First published use. Name applied to a gray quartz-mica-diorite of granitic texture and habit. Consists of plagioclase feldspar (usually andesine), quartz, and biotite. Becomes a granodiorite in composition at some localities. Named for Mount Madera in the Pinal Mountains, Gila Co, AZ in Southwestern Basin-and-Range region. No type locality designated. Occurs on much of crest of Pinal Mountains, from northwest of Hog Ranch across Lyons Fork of Mineral Creek south to southern border of quad. Is the oldest intrusive rock in quad--older than Schultz granite as it is cut by dikes of the Schultz. Intrudes the Pinal schist. Considered pre-Cambrian age. Geologic map of Globe quad.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Geologic relations suggest Madera in the Southwestern Basin-and-Range region is older than the 1,400 m.y. Ruin Granite. Thought to be correlative with Willow Spring Granodiorite. Has K-Ar ages of 1,630 +/-60 m.y. and 1,578 +/-8 m.y., and 1,660 m.y. Has Rb-Sr whole rock age of 1,630 m.y. and 1,775 m.y. Age modified from Precambrian to Precambrian Y or X. Cross section.

Source: GNU records (USGS DDS-6; Denver GNULEX).