A map series of the Southern East Pacific Rise and its flanks, 15� S to 19� S

Scheirer, Daniel S.; Macdonald, Ken C.; Forsyth, Donald W.; Miller, Stephen; Wright, Dawn J.; Cormier, Marie-Hélène; Weiland, C.

doi:10.1007/bf00286201

Cited by 51 publications

(36 citation statements)

References 32 publications

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“…(g) Cross-sections along the axis showing seafloor depth from multibeam bathymetry data and the base of layer 2A, and the AML imaged in multi-channel seismic data (Hooft et al 1997). Short vertical arrows mark locations of third-order discontinuities from Scheirer et al (1996). , 2002Smith et al 2001;Sims et al 2002).…”

Section: Geochemical Properties At Discontinuities and Along Ridge Sementioning

confidence: 99%

Tectonic and magmatic segmentation of the Global Ocean Ridge System: a synthesis of observations

Carbotte

Smith

Cannat

et al. 2015

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Mid-ocean ridges display tectonic segmentation defined by discontinuities of the axial zone, and geophysical and geochemical observations suggest segmentation of the underlying magmatic plumbing system. Here, observations of tectonic and magmatic segmentation at ridges spreading from fast to ultraslow rates are reviewed in light of influential concepts of ridge segmentation, including the notion of hierarchical segmentation, spreading cells and centralized v. multiple supply of mantle melts. The observations support the concept of quasi-regularly spaced principal magmatic segments, which are 30-50 km long on average at fast-to slow-spreading ridges and fed by melt accumulations in the shallow asthenosphere. Changes in ridge properties approaching or crossing transform faults are often comparable with those observed at smaller offsets, and even very small discontinuities can be major boundaries in ridge properties. Thus, hierarchical segmentation models that suggest large-scale transform fault-bounded segmentation arises from deeper level processes in the asthenosphere than the finer-scale segmentation are not generally supported. The boundaries between some but not all principal magmatic segments defined by ridge axis geophysical properties coincide with geochemical boundaries reflecting changes in source composition or melting processes. Where geochemical boundaries occur, they can coincide with discontinuities of a wide range of scales.Discovery and interpretations of mid-ocean ridge (MOR) segmentation: historical review

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Section: Geochemical Properties At Discontinuities and Along Ridge Sementioning

confidence: 99%

Tectonic and magmatic segmentation of the Global Ocean Ridge System: a synthesis of observations

Carbotte

Smith

Cannat

et al. 2015

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“…On the fast spreading EPR, abyssal hill relief has been interpreted as a fault-bounded horst and graben terrain formed during horizontal extension of the lithosphere at the ridge axis [Lonsdale, 1977;Macdonald, 1982;Searle, 1984]. The volcanic draping of outward facing slopes on the EPR reported by Macdonald et al [ 1996] will produce slopes with a volcanic surficial morphology, although the underlying architecture is fault-controlled. In comparison, on the intermediate spreading ridges abyssal hills appear to be backtilted blocks bounded by faults on their axis-facing sides with gently dipping, volcanic, outward facing slopes [Klitgord and Mudie, 1974;Kappel and Ryan, 1986].…”

Section: Abyssal Hill Topographymentioning

confidence: 99%

Contribution of volcanism and tectonism to axial and flank morphology of the southern East Pacific Rise, 17°10′–17°40′S, from a study of layer 2A geometry

Carbotte¹,

Mutter²,

Xu³

1997

J. Geophys. Res.

105

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Abstract. Multichannel seismic images from the East Pacific Rise 17ø10 '-17ø40'S are used to study the geometry of seismic layer 2A in the near-axis region. Wave-exluafion datuming is applied to stacked common midpoint data to remove the distorting effects of seafloor topography on the layer 2A event. Processed stacks are compared with seafloor morphology and tectonic fabric imaged in side-scan sonar data. Assuming layer 2A corresponds with the extmsive crust, these data are usexi to study the relationship between volcanism and tectonism in the accumulation of the extmsive layer and to assess the contribution of extrasives to ridge-crest and ridge-flank morphology. We find variations in axial thickening of layer 2A which imply twofold variation in the width of the extmsive layer accumulation zone, as well as systematic changes in the pattern of accumulation of this layer. On the ridge flanks the layer 2A horizon mimics abyssal hill relief, consistent with a horst and graben origin for this topography. Short-wavelength variations in the thickness of layer 2A are superimposed on this relief, which we attribute to volcanic modification of tectonic topography at the edge of the neovolcanic zone. The integrated off-axis thickness of layer 2A is correlatexl with ridge cross-sectional area and indicates persistent (100,000 years) spatial gradients in extmsive layer thickness. Systematic changes in the cross-axis shape of the ridge, observed over distances of 5-10 km, cannot be attributed to the extmsive layer, and it appears that axial structure beneath the volcanics governs the cross-axis morphology of the ridge.

