Dike emplacement Research Papers - Academia.edu (original) (raw)

Observations of active dike intrusions provide present day snapshots of the magmatic contribution to continental rifting. However, unravelling the contributions of upper crustal dikes over the timescale of continental rift evolution is a... more

Observations of active dike intrusions provide present day snapshots of the magmatic contribution to continental rifting. However, unravelling the contributions of upper crustal dikes over the timescale of continental rift evolution is a significant challenge. To address this issue, we analyzed the morphologies and alignments of >1500 volcanic cones to infer the distribution and trends of upper crustal dikes in various rift basins across the East African Rift (EAR). Cone lineament data reveal along-axis variations in the distribution and geometries of dike intrusions as a result of changing tectonomagmatic conditions. In younger (<10 Ma) basins of the North Tanzanian Divergence, dikes are largely restricted to zones of rift-oblique faulting between major rift segments, referred to here as transfer zones. Cone lineament trends are highly variable, resulting from the interplay between (1) the regional stress field, (2) local magma-induced stress fields, and (3) stress rotations related to mechanical interactions between rift segments. We find similar cone lineament trends in transfer zones in the western branch of the EAR, such as the Virunga Province, Democratic Republic of the Congo. The distributions and orientations of upper crustal dikes in the eastern branch of the EAR vary during continental rift evolution. In early-stage rifts (<10 Ma), upper crustal dikes play a limited role in accommodating extension, as they are confined to areas in and around transfer zones. In evolved rift basins (>10 Ma) in Ethiopia and the Kenya Rift, rift-parallel dikes accommodate upper crustal extension along the full length of the basin.

In Flood Control 2015, technology is used as a means to enable people to better assess and respond to risky situations. From manager to citizen, people make decisions depending upon the circumstances at hand. If there is more certainty... more

In Flood Control 2015, technology is used as a means to enable people to better assess and respond to risky situations. From manager to citizen, people make decisions depending upon the circumstances at hand. If there is more certainty about the current situation, and if pertaining information is purposefully provided, the adverse consequences of flooding can be limited. By making smart use of the most advanced information and technology available, Flood Control 2015 makes it possible to take informed action. As illustration of the applicability and need of the Flood Control 2015 advances, ample use was made of these innovations not only within the Netherlands, but also in Indonesia and the US. Improved flood forecasting systems or real-time monitoring of flood defences are not objectives in themselves. A characteristic feature of the Flood Consortium 2015 is that it develops knowledge and tools that are suitable for use in day-to-day practice of several professional disciplines, not only for those responsible for operational water management but also for decision-makers on different levels, crisis managers, communication advisors, news agencies and the emergency services. All of the aforementioned benefit from the yields of this program. Let us not forget about the communities within the areas at risk who will now be better equipped to help themselves and their neighbours by using this improved information and means of communication.

Magma transport in brittle rock occurs by diking. Understanding the dy- namics of diking and its observable consequences is essential to deciphering magma propagation in volcanic areas. Furthermore, diking plays a key role in tectonic... more

Magma transport in brittle rock occurs by diking. Understanding the dy- namics of diking and its observable consequences is essential to deciphering magma propagation in volcanic areas. Furthermore, diking plays a key role in tectonic phenomena such as continental rifting and plate divergence at mid-ocean ridges. Physics-based models of propagating dikes usually involve coupled transport of a viscous fluid with rock deformation and fracture. But the behaviour of dikes is also affected by the exchange of heat with the sur- roundings and by interaction with rock layering, pre-existing cracks, and the external stress field, among other factors. This complexity explains why ex- isting models of propagating dikes are still relatively rudimentary: they are mainly 2D, and generally include only a subset of the factors described above. Here, we review numerical models on dike propagation focusing on the most recent studies (from the last 15–20 years). We track the influence of two main philosophies, one in which fluid dynamics are taken to control the behavior and the other which focuses on rock fracturing. It appear that uncertainties in the way that rock properties such as fracture toughness vary from labora- tory to field scale remains one of the critical issues to be resolved. Finally, we present promising directions of research that include emerging approaches to numerical modeling and insights from hydraulic fracturing as an industrial analogue.

