The Maria deposit is about 10 km northwest of the town of Cananea, Sonora, Mexico, and about 160 km south of Tucson, USA. Cananea, a historic mining district dating from the 19th century, hosts one of the largest porphyry copper deposits in the world (>30 billion pounds Cu) (Titley, 1982, and Pierce et al., 1995). Mineralization is in an area of about 40 × 4 km and follows a northwest-striking belt of Laramide quartz feldspar porphyry stocks that includes significant historic production from related skarn deposits in carbonate rocks. Porphyry-related ores in the district occur in three types: supergene-enriched standard porphyry-style mineralization with grade in the order of 0.7% Cu, a number of large porphyry copper-related higher-grade (1–2% Cu) standard hydrothermal breccia pipes, and the unusual high grade (∼7% Cu) large La Colorada brecciated massive sulfide/silicate pegmatite ore body.

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