Metamorphism and Deformation in Early Proterozoic Basic Dykes Near Scourie, Northwest Scotland (Amphibolite)
type: CreativeWork
description: Early Proterozoic amphibolite dykes of the Scourie Dyke swarm, exposed in the transitional Archean to Proterozoic Lewisian basement near Scourie, Northwest Scotland, exhibit complex morphologies, mineralogies, and microfabrics. Dyke morphology is often highly variable, and was controlled to a large extent by pre-existing structures within the gneissic basement. The mineralogy and microfabric of major dykes record a common sequence of metamorphism and deformation. Localization of deformation and fluid within narrow, generally anastomosing zones was responsible for the contemporaneous development of two distinct dyke fabrics. Complexity and intensity of fabric development does not correlate with complexity of dyke morphology or with structures in the basement rock. The non-schistose dyke rock records a series of processes involving unmixing of the original ferro-magnesian minerals and growth of continuously zoned amphibole rims. Microstructures record contemporaneous ductile deformation, and recovery and recrystallization processes. Schistose rock assemblages are equivalent to the rims and recrystallized grains of the non-schistose rock. These fabrics reflect local differences in amount of deformation, grain growth, recovery, and recrystallization within individual dykes. Amphibolitization was primarily confined within dyke margins. There is no correlation between the dyke characteristics and mineralogical or structural changes within the country rock. The mineralogical and deformational character of the dykes probably formed in association with, or closely following intrusion. The amphibolite facies mineralogy and two distinct dyke fabrics are preserved, with no superposition of later fabrics or metamorphic mineralogy. This observation precludes the occurrence of younger regional metamorphism or deformation in the area traversed by these dykes. The microstructural and mineralogical characteristics of these transition zone dykes are unique in comparison with Scourie D…
abstract: Early Proterozoic amphibolite dykes of the Scourie Dyke swarm, exposed in the transitional Archean to Proterozoic Lewisian basement near Scourie, Northwest Scotland, exhibit complex morphologies, mineralogies, and microfabrics. Dyke morphology is often highly variable, and was controlled to a large extent by pre-existing structures within the gneissic basement. The mineralogy and microfabric of major dykes record a common sequence of metamorphism and deformation. Localization of deformation and fluid within narrow, generally anastomosing zones was responsible for the contemporaneous development of two distinct dyke fabrics. Complexity and intensity of fabric development does not correlate with complexity of dyke morphology or with structures in the basement rock. The non-schistose dyke rock records a series of processes involving unmixing of the original ferro-magnesian minerals and growth of continuously zoned amphibole rims. Microstructures record contemporaneous ductile deformation, and recovery and recrystallization processes. Schistose rock assemblages are equivalent to the rims and recrystallized grains of the non-schistose rock. These fabrics reflect local differences in amount of deformation, grain growth, recovery, and recrystallization within individual dykes. Amphibolitization was primarily confined within dyke margins. There is no correlation between the dyke characteristics and mineralogical or structural changes within the country rock. The mineralogical and deformational character of the dykes probably formed in association with, or closely following intrusion. The amphibolite facies mineralogy and two distinct dyke fabrics are preserved, with no superposition of later fabrics or metamorphic mineralogy. This observation precludes the occurrence of younger regional metamorphism or deformation in the area traversed by these dykes. The microstructural and mineralogical characteristics of these transition zone dykes are unique in comparison with Scourie D…
author: Fryer, Karen Helene
keywords: Geology
date published: 2014-12-16T06:06:46Z
date modified: 2026-07-22T22:26:04Z
provider: University of Illinois - Urbana-Champaign
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Illinois at Urbana-Champaign

PropertyValue
property ID: Handle
value: http://hdl.handle.net/2142/71142