Copper Canyon deposits, Copper Canyon, Hoskinnini Mesa, Navajo County, Arizona, USAi

Regional Level Types
Copper Canyon deposits	Prospect
Copper Canyon	Canyon
Hoskinnini Mesa	Mesa
Navajo County	County
Arizona	State
USA	Country

Localization of the uranium-copper minerals:
The mineral-bearing outcrops are confined to the channel structures eroded into the Moenkopi formation and filled with Shinarump sands and gravels. In the mapped area, 42 channel outcrops are now known; 18 have been examined and 24 have been observed by aerial reconnaissance and study of photographs, Of the 18 channels examined, 17 were found to be copper-bearing and 15 contained copper and uranium.

No uranium minerals have been found higher than 20 feet above the base of the channels and the best concentrations are in the lower 5 feet. In some channels, the copper minerals are confined to the lower part of the channel; in one, however, on the western side of Hoskinnini Mesa, abundant copper minerals were found frame the base upward through a vertical interval of 100 feet.

Uranium occurs as carnotite, filling interstices between the sand grains and as a replacement of fossil trees, twigs, and carbonaceous trash; copper occurs as chalcocite surrounded by halos of malachite, azurite, chrysocolla, and brochantite in bedding-plane seems and replacements of fossil woody material. It is believed that there is no constant ratio between copper and uranium, as some of the best copper deposits are low in uranium.

Size and shape of the deposits:
The mineralized deposits, being confined to fossil channel-bottoms, are elongated along the courses of the channels. As the channels are roughly U-shape, the mineralized portions are not as large as the tops of the channels. A channel 1000 feet wide at the top probably nowhere contains more than 1000 to 1100-foot widths of mineralized material at its base. As uranium minerals have, in no locality, been observed higher than 20 feet above the channel base and are, in some places, confined to horizons as thin as a few inches, it is believed that the average thickness of the ore does not exceed 10 feet.

Drilling near the Monument No. 2 mine and elsewhere in the Monument Valley region has indicated that ore occurs in lenses in the channels, and that about 6% of the total length of a channel is mineralized.

Lateral extent of the deposits:
Several channels have been observed crossing promontories on Hoskinnini Mesa; others have been projected across the mesa; several of them have been observed entering Nokai Mesa on the western side of Copper Canyon. Those channels which have been projected with a reasonable assurance of
accuracy embrace a surface area of 3.8 square miles. In the entire Copper Canyon district, it is calculated that 38 square miles of the surface is underlain by channels, of which about 2.25 square miles may reasonably be expected to be mineralized.

Grade of the material:
A face of ore 40 feet long by 5 feet thick opened by Navajos on the western side of Copper Canyon averages 0.35% U308. Samples assaying from 0.10% to 0.66% U308 have been obtained from widely separated points. Copper assays as high as 18% have been obtained. A copper-bearing outcrop 100 feet high on the eastern side of Copper Canyon appears, from visual examination, to contain a minimum of 1% copper. Sane of the uranium-bearing outcrops, on the other hand, are quite low in copper content. From data now at hand, it seems likely that the grade of material, if mined from 5 to 20 feet thick, might range around 0.10% U308 and 1.0% copper. These figures may have to be revised as drilling proceeds.