Navajo volcanic field

The volcanic field consists of over 80 volcanoes and associated intrusions of unusual potassium-rich compositions, with an age range of 26.2 to 24.7 million years (Ma).

Geologists have studied the Navajo volcanic field for clues to the geologic history of the Colorado Plateau and the timing and cause of its uplift.

[1] Geologically, these erupted in a short time interval, between 26.2 and 24.7 million years ago, based on high-precision Ar-Ar dating of samples from the field.

[1] At some vents, the diatreme-eruptions excavated the country rock to depths as great as 1,000 meters (3,300 ft) below the original ground surface.

The high potassium content of the magma erupted in the province suggests that potassium-rich fluids from the disintegrating Farallon Plate beneath the Colorado Plateau had risen into the overlying mantle wedge.

Other rare rock types found in a few locations in the Navajo volcanic field include monchiquites (sodium-rich lamprophyres), olivine melilites, and katungite, the latter having a silica content as low as 33.6 percent.

[9] Xenoliths erupted at The Thumb, a small vent near Shiprock, were mantle rock entrained by the magma at a depth close to 130 kilometers (81 mi) and at a temperature of about 930 to 1,230 °C (1,710 to 2,250 °F).

[12] The Chacoan civilization included vents of the Navajo volcanic field, such as Shiprock, Bennett Peak, and Ford Butte, in their system of sacred geography.

Shiprock , a volcanic neck of the Navajo volcanic field