Abstract

The Red Hills intrusion hosts the easternmost porphyry copper-molybdenum system in southwestern North America and consists of quartz-sulfide stockwork veins in sericitized porphyritic quartz monzonite. Zircon U-Pb and molybdenite Re-Os analyses yield ages of 64.2 ± 0.2 Ma and 60.2 ± 0.3 Ma, respectively, indicating that the Red Hills intrusion and mineralization are distinctly older than all other Tertiary magmatism (48–17 Ma) in the Trans-Pecos region of Texas, including the nearby 32 Ma Chinati Mountains caldera. The Red Hills intrusive system is contemporaneous with and genetically related to other Laramide magmatic systems (75–54 Ma) that host porphyry copper deposits in Arizona, southwestern New Mexico, and northern Mexico. These results significantly extend the Laramide magmatic province eastward and suggest that Laramide subduction-related magmatism and deformation are coextensive over a broad area of southwestern North America.

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