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“…This area has been extensively mapped [Scheirer et al, 1996], and was the focus of two submersible dive programs [Renard et al, 1985;Auzende et al, 1996], a detailed seismic refraction/reflection survey (TERA) , and the Mantle ELectromagnetic and Tomographic (MELT)…”

Section: The Study Areamentioning

confidence: 99%

Seismic and magnetic constraints on the structure of upper oceanic crust at fast and slow spreading ridges

Hussenoeder¹

1998

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The upper ocean crust contains a comprehensive record of the shallow geological processes active along the world's mid-ocean ridge system. This thesis examines the magnetic and seismic structure of the upper crust at two contrasting ridges-the fast spreading East Pacific Rise (EPR) and the slow spreading Mid-Atlantic Ridge (MAR)-to build a more complete understanding about the roles of volcanic emplacement, tectonic disruption and hydrothermal alteration in the near-ridge environment.A technique that inverts potential field measurements. directly from an uneven observation track is developed and applied to near-bottom magnetic data from the spreading segments north of the Kane transform on the MAR. It is concluded that the central anomaly magnetization high marks the locus of focused volcanic emplacement. A cyclic faulting model is proposed to explain the oscillatory magnetization pattern associated with discrete blocks of crust being transported out of the rift valley between intensely altered fault zones. Seismic waveform and amplitude analyses of the magma sill along the EPR reveal it to be a thin «100 m) body of partial melt. These characteristics have important implications for melt availability and transport within the cycle of eruption and replenishment. A genetic algorithm-based seismic waveform inversion technique is developed and applied to on-and near-axis multichannel data from 17°20 's on the EPR and the spreading segment south of the Oceanographer transform (MAR) to map and compare for the first time the detailed velocity structure of the upper crust at two different spreading rates. Combined with conventionally processed seismic profiles, our results show that, while final extrusive thickness is comparable at all spreading ridges (300-500 m), the style of thickening may vary. While a thin (:S100 m) extrusive carapace quadruples in thickness within 1-4 km of the EPR crest, the extrusive section at the MAR achieves its final thickness within the inner valley. Both show evidence for a narrow zone of volcanic emplacement. Vigorous hydrothermalism at the EPR may produce a more rapid increase in basement velocities relative to the MAR. Rapid modification of the extrusive/dike transition at both ridges indicates that hydrothermalism is enhanced in this interval. Along-axis transport of lavas may thicken the extrusive pile at slow spreading segment ends, strengthening the magnetic highs generated by lava chemistry. Biographical SketchIn order to wax only partially rhapsodic, let me start at my formative age as a marine geophysicist ... the age of six. The first hint that I wasn't going to grow up to be a successful businessman was dropped in Germany, where my best friend and I rejected the idea of opening a lemonade stand in favor of selling fossils and geodes on the street corner. We soon went bankrupt. Our village in southern Germany was not far from Solnhofen, home of the famed Archaeopteryx. The countryside was full of geological treasures exposed in streambeds or along roadsides. Our final m...

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A map series of the Southern East Pacific Rise and its flanks, 15� S to 19� S

Cited by 51 publications

References 32 publications

Tectonic and magmatic segmentation of the Global Ocean Ridge System: a synthesis of observations

Tectonic and magmatic segmentation of the Global Ocean Ridge System: a synthesis of observations

Contribution of volcanism and tectonism to axial and flank morphology of the southern East Pacific Rise, 17°10′–17°40′S, from a study of layer 2A geometry

Seismic and magnetic constraints on the structure of upper oceanic crust at fast and slow spreading ridges

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