Crustal structure across the Grand Banks-Newfoundland Basin Continental Margin - I. Results from a seismic refraction profile

Lau, K. W. Helen; Louden, K. E.; Funck, Thomas; Tucholke, Brian E.; Holbrook, W. S.; Hopper, John R.; Larsen, Hans Christian

doi:10.1111/j.1365-246x.2006.02988.x

Cited by 99 publications

(166 citation statements)

References 50 publications

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“…There are substantial variations in the P-wave velocity characteristics of the OCT. The OCT reaches a width of > 100 km on the IAM9 and SCREECH3 profiles [8,24], while on the ISE1 profile offshore Galicia Bank [25], the OCT is likely only ~20 km wide, though oceanic crust cannot be identified clearly on this profile.…”

Section: P-wave Velocity Structurementioning

confidence: 97%

Geophysical characterisation of the ocean–continent transition at magma-poor rifted margins

Minshull

2008

Comptes Rendus. Géoscience

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Geophysical characterisation of the ocean-continent transition (OCT) at magma-poor rifted margins has focused primarily on the determination of P wave velocities using wide-angle seismic techniques. Such experiments have shown that the OCT is heterogeneous, but that typically velocities increase gradually with depth from ~5.0 km/s at top basement to ~8.0 km/s at ~5 km deeper, without a large and abrupt Moho transition. The velocity variation with depth is similar to that of old fracture zone crust, and appears to differ from that of oceanic crust formed at ultra-slow spreading rates, though sampling of the latter is limited.Typically, the OCT is characterised by weakly lineated, low amplitude magnetic anomalies; the interpretation of these anomalies remains controversial. The oceanward limit of the OCT remains poorly defined on many margins.

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Section: P-wave Velocity Structurementioning

confidence: 97%

Geophysical characterisation of the ocean–continent transition at magma-poor rifted margins

Minshull

2008

Comptes Rendus. Géoscience

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“…Laboratory experiments suggest that serpentinization of such large volumes lasted at least a few million years (20). The conjugate Newfoundland Margin likely exposed similar volumes of mantle peridotite to seawater (21), as did other magma-poor passive margins, such as the South Australian Margin and the West Greenland−Labrador conjugate margins (22).…”

Section: Significancementioning

confidence: 99%

Fluid mixing and the deep biosphere of a fossil Lost City-type hydrothermal system at the Iberia Margin

Klein

Humphris

Guo

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Subseafloor mixing of reduced hydrothermal fluids with seawater is believed to provide the energy and substrates needed to support deep chemolithoautotrophic life in the hydrated oceanic mantle (i.e., serpentinite). However, geosphere-biosphere interactions in serpentinite-hosted subseafloor mixing zones remain poorly constrained. Here we examine fossil microbial communities and fluid mixing processes in the subseafloor of a Cretaceous Lost City-type hydrothermal system at the magma-poor passive Iberia Margin (Ocean Drilling Program Leg 149, Hole 897D). Brucite−calcite mineral assemblages precipitated from mixed fluids ca. 65 m below the Cretaceous paleo-seafloor at temperatures of 31.7 ± 4.3°C within steep chemical gradients between weathered, carbonate-rich serpentinite breccia and serpentinite. Mixing of oxidized seawater and strongly reducing hydrothermal fluid at moderate temperatures created conditions capable of supporting microbial activity. Dense microbial colonies are fossilized in brucite−calcite veins that are strongly enriched in organic carbon (up to 0.5 wt.% of the total carbon) but depleted in 13 C (δ 13 C TOC = −19.4‰). We detected a combination of bacterial diether lipid biomarkers, archaeol, and archaeal tetraethers analogous to those found in carbonate chimneys at the active Lost City hydrothermal field. The exposure of mantle rocks to seawater during the breakup of Pangaea fueled chemolithoautotrophic microbial communities at the Iberia Margin, possibly before the onset of seafloor spreading. Lost City-type serpentinization systems have been discovered at midocean ridges, in forearc settings of subduction zones, and at continental margins. It appears that, wherever they occur, they can support microbial life, even in deep subseafloor environments.serpentinization | microfossils | lipid biomarkers | brucite−calcite | passive margin

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“…Whitmarsh et al (2001) introduced the term "zone of exhumed continental mantle" to describe the most likely nature of the deep Iberia ocean-continent transition. However, for the conjugate Newfoundland margin the composition of the basement in transition zone is still debated (see Hopper et al 2003;Shillington et al 2006 ;Lau et al 2006).…”

Section: Tectonic Settingmentioning

confidence: 99%

Compressional structures on the West Iberia rifted margin: controls on their distribution

Péron‐Pinvidic¹,

Manatschal²,

Dean³

et al. 2008

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The West Iberia margin is a magma-poor rifted margin that resulted from Jurassic to Cretaceous polyphase rifting leading to the opening of the North Atlantic Ocean. The Mesozoic rift structures were overprinted by two compressive tectonic events during Eocene and Miocene times resulting from collision between Iberia, Europe and Africa. The effects of these compressive tectonic events are expressed by faults and folds within the post-rift sedimentary sequence. We mapped and studied these Cenozoic deformation structures throughout the Southern Iberia Abyssal Plain (40°–41°N, 11°–13°W) on the basis of an extensive dataset of time migrated seismic profiles acquired by various academic institutions. Acoustic basement has also been analysed on the basis of its seismic aspect, in order to test potential relationships with the distribution of the post-rift sedimentary deformation.Our observations lead to three major conclusions concerning the deformation affecting the post-rift sediments in the Southern Iberia Abyssal Plain: (1) the deformation occurs within the zone of exhumed continental mantle and not at its transition to continental or oceanic crust; (2) it is localized within a zone overlying basement with well-defined seismic characteristics; and (3) it is closely related to the major topographic features observed in the ocean–continent transition. The localization of the deformation within the zone of exhumed continental mantle and not at its boundaries to the adjacent oceanic and continental crust suggests that the limits between the different types of crust are transitional rather than sharp. Our results show that the zone of exhumed continental mantle represents the weakest zone within the margin that is preferentially deformed during initial convergence. At higher convergence rates, this zone may coincide with the location of a future subduction.

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Crustal structure across the Grand Banks-Newfoundland Basin Continental Margin - I. Results from a seismic refraction profile

Cited by 99 publications

References 50 publications

Geophysical characterisation of the ocean–continent transition at magma-poor rifted margins

Geophysical characterisation of the ocean–continent transition at magma-poor rifted margins

Fluid mixing and the deep biosphere of a fossil Lost City-type hydrothermal system at the Iberia Margin

Compressional structures on the West Iberia rifted margin: controls on their distribution

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