AbstractContinental rifting is achieved through a combination of magmatic and amagmatic processes. However, these processes can be influenced by heterogeneities at a range of scales, which act as regions of relative strength and weakness in the crust. The subaerial East African Rift, the longest continental rift on Earth, demonstrates the transition between incipient amagmatic and mature magmatic rifting. The rift interacts with geology that spans 3.8 Ga, and thus represents the ideal place to investigate crustal heterogeneities and rifting.
Interferometric Synthetic Aperture Radar (InSAR) has been used to observe the surface deformation caused by transient events associated with rifting throughout the East African Rift System. In this thesis, I explore how heterogeneities influence strain partitioning, magma transportation, and hydrothermal fluid migration, through the combination of InSAR, and other geophysical and geological datasets.
In the southern East African incipient rift environments of Mozambique and Botswana, I provide evidence to indicate pre-rift along rift faults are reactivated in the present-day stress field to influence where and how rifting occurs. By contrast, in the more mature, magmatic, Main Ethiopian Rift, I show pre-rift cross rift faults can influence magma and fluid migration over multiple temporal scales.
Magma plays an important role in accommodating extension in mature rift settings, primarily through dyking. However, the presence of large axial caldera systems suggest that the localisation of magma in reservoirs is also important. Observations of sustained uplift at the Corbetti caldera, in the Main Ethiopian Rift, indicates upper-crustal silicic magma reservoirs at continental rift calderas grow incrementally, through pulses of above-average magma flux.
|Date of Award||25 Sep 2018|
|Supervisor||Juliet J Biggs (Supervisor) & Geoff Wadge (Supervisor)|