The Reykjanes Ridge: structure and tectonics of a hot-spot-influenced, slow-spreading ridge, from multibeam bathymetry, gravity and magnetic investigations

Searle, R. C.; Keeton, Jane A.; Owens, Robin; White, R. S.; Mecklenburgh, R.; Parsons, B.; Lee, S.M

doi:10.1016/s0012-821x(98)00104-6

Cited by 98 publications

(109 citation statements)

References 49 publications

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“…Since this segment is closest to the volcanic arc and the MBA low of the segment center continues to the Mariana Ridge, these observations lead us an interpretation that this segment receives extra magma delivery from the volcanic front. Similar changes of topography and gravity are observed in segments of the MAR approaching to the Azores hot spot [Detrick et al, 1995;Thibaud et al, 1998] and the Iceland hot spot [Bell and Buck, 1992;Searle et al, 1998]. On the basis of chemical compositions of basalts obtained from the northern part of the trough between 21°N and 22°N, Stern et al [1990] estimated a mixing of 50-90% Mariana arc component with a mid-ocean ridge basalt (MORB) component.…”

Section: Discussionmentioning

confidence: 64%

Spreading process of the northern Mariana Trough: Rifting‐spreading transition at 22°N

Yamazaki

Seama

Okino

et al. 2003

Geochem Geophys Geosyst

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[1] We have conducted a geophysical survey of the northern Mariana Trough from 19°N to 24°N. The trough evolves southward from incipient rifting to seafloor spreading within this region. This study aims to clarify the location and time of the rifting-to-spreading transition, which was controversial previously, and processes of seafloor spreading after the transition. The new data set includes swath bathymetry with sidescan images and magnetic vector anomaly. The mantle Bouguer gravity anomaly (MBA) was calculated using the free-air gravity anomaly from satellite altimetry. The rifting-to-spreading transition occurs at about 22°N, which is proved by seafloor-spreading fabric in the bathymetry, clear magnetic lineations, and the bull's-eye pattern in MBA. Four ridge segments separated by three nontransform discontinuities are recognized between 19°N and 22°N. The northernmost segment has relatively abundant magma supply compared with the other segments, which is estimated from a larger segment length, shallower axial depths with no rift valley, and lower MBA. The next segment to the south is, on the other hand, a magma-starved segment with a prominent rift valley. Two anomalously deep grabens (called the Central Grabens) formed by amagmatic extension occur near the segment ends. The succession of magma-rich, magma-starved, and normal segments with increasing distance from the volcanic arc is the same as the observation in the Lau Basin reported by Martinez and Taylor spreading center have been significantly larger than the eastern counterpart in general. The asymmetry may have been caused by an interaction of mantle upwelling systems under the volcanic front and the backarc spreading center and would be a characteristic of backarc spreading.

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Section: Discussionmentioning

confidence: 64%

Spreading process of the northern Mariana Trough: Rifting‐spreading transition at 22°N

Yamazaki

Seama

Okino

et al. 2003

Geochem Geophys Geosyst

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“…This phenomenon is also described for volcanic structures on the Reykjanes Ridge where high aspect-ratio axial volcanic ridges (AVR's) strike perpendicular to the extensional strain direction at their mid-points but bend towards a more rift-parallel strike at their tips (Searle et al 1998;Höskuldsson et al 2007), giving the AVRs an overall S-shaped geometry. This geometry is reproduced in numerical models of oblique (2007), which show that the principle stresses rotate between the axial rift zone and the surrounding lithosphere as a result of the weaker material within the axial zone attributed to differences in thermal properties of the crust.…”

Section: Discussionmentioning

confidence: 82%

“…The structural influence of topography has been observed and modeled in volcanic areas as diverse as Madeira (Klügel et al 2005) and Hawaii (Walter and Amelung 2006) and has been modeled by Pinel and Jaupart (2004) and Gaffney and Damjanac (2006). Numerous studies on the oblique Reykjanes Ridge have noted that the strike of both faults and axial volcanic ridges (AVRs) changes from spreading perpendicular to ridge-parallel with distance from the axial zone of the ridge (Searle et al 1998;Höskuldsson et al 2007;Peirce and Sinha 2008). This behavior has been modeled by Tuckwell et al (1998) van Wijk andBlackman (2007) and also documented for faults on the RP (Nakamura 1970;Clifton and Schlische 2003;Clifton and Kattenhorn 2006).…”

Section: Introductionmentioning

confidence: 99%

Controls on the geometry of a Holocene crater row: a field study from southwest Iceland

Jenness¹,

Clifton

2009

Bull Volcanol

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The Reykjanes Peninsula rift zone in southwest Iceland is a highly oblique segment of the Mid-Atlantic ridge system which accommodates NW-SE extension during rifting episodes that consist of eruptions and normal faulting, and E-W left-lateral shear strain along strike-slip faults during longer amagmatic periods. Dominant tectonic features on the peninsula are a series of generally NEstriking, sub-parallel eruptive fissures and normal faults, and a cross-cutting zone of N-S striking, right-lateral strike-slip faults. The last series of rifting episodes ended in 1227, and a proposed 1,000 year cyclicity predicts the start of a new series of eruptions within the next 200 years. In order to more accurately characterize the nature of eruptions on the Reykjanes Peninsula, we present a new, spatially accurate map of the ∼2,350 year old Sundhnúkur crater row in the western part of the peninsula, which was examined in detail in order to determine the structural controls on crater row geometry and to understand the interactions that take place between eruptive fissures and pre-existing geological structures. Volcanism is sometimes influenced by small perturbations in the surroundings such as gravitational loading, topography, changes in crustal properties or the presence of fault zones, but there are few field examples showing how fissures are influenced by these pre-existing structures. We identify 27 fissure segments, ranging in strike from 006°to 053°, with varying spacing and overlap between them. Significant local variability in strike and stepping sense of segments occurs in proximity to topographic highs as well as within zones of faulting that pre-date the crater row. Strike also varies at the northern end of the crater row as it approaches a region of older crust at the rift margin. Our data support numerical and laboratory modeling results which show that local topography, pre-existing fractures and crustal properties influence the path taken by magma on its way through the shallow crust.

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“…Rifted spreading centers, typical of the Mid-Atlantic Ridge, transition to axial morphologies more typical of faster spreading ridges with smooth, elevated forms proximal to Iceland (Searle et al 1998). Oceanic crust formed on the Kolbeinsey and Reykjanes Ridges to the north and south of Iceland thickens toward Iceland reflecting elevated mantle temperatures of the hotspot (Hooft et al 2006).…”

Section: Northeast Atlantic Crustal Structurementioning

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 Reykjanes Ridge: structure and tectonics of a hot-spot-influenced, slow-spreading ridge, from multibeam bathymetry, gravity and magnetic investigations

Cited by 98 publications

References 49 publications

Spreading process of the northern Mariana Trough: Rifting‐spreading transition at 22°N

Spreading process of the northern Mariana Trough: Rifting‐spreading transition at 22°N

Controls on the geometry of a Holocene crater row: a field study from southwest Iceland

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

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