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Detailed studies of sphalerite, as a part of a larger study of the Central City district, Colorado, have been undertaken to learn something of the physico-chemical environment of ore deposition. More than 90 samples have been analyzed by chemical and spectrochemical methods and these data are interpreted in the light...

The Ambrosia Lake district in northwestern New Mexico is the most important uranium mining and milling district in the United States. Together with the nearby Laguna district it contains more than 50 percent of the nation's reserves.Most of the ore occurs in the Morrison formation of Late Jurassic age as elongate, tabular, mantolike...

Their stratigraphic setting demonstrates that three batholithic intrusions in northern and central Chile are respectively pre-Jurassic, Jurassic, and Cretaceous. Radiometric age determinations, by the lead-alpha (Larsen) method, indicate ages of 265 ± 30, 120 ± 15 to 125 ± 15, and 95 ± 10 to 130 ± 15 million years respectively for samples from the...

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This report establishes lithologic units among the granitic rocks of the east-central Sierra Nevada near Bishop, California. In this area the Sierra Nevada batholith is composed chiefly of quartz-bearing plutonic rocks ranging in composition from quartz diorite to alaskite but includes scattered small masses of darker and older plutonic rocks and remnants of metamorphosed...

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Analysis of data for the White and Wabash Rivers suggests means of determining discharge at the natural bankfull stage, despite the effects of artificial embanking and clearance of channels. Bankfull discharge, and discharge at mean annual flood, undergo an orderly downstream increase in percentage duration of flow....

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Recently discovered beryllium deposits in the Thomas Range, Utah, are along the periphery of the fluorspar district at Spor Mountain. The beryllium is in altered rhyolite tuff of Tertiary age and is associated with genetically related fluorite, quartz, chalcedony, opal, calcite, and mont-morillonite and with residual quartz, feldspar, and biotite. Nodules of silica...

Analytical methods used in geochemical prospecting for copper were compared by analysis of samples of residual soil collected in duplicate near a copper-bearing vein at the Malachite mine, Jefferson County, Colo. In this area barren or "background" samples have a mean copper content of 58 ppm (parts per million) and anomalous samples containing copper derived from the...

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A radiocarbon age of 10,500±250 years B.P. (Before Present) from shell material near the base of a terrace along the North Loup River, Howard County, Nebraska, dates the alluvial sequence of silts and soils as late Wisconsin. The alluvium containing the shell material previously was reported as...

The sex classes and age classes of various species of ducks constitute measurable elements of the populations. The present study deals primarily with sex ratios and age ratios and the ways in which they relate to population productivity. The present study is an evaluation of sex and age ratios in...

Tritium in Arabian rainfall has followed the trend observed in North America with peaks in 1958 and the spring of 1959. These measurements will be useful for future hydrologie studies. Water from wadi gravels averages 10 yr old. Carbon-14 measurements of deep waters indicate ages of several thousand years....

In northeastern Lyon County the areal distribution of aquifers of Cretaceous age determined from well-bottom altitudes suggests a series of interbedded sandstones striking northwestward and overlapping one another to the northeast. Probably the numerous thin sandstone aquifers in the area were deposited near the flanks of a Precambrian granite “high”...

The Elk Ridge area of southeastern Utah contains uranium ore deposits in two lower members of the Chinle formation of Late Triassic age. Each member is mineralized in different parts of the area, and where both are present only the lower contains ore. Across the Elk Ridge area from southwest to northeast, successively younger beds...

Petrographic and chemicoal studies of a suite of rocks from the Uwekahuna laccolith of Kilauea Volcano show that the original mafic tholeiitic magma differentiated into tholeiitic picrite, tholeiitic olivine gabbro, and an aphanitic rock approaching quartz-basalt in composition. Mechanisms involved were an initial gravity settling of olivine and a final filter pressing of...

Tectonic inclusions within the New Idria serpentine body contain jadeite in two distinct assemblages: (1) Lenslike inclusions containing a monomineralic green jadeite core surrounded by a calc-silicate rim. (2) Jadeite veins cross-cutting albite-crossite schist inclusions. In these veins jadeite coexists with low albite; green jadeite (Jd 75 Ac+Di+He 25)...

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Deposits of copper, vanadium, and uranium in nonmarine sandstones are numerous and widespread. Copper deposits, with or without uranium, are mainly resident in first-generation arkosic sandstones derived from granitic rock terrains; deposits rich in vanadium, with or without much uranium, are dominantly in second-generation sandstones derived from sedimentary rocks; and the uranium deposits with little...

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Open fissures, from 100 to several hundred feet apart, that have produced polygonal patterns on the Black Rock Desert, Nevada, are believed to be giant desiccation cracks resulting from a secular trend toward aridity in the last few decades. Similar features on the Smoke Creek Desert probably have the same...

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