Wyoming Uranium Province
Bill Boberg, Ur-Energy Inc, Denver, Colorado
This is an outline of the NWMA Uranium Short Course that was presented December 4-5, 2006.
Wyoming Uranium History
Comparison of Wyoming Exploration & Production to rest of US
Current Production and Exploration Activity
Description of Wyoming Uranium Deposits
Nature of Deposits
Development of the Wyoming Uranium Province
Source of the Uranium
Age of the mineralizing event
Controls on district development
Roll front and deposit development
Exploration for Wyoming Sandstone Deposits
Generalized sequence of exploration
Uranium roll-front geometry
Gamma log interpretation
Fluvial channel stratigraphy and sedimentation
Examples from the Great Divide Basin
Relationship to other districts in Wyoming
Basin-wide roll front and deposit development
Stratigraphic and Sedimentologic controls on deposits
Mineral Mapping Approach Using Airborne and Satellite Imaging Systems:
Keeping Pace with Remote Sensing Technology Advancements
Sandra L. Perry
Perry Remote Sensing, LLC, Englewood, Colorado, USA
The last six years have seen vast improvements in the realm of mineral mapping and worldwide exploration from a remote-sensing standpoint. This comes at a time when the mining industry is faced with formidable field mapping and logistics challenges. Improved spatial and spectral resolution sensors offer readily available solutions for field geologists and explorationists that integrate with Geographic Information System (GIS) software and Global Positioning System (GPS) capabilities.
The presentation will review NASA-funded mineral mapping research based upon an approach testing airborne and satellite digital imagery. This research uses multispectral Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite data to extend Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) hyperspectral imaging (HSI) endmember results to regional scales for geologic mapping and alteration mineral modeling. HSI data have hundreds of spectral bands, which allow direct identification of minerals using fully resolved spectral signatures. Spatial coverage using HSI data is confined to small surveys and therefore limited. ASTER data do not have the same high spectral resolution as HSI data but provides broader spatial coverage (~60 X 60 km). The approach utilizes integration and spectral/spatial scaling of nested HSI/multispectral data sets to model and predict ASTER spectral signatures. The predicted signatures are then used to extend hyperspectral mapping results to the larger synoptic spatial coverage of ASTER, thus improving geologic mapping and monitoring for areas not covered by hyperspectral data.
Several test case areas in North and South America are being investigated with selection based upon variable deposit models, terrain, and geologic setting. Two examples will be discussed here. Analysis of AVIRIS and ASTER data for hydrothermally altered rocks near Los Menucos, Argentina serves to illustrate the approach using coincident HSI/ASTER data for mapping an epithermal Au/Ag system. Key minerals, including muscovite/sericite, kaolinite, alunite, pyrophyllite, and carbonates were successfully extended to several ASTER scenes. ASTER mineral mapping at a prospective copper mine at Cashin, Colorado produced results consistent with sericite/muscovite and kaolinite mapping performed using AVIRIS and proposed mineral endmembers. Copper mineralization is found in reduced, altered massive sandstone units characterized by the absence of FeOx and intensification of sericite/muscovite. ASTER analysis, based upon HSI mineral endmembers, demonstrates that sandstone facies changes can be mapped based upon altered and unaltered exposures. Other mineral mapping was successful, including classification detecting kaolinite, montmorillonite, and illite. In both case histories, fieldwork follow-up utilized field-portable spectrometers, real-time GPS mapping, and GIS database development. Mineral mapping pitfalls will also be discussed.
It is significant that ASTER can identify many key minerals associated with specific geologic units, metal deposits, and alteration. In evaluating very different geologic models and terrain over the past two years, ASTER remains far in advance of LANDSAT for differentiating clays, carbonates, silicates, and sulfates. This mineral modeling approach provides a consistent method for detecting and identifying specific minerals based on physical properties (spectral signatures) and extending them to regional coverage.
