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P. K. Theobald

Publications and source records attributed to P. K. Theobald.

At least 19 recordsLinked to original sources
USGS1993

The Hatu gold anomaly, Xinjiang-Uygur Autonomous Region, China - testing the hypothesis of aeolian transport of gold

In 1987, a cooperative project between the U.S. Geological Survey and the Institute of Geophysical and Geochemical Exploration was initiated to evaluate the origin of the Hatu gold anomaly. The anomaly is located in the Hatu mining district in the northwest corner of Xinjiang-Uygur Autonomous Region in northwest China. The climate is semiarid to arid and wind erosion predominates. A regional soil survey of the Hatu district, based on samples collected on a 200 by 500 m grid and composited prior to chemical analysis to a density of one sample per square km, delineated a series of south-southeast-trending Au anomalies. Anomalous Au values range from 5 ppb to more than 700 ppb. The Hatu anomaly, the most prominent of these anomalies, is more than 30 km long and about 5 km wide. The mining town of Hatu and the economic gold deposits of Qiqu 1 and Qiqu 2 are at the northern end of this anomaly. The axis of the Hatu anomaly cuts across mapped structure and stratigraphy in the district, but is parallel to the prevailing wind direction. This observation led to the hypothesis that the Hatu anomaly is the result of acolian dispersion of gold from the vicinity of Qiqu 1 and Qiqu 2. The alternative interpretation, that the anomalies reflected additional primary gold occurrences, was not consistent with existing information on the known occurrences and the geology.

Journal of Geochemical Exploration↗
USGS1992

The Conterminous United States Mineral Assessment Program: Background information to accompany folio of geologic, geochemical, geophysical, and mineral resource maps of the Ajo and Lukeville 1° by 2° quadrangles, Arizona

Encompassing about 21,000 km 2 in southwestern Arizona, the Ajo and Lukeville 1° by 2° quadrangles have been the subject of mineral resource investigations utilizing field and laboratory studies in the disciplines of geology, geochemistry, geophysics, and Landsat imagery. The results of these studies are published as a folio of maps, figures, and tables, with accompanying discussions. Past mineral production has been limited to copper from the Ajo Mining District. In addition to copper, the quadrangles contain potentially significant resources of gold and silver; a few other commodities, including molybdenum and evaporites, may also exist in the area as appreciable resources. This circular provides background information on the mineral deposits and on the investigations and integrates the information presented in the folio. The bibliography cites references to the geology, geochemistry, geophysics, and mineral deposits of the two quadrangles.

Arizona↗
USGS1988

Maps showing anomalous concentrations of lead, molybdenum, bismuth, and tungsten in stream sediment and heavy-mineral concentrate from parts of the Ajo and Lukeville 1 degree by 2 degrees quadrangles, Arizona

These maps are part of a folio of maps of the Ajo and Lukeville 1° x 2° quadrangles, Arizona, prepared under the Conterminous United States Mineral Assessment Program. Other publications in this folio include U.S. Geological Survey Miscellaneous Field Studies Maps MF-1834-A, 1834–B, and 1834–C and U.S. Geological Survey Open-File Reports 82–419, 82–599, and 83–734. Open-File Reports 82–419 and 83–734 constitute the basic data and initial interpretation on which this discussion is predicated. Open-File Report 82–599 is an aeromagnetic map.

Arizona↗
USGS1988

Maps showing anomalous concentrations of zinc, silver, antimony, manganese, barium and strontium in stream sediment and heavy-mineral concentrate from parts of the Ajo and Lukeville 1 degree by 2 degrees quadrangles, Arizona

This map is part of a folio of maps of the Ajo and Lukeville 1 degree x 2 degrees quadrangles, Arizona, prepared under the Conterminous United States Mineral Assessment Program. Other publications in this folio include U.S. Geological Survey Open-File Reports 82-419 (Barton and others, 1982), 82-599 (Klein, 1982), and 830734 (Theobald and Barton, 1983), and Miscellaneous Field Studies Maps MF-1834-A (Peterson and Tosdal, 1986), MF-1834-B (Peterson and others, 1987), MF-1834-C (Theobald and Barton, 1987), and MF-1834-D (Theobald and Barton, 1988). Open-File Reports 82-419 and 83-734 constitute the basic data and initial interpretation on which this discussion is predicated. MF-1834-C and D show the distributions of anomalous concentrations of copper, lead, molybdenum, bismuth, and tungsten.

Arizona↗
USGS1987

Maps showing anomalous copper concentrations in stream sediments and heavy-mineral concentrates from the Ajo and Lukeville 1 degree by 2 degrees quadrangles, Arizona

This map is part of a folio of maps of the Ajo and Lukeville 1 ° x 2° quadrangles, Arizona, prepared under the Conterminous United States Mineral Assessment Program. Other publications in this folio include U.S. Geological Survey Miscellaneous Field Studies Maps MF-1831-A and MF-1831-B and Open-File Reports 82-119, 82–599, and 83–734. Open-File Reports 82-119 and 83–731 constitute the basic data and initial interpretation on which this discussion is predicated.

Arizona↗
USGS1985

Map showing the distribution of selected mineral assemblages in nonmagnetic heavy-mineral concentrates from stream sediments from the Vasquez Peak Wilderness Study Area, and the Williams Fork and St. Louis Peak Roadless Areas, Clear Creek, Grand, and Summit counties, Colorado

The U.S. Geological Survey and the U.S. Bureau of Mines conducted field studies from 1979 through 1983 to assess the mineral resource potential of the Vasquez Peak Wilderness Study Area (acreage: 16,000), the Williams Fork Roadless Area (acreage: 74,820), and the St. Louis Peak Roadless Area (acreage: 12,800). Included were geological, geochemical, and geophysical studies by the U.S. Geological Survey and investigation of known prospects and mines by the U.S. Bureau of Mines.

Colorado↗
USGS1983

Statistical parameters for resource evaluation of geochemical data from the Ajo 1° x 2° quadrangle, Arizona

Statistical data are presented from a regional geochemical study of the Ajo 1° x 2° quadrangle exclusive of the Papago Indian Reservation, but including the extension of Organ Pipe Cactus National Monument into the Lukeville 1° x 2° quadrangle. Frequency distribution data from the analysis of stream-sediment and heavy-mineral-concentrate samples for 31 elements have broad ranges and for most elements have maxima well above normal. Elemental associations derived from correlation and R-mode factor analysis related to regional lithologic variation and for some associations suggest mineral-resource potential.

Arizona↗
USGS1982

Comparison of hot hydroxylamine hydrochloride and oxalic acid leaching of stream sediment and coated rock samples as anomaly enhancement techniques

A hot hydroxylamine hydrochloride (H-Hxl) extraction in 25% acetic acid is compared with the commonly used oxalic acid extraction as a method of anomaly enhancement for Cu and Zn in samples from two very different metal deposits and climatic environments. Results obtained on minus-80-mesh stream sediments from an area near the Magruder massive sulfide deposit in Lincoln County, Georgia, where the climate is humid subtropical, indicate that H-Hxl enhances the anomaly for Cu by a factor of 2 and for Zn by a factor of 1.5, compared to the oxalic method. Analyses of Fe oxide-coated rock samples from outcrops overlying the North Silver Bell porphyry copper deposit near Tucson, Arizona, where the climate is semi-arid to arid, indicate that both techniques effectively outline the zones of hydrothermal alteration. The H-Hxl extraction can also perform well in high-carbonate or high-clay environments, where other workers have suggested that oxalic acid is not very effective. Therefore, the H-Hxl method is recommended for general exploration use.

Journal of Geochemical Exploration↗