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At least 613 records · Page 34Linked to original sources
USGS1946

Structural control of ore bodies in the Jefferson City area, Tennessee

The zinc deposits of the Jefferson City area are confined to the lower half of the Kingsport formation of the Knox group of rocks. They are on the southeast flank of a northeast-trending anticline which is partially overridden from the southeast by the Bays Mt. thrust sheet. The beds show low dips. The area is transected by a series of high angle strike-slip faults having relatively small displacement and striking essentially parallel to the dominant northeast structure. Minor cross folds running transversely to the regional structure are numerous. Three sets of fractures trending N. 45-50 degrees W., N. 30-40 degrees E., and N. 60-70 degrees E. are well developed. The ore bodies are irregular but generally have a distinct elongation. The vertical extent may be limited to a single bed or may include several beds, depending upon local structural conditions. All ore bodies are confined to zones of pre-mineral deformation. The linear trends of the ore bodies show a remarkable parallelism to the axes of the cross folds. Ore occurs on any part of the flexures but maximum concentration is on the anticlinal crests and synclinal troughs: the ore attains greatest thickness on the anticlines. Fractures associated with the folding exhibit local ore control. Faults are poor sites for ore, but fracturing and drag folding accompanying faulting produce conditions favorable to ore deposition.

Tennessee↗
USGS1946

Artificial recharge of productive ground-water aquifers in New Jersey

Artificial recharge by water spreading is practiced in several places in New Jersey. Rates of recharge ranging from 3,000 to 125,000 gallons per acre per day have been measured at the Perth Amboy Water Works, where artificial recharge of the Old Bridge sand, of upper Cretaceous age, has been practiced for more than 40 years. At the Duhernal development, which also draws from the Old Bridge sand, four or five million gallons daily is now derived from artificial recharge. This rate will probably increase with further lowering of the water table near the lake. For many years the Princeton Water Company has pumped water from a stream for recharging the Stockton sandstone, of Triassic age. The Lake Mohawk-Sparta Water Company spreads water underground by means of covered, gravel-filled ditches to recharge a shallow aquifer in its well field. The City of East Orange spreads the water from several small streams over parts of the intake area of the Quaternary beds supplying its wells. The estimated total recharge there is about two million gallons daily. Closely related to artificial recharge are those instances wherein well sites are chosen to take advantage of potential recharge from existing bodies of surface water. At the Borough of Manville no water spreading operations are conducted, but about three quarters of the water from its wells is derived by recharge from the Raritan River. The silting of water spreading areas may impair their effectiveness considerably. In some instances the growth of aquatic vegetation seems to reduce the ill effects of silting.

New Jersey↗
USGS1946

Hydrothermal alteration in the Castle Dome copper deposit, Arizona

Hydrothermal alteration of the quartz monzonite host rock in the Castle Dome copper deposit consists of three phases. Very weak propylitic alteration of biotite and plagioclase occurs in the marginal part of the mineralized area. Where mineralization is stronger most of the plagioclase and some of the orthoclase and biotite are replaced by a montmorillonitetype clay, resembling beidellite, and hydrous mica. The third phase is localized along quartz-pyrite veins where the wall rock, commonly as much as an inch from the vein, is replaced by quartz and seriate. In contrast to the localization of quartz-sericite alteration along the veins, clay alteration is general and can be seen between the veins wherever the rock is not completely sericitized. Thus these two types of alteration cannot be separated areally. The most intense clay alteration together with moderate quartz-sericite alteration occurs in the ore body, whereas the strongest quartz-sericite alteration, where pyrite veins are largest and most numerous, is in a zone along the north side of the ore body.

Arizona↗
USGS1947

Scheelite in the Boulder District, Colorado

Scheelite accompanies ferberite as an ore of tungsten at many localities in the Boulder tungsten district. It is only of accessory importance in most veins, but in a few mines it affects grade of the ore substantially. It occurs in small veins, in vugs, disseminated in sericitized rock, and in gouge and minute fractures in shear zones. The vein and shear-zone deposits are the most important economically, but all scheelite-bearing ores owe their value chiefly to ferberite. The ratio of scheelite to ferberite is as high as 1:1 in some deposits containing one per cent WO 3 , but in scheelite-bearing ore containing 3 to 5 per cent WO 3 , the ratio ranges from 1:5 to 1:10. Scheelite is later than all minerals except calcite and some late dolomite. The mineralogy and paragenesis of the tungsten veins indicate a change from acid to alkaline solutions during mineralization. This change may be attributed partly to reaction with the alkaline wall rocks, but the distribution of alteration zones is in some respects incompatible with this hypothesis, and it is suggested in this paper that the solutions depositing tungsten changed at the source as well as by reaction. Ferberite was deposited from slightly acid, and scheelite from alkaline solutions. Early acid solutions leached lime from plagioclase in the wall rocks. Late alkaline solutions deposited a little lime as carbonate but carried little or no tungsten. As neither the solutions nor the altered walls could furnish much lime at the time when tungsten appears to have been most abundant in early alkaline solutions, scheelite formed only in relatively minor quantities.

