Western Mineral Resources
View to the west from the Scenic Loop Drive south of the town of Ajo. The hill at right shows pronounced layering in the Oligocene-Miocene Locomotive Fanglomerate. The sharp peak in the distance is North Ajo Peak, formed by units of the Miocene Ajo Volcanics.
The Ajo porphyry copper deposit and surrounding Upper Cretaceous rocks have been separated from their plutonic source and rotated by detachment faulting. Overlying middle Cenozoic sedimentary and volcanic rocks have been tilted and show evidence for two periods of rotation. Following these rotations, a granitic stock (23.7±0.2 Ma) intruded basement rocks west of the Ajo deposit. This stock was uplifted 2.5 km to expose deep-seated Na-Ca alteration.
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