In addition, a brief overview will be presented on high-spatial resolution (or hi-res) satellite imagery offering 1-meter and 60-cm pixel sizes. These data are ideal for field mapping and logistics down to 1 inch equals 200 feet mapping scale on a worldwide basis. While not suited for mineral prediction due to limited spectral bands, hi-res imagery is ideal for field follow-up work not to mention survey planning, logistics, and mobilization for remote locations.
Structural Evolution of the central Yukon-Tanana Upland-How Regional Deformation Nourishes the (Ore) Body
Warren C. Day, U.S. Geological Survey, Mail Stop 911, Denver Federal Center, Lakewood, CO, USA, 80225; firstname.lastname@example.org
The Yukon-Tanana Upland is a greater than 1,000 km-long arcuate-shaped crystalline block bounded on the north and south by the Tintina and Denali fault systems, respectively. These two fault systems form a regional dextral wrench zone that is transected by several major northeast-striking steep faults and lineaments. The Upland hosts major gold deposits, such as the Pogo (10 m oz.), Fort Knox, True North, and Donlin Creek, as well as numerous prospects, such as the Brink, Grey Lead, Blue Lead, and Grizzly prospects. The region is and will continue to be a prime area for gold exploration in North America. The US Geological Survey Mineral Resources Program has been conducting integrated geologic and geoenvironmental studies in the Upland to understand the regional geologic framework of the ore-bearing systems as well as to help define pre-mining background values of potentially deleterious metals that occur naturally in pristine regions not impacted by mining. This talk focuses on the tectonic evolution of the Big Delta 1x3 degree quadrangle, which lies in the central part of the Upland in east-central Alaska.
The Big Delta quadrangle is underlain predominantly by Paleozoic and Cretaceous crystalline bedrock. The Paleozoic units include biotite + sillimanite gneiss, quartzite intermixed with pelite, and amphibolite, whose protoliths were continentally-derived siliciclastic sediments, shales, and mafic volcanic rocks, respectively. The protoliths, which were deposited on the northwestern margin of the North American continent, were intruded by calc-alkaline plutons during the Devonian and Mississippian. The Middle Paleozoic plutonism marks the earliest recognized tectonic event for the region.
During Jurassic through Late Cretaceous time, the Pacific plate collided with the North American plate, causing dextral transpressive deformation and associated northwest-vergent thrusting. In the Big Delta quadrangle area, Late Cretaceous plutonism invaded the area with calc-alkaline granodioritic to granitic batholiths. During the waning stages of the Late Cretaceous deformation in the Big Delta quadrangle, numerous pluton-related gold systems formed within the margins of the intrusions (for example, Brink), as well as in the adjoining country rock (for example, Pogo. In the eastern part of the Big Delta quadrangle, a northeast-trending structural corridor, the Black Mountain tectonic zone, both controlled the emplacement of some of the Late Cretaceous intrusive rocks and gold deposits and prospects (for example, Blue Lead, Gray Lead, and Grizzly prospects) and formed a conduit along which a rhyolite flow-dome complex subsequently erupted during the Paleocene.
Tertiary uplift and erosion resulted in the development of extensive erosional pediments. Quaternary alpine glaciation carved beautiful, broad valleys in the eastern part of the quadrangle. Continual deformation along the Black Mountain tectonic zone has offset Tertiary terraces, disrupted some of the gold prospects, as well as Quaternary fluvial and alluvial deposits, indicating that the area has a long, complex, and ongoing tectonic history.
The talk will present several Athabasca unconformity type deposits for comparison; models for genesis will be shown; size and grade of some major deposits will be given. The Cigar Lake and McArthur River deposit mineralization and alteration will be compared. Then, a tour through the McArthur River mine, following the ore as it is trucked and put through the mill at Key Lake. Views of the Sue C and Rabbit Lake open pit mineralization will be presented, along with discovery pitchblende cobbles from Cluff Lake. Emphasis will be placed on the large differences between major deposits in the ?unconformity? family. Basically, I?ll try to organize an informative story of the world?s best uranium district based on my occasional Athabasca uranium experiences of the past 30 years.
