Three‐dimensional shallow crustal emplacement at the 9°03′N overlapping spreading center on the East Pacific Rise: Correlations between magnetization and tomographic images

Bazin, Sara; Harding, A. J.; Kent, G. M.; Orcutt, John A.; Tong, C. H.; Pye, J. W.; Singh, S. C.; Barton, P. J.; Sinha, M. C.; White, R. S.; Hobbs, R. W.; Avendonk, H. J. Van

doi:10.1029/2001jb000371

Cited by 37 publications

(58 citation statements)

References 79 publications

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“…It has been the focus of several geophysical studies (Detrick et al, 1987;Harding et al, 1993;Kent et al, 1993Kent et al, , 2000Bazin et al, 2001;Dunn et al, 2001;Tong et al, 2002), which have produced the first 3D multi-channel seismic survey of a mid-ocean ridge (Kent et al, 2000) and a 3D seismic refraction study (Dunn et al, 2001). These studies reveal shallow melt lenses beneath both limbs of the OSC and in the interlimb region north of the overlap basin (Kent et al, 2000).…”

Section: Geologic Settingmentioning

confidence: 99%

Volatile abundances and oxygen isotopes in basaltic to dacitic lavas on mid-ocean ridges: The role of assimilation at spreading centers

et al. 2011

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a b s t r a c t a r t i c l e i n f oMost geochemical variability in MOR basalts is consistent with low-to moderate-pressure fractional crystallization of various mantle-derived parental melts. However, our geochemical data from MOR highsilica glasses, including new volatile and oxygen isotope data, suggest that assimilation of altered crustal material plays a significant role in the petrogenesis of dacites and may be important in the formation of basaltic lavas at MOR in general. MOR high-silica andesites and dacites from diverse areas show remarkably similar major element trends, incompatible trace element enrichments, and isotopic signatures suggesting similar processes control their chemistry. In particular, very high Cl and elevated H 2 O concentrations and relatively light oxygen isotope ratios (~5.8‰ vs. expected values of~6.8‰) in fresh dacite glasses can be explained by contamination of magmas from a component of ocean crust altered by hydrothermal fluids. Crystallization of silicate phases and Fe-oxides causes an increase in δ 18 O in residual magma, but assimilation of material initially altered at high temperatures results in lower δ 18 O values. The observed geochemical signatures can be explained by extreme fractional crystallization of a MOR basalt parent combined with partial melting and assimilation (AFC) of amphibole-bearing altered oceanic crust. The MOR dacitic lavas do not appear to be simply the extrusive equivalent of oceanic plagiogranites. The combination of partial melting and assimilation produces a distinct geochemical signature that includes higher incompatible trace element abundances and distinct trace element ratios relative to those observed in plagiogranites.

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Section: Geologic Settingmentioning

confidence: 99%

Volatile abundances and oxygen isotopes in basaltic to dacitic lavas on mid-ocean ridges: The role of assimilation at spreading centers

et al. 2011

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“…These data were obtained by multibeam (and microbeam) bathymetry, side-scan sonar, and remotely operated vehicle (ROV) and autonomous underwater vehicle (AUV), and submersible dive data [e.g., Wright et al, 1995;Embley et al, 1998;Kurras et al, 2000;Scheirer et al, 2000;White et al, 2000;Bazin et al, 2001;White et al, 2002;Cormier et al, 2003;Fornari et al, 2004;Soule et al, 2005Soule et al, , 2007Stakes et al, 2006;Escartín et al, 2007;Ferrini et al, 2007;Soule et al, 2009;White et al, 2009]. These observations indicate that the evolution of EPR submarine lava flows is analogous to the down-flow transition of subaqueous lava flows observed on the Hawaiian Islands, where lava flows evolve from proximal sheet flows, to lobates, to pillows [e.g., Soule et al, 2004;Fornari et al, 2004].…”

Section: East Pacific Rise Lava Flowsmentioning

confidence: 99%

Lava deposition history in ODP Hole 1256D: Insights from log‐based volcanostratigraphy

Tominaga

Umino

2010

Geochem Geophys Geosyst

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[1] A log-based volcanic stratigraphy of Ocean Drilling Program Hole 1256D provides a vertical crosssection view of in situ upper crust formed at the East Pacific Rise (EPR) with unprecedented resolution. This stratigraphy model comprises ten electrofacies, principally identified from formation microscanner images. In this study, we build a lava flow stratigraphy model for the extrusive section in Hole 1256D by correlating these electrofacies with observations of flow types from the modern EPR, such as sheet flows and breccias, and pillow lavas and their distribution. The resulting flow stratigraphy model for the Hole 1256D extrusive section represents the first realization of detailed in situ EPR upper oceanic crust construction processes that have been detected only indirectly from remote geophysical data. We correlated the flow stratigraphy model with surface geology observed from the southern EPR (14°S) by Shinkai 6500 dives in order to obtain the relationship between lava flow types and ridge axis-ridge slope morphology. This dive information was also used to give a spatial-time reference frame for modeling lava deposition history in Hole 1256D. In reconstructing the lava deposition history, we interpreted that the origins of the ∼100 m thick intervals with abundant pillow lavas in Hole 1256D are within the axial slope where pillow lavas were observed during the Shinkai 6500 dives and previous EPR surveys. This correlation could constrain the lava deposition history in Hole 1256D crust. Using the lateral scale of ridge axis-ridge slope topography from the Shinkai 6500 observations and assuming the paleospreading rate was constant, 50% of the extrusive rocks in Hole 1256D crust were formed within ∼2000 m of the ridge axis, whereas nearly all of the remaining extrusive section was formed within ∼3000 m of the ridge axis. These results are consistent with the upper crustal construction model previously suggested by seismic studies.

