EGS Lectures 2023 - Dr Steven Hollis, University of Edinburgh

Dr Steven Hollis, Lecturer in Ore Systems
School of Geosciences, University of Edinburgh

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

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.