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W. N. Sharp

Publications and source records attributed to W. N. Sharp.

15 recordsLinked to original sources
USGS1987

The Conterminous United States Mineral Assessment Program: Background information to accompany folio of geologic and mineral resource maps of the Silver City 1° x 2° quadrangle, New Mexico and Arizona

The Silver City 1° x 2° quadrangle, consisting of about 20,650 km2 in southwestern New Mexico and southeastern Arizona, has been investigated by a multidisciplinary research team for the purpose of assessing its mineral resource potential. The results of this investigation are in a folio of 21 maps that contain detailed information on the geology, geochemistry, geophysics, mineral deposits, and potential mineral resources of the quadrangle. This Circular provides background information on the various studies and integrates the component maps. It contains an extensive selected bibliography pertinent to the geology and mineral deposits of the quadrangle. The quadrangle has produced more than $3.5 billion in mineral products since about 1850 and contains significant resources of gold, silver, copper, molybdenum, lead, zinc, iron, manganese-iron, zeolite minerals, and possibly tin and tungsten.

Arizona, New Mexico↗
USGS1975

The Pikes Peak batholith, Colorado front range, and a model for the origin of the gabbro-anorthosite-syenite-potassic granite suite

This study of the Pikes Peak batholith includes the mineralogy and petrology of quartz syenite at West Creek and of fayalite-bearing and fayalite-free biotite granite near Mount Rosa; major element chemistry of the batholith; comparisons with similar postorogenic, intracratonic, sodic to potassic intrusives; and genesis of the batholith. The batholith is elongate in plan, 50 by 100 km, composite, and generally subalkalic. It was emplaced at shallow depth 1,040 m. y. ago, sharply transects its walls and may have breached its roof. Biotite granite and biotite—hornblende granite are predominant; quartz syenite, fayalite granite and riebeckite granite are present in minor amounts. Fayalite-bearing and fayalite-free quartz syenite, fayalite-biotite granite and riebeckite granite show a well-defined sodic differentiation trend; the less sodic fayalite-free granites exhibit a broader compositional range and no sharp trends. Crystallization was largely at P H2O < P total ; P H2O approached P total only at late stages. Aplite residual to fayalite-free biotite granite in the north formed at about 1,500 bars, or 5 km depth. Feldspar assemblages indicate late stages of crystallization at about 720°C. In the south ilmenite and manganian fayalite indicate f O2 of 10 −17 or 10 −18 bars. Biotite and fayalite compositions and the ‘granite minimum’ imply completion of crystallization at about 700°C and 1,500 bars. Nearby fayalite-free biotite granite crystallized at higher water fugacity. All types of syenite and granite contain 5–6% K 2 O through a range of SiO 2 of 63–76%. Average Na 2 O percentages in quartz syenite are 6.2, fayalite granite 4.2, and fayalite-free granite 3.3 MgO contents are low, 0.03–0.4%; FeO averages 1.9–2.5%. FeO/Fe 2 O 3 ratios are high. Fluorine ranges from 0.3 to 0.6%. The Pikes Peak intrusives are similar in mode of emplacement, composition, and probably genesis to rapakivi intrusives of Finland, the Younger Granites of Nigeria, Cape Ann Granite and Beverly Syenite, Mass., and syenite of Kungnat, Greenland, among others — allowing for different levels of erosion. A suite that includes gabbro or basalt, anorthosite, quartz syenite, fayalite granite, riebeckite granite, and biotite and/or hornblende granites is of worldwide occurrence. A model is proposed in which mantle-derived, convecting alkali olivine basaltic magma first reacts with K 2 O-poor lower crust of granulite facies to produce magma of quartz syenitic composition. The syenitic liquid in turn reacts with granodioritic to granitic intermediate crust of amphibolite facies to produce the predominant fayalite-free biotite and biotite-hornblende granites of the batholith. This reaction of magma and roof involves both partial melting and the reconstitution and precipitation of refractory phases, as Bowen proposed. Intermediate liquids include MgO-depleted and Na 2 O-enriched gabbro, which precipitated anorthosite, and alkali diorite. The heat source is the basaltic magma; the heat required for partial melting of the roof is supplied largely by heats of crystallization of phases that settle out of the liquid — mostly olivine, clinopyroxene and plagioclase.

Colorado↗
USGS1957

Preliminary geologic map of the Pumpkin Buttes area, Campbell and Johnson Counties, Wyoming, showing location of uranium occurrences

The Pumpkin Buttes area comprises about 450 square miles in Campbell and Johnson Counties that includes several prominent buttes known as Pumpkin Buttes. The area is near the center of the Powder River Basin, a large physiographic unit of prairie and sculptured terrain that occupies approximately 12, 000 square miles of northeastern Wyoming. The basin is bounded on the east by the Black hills, on the south by the Laramie Mountains, and on the west by the Big Horn Mountains. The northern end is more or less open into Montana. Much of the basin ranges in altitude from 4,000 to 5,000 feet above sea level; but in the central part, about 40 miles southwest of Gillette, the Pumpkin Buttes rise abruptly to an altitude of 6,000 feet. Secondary uranium minerals were discovered in the vicinity of Pumpkin Buttes in October 1951 (Love, 1952). The following spring, a study of the area and the uranium occurrences was begun by the Geological Survey on behalf of the Division of Raw Materials of the U. S. Atomic Energy Commission. The accompanying map, which shows distinguishable lithologic units and occurrences of uranium in outcrop, is a result of the continuation of this study.

Wyoming↗
USGS1952

Geologic map of bastnaesite deposits, Birthday claims, San Bernardino County, California

In April 1949 a deposit containing considerable quantities of the rare mineral bastnaesite - the fluorocarbonate of cerium, lanthanum, and other rare earths - was discovered near Mountain Pass, San Bernardino County, Calif. Small quantities of bastnaesite have been found in several places in the United States, but this area is the first that offers promise of being a commercial source of cerium, lanthanum, and other rare earths.

California↗