Segmentation and a nontransform ridge offset on the Reykjanes Ridge near 58°N

Searle, R. C.; Field, Paul R.; Owens, Robin

doi:10.1029/94jb01549

Cited by 26 publications

(23 citation statements)

References 42 publications

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“…1995a, b). They are similar in shape to seamounts near the axis of the East Pacific Rise (Searle 1983;Fornari et al 1987), but fall in the lower end of that size spectrum. The texture seen on TOBI sidescan shows an evolution with age: compare the 'nested' seamounts ( Fig.…”

Section: Constructional Terrainsmentioning

confidence: 76%

“…It comprises a conglomeration of myriad, circular mounds, whose diameters range from a few tens of metres to about 500 m. The geometry of the shadows indicates that they are usually less than 50 m high, have rounded summits and no summit craters. TOBI data from the Reykjanes Ridge (Magde & Smith 1995;Mutton & Parson 1993;Parson et al 1993;Searle et al 1994) and elsewhere on the Mid-Atlantic Ridge between 24 ~ and 30~ (Smith et al 1995a, b) show AVRs comprising a similar terrain. Our camera runs (Figs 4 & 5), which are described more fully below, showed that each hummock usually corresponds to an individual pillow flow, with the steep fronts and shallower tops of the flows causing the hummocky morphology.…”

Section: Constructional Terrainsmentioning

confidence: 99%

“…Studies from the Pacific have often located areas of satellite cones and lava fields around the base of seamounts (Batiza & Vanko 1983;Searle 1983). Satellite volcanism is thought to play an important part in the subsequent development of a seamount's summit plateau (Fornari et al 1984).…”

Section: Constructional Terrainsmentioning

confidence: 99%

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Detailed volcanic geology of the MARNOK area, Mid-Atlantic Ridge north of Kane transform

Lawson

Searle

Pearce

et al. 1996

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We present the results of a detailed study of the volcanic geology of the median valley floor of the Mid-Atlantic Ridge in two adjacent but contrasting spreading segments immediately north of the Kane transform fault, based on a high-resolution deep-towed sidescan sonar (TOBI) survey, near-bottom photographic traverses, and geochemical analyses from 28 precisely sited sets of dredge samples. This has allowed us to assess the relative importance of small (intersegment) and large (transform) boundaries on magmatic processes at slow spreading ridges.We find that the petrological effect of the transform (so-called 'transform fault effect') is minor compared to the manifestation of the second-order segmentation. The southern, 'narrowgate'-type segment has a poorly developed neovolcanic zone, which tapers towards its bathymetric centre where continuous faulting causes rapid dismemberment. Flat-topped seamounts are preferentially located at the ends of the segment, particularly near the non-transform offset. There is a striking variation in the degree of fractionation along the length of this segment: primitive lavas were sampled at the centre, while more fractionated basalts, showing a greater range of parental compositions, form discrete volcanic edifices at the ends. In contrast, the northern segment has a wider inner valley, and syn-magmatic faults extend up to 15km along the crest of its robust axial volcanic ridge. The along-segment trend of increasing MgO towards the bathymetric crest of the axial volcanic ridge is similar to, but less well-defined than, that for the southern segment.There is no variation in the bulk degree of melting along the segments as determined from the major element geochemistry; hence, melt migration is favoured over focused mantle upwelling as the main cause of the crustal thickness variations which define second-order segmentation. Radiogenic isotopes show only very small variations with no systematic pattern emerging within or between the ridge segments. The isotopic irregularities are not related to the variations in incompatible elements, implying that the latter result from dynamic melting processes rather than from long-lived source heterogeneity. A model is developed which relates the volcanology, tectonic style and the geochemical trends to the episodicity of magma supply and eruption.

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Section: Constructional Terrainsmentioning

confidence: 76%

Section: Constructional Terrainsmentioning

confidence: 99%

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Detailed volcanic geology of the MARNOK area, Mid-Atlantic Ridge north of Kane transform

Lawson

Searle

Pearce

et al. 1996

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“…The basins are thought to represent non-transform ridge offsets Huestis and Acton, 1997;Searle et al, 1994Searle et al, , 1998.…”

Section: Ridge Segmentationmentioning

confidence: 99%

The Reykjanes Ridge between 63°10′N and Iceland

Höskuldsson

Hey

Kjartansson

et al. 2007

Journal of Geodynamics

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“…Murton & Parson 1993;Searle et al 1994;Keeton et al 1997, and see Fig. Murton & Parson 1993;Searle et al 1994;Keeton et al 1997, and see Fig.…”

Section: Introductionmentioning

confidence: 96%

The RAMESSES experiment-V. Crustal accretion at axial volcanic ridge segments-a gravity study at 57°45′N on the slow spreading Reykjanes Ridge

Peirce

Navin

2002

Geophysical Journal International

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Summary Presented in this paper are the results of a two‐stage analysis of gravity data acquired during a multidisciplinary geophysical survey of a magmatically active axial volcanic ridge (AVR) segment located at 57°45′N on the Reykjanes Ridge, part of the slow spreading Mid‐Atlantic Ridge south of Iceland. Modelling of the free‐air anomaly in 2‐D shows that, across‐axis, the observed anomaly results largely from density and layer thickness variation in the mid‐lower crust. Although seismic control on crustal thickness along‐axis is limited, modelling also suggests that both crustal density and thickness also vary towards AVR tips. Using the 2‐D modelling results as crustal reference, the residual mantle Bouguer anomaly (RMBA) is calculated to assess whether magma‐related density anomalies are present in the mantle and to investigate the structure of, and relationship between, adjacent AVRs along‐axis. RMBA lows are associated with both an along‐ridge trend encompassing a number of adjacent AVRs and with individual, more topographically robust AVRs. Modelling of the RMBA low associated with the 57°45′N AVR further suggests that along‐axis density variation is confined to the central region of this AVR and that the anomaly can largely be accounted for by density variation within Layer 3 and a degree of crustal thinning towards AVR tips. The nature of the along‐axis variation in crustal density further suggests that it may result from repeated phases of magma supply to the crustal system from the mantle. Within the resolution of the RMBA, modelling does not confirm or preclude the presence of a subcrustal density anomaly associated with retention of a small percentage of melt in the mantle. However, a melt‐free model for at least the top 40 km of the mantle is preferred as this is consistent with the results of modelling a coincident magnetotelluric data set. The ridge‐trend characteristics of the RMBA also suggest that magma delivery may take place along this trend, and in an episodic fashion that controls initiation of an AVR tectonomagmatic cycle. AVRs may, therefore, be created along a spreading‐orthogonal direction by tapping of a recent magma injection into the ridge‐trending crustal system, with flow of this magma laterally along AVR‐parallel faults and fissures accommodating spreading and crustal accretion.

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Segmentation and a nontransform ridge offset on the Reykjanes Ridge near 58°N

Cited by 26 publications

References 42 publications

Detailed volcanic geology of the MARNOK area, Mid-Atlantic Ridge north of Kane transform

Detailed volcanic geology of the MARNOK area, Mid-Atlantic Ridge north of Kane transform

The Reykjanes Ridge between 63°10′N and Iceland

The RAMESSES experiment-V. Crustal accretion at axial volcanic ridge segments-a gravity study at 57°45′N on the slow spreading Reykjanes Ridge

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