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At least 505 records · Page 28Linked to original sources
USGS1980

Chemical and physical characteristics of natural ground waters in Michigan: A preliminary report

Wide variations occur in the chemical and physical characteristics of natural groundwaters in Michigan. Dissolved-solids concentrations range from 23 to 2,100 milligrams per liter. Waters having low dissolved-solids concentrations are calcium bicarbonate waters. Sodium, sulfate, and chloride increase as mineralization increases. Iron, aluminum, and titanium are higher at some locations than is common in most natural waters. Lead concentrations exceed those desirable in drinking water at some locations in the northern part of the Lower Peninsula. Generalized areal patterns of water quality variation suggest that geology is a primary cause of differences across the State. Examples of chemical associations in water suggest that chemical analyses may be valuable in tracing and identifying mineral deposits.

Michigan↗
USGS1982

Preliminary report on the geology and gold mineralization of the Gold Basin-Lost Basin mining districts, Mohave County, Arizona

The Gold Basin-Lost Basin mining districts are adjacent to each other in northwestern Arizona, south of Lake Mead, and just west of the Grand Wash Cliffs. Most recorded production from lode deposits is credited to mines in the Gold Basin district, which is in the southern White Hills, whereas the bulk of the placer production has been from placers worked along the eastern flank of the Lost Basin range, about 16 km to the northeast across Hualapai Valley. Gold in quartz veins apparently was first discovered in the 1870's. Recorded production from the districts between 1901 and 1942 includes 13,508 oz gold and 6,857 oz silver, and this recorded production has a dollar value of about $359,000 of which 98 percent is credited to gold. Most known occurrences of lode gold in the districts are associated with widespread quartz-cored pegmatite-vein systems, presumably emplaced episodically during Proterozoic X, Proterozoic Y, and Late Cretaceous time into Proterozoic X metamorphic and igneous rocks. The bulk of the veins apparently were emplaced during the Late Cretaceous, and they were localized along both high- and low-angle structures in the Proterozoic X terrane. These veins appear to be associated genetically with presumably Late Cretaceous, two-mica magmatism. A Late Cretaceous two-mica monzogranite crops out in an approximately 4 to 5 km 2 area in the southern part of the Gold Basin district and includes some facies of episyenite. Some gold is found also in small episyenitic alteration pipes, or in veins caught up tectonically along a regionally extensive, low-angle detachment surface which crops out prominently in the southern White Hills, and has been traced for at least 30 km along the western flank of the White Hills. Hydrothermal micas from selected veins in the districts give K-Ar ages of 822, 712, 69, 68, and 65 m.y. (million years), and from the pipes, ages of 130 and 127 m.y. The oldest ages (822 and 712 m.y.) presumably reflect resetting of veins that probably were emplaced penecontemporaneous with emplacement of the 1,400-m.y. granite of Gold Butte, which crops out just to the north of Lake Mead. The latter ages (130 and 127 m.y.) must reflect either the presence of excess radiogenic argon in the hydrothermal environment of the evolving pipes, or contamination of the dated mineral separates by Proterozoic mica and (or) feldspar. Primary white mica from the two-mica monzogranite gives a K-Ar age of 72 m.y.. Most occurrences of gold in the veins and pipes probably reflect either remobilization of gold from gold-bearing, near-surface Proterozoic source areas, or anatectic incorporation of gold into Late Cretaceous, two-mica magmas from very deep gold-bearing Proterozoic sources. Deposition of gold occurred in a mesothermal environment during the galena-, chalcopyrite-, ferroan-carbonate-bearing stages of the veins. Homogenization studies of fluid inclusions prominent in the veins and pipes yield temperatures mostly in the range 150 to 280°C. Early-stage, trapping temperatures at the pipes probably were about 330°C and pressures in the range 500 to 700 bars can be inferred. Fluids were moderately saline, mostly 4 to 16 weight percent NaC1 equivalent, nonboiling, and also contain appreciable amounts of carbon dioxide and, in places, fluorine. Such fluids associated with the deposition of gold in these districts largely bridge the fluid composition interval between many other epithermal precious-metal and porphyry coper deposits. Approximately 350 compositional analyses obtained from native-gold samples from 20 mines in the Gold Basin district and 48 veins in the Lost Basin district show silver contents that range from 6 to approximately 50 weight percent, and copper from 0.01 to 0.5 weight percent. Metal zonation and possible relation to a porphyry copper system at depth can be inferred from some of these chemical data. The differences in the composition of placer gold from 24 occurrences in the Lost Basin district from that of nearby lode sources suggest that other sources contributed gold to the placers or that locally derived grains were enriched by oxidation and weathering of the lodes.

