Saturday, October 29, 2016

Arizona's Mining Districts and Mines


Gold Basin District

Hey! Is that really Tony Beets? Nope, this is a dredge we visited in 1989 in Flat,
Alaska the year after our geology team with WestGold
  found one of the largestgold deposits in history at Donlin Creek, Alaska in 198
Many dry gold placers lie along the eastern edge of the White Hills and extend east to Hualapai Wash in Mohave County of northwestern Arizona (T28 & 29N, R17 & 18W). These are known as the Gold Basin placers. Get on your Google Earth and search for "Gold Basin, AZ" and hopefully, you will arrive in the middle of Gold Basin a short distance to the east and south of the many dry gold placers known in this basin.

The area lies south of Lake Mead, the Lake Mead Recreation area, and the Colorado River. The nearest communities are Meadview (36o00’00”N; 114o04’00”) and Dolan Springs (35o35’25”N; 114o16’25”W). Due to the large number of retirees and snowbirds settling in the region, each community is surrounded by extensive suburbs.

The placers are all dry placers in a desert, and these have detrital gravels that are only 1 to 5 feet thick that mostly lie on hard, false, bedrock of consolidated gravel cemented by caliche. The overlying gold-bearing gravels are weakly mineralized, and have considerable black sand and quartz with rock fragments of schist and gneiss eroded from the Precambrian terrain in the White Hills. 

The gold content of the placers is poor and may only be 0.03 to 0.04 ounce per cubic yard at best; while the underlying consolidated gravel remains unexplored. Gold nuggets are rare. Some up to an ounce have been found with the largest being only 4 to 5 ounces in weight (Nevada Outback Gems website). Much of the gold-bearing area is part of the White Mountains alluvial fan that extends from the eastern flank of the uplifted White Hills to Haulapai Wash to the east. The fan covers a surface area of 6 by 5 miles and you can drive to the area northward on the Pierce-Ferry highway (Road 25) through Dolan Springs. 

Lode gold was discovered in quartz veins in Precambrian rock in the 1870s. Placer gold from the veins was not found until the Great Depression. In 1932, W. E. Dunlop found gold in the dry gravel which attracted others. The amount of gold recovered by the prospectors was minor. Even experienced miners only made about $1 per day (1933 wages). And the total amount of reported gold recovered from the Gold Basin placers is only 415 ounces produced during the period of 1934-49.  To put this in perspective, this is equivalent to only one clean-up on Tony Beet's dredge in the Yukon!

The gold-bearing gravels occur in arroyos and gulches at elevations of 3,300 to 2,900 feet. The gravels have medium-grained, angular schist and gneiss fragments with a minor amount of finely divided quartz. A small number of boulders are encountered that are generally less than 2 feet in diameter. The gold occurs as flour gold and less commonly as angular nuggets with some gold attached to black schist particles. The White Hills, which are made up of granitic, schistose, and volcanic rocks, contain many argentiferous and auriferous quartz veins that are the likely source for much of the Gold Basin gold (Wilson, 1981).

The gold placers have erratically distributed gold. In addition to dry placer mining, there is considerable prospecting with metal detectors. Some find gold, while others have found a bonus of meteorite fragments (Nevada Outback Gems website).

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