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C. A. Anderson

Publications and source records attributed to C. A. Anderson.

9 recordsLinked to original sources
USGS1972

Geology of the massive sulfide deposits at Jerome, Arizona; A reinterpretation

The massive sulfide deposits at Jerome, consisting largely of pyrite, chalcopyrite, and sphalerite, are concordant stratabound lenses in massive quartz-bearing crystal tuffs of Precambrian age and overlying bedded tuffaceous rocks. The crystal tuffs were eraplaced as submarine pyroclastic flows. The evidence permits the interpretation that the massive sulfide lenses are essentially syngenetic and related to hydrothermal brines that discharged into a submarine basin. The host rocks and sulfide lenses were folded and metamorphosed. Two periods of folding can be recognized; during the second period, the older folds were deformed along vertical axes, and some of the chalcopyrite in the major lens migrated downward to form shoots of intersecting veins in the crystal tuff and chloritized tuff (black schist). Fluid inclusions in volcaniclastic and vein quartz appear to be related to deformation and metamorphism and provide no direct evidence on the nature of the primary fluids that presumably introduced the ore metals to the volcanic rocks accumulating on the sea floor. Liquid CO2-bearing inclusions are restricted to rocks and veins near the United Verde deposit and associated chalcopyrite ore shoots. Fluids at that time were CO2-rich, with temperatures of approximately 235 ø C and confining pressures of about 700 bars or less.

Arizona↗
USGS1968

Metamorphosed precambrian silicic volcanic rocks in central Arizona

Silicic volcanic rocks — dacite, rhyolite, and quartz porphyry — constitute about 35 percent of the Yavapai Supergroup, an older Precambrian sequence in central Arizona. In addition, the series contains about 30 percent pillow and amygdaloidal basalt, 5 percent andesitic rocks, and the remainder is mixed andesitic and silicic-bedded tuffaceous rock. The Yavapai Supergroup is divided into the Ash Creek and Alder Groups, each containing about 20,000 feet of lavas and pyroclastic rocks; no evidence is available to determine the relative ages of the two groups. The pillow basalts, coarsely graded volcanic breccias, and poorly sorted and graded tuffaceous-bedded rocks suggest a marine accumulation in an eugeosyncline. The Yavapai Supergroup is metamorphosed to the greenschist facies. The Ash Creek Group exhibits open folds but is nonfoliated except locally, whereas, the Alder Group is isoclinally folded and dominantly schistose. Twenty-five chemical analyses of the metamorphosed, silicic volcanic rocks reveal varying ratios of sodium and potassium. By comparison with young rhyolitic obsidians, only two rhyolites approach the ratios and total alkali content found in recent obsidians. Five rhyolites contain more sodium and appreciably less potassium, whereas none of the rhyolitic rocks contain more potassium than in young obsidians. High-sodium content is reflected by much albite, and high-potassium content by abundant sericite. Iron-magnesium metasomatism locally has produced much chlorite associated with an increased quartz and decreased albite content. The source of the iron and magnesium may be underlying pillow basalts. Many rhyolitic rocks of Phanerozoic age display variable ratios of Na 2 O and K 2 O caused by hydration of obsidian, hot spring action, and hydrothermal solutions. The redistribution of the alkalis in the Yavapai Supergroup may be caused in part by factors other than regional metamorphism. It is suggested the H 2 O + content, averaging between 5 and 6 percent by volume in these metamorphosed silicic rocks, may be derived in part from interstitial marine water.

Arizona↗
USGS1958

Geology and ore deposits of the Jerome area, Yavapai County, Arizona

The Jerome area, in central Arizona, includes the Mingus Mountain quadrangle and parts of the adjacent Clarkdale, Mayer, and Mount Union quadrangles. The largest copper mines in the area at Jerome are the United Verde Extension and the United Verde. The United Verde Extension, closed in 1938 and the United Verde closed in 1953. The Iron King mine at Humboldt, the most active mine in the area after 1953, produces lead and zinc.

Arizona↗
USGS1942

Reconnaissance survey of the Roberts Mountains, Nevada

The Roberts Mountains region, central Nevada, provides an excellent section of Paleozoic rocks ranging from Upper Cambrian to Permian. Major low-angle thrusting is indicated by deformed Ordovician strata resting on Paleozoics of varying age. Overlying a thick breccia zone, the upper thrust plate consists of sandstones, andesitic flows and tuffs, black shales, and bedded cherts (Vinini formation). Ordovician age of the Vinini is established on the basis of graptolite faunules. A belt of Lower to Middle Ordovician graptolitic facies similar to the Vinini formation crosses the Great Basin west of Roberts Mountains. Deposits of roughly the same age in the Roberts Mountains meridian and eastward are dominantly limestone, carrying distinct faunas. Axial planes of overturned folds in the thrust plate dip west, a further indication that the upper thrust plate moved from west to east. Minimum horizontal displacement is 16 miles. The date of thrusting is uncertain, but presumably was later Cretaceous or early Tertiary. Following thrusting, an alaskite stock and rhyolite porphyry plugs were intruded; lava flows and tuffs covered the area in part. Thrust plate and cover of volcanics have been broken into normal fault blocks. The post-thrusting igneous rocks, like volcanic rocks of Utah and New Mexico, are characterized by high potash content.

Nevada↗