In this paper, an enriched finite element technique is presented to simulate the mechanism of interaction between the hydraulic fracturing and frictional natural fault in impermeable media. The technique allows modeling the... more

In this paper, an enriched finite element technique is presented to simulate the mechanism of interaction between the hydraulic fracturing and frictional natural fault in impermeable media. The technique allows modeling the discontinuities independent of the finite element mesh by introducing additional degrees of freedom. The coupled equilibrium and flow continuity equations are solved using a staggered Newton solution strategy; and an algorithm is proposed on the basis of fixed-point iteration concept to impose the flow condition at the hydro-fracture mouth. The cohesive crack model is employed to introduce the nonlinear fracturing process occurring ahead of the hydro-fracture tip. Frictional contact is modeled along the natural fault using the penalty method within the framework of plasticity theory of friction. Moreover, an experimental investigation is carried out to perform the hydraulic fracturing experimental test in fractured media under plane strain condition. The results of several numerical and experimental simulations are presented to verify the accuracy and robustness of proposed computational algorithm as well as to investigate the mechanisms of interaction between the hydraulically-driven fracture and frictional natural fault.

A model of magma propagation in the crust is presented using a series of analogue experiments, where dyed water is injected at a constant flux into layers of solidified gelatine. The gelatine layers are transparent and, when intruded,... more

A model of magma propagation in the crust is presented using a series of analogue experiments, where dyed water is injected at a constant flux into layers of solidified gelatine. The gelatine layers are transparent and, when intruded, deform in an almost ideal-elastic manner under the experimental conditions (low gelatine concentration: 2.5 or 3 wt%, and low temperature: 5–10◦C). The upper gelatine layer was 1.0 to 1.5 times stiffer than the lower layer, with either a ‘weak’ or ‘strong’ interface strength between the gelatine layers. The gelatine is seeded with 20–50μm-diameter PMMA-RhB neutrally buoyant particles that are fluoresced by a pulsed, vertical laser sheet centred on the injection point. Digital image correlation (DIC) is used to calculate incremental strain and finite strain in the deforming host material as it is intruded. This is mapped in 2D for the developing experimental volcanic plumbing system that comprises a feeder dyke and sill. Since the gelatine deforms elastically, strain measurements correlate with stress. Our results indicate that, for constant magma flux, the moment of sill inception is characterised by a significant magmatic pressure decrease of up to ∼60%. This is evidenced by the rapid contraction of the feeder dyke at the moment the sill forms. Sill propagation is then controlled by the fracture properties of the weak interface, with fluid from the feeder dyke extracted to help grow the sill. Pressure drops during sill inception and growth are likely to be important in volcanic systems, where destabilisation of the magmatic plumbing system could trigger an eruption.

It is of great importance in many fields to be able to forecast the likely propagation paths of fluid-driven factures. These include mineral veins, human-made hydraulic fractures, and dikes/inclined sheets. The physical principles that... more

It is of great importance in many fields to be able to forecast the likely propagation paths of fluid-driven factures. These include mineral veins, human-made hydraulic fractures, and dikes/inclined sheets. The physical principles that control the propagation of all fluid-driven fractures are the same. Here the focus is on dikes and inclined sheets where the selected path determines whether, where, and when a particular dike/sheet reaches the surface to erupt. Here we provide analytical and numerical models on dike/sheet paths in crustal segments (including volcanoes) that include layers of various types (lava flows, pyroclastic flows, tuff layers, soil layers, etc) as well as mechanically weak contacts and faults. The modelling results are then compared with, and tested on, actual data of two types. (a) Seismic data on the paths of dikes/sheets as well as human-made hydraulic fractures, and (b) field data on the actual propagation paths of dikes/sheets in layered and faulted rocks The numerical results show that, particularly in stratovolcanoes, the paths are likely to be complex with common deflections along layer contacts, in agreement with field observations. Also, some dikes/sheets may use existing faults as parts of their paths, primarily steeply dipping and recently active normal faults. The propagation path is thus not entirely in pure mode I but rather partly in a mixed mode. The energy required to propagate the dike/sheet is mainly the surface energy needed to rupture the rock, to form two new surfaces and move them apart as the fracture propagates. The energy available to drive the fracture is the stored elastic energy in the hosting crustal segment. From its point of initiation in the magma-chamber roof, a dike/sheet can, theoretically, select any one of an infinite number of paths to follow to its point of arrest or eruption. It is shown that the eventual path selected is the one of least action, that is, the path along which the time integral of the difference between the kinetic and potential energies is an extremum (normally a minimum) relative to all other possible paths with the same endpoints. If the kinetic energy is omitted, and there are no constraints, then least action becomes the minimum potential energy, which was postulated as a basis for understanding dike propagation by Gudmundsson (1986). Here it is shown how this theoretical framework can help us make reliable forecasts of dike/sheet paths and associated volcanic eruptions. Gudmundsson, A., 1986. Formation of dykes, feeder-dykes, and the intrusion of dykes from

