Rift-zone development around a plume-related magma centre on the Isle of Skye (Scotland): a model for stress inversions |
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Authors: | Cécile Doubre & Laurent Geoffroy |
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Institution: | Laboratoire de Géodynamique des Rifts et des Marges Passives, EA 3264, Facultédes Sciences, Universitédu Maine, Av. Olivier Messiaen, 72085 Le Mans Cedex 09, France |
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Abstract: | ABSTRACT Using the example of the Isle of Skye in Scotland, we investigate the influence of pressure variations in upper-crustal magma reservoirs on the development of rift-type normal faulting around central volcanoes. The regional synmagmatic stress regime is of strike-slip type in Scotland during the Lower Tertiary. During a prolonged period of overall high pressure in the Skye magma reservoir (gabbro intrusion stage), crustal extension results from the injection of basaltic dykes parallel to the trend of the far-field maximum stress. During a subsequent period of pressure decrease in the reservoir (granites intrusion stage) normal faults trending parallel to the dykes are initiated. These faults tilt the upper-crustal blocks along with the former dyke swarm and associated lava pile. Finite-element modelling shows that a decrease of magma pressure in a circular cavity may lead, as in Skye, to a change from a regional strike-slip to a local rift-type normal stress regime. |
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