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A. A. Bookstrom

Publications and source records attributed to A. A. Bookstrom.

7 recordsLinked to original sources
USGS2001

Assessment method for epithermal gold deposits in northeast Washington State using weights-of-evidence GIS modeling

The weights-of-evidence analysis, a quantitative mineral resource mapping tool, is used to delineate favorable areas for epithermal gold deposits and to predict future exploration activity of the mineral industry for similar deposits in a four-county area (222 x 277 km), including the Okanogan and Colville National Forests of northeastern Washington. Modeling is applied in six steps: (1) building a spatial digital database, (2) extracting predictive evidence for a particular deposit, based on an exploration model, (3) calculating relative weights for each predictive map, (4) combining the geologic evidence maps to predict the location of undiscovered mineral resources and (5) measuring the intensity of recent exploration activity by use of mining claims on federal lands, and (6) combining mineral resource and exploration activity into an assessment model of future mining activity. The analysis is accomplished on a personal computer using ArcView GIS platform with Spatial Analyst and Weights-of-Evidence software. In accord with the descriptive model for epithermal gold deposits, digital geologic evidential themes assembled include lithologic map units, thrust faults, normal faults, and igneous dikes. Similarly, geochemical evidential themes include placer gold deposits and gold and silver analyses from stream sediment (silt) samples from National Forest lands. Fifty mines, prospects, or occurrences of epithermal gold deposits, the training set, define the appropriate a really-associated terrane. The areal (or spatial) correlation of each evidential theme with the training set yield predictor theme maps for lithology, placer sites and normal faults. The weights-of-evidence analysis disqualified the thrust fault, dike, and gold and silver silt analyses evidential themes because they lacked spatial correlation with the training set. The decision to accept or reject evidential themes as predictors is assisted by considering probabilistic data consisting of weights and contrast values calculated for themes according to areal correlation with the training sites. Predictor themes having acceptable weights and contrast values are combined into a preliminary model to predict the locations of undiscovered epithermal gold deposits. This model facilitates ranking of tracts as non-permissive, permissive or favorable categories based on exclusionary, passive, and active criteria through evaluation of probabilistic data provided by interaction of predictor themes. The method is very similar to the visual inspection method of drawing conclusions from anomalies on a manually overlain system of maps. This method serves as a model for future mineral assessment procedures because of its objective nature. To develop a model to predict future exploration activity, the locations of lode mining claims were summarized for 1980, 1985, 1990, and 1996. Land parcels containing historic claims were identified either as those with mining claims present in 1980 or valid claims present in 1985. Current claim parcels were identified as those containing valid lode claims in either 1990 or 1996. A consistent parcel contains both historic and current claims. The epithermal gold and mining claim activity models were combined into an assessment (or mineral resource-activity) model to assist in land use decisions by providing a prediction of mineral exploration activity on federal land in the next decade. Ranks in the assessment model are: (1) no activity, (2) low activity, (3) low to moderate activity, (4) moderate activity and (5) high activity.

Washington↗
USGS1999

Assessing the influence of reacting pyrite and carbonate minerals on the geochemistry of drainage in the Coeur d'Alene mining district