Although subparallel swarms of dikes are thought to be the primary feeders to voluminous volcanic eruptions, increasing recognition of volumetrically significant sill complexes suggests that they too play an important role in magma ascent... more

Although subparallel swarms of dikes are thought to be the primary feeders to voluminous volcanic eruptions, increasing recognition of volumetrically significant sill complexes suggests that they too play an important role in magma ascent through the shallow crust. However, the extent to which sills and interconnected, sill-fed dikes actually transport magma to the earth's surface in many large igneous provinces (LIP) is presently unclear. By analyzing field relationships and dimensions of intrusions of the Ferrar LIP in South Victoria Land, Antarctica, we show that sill-fed dikes were the likely feeders for voluminous flood basalt eruptions. These intrusions are small but numerous, with cumulative dimensions equivalent to a feeder network 308,000 km long and 1.8 m wide. Due to the tremendous aerial extent of this intrusive network, each individual dike-feeder segment would only be required to actively feed magma for 2 to 3 days on average to erupt the 70,000 km3 of flood lavas ...

The relationship between mantle perturbation, penetrative magmatism, crustal uplift and the processes of rifting and rift propagation was studied. Quasi-scale model experiments and theoretical analyses by Boussinesq's three function... more

The relationship between mantle perturbation, penetrative magmatism, crustal uplift and the processes of rifting and rift propagation was studied. Quasi-scale model experiments and theoretical analyses by Boussinesq's three function method were used. Three dimensional stress analyses around a rising mantle intrusion and semiquantitative model experiments on mantle upwelling and magma penetration into brittle and brittle-ductile lithospheric materials indicate the origin of ridges, rifts, and rift-basin structures. These structures are commonly initiated by broad domal or plateau uplift. The magnitude and nature of the uplift, fissure or rift development, branching and pattern(s) are controlled primarily by flexural rigidity, magnitude of stress development due to mantle intrusion and magma penetration, and the degree of preferred orientation of weakness (anisotropy) in the lithosphere. Continued magma penetration into the crust produces en echelon fissures, vertical and lateral dike propagation, graben and graben and horst structures with step or block faulting. This is followed by axial subsidence, fault opening and periodic volcanism with continued crustal extension, stretching and slow spreading. Mantle and magma penetration into the crust are shown to be important in developing in situ lateral compressive stress adjacent to and around the active rift zones. Transverse fissures, dike swarms, volcanoes and anticlines between two rifts (as in Iceland) result from such lateral compressive stress. This stress is also important in the development of marginal fissures and faults (as in fast-spreading centers). Time progressive model experiments on magma formation and magma penetration from the asthenosphere-lithosphere boundary show the importance of magma chambers. These chambers cause thinning and stretching of the composite lithosphere, vertical and lateral propagation of dikes and dike swarms, and initiate rifts with or without significant uplift. This study also suggests that multiple dike wedging with rapid extension fracturing can generate excess magma pressure and push force, and may contribute seismicity to spreading centers.

