Applied Geochemistry, Geology, and Mineralogy of the Northernmost Carlin Trend, Nevada

Theodore, Ted G.; Kotlyar, Boris B.; Singer, Donald A.; Berger, Vladimir I.; Abbott, Earl W.; Foster, Andrea L.

doi:10.2113/gsecongeo.98.2.287

Cited by 21 publications

(2 citation statements)

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“…Arsenic is known to be mobile in the surficial environment, and Theodore et al (2003) have shown directly, using X-ray absorption fine structure spectroscopy, that arsenic is commonly fixed in stream sediments as an element adsorbed onto clay minerals. Their conclusions regarding arsenic mobility and fixation are supported by our very large data set.…”

Section: Ludington Et Almentioning

confidence: 99%

Regional Surficial Geochemistry of the Northern Great Basin

Ludington¹

2006

Economic Geology

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The regional distribution of arsenic and 20 other elements in stream-sediment samples in northern Nevada and southeastern Oregon was studied in order to gain new insights about the geologic framework and patterns of hydrothermal mineralization in the area. Data were used from 10,261 samples that were originally collected during the National Uranium Resource Evaluation (NURE) Hydrogeochemical and Stream Sediment Reconnaissance (HSSR) program in the 1970s. The data are available as U.S. Geological Survey Open-File Report 02-0227.The data were analyzed using traditional dot maps and interpolation between data points to construct highresolution raster images, which were correlated with geographic and geologic information using a geographic information system (GIS). Wavelength filters were also used to deconvolute the geochemical images into various textural components, in order to study features with dimensions of a few kilometers to dimensions of hundreds of kilometers.The distribution of arsenic, antimony, gold, and silver is different from distributions of the other elements in that they show a distinctive high background in the southeast part of the area, generally in areas underlain by the pre-Mesozoic craton. Arsenic is an extremely mobile element and can be used to delineate structures that served as conduits for the circulation of metal-bearing fluids. It was used to delineate large crustal structures and is particularly good for delineation of the Battle Mountain-Eureka mineral trend and the Steens lineament, which corresponds to a post-Miocene fault zone. Arsenic distribution patterns also delineated the Black Rock structural boundary, northwest of which the basement apparently consists entirely of Miocene and younger crust.Arsenic is also useful to locate district-sized hydrothermal systems and clusters of systems. Most important types of hydrothermal mineral deposit in the northern Great Basin appear to be strongly associated with arsenic; this is less so for low-sulfidation epithermal deposits.In addition to individual elements, the distribution of factor scores that resulted from principal component studies of the data was used. The strongest factor is characterized by Fe, Ti, V, Cu, Ni, and Zn and is used to map the distribution of distinctive basalts that are high in Cu, Ni, and Zn and that appear to be related to the Steens Basalt. The other important factor is related to hydrothermal precious metal mineralization and is characterized by Sb, Ag, As, Pb, Au, and Zn. The map of the distribution of this factor is similar in appearance to the one for arsenic, and we used wavelength filters to remove regional variations in the background for this factor score. The resulting residual map shows a very strong association with the most significant precious metal deposits and districts in the region. This residual map also shows a number of areas that are not associated with known mineral deposits, illustrating the utility of the method as a regional exploration tool. A number of these prospective are...

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Section: Ludington Et Almentioning

confidence: 99%

Regional Surficial Geochemistry of the Northern Great Basin

Ludington¹

2006

Economic Geology

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Tectonic position of the Alshar Au-As-Sb-Tl deposit, Macedonia

et al. 2006

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During the second half of the 20th century, several dozen large and medium deposits of disseminated pyrite-marcasite ores with total gold reserves of more than 6000 t and annual gold production of ~200 t were found in the Basin and Range Province, Nevada, United States [1,2]. This unique gold district is termed as the Carlin trend. The limited development of the Carlintype mineralization in other gold districts of the world is presently a debated issue. Naturally, each Carlin-type mineralization inferred beyond Nevada requires detailed investigations. In 2004, we began to study the Alshar deposit with Carlin-type mineralization together with Macedonian geologists [3]. The Alshar deposit is a large object in terms of Tl reserves and a medium reserve in terms of inferred Au reserves [3,4].The territory of Macedonia experienced long-term geological evolution. Its majority is occupied by the Serbian-Macedonian and Pelagonia crystalline massifs, separated by the Mesozoic Vardarian riftogenic graben ( Fig. 1). Macedonia is located in the SerbianMacedonian part of the Eurasian Tethys metallogenic belt. Mineralization related to the Cenozoic activation in this area is expressed in the formation of volcanoplutonic associations in the dispersed spreading environment [4]. The activation spanned the Serbian-Macedonian Massif and part of the Vardarian riftogenic zone. Superimposed structures of this period occur as narrow NW-trending grabenlike depressions complicated by local ring structures of the chamber type.Previous joint works with Macedonian geologists showed that the present-day tectonic structure of Macedonia reflects dislocations closely related to Cenozoic magmatism and productive mineralization. These dislocations were reconstructed from tectonic elements of the present-day relief surface using morphostructural analysis and deciphering aerial and satellite photographs. Based on the dislocations, we distinguished three (Oligocene-Miocene) NW-trending metallogenic zones superimposed onto the metamorphic sequence of the Serbian-Macedonian Massif. They are mainly composed of the Cenozoic tuffogenic-sedimentary and volcanic sequences and are crosscut by granitoids and dikes of intermediate composition. The metallogenic zones compose an ore belt (Fig. 1), which extends to the northwest (Serbia) and southeast (Greece and Bulgaria).From southwest to northeast, the metallogenic zones show variation in ore type and decrease in age of magmatic complexes and ores. One can see a distinct correlation between age and ore composition. Northeastward, the mineralization evolves from high-temperature (relatively low-sulfide) to low-temperature (polysulfide) types. The directed change of ore composition can be related to differentiation of ore matter in the deep-seated chambers. The ore type changes across metallogenic zones in the following way: skarn-magnetite ores (Borov Dol deposit), porphyry copper ores (Buchim), base metal copper ores (Kratovo-Zletovo), and base metal ores (Sasa and Toranica). In the SW-NE direction, the age o...

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Laznicka¹

2010

Giant Metallic Deposits

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Applied Geochemistry, Geology, and Mineralogy of the Northernmost Carlin Trend, Nevada

Cited by 21 publications

References 47 publications

Regional Surficial Geochemistry of the Northern Great Basin

Regional Surficial Geochemistry of the Northern Great Basin

Tectonic position of the Alshar Au-As-Sb-Tl deposit, Macedonia

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