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A-team quarterly update

Juli – October 2019

Read up on our St Andrews Alkaline Magmas and Resource group activities here.

 

Alkaline Igneous Rocks of Angola, workshop and fieldtrip September 2019

3/10/2019

In September, the St Andrews team took part in a workshop and fieldcourse in Angola, hosted by the Universidade Agostinho Neto (UAN) in Luanda. The purpose of our trip was to outreach our work on alkaline igneous rocks and to learn more about similar rocks found in Angola. Our visit was funded by the SFC Global Challenges Research Fund. Read more about our visit here…

 

Sulfur Isotopes Paper Published in Nature Communications

16/09/2019

Our research led by Will Hutchison on sulfur isotopes of alkaline magmas is now published Open Access in Nature Communications. The work was led by the St Andrews team in collaboration with colleagues at Tübingen and Glasgow Universities. The group at St Andrews included four of our group (Will Hutchison, Adrian Finch, Nicky Horsburgh and Anouk Borst), our colleague Eva Stüeken (who works on chalcogen isotope fractionation) and Henrik Friis who is now Associate Professor at the University of Oslo.

Will compared the mantle signatures of Gardar magmas in Greenland with a compilation of data for alkaline igneous rocks across the globe. Variations in mantle sulfur signatures matched gross trends in the isotope values of the contemporary surface, which changed dramatically over Earth History. He concluded that the sulfur in the Gardar magmas contained a component that had been recycled from the Earth’s surface.

The exciting conclusion is that the Earth’s sulfur cycle contains a significant component of surface sulfur being recycled back into the mantle. Will’s work draws attention to how useful alkaline igneous rocks are as windows on the composition of the sub-continental mantle through geological time. 

IMG_0471

View from mile high cliffs on the Motzfeldt complex, Gardar South Greenland, one of the main sites for the study

Hutchison W, Babiel RJ, Finch AA, Marks MAW, Markl G, Boyce AJ, Stüeken EE, Friis H, Borst AM & Horsburgh NJ (2019) Sulphur isotopes of alkaline magmas unlock long-term records of crustal recycling on Earth. Nature Communications, 10, 4208.

Press Coverage

The work has received significant national press coverage including of the following:

New paper out in special Rare Earth issue of Minerals

10/07/2019

In this paper we quantify gains and losses of critical elements during late-magmatic hydrothermal alteration of eudialyte in the Ilimaussaq complex, Greenland. By microdrilling the alteration products of eudialyte – the primary host for REE, Zr and Nb – we found that certain metals (particularly those just mentioned) may be more mobile in the hydrothermal environment than we previously thought.

EudialyteAlteration-VandeVen et al 2019

Red kakortokite sample from Unit 0 showing relative proportions of fresh eudialyte (red, c. 30%), replacement products after eudialyte (brown, c. 30%) and remaining minerals (feldspar, nepheline, sodic amphibole, c. 40%)

The alteration led to significant losses in Rare Earths and other High Field Strength Elements, and small gains in Large Ion Lithophile Elements (Rb, Th, U). We suspect that the elements that were removed from eudialyte by the fluids re-precipitated elsewhere in the rock. As such we infer that the alteration did not significantly influence the overall ore grade of the deposit. However, it does influence the ease by which we can extract the metals from the rock, as the metals are now hosted in a plethora of fine-grained intergrowths of secondary minerals. This has important implications for ore potential and mineral processing schemes of eudialyte-hosted ores, if we are to exploit these as a future source for green-technology metals.

van de Ven Mathijs, Borst Anouk M, Davies Gareth R, Hunt Emma J, Finch Adrian A (2019) Hydrothermal Alteration of Eudialyte-Hosted Critical Metal Deposits: Fluid Source and Implications for Deposit Grade. Minerals 20199(7), 422; https://doi.org/10.3390/min9070422.  

The paper is the result of an MSc project by Mathijs van de Ven, co-funded by the University of St Andrews, the VU University Amsterdam and SOSRARE. Mathijs graduated at the VU University Amsterdam with distinction in 2018, and now works as an exploration geologist at RSC Mining & Mineral Exploration in New Zealand.

New Ilímaussaq isotope paper in Lithos

Jan 2019

Dating agpaitic rocks: A multi-system (U/Pb, Sm/Nd, Rb/Sr and 40Ar/39Ar) isotopic study of layered nepheline syenites from the Ilímaussaq complex, Greenland, Lithos. https://doi.org/10.1016/j.lithos.2018.10.037

Happy to announce that the last paper of my PhD is now published in Lithos. In this paper we investigate how late-magmatic fluid reactions affect initial isotopic ratios of different minerals and how this affects the accuracy of isochron age dating for peralkaline rocks.

Find a link to the paper here.

EGU Geochemistry, Mineralogy, Petrology & Volcanology Blog

Below is a link to a guest blog I wrote with Dr. Will Hutchison for the EGU Geochemistry, Mineralogy, Petrology & Volcanology website.

The Fractional Crystallization Freak Zone

Will is a fellow postdoctoral researcher here at St Andrews. He studies active volcanoes and ancient magma chambers, and is currently working on the roof zones of  alkaline magmatic systems in Greenland, as part of the Horizon2020 funded HiTech AlkCarb consortium.

Click here for the HiTechAlkCarb, website and blogs