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

Abstract

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

Weak Tectono-Magmatic Relationships along an Obliquely Convergent Plate Boundary: Sumatra, Indonesia

“…This somehow contrasts with previous evidence from the deeper structure of extinct and eroded magmatic arcs, where pluton emplacement has been commonly associated with local extension created by strike-slip systems (Acocella and Funiciello, 2010, and references therein). This may be explained by a different structural control of the magmatic arc at depth and at the surface, with a decoupling in the tectono-magmatic relationships responsible for a stronger structural control on magma emplacement at depth and a weaker control on the rise of the magma at the surface; a similar behavior has been postulated for the central Aeolian Arc (Ruch et al, 2016). Another possibility to explain the apparently more limited structural control on the Sumatra arc compared to other eroded arcs may be related to the different timing in the development of the GSF along the island.…”

“…Another possibility to locally explain the arc-normal extension may be related to the pressurization promoted by the intruded magma along the arc. A similar mechanism has been proposed to explain the widespread and consistent extensional structures on the central Aeolian Arc (Ruch et al, 2016), inferred to experience strike-slip motions at depth (De Astis et al, 2003). However, such a possible shallow tectonic reorganization does not appear completely feasible for the Sumatra Arc.…”

“…These general relations between volcanism and strike-slip structures are largely confirmed by the deeper structure of extinct and eroded magmatic arcs: there pluton emplacement has been most commonly associated with the local extension created by strike-slip systems (e.g., Tobisch and Cruden, 1995;Acocella and Funiciello, 2010, and references therein). However, recent studies on active volcanic arcs inferred to experience significant strike-slip motion, as the central Aeolian arc (Italy;De Astis et al, 2003), suggest a tectonic reorganization with predominant magma-induced extension at the surface, without evident strikeslip faulting (Ruch et al, 2016).…”

Learning about Hydrothermal Volcanic Activity by Modeling Induced Geophysical Changes

“…The development of the island is strongly influenced by the Tindari-Letojanni regional dextral fault system and by minor N-S to NE-SW trending normal faults and cracks associated to the main NW-SE shear zone (Ventura et al, 1999;De Astis et al, 2013). The shallow structures of volcano complex were defined by several geophysical studies since the 70s (Barberi et al, 1994;BlancoMontenegro et al, 2007;Napoli and Currenti, 2016;Ruch et al, 2016), and by two deep geothermal drillings (Figure 1) in 1983-1987(Gioncada and Sbrana, 1991, located at the foot of the south-western and northern flanks of La Fossa crater. Since the end of the last magmatic eruption in 1890, the volcano activity has been characterized by fumarolic emissions of variable intensity and temperature and seismic crises due to magmawater interaction (Alparone et al, 2010;Federico et al, 2010).…”

Impact of the Dead Sea Transform Kinematics on Adjacent Volcanic Activity

“…The petrogenetic relations of volcanism to continental transforms are not always well established (e.g., Aydin & Nur, 1982;Weinstein & Garfunkel, 2014), and often the strike-slip faults only interact with volcanism en route to the surface, affecting their distribution and channeling magmas along preferred avenues (e.g., Garfunkel, 1989;Marra, 2001;Mathieu et al, 2011;Weinstein, 2012). By the same token, magmatic intrusions may affect strike-slip fault structures, by enhancing the formation of pull-apart basins (e.g., Girard & van Wyk de Vries, 2005) or imposing transient changes to the local stress field (e.g., Ruch et al, 2016).…”