Challenges and opportunities for structural geologists in the critical minerals sector

Ben M. Frieman, Colorado Scool of Mines
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Abstract

The genesis of most mineral deposit types is fundamentally governed by structural and tectonic factors. This may include first-order controls imparted by the paleoenvironment and tectonic setting, as well as higher-order controls that arise from the structural regime at the time of transport, deposition, and economic accumulation of critical minerals. Despite advancements in the understanding of ore systems processes, geological interpretations remain hampered by fundamental grand challenges inherent to the ways in which we collect, interact, visualize, and interpret structural observations. Based on my experiences, I will convey structural problems spanning the mineral deposit life cycle, highlight significant impediments to effective interpretation of structural observation in 3D space, and suggest key experiential learning opportunities that may be easily integrated into existing structural geology and mapping coursework.
Structural geology grand challenges in critical mineral research are explored through a series of case studies. These case studies highlight that, while new technologies and data analysis approaches have helped facilitate novel research, they generate significant volumes of data, which complicate QA/QC procedures and interpretations of syn-mineral and/or pre-/post-mineral structural complexity. Case studies presented herein, include the Manhattan district, Nevada and at the San Albino deposit of Nicaragua. The Nicaragua study relied most heavily on open pit observations collected during active mining operations. Due to widespread Tertiary deformation related to development of the Caribbean plate, delineating this younger history was key goal. Several distinct structural episodes were identified from paired field observations and statistical analysis. Based on these results a Laramide aged contractional episode and a younger extensional to transtensional episode are identified. Both episodes affected the present-day distribution of mineral resources that formed in the mid-Cretaceous. In contrast, the Manhattan district project relied more heavily on digital mapping derived from drone-assisted 3D mapping using Mira Geoscience's HiveMap software. This approach facilitated more detailed mapping of highwall open pit exposures spanning hundreds of meters of vertical and lateral exposure. Statistical analysis defines the pre-mineralization structure, which provided local traps for later mineralizing fluids. The syn- to post-mineral history is dominated by brittle deformation that relates to Miocene extension leading to a transtensional regime. In general, each of these studies highlight that we have relatively few tools to effectively interrogate 3D geological data and few best practices exist for integrating structural data into quantitative analysis with other key defining parameters, like geochemistry of geophysical constraints.

Session

Deformation in the upper crust