The relative abundance of minerals that react to generate or consume acid in mineralized areas is critical in determining the quality of water draining from such areas. This work examines the fundamental reactions that influence the pH and composition of drainage from mine adits and tailings piles. We construct triangle diagrams that predict stoichiometric relationships between concentrations of dissolved SO4 dissolved Ca and Mg, and either alkalinity or acidity by considering reactions involving the oxidation of pyrite, dissolution of carbonate minerals, and precipitation of iron oxide and iron hydroxysulfate minerals. Drainage data from the Coeur d'Alene mining district are used to test our stoichiometric approach. Comparisons between theoretical predictions and drainage data indicate that the range of pH values in the mining district is due to reacting pyrite to carbonate mineral ratios that range from near 0/1 to 1/1. Calcite and ankerite are the dominant carbonate minerals that buffer the acid produced during pyrite oxidation and ferrihydrite or schwertmannite precipitation.The relative abundance of minerals that react to generate or consume acid in mineralized areas is critical in determining the quality of water draining from such areas. This work examines the fundamental reactions that influence the pH and composition of drainage from mine adits and tailings piles. We construct triangle diagrams that predict stoichiometric relationships between concentrations of dissolved SO4, dissolved Ca and Mg, and either alkalinity or acidity by considering reactions involving the oxidation of pyrite, dissolution of carbonate minerals, and precipitation of iron oxide and iron hydroxysulfate minerals. Drainage data from the Coeur d'Alene mining district are used to test our stoichiometric approach. Comparisons between theoretical predictions and drainage data indicate that the range of pH values in the mining district is due to reacting pyrite to carbonate mineral ratios that range from near 0/1 to 1/1. Calcite and ankerite are the dominant carbonate minerals that buffer the acid produced during pyrite oxidation and ferrihydrite or schwertmannite precipitation.

Idaho↗
USGS1998

Drainage from adits and tailings piles in the Coeur d'Alene mining district, Idaho; sampling, analytical methods and results

This report contains information about collecting, handling, and analyzing waters draining from adits and seeping from beneath tailings piles in the Coeur d'Alene mining district during August 1996, November 1996, and June 1997. Data include temperature, pH, conductivity, dissolved oxygen, alkalinity, flow, and total acid soluble and dissolved (<0.45 \im) major and trace ion concentrations for 11 adits and 5 tailings deposits. Interpretations of these data will be discussed in other publications.

Idaho↗
USGS1991

Reconnaissance geochemical survey of the Farah Garan-Kutam mineral belt, Kingdom of Saudi Arabia

Wadi-sediment samples were collected from 450 sites in a 580-km 2 area (sample density 1.5 per km 2 ) as part of an exploration program designed to assess the mineral potential of the Farah Garan - Kutam mineral belt and to evaluate mineralization at the Farah Garan ancient working (DGMR Project 3.03.10). Demagnetized panned-concentrate and sieved minus-80-mesh fractions were prepared from each bulk sample of approximately 5 kg. The fractions were analyzed for silver, arsenic, copper, lead, and zinc by atomic-absorption methods and for gold by an atomic-absorption graphite-furnace method. The analytical results for the panned-concentrate samples delineate 21 anomalies, and the results for the minus-80-mesh samples delineate 24. Of the latter, 14 are coincident with panned-concentrate anomaly areas, whereas 10 are uniquely defined. The analytical results of the panned-concentrate samples uniquely define two areas. Overall, the panned-concentrate samples yielded threshold values higher than the threshold values for the minus-80-mesh samples (for gold, 10 times higher), and delineate anomalous areas larger than those for the minus-80-mesh samples. This observation is consistent with the results of similar surveys elsewhere in the Arabian Shield, which indicate that panned-concentrate samples more effectively outline geochemical anomalies than sieved fine-grained samples. In the present survey, geochemical anomalies locate all the sites of mineralization known from previous work. The survey is therefore technically a success. However, a large number of these anomalies probably result from contamination of the wadi systems by metal dispersed from ancient mine workings, and this particular survey, overall, may be of limited value as a guide to the discovery of hitherto unknown mineralization. Nevertheless, the survey outlines two areas that may mark extensions to known mineralization, and a number of other areas in which no mineralization is known. Based on a consideration of the character of the bedrock geology, the value of each reported analytical result in relation to the respective element thresholds, and the number of anomalous samples that cluster in any given area, four areas are recommended for high-priority follow-up sampling.