Colorado↗
USGS1947

The sangdong tungsten deposit, southern Korea

The Sangdong deposit consists of metamorphosed lenticular beds in a sequence of gently dipping argillaceous sedimentary rocks. It is believed that scheelite mineralization was simultaneous with metamorphism, followed by deposition of wolframite during a later hydrothermal phase. The reserve of ore is estimated to be 3,000,000 tons, containing 51,000 tons of WO (sub 3.)

southern Korea↗
USGS1948

Some solutional features of the limestone near Lexington, Kentucky

Field work on the Ordovician limestones and shales of the Lexington area, Kentucky, has shown that no appreciable quantity of ground water is transmitted through interstitial openings in these rocks. Ground-water movement is restricted to joint planes and, to a lesser extent, bedding planes that have been enlarged by solution. Studies of these planes indicate that solution has been effective only to a limited depth below the land surface. The bottom of the solutional zone is an exaggerated replica of the land surface, showing a greater depth of the solutional zone below stream valleys. The greater depth is attributed to the greater accumulation of ground water, the dissolving agent, in those areas. Modifications of the ideal condition are effected by the less soluble beds and the configuration of the land surface. The underground drainage systems of the area develop in a manner similar to rectilinear stream patterns, showing a definite alignment along the two joint sets of the area. Directional solution has taken place where one of these joint sets has been developed to the exclusion of the other.

Kentucky↗
USGS1948

Variable coalification; the processes involved in coal formation

Coalification involves the genetic and metamorphic history of coal beds. The plant materials that form coal may be, in part, simply incorporated, or they may be present in vitrinized or fusinized form. Materials contributing to coal differ in their response to diagenetic and metamorphic agencies and the three essential processes of coalification are called incorporation, vitrinization, and fusinization. The processes are defined on the basis of important petrographic characteristics. A diagram is given illustrating the extent of change in the plant material, in comparison with diagenetic and metamorphic intensity. Since coal beds generally include various proportions of the diverse materials resulting from the three processes, practical classification of coal is intimately related to the part each process has played.

Economic Geology↗
USGS1948

Heavy metals in altered rock over blind ore bodies, East Tintic District, Utah

Standard chemical tests and spectroscopic analyses of altered Tertiary lavas that occur above blind ore bodies in the East Tintic district, Utah, have failed to show any evidence of the mineralization in the underlying dolomites. A new technique involving dithizone was used in the field to test ammonium acetate extracts of crushed samples of the lava for soluble heavy metals, with significant results. Concentrations of heavy metals, believed to be chiefly zinc, with some lead and rarely copper (?), were found in pyritized rhyolite above and up-rake from known blind ore bodies, and were lacking in similarly altered rhyolite underlain by barren rocks. An incompletely prospected area of pyritic alteration shows a definite pattern of positive tests and seems worthy of further exploration. The theory and practice of the dithizone method as used in the field is described briefly.

Utah↗
USGS1948

The bedding-replacement fluorspar deposits of Spar Valley, Eagle Mountains, Hudspeth County, Texas

