The Iceland Plate Boundary Zone: Propagating Rifts, Migrating Transforms, and Rift‐Parallel Strike‐Slip Faults

Karson, Jeffrey A.

doi:10.1002/2017gc007045

Cited by 34 publications

(49 citation statements)

References 86 publications

(143 reference statements)

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“…Fault slip and block rotations at propagating rifts. (a) Schematic diagram showing crustal block rotations and predicted rift‐parallel strike‐slip faults with respect to propagating Icelandic rift zones (Karson, ). Large‐scale crustal block rotations occur by distributed slip on rift‐parallel strike‐slip faults.…”

Section: Discussionmentioning

confidence: 99%

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Rift‐Parallel Strike‐Slip Faulting Near the Iceland Plate Boundary Zone: Implications for Propagating Rifts

Karson

Farrell

Chutas³

et al. 2018

Tectonics

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Strongly lineated terrain outside of Iceland's active plate boundary zones is created by faults and dikes aligned with the rift zones where they formed, similar to the spreading fabric defined by abyssal hills generated at mid‐ocean ridge spreading centers. As expected, rift‐parallel normal faults and fissures dominate in the active rift zones, but in older crust to the east and west, faults with strike‐slip and oblique‐slip displacements dominate. Some areas have widespread, small‐scale, strike‐slip, and oblique‐slip faults, while others have more widely spaced, larger, strike‐slip fault zones. In most cases, the strike‐slip and oblique‐slip faults strike subparallel to nearby older dikes and normal faults assumed to indicate the orientation of the rift zones where they formed. Strike‐slip displacements overprinting normal faults and along dike margins suggest reactivation of spreading‐related zones of weakness. More complicated fault geometries and kinematics occur near the oblique rifts and the major transform fault zones. The sense of movement on the strike‐slip and oblique‐slip faults is broadly systematic with respect to the active Northern and Eastern Rift Zones supporting the interpretation that they are the result of crustal block rotations on either side of rift zones that propagate to the north and south away from the center of the Iceland hot spot. Similar fault kinematics may occur along mid‐ocean ridges and other magmatic rifts where rift propagation occurs on a range of scales.

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Section: Discussionmentioning

confidence: 99%

“…This might result in faults with oblique-slip displacements or strain partitioned between normal and strike-slip faults. The current plate (Karson, 2017). Large-scale crustal block rotations occur by distributed slip on rift-parallel strike-slip faults.…”

Section: 1029/2018tc005206mentioning

confidence: 99%

Rift‐Parallel Strike‐Slip Faulting Near the Iceland Plate Boundary Zone: Implications for Propagating Rifts

Karson

Farrell

Chutas³

et al. 2018

Tectonics

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“…Models of GPS data support this hypothesis—two thirds of present‐day plate motion is accommodated on the northeastern‐most Grímsey fault with only a third on the central Húsavík‐Flatey fault (Metzger et al, ). This transfer process may be linked to the northward propagation of the Northern Volcanic Zone (Karson, ; Sæmundsson, ).…”

Section: Tectonic Settingmentioning

confidence: 99%

“…These transform fault systems formed in response to ridge migration, as the axial rift system on Iceland stepped eastward to stay above the deep‐seated mantle plume (Burke et al, ; Lawver & Müller, ). The regions where faults and rifts connect have complex patterns of deformation in both space and time, especially between overlapping but simultaneously active rift segments (e.g., Foulger, ; Gudmundsson et al, ; Hackman et al, ; Karson, ; Khodayar & Franzson, ; LaFemina et al, ; Perlt & Heinert, ).…”

Section: Introductionmentioning

confidence: 99%

Distributed Deformation in an Oceanic Transform System: Applying Statistical Tools to Structural and Paleomagnetic Data Near the Húsavík‐Flatey Fault, Northern Iceland

et al. 2018

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The right-lateral Húsavík-Flatey fault is part of the Tjörnes Fracture Zone, which links the offshore and onshore rift axes in northern Iceland. There has been debate about whether rocks near this fault have accommodated distributed off-fault deformation, which is testable using paleomagnetic data. Recent studies from Flateyjarskagi show clockwise declination deflections that are largest near the fault. We augment these data with new structural and paleomagnetic measurements from 106 lava flows across three peninsulas-Flateyjarskagi, Tröllaskagi, and Tjörnes-also finding clockwise deflections that vary with distance from the fault. To test whether the deflections could be caused by off-fault deformation, we combine our measurements with other regional data sets, applying several statistical tools including regressions of structural or paleomagnetic directions versus fault-normal distance. To evaluate the significance and uncertainties of the regressions, we use permutation tests and bootstrapping. For Flateyjarskagi, our analysis suggests that lavas and dikes were deformed together; the regression results predict 4 ∘ -6 ∘ of rotation per kilometer about a steep, but not vertical, axis. Rocks on Tröllaskagi hint at similar spatial patterns with fault distance, but the data quality precludes a full analysis. Rocks on Tjörnes show no spatial patterns, but they preserve a temporal history, where rotation seems to have ceased after deposition of the Pliocene-age Tjörnes beds. Using constraints from our statistical analyses, geochronology, and comparisons with the transform system in southern Iceland, we propose several modifications to models for the evolution of axial rift zones in northern Iceland.