A 45-km-long regional dike was emplaced over a period of 2 weeks in August 2014 at the boundary between the East and North Volcanic Zones in Iceland. This is the first regional dike emplacement in Iceland monitored with modern geophysical... more

A 45-km-long regional dike was emplaced over a period of 2 weeks in August 2014 at the boundary between the East and North Volcanic Zones in Iceland. This is the first regional dike emplacement in Iceland monitored with modern geophysical networks, the importance of which relates to regional dikes feeding most of the large fissure (e.g., Eldgja 934 and Laki 1783) and lava shield (e.g. early Holocene Skjaldbreidur and Trölladyngja) eruptions. During this time, the dike generated some 17,000 earthquakes, more than produced in Iceland as a whole over a normal year. The dike initiated close to the Bardarbunga Volcano but gradually extended to the northeast until it crossed the boundary between the East Volcanic Zone (EVZ) and the North Volcanic Zone (NVZ). We infer that the strike of the dike changes abruptly at a point, from about N45ºE (coinciding with the trend of the EVZ) to N15ºE (coinciding with the trend of the NVZ). This change in strike occurs at latitude 64.7º, exactly the same latitude at which about 10 Ma dikes in East Iceland change strike in a similar way. This suggests that the change in the regional stress field from the southern to the northern part of Iceland has been maintained at this latitude for 10 million years. Analytical and numerical models indicate that the dike-induced stress field results in stress concentration around faults and particularly shallow magma chambers and calderas in its vicinity, such as Tungnafellsjökull, Kverkfjöll, and Askja. In particular, the dike has induced high compressive, shear, and tensile stresses at the location of the Bardarbunga shallow chamber and (caldera) ring-fault where numerous earthquakes occurred during the dike emplacement, many of which have exceeded M5 (the largest M5.7). The first segment of the dike induced high tensile stresses in the nearby part of the Bardarbunga magma chamber/ring-fault resulting in radially outward injection of a dike from the chamber at a high angle to the strike of the regional dike. The location of maximum stress at Bardarbunga fluctuates along the chamber/ring-fault boundary in harmony with dike size and/or pressure changes and encourages ring-dike formation and associated magma flow within the chamber. Caldera collapse and/or eruption in some of these volcanoes is possible, most likely in Bardarbunga, but depends largely on the future development of the regional dike.
Keywords: Crustal stresses, dike propagation, feeder dike, volcano deformation, volcano

Abstract: The surface expressions of most Holocene rift-zone volcanic systems in Iceland are 40-150 km long and 5-20 km wide swarms of tension fractures, normal faults and basalt volcanoes each of which extends from a central volcano (a... more

Abstract: The surface expressions of most Holocene rift-zone volcanic systems in Iceland are 40-150 km long and 5-20 km wide swarms of tension fractures, normal faults and basalt volcanoes each of which extends from a central volcano (a composite volcano or a caldera). Below the Holocene surface, the swarms are mainly composed of subvertical dykes and normal faults except within the central volcanoes where the main tectonic elements are inclined sheets. The inclined sheets are mostly 0.5 m thick, whereas the regional dykes ...

Magma intrusions grow to their final geometries by deforming the Earth's crust internally and by displacing the Earth's surface. Interpreting the related displacements in terms of intrusion geometry is key to forecasting a volcanic... more

Magma intrusions grow to their final geometries by deforming the Earth's crust internally and by displacing the Earth's surface. Interpreting the related displacements in terms of intrusion geometry is key to forecasting a volcanic eruption. While scaled laboratory models enable us to study the relationships between surface displacement and intrusion geometry, past approaches entailed limitations regarding imaging of the laboratory model interior or simplicity of the simulated crustal rheology. Here we apply cutting-edge medical wide beam X-ray Computed Tomography (CT) to quantify in 4D the deformation induced in laboratory models by an intrusion of a magma analog (golden syrup) into a rheologically-complex granular host rock analog (sand and plaster). We extract the surface deformation and we quantify the strain field of the entire experimental volume in 3D over time by using Digital Volume Correlation (DVC). By varying the strength and height of the host material, and intrusion velocity, we observe how intrusions of contrasting geometries grow, and induce contrasting strain field characteristics and surface deformation in 4D. The novel application of CT and DVC reveals that distributed strain accommodation and mixed-mode (opening and shear) fracturing dominates in low-cohesion material overburden, and leads to the growth of thick cryptodomes or cup-shaped intrusions. More localized strain accommodation and opening-mode fracturing dominates in high-cohesion material overburden, and leads to the growth of cone sheets or thin dikes. The results demonstrate how the combination of CT and DVC can greatly enhance the utility of optically non-transparent crustal rock analogs in obtaining insights into shallow crustal deformation processes. This unprecedented perspective on the spatio-temporal interaction of intrusion growth coupled with host material deformation provides a conceptual framework that can be tested by field observations at eroded volcanic systems and by the ever increasing spatial and temporal resolution of geodetic data at active volcanoes.