Open-File Report↗
USGS1990

Reconnaissance geochemical exploration for gold in the Ad Darb area, Kingdom of Saudi Arabia

Geochemical data were analyzed for 244 wadi-sediment samples in an attempt to locate gold exploration targets in late Proterozoic metasedimentary and metavolcanic rocks in the Ad Darb area of the southern Arabian Shield. The target was gold mineralization in high-alumina alteration zones of the type that occurs in the Carolina Slate Belt, eastern United States. Such a target was sought in the Ad Darb area because of the known presence of kyanite in schist of the Sabya formation, which was interpreted to be a possible indicator of late Proterozoic high-alumina hydrothermal activity in the region. Overall, metal values in the wadi-sediment samples are low. The known kyanite mineral occurrence is marked by anomalous gold and tin in three minus-80-mesh samples. The low values of the metals do not justify further exploration for the sought deposit type in the immediate vicinity, although the signature of anomalous elements in the wider region is comparable to the signature known in the Carolina Slate Belt, and is permissive of the interpretation that a diffuse hydrothermal system operated in the region during the late Proterozoic. A large concentration of polymetallic anomalies (gold, arsenic, copper, antimony, tin, tungsten, and lead) is outlined in the northeastern part of the survey area on the basis of panned-concentrate samples. The source of the concentration is unknown, and further investigations are recommended. Recommended low-priority investigation of the source of lead and zinc anomalies in the western part of the survey area would be justified as part of a larger program designed to evaluate the mineral potential of the entire belt of Sabya formation rock.

Open-File Report↗
USGS1990

Hamdah ancient gold mines, Kingdom of Saudi Arabia

The Hamdah prospect is a 1.5-km 2 area that includes ancient mine workings 15 km southeast of Hamdah in the southern Arabian Shield. The workings cluster at a gently dipping thrust contact between serpentinite (above) and hornblende schist (below) exposed in a window within the serpentinite. Aplite sills intrude the contact, and gold concentrations occur just above or below it. The ancient mine dumps cover >100,000 m 2 of the prospect and are estimated to be 1.5 to 1.8 m thick. They contain nearly 181,000 metric tons of material at an average grade of 4.5 g/t gold, thus having an estimated total gold content of 831 kg, or 26,726 Troy oz. Almost 100 percent of the contained gold is recoverable by cyanide acid leaching. Eleven new diamond-drill holes were completed to supplement information from 12 drill holes completed during an earlier drilling program, in order to enable more detailed evaluation of the prospect. The drill holes are grouped in the northeast, southeast, southwest, and west quadrants of the prospect. In the northeast quadrant, where 9 drill holes intersect gold at shallow (<27 m) depths, the quadrant is calculated to contain nearly 242,300 metric tons of gold-bearing material. The calculations show: (1) 19,144 metric tons high-grade material grading 21.4 g/t Au at 5 g/t cutoff; (2) 39,884 metric tons of material grading 8.5 g/t Au at 5 g/t cutoff; (3) 71,617 metric tons of material grading 3.9 g/t Au at 1 g/t cutoff; and (4) 111,641 metric tons low-grade material grading 2.0 g/t Au at 1 g/t cutoff. Total gold content of this selected block is 1,251 kg gold, or 40,234 Troy oz. The mineralized zone in 1 the northeast quadrant is open to the northeast, east, and southeast. Drill data are insufficient in detail to allow grade or tonnage estimates for the southeast, southwest, and west quadrants of the prospect. Gold is concentrated in surface alluvium in the southeast and southwest of the prospect, in amounts that are of possible economic significance. Ground geophysical surveys (CEM and VJJ7) revealed the presence of electrical conductors at shallow depths, some of which correlate with possible disseminated sulfide minerals, and others with the thrust contact. It is recommended that the thickness of the dumps be more accurately determined, and that the gold leachability of bulk dump material be tested. Shallow reverse-circulation drilling is recommended on 25-m centers in the northeast quadrant, and diamond drilling is recommended elsewhere at the prospect. Geophysical surveys are required to help establish depths to the serpentinite/schist contact on the northeastern, southern, and western margins of the prospect. Detailed mapping should be undertaken at the prospect, and a mineral-belt type of mapping program should be completed over the larger Hamdah region.

Open-File Report↗