During the 1980s, before Congress passed the Arizona Desert Wilderness Act of 1990, the US Geological Survey funded a study of the mineral resource potential of the Harcuvar Mountains. USGS geologist Ed DeWitt (right) and then UC Santa Barbara graduate student Steve Richard (left) are shown leaving the helicopter to begin field mapping at the crest of the central Harcuvar Mountains, La Paz County.
The geology of the western Harcuvar Mountains is dominated by crystalline rocks, including high-grade Proterozoic gneiss and schist, strongly deformed and metamorphosed metaplutonic rocks of Jurassic and/or Proterozoic age, and geometrically complex intrusions of variably deformed Cretaceous Tank Pass Granite. Less abundant rock types include Paleozoic or Mesozoic quartzite and marble, Middle Tertiary mafic dikes and intrusions, and hydrothermal veins. (From Reynolds and Spencer 1993)
Online resources:
Gehrels, G.E. and Spencer, J.E. (eds.), 1990, Geologic excursions through the Sonoran Desert Region, Arizona and Sonora. Arizona Geological Survey, Special Paper-7, 202 p. (Harcuvar Mtns p. 66). https://library.azgs.arizona.edu/item/AGSP-1552429065059-537
Reynolds, J.S. and Spencer, E. J., 1993, Geologic Map of the Western Harcuvar Mountains, La Paz County, West-Central Arizona. Arizona Geological Survey Open File Report, OFR-93-08, 1 map sheet, map scale 1:24,000, 9 p. https://library.azgs.arizona.edu/item/AOFR-1552431436798-749
Photographer: Jon Spencer
Photo Date: circa 1984
Photo Location Accuracy: Approximately Located