Although monogenetic volcanic fields pose hazards to major cities worldwide, their shallow magma feeders (<500 m depth) are rarely exposed and, therefore, poorly understood. Here, we investigate exposures of dikes and sills in the Hopi... more

Although monogenetic volcanic fields pose hazards to major cities worldwide, their shallow magma feeders (<500 m depth) are rarely exposed and, therefore, poorly understood. Here, we investigate exposures of dikes and sills in the Hopi Buttes volcanic field, Arizona, to shed light on the nature of its magma feeder system. Shallow exposures reveal a transition zone between intrusion and eruption within 350 m of the syn-eruptive surface. Using a combination of field-and satellite-based observations, we have identified three types of shallow magma systems: (1) dike-dominated, (2) sill-dominated , and (3) interconnected dike-sill networks. Analysis of vent alignments using the pyroclastic massifs and other erup-tive centers (e.g., maar-diatremes) shows a NW-SE trend, parallel to that of dikes in the region. We therefore infer that dikes fed many of the eruptions. Dikes are also observed in places transforming to transgressive (ramping) sills. Estimates of the observable volume of dikes (maximum volume of 1.90 × 10 6 m 3) and sills (minimum volume of 8.47 × 10 5 m 3) in this study reveal that sills at Hopi Buttes make up at least 30 % of the shallow intruded volume (∼2.75 × 10 6 m 3 total) within 350 m of the paeosurface. We have also identified saucer-shaped sills, which are not traditionally associated with monogenetic volcanic fields. Our study demonstrates that shallow feeders in monogenetic fields can form geometrically complex networks, particularly those intruding poorly consolidated sedimentary rocks. We conclude that the Hopi Buttes eruptions were primarily fed by NW-SE-striking dikes. However, saucer-shaped sills also played an important role in modulating eruptions by transporting magma toward and away from eruptive conduits. Sill development could have been accompanied by surface uplifts on the order of decime-ters. We infer that the characteristic feeder systems described here for the Hopi Buttes may underlie monogenetic fields elsewhere, particularly where magma intersects shallow, and often weak, sedimentary rocks. Results from this study support growing evidence of the important role of shallow sills in active monogenetic fields.

A fraction of the volcanic activity occurs intraplate, challenging our models of melting and magma transfer to the Earth's surface. A prominent example is Mt. Etna, eastern Sicily, offset from the asthenospheric tear below the Malta... more

A fraction of the volcanic activity occurs intraplate, challenging our models of melting and magma transfer to the Earth's surface. A prominent example is Mt. Etna, eastern Sicily, offset from the asthenospheric tear below the Malta Escarpment proposed as its melt source. The nearby Hyblean volcanism, to the south, and the overall northward migration of the eastern Sicilian volcanism are also unexplained. Here we simulate crustal magma pathways beneath eastern Sicily, accounting for regional stresses and decompression due to the increase in the depth of the Malta Escarpment. We find non-vertical magma pathways, with the competition of tectonic and loading stresses controlling the trajectories' curvature and its change in time, causing the observed migration of volcanism. This suggests that the Hyblean and Etnean volcanism have been fed laterally from a melt pooling region below the Malta Escarpment. The case of eastern Sicily shows how the reconstruction of the evolution of magmatic provinces may require not only an assessment of the paleostresses, but also of the contribution of surface loads and their variations; at times, the latter may even prevail. Accounting for these competing stresses may help shed light on the distribution and wandering of intraplate volcanism

Flood Control 2015 is five years of innovation directly towards increased flood protection. The private sector, knowledge institutes and public users united their skill and expertise through an integrated effort to achieve a cohesive,... more

Flood Control 2015 is five years of innovation directly towards increased flood protection. The private sector, knowledge institutes and public users united their skill and expertise through an integrated effort to achieve a cohesive, practical approach to determining and mitigating flood risk. The innovations produced by Flood Control 2015 have resulted in improved decision-making, increased community and individual flood resilience, and a reduction in flood-related damage.

Popular article on the value of dikes in Holland focusing on archaeology and landscape/seascape.

