whereby connectivity of vesicles as a result of shear deformation governs sample rehydration by meteoric water, a process previously correlated to lava vesicularity alone.

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Section: Rocche Rosse Flow Descriptionmentioning

confidence: 99%

Section: Role Of Heterogeneities On Structural Evolution Of An Obsidimentioning

confidence: 99%

Unravelling textural heterogeneity in obsidian: Shear-induced outgassing in the Rocche Rosse flow

Shields

Mader

Caricchi

et al. 2016

Journal of Volcanology and Geothermal Research

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“…2). The Rocche Rosse sits on top of older tephra deposits (Forni et al 2013). A thick (up to 10 m) basal breccia made up of angular obsidian blocks is evident at the base of the flow (Fig.…”

Section: Lithofacies Of Rhyolitic Lava Flowsmentioning

confidence: 98%

“…The most recent activity of Lipari comprised explosive pyroclastic deposits and rhyolitic lava flows, culminating in the extrusion of the Rocche Rosse and Forgia Vecchia rhyolite lava flows (Forni et al 2013). The pattern of this recent activity included a hydromagmatic phase, explosive eruption of a vesicular magma, accompanying fall and surge deposits and degassed viscous lava extrusion (Cortese et al 1986;Dellino and La Volpe 1995;Lucchi et al 2010;Forni et al 2013).…”

Section: Geological Settingmentioning

confidence: 99%

“…The pattern of this recent activity included a hydromagmatic phase, explosive eruption of a vesicular magma, accompanying fall and surge deposits and degassed viscous lava extrusion (Cortese et al 1986;Dellino and La Volpe 1995;Lucchi et al 2010;Forni et al 2013). The Rocche Rosse represents a renewal of activity, following the initial Monte Pilato-Rocche Rosse explosive phase.…”

Section: Geological Settingmentioning

confidence: 99%

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Emplacement of the Rocche Rosse rhyolite lava flow (Lipari, Aeolian Islands)

2018

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The Rocche Rosse lava flow marks the most recent rhyolitic extrusion on Lipari island (Italy), and preserves evidence for a multi-stage emplacement history. Due to the viscous nature of the advancing lava (10 8 to 10 10 Pa s), indicators of complex emplacement processes are preserved in the final flow. This study focuses on structural mapping of the flow to highlight the interplay of cooling, crust formation and underlying slope in the development of rhyolitic lavas. The flow is made up of two prominent lobes, small (< 0.2 m) to large (> 0.2 m) scale folding and a channelled geometry. Foliations dip at 2-4°over the flatter topography close to the vent, and up to 30-50°over steeper mid-flow topography. Brittle faults, tension gashes and conjugate fractures are also evident across flow. Heterogeneous deformation is evident through increasing fold asymmetry from the vent due to downflow cooling and stagnation. A steeper underlying topography mid-flow led to development of a channelled morphology, and compression at topographic breaks resulted in fold superimposition in the channel. We propose an emplacement history that involved the evolution through five stages, each associated with the following flow regimes: (1) initial extrusion, crustal development and small scale folding; (2) extensional strain, stretching lineations and channel development over steeper topography; (3) compression at topographic break, autobrecciation, lobe development and medium scale folding; (4) progressive deformation with stagnation, large-scale folding and refolding; and (5) brittle deformation following flow termination. The complex array of structural elements observed within the Rocche Rosse lava flow facilitates comparisons to be made with actively deforming rhyolitic lava flows at the Chilean volcanoes of Chaitén and Cordón Caulle, offering a fluid dynamic and structural framework within which to evaluate our data.

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Magmatic control along a strike-slip volcanic arc: The central Aeolian arc (Italy)

et al. 2016

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The regional stress field in volcanic areas may be overprinted by that produced by magmatic activity, promoting volcanism and faulting. In particular, in strike-slip settings, the definition of the relationships between the regional stress field and magmatic activity remains elusive.To better understand these relationships, we collected stratigraphic, volcanic and structural field data along the strike-slip Central Aeolian arc (Italy): here the islands of Lipari and Vulcano separate the extensional portion of the arc (to the east) from the contractional one (to the west). We collected >500 measurements of faults, extension fractures and dikes at 40 sites. Most structures are NNE-SSW to NNW-SSE oriented, eastward dipping, and show almost pure dip-slip motion; consistent with an E-W extension direction, with minor dextral and sinistral shear. Our data highlight six eruptive periods during the last 55 ka, which allow considering both islands as a single magmatic system, in which tectonic and magmatic activity steadily migrated eastward and currently focus on a 10 km long x 2 km wide active segment. Faulting appears to mostly occur in temporal and spatial relation with magmatic events, supporting that most of the observable deformation derives from transient magmatic activity (shorter-term, days to months), rather than from steady longer-term regional tectonics (10 2 -10 4 years). More in general, the Central Aeolian case shows how magmatic activity may affect the structure and evolution of volcanic arcs, overprinting any strike-slip motion with magma-induced extension at the surface. Keypoints: Relation between strike-slip kinematics and magmatism at volcanic arcs  Two neighbour volcanic islands share a single magmatic system  Magmatic stress is dominant and generates transient faulting

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Chapter 10 Stratigraphy and geological evolution of the Lipari volcanic complex (central Aeolian archipelago)

Cited by 81 publications

References 91 publications

Unravelling textural heterogeneity in obsidian: Shear-induced outgassing in the Rocche Rosse flow

Unravelling textural heterogeneity in obsidian: Shear-induced outgassing in the Rocche Rosse flow

Emplacement of the Rocche Rosse rhyolite lava flow (Lipari, Aeolian Islands)

Magmatic control along a strike-slip volcanic arc: The central Aeolian arc (Italy)

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