Arizona↗
USGS1981

Preliminary report on geophysics ground follow-up of the 1977 airborne survey in the Wadi Bidah District, Kingdom of Saudi Arabia

Reconnaissance geologic and geochemical sampling was made during the 1978 field season at most of the 50 or so electromagnetic anomalies detected in the 1977 airborne electromagnetic (AEM) survey of the Wadi Bidah district. These Phase 1 studies also included reconnaissance geophysical traverses of nine of the AEM conductors. In addition the AEM anomalies were classified on the basis of this reconnaissance work into a list of priority targets for use in economic studies, and six AEM anomalies were selected for further studies. During Phase 2 conducted in the 1979 field season, ground geophysical work consisting of electromagnetic (EM), self-potential (SP), and selected magnetic surveys were carried out in the six targets selected in the Phase 1 studies. These target areas in aggregate cover about 30 km 2, and are approximately half of the Wadi Bidah Class 1 and Class 2 priority targets found during the 1977 airborne electromagnetic (AEM) survey of parts of the Arabian Shield. The results indicate possible extension of known reserves at the Rabathan area (AEM anomaly B-29), with possible potential for mineralization in the area extending 15-20 km north (anomaly B-13), where the geologic and geophysical environment is similar. An important observation is that mineralization in the B-29 (Rabathan) zone is coincident with narrow SP anomalies superimposed on the larger, broader, and more formational-type SP anomalies encountered in both areas B-29 and B-13. AEM anomaly B-25-26 areahas geophysical characteristics that show in the groundwork and that make it an attractive drill target. EM and SP anomalies are associated, in part, with magnetic anomalies and with exposures of significant limonitic gossan. Wadi al Khadra prospect, not included in the 1977 AEM survey, and the AEM anomaly B-25-26 area were also high-mineralization-potential products of the Phase 2 studies. Target area B-35 remains an unknown quantity, and AEM anomaly B-24 is almost certainly due to a carbonaceous schist. Geochemical results, along with detailed geologic mapping and the geophysical data, indicate several potential mineralized targets. Further detailed geophysics (EM and SP) will assist in understanding the geophysical data thus far collected. Further ground follow-up studies are recommended.

Open-File Report↗
USGS1982

Postglacial volcanic deposits at Glacier Peak, Washington, and potential hazards from future eruptions; a preliminary report