The Spar Valley fluorspar district in the Eagle Mountains, Hudspeth County, Texas, is one of the few in the western United States containing bedding-replacement fluorspar deposits. The deposits at Spar Valley resemble the bedding-replacement deposits of the Cave in Rock fluorspar district of southern Illinois. Two distinct deposits, the North and the South ore bodies, are present. The North ore body is larger and has been developed by diamond drilling and mining; the following statements apply chiefly to it.The fluorspar partly replaces a sequence of three sandy limestones interbedded with four calcareous shales in the lower part of the Edwards limestone of Lower Cretaceous age. The fluoritized beds, which dip 40 degrees SW in conformity with underlying limestone, are overlain by thick impermeable gouge along a bedding-plane fault dipping slightly more than 40 degrees SW. The high-grade beds were derived from the sandy limestones, and the low-grade beds, which contain as much as 28 percent of CaF 2 , were formed from the calcareous shales. The selectiveness of replacement by the fluorine-bearing solutions, due to differences in the chemical composition, texture, and degree of brecciation of the original rock, resulted in bedding-replacement deposits of variable fluorite content.A reduction in volume, which accompanied the replacement, led to the development of many cavities. During the later stages of fluoritization these cavities were lined with fluorite crystals, early fluorite grains were coated and interstices between them were filled, and fluorite veins were formed in the ore beds and the underlying dense limestone.

Texas↗
USGS1948

Distribution of coastal black-sands in North Carolina, South Carolina, and Georgia, as mapped from an airplane

Black-sand beach concentrates are more widely distributed along the beaches of North Carolina, South Carolina, and Georgia than has been recorded heretofore, as shown by a map prepared by airplane reconnaissance. The map shows also that the black sands diminish in abundance northward, that their distribution is in part related to the configuration of the shoreline, and that they are found only on beaches along the open sea.

Georgia, North Carolina, South Carolina↗
USGS1948

A sensitive field test for heavy metals in water

A semiquantitative colorimetric analytical method using dithizone to detect traces of heavy metals in natural water is described. Although reagents of exceptional purity are required, only simple equipment is needed and the test can be made in a few minutes in the field. A combined mixed color and mono color technique makes the test suitable for a wide range of concentrations. The test is very sensitive; as little as 0.01 part per million of either copper, lead, zinc or any combination of the three metals can be detected readily.The dithizone test permits rapid field identification of drainage elements which contain significant concentrations of heavy metals. An example is given showing how the test can be used to trace the heavy metal content of a drainage system back to its source. It is possible that, under favorable conditions, the field test may facilitate prospecting by detecting metals discharged by the weathering of hidden ore bodies. However, until the method receives further investigation, it would be premature to predict its value.

Colorado↗
USGS1949

Cannel, boghead, torbanite, oil shale

The gradational interrelationship of coal with cannel, boghead, torbanite, and oil shale is reemphasized in view of contrary opinions expressed recently. An example from South Africa that has recently been studied in some detail is cited in illustration of how closely coal and torbanite may be related. The scientific classification of the carbonaceous rocks requires a broader basis of comparison than is generally adopted; authoritative statements cannot have very much weight unless supported by more correlated data than exist now.

Economic Geology↗
USGS1949

Sheet structure, a major factor in the occurrence of ground water in the granites of Georgia

Increasing demand for supplies of ground water in the Piedmont of Georgia has necessarily focused attention on granitic rocks, which have a considerable areal extent in this part of the state. These rocks have the property generally known as sheet structure. Major parting planes resulting from sheeting are usually sub-parallel to the rock surface on hills and in valleys and consequently control the circulation of subsurface water. Imperfect shallow pseudosynclinal basins formed by sheet planes in valleys are the receptacles for much subsurface water that percolates along these planes from nearby upland slopes. Therefore, wells drilled in lowlands in sheeted terranes almost invariably produce greater quantities of water than those on the uplands.

Georgia↗
USGS1949

Vestigial zinc in surface residuum associated with primary zinc ore in East Tennessee

A series of samples of residual clay at the Friends Station zinc deposit, Tenn., was collected and analyzed for zinc. Results indicate that residuum containing 0.05 percent Zn and more is the product of weathering of limestone and dolomite containing zinc mineralization. Chemical analysis of residual clays for zinc shows promise as a method of prospecting for zinc in the limestone valleys of the southern Appalachians.

Tennessee↗
USGS1949

Field method for the determination of zinc in soils

A method is described for the field estimation of total zinc in soils. A small sample of soil is fused with potassium bisulfate, the fused mass dissolved in water, buffered at pH 4 to 5.5 with acetate buffer, and sodium thiosulfate added to form complex ions with metals that might cause interference. Measured increments of the sample solution are added to a carbon-tetrachloride-dithizone solution, with vigorous shaking after each addition, until a standard color is obtained in the organic phase. Under favorable conditions up to 60 determinations per day can be made by one man. Comparisons of data obtained by the field method with accurate laboratory analyses of the same samples indicate that the method is sufficiently reliable for reconnaissance surveys.

Economic Geology↗