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Title: Rifted margin formation in the northwest Indian Ocean : the extensional and magmatic history of the Laxmi Ridge continental margin
Author: Lane, Christine Irene
ISNI:       0000 0004 2675 103X
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2006
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This thesis focuses on geophysical data collected over the Laxmi Ridge margin. A 480 km wide-angle velocity model is presented, along with coincident normal-incidence reflection data, gravity and magnetic modelling. The wide-angle model is broadly divided into four areas of crustal provenance: the southern-most crust is Chron 27 oceanic crust, which is around 5 km thick and reaches velocities of 7.4 km s⁻¹ at its base. Laxmi Ridge is adjacent to this crust, and is a 130 km wide, 9 km thick section of thinned continental crust. It is underlain by 11 km of high velocity arterial, whose P-wave velocities reach 7.70 km s⁻¹ at the base. Laxmi Ridge abuts against Gop Rift, which is a 55 km wide basin with crust up to 13 km thick. North of Gop Rift is the continental rise of India, which is interpreted as stretched continental crust. The Laxmi Ridge margin has features usually diagnostic of amagmatic rifted margins, including thin (5 km) first-formed oceanic crust south of Laxmi Ridge and weak seaward-dipping reflectors at the ocean-continent boundary. However, thick oceanic crust is observed in Gap Rift, an isolated asymmetric basin landward of Laxmi Ridge. Gop Rift is flanked by two ~ 100 km wide, almost 13 km thick bodies in the deep crust, whose P-wave velocities reach 7.70 km s⁻¹. These bodies are interpreted to be magmatic underplate associated with rifting over a thermal anomaly. This apparent disparity between magmatic and amagmatic features on the same margin is solved if the magmatic features are attributed to a prior phase of spreading in Gap Rift, most likely Chron 29 in age, with the magmatic material supplied by enhanced melting over the Deccan plume. This spreading ceased once the thermal anomaly cooled. The final breakup of India and the Seychelles then occurred within the weakened underplated lithosphere, and was relatively amagmatic despite the rapid extension.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available