865 IMPROVING MINE–PLANT RECONCILIATION THROUGH ONLINE GRADE MEASUREMENT ON THE CONVEYOR BELT: A CASE STUDY FROM CHUQUICAMATA UNDERGROUND *P.S. Peñaloza1, C.A. Córdova2 ¹Production Management Superintendence, Mineral Resources and Development Department, Chuquicamata Division, Codelco, Chile, ppena018@codelco.cl 2Production Management Superintendence, Mineral Resources and Development Department, Chuquicamata Division, Codelco, Chile, ccord004@codelco.cl ABSTRACT Chuquicamata Division faces the challenge of improving mine–plant reconciliation in a context of multi-source ore processing and transition to underground mining. Currently, feed grade estimation relies on discrete sampling, which, together with time delays and blending effects, results in discrepancies on the order of 0.01% to 0.02% CuT between mine-reported grades and those reconciled in the metallurgical balance, with significant economic impact. In valuation terms, a deviation of 0.01% CuT is estimated to represent approximately USD 1.4 million per 1.7 Mt processed, considering a 90% recovery and a copper price of around USD 4.0/lb. This work presents the technical and economic evaluation of a solution based on the implementation of an online grade analyzer on the Overland conveyor at Chuquicamata Underground, aimed at reducing this gap. The evaluation considers the capability for continuous, real-time measurement of elements such as Cu, Mo, Fe, and As, as well as its integration into operational control systems. The methodology includes initial calibration using representative ore samples, validation under controlled conditions, and comparison with laboratory assays and metallurgical balance data. Based on the results obtained, which demonstrate the potential of online measurement to reduce the mine–plant gap and its associated economic impact, it has been decided to proceed with the system implementation during the present year. The project is currently in the permitting and calibration phase. The results of this evaluation highlight the potential of online measurement to improve ore traceability, reduce uncertainty in grade estimation, and enable more timely and data-driven operational decision-making. KEYWORDS Mine–plant reconciliation, underground mining, online analyzer, elemental grades 1. CONTEXT AND PROBLEM STATEMENT Chuquicamata Division is a copper mining operation, with molybdenum as a by-product, located approximately 15 km north of the city of Calama, in the Antofagasta Region, Chile. The division is currently undergoing a transition from its historical open-pit operation to an underground mining scheme using the conventional panel caving method. This structural project, initiated in 2019, includes the operation of three main macroblocks (N1S1, N2N3, and S2S3) and aims to extend the life of the deposit by at least 40 years (Barindelli, López & Quiroz, 2004; Barindelli, Gálvez & Guerra, 2026). One of the main challenges associated with this transition is achieving production ramp-up under highly complex operational conditions. A key characteristic of Chuquicamata Division is that its concentrator plant processes ore from multiple sources: Chuquicamata open pit, Chuquicamata Underground, and Radomiro Tomic sulfides. This condition creates a blending scenario involving ores with different geometallurgical characteristics, where reporting reliability becomes critical. In particular, accurate estimation of feed grades is essential for constructing reliable metallurgical balances, controlling the process, and ensuring proper valuation of the processed material. From the Production Management perspective, it is essential to rely on robust methodologies that
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