Geology topics
G.C. Curtin
Publications and source records attributed to G.C. Curtin.
Geochemical maps of selected elements and results of spectrographic analyses for heavy-mineral concentrates from the western half of the Talkeetna Mountains Quadrangle, Alaska
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The Alaskan Mineral Resource Assessment Program: Background information to accompany folio of geologic and mineral resource maps of the Tanacross quadrangle, Alaska
The Tanacross quadrangle, consisting of 17,400 km 2 (6,700 mi 2) in east-central Alaska, was investigated by an interdisciplinary research team for the purpose of assessing the mineral resource potential of the quadrangle. This report provides the background information for a folio of maps on the geology, geophysics, reconnaissance geochemistry, Landsat imagery, and mineral resource evaluation of the quadrangle. Revisions to the previously published geologic map of the Tanacross quadrangle, 18 new potassium-argon ages, and a comprehensive bibliography are also included.
Mineral resources map of the Tanacross Quadrangle, Alaska
Areas favorable for the occurrence of two types of mineral deposits are delineated on the map. Known deposits and occurrences are also shown on the map and available data on them are provided in table 1. Information from the known deposits combined with geologic, geochemical, geophysical, and earth satellite data presented in the other components of the Tanacross folio provide the basis for the selection of favorable areas. However because bedrock exposure is poor in the Tanacross quadrangle, types of deposits other than those now known to occur may eventually be found, and boundaries of the area delineated as favorable may change as more information, particularly from drilling, is obtained.
Geochemical maps showing the distribution and abundance of copper in the Tanacross Quadrangle, Alaska
This series of geochemical maps shows the distribution of copper in four sample media: (A) the oxide residue (the oxalic-acid-leachable fraction) of the stream sediment, (B) the minus-80-mesh stream sediment, (C) the ash of streambank sod (mixed organic and inorganic material) collected beneath the water level, and (D) the ash of aquatic bryophytes (mosses). The copper data are plotted on base maps showing generalized geology and the drainage pattern. The map symbols show the sample sites and ranges of values in the following manner: (1) open symbols denote background, (2) small black symbols represent weakly anomalous values, and (3) large black symbols denotes strongly anomalous values. Because the small black symbols represent weakly anomalous values, they are considered to be significant only where they are closely associated with strongly anomalous metal values either in the same sample medium or with anomalous values in other sample media. The ranges of values represented by the symbols are shown on the histograms which accompany the geochemical maps. An explanation of sampling, preparation, and analytical procedures is given in Circular 734, which accompanies this folio. Complete analytical data for geochemical samples collected by the U.S. Geological Survey in the Tanacross quadrangle are available in a U.S. Geological Survey open-file report (O'Leary and others, 1976).
Geochemical maps showing the distribution and abundance of molybdenum in the Tanacross Quadrangle, Alaska
This series of geochemical maps shows the distribution of molybdenum in four sample media: (A) the oxide residue (the oxalic-acid-leachable fraction) of the stream sediment, (B) the minus-80-mesh stream sediment, (C) the ash of streambank sod (mixed organic and inorganic material) collected beneath the water level, and (D) the ash of aquatic bryophytes (mosses). The molybdenum data are plotted on base maps showing generalized geology and the drainage pattern. The map symbols show the sample sites and ranges of values in the following manner: (1) open symbols denote background, (2) small black symbols represent weakly anomalous values, and (3) large black symbols denotes strongly anomalous values. Because the small black symbols represent weakly anomalous values, they are considered to be significant only where they are closely associated with strongly anomalous metal values either in the same sample medium or with anomalous values in other sample media. The ranges of values represented by the symbols are shown on the histograms which accompany the geochemical maps. An explanation of sampling, preparation, and analytical procedures is given in Circular 734, which accompanies this folio. Complete analytical data for geochemical samples collected by the U.S. Geological Survey in the Tanacross quadrangle are available in a U.S. Geological Survey open-file report (O'Leary and others, 1976).
Geochemical maps showing the distribution and abundance of lead in the Tanacross Quadrangle, Alaska
This series of geochemical maps shows the distribution of lead in four sample media: (A) the oxide residue (the oxalic-acid-leachable fraction) of the stream sediment, (B) the minus-80-mesh stream sediment, (C) the ash of streambank sod (mixed organic and inorganic material) collected beneath the water level, and (D) the ash of aquatic bryophytes (mosses). The geochemical data are plotted on base maps showing generalized geology and the drainage pattern. The map symbols show the sample sites and ranges of values in the following manner: (1) open symbols denote background, (2) small black symbols represent weakly anomalous values, and (3) large black symbols denotes strongly anomalous values. Because the small black symbols represent weakly anomalous values, they are considered to be significant only where they are closely associated with strongly anomalous metal values either in the same sample medium or with anomalous values in other sample media. The ranges of values represented by the symbols are shown on the histograms which accompany the geochemical maps. An explanation of sampling, preparation, and analytical procedures is given in Circular 734, which accompanies this folio. Complete analytical data for geochemical samples collected by the U.S. Geological Survey in the Tanacross quadrangle are available in a U.S. Geological Survey open-file report (O'Leary and others, 1976).