Eruptions and other geologic events at Glacier Peak volcano in northern Washington have repeatedly affected areas near the volcano as well as areas far downwind and downstream. This report describes the evidence of this activity preserved in deposits on the west and east flanks of the volcano. On the west side of Glacier Peak the oldest postglacial deposit is a large, clayey mudflow which traveled at least 35 km down the White Chuck River valley sometime after 14,000 years ago. Subsequent large explosive eruptions produced lahars and at least 10 pyroclastic-flow deposits, including a semiwelded vitric tuff in the White Chuck River valley. These deposits, known collectively as the White Chuck assemblage, form a valley fill which is locally preserved as far as 100 km downstream from the volcano in the Stillaguamish River valley. At least some of the assemblage is about 11,670-11,500 radiocarbon years old. A small clayey lahar, containing reworked blocks of the vitric tuff, subsequently traveled at least 15 km down the White Chuck River. This lahar is overlain by lake sediments containing charred wood which is about 5,500 years old. A 150-m-thick assemblage of pyroclastic-flow deposits and lahars, called the Kennedy Creek assemblage, is in part about 5,500-5,100 radiocarbon years old. Lithic lahars from this assemblage extend at least 100 km downstream in the Skagit River drainage. The younger lahar assemblages, each containing at least three lahars and reaching at least 18 km downstream from Glacier Peak in the White Chuck River valley, are about 2,800 and 1,800 years old, respectively. These are postdated by a lahar containing abundant oxyhornblende dacite, which extends at least 30 km to the Sauk River. A still younger lahar assemblage that contains at least five lahars, and that also extends at least 30 km to the Sauk River, is older than a mature forest growing on its surface. At least one lahar and a flood deposit form a low terrace at the confluence of the White Chuck and Sauk Rivers, and were deposited before 300 years ago, but more recently than about 1,800 years ago. Several small outburst floods, including one in 1975, have affected Kennedy and Baekos Creek and the upper White Chuck River in the last hundred years. East of Glacier Peak the oldest postglacial deposits consist of ash-cloud deposits that underlie tephra erupted by Glacier Peak between 12,750 and 11,250 radiocarbon years ago. Although pyroclastic-flow deposits correlative with the ash-cloud deposits have not been recognized, late Pleistocene pumiceous lahars extend at least 50 km downstream in the Suiattle River valley. A younger clayey mudflow extends at least 6 km down Dusty Creek. This lahar is overlain by deposits of lithic pyroclastic flows and lahars that form the Dusty assemblage. This assemblage is at least 300 m thick in the upper valleys of Dusty and Chocolate Creeks, and contains more than 10 km3 of lithic debris. Lahars derived from the Dusty assemblage extend at least 100 km down the Skagit River valley from Glacier Peak. This assemblage is younger than tephra layer 0 from Mount Mazama, and older than tephra layer Yn from Mount St. Helens, and thus was formed between about 7,000 and 3,400 years ago. The Dusty assemblage may have been formed at the same time as the Kennedy Creek assemblage. A 100-m-thick assemblage of pyroclastic flows and lahars preserved in the Chocolate Creek valley is about 1,800 radiocarbon years old. A clayey lahar in the upper Chocolate Creek valley extended at least 2 km downvalley after 1,800 years ago, but before pyroclastic flows and lahars were deposited in upper Chocolate Creek 1,100 radiocarbon years ago. Several clayey lahars in the Dusty Creek valley east of Glacier Peak are also about 1,100 years old. A lahar in the valley of Dusty Creek, which contains rare prismatically jointed blocks of vesiculated dacite, and a white ash that is locally as much as 50 cm thick may be the products of small

Open-File Report↗
USGS1983

Preliminary report on geology, geochemical exploration, and biogeochemical exploration of the Red Mountain stockwork, Yellow Pine District, Valley County, Idaho

