Distinct Sulphur Saturation Histories of the Palaeogene Magilligan Sill, N. Ireland: Implications for Ni-Cu-PGE Exploration in the North Atlantic

Lindsay, J. J., Hughes, H. S.R., Andersen, J. C.O., Smyth, D., McDonald, I. and Boyce, A. J. (2019) Distinct Sulphur Saturation Histories of the Palaeogene Magilligan Sill, N. Ireland: Implications for Ni-Cu-PGE Exploration in the North Atlantic. In: 15th SGA Biennial Meeting on Life with Ore Deposits on Earth, Glasgow, Scotland, 27-30 Aug 2019, pp. 550-552. ISBN 9780852619636

Abstract

The similar to 60 m thick Northern Irish Magilligan Sill is a dolerite and olivine gabbro intrusion, thought to be connected to the Irish dyke swarm plumbing system that is part of the British Palaeogene Igneous Province (BPIP) in the North Atlantic. The sill has received interest as an exploration target for Ni-Cu-PGE sulphide mineralisation due to its morphological similarity to Noril'sk-Talnakh (Russia). We present new petrological, geochemical and S-isotope data for the sill, to assess its prospectivity and detail the underlying magmatic plumbing system. Most sulphides in the dolerite portions of the sill contain negligible PGE. In the olivine gabbros, sulphides contain significant PGE, Cu, Ni, Co and Ag. Pyrite from the dolerites have delta S-34 ranging from -10.0 to +3.4 parts per thousand and olivine gabbro sulphides range from -2.5 to -1.1 parts per thousand, suggesting widespread crustal contamination. The S/Se ratios of sulphides in the dolerites and olivine gabbros range from 3,500 to 19,500 and from 1,970 to 3,710, respectively, indicating that olivine gabbro sulphides may have come from upstream in the magma plumbing system. The Magilligan Sill records multiple injections of mafic magma into a single intrusive package, each with distinct mechanisms towards S-saturation. The divergence in S-saturation histories and metal contents suggest that a larger volume of olivine gabbro sulphides at depth may be prospective.

• Item Type: Conference Proceedings
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Boyce, Professor Adrian
• Authors: Lindsay, J. J., Hughes, H. S.R., Andersen, J. C.O., Smyth, D., McDonald, I., and Boyce, A. J.
• College/School: College of Science and Engineering > Scottish Universities Environmental Research Centre
• ISBN: 9780852619636