Geochemical maps showing the distribution and abundance of zinc in the Tanacross Quadrangle, Alaska
This series of geochemical maps shows the distribution of zinc in four sample media: (A) the oxide residue (oxalic-acid-leachable fraction) of the stream sediment, (B) the minus-80-mesh steam sediment, (C) the ash of streambank sod (mixed organic and inorganic material) collected beneath the water level, and (D) the ash of aquatic bryophytes (mosses). The map symbols show sample sites and ranges of values in the following manner: (1) open symbols denote background, (2) small black symbols represent weakly anomalous values, and (3) large black symbols denote strongly anomalous values. Because the small black symbols represent weakly anomalous values, we consider them to be significant only where they correlate with strongly anomalous metal values either in the same or in other sample media. The ranges of values represented by the symbols are shown on the histograms that accompany the geochemical maps. An explanation of sampling, preparation, and analytical procedures is given in Circular 734, which accompanies the folio. Complete analytical data for geochemical samples collected by the U.S. Geological Survey in the Tanacross quadrangle are available in a U.S. Geological Survey open-file report (O'Leary and others, 1976.)
Geochemical maps showing the distribution and abundance of arsenic and mercury in the Tanacross Quadrangle, Alaska
This series of geochemical maps shows the distribution of arsenic and mercury in the minus-80-mesh stream sediment and of arsenic in the ash of streambank sod (mixed organic and inorganic material) collected beneath the water level. The geochemical data are plotted on a base map that shows generalized geology and the drainage pattern. The map symbols show the sample sites and ranges of values in the following manner: (1) open symbols denote background, (2) small black symbols represent weakly anomalous values, and (3) large black symbols denotes strongly anomalous values. Because the small black symbols represent weakly anomalous values, they are considered to be significant only where they are closely associated with strongly anomalous metal values either in the same sample medium or with anomalous values in other sample media. The ranges of values represented by the symbols are shown on the histograms that accompany the geochemical maps. An explanation of sampling, preparation, and analytical procedures is given in Circular 734, which accompanies this folio. Complete analytical data for geochemical samples collected by the U.S. Geological Survey in the Tanacross quadrangle are available in a U.S. Geological Survey open-file report (O'Leary and others, 1976).
Geochemical maps showing the distribution and abundance of tin in the Tanacross Quadrangle, Alaska
This series of geochemical maps shows the distribution of tin in three sample media: (A) the oxide residue (the oxalic-acid-leachable fraction) of the stream sediment, (B) the minus-80-mesh stream sediment, and (C) the ash of aquatic bryophytes (mosses). The geochemical data are plotted on a base map that shows generalized geology and the drainage pattern. The map symbols show the sample sites and ranges of values in the following manner: (1) open symbols denote background, (2) small black symbols represent weakly anomalous values, and (3) large black symbols denotes strongly anomalous values. Because the small black symbols represent weakly anomalous values, they are considered to be significant only where they correlate with strongly anomalous metal values either in the same or other sample media. The ranges of values were determined from the histograms and other statistical data shown for each of the sample media. An explanation of sampling, preparation, and analytical procedures is given in Circular 734, which accompanies this folio. Complete analytical data for geochemical samples collected by the U.S. Geological Survey in the Tanacross quadrangle are available in a U.S. Geological Survey open-file report (O'Leary and others, 1976).
Geochemical maps showing the distribution and abundance of beryllium in the Tanacross Quadrangle, Alaska
This series of geochemical maps shows the distribution of beryllium in three sample media: (A) the oxide residue (the oxalic-acid-leachable fraction) of the stream sediment, (B) the minus-80-mesh stream sediment, and (C) the ash of aquatic bryophytes (mosses). The geochemical data are plotted on a base map that shows generalized geology and the drainage pattern. The map symbols show the sample sites and ranges of values in the following manner: (1) open symbols denote background, (2) small black symbols represent weakly anomalous values, and (3) large black symbols denotes strongly anomalous values. Because the small black symbols represent weakly anomalous values, they are considered to be significant only where they correlate with strongly anomalous metal values either in the same or in other sample media. The ranges of values represented by the map symbols are shown on the histograms that accompany the geochemical maps. An explanation of sampling, preparation, and analytical procedures is given in Circular 734, which accompanies this folio. Complete analytical data for geochemical samples collected by the U.S. Geological Survey in the Tanacross quadrangle are available in a U.S. Geological Survey open-file report (O'Leary and others, 1976).
