Extension of Laramide magmatism in southwestern North America into Trans-Pecos Texas

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.