New exploration targets for gold, molybdenum, tungsten, and tin are indicated by the systematic distribution of metals in soil and plants of the Red Mountain stockwork and its environs. The stockwork is built of countless quartz veins and veinlets, extensively argillized and containing sparsely disseminated gold, pyrite, arsenoDyrite, Dyrrhotite, fluorite, and other minerals. The stockwork developed along the outer ring-fracture zone of the Eocene Quartz Creek cauldron where subsidence strain, unrelieved by radial faulting, produced internal deformation and intense small-scale fracturing in rocks of the Idaho batholith. The stockwork, cropping out as a fault-bounded polygon 2,700 ft long and 2,000 ft wide, contains (underlies?) a large, virtually barren quartz body 1,350 ft long and 350 ft wide. Deformed, shattered granite flanks and presumably underlies the stockwork, which may plunge southward beneath inclusion-bearing granodiorite and alaskite of the Idaho batholith suite. Narrow dikes of rhyolite and latite radiate from two centers within the quartz body. Many dikes and small bosses of rhyolite and latite intrude stockwork and granite. The radial habit of some dikes and the high frequency of small intrusives concentrated within the sericite and kaolinite alteration zones suggest that a Tertiary porphyry is concealed beneath the mountain. Clay-mineral alteration zones mapped in residual soil extend far outward from the stockwork. Valleys filled with Quaternary deposits bound the stockwork-granite complex on the east, north, and west, effectively concealing elements of a crudely elliptical substructure that differs from the fault-dissected, mappable part of the complex. Metal anomalies in soil of the 3,600-ft x 8,400-ft gridded area are mostly weak and small. In contrast, metal anomalies in plants are strong, large, and consistent with the inference of a concealed elliptical substructure that may be hoodlike and may contain more than one mineralized zone. Gold in ashed sapwood of douglas-fir (Pseudotsuga menziesii) indicates a major gold anomaly, peak value 14.2 ppm Au, on inclusion-bearing granodiorite in an unprospected area south of the exposed stockwork. Locally, the gold anomaly is accompanied by a sizable tin anomaly, peak value 100 ppm Sn, in douglas-fir. Molybdenum in ashed leaves of beargrass (Xerophyllum tenax), peak value >500 ppm Mo, indicates extensive anomalies within a 2-milelong semi-elliptical belt of Mo values exceeding the 20 ppm median. Most of the belt is on valley fill, but the southern segment of it, near the major gold anomaly, is mainly on inclusion-bearing granodiorite. Here, where beargrass is sparse, the peak value of Mo in beargrass drops to 70 ppm. Where beargrass is absent, ashed leaves of sedge (Carex geyeri) have anomalous values of 100 ppm Mo. An additional target for molybdenum is indicated by molybdenite from the inaccessible Dart of the main adit. The molybdenite, seen only in dump specimens, is in weakly silicified granite that may underlie part of the stockwork. The source body of the molybdenite is blind, and no clue to it is given by samples of soil or plants. Just north of the major gold anomaly, 2 ppm values of W in beargrass coincide approximately with a tungsten anomaly in soil (peak value 22 ppm W) in an area of float containing disseminated scheelite in weakly silicified inclusion-bearing granodiorite. Other areas of 2 ppm W values in beargrass are nearly coextensive with the Moin-beargrass anomalies on Quaternary deposits of Quartz Creek valley. Some of the target areas for gold, molybdenum, tungsten, and tin have not been circumscribed by our sampling.

Open-File Report↗
USGS1983

Regional magnetic and gravity features of the Gibson Dome area and surrounding region, Paradox Basin, Utah: A preliminary report

Analyses of regional gravity and magnetic anomaly maps have been carried out to assist in the evaluation of the Gibson Dome area as a possible repository site for high-level radioactive waste. Derivative, wavelength-filtered, and trend maps were compiled to aid in properly locating major geophysical trends corresponding to faults, folds, and lithologic boundaries. The anomaly maps indicate that Paradox Basin is characterized by a heterogeneous Precambrian basement, essentially a metamorphic complex of gneisses and schist intruded by granitic rocks and mafic to ultramafic bodies. Interpreted Precambrian structures trend predominantly northwest and northeast although east-west trending features are evident. Prominent gravity lows define the salt anticlines. Structural and lithologic trends in the Gibson Dome area are closely examined. Of greatest interest is a series of circular magnetic highs trending west-northwest into the Gibson Dome area. Further study of the exact definition and geologic significance of this series of anomalies is warranted.

Utah↗
USGS1983

Preliminary report on near-surface lignite occurrences, Cleveland County, Arkansas

Four cross sections were constructed from lithologic descriptions of 43 drill holes in Cleveland County, Ark., in order to illustrate the occurrence of lignite and to relate the lignite beds to the regional stratigraphic framework. Of 43 holes drilled, 8 contained beds of lignite, but only two had beds greater than 30 in. thick. These beds are apparently lenticular and are restricted to the upper 60 ft. of the Cockfield Formation of the Claiborne Group of Middle Eocene age. The Cockfield Formation is at or near the surface west of the Saline River.

Open-File Report↗