Battery and Base Metals in Chilean Copper Mine Tailings: A National Screening of Cobalt, Nickel and Copper from Public Geochemical Data

Chile, the world’s leading copper producer, accumulates hundreds of tailings deposits whose battery metals were never a recovery target. We screened cobalt, nickel and residual copper across the national tailings inventory using the public geochemical survey of the Chilean National Geology and Mining Service (SERNAGEOMIN, ∼2100 surface samples), deriving representative compositions for 649 deposits integrated with the October 2025 cadastre. Each metal returns a different answer. Residual copper is ubiquitous (median 0.15%, above 0.2% in 260 deposits) and its indicative endowment of ∼24 Mt, where the impoundments are counted at their authorised capacity, or ∼20 Mt on the tonnage actually deposited, over 90% of it in twenty impoundments above 100 Mt, is the most robust target. Cobalt sits just below crustal abundance (median 14 g/t) but shows an enriched tail: 104 deposits exceed twice the crustal reference, up to 1080 g/t, concentrated in small, old deposits. A discontinuity in the source release splits the nickel determinations into two segments with medians of 70 and 7.9 g/t; chromium, vanadium and a regional soil background all place the lower segment on the rock, so nickel is reported over its 304 deposits, at a median of 7.9 g/t, one sixth of the crustal reference. Cu, Co and Ni are uncorrelated at the deposit level (ρ≤0.13), so surface geochemistry gives a plant no signal on which to base joint recovery. A comparison of surface against depth over twelve paired deposits also differs by metal: copper ordering is preserved, while the same twelve pairs are too few to resolve whether surface cobalt orders the interior. Assessing the battery metals of these tailings, therefore, requires sampling at depth, and the screening names the deposits where that campaign should start.