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At least 631 records · Page 35Linked to original sources
USGS1949

Research in coal paleobotany since 1943

The varied applications of paleobotany to coal resource studies, coal technology, and to fundamental physical and chemical research on coal are briefly indicated. The usual conception of paleobotany is not as broad as this, and many of the studies of fossil plants have been conducted without reference to the part the plant materials assume in composing coal. The interrelationship of paleobotany with the physical constitution and petrography of coal is an intimate one. which is too involved for treatment in the present paper. Chief emphasis is devoted to review of plant microfossil investigations during the past several years.The consistent abundance of plant microfossils in coal and its associated rocks is now generally recognized. One of the greatest difficulties in using this material for correlation and for extending our knowledge of the plant composition of coal has been in systematic (taxonomic) treatment of the materials. The reviews of recent literature are presented chiefly with reference to the diverse systematic approaches of various authors. The contrast between essentially nonbotanical or morphologic classification schemes, which are simpler to apply and which may serve adequately for local correlational studies, and those studies conceived on a more fundamental basis of plant taxonomy, for paleogeographic and ecologic interpretation of botanically related groups, is presented. Both viewpoints should be kept clearly in mind, since differing circumstances of study and differing objectives may suggest the advisability of using one rather than the other method of systematic treatment of these fossils. No other fossils are so conveniently available from the coal deposits of primary interest.

Economic Geology↗
USGS1949

Origin of the Bendigo saddle reefs with comments on the formation of ribbon quartz

"Several textural varieties of quartz, together with ore textures and structural relations, indicate that (1) open-space filling, (2) replacement, and (3) growth by accretion were active processes in the formation of saddle reefs and related quartz bodies of the Bendigo goldfield, Australia. The relative importance of each process varied with the type of quartz body. . . . Book structure, ribbon structure, and 'crinkly banding' probably resulted primarily from the replacement of previously sheared or foliated zones in wall rock; the individual leaves and ribbons are usually residues from the replacement process."

Economic Geology↗
USGS1949

Buried preglacial ground water channels in the Albany-Schenectady area in New York

A map is presented showing contours of the buried preglacial channel of the Mohawk River from Schenectady, New York, to its confluence with the Hudson River about 12 miles south of Albany and of associated buried preglacial channels. The Pleistocene history of a portion of the Mohawk and Hudson Rivers is discussed, and the relation of buried valleys to ground-water supplies is indicated.

New York↗
USGS1950

Uranium-bearing sandstone deposits of the Colorado Plateau

The uranium-bearing sandstone deposits of the Colorado Plateau are commonly referred to as "carnotite deposits." They have been the principal domestic source of uranium, radium, and vanadium. The deposits are largely restricted to a few stratigraphic zones, along which they have a wide but spotty areal distribution. The ore minerals mainly impregnate sandstone, though in places fossil plants are richly mineralized. Most of the ore bodies are small, but have a wide range in size, and within individual deposits the ore has a considerable range in thickness and grade. The deposits are irregularly tabular or lenticular, with their long axes nearly parallel to the bedding, but the ore does not follow the beds in detail.The ore is thought to have been precipitated from ground-water solutions after the enclosing sands had accumulated and before regional deformation. Sedimentary structures that seem to have controlled the movement of these solutions and the features that probably localized the ore deposits are described, and their application as guides to ore finding is explained.

Colorado, Utah, Wyoming↗
USGS1950

Ground-water problems in the Philadelphia area [Pennsylvania]

Large quantities of ground water are used by the Philadelphia Naval Base and many industries in south Philadelphia, as well as by municipalities near Philadelphia in both Pennsylvania and New Jersey. The areal contact between unconsolidated sand, gravel, and clay strata of the Atlantic Coastal Plain and consolidated rocks of the Piedmont province extends in a northeast-southwest line through central Philadelphia. This line of contact, the so-called Fall Line, sharply separates the area of highly productive sand and gravel aquifers of the Coastal Plain from the less productive bedrock aquifers of the Piedmont Plateau. The daily withdrawal of ground water from sand and gravel in the Philadelphia area, including Bristol, Pa., and Trenton, N. J., is approximately 110 million gallons. Wells around Philadelphia yield an additional 13 million gallons a day from consolidated rocks of the Piedmont province. The Raritan formation of Cretaceous age is the principal aquifer for wells in south Philadelphia and the adjacent Camden area. The large quantity of water pumped and the limited extent of this aquifer in the area provide a potentially serious interstate water problem. Ground-water levels in the strategically important Naval Base area have not declined seriously as yet, but increasing withdrawal planned in adjacent New Jersey is expected to lower water levels in south Philadelphia The Delaware and Schuylkill Rivers are believed to be the chief sources of recharge to the Raritan formation, even though heavy pumping on either side of the Delaware River may be expected to affect water levels on the other side. Recharge appears to be adequate generally for present rates of withdrawal, but further studies are needed for an evaluation of the safe maximum yield of the area. The chemical quality of ground water pumped from the Raritan formation is satisfactory for most purposes, but periodic analyses indicate that the concentration of dissolved solids is increasing. This deterioration of the chemical quality probably is due to the character of the water and bottom sediments of the Delaware and Schuylkill Rivers. Shallow aquifers in south Philadelphia contain large amounts of gases generated by the decay of river silts and city refuse occupying low areas. The States of Pennsylvania and New Jersey, together with the municipalities concerned, are coordinating their efforts for a practical solution to the ground-water problems of the Philadelphia area.

