Evolution of nonvolcanic rifted margins: New results from the conjugate margins of the Labrador Sea

Chian, D.; Keen, C. E.; Reid, I.; Louden, K. E.

doi:10.1130/0091-7613(1995)023<0589:eonrmn>2.3.co;2

Cited by 103 publications

(99 citation statements)

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“…Gravity modeling has been a common exercise in studies of deep-crustal structure [e.g., Holbrook et al, 1994b;Horsefield et al, 1994;Chian et al, 1995;Barton and White, 1997a;Lizarralde and Holbrook, 1997;Reid and Jackson, 1997;Mjelde et al, 1998];…”

Section: Discussionmentioning

confidence: 99%

Magmatism and dynamics of continental breakup in the presence of a mantle plume

Korenaga¹

2000

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This thesis studies the dynamics of mantle melting during continental breakups by geophysical, geochemical, and numerical analyses. The first part focuses on the mantle melting and crustal accretion processes during the formation of the Southeast Greenland margin, on the basis of deep-crustal seismic data. A new seismic tomographic method is developed to jointly invert refraction and reflection travel times for a compressional velocity structure, and a long-wavelength structure with strong lateral heterogeneity is successfully recovered, including 30-to 15-km-thick igneous crust within a 150-km-wide continent-ocean transition zone. A nonlinear Monte Carlo analysis is also conducted to establish the absolute uncertainty of model parameters. The derived crustal structure is first used to resolve the origin of a margin gravity high, with new inversion schemes using both seismic and gravity constraints. Density anomalies producing the gravity high seem to be confined within the upper crust, not in the lower crust as suggested for other volcanic margins. A new robust framework is then developed for the petrological interpretation of the velocity structure of igneous crust, and the thick igneous crust formed at the continentocean transition zone is suggested to have resulted from vigorous active upwelling of mantle with only somewhat elevated potential temperature. In the second part, the nature of mantle melting during the formation of the North Atlantic igneous province is studied on the basis of the major element chemistry of erupted lavas. A new fractionation correction scheme based on the Ni concentrations of mantle olivine is used to estimate primary melt compositions, which suggest that this province is characterized by a large degree of major element source heterogeneity. In the third part, the nature of preexisting sublithospheric convection is investigated by a series of finite element analyses, because the strength of such convection is important to define the "normal" state of mantle, the understanding of which is essential to identify any anomalous behavior of mantle such as a mantle plume. The results suggest that small-scale convection is likely in normal asthenosphere, and that the upwelling velocity in such convection is on the order of 1-10 cm/yr. 271 Introductory NotesThis thesis is composed of three parts, all of which are related to the dynamics of mantle melting during continental breakups. In the first part, rifting magmatism associated with the opening of the North Atlantic (at -60 Ma) is investigated on the basis of deep-crustal seismic data collected across the Southeast Greenland continental margin. A new seismic tomographic method is developed to jointly invert refraction and reflection travel times for a two-dimensional velocity structure (Chapter 1). Several key issues in travel time tomography such as velocity-depth ambiguity and absolute parameter uncertainty are identified, and a practical strategy is presented to resolve them. The derived crustal velocity structure is the...

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Section: Discussionmentioning

confidence: 99%

Magmatism and dynamics of continental breakup in the presence of a mantle plume

Korenaga¹

2000

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“…We both compare with published surface magnetic data [e.g., Srivastava and Roest, 1999] and crustal seismic profiles [Chian and Louden, 1994; Chian et al, 1995] in order to investigate the limit between unextended buoyant continental crust and very thin (6 km) continental crust [Chalmers and Laursen, 1995], Cretaceous oceanic crust [e.g., Srivastava and Roest, 1999], or else extremely thin (< 2 km) transition crust [Chian et al, 1995].…”

Section: Labrador Seamentioning

confidence: 99%

Southeast Baffin volcanic margin and the North American‐Greenland plate separation

Geoffroy¹,

Callot²,

Scaillet³

et al. 2001

Tectonics

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“…For these reasons, we suggest that this margin may be amagmatic, analogous to those of the Labrador Sea [Chian et al, 1995] and the Grand Banks [Reid, 1994], and that the 6.8-km/s layer may in fact be serpentinized mantle. If this interpretation is correct, it implies that the rifting in northern Baffin Bay took place, at least initially, with little or no melt production, and that the thick sedimentary sequences south of the paleoshelf edge in fact directly overlies tectonically exposed mantle.…”

Section: Regional Free Air Gravitymentioning

confidence: 99%

Crustal structure of northern Baffin Bay: Seismic refraction results and tectonic implications

Reid¹,

Jackson²

1997

J. Geophys. Res.

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Abstract. Two detailed seismic refraction lines were shot in northern Baffin Bay in order to determine the crustal structure and so provide constraints on the complex geological and tectonic history of the area. An array of air guns provided the seismic source, with a total of 16 ocean bottom seismometers as receivers. The data were analyzed by iterative forward modeling of travel times and arrival amplitudes, and the crustal velocity structure obtained was interpreted in the light of previous seismic reflection and refraction results from this area, together with other available geological and geophysical information. Plate reconstructions suggest that the region was a single entity from the Archean until the late Mesozoic, when it underwent successive stages of extension, translation, and compression. On line 2, at 76 ø N, the continental crust thins between Greenland and Ellesmere Island, reaching to a minimum of about 10 km beneath a narrow, linear basin, which may delineate a former transform plate boundary. On line 4, on the northern margin of Baffin Bay, there is a marked change in velocity structure across the apparent continent-ocean boundary, with continental crust being replaced by a layer of intermediate seismic velocity that is believed to be serpentinized mantle, indicating that northern Baffin Bay was formed by amagmatic continental rifting and separation. A thick sedimentary sequence is the result of erosion of the Eurekan Orogen to the north, which was formed during the final, compressional tectonic motion.The seismic refraction results are consistent with the tectonic history inferred from plate kinematics.

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Evolution of nonvolcanic rifted margins: New results from the conjugate margins of the Labrador Sea

Cited by 103 publications

References 0 publications

Magmatism and dynamics of continental breakup in the presence of a mantle plume

Magmatism and dynamics of continental breakup in the presence of a mantle plume

Southeast Baffin volcanic margin and the North American‐Greenland plate separation

Crustal structure of northern Baffin Bay: Seismic refraction results and tectonic implications

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