May Technical Presentation
Exploration Opportunities for Gold and Copper in Eastern Iran: a new mineral deposits database
Eastern Iran has undergone at least two major episodes of plate tectonic activity: 1-Paleo-Tethys (Paleozoic) and 2-Neo-Tethys (Mesozoic-Tertiary). Both started as intercontinental rifting followed by invasion of the Tethys ocean. Later, subduction began, the ocean started to close, and volcanic-plutonic belts were formed. The final stage brought continental collision, magmatism and regional metamorphism. 65 to 70 percent of exposed rocks in Eastern Iran are primarily volcanic, some intrusive, mainly Tertiary, some Mesozoic.
Eastern Iran has great potential for mineral exploration, but little exploration is being done at present. Commodities being mined include: Cu-Au-Ag, Fe, Cr, kaolin, perlite, bauxite, pumice, silica, gypsum, salt, barite, fluorine, talc, magnesite, facing and decorative stones, diatomite, coal, feldspar, fireclay, limestone, shale and marl. Abandoned mines exploited Pb, Zn, Cu, Cr, Mn, As, and Sb.
Exploration is taking place for different types of Au and Cu-Au deposits which have been identified in Eastern Iran. Kuh-e-Zar is a gold deposit. It is a specularite-rich Au deposit (Iron Oxide Copper-Gold type). A different style of mineralization occurs in veins, stockworks and hydrothermal breccias. The main minerals are quartz, specularite and minor sulfides. Host rocks are Tertiary rhyolite, andesite, diorite and monzodiorite. The ore reserves based on an Au cutoff grade of 0.7 ppm is estimated at 3 million metric tons averaging 3.02 ppm Au. The main alteration is propylitic, silicification and albitization with minor argillic and sericitic. Fluid inclusion thermometry was useful in exploration strategy. Based on this study, areas with favorable gold grade were deposited between 325°C -295°C.
The Tannurjeh Au-Cu porphyry prospect is located about 35 km west of Kuh-e-Zar. Eocene rhyolite, dacite, rhyodacite and minor andesite are intruded by a series of sub-volcanic rocks. Nineteen subvolcanic (Oligo-Miocene) bodies of monzonite, quartz monzonite, diorite and quartz diorite porphyry have been mapped. Different types of alteration such as propylitic, advanced argillic with kaolinite, alunite and vuggy silica are well developed in the area. The silicified zone covers a large area. Pyrite and minor chalcopyrite are the main primary sulfides. They occur both disseminated and as fracture filling. Secondary oxides are between 0.3 - 8 percent. Au, Cu, Zn, Pb, As, and Mo show anomalies in the area. The Au content of surface rock samples are between 0.1 - 11.2 ppm (average 0.25 ppm).
Hired gold prospecting area is located 160 Km south of Birjand, in eastern Iran. I and S-type granitoids intruded Eocene and older rocks. Gold and tin mineralization is associated with the S-Type. Hypogene minerals are: pyrite, arsenopyrite, pyrrhotite, chalcopyrite, +/- galena, +/- sphalerite, tourmaline, quartz, chlorite, calcite and sericite. Stockwork mineralization is found within or adjacent to S-type granite. Temperature of homogenization of primary fluid inclusions in quartz stockwork associated with tourmaline, arsenopyrite, and gold is between 400-500°C. Further away from the source rock, gold deposited within veins and replacement bodies at < 300°C. Gold grade varies between 0.1 to 6 ppm and Sn is up to 570 ppm.
