Magmatic fissures and their systems in Iceland: A tectonomagmatic model

Tentler, Tatiana; Temperley, Stephen

doi:10.1029/2006tc002037

Cited by 17 publications

(19 citation statements)

References 61 publications

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“…Vertical fractures related to normal faulting are also observed in Hawaii, although in that case the fractures are commonly distinct from the fault surface [e.g., Martel and Langley , 2006; Kaven and Martel , 2007]. Others interpret near‐vertical faults as reflective of the overall fault dip resulting from deflation of shallow sills, which would promote steeper dipping faults [e.g., Tentler and Temperley , 2007]. We have measured fault dips throughout our study area using high‐resolution bathymetric profiles and find values ranging from 45° to 80°, with a mean of ∼60°.…”

Section: Ast Formation By Dike Intrusionsmentioning

confidence: 99%

A record of eruption and intrusion at a fast spreading ridge axis: Axial summit trough of the East Pacific Rise at 9–10°N

Soule

Escartı́n

Fornari

2009

Geochem Geophys Geosyst

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[1] High-resolution side-scan sonar, near-bottom multibeam bathymetry, and deep-sea photo and bathymetry traverses are used to map the axial summit trough (AST) at the East Pacific Rise between 9 and 10°N. We define three ridge axis morphologic types: no AST, narrow AST, and wide AST, which characterize distinct ridge crest domains spanning tens of kilometers along strike. Near-bottom observations, modeling of deformation above intruding dikes, and comparisons to the geologic and geophysical structure of the ridge crest are used to develop a revised model of AST genesis and evolution. This model helps constrain the record of intrusive and extrusive magmatism and styles of lava deposition along the ridge crest at time scales from hundreds to tens of thousands of years. The grabens in the narrow-AST domain (9°43 0 -53 0 N) are consistent with deformation above the most recent (<10) diking events beneath the ridge crest. Frequent high-effusion rate extrusive volcanism in this domain (several eruptions every $100 years) overprints near-axis deformation and maintains a consistent AST width. The most recent eruption at the ridge crest occurred in this area and did not significantly modify the physical characteristics of the AST. The grabens in the wide-AST domain (9°23 0 -43 0 N) originated with similar dimensions to the narrow AST. Spreading, driven primarily by the intrusion of shallow dikes within a narrow axial zone, causes the initial graben bounding faults to migrate away from the axis. Infrequent extrusive volcanism (several eruptions every $1000 years) fills a portion of the subsidence that accumulates over time but does not significantly modify the width of the AST. Outside of these domains, lower-effusion rate constructional volcanism without efficient drain-back fills and erases the signature of the AST. The relative frequency of intrusive versus extrusive magmatic events controls the morphology of the ridge crest and appears to remain constant over millennial time scales within the domains we have identified; however, over longer time scales ($10-25 ka), domain-specific intrusive-to-extrusive ratios do not appear to be fixed in space, resulting in a fairly consistent volcanic accretion over the length scale of the second-order ridge segment between 9°N and 10°N.

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Section: Ast Formation By Dike Intrusionsmentioning

confidence: 99%

A record of eruption and intrusion at a fast spreading ridge axis: Axial summit trough of the East Pacific Rise at 9–10°N

Soule

Escartı́n

Fornari

2009

Geochem Geophys Geosyst

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“…The models either favour vertical dyke intrusions originating from axial reservoirs (e.g . Walker 1975;Gudmundsson 1990;Tentler & Temperley 2007), lateral intrusions from shallow magma chambers (e.g. Buck et al 2006;Paquet et al 2007) or a combination of the two (Walker 1992).…”

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confidence: 99%

Magma flow and palaeo-stress deduced from magnetic fabric analysis of the Álftafjörður dyke swarm: implications for shallow crustal magma transport in Icelandic volcanic systems

Eriksson

Riishuus

Elming

2014

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Neogene regional mafic dykes extending north of the Á lftafjörður central volcano in east Iceland are studied to test models of dyke swarm emplacement at spreading ridges. This is accomplished by using anisotropy of magnetic susceptibility to define fossilized magma flow regimes. The imbrication of the foliation plane, defined by the minor susceptibility axis, is used as an indicator of the flow direction. Contemporaneous shear resolved on the dyke walls may modify a pure flow-induced fabric and such shear regimes are therefore retracted. The magma flow and palaeo-stress resolved on the dykes are determined in 13 of 24 dykes. The magma flow is interpreted as subhorizontal and northwards directed away from the central volcano for nine dykes, and found to be vertical in three cases. The preferentially subhorizontal magma flow in the Á lftafjörður swarm suggests that dyke propagation in this type of Icelandic volcanic system originates in shallow crustal magma chambers. The regional tectonic palaeo-stress field is deduced to cause oblique spreading across the Á lftafjörður dyke swarm and govern a subhorizontal dextral shear component on the dyke planes during propagation. This interpretation is not in conflict with the left-stepping en echelon trend distribution of individual dykes relative to the trend of the swarm.

