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Second-order segmentation; the relationship between volcanism and tectonism at the MAR, 38N-35 40N

Second-order segmentation; the relationship between volcanism and tectonism at the MAR, 38N-35 40N
Second-order segmentation; the relationship between volcanism and tectonism at the MAR, 38N-35 40N
Deep-tow sidescan sonar data acquired along 240 km of the Mid-Atlantic Ridge (MAR) between 35°40?N and 38°N have been combined with new bathymetric compilations and used to establish the recent tectonic and volcanic history of six second-order segments and their bounding non-transform offsets (NTOs). The segments show a range of volcanic and tectonic types, but in general the northernmost segments (i.e. those with greater influence from the Azorean hotspot) are shallower and more volcanically robust than those to the south, with hydrothermal activity in segment centres (for example, Menez Gwen and Lucky Strike). Nonetheless, this generalisation requires some modification due to temporal variations in the balance between magmatic supply and tectonic dismemberment. The NTOs are broad right-stepping discontinuities, locally up to 25 km wide, and accommodate offsets between 10 and 50 km. The discontinuities are mostly sediment-floored, and link the spreading segment tips with a range of structures. These include locally dense arrays of en echelon extensional normal faults, short lengths of linear strike–slip fault strands occasionally cutting basement blocks apparently stranded within the offsets. Basement blocks within the offsets are cross-cut by complexes of intersecting faults, suggesting that deformation is distributed across the zone. The pervasive faulting taking place at the NTOs favours fluid circulation and associated hydrothermal activity, as at the Rainbow Site at 36°17?N.
MID ATLANTIC RIDGE, VOLCANISM, TECTONICS, FAULTS, TOBI, SIDE SCAN SONAR, AMAR, MENEZ GWEN, LUCKY STRIKE, FAMOUS
0012-821X
231-251
Parson, L.
8985a003-911e-402e-a858-3ecbd09d6771
Gracia, E.
f9e61943-c032-4be7-9c37-c5199fc8950e
Coller, D.
3ad97fdc-df25-4b9c-a272-8cbd8d97116d
German, C.
eef91285-1bfc-41ab-9427-44a7b2874ce2
Needham, D.
e22dceac-6c11-4480-a16d-ec4b51a16f8c
Parson, L.
8985a003-911e-402e-a858-3ecbd09d6771
Gracia, E.
f9e61943-c032-4be7-9c37-c5199fc8950e
Coller, D.
3ad97fdc-df25-4b9c-a272-8cbd8d97116d
German, C.
eef91285-1bfc-41ab-9427-44a7b2874ce2
Needham, D.
e22dceac-6c11-4480-a16d-ec4b51a16f8c

Parson, L., Gracia, E., Coller, D., German, C. and Needham, D. (2000) Second-order segmentation; the relationship between volcanism and tectonism at the MAR, 38N-35 40N. Earth and Planetary Science Letters, 178 (3/4), 231-251. (doi:10.1016/S0012-821X(00)00090-X).

Record type: Article

Abstract

Deep-tow sidescan sonar data acquired along 240 km of the Mid-Atlantic Ridge (MAR) between 35°40?N and 38°N have been combined with new bathymetric compilations and used to establish the recent tectonic and volcanic history of six second-order segments and their bounding non-transform offsets (NTOs). The segments show a range of volcanic and tectonic types, but in general the northernmost segments (i.e. those with greater influence from the Azorean hotspot) are shallower and more volcanically robust than those to the south, with hydrothermal activity in segment centres (for example, Menez Gwen and Lucky Strike). Nonetheless, this generalisation requires some modification due to temporal variations in the balance between magmatic supply and tectonic dismemberment. The NTOs are broad right-stepping discontinuities, locally up to 25 km wide, and accommodate offsets between 10 and 50 km. The discontinuities are mostly sediment-floored, and link the spreading segment tips with a range of structures. These include locally dense arrays of en echelon extensional normal faults, short lengths of linear strike–slip fault strands occasionally cutting basement blocks apparently stranded within the offsets. Basement blocks within the offsets are cross-cut by complexes of intersecting faults, suggesting that deformation is distributed across the zone. The pervasive faulting taking place at the NTOs favours fluid circulation and associated hydrothermal activity, as at the Rainbow Site at 36°17?N.

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More information

Published date: 2000
Keywords: MID ATLANTIC RIDGE, VOLCANISM, TECTONICS, FAULTS, TOBI, SIDE SCAN SONAR, AMAR, MENEZ GWEN, LUCKY STRIKE, FAMOUS

Identifiers

Local EPrints ID: 8887
URI: http://eprints.soton.ac.uk/id/eprint/8887
ISSN: 0012-821X
PURE UUID: 2b2637ec-daf3-4db6-90fb-a0b89289b0ee

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Date deposited: 13 Sep 2004
Last modified: 15 Mar 2024 04:53

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Contributors

Author: L. Parson
Author: E. Gracia
Author: D. Coller
Author: C. German
Author: D. Needham

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