Research

The McMaster Structural Geology and Tectonics Research Group has a very wide range of interests but primarily focuses on rift system, continental breakup and the evolution of continental passive margins, including the processes that led to breakup and subsequent passive margin formation. Particular areas of interest include: rift-related magmatism, structural inheritance and mantle dynamics. Geographically, the work to date has principally focused on the continental margins of the North Atlantic and surrounding regions including; Newfoundland, West Greenland, Jan Mayen, Labrador and the UK/Irish margin.

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Looking northeast onto the faulted top pre-rift/basement horizon in the Davis Strait, offshore West Greenland.

Methodologies

The nature of the work undertaken in this group requires a multifaceted approach incorporating a wide variety of approaches and methodologies such as: seismic interpretation, field-based studies, numerical modelling, petrology, structural modelling and geochemistry.

Current Research Projects

1. Causes of active seismicity in Eastern Canada

The St. Lawrence region in Eastern Canada is an area of significant active seismicity. This seismicity has been suggested to be highly controlled by pre-existing structures. However, the exact role of structural inheritance remains unknown. In addition, it is currently unclear how much of the seismicity is controlled by glacial isostatic rebound and how much is from tectonic processes. This work seeks to answer these questions through new field-based studies.

2. Style, controls, and distribution of salt and faulting in the North Sea

This research area is primarily the work of BSc thesis students Evangeline Ng and Emma Keefe. The aim is to provide new understanding of rift development in the North Sea, and particular, the  evolution of rift-related faulting and the relationship to salt tectonics. This is being achieved through interpretation of subsurface seismic data provided by the Oil and Gas Authority in the UK.

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Examples of Salt shown on seismic reflection data from the Mid-North Sea High.
Project collaborators: Evangeline NG & Emma Keefe

3. Deformable plate tectonic models for the southern North Atlantic

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Crustal thickness of the continental margins of the southern North Atlantic from deformable plate tectonic models (GPlates). (Peace et al., 2019)

One of the most fundamental problems with the many plate tectonic models is the assumption of rigid plates, despite the fact that a large amount of deformation is known to occur in the continental domain. In addition, the role of micro continental fragments (e.g. mircoplates, continental ribbons etc.) is currently under appreciated. For these reasons we are currently using the latest version of GPlates to construct deformable plate models of the southern North Atlantic, that include microcontinental fragments. This work is currently in review with Journal of Geodynamics.

Project collaborators: J. Kim Welford, Phillip Ball and Michael Nirrengarten.

4. Petrology, geochemistry and geochronology of Mesozoic intrusions onshore Newfoundland

The role of magmatism during rifting and continental breakup is a highly contentious topic. I recently conducted research on the structure of onshore Mesozoic rift-related igneous rocks in Newfoundland and published the results in Tectonophysics and Geophysics. This work highlighted the need for a modern geochronological analysis, in addition to further work on the petrology to fully comprehend the role of these rocks during the separation of Newfoundland from Europe. As such, we are currently investigating these aspects of the intrusions.

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Mineral Liberation Analysis (MLA) map (false colour) of lamprophyre dyke sample from Notre Dame Bay.
Project collaborators: J. Kim Welford, Hamish Sandeman and Gregory Dunning

5. Asymmetric rifting, breakup and magmatism across conjugate margin pairs: insights from Newfoundland to Ireland

Group P.I Dr. Alexander Peace is currently conducting a comparison of rift and breakup related magmatic events through the rift cycle on the approximately conjugate Northern Newfoundland and UK/Irish margin. The main aim of this project is to reevaluate rift-related magmatism in order to provide thermal and structural constraints on the development of the offshore Orphan Basin and the conjugate Irish margin.

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Mesozoic Lamprophyre dyke displaying minor bridge structure coincident with the axis of a minor fold near Leading Tickles, Newfoundland, Canada

On the northern Newfoundland margin a small volcanic province has been interpreted near the termination of the Charlie Gibbs Fracture Zone and onshore adjacent to the Newfoundland margin localized Jurassic-Cretaceous igneous rocks intruded during the earliest stages of breakup have been described. By contrast magamatism on the conjugate Irish margin appears to be significantly more widespread particularly within the Rockall Basin but also within the Porcupine basin to the south. However, the voluminous magmatism documented on the Irish margin occurs during the post-rift stage, whilst syn-rift occurrences on this margin from both the offshore and adjacent onshore are surprisingly rare. Again, this differs from the conjugate northern Newfoundland margin where widespread post-rift magmatism is, if present, minimal.

