Novel Insights into the Palaeomagnetism of Serpentinized Peridotites from the Troodos and Oman Ophiolites
type: CreativeWork
description: Large volumes of mantle peridotite are exposed at the Earth’s surface in ophiolites, becoming vulnerable to the concurrent chemical alteration processes of serpentinization and carbonation. Serpentinization frequently results in the production of secondary magnetite that can record the direction of the Earth’s magnetic field at the time of its formation, allowing palaeomagnetism to be used as a tool to investigate this process. Many ophiolites also experienced large-scale tectonic rotations during their evolution. In some cases, the timing of these rotations is well-documented palaeomagnetically, potentially allowing the timing of different phases of serpentinization to be constrained if the magnetization directions of secondary magnetite assemblages can be determined and compared to known rotation histories. This research represents the first attempt to combine paleomagnetic and rock magnetic analyses of serpentinized mantle peridotites with state-of-the-art Quantum Diamond Microscopy (QDM), a recently developed analytical tool that allows two-dimensional images of the magnetic fields in a sample arising from distributions of magnetic sources. Two ophiolites are the focus of this thesis. The Late Cretaceous Troodos ophiolite of Cyprus that underwent a ~90° anticlockwise tectonic rotation that began shortly after it formed by seafloor spreading. The timing of this rotation is well-constrained by palaeomagnetic analysis of the sedimentary rocks that were deposited continuously while the underlying oceanic crust rotated. In this context, different magnetization directions would be expected to be carried by magnetite assemblages produced by serpentinization during: (i) early exposure on the seafloor or deep fluid circulation during Late Cretaceous seafloor spreading; (ii) subsequent progressive tectonic rotation; and (iii) Plio-Quaternary to Recent tectonic uplift and/or reaction with modern meteoric water. The Late Cretaceous Samail/Semail ophiolite in Oman and the UA…
abstract: Large volumes of mantle peridotite are exposed at the Earth’s surface in ophiolites, becoming vulnerable to the concurrent chemical alteration processes of serpentinization and carbonation. Serpentinization frequently results in the production of secondary magnetite that can record the direction of the Earth’s magnetic field at the time of its formation, allowing palaeomagnetism to be used as a tool to investigate this process. Many ophiolites also experienced large-scale tectonic rotations during their evolution. In some cases, the timing of these rotations is well-documented palaeomagnetically, potentially allowing the timing of different phases of serpentinization to be constrained if the magnetization directions of secondary magnetite assemblages can be determined and compared to known rotation histories. This research represents the first attempt to combine paleomagnetic and rock magnetic analyses of serpentinized mantle peridotites with state-of-the-art Quantum Diamond Microscopy (QDM), a recently developed analytical tool that allows two-dimensional images of the magnetic fields in a sample arising from distributions of magnetic sources. Two ophiolites are the focus of this thesis. The Late Cretaceous Troodos ophiolite of Cyprus that underwent a ~90° anticlockwise tectonic rotation that began shortly after it formed by seafloor spreading. The timing of this rotation is well-constrained by palaeomagnetic analysis of the sedimentary rocks that were deposited continuously while the underlying oceanic crust rotated. In this context, different magnetization directions would be expected to be carried by magnetite assemblages produced by serpentinization during: (i) early exposure on the seafloor or deep fluid circulation during Late Cretaceous seafloor spreading; (ii) subsequent progressive tectonic rotation; and (iii) Plio-Quaternary to Recent tectonic uplift and/or reaction with modern meteoric water. The Late Cretaceous Samail/Semail ophiolite in Oman and the UA…
author: Hepworth, James
language: eng
date published: 2025-01-01T08:00:00Z
date modified: 2026-07-24T03:49:35Z
provider: University of Plymouth
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Plymouth