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“…Divergence between these crustal blocks may account for the poorly known Central Rift Zone (CRZ) that extends westward from the Iceland hotspot toward the Snaefellsnes Volcanic Zone (Fig. 4) (Karson 2015(Karson , 2016.…”

Section: Upper Crust Of Icelandmentioning

confidence: 99%

Crustal accretion of thick mafic crust in Iceland: implications for volcanic rifted margins

Karson

2016

Can. J. Earth Sci.

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Rifting near hotspots results in mantle melting to create thick mafic igneous crust at volcanic rifted margins (VRMs). This mafic crust is transitional between rifted continental crust with mafic intrusions landward and oceanic crust into which it grades seaward. Seismic velocities, crustal drilling, and exhumed margins show that the upper crust in these areas is composed of basaltic lava erupted in subaerial to submarine conditions intruded by downward increasing proportions of dikes and sparse gabbroic intrusions. The lower crust of these regions is not exposed but is inferred from seismic velocities (Vp > 6.5 km/sec) and petrological constraints to be gabbroic to ultramafic in composition. Limited access to crustal sections generated along VRMs have raised questions regarding the composition and structure of this transitional crust and how it evolves during the early stages of rifting and subsequent seafloor spreading. Active processes in Iceland provide a glimpse of subaerial spreading with the creation of a thick (40-25 km) mafic igneous crust that may be analogous to the transitional crust of VRMs. Segmented rift zones that propagate away from the Iceland hotspot, migrating transform fault zones, and rift-parallel strike-slip faults create a complex plate boundary zone in the upper, brittle crust. These structures may be decoupled from underlying lower crustal gabbroic rocks that are capable of along-axis flow that smooths-out crustal thickness variations. Similar processes may be characteristic of the early history of VRMs and volcanic hotspot ridges related to rifting and seafloor spreading proximal to hotspots. Résumé :De la distension à proximité de points chauds génère une fusion du manteau créant une épaisse croûte ignée mafique aux marges de divergence des volcans (VRM). Cette croûte mafique constitue une transition entre la croûte continentale de divergence comportant des intrusions mafiques du côté continental et la croûte océanique dans laquelle elle s'intègre vers le large. Les vitesses sismiques, les forages dans la croûte et les bordures exhumées montrent que, dans ces secteurs, la croûte supérieure est composée de lave basaltique ayant fait éruption sous des conditions subaériennes à sous-marines et elle a été pénétrée par des intrusions gabbroïques éparses et des dykes dont les proportions augmentent vers le bas. La croûte inférieure de ces régions n'affleure pas mais selon les vitesses sismiques (Vp > 6,5 km/sec) et les contraintes pétrologiques elle serait de composition gabbroïque à ultramafique. L'accès limité aux sections de la croûte générées le long des VRM a soulevé des questions quant à la composition et la structure de cette croûte de transition et de son évolution durant les premiers stades de distension et d'étalement subséquent du plancher océanique. Des processus actifs en Islande fournissent un aperçu de l'étalement subaérien avec la création d'une épaisse (40-25 km) croûte ignée mafique qui pourrait être analogue à la croûte de transition des VRM. Des zones de rift ...

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The Iceland Plate Boundary Zone: Propagating Rifts, Migrating Transforms, and Rift‐Parallel Strike‐Slip Faults

Cited by 34 publications

References 86 publications

Rift‐Parallel Strike‐Slip Faulting Near the Iceland Plate Boundary Zone: Implications for Propagating Rifts

Rift‐Parallel Strike‐Slip Faulting Near the Iceland Plate Boundary Zone: Implications for Propagating Rifts

Distributed Deformation in an Oceanic Transform System: Applying Statistical Tools to Structural and Paleomagnetic Data Near the Húsavík‐Flatey Fault, Northern Iceland

Crustal accretion of thick mafic crust in Iceland: implications for volcanic rifted margins

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