Pennsylvania↗
USGS1950

Summary of Kinoshita's kuroko deposits of Japan

Summarized translation of a report by Kameki Kinoshita, published in Japanese in 1943, on kuroko deposits (black ore deposits) of Japan. "Kuroko means two things. One is the common mixture of sphalerite, galena, and barite which is ordinarily black to grayish white, depending on the proportion of barite. The other meaning is the unusual assemblage of separate bodies of: 1, sphalerite-galena-barite; 2, massive pyrite; 3, disseminated chalcopyrite in silicified rock; and 4, massive gypsum. Rarely are all four of these ore bodies present in any one mine, yet the assemblage is still called kuroko, regardless of color."

Hokkaido, Honshu↗
USGS1950

Value of domestic production of minerals from various classes of rocks

Fluids and sedimentary rocks accounted for 48 and 36 percent, respectively, of the total value of the 1946 domestic mineral production. The epigenetic (vein and replacement) and metamorphic deposits each contributed 6 percent of the total, and residual and igneous deposits accounted for 3 and 1 percent, respectively. Fuels were the most valuable of all the minerals produced--77 percent of the total. Petroleum, natural gas, and similar fluid fuels accounted for 47 percent of the total production and 98 percent of that from fluids; bituminous coal made up 24 percent of the total production and 67 percent of that from sedimentary rocks; anthracite coal was valued at 6 percent of the total production and 92 percent of that from metamorphic rocks. Exclusive of fuels, the bulk of the production of nonmetallics, and of the total mineral production too, was from sedimentary rocks (74 and 50 percent, respectively) and from veins and replacements (8 and 28 percent, respectively). Most of the production of metals, however, was from veins, etc. (62 percent) and residuum (29 percent).

Economic Geology↗
USGS1950

Dispersion of copper from the San Manuel copper deposit, Pinal County, Arizona

At San Manuel, near Tucson, Arizona, recent churn drilling has blocked out large reserves of low-grade "porphyry copper" ore. This virgin deposit has a small outcrop and seems ideally suited for a geochemical study of the dispersion pattern produced by weathering in a desert climate. Samples of soils, alluvium, ground water, and vegetation were analyzed for copper. To avoid grinding, to accentuate differences in copper concentration, and to decrease sampling error, sampling was confined to the silt and clay fraction of the soil and alluvium. A sensitive field test for copper, using hydrochloric acid for a digestant and dithizone for copper determination, proved both quick and reliable. The results of the study show that at present little copper from the ore body dissolves in the ground water or runoff, and also that very little is taken up by plants growing on the ore outcrop. For this reason, prospecting for similar deposits by the sampling and analysis of ground water or vegetation is unlikely to be fruitful. A study of plant ecology, however, shows that certain plant species grow preferentially on outcrops of copper ore and may be useful as indicators of ore. Chrysocolla along joints carries most of the copper in the oxidized zone. The chrysocolla is slowly disintegrated mechanically as the rock weathers and enters the fine fraction of the soil. Slope wash and soil creep carry the copper along with the other soil materials into the nearby washes, where they are incorporated in the alluvium and swept downstream during floods. Abrasion probably continues to concentrate the copper in the fines, but the net change downstream is a decrease in copper content caused by dilution. As copper can now be readily determined by chemical analysis in the field, analysis of soil and alluvium seems to be one of the best geochemical methods of prospecting for copper in a desert environment. Wherever appreciable copper is found in alluvium or soils, upstream or upslope sampling can be used to trace the copper back to its source.

Arizona↗
USGS1950

The appraisal of ore reserves at a Japanese copper mine

Estimates of ore reserves at major Japanese metal mines seem, at first glance, to be readily understandable to American engineers and geologists. Close scrutiny, however, generally reveals unexpected features at each mine. For example, the Hitachi copper mine formerly segregated its developed ore reserve into positive and probable on the basis of the possibility of high-grade and low-grade production from individual stopes. Tests were made by the writer at Hitachi on the accuracy of the original reserve estimates of a few ore blocks by comparing those figures with the final production data. The results suggesthat the average reserve estimate of positive ore may be accurate within 20 percent, plus or minus. A ten-year supply of proved ore at the big mines is not unusual; hence Hitachi is not much concerned with the additional categories of probable and possible ore, unless the positive ore has become inaccessible because of caving of the workings. For the sake of comprehensiveness, however, the writer studied the assay maps and stope maps in collaboration with the mine management and estimated tonnages of probable and possible ore, qualified by lower reliability ratings. Exploration prospects also were described in actual figures, subject to a variation of plus-or-minus 75 percent.