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“…The fractures in Ásbyrgi have been classified as fissures and tilted blocks. The proximity of the fissures to the fault and the prominent surface slope may possibly be interpreted as doming of the surface related to a subsurface dike intrusion, as described for similar structures by Tentler and Temperley (2007). However, in this model, a slope on both sides of the fractures is expected.…”

Section: Discussionmentioning

confidence: 68%

“…To avoid misinterpretations stemming from model tilt, possible slopes and artefacts have been ruled out by comparison with TanDEM-X WorldDEM ™ data. To more carefully review the point clouds created during the process and to take first test measurements, we used the Compass plugin (Thiele et al, 2017) for CloudCompare.…”

Section: Unmanned Aerial Vehicle Photogrammetrymentioning

confidence: 99%

Structure of massively dilatant faults in Iceland: lessons learned from high-resolution unmanned aerial vehicle data

et al. 2019

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Abstract. Normal faults in basalts develop massive dilatancy in the upper few hundred meters below the Earth's surface with corresponding interactions with groundwater and lava flow. These massively dilatant faults (MDFs) are widespread in Iceland and the East African Rift, but the details of their geometry are not well documented, despite their importance for fluid flow in the subsurface, geohazard assessment and geothermal energy. We present a large set of digital elevation models (DEMs) of the surface geometries of MDFs with 5–15 cm resolution, acquired along the Icelandic rift zone using unmanned aerial vehicles (UAVs). Our data present a representative set of outcrops of MDFs in Iceland, formed in basaltic sequences linked to the mid-ocean ridge. UAVs provide a much higher resolution than aerial/satellite imagery and a much better overview than ground-based fieldwork, bridging the gap between outcrop-scale observations and remote sensing. We acquired photosets of overlapping images along about 20 km of MDFs and processed these using photogrammetry to create high-resolution DEMs and orthorectified images. We use this dataset to map the faults and their damage zones to measure length, opening width and vertical offset of the faults and identify surface tilt in the damage zones. Ground truthing of the data was done by field observations. Mapped vertical offsets show typical trends of normal fault growth by segment coalescence. However, opening widths in map view show variations at much higher frequency, caused by segmentation, collapsed relays and tilted blocks. These effects commonly cause a higher-than-expected ratio of vertical offset and opening width for a steep normal fault at depth. Based on field observations and the relationships of opening width and vertical offset, we define three endmember morphologies of MDFs: (i) dilatant faults with opening width and vertical offset, (ii) tilted blocks (TBs) and (iii) opening-mode (mode I) fissures. Field observation of normal faults without visible opening invariably shows that these have an opening filled with recent sediment. TB-dominated normal faults tend to have the largest ratio of opening width and vertical offset. Fissures have opening widths up to 15 m with throw below a 2 m threshold. Plotting opening width versus vertical offset shows that there is a continuous transition between the endmembers. We conclude that for these endmembers, the ratio between opening width and vertical offset R can be reliably used to predict fault structures at depth. However, fractures associated with MDFs belong to one larger continuum and, consequently, where different endmembers coexist, a clear identification of structures solely via the determination of R is impossible.

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Magmatic fissures and their systems in Iceland: A tectonomagmatic model

Cited by 17 publications

References 61 publications

A record of eruption and intrusion at a fast spreading ridge axis: Axial summit trough of the East Pacific Rise at 9–10°N

A record of eruption and intrusion at a fast spreading ridge axis: Axial summit trough of the East Pacific Rise at 9–10°N

Magma flow and palaeo-stress deduced from magnetic fabric analysis of the Álftafjörður dyke swarm: implications for shallow crustal magma transport in Icelandic volcanic systems

Structure of massively dilatant faults in Iceland: lessons learned from high-resolution unmanned aerial vehicle data

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