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Mesozoic Lamprophyre dyke near Cottrell’s Cove, Newfoundland, Canada

The variable distribution of magmatism between the conjugate margins throughout the rift cycle, an in particular the broader region over which late-stage magmatism has been identified on the Irish margin is suggestive of magmatic asymmetry across this conjugate margin pair. This feature is likely to have direct implications for the mechanisms governing rifting and breakup.

Project collaborators: J. Kim Welford, Larry Sandoval, Heide Macmahon, Michael Nirrengarten et al.

6. A review of Pangaea dispersal and Large Igneous Provinces – In search of causative mechanisms

The breakup of Pangea was accompanied by extensive, episodic, magmatic activity. Several Large Igneous Provinces (LIPs) formed, such as the Central Atlantic Magmatic Province (CAMP) and the North Atlantic Igneous Province (NAIP). Despite the prevalent idea that some continental rifts are triggered by thermal anomalies, rising from the deep mantle, these locations often coincide with aborted rift basins, major, rift-orthogonal shear zones, or triple junctions.

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Breakup related magmatism in East Gondwana from Peace et al. (2019)

In this project, we consider the chronological order of the breakup of Pangea and the relationship between large-scale magmatism and the Triassic formation of the Central Atlantic Ocean, the breakup between East and West Gondwana in Middle Jurassic times, the Early Cretaceous opening of the South Atlantic, the Late Cretaceous separation of India from Antarctica, and finally the formation of the North Atlantic in the early Cenozoic.

This work is part of a series of invited Earth-Science Reviews papers that were conceived following a series of workshops held at Durham University, UK between 2016 and 2018 focusing on the geodynamics of the North Atlantic region.

Project collaborators: Jordan Phethean, Dieter Franke, Tony Doré, Gillian, Foulger, Gregory McHone, Sergio Rocchi, Christian Schiffer, Michael Schnabel, and Kim Welford

7. Segmentation of rifts through structural inheritance: Creation of the Davis Strait

Mesozoic-Cenozoic rifting between Greenland and North America created the Labrador Sea and Baffin Bay, while leaving preserved continental lithosphere in the Davis Strait which lies between them. Inherited crustal structures from a Palaeoproterozoic collision have been hypothesized to account for the tectonic features of this rift system. However, the role of mantle lithosphere heterogeneities in continental suturing has not been fully explored.

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Numerical modelling results showing the role of a mantle scar in the evolution of the Davis Strait from Heron et al. (2019).

Our study uses 3-D numerical models to analyze the role of crustal and sub-crustal heterogeneities in controlling deformation. We implement continental extension in the presence of mantle lithosphere suture zones and deformed crustal structures and present a suite of models analyzing the role of local inheritance related to the region. In particular, we investigate the respective roles of crust and mantle lithospheric scarring during an evolving stress regime in keeping with plate tectonic reconstructions of the Davis Strait. Numerical simulations, for the first time, can reproduce first order features that resemble the Labrador Sea, Davis Strait, Baffin Bay continental margins and ocean basins.

The positioning of a mantle lithosphere suture, hypothesized to exist from ancient orogenic activity, produces a more appropriate tectonic evolution of the region than the previously proposed crustal inheritance. Indeed, the obliquity of the continental mantle suture with respect to extension direction is shown here to be important in the preservation of the Davis Strait. Mantle lithosphere heterogeneities are often overlooked as a control of crustal-scale deformation. Here, we highlight the sub-crust as an avenue of exploration in the understanding of rift system evolution.

Project collaborators: Philip Heron, Kim Welford, Ken McCaffrey, Russell Pysklywec & Woody Wilson

Links to collaborators websites

Gillian Foulger

Phil Heron

Kim Welford

Christian Schiffer

Eddie Dempsey