Fissure eruptions are commonly linked to magma dikes at depth and are associated with elastic and inelastic surface deformation. Elastic deformation is well described by subsidence occurring above the dike plane and uplift and lateral... more

Fissure eruptions are commonly linked to magma dikes at depth and are associated with elastic and inelastic surface deformation. Elastic deformation is well described by subsidence occurring above the dike plane and uplift and lateral widening occurring perpendicular to the dike plane. Inelastic deformation is associated with the formation of a graben, which is bordered by graben parallel faults that might express as sets of fractures at the surface. Additionally, secondary structures, such as push-ups, bends and step overs, yield information about the deforming domain. However, once these structures are formed during fissure eruptions, they are rarely preserved in nature, due to the effects of rapid erosion, sediment coverage or overprinting by other faulting events. Therefore, simple normal fault displacements are commonly assumed at dikes. At the 2014/2015 Holuhraun eruption sites (Iceland), increasing evidence suggests that developing fractures exhibited variations in their displacement modes. In an attempt to investigate these variations, a fieldwork mapping project combining Terrestrial Laser Scanning (TLS) and Unmanned Aerial Vehicle (UAV)-based aerophoto analysis was undertaken. Using these data, we generated local high-resolution Digital Elevation Models (DEMs) and a structural map that facilitated the identification of kinematic indicators and the assessment of the observed structures. We identified 315 fracture segments from these satellite data. We measured the strike directions of single segments, including the amount of opening and opening angles, which indicate that many of the measured fractures show transtensional dislocations. Of these, ∼81% exhibit a significant left-lateral component and only ∼17% exhibit a right-lateral component. Here, we demonstrate that the local complexities in these fracture traces and geometries are closely related to variations in their transtensional opening directions. Moreover, we identified local changes in fracture azimuths and offsets close to eruption sites, which we speculate are associated with geometric changes in the magma feeder itself.

ABSTRACT Flood Control 2015 is five years of innovation directly towards increased flood protection. The private sector, knowledge institutes and public users united their skill and expertise through an integrated effort to achieve a... more

ABSTRACT Flood Control 2015 is five years of innovation directly towards increased flood protection. The private sector, knowledge institutes and public users united their skill and expertise through an integrated effort to achieve a cohesive, practical approach to determining and mitigating flood risk. The innovations produced by Flood Control 2015 have resulted in improved decision-making, increased community and individual flood resilience, and a reduction in flood-related damage.

Although subparallel swarms of dikes are thought to be the primary feeders to voluminous volcanic eruptions, increasing recognition of volumetrically significant sill complexes suggests that they too play an important role in magma ascent... more

Although subparallel swarms of dikes are thought to be the primary feeders to voluminous volcanic eruptions, increasing recognition of volumetrically significant sill complexes suggests that they too play an important role in magma ascent through the shallow crust. However, the extent to which sills and interconnected, sill-fed dikes actually transport magma to the earth's surface in many large igneous provinces (LIP) is presently unclear. By analyzing field relationships and dimensions of intrusions of the Ferrar LIP in South Victoria Land, Antarctica, we show that sill-fed dikes were the likely feeders for voluminous flood basalt eruptions. These intrusions are small but numerous, with cumulative dimensions equivalent to a feeder network 308,000 km long and 1.8 m wide. Due to the tremendous aerial extent of this intrusive network, each individual dike-feeder segment would only be required to actively feed magma for 2 to 3 days on average to erupt the 70,000 km3 of flood lavas represented by the Kirkpatrick basalts. The Ferrar intrusions form a broadly-distributed array of small, moderately dipping dikes (<2 km long, 1.8 m wide, 56° mean dip) exhibiting almost any orientation. This sill-fed dike network contrasts with dike swarms conventionally depicted to feed flood basalt provinces, and has the appearance of a variably “cracked lid” atop a sill complex. The cracked lid model may apply to a range of shallow feeder systems (<4 km depth) intruding sedimentary basins, where the effects of far-field tectonic stresses are negligible and sill intrusions exert the dominant control on dike orientations. We conclude that sill inflation, and resulting deformation of surrounding host rock, plays a critical role in the ascent of magma in shallow volcanic systems that span the full spectrum of eruptive volumes.