Closing the Iapetus Ocean: late arc and ophiolite formation in the Grampian Orogeny and implications for UK mineral potential and metal security

Dr Steven Hollis, University of Edinburgh

The Grampian Orogeny marks the first phase of the closure of the Iapetus Ocean in the British and Irish Caledonides during the Late Cambrian to Middle Ordovician. Widespread metamorphism and deformation of passive margin sequences resulted from the accretion of several arc and ophiolite complexes (and outriding microcontinental blocks) to the continental margin of Laurentia. These remnants of that now closed ocean extend across Scotland and Ireland, into Newfoundland and Quebec. The Tyrone Igneous Complex of Northern Ireland represents a young, structurally dissected c. 484-480 Ma ophiolite and c. 473-464 Ma volcanic arc. Extensive fieldwork, geochemistry, isotope analysis (Sr-Nd), and U-Pb zircon geochronology have provided us with a detailed understanding of its tectonic-magmatic evolution, and potential metal endowment. Equivalent sequences in the Newfoundland Appalachians contain some of the most metal-rich massive sulphide deposits globally. Exploration efforts in Co. Tyrone have revealed numerous encouraging occurrences of base (Cu-Zn-Pb) and precious (Au-Ag) metals crucial for the energy transition, and also occurrences of energy-critical metals (e.g. Co, Bi, Te). Parallels between the Tyrone Igneous Complex and the Ballantrae Ophiolite Complex will also be discussed in this presentation, highlighting the possible mineral potential of western Scotland.

Steven is lecturer in ore systems at the University of Edinburgh. He completed his undergraduate degree at the University of Birmingham in 2007, before completing an MSc in Geochemistry at the University of Leeds in 2008. His PhD at the University of Southampton focused on the evolution and mineralization of the Tyrone Igneous Complex of Northern Ireland. He then undertook postdoctoral positions at CSIRO in Western Australia on developing new exploration techniques for VMS deposits in the Yilgarn Craton of Western Australia, and at University College Dublin, Ireland, on the applications of clumped C-O and Pb isotopes to carbonate-hosted Zn-Pb deposits of the Irish Midlands.