Geology Reports⌕ Search

SEARCH · Geology Reports

Results for “Economic Geology”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 685 records · Page 38Linked to original sources
USGS1959

The Elk Ridge-White Canyon channel system, San Juan County, Utah: Its effect on uranium distribution

Reconnaissance in the White Canyon district, San Juan County, Utah, indicates that rocks of the Shinarump member of the Chinle formation of Triassic age were deposited in that district in two different channel systems; sediments deposited in channels of one system were derived from a source to the east and sediments of the other from a source to the south. The channel system containing sediments derived from the east, the Elk Ridge-White C anyon channel system, was apparently formed by a large braided stream that flowed westward from a source in granitic and metamorphic terrane of the ancestral Uncompahgre highland. All known uranium deposits of any consequence in the White Canyon district are confined to the Shinarump member deposited in the Elk Ridge-White Canyon channel system. The nature of the channels and the lithologic characteristics of the rocks filling this system of channels combine to form a much more favorable environment for the localization of uranium deposits than do the channels formed and the rocks deposited by northward-flowing streams. Recognition of channel systems in the White Canyon district suggests that channel systems may be recognized elsewhere in the Shinarump member, and that the Shinarump member on the Colorado Plateau may be composed of rocks deposited in many coalescing channel systems. In addition, study in the White Canyon district indicates that rocks deposited in some of these channel systems are more favorable hosts for uranium deposits than the rocks deposited in others. Recognition and delineation of these ancient channel systems may be-of help in making regional appraisals of ore potential and in the search for new mining districts.

Utah↗
USGS1959

Some aspects of the origin of the Ironwood iron-formation of Michigan and Wisconsin

The Ironwood iron-formation of the Gogebic Range of Michigan and Wisconsin is made up of several rock types, each of which is characterized by a different iron-rich mineral: hematite, magnetite, pyrite, iron carbonate, or iron silicate (minnesotaite, stilpnomelane). Where the Ironwood iron-formation is relatively unaltered the Plymouth, Norrie, and Anvil members consist of wavy-bedded magnetite and silicate-rich rocks, whereas the Yale and Pence members consist of even-bedded carbonate, silicate, magnetite, and pyrite-rich rocks. These rock types represent primary facies of the iron-formation that were deposited under differing physical and chemical conditions during a period of continuous iron-rich sedimentation. Animikie sedimentation in the Gogebic district began with the deposition of sandstone and dolomitic limestone in a shallow sea advancing over a low-lying land mass of lower Precambrian granite and green-stone. Continued advance of the sea, with effective separation of clastic material near shore, permitted the dominantly chemical sedimentation of the iron- formation in somewhat deeper water. The development of an off-shore basin with partially restricted circulation would have facilitated such deposition. Minor fluctuations in the physical and chemical conditions within the depositional environment are reflected in the differing facies of the iron-formation. Deposition of the iron and silica-rich chemical sediments was terminated by increased tectonism and the deposition of the thick sequence of slates and graywackes of the Tyler formation.

Michigan, Wisconsin↗
USGS1959

Some phase relations in the hydrothermally altered rocks of porphyry copper deposits

The application of ACF and AKF diagrams to the hydrothermal alteration in porphyry Cu deposits aids in the recognition of the critical components, and the characteristic mineral phases permit the distinction of one alteration facies from another. The somewhat meager chemical and mineralogical data suggest 3 principal alteration facies, herein called the propylitic, argillic, and potassium silicate facies. The ACF diagram applies to the propylitic alteration. The critical components are Al 2 O 3 , CaO, and (FeO + MgO + MnO), and the characteristic minerals are muscovite (sericite), epidote, chlorite, and a member of the carbonate group. The AKF diagram applies to the argillic and potassium silicate facies. The critical components are Al 2 O 3 , K 2 O, and (FeO + MgO + MnO). The characteristic minerals for the argillic facies are kaolinite (or other member of the group) and muscovite (sericite); and for the potassium silicate facies, muscovite (sericite), biotite, and K-Feldspar. For the propylitic facies, insufficient chemical analyses are available to show the chemical changes between the fresh and altered rock. For the argillic and potassium silicate facies, chemical analyses indicate a loss in Al, Fe, Mg, Ca, and Na; and a gain in K, hydroxyl ion (water), and S. The gain in K is about 60% greater for the potassium silicate facies than for the argillic.