The Qaleh-Zari specularite- rich Cu-Au-Ag deposit is located 175 from Birjand. Host rocks are mainly Tertiary andesite and andesitic basalts and some Jurassic shale and sandstone. Three major sub-parallel steep quartz veins are identified. No.1 vein is about 650 m long, and No.2 vein is traced for more than 3.5 km horizontally along strike (N400W) and more than 350 m down dip. No.3 vein is less than 500m long.Paragenesis: Stage I: specularite, quartz, Fe-chlorite, chalcopyrite and sulfosalts. Specularite deposited first and forms 10 to 25 percent of the vein. Stage II: quartz, chalcopyrite, pyrite, chlorite +/- hematite +/- sulfosalt minerals. Stage III: quartz +/- pyrite +/- chalcopyrite. Stage IV: hematite, quartz, and +/- calcite. Ore grade is 2 to 9% Cu, Ag 100 to 650 ppm, and Au 0.5 to 35 ppm. Propylitic alteration is dominant and epidote is very abundant. Argillic alteration is locally present. Silicification is mainly found within the vein zone. Temperature of homogenization of primary fluid inclusions in quartz associated with specularite and Cu, Ag, and Au mineralization was between 240°C and 360°C. The salinity of ore fluid was between 1.0 and 6.0 wt% equiv. NaCl and the CO2 was < 0.1 mole%. The fluid was very oxidizing, Log fO2 was between -13 and -28 (T 300°C). The δ34S per mil (CDT) values of pyrite and chalcopyrite are between 0.4 and 2.2 per mil. The origin of the sulfur may be: 1) direct input from a buried pluton, or 2) leached from the host volcanic rocks.
Based on the GIS database, several Cu-Au mineralized systems were identified. Maherabad and Chah Shalghami are two examples. Both Aster and ground checking revealed very broad altered zones characteristic of Cu-Au porphyry systems. Quartz monzonite and intense stockworks all confirm a Cu-Au porphyry deposit. Based on the presence of quartz-sericite-pyrite and intense quartz stockwork (A-type), the top of the system is being eroded away. Chah Shalghami is situated 15 Km southwest of Qaleh Zari Cu-Au-Ag mine. Alteration zones are 2 to 3 Km2 . Alteration zones at Chah Shalghami are: alunite, silicified, propylitic and argillic. Host rocks are mainly Tertiary volcanic rocks and they are intruded by small dikes and plugs of monzonite and quartz monzonite porphyry.
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September Technical Presentation
Application of the GoreTM Module Soil Gas Geochemistry
Technology to Oil & Gas and Minerals Exploration
Anne Leibold, Mark Arnold, and Don Baker, Royalty Exploration LLC, Lakewood, CO
A variety of technologies, sampling and analytical approaches have been or are employed in attempting to outline near-surface, soil-hosted chemical signatures derived from deeper contaminant plumes, oil and gas accumulations and mineral deposits. These approaches all try to adequately sample, analyze and interpret chemical signatures resulting from transport, in one fashion or another, of metals and gases from the deeper source to the near-surface environment. Approaches include soil sampling and wet chemical analysis using total digestion or various partial digestion and leaching methods; and soil gas analysis targeting CO2, O2, Hg, and a wide variety of sulfur species gases, hydrocarbons, and, in the environmental sector, certain contaminants (commonly hydrocarbons). The gas sampling and measurement methodologies range from active pumping approaches, to direct in situ measurement, to passive collection approaches requiring certain in-soil residence periods for gas collection followed by laboratory analysis.
Passive sampling of soil gases using the GoreTM Module technology in environmental and oil & gas sectors has proven highly effective in mapping plumes of certain contaminants, and hydrocarbon distributions, respectively. Potential application to minerals exploration programs is being evaluated through the generation of a number of case studies over known metal deposits representing a wide variety of deposit types. The approach has been empirical, attempting to identify those deposit types and general climatic conditions under which the approach appears to have potential application, especially in terrains with post-mineral cover. To date, case study results over porphyry copper and massive sulfide systems appear to yield positive geochemical patterns that effectively pinpoint the mineral system. Studies on a variety of systems, including sediment-hosted copper, Mississippi Valley lead-zinc, IOCG, roll-front and breccia-hosted uranium, and various gold systems Carlin-style, low and high sulfidation epithermal and Archean shear-hosted gold, remain in progress with results expected before the end of 2007.
This discussion will provide an overview of the GoreTM Module technology, a presentation of a couple of examples from the oil & gas sector, and a more detailed review of mineral system survey results to date.