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Along-axis variation in crustal thickness at the ultraslow spreading Southwest Indian Ridge (50°E) from a wide-angle seismic experiment

Along-axis variation in crustal thickness at the ultraslow spreading Southwest Indian Ridge (50°E) from a wide-angle seismic experiment
Along-axis variation in crustal thickness at the ultraslow spreading Southwest Indian Ridge (50°E) from a wide-angle seismic experiment
The Southwest Indian Ridge (SWIR) is characterized by an ultraslow spreading rate, thin crust, and extensive outcrops of serpentinized peridotite. Previous studies have used geochemical and geophysical data to suggest the presence of a thicker crust at the central and shallowest portions of the SWIR, from the Prince Edward (35°30?E) to the Gallieni (52°20?E) fracture zones. Here we present a new analysis of wide-angle seismic data along the ridge 49°17?E–50°49?E. Our main conclusions are as follows: (1) we find an oceanic layer 2 of roughly constant thickness and steep velocity gradient, underlain by a layer 3 with variable thickness and low velocity gradient; (2) the crustal thickness varies from ?5 km beneath nontransform discontinuities (NTDs) up to ?10 km beneath a segment center; (3) the melt supply is focused in segment centers despite a small NTD between adjacent segments; (4) the presence of a normal upper mantle velocity indicates that no serpentinization occurs beneath this thick crust. Our observation of thick crust at an ultraslow spreading ridge adds further complexity to relationships between crustal thickness and spreading rate, and supports previous suggestions that the extent of mantle melting is not a simple function of spreading rate, and that mantle temperature or chemistry (or both) must vary significantly along axis.
Southwest Indian Ridge, oceanic crust, thick crust, wide-angle seismic experiment, mantle
1525-2027
468-485
Niu, Xiongwei
1f806e9f-eff5-4354-9478-fbfb1056aa3c
Ruan, Aiguo
b70c0f3e-2790-4242-a216-1bf2ef8dd574
Li, Jiabiao
ffacfd36-3b8b-41ed-b7ac-ee037985ac7c
Minshull, T.A.
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Sauter, Daniel
67c1f131-d5f6-4bd4-8cd6-06f8dca35c41
Wu, Zhenli
505114c3-bd7b-4346-b2a7-6c6c31e9479d
Qiu, Xuelin
d2d7d18b-1023-4fa5-bf88-3917e2cf3513
Zhao, Minghui
84a6c41f-1ec1-4dee-9edf-89d184aa606c
Chen, Y. John
4dfdc953-9cf8-4523-96db-4e217a9c0550
Singh, Satish
07f0d07e-4c74-481d-afdb-3962b52e6d86
Niu, Xiongwei
1f806e9f-eff5-4354-9478-fbfb1056aa3c
Ruan, Aiguo
b70c0f3e-2790-4242-a216-1bf2ef8dd574
Li, Jiabiao
ffacfd36-3b8b-41ed-b7ac-ee037985ac7c
Minshull, T.A.
bf413fb5-849e-4389-acd7-0cb0d644e6b8
Sauter, Daniel
67c1f131-d5f6-4bd4-8cd6-06f8dca35c41
Wu, Zhenli
505114c3-bd7b-4346-b2a7-6c6c31e9479d
Qiu, Xuelin
d2d7d18b-1023-4fa5-bf88-3917e2cf3513
Zhao, Minghui
84a6c41f-1ec1-4dee-9edf-89d184aa606c
Chen, Y. John
4dfdc953-9cf8-4523-96db-4e217a9c0550
Singh, Satish
07f0d07e-4c74-481d-afdb-3962b52e6d86

Niu, Xiongwei, Ruan, Aiguo, Li, Jiabiao, Minshull, T.A., Sauter, Daniel, Wu, Zhenli, Qiu, Xuelin, Zhao, Minghui, Chen, Y. John and Singh, Satish (2015) Along-axis variation in crustal thickness at the ultraslow spreading Southwest Indian Ridge (50°E) from a wide-angle seismic experiment. Geochemistry, Geophysics, Geosystems, 16 (2), 468-485. (doi:10.1002/2014GC005645).

Record type: Article

Abstract

The Southwest Indian Ridge (SWIR) is characterized by an ultraslow spreading rate, thin crust, and extensive outcrops of serpentinized peridotite. Previous studies have used geochemical and geophysical data to suggest the presence of a thicker crust at the central and shallowest portions of the SWIR, from the Prince Edward (35°30?E) to the Gallieni (52°20?E) fracture zones. Here we present a new analysis of wide-angle seismic data along the ridge 49°17?E–50°49?E. Our main conclusions are as follows: (1) we find an oceanic layer 2 of roughly constant thickness and steep velocity gradient, underlain by a layer 3 with variable thickness and low velocity gradient; (2) the crustal thickness varies from ?5 km beneath nontransform discontinuities (NTDs) up to ?10 km beneath a segment center; (3) the melt supply is focused in segment centers despite a small NTD between adjacent segments; (4) the presence of a normal upper mantle velocity indicates that no serpentinization occurs beneath this thick crust. Our observation of thick crust at an ultraslow spreading ridge adds further complexity to relationships between crustal thickness and spreading rate, and supports previous suggestions that the extent of mantle melting is not a simple function of spreading rate, and that mantle temperature or chemistry (or both) must vary significantly along axis.

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e-pub ahead of print date: 19 February 2015
Published date: February 2015
Keywords: Southwest Indian Ridge, oceanic crust, thick crust, wide-angle seismic experiment, mantle
Organisations: Geology & Geophysics

Identifiers

Local EPrints ID: 374553
URI: http://eprints.soton.ac.uk/id/eprint/374553
ISSN: 1525-2027
PURE UUID: fa26dd8c-5263-4625-8641-2527052be4bb
ORCID for T.A. Minshull: ORCID iD orcid.org/0000-0002-8202-1379

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Date deposited: 20 Feb 2015 10:45
Last modified: 15 Mar 2024 03:04

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Contributors

Author: Xiongwei Niu
Author: Aiguo Ruan
Author: Jiabiao Li
Author: T.A. Minshull ORCID iD
Author: Daniel Sauter
Author: Zhenli Wu
Author: Xuelin Qiu
Author: Minghui Zhao
Author: Y. John Chen
Author: Satish Singh

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