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Master Thesis

Interaction magma-sédiment et impact environnemental d'une intrusion doléritique - Antrim, Irlande du Nord

Abstract : Portrush Sill, Co.Antrim, Northern Ireland, is a dolerite intrusion related to the North-Atlantic Province. It was intruded in Jurassic mudstones about 55 My ago, forming a contact aureole by thermal metamorphism. Describing Portrush Sill and its interaction with sedimentary country rocks is essential to estimate aureole toxic gasses emission and its environmental impact. We adopted a multi-method approach, including petrologic, petrographic and geochemistry analyses. The field study revealed two new magmatic units prior to the main sill: the upper sill, and numerous minor dolerite intrusions. Major and trace analyses show two magma contamination process: a deep crustal assimilation, and a superficial fluid circulation contamination. Data obtained for the contact aureole show isochemical high-T° metamorphism within hornfels (> 660 °C): the CO 2-poor shale facies of the protolite leads to only water liberation, without environmental effect. South-Eastward, the Scawt Hill contact aureole also revealed isochemical metamorphism, but from other origins: the lack of toxic gas releasing is due to the high-T° s tability of carbonates. Those two intrusions show that environmental impact due to degassing process in aureole contact are essentially dependent on the sediment composition and the degree of pick metamorphism.
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Submitted on : Friday, February 5, 2010 - 3:42:36 PM
Last modification on : Tuesday, July 21, 2020 - 5:18:54 AM
Long-term archiving on: : Wednesday, November 30, 2016 - 12:39:39 PM

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  • HAL Id : dumas-00453794, version 1

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Morgane Ledevin. Interaction magma-sédiment et impact environnemental d'une intrusion doléritique - Antrim, Irlande du Nord. Géochimie. 2009. ⟨dumas-00453794⟩

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