Geology topics

Research about Arizona, California, Colorado, Nevada, New Mexico, Utah

Source-linked reports with geographic coverage including Arizona, California, Colorado, Nevada, New Mexico, Utah.

20 records · Page 2Linked to original sources

USGS1964

Veins of hypogene manganese oxide minerals in the southwestern United States

Characteristic minerals are psilomelane, hollandite, cryptomelane, and coronadite, more rarely ramsdellite and pyrolusite. Host rocks are Mn-deficient; 80 percent of examples are middle to late Tertiary layered volcanics. Though deposits are shallow, mostly mined to only 100-200 feet (maximum 500 feet), a hypogene origin is indicated by their persistent association with barite and fluorite, a peripheral position in the zonal pattern of some metal-mining districts, alteration of plagioclase to K-spar, and abundance of W, Pb, Cu, Mo, Ti, As, Sb. They represent the subzone of Mn-bearing epithermal vein deposits lying nearest the surface, succeeded in depth by four other subzones: barite, fluorite, gold-silver, and base metals.

Arizona, California, Colorado, Nevada, New Mexico,↗

USGS1963

Effects of drought in the Colorado River basin: Chapter F in Drought in the Southwest, 1942-56

The prolonged drought of 1942-56 affected chiefly the lower part of the Colorado River basin and did not extend into the upper basin (the chief water-producing area) until 1953. Areas served by the Colorado River had adequate water supplies in spite of the local deficiency of precipitation. In the Gila River basin, there was a deficiency of streamflow during the drought years, and the water requirements of the present population exceed the yield of the basin even during years of average precipitation; the deficiency is overcome by mining of ground water.

Arizona, California, Colorado, Nevada, New Mexico,↗