Ibaraki Prefecture↗
USGS1950

Alteration and metallization in the Bagdad porphyry copper deposit, Arizona

The porphyritic to seriate-textured quartz monzonite host-rock at Bagdad was changed by hypogene alteration to a granular rock in which the plagioclase became albitic, orthoclase and quartz increased in amount, and hornblende and book-biotite were recrystallized to pale brown leafy biotite. Hypogene sulfides, pyrite and chalcopyrite, were added during the process of alteration, accompanied in part by sericite. Molybdenite is younger than the chalcopyrite. Locally, the host rock was altered to a quartz-orthoclase-sericite facies containing more quartz and orthoclase than is found in the main alteration facies. Chemical analyses indicate that alteration and mineralization of the host rock resulted in loss of iron, lime, and soda, and addition of sulfur, copper, and potash.Supergene changes include the formation of a chalcocite blanket in late Pliocene or early Pleistocene time. Chalcocite replaced chalcopyrite in preference to pyrite. The chalcocite blanket is truncated by the present erosion surface and its distribution can be recognized from the character of the iron oxide left in the leached cavities. Along some of the fractures and faults, supergene clay is present, consisting of kaolinite and a member of the saponite-montmorillonite group.

Arizona↗
USGS1951

Notes on the manganese ores of Brazil

Brazil has been a small but consistent source of manganese ore for world markets during the last five decades. Production both for export and for domestic use is likely to increase. Deposits can be classified into syngenetic (the primary manganese sediments in iron formation at Urucum) and epigenetic. The epigenetic deposits can be further subdivided into four classes: (a) The Queluz or Morro da Mina type, in which the manganese oxide ore has been derived by weathering processes from a manganese silicate-carbonate-sulfide protore. (b) The Lagoa Grande type, enclosed in itabirite, in which lean man-ganiferous horizons in the metamorphosed iron formation have been leached and the manganese concentrated by weathering processes. (c) Deposits in slightly manganiferous rocks of various types in which the manganese has been concentrated by weathering processes. (d) Deposits in barren rocks into which manganese oxides have been introduced from unknown sources. It is probable that the Lagoa Grande type is closely related in ultimate origin to the Urucum type, although the regional metamorphism suffered by the former obscures relations. The Urucum deposits and two deposits of the Morro da Mina type have large reserves of export-grade ore. Many deposits of the Lagoa Grande type are known and the aggregate reserves are large, although their grade makes them more suitable for domestic than for export use. Deposits of the other two types are numerous but small, and their grade seems to consign most ore from these deposits to the domestic market. © 1951 Society of Economic Geologists, Inc.

Economic Geology↗
USGS1951

Ilmenite, magnetite, hematite, and copper in lavas of the Keweenawan series

The opaque minerals in ten lava flows of the Keweenawan series of Michigan were studied microscopically by the writer. The basaltic lavas , which range in thickness from 100 to 1,400 feet, contain ilmenite , magnetite , hematite , intergrowths of magnetite - ilmenite and ilmenite - hematite , copper sulfides, native copper , and pyrite. Variations of opaque iron minerals with thickness of flow are slight, but native copper predominates in the thinner flows and copper sulfides in the thickest. Pyrite occurs only in the thickest flow. Two groups of opaque minerals and their alteration products are distinguished. The earlier group includes magnetite , ilmenite , magnetite - ilmenite and ilmenite - hematite intergrowths, copper sulfides, and native copper . The later group includes hematite , native copper , chalcocite, pyrite, chlorite, and sphene. The second-generation minerals formed by the action of volatiles escaping from the lavas . The ratio of Ti to total Fe correlates with the degree of differentiation of the lavas , but the ratio of ferric to ferrous iron does not. The latter ratio was controlled primarily by the action of escaping volatiles.

Economic Geology↗
USGS1951

Ground water in alluvial deposits in Oklahoma

Alluvium along main streams in Oklahoma has long been recognized as a generally dependable aquifer. Pumping tests made in recent years afford a means of comparing one area with another. They indicate coefficients of transmissibility on the order of 70,000 gallons per day per foot in the Arkansas River alluvium near Fort Gibson, and 60,000 in the North Canadian River alluvium near Oklahoma City and El Reno.

Oklahoma↗
USGS1951

Geochemical techniques as applied in recent investigations in the Tintic District, Utah

Field techniques for the rapid extraction and estimation of copper, lead, and zinc from altered rock are described, together with their application in the Tintic district , Utah . Either sulfuric acid or an acetic acid-ammonium acetate reagent is feasible as an extractant; but of these two, sulfuric acid is preferred. Data obtained by partial extraction methods show that zinc and lead are concentrated in altered extrusive rocks 350 to 500 feet above a horizontal, pipelike ore body in limestone, where the extrusive rocks are cut by a fracture zone related to a strong premineral cross fault. Such concentrations are absent in altered but unbrecciated igneous rocks above the continuation of the same ore body in an unfaulted area.

Utah↗