Abstract The silver and gold deposits of the world-class Palmarejo district are typical intermediate sulfidation-style epithermal precious metal occurrences hosted in Cretaceous- to Tertiary-age volcanic and intrusive rocks, of the Lower Volcanic Complex (LVC), and now host one of the newest and largest silver and gold producers in Mexico. The district, along with a surface and underground mine and new 6,000 tpd ore processing facility, is owned and operated by Coeur dâ∈™Alene Mines Corporation through its wholly owned subsidiary, Coeur Mexicana S.A. de C.V. Palmarejo is located in the southwest portion of the State of Chihuahua in the Sierra Madre Occidental (SMO) epithermal belt (Fig. 1).

Abstract The Jurassic sequence of northeastern Mexico includes Oxfordian through Tithonian-aged marine sediments that were deposited in eight environments: (1) sabkha, (2) nearshore, (3) lagoonal, (4) shoal, (5) inner-shelf, (6) restricted-shelf, (7) open-shelf, and (8) pelagic. Lithologic correlations relate the sections studied with the type sections of coeval rocks described from the Sierra de Parras. Based on their lithic characteristics they are assigned to the Minas Viejas, Zuloaga, La Gloria, La Caja, La Casita, and San Angel Formations. Three biohorizons are established: (1) the first stratigraphic occurrence of the ammonite Idoceras in the early Kimmeridgian, (2) the first appearance of calpionellids in the middle Tithonian, and (3) the first occurrence of Calpionella elliptica Cadish at the Jurassic/Cretaceous boundary. Two lowerings of sea level are identified in the sections studied, the first in early Kimmeridgian and the second in the early Tithonian. These two drops of sea level are separated by a sea-level rise in the middle Tithonian. Eustatic changes of sea level are associated with tectonism in the area. Active transform faulting in the Gulf of Mexico region resulted in the juxtaposition of Oxfordian-Kimmeridgian shallow- and deep-water facies. The translations along transcurrent faults result in a SE-NW displacement of about 300 kilometers, which caused the formation of the Sabinas Basin of northeastern Mexico. Late Jurassic sea-floor spreading in the central Gulf of Mexico is regarded as the driving mechanism. The Oxfordian-Kimmeridgian and late Tithonian paleogeographies of northeastern Mexico are reconstructed, and parallel lineal facies belts are envisioned which account for the sporadic distribution of the Jurassic shallow-water facies in northeastern Mexico.