The growth and decay of a Paleogene Intrusive Complex, Isle of Skye

The full details of this project on the IAPETUS2 webpage (https://www.iapetus2.ac.uk/) will be available shortly. To apply for this position, use the following link www.gla.ac.uk/ScholarshipApp

For further information please contact: Darren Mark (SUERC, University of Glasgow) [Email Address Removed].

The project student will join the Caledonian Geochronology & Geochemistry Research Group (https://www.scottishisotopes.co.uk/) and be based fulltime at SUERC (https://www.gla.ac.uk/research/az/suerc/). Further project details can be found here: https://www.scottishisotopes.co.uk/postgraduate

PROJECT SUMMARY:

The Paleogene Igneous Complex, Isle of Skye has fascinated geologists for over 200 years, encouraging multiple field expeditions despite the steep, jagged peaks. The story of these hills begins more than 61 million years ago with volcanic activity during the initial opening stages of the North Atlantic Ocean. As North America and Europe ripped apart, large volumes of basalt lava were erupted from long narrow fissures on what is now the West coast of Scotland. As time went on, the volcanism became focused at several specific locations, creating large, central volcanoes. The remnants of these volcanoes can be observed today as either thick lava flows or large intrusive complexes and nested plutons (e.g., Cullins).

The emplacement and construction of such large plutons is a widely debated topic and controversies centre on (1) the origin of voluminous granites, and (2) how they are emplaced. These can be summarised as the source and the space problem. Models that have been hypothesised to address the source issue range from mostly partial melting of the crust to fractionation from basaltic sources, whereas models addressing emplacement mechanisms vary from km-scale diapiric rise to incremental emplacement of small magma batches.

Precise zircon U-Pb geochronology, however, suggests plutons are accreted by addition of small magma batches to the middle-upper crust over 10,000 to 100,000 year timescales. Subsequently, a complex of nested plutons can accumulate to form batholiths over 1,000,000 to 10,000,000 years. During these periods pulses of high magma flux can be followed by periods of relative quiescence with magmatic flare-up periods proposed to explain the non-linear growth of large batholiths.

In the field the surface (topographic) exposure of different phases of magmatic activity within such nested plutons may hinder the relative reconstruction of emplacement, however U-Pb geochronology applied to zircon offers a high-precision method to reconstruct the timescales of magmatic activity on the pluton, igneous intrusive suite, or bathoith scale. Ar/Ar geochronology on mineral phases from the same rocks can track cooling rates and periods of high heat flow as new magma batches are emplaced into the crust.

This PhD project aims:
(1) Use zircon U-Pb geochronology and isotopic variability (Hf and O isotopes) to precisely determine the timescales for emplacement of the Paleogene Igneous Complex, Isle of Skye.
(2) Document the development of a crustal thermal anomaly leading to increased crustal assimilation in the magmas and use Ar/Ar geochronology to detail the eventual cessation of activity and cooling of the intrusive bodies.
(3) Use different modelling techniques to quantify emplacement rates for the different phases of the Paleogene Igneous Complex, Isle of Skye.

STUDENT

The project requires a student from a geological background who has a desire to combine field observations with precise and accurate laboratory measurements (geochemistry and geochronology). Experience of field mapping, numerically literate and demonstrable ability to work with isotope data are key. The student will be immersed in the Caledonian Geochronology & Geochemistry Research Group at the Scottish Universities Environmental Research Centre (SUERC), which currently includes 6 PhD students, 2 post-doctoral researchers and 4 research technicians. Working with CASE partners Thermo Scientific will allow the student to get direct experience in the mass spectrometer industry, including high precision design of cutting-edge instrumentation. During the course of the PhD the student will spend 3 months in Bremen, Germany and 2 months at Purdue University.