Economic Geology↗
USGS1959

Primary borates in playa deposits: Minerals of high hydration

The primary borate minerals in nonmarine bedded borate deposits - those of the playa type, and their deformed derivatives - are the high hydrates. Both field and laboratory data indicate that the high hydrates are the borate minerals that form stable phases at the lowest temperatures: under the surface conditions of playas. From a study of hand specimens of borate minerals from the new Turkish borate deposits, Meixner suggested that the borate minerals having the lowest specific gravity, and hence, highest water content, are the primary minerals. The role of temperature in the formation of the hydrous borates is shown by solid phases in the system Na 2 B 4 O 7 -H 2 O. As temperature increases, hydration of the solid phase decreases successively from borax (10H 2 O) through tincalconite (5H 2 O), kernite (4H 2 O), to metakernite (2H 2 O). This suggests that in the temp- erature ranges considered in the present paper - those of playas - the high hydrate (borax) is the one most likely to form as the primary mineral in nature. Studies of the Ca, Mg, and Ca-Na hydrous borate systems suggest that the same statement holds in these systems. Until recently, only borax and ulexite (Na 2 O . 2CaO . 5B 2 O 3 . 16H 2 O) have been known as primary minerals of playa deposits. However, inderite (2MgO . 3B 2 O 3 . 15H 2 O) has recently been found as a primary mineral I 5i in Argentina and primary inyoite (2CaO . 3B 2 O 3 . 13H 2 O) has been found in Peru. These 4 minerals are the high hydrates of their respective mineral series. None of the lower hydrates are known as primary minerals in nonmarine bedded deposits. On burial and deformation of the primary minerals, the changes in temperatures and pressures are almost certainly in such a direction as to encourage minerals of higher density and lower hydration to become stable phases. Field evidence bears this out; in all deformed deposits secondary minerals of low hydration are quantitatively important.

Economic Geology↗
USGS1959

Plastic standards for geochemical prospecting

Plastic standards for use in geochemical prospecting have been prepared by impregnating a clear thermosetting resin with different amounts of a stable dye or colored metal complex. The colored plastic is molded or subsequently milled into convenient shapes to form standards that are less bulky and more stable than the liquid standards conventionally used in rapid field methods. The use of such standards is limited only by the availability of stable coloring materials. The preparation of plastic standards for use with copper, zinc, tin, and mercury field procedures is described.

Economic Geology↗
USGS1959

Peneconcordant uranium deposit: A proposed term

The term peneconcordant is proposed to describe the form of the numerous and highly productive U deposits in sedimentary rocks of the Colorado Plateau, Wyoming, the Dakotas, and Texas. Peneconcordant U deposits are tabular, lenticular, or irregularly-shaped masses of widely differing size that are, in general, concordant to the gross sedimentary structures of the enclosing rock but that in detail cut across sedimentary structures. They differ from vein deposits in that they do not occupy or follow fractures or shear zones in the sedimentary rocks. Furthermore, they are not coextensive with a specific lithologic unit, such as U-bearing marine black shale. The many terms now used to describe these U deposits are based variously on petrographic, mineralogic, geographic, and genetic considerations; none is satisfactory for describing all these deposits having a common and distinctive form. Furthermore, some of the terms are ambiguous and have been commonly used to group together deposits having distinctly different forms. The term peneconcordant U deposit clearly sets apart a widespread and important type of U deposit that has a common and distinctive form, namely, nearly concordant to the bedding of the host rock. The meaning of the term is self-evident, and the term is readily applicable to field usage.

Economic Geology↗
USGS1959

Effect of FeS on the unit cell edge of sphalerite, a revision

Redeterminations of the relation between the composition and unit-cell size of Fe-bearing sphalerites, necessitated because of partial oxidation of the FeS sample used in earlier measurements, are presented. It is noted that the Fe-ZnS solvus curve may also require revision and should be used with caution, particularly for temperature determinations in the higher ranges.

Economic Geology↗
USGS1960

Detrital-appearing uraninite grains in the shinarump member of the chinle formation in northern Arizona

A sample of uranium-bearing conglomerate from the Shinarump member of the Chinle formation in northern Arizona was disaggregated in an ultrasonic separator. The sample, weighing 187 grams, contained about 60 grains of uraninite (from 0.1 to 1 mm diameter) which have the sphericity and polish suggestive of detrital grains . The detrital-appearing grains are associated with abundant interstitial uraninite , sphalerite, and pyrite, which presents conflicting evidence as to the origin of the uranium deposit. No definite conclusions are presented for the occurrence of these grains . However, the evidence strongly suggests that they are probably not detrital in origin, but are uraninite replacements of detrital grains ; the original mineral may have been quartz.

Arizona↗
USGS1960

Occurrence of strontium in the surface and ground waters of Champaign county, Ohio

Naturally occurring strontium was found in both surface and ground waters during an investigation of the water resources of Champaign County , Ohio . The strontium is related to the presence of celestite ( strontium sulfate) in rocks associated with evaporite deposition. The principal source of celestite in Ohio is in rocks of Late Silurian age. Celestite is present also in the glacial deposits of western Ohio , which contain rock material of Late Silurian age. Total time in contact with the rock material seems to have a large effect upon concentrations of strontium in ground water . Streamflow, during low-flow periods, is made up largely of ground - water seepage and contains detectable strontium . Strontium has been found in ground water in other counties in western Ohio and in the brines of eastern Ohio .

Ohio↗
USGS1960

Extract ability of humic acid from coalified logs as a guide to temperatures in colorado plateau sediments

Coalified logs in Triassic and Jurassic sediments of the Colorado Plateau have been exposed to alkaline ground water. Extraction of humic acids under such conditions is temperature dependent. Study of residual humic acids in a suite of coalified logs has indicated that temperatures up to but not over 120° C prevailed in the sediments . This maximum temperature corresponds with that to be expected from geothermal gradient and estimated from mineralogic evidence.

