CIENEGA MINING DISTRICT

THE VOLCANIC ROCKS OF THE BUCKSKIN MOUNTAINS CROP OUT AT BUCKSKIN STATE PARK AND CROSS  THE COLORADO RIVER INTO CALIFORNIA AS THE WHIPPLE MOUNTAINS.

The Buckskin Mountains lie northeast of Parker, Arizona, with the range extending to the Colorado River, and in fact crossing the river to California where they are known as the Whipple Mountains.  Parker is about 28 miles south of Lake Havasu City and about 50 miles north of Blythe, CA.  The Buckskins are part of the Basin and Range Physiographic Province and related to extensional tectonics (as opposed to compressional tectonics as seen in the Colorado Front Range).  The range also displays the Buckskin-Rawhide Detachment Fault, a large, very low angle (sub horizontal) normal fault. The upper plate, or hanging wall, rocks consist of tilted syntectonic (deposited at time of uplift), mid-Tertiary sedimentary and volcanic units and deformed and metamorphosed Mesozoic and Paleozoic sedimentary and volcanic units. The lower plate, or footwall, is composed of metamorphosed crystalline and metasedimentary (sedimentary rocks changed because of metamorphism) units (Hawkins, 2010).  The geology seems quite complex, at least to me, and it is difficult to understand the mechanisms associated with mineralization!

A large mining district, the Cienega, lies within the Buckskins, and is described as a Cu-Au-Ag-Pb-Hg-W-Ba mining area (Hawkins, 2010).  The major target was (and is?) copper; however, significant amounts of gold and silver have been produced in past years (Scott, 1989). These deposits have produced, in total, about 52 million pounds of copper 15,500 ounces of gold, and a few hundred ounces of silver (Keith and others, 1983).

 Mineral deposits are widely distributed in the Cienega District and most occur along, or within a few feet, of the detachment fault, or along the other numerous small scale normal faults.  In hiking around the area I have seen mines located in basalt, in vuggy, almost cave-like limestone (partially metamorphosed), along breccias zones in various units,  along massive quartz veins, and in metamorphosed crystalline rocks.  Interesting minerals I noted included crystalline calcite, barite, chrysocolla, and specular hematite.  I was looking for fluorite, azurite and malachite---but, no luck.

REFERENCES CITED

Hawkins, W., 2010, Geological Report on eagle Nest Mining Claims, La Paz County, Arizona, United States: privately printed for Converge Global. Inc., Toronto, Ontario.

Keith, S.B., Gest, D.E., DeWitt, Ed, Woode Toll, Netta, and Everson, B.A., 1983, Metallic Mineral Districts and Production in Arizona:

Arizona Bureau of Geology and Mineral Technology Bulletin 194.

Scott, D. C., 1989, Mineral Investigation of the Gibraltar Mountain Wilderness Study Area (AZ-050-O12), La Paz County Arizona: U. S. department of the Interior, MLA 18-89..

mike 

OLD MINE ADIT FOLLOWS BRECCIA AND FAULT ZONES IN PALEOZOIC LIMESTONE. NOTE RECRYSTALLIZED ZONE OF PURE WHITE CALCITE.

MINE ADIT INTO VUGGY PALEOZOIC LIMESTONE.

MINE ADIT FOLLOWS BRECCIA AND FAULT ZONES IN TERTIARY VOLCANICS.

LARGE PIECES OF CRYSTALLINE BARITE ARE COMMON IN UPPER PLATE VOLCANIC ROCKS.

LARGE SCALE COPPER MINING IN PRECAMBRIAN GNEISS.

MAGENTA BLOOMS OF BEAVERTAIL CACTUS LIGHT UP THE DESERT.