Building decarbonised energy and transport infrastructure requires a diversity of raw materials, including the rare-earth elements (REE), Nb, Cu, Co and Li, demand that is increasing rapidly and cannot be met by recycling alone for some decades. Our understanding of the mineral systems for many of the commodities is poorly integrated across spatial scales and effective study will require a variety of approaches. Alkaline-silicate igneous systems host the world’s largest deposits of REE, which are essential ingredients of high-strength permanent magnets. Metal enrichment in alkaline systems is the result of extensive crystallisation of mantle-derived alkali-rich mafic melts. However, it remains uncertain why within individual alkaline igneous provinces some of the intrusive complexes host mineralisation, whilst others are barren. One possibility is that variation in the primary melt composition, fractional vs. batch crystallisation, and the temperature-pressure pathway through which magma cools, will generate a mineral assemblage that either effectively rejects the REE, facilitating their residual enrichment and possible mineralisation, or sequester the REE in low — and thus uneconomic — concentrations in early-formed igneous cumulates. Another possibility is that barren alkaline-silicate systems may have lost their metal tenor via immiscible separation of carbonatite melts.

This field project will collect suites of samples to test the relative importance of the above processes in the generation and preservation of REE enrichment in alkaline silicate magmatic systems. A process-based understanding of the alkaline-silicate REE mineral system will inform exploration for large and high-grade mineralisation.

• Owen Weller
• Caroline Soderman
• Corinne Frigo
• Adrian A. Finch

Northern lakes are the largest natural sources of methane, a potent greenhouse gas, but it is unclear how and whether feedbacks from warming in Arctic regions will exacerbate or mitigate lake methane emissions. This proposal investigates two potential drivers of methane emissions, which are rapidly changing as the Arctic warms: (1) the composition and quantity of dissolved organic matter (DOM) transported into lakes from the land as vegetation changes and permafrost melts, and (2) the increasing quantities of windblown (aeolian) dust that is released from glacial discharge as the Greenland ice sheet melts. We hypothesize that DOM and dust are the key drivers of methane emissions. DOM is the dominant external source of carbon to lakes with the potential to fuel the methane cycle. Aeolian dust is a source of nutrients that drive microbial activity and, particularly, rare earth elements (REE) from the lanthanide group which are enzymatically-linked to methanotrophy. Understanding how such changes and interactions between DOM and dust/REE influence methane emissions requires approaches from different scientific fields. Methane cycling is powered by microbes and their interactions, but the lake conditions, trophic structure and environmental situation will modify the supply, distribution and bioavailability of elements that support the methane cycle over a variety of timescales and climatic conditions. This consortium focuses on a well-studied lake district as a living laboratory in West Greenland, and assembles experts in the microbiology of lanthanide-dependent methanotrophs, microbial and lake ecology to investigate respectively how microbial interactions and higher trophic levels of the food web modify methane production. Combining limnology and paleolimnology (sediment core analysis) with citizen scientist work will allow linkages between DOM, dust/ REE supply and methane production to be quantified at the landscape-scale and across timescales of decades to centuries as a means of evaluating their broader biogeochemical significance.

• prof. dr. Friederike Wagner-Cremer
• dr. Wim Hoek
• prof. dr. Paul Mason
• prof. dr. Suzanne McGowan