Colorado↗
USGS1960

Scheelite in the precambrian gneisses of Colorado

Scheelite of Precambrian age has been found at several localities in Colorado and Wyoming in recent years. Most of it is disseminated in regionally metamorphosed rocks, principally in calc-silicate gneiss , but also in amphibolite. Small amounts are found in pegmatites and in gold-or copper-quartz veins of Precambrian age. The scheelite in most of the deposits contains molybdenum, and much of it is accompanied by discrete powellite (CaMoCX). The scheelite deposits vary in age with the rocks that contain them and show no consistent genetic associations. Many of the deposits are products of some phase of the major plutonic stage that included regional metamorphism, migmatization, and emplacement of syntectonic granites, A few deposits may be related to younger Precambrian granites, and some are related to late diorite and pegmatite. Tungsten originally present in minor concentration in the sedimentary rocks that gave rise to the gneisses was evidently redistributed and r eery stall ized through successive Precambrian plutonic episodes. Reworked Precambrian deposits may have been a source of the tungsten in the economically important Tertiary deposits, and possibly also of molybdenum. The Precambrian scheelite deposits found thus far have proved to be of minor economic importance, but others are still being found, and many more can be presumed to exist; among these may be some of importance.

Colorado↗
USGS1960

Metallization and post-mineral hypogene argillization, Lost River tin mine, Alaska

The Lost River tin and tungsten deposit occurs in a buried granite pluton and in associated rhyolite dikes that intrude Paleozoic limestone. The dikes and parts of the granite were greisenized and then argillized irregularly. Metallization accompanied greisenization rather than argilli-zation, although both processes probably were closely related in time. Iron-zinc ratios in sphalerite indicate that the ore minerals were deposited at a temperature between 425°C and 740°C. This temperature is within the range of the temperatures at which topaz, a comman associate of the ore minerals, has been synthesized in the laboratory. The temperature of deposition of the ore minerals is above the temperature interval in which clay minerals are stable. Thus, clay minerals could not have formed while ore was being deposited. As temperatures fell and entered the stability range of the clay minerals, argillic alteration encroached upon greisen ores and wall rocks. Reaction rims between quartz and topaz indicate that kaolinite could have formed according to the following reaction: topaz + quartz + water + limestone -* kaolinite + fluorite + Cajj"C (Al,F)2Si04 + Si02 +3H2O+ CaCOa - Al2Si20B(OH)41 + CaF2 + H2CO3 The clay minerals, which formed from diverse rock types, consist of kaolinite, dickite, mixed-layered chlorite-montmorillonite, and minor montmorillonite, accompanied by variable amounts of muscovite and zinnwaldite. The dickite is most common in and near late veins that cut the earlier-formed greisen. Temperature is believed to be the principal agent governing the relations between ore deposition and argillization . Similar relations are to be expected in other high-temperature deposits where abundant veining and fracturing indicate that wall rocks reached an isothermal condition above a maximum temperature of 480°C during ore deposition.

Bering land bridge↗
USGS1960

A rapid and accurate contour interpolator

An instrument called a "contourpolator" is described. The device is constructed from readily available materials costing about $2.00 and consists of 4 primary parts. Detailed instructions are provided for its assembly and use.

Economic Geology↗
USGS1960

Position of the salt-water body in the magothy(?) formation in the Cedarhurst-Woodmere area of southwestern Nassau county, Long Island, N.Y.

The position and chloride concentration of a sizable body of salt water , moving slowly landsyard from the south-shore bays of Long Island and the Atlantic Ocean were defined by recent test drilling in the Cedarhurst-Woodmere area of southwestern Nassau County, Long Island, N. Most of the salt-water body is in the lower part of a permeable artesian aquifer; the lowermost part of the salt-water body is in clay deposits underlying the permeable aquifer. The upper limit of the salt-water body in this area was found at depths increasing progressively in a landward direction. It was 318 feet below sea level at a well in Cedarhurst and 541 feet below sea level at a well in Woodmere. The lower limit of the salt-water body was determined at depths between 578 and 630 feet below sea level in the Cedarhurst-Woodmere area. The salt-water body is more than 300 feet thick at a well in Cedarhurst, and it thins out to zero in the vicinity of a pumping center about 1- miles northeast of the Cedarhurst well. Chloride concentration in the salt-water body in the Cedarhurst-Woodmere area ranged from about 40 to 16,000 ppm (parts per million). Isochlors define a zone of diffusion about a mile wide in the Cedarhurst-Woodmere area. They indicate a thickness of diffused water ranging from a few tens to more than 150 feet vertically. Electrical-log data show that the upper boundary of the salt-water body moved upward 21 feet between 1952 and 1958 at a site in Woodmere about half a mile southwest of the pumping center. ' From this information it is inferred that between 1952 and 1958 the leading edge of the saltwater front moved landward about 2,000 feet toward the pumping center.

New York↗