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Palaeomagnetic evidence for the age of the Cumbrian and Manx hematite ore deposits; implications for the origin of hematite mineralization at the margins of the East Irish Sea Basin, UK

Stephen F. Crowley, John D. A. Piper, Turki Bamarouf and Andrew P. Roberts
Palaeomagnetic evidence for the age of the Cumbrian and Manx hematite ore deposits; implications for the origin of hematite mineralization at the margins of the East Irish Sea Basin, UK
Journal of the Geological Society of London (October 2013) 171 (1): 49-64

Abstract

Examples of epigenetic hematite mineralization located at the margins of the East Irish Sea Basin have been sampled for palaeomagnetic investigation to establish the timing of ore formation. Samples collected from 10 sites in Cumbria are dominated by hematite of near-pure composition and characterized by dual polarity and, in part, dual component magnetizations that yield palaeopoles (nine sites) between 50 degrees N, 130 degrees E and 50 degrees N, 150 degrees E. In contrast, samples recovered from seven sites on the Isle of Man have more varied mineralogical compositions that include ferromagnets with lower unblocking temperatures. Manx hematite mineralization also exhibits dual polarity, but magnetizations yield steeper inclinations with palaeopoles lying between 55 degrees N, 130 degrees E and 70 degrees N, 150 degrees E. Steeper directions probably reflect minor tilting of the Manx block following hematite emplacement. Correlation of poles with the European apparent polar wander path indicates that these ore deposits formed during the Middle Triassic. Results show that hematite mineralization sited at the margins of the East Irish Sea Basin is essentially contemporaneous and establishes, for the first time, an underlying temporal relationship between these geographically dispersed ore bodies. Dating places the mineralization within a broader extensional geotectonic regime associated with the early rifting of Pangaea in the North Atlantic. The context implies a causal link between crustal extension, development of ore-forming fluids within the evolving East Irish Sea Basin, and subsequent migration of fluids to basin margins where iron was precipitated as hematite.


ISSN: 0016-7649
EISSN: 2041-479X
Coden: JGSLAS
Serial Title: Journal of the Geological Society of London
Serial Volume: 171
Serial Issue: 1
Title: Palaeomagnetic evidence for the age of the Cumbrian and Manx hematite ore deposits; implications for the origin of hematite mineralization at the margins of the East Irish Sea Basin, UK
Affiliation: University of Liverpool, Department of Earth and Ocean Sciences, Liverpool, United Kingdom
Pages: 49-64
Published: 20131023
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
References: 80
Accession Number: 2014-002372
Categories: GeochronologyEconomic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables, geol. sketch map
N53°00'00" - N55°00'00", W04°30'00" - W03°00'00"
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201403
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