Processes Influencing Critical Element Enrichment in Alkaline Magmatic Systems

The distribution of critical elements in the Earth’s crust is influenced by many processes across distinct geologic settings. The rare earth elements (REEs) are important components in many facets of our day-to-day life, for example, in permanent magnets, many electronics, and batteries in hybrid cars. Platinum group elements (PGEs) are important components in catalytic agents and are utilized in many industrial and electronic applications.

Despite critical element enrichment in many alkaline magmatic systems, our understanding of the igneous processes that influence their enrichment and distribution is limited. A better understanding of the igneous processes that control critical element concentrations in alkaline systems can aid in informing focused critical element exploration. This project aims to evaluate igneous processes that may influence the enrichment and distribution of PGEs and REEs within the alkaline magmatic system at the Rattlesnake Hills Alkaline Complex, Wyoming.

Broader impacts of this project include graduate student training, research experience for undergraduate students, and the development of 3D rock models and associated assignments for distribution to educators. This project is jointly funded by the Petrology and Geochemistry program and the Established Program to Stimulate Competitive Research (EPSCoR).

Alkaline systems show extreme variation in critical element enrichment (e.g., REEs, PGEs, Te, V, W, Ba, and F) and Au contents. The proposed project will evaluate potential controls on critical element enrichment at the Rattlesnake Hills alkaline complex (RHAC). End-member hypotheses for critical element enrichment include: 1) country rock control, potentially as crustal assimilation or hydrothermal scavenging and redistribution of critical elements from country rock, 2) liquid immiscibility, and 3) initial composition of alkaline magmas.

The project will document the igneous history of the RHAC, distinguishing timing and sources of igneous units and their relationship to mineralization. Geochemical and isotopic data will be collected to evaluate the input of critical elements from country rock. The role of liquid immiscibility will be investigated through the use of geochemical and melt inclusion data.

Despite recognition of economic enrichment in alkaline systems for over 100-years, the processes that control critical element enrichment within these deposits are unclear. Understanding these controls will better elucidate the evolution of shallowly-emplaced, mantle-derived melts, the cycling of critical minerals in the upper-crust, and inform targeted exploration for critical minerals.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.