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“…The Anatomy of a Ridge Axis Discontinuity (ARAD) experiment [ Singh et al , 1999], which was conducted in 1997 on board R/V Maurice Ewing , provided a large volume of refraction and reflection seismic data across the 9°03′N OSC: Kent et al [2000] propose a melt supply mechanism at the OSC by presenting images of interpreted melt runnels in the vicinity of the eastern melt sill. By correlating seismic velocity images and results from magnetic analysis, Bazin et al [2001] interpret the region of thick layer 2A at the tip of the propagating spreading limb and beneath the overlap basin as the result of a long period of extrusive accumulation. Tong et al [2002] study the geometry of the asymmetric melt sills and vertical sections from a seismic velocity model and propose a possible self‐decapitation model of the neovolcanic axis that may explain the morphologic evolution of the propagating eastern limb.…”

Section: Geologic Setting and Motivationmentioning

confidence: 99%

“…This small misfit is consistent with the suspension of hydrophones above the seafloor (∼10 m), with smoothing applied to the swath bathymetry data and pick uncertainties of the direct arrivals in the water layer. The Scripps OBHs were relocated by minimizing the travel time misfit of direct arrivals and by modeling the wave velocity in the water layer with an estimated accuracy of 5 m in the horizontal relocated position [ Bazin et al , 2001]. The smaller uncertainties for the Scripps OBHs are due to differences in relocation procedures and higher sampling frequency of the OBHs (4 ms rather than 7.8 ms).…”

Section: Data Processing and Analysismentioning

confidence: 99%

Influence of enhanced melt supply on upper crustal structure at a mid‐ocean ridge discontinuity: A three‐dimensional seismic tomographic study of 9°N East Pacific Rise

et al. 2003

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[1] We present a three-dimensional upper crustal model of the 9°03 0 N overlapping spreading center (OSC) on the East Pacific Rise that assists in understanding the relationship between melt sills and upper crustal structure at a ridge discontinuity with enhanced melt supply at crustal levels. Our P wave velocity model obtained from tomographic inversion of $70,000 crustal first arrival travel times suggests that the geometry of extrusive emplacement are significantly different beneath the overlapping spreading limbs. Extrusive volcanic rocks above the western melt sill are inferred to be thin ($250 m). More extensive accumulation of extrusives is inferred to the west than to the east of the western melt sill. The extrusive layer inferred above the eastern melt sill thickens from $350 (at the neovolcanic axis) to 550 m (to the west of the melt sill). Volcanic construction is likely to be significant in the formation of ridge crest morphology at the OSC, particularly at the tip of the eastern limb. On the basis of our interpretation of the velocity model, we propose that enhanced magma supply at crustal levels at the OSC may provide an effective mechanism for the migration of ridge discontinuities. This ''dynamic magma supply model'' may explain the commonly observed nonsteady migration pattern of ridge discontinuities by attributing this to the temporal fluctuations in melt availability to the overlapping spreading limbs.INDEX TERMS: 0930 Exploration Geophysics: Oceanic structures; 3025 Marine Geology and Geophysics: Marine seismics (0935); 3035 Marine Geology and Geophysics: Midocean ridge processes; 7220 Seismology: Oceanic crust; KEYWORDS: overlapping spreading center, magma supply, ridge segmentation, ridge propagation, crustal evolution, oceanic crust Citation: Tong, C. H., et al., Influence of enhanced melt supply on upper crustal structure at a mid-ocean ridge discontinuity: A threedimensional seismic tomographic study of 9°N East Pacific Rise,

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Three‐dimensional shallow crustal emplacement at the 9°03′N overlapping spreading center on the East Pacific Rise: Correlations between magnetization and tomographic images

Cited by 37 publications

References 79 publications

Volatile abundances and oxygen isotopes in basaltic to dacitic lavas on mid-ocean ridges: The role of assimilation at spreading centers

Volatile abundances and oxygen isotopes in basaltic to dacitic lavas on mid-ocean ridges: The role of assimilation at spreading centers

Lava deposition history in ODP Hole 1256D: Insights from log‐based volcanostratigraphy

Influence of enhanced melt supply on upper crustal structure at a mid‐ocean ridge discontinuity: A three‐dimensional seismic tomographic study of 9°N East Pacific Rise

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