Composite geochemical map of anomalous copper and molybdenum distribution in the Tanacross Quadrangle, Alaska
This geochemical map delineates drainage basins in which either anomalous copper, molybdenum, or both copper and molybdenum were detected in at least one of four sample media: (A) the oxide residue (the oxalic-acid-leachable fraction) of the stream sediment, (B) the minus-80-mesh stream sediment, (C) the ash of streambank sod (mixed organic and inorganic material) collected beneath the water level, and (D) the ash of aquatic bryophytes (mosses). The anomaly patterns were derived from the point-plot maps of copper and molybdenum distribution in the individual sample media (Curtain, Day, O'Leary, Marsh, and Tripp, 1976; Curtain, Day, Carten, Marsh, and Tripp, 1976). Background data were disregarded for each of the two metals. Weakly anomalous data for all media (small black symbols) were assigned the number 2; strongly anomalous data for all media (large black symbols) were assigned the number 3. These new data were then summed or "stacked" for each metal so that all sites showing anomalous values in one or more of the sample media had a numerical rating that ranged from 2 (weakly anomalous value in one sample medium) to a possible 12 (strongly anomalous values in all four sample media). The summed data were ranked into three groups shown in the explanation. The drainage basins showing anomalous values were outlined according to these groups. As a final step the composite copper anomaly map was superimposed on that of molybdenum to give this composite copper-molybdenum map.
Maps showing mineralogical and geochemical data for heavy-mineral concentrates in the Tanacross quadrangle, Alaska
This series of maps showing the following data for heavy mineral concentrates: distribution and abundance of selected ore-related minerals, distribution and abundance of copper in the magnetic fraction, and distribution and abundance of lead, copper, tin, beryllium, tungsten and bismuth in the nonmagnetic fraction. The data are plotted on base maps showing generalized geology, base metal prospects in the Yukon-Tanana Upland, and the drainage pattern. The distribution and abundance of ore-related minerals (fig. A) were obtained by microscopic examination of the heavy-mineral concentrates. The number of mineral grains observed is shown in the map explanation. Figures B through H are geochemical maps showing the distribution and abundance of metals as determined by six-step semi-quantitative emission spectrography. The geochemical map symbols show sample sites and the actual values for the element in the sample as determined by spectrography. An explanation of sampling, preparation, and analytical procedure is given in Circular 734 which accompanies this folio. Complete analytical data for geochemical samples collected by the U.S. Geological Survey in the Tanacross quadrangle are available in an open-file report (O'Leary and others, 1976).
Movement of elements into the atmosphere from coniferous trees in subalpine forests of Colorado and Idaho
Exudates from conifer trees, presumably consisting largely of volatile materials, were sampled at 19 subalpine localitites in Colorado and Idaho where anomalous amounts of several metals were determined in vegetation and mull during previous geochemical testing. The trees sampled were lodgepole pine ( Pinus contorta ), Engelmann spruce ( Picea engelmannii ) and Douglas fir ( Pseudotsuga menziesii ). The condensed exudates were passed through No. 40 Whatman filters, and through 5-micron, 0.45-micron, and 0.05-micron average-pore-diameter membrane filters, evaporated to dryness, and each residue was ashed and analyzed by a semiquantitative spectrographic method. The ashed residues of the exudates contain lithium, beryllium, boron, sodium, magnesium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, arsenic, strontium, yttrium, zirconium, molybdenum, silver, lead, bismuth, cadmium, tin, antimony, barium, and lanthanum. The presence of these elements suggests that volatile exudates from vegetation are a medium for the transport of elements in the biogeochemical cycle in subalpine environments. Thus, air sampling and analysis of aerosols derived from volatile exudates may be a useful tool in geochemical exploration.
The association of geochemical anomalies with a negative gravity anomaly in the Chief Mountain-Soda Creek area, Clear Creek County, Colorado
Geochemical studies in the Chief Mountain Soda Creek area, Clear Creek County, Colo., show that anomalously high amounts of Au, Ag, Pb, Zn, Cd, and Bi in mull ash, and Cu and Hg in soil, correspond to a negative gravity anomaly in the Front Range mineral belt. The correspondence of the geochemical anomalies to the negative gravity anomaly suggests the presence of altered and mineralized rock and a Tertiary intrusive body at depth. This gravity anomaly and other similar gravity anomalies in the Front Range mineral belt merit further investigation for possible ore deposits.