42-6 Timing and Processes leading to Exhumation and Supergene Profile Formation at Buenavista del Cobre Porphyry Copper Deposit: A Thermochronological Study

Session: Cordilleran Mineral Systems: Interdisciplinary Perspectives on Critical Metal Ore Deposits

Presenting Author:

Authors:

Abstract:

The Buenavista del Cobre deposit in the Cananea Mining District (Sonora, Mexico) is a world-class Cu-Mo porphyry system with a well-developed supergene enrichment profile. This study represents the first integrated application of low-temperature thermochronology and supergene mineral geochronology to a porphyry copper deposit in Mexico and the broader southwestern North American copper province. We combine apatite fission-track and apatite (U-Th-Sm)/He thermochronology with thermal history modeling and 40Ar/39Ar dating of supergene alunite and jarosite to reconstruct the exhumation history and temporal evolution of supergene enrichment at Buenavista del Cobre. Thermochronological data indicate that currently exposed intrusive rocks experienced extremely slow exhumation (3–40 m/Ma) prior to approximately 25 Ma. Supergene mineral geochronology reveals three distinct episodes of oxidation and enrichment: 25–16 Ma, 11–8 Ma, and 6 Ma to present. When integrated with a regional compilation of supergene ages, our results indicate that climate, rather than tectonics, exerted primary control on exhumation rates and supergene profile development. Although Basin and Range extension did not drive exhumation directly, it enhanced crustal permeability and facilitated supergene fluid circulation, thereby contributing indirectly to enrichment processes. This interpretation challenges the prevailing regional paradigm that attributes supergene enrichment primarily to tectonically driven exhumation. Our thermal history modeling demonstrates that the Buenavista del Cobre intrusive complex experienced limited erosional removal since its emplacement. This preservation substantially increases exploration potential for deeper hypogene copper mineralization, particularly potassic alteration-hosted ore zones that may remain unrecognized. Our findings underscore the value of thermochronology for evaluating preservation state in porphyry copper systems, optimizing deep exploration strategies, and reassessing resource potential in existing districts amid escalating global copper demand.

Geological Society of America Abstracts with Programs. Vol. 58, No. 3, 2026

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