The Tectonic, Thermal, and Temporal Controls on the Production of Lithium‐Enriched Melts

Abstract We present a new tectonically‐based method for understanding the mountain‐belt‐scale controls on the distribution of critical metals, applied to lithium ores. Lithium‐rich melts in collisional zones are produced by biotite‐breakdown reactions, so we analyze the tectonic “filters” that control whether underthrusting (meta‐)sediments reach sufficiently high temperatures for these reactions. Such conditions are most readily achieved with large crustal thicknesses, high radiogenic heating rates, and slow convergence. The first two factors indicate an important role for geological history, in terms of creating a strong foreland and assembling sufficiently radiogenic lithologies. Slow convergence is generally incompatible with uplift outpacing erosion to develop thick mountain belts, but this paradox is resolved by, and explains, most lithium deposits being formed late in the history of mountain belts, at times of slowing convergence rates. Our results explain why lithium deposits are more prevalent in preserved Precambrian mountain belts, formed during times of higher radiogenic heating. Plain Language Summary The energy transition is driving increasing demand for a variety of metals, including lithium. The controls on the large‐scale distribution of lithium, and other critical metals, are not yet established. In this paper we use a model for the thermal structure of continental mountain belts to establish the tectonic conditions that are able to generate lithium‐rich melts. Our results highlight the most important factors (crustal thickness, rate of radiogenic heating, rate of convergence), and by doing to provide an explanation for the documented distribution of economically‐viable lithium deposits. Our approach therefore provides a means to undertake range‐scale assessments of mineralization potential. This method can be applied to other critical metals (e.g., Sn, W) whose distributions are also controlled by temperature‐dependent melt processes in mountain belts. Key Points The tectonic filters controlling the production of lithium‐enriched melts The importance of crustal thickness, radiogenic heating, and convergence rate Explanations for the known distribution of lithium deposits, and a means for range‐scale assessments of mineralization potential