Effect of local and regional stress fields on sheet emplacement in West Iceland

Gautneb, Håvard; Guðmundsson, Ágúst

doi:10.1016/0377-0273(92)90107-o

Cited by 58 publications

(17 citation statements)

References 17 publications

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“…Qualitatively, this prediction is supported by the general observation that swarms of inclined sheets are restricted to the immediate vicinity of crustal magma chambers (as represented by plutons) in extinct central volcanoes in Iceland. Quantitatively, this prediction is confirmed by the abrupt change in strike, dip, thickness, and abundance of sheets at a distance of 9 km from the center of the Tertiary Reykjadalur Central Volcano in west Iceland [Gautneb and Gudmundsson, 1992]. At distances less than 9 km the sheets strike in various directions, have a mean dip of 45 ø and a mean thickness of i m, and form a typical swarm of inclined sheets.…”

Section: Discussionmentioning

confidence: 69%

Magma chambers modeled as cavities explain the formation of rift zone central volcanoes and their eruption and intrusion statistics

Guðmundsson¹

1998

J. Geophys. Res.

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119

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Section: Discussionmentioning

confidence: 69%

Magma chambers modeled as cavities explain the formation of rift zone central volcanoes and their eruption and intrusion statistics

Guðmundsson¹

1998

J. Geophys. Res.

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119

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“…Formation of a dyke complex requires that a volcano be capable of widening sufficiently to accommodate the dykes; otherwise an intrusive-sheet (conesheet) complex that is accommodated by thickening of the volcano develops instead. Recent studies (Gautneb & Gudmundsson 1992;Walker, this volume) show that cone-sheets are closely similar to dykes in width and in having their dilation vector normal to the intrusionplane.…”

Section: Neutral Buoyancy Controlmentioning

confidence: 89%

“…Lateral dyke-injection from a high-level magma chamber is thought to be important near volcanic centres, but further away dykes may commonly be injected vertically upward from a deep reservoir (Gautneb & Gudmundsson, 1992).…”

Section: Propagation Of Bladed Dykesmentioning

confidence: 99%

Basaltic-volcano systems

Walker

1993

194

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This review and personal account of basaltic volcanism concentrates on the geological aspects and physical controls, unlike most others which concentrate on geochemistry. It serves as an update to reviews by Wentworth & Macdonald 20 to 40 years ago. The concept of volcanic systems is developed, a system including the plumbing, intrusions, and other accoutrements of volcanism, as well as the volcanic edifice. Five types of systems are described, namely lava-shield volcanoes, stratovolcanoes, flood-basalt fields, monogenetic-volcano fields, and central volcanoes (having silicic volcanics as well as basaltic). It is postulated that the system-type depends on (a) the magma-input rate and (b) the frequency with which magma-batches enter the system (or modulation frequency). These controls determine whether a hot pathway is maintained from the source to the high-level magma chamber, and hence if eruptions are concentrated in the central-vent system. Reviews are given on many aspects: the different kinds of rift zones that volcanoes exhibit, and their controls; the mostly small intrusions, including coherent-intrusion complexes, that occur in and under the volcanic edifices; the great sill swarms that are an alternative to flood basalts; the origin of the craters and calderas of basaltic volcanoes; high-level magma chambers, their locations, and cumulate prisms; the positive Bouguer gravity anomalies that are attributed to cumulates and intrusion complexes; the structures of basaltic lava flows; the characteristics of basaltic explosive volcanism and the consequences of participation by nonvolcanic water; the products of underwater volcanism; the origin and significance of joints, formed either by contraction or expansion, in volcanic rocks; and the distribution of vesicles in basaltic rocks. A fairly extensive bibliography is included. This is in part a review; it takes stock of changes in concepts since the publications by Wentworth & Macdonald (1953) and Macdonald (1967), which were models of clear description of basaltic volcanics, and since the publication 12 years ago of the landmark Basaltic Volcanism Study Project (1981). It also incorporates new ideas, new interpretations, and new ways of looking at the subject. The scope of basaltic volcanism is too broad to cover all aspects, and petrology and geochemistry are specifically omitted.More than half of the world's volcanoes are basaltic or include basalt among their products; and about one third of known eruptions, involving about 20 volcanoes per year erupt basaltic magma. Basaltic volcanoes occur in all tectonic settings. Basaltic volcanism is associated with both divergent and convergent plate boundaries; it characterizes spreading ridges mostly concealed beneath the ocean; it characterizes hotspot volcanism which, in oceanic settings, is almost exclusively basaltic and, in continental settings, is commonly bimodal (basaltic plus rhyolitic); and it is widespread associated with andesitic and more silicic magmas in subduction-zone settings, particula...

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“…Regional dikes are often sub-vertical and aligned orthogonal to the regional tectonic σ3, as observed along the axis of rift zones, both within and outside the calderas. Dikes that propagate within the volcanic edifice are likely to be controlled by the local stress field (Gautneb and Gudmundsson, 1992). These dikes may be arranged as centrallyinclined sheets (e.g., cone sheets), which are commonly circular or elliptical in map view, and/or have a radial distribution in alignment with the axis of the edifice (e.g., Acocella and Neri, 2009).…”

Section: Introductionmentioning

confidence: 99%

How caldera collapse shapes the shallow emplacement and transfer of magma in active volcanoes

Corbi

Rivalta

Pinel

et al. 2015

Earth and Planetary Science Letters

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Calderas are topographic depressions formed by the collapse of a partly drained magma reservoir. At volcanic edifices with calderas, eruptive fissures can circumscribe the outer caldera rim, be oriented radially and/or align with the regional tectonic stress field. Constraining the mechanisms that govern this spatial arrangement is fundamental to understand the dynamics of shallow magma storage and transport and evaluate volcanic hazard. Here we show with numerical models that the previously unappreciated unloading effect of caldera formation may contribute significantly to the stress budget of a volcano. We first test this hypothesis against the ideal case of Fernandina, Gal ‡pagos, where previous models only partly explained the peculiar pattern of circumferential and radial eruptive fissures and the geometry of the intrusions determined by inverting the deformation data. We show that by taking into account the decompression due to the caldera formation, the modeled edifice stress field is consistent with all the observations. We then develop a general model for the stress state at volcanic edifices with ! 1 calderas based on the competition of caldera decompression, magma buoyancy forces and tectonic stresses. These factors control: 1) the shallow accumulation of magma in stacked sills, consistently with observations; 2) the conditions for the development of circumferential and/or radial eruptive fissures, as observed on active volcanoes. This top-down control exerted by changes in the distribution of mass at the surface allows better understanding of how shallow magma is transferred at active calderas, contributing to forecasting the location and type of opening fissures.

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Effect of local and regional stress fields on sheet emplacement in West Iceland

Cited by 58 publications

References 17 publications

Magma chambers modeled as cavities explain the formation of rift zone central volcanoes and their eruption and intrusion statistics

Magma chambers modeled as cavities explain the formation of rift zone central volcanoes and their eruption and intrusion statistics

Basaltic-volcano systems

How caldera collapse shapes the shallow emplacement and transfer of magma in active volcanoes

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