Fault and fracture networks as long-lived conduits for lithium transport

Abstract. Lithium brine systems are critical resources for the energy transition, yet the mechanisms governing lithium mobilization, transport, and concentration remain poorly constrained. In particular, the role of fault and fracture networks in controlling fluid flow and lithium distribution is not well resolved. Here we investigate the structural controls on lithium transport in Clayton Valley, Nevada, a key lithium-producing basin in the USA. We present new analyses of calcite-mineralized faults, opening-mode fractures, and spring deposits that record lithium-bearing fluid flow over >10 Myr of Basin and Range extension. Hereafter, opening-mode fractures are referred to as “fractures,” and mineral-cemented faults or fractures as “veins.” Calcite U–Pb ages (15–4 Ma), clumped-isotope formation temperatures (25–140 °C), and lithium concentrations (up to 460 ppm) demonstrate that fault and fracture networks repeatedly transported lithium-bearing fluids through basement, along basin margins, and within basin fill throughout basin evolution. Lithium concentrations vary systematically with host setting, with the highest values recorded in basin-fill-hosted veins and spring deposits and generally lower values in basement-hosted and basin-bounding fault veins. Several lithium-bearing calcite veins yield U–Pb ages that predate emplacement of late Miocene silicic volcanic units by up to ~9 Myr, demonstrating that structurally focused lithium transport occurred prior to emplacement of widely cited volcanic source reservoirs. Temperature and stable isotope constraints indicate dominantly meteoric fluids advected to depth and focused along faults, suggesting that lithium transport and enrichment in Clayton Valley does not necessarily require ascent of lithium-enriched magmatic fluids along deeply rooted crustal-scale faults. These results show that long-lived fault and fracture networks act as persistent pathways for lithium transport and redistribution within closed extensional basins. Although fault-controlled lithium enrichment has been recognized previously, this study provides direct evidence for structurally focused lithium transport over multi-Myr timescales.