Mapping known and potential mineral occurrences and host rocks in the Bonnifield Mining District using minimal cloud- and snow-cover ASTER data: Chapter E in Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada--results of a 5-year projec... (original) (raw)
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Scientific Investigations Report, 2007
Cover. View of a portion of the Black Mountain tectonic zone (ridge in background) looking northeast across the Tibbs Creek drainage within the Yukon-Tanana Upland. This zone, the subject of chapter D of this report, is the locus of almost all of the mineralized base and precious metal veins in the Big Delta B-1 quadrangle. The zone is characterized by complex faulting, shearing, intrusions, and zones of gold and antimony mineralization (photograph by Larry P. Gough).
Scientific Investigations Report, 2010
Cover. View of a portion of the Black Mountain tectonic zone (ridge in background) looking northeast across the Tibbs Creek drainage within the Yukon-Tanana Upland. This zone, the subject of chapter D of this report, is the locus of almost all of the mineralized base and precious metal veins in the Big Delta B-1 quadrangle. The zone is characterized by complex faulting, shearing, intrusions, and zones of gold and antimony mineralization (photograph by Larry P. Gough).
Tintina Gold Province Study, Alaska and Yukon Territory, 2002-2007
Fact Sheet, 2007
The Tintina gold province is an arc-shaped 2,000-kilometer-long metallogenic province that extends from northern British Columbia, through the Yukon Territory, and across and into southwestern Alaska. In the United States, the province remains a prime area for gold exploration and includes such large gold deposits as Pogo, Fort Knox-True North, and Donlin Creek. In recent years, gold exploration and development and mining activity have accelerated in the area. Plans have been discussed for public and private projects and infrastructures associated with development. A U.S. Geological Survey study undertaken from 2002 to 2007 provides a context for understanding why and how the mineral resources of the area were formed, why this area is so abundantly endowed, and how the environmental signatures that are characteristic of the area are related to the development of mineral resources. Characterization of natural baseline metal concentrations in the area's watersheds is necessary to address future land-use issues related to mining and/or infrastructure activities. A thorough understanding of water-rock and elementbioavailability processes will help predict the possible environmental impact of development. The five tasks of this study add to the science of defining and understanding an "intrusion-related gold system."
Yukon exploration and …, 1998
Auriferous sheeted quartz veins and silicified shear zones occur along the margins and within adjacent hornfels zones of mid-Cretaceous Tombstone intrusions near the head of Clear Creek in the central Yukon. The lodes are the source for more than 120,000 ounces of downstream placer gold production. These lodes contain variable amounts pyrrhotite, pyrite, and arsenopyrite, with less abundant scheelite-alkali-feldspar, muscovite, biotite and tourmaline are common gangue phases. Grab samples of mineralization often contain gold grades in excess of 1 ounce per ton. Gold-to-silver ratios vary most commonly from 1:1 to 5:1. Gold-rich quartz veins cut all stocks, adjacent hornfels and associated lamprophyre dykes commonly contain greater than 1% arsenic. Bismuth, and less consistently tungsten and stibnite, characterize many of the most highly mineralized veins within and surrounding the stocks. Quartz veins along the intrusivemetasedimentary rock contact around the Pukelman stock are also enriched in lead and silver. R-mode factor analysis of multi-element geochemical data for 111 gold-and sulphide-bearing rock samples indicates that there are two geochemically distinct metal suites in the Clear Creek occurrences. The first is characterized by As-Au-Bi ± Sb, Te ore-related mineral association, which is typical of many intrusion-related deposits in the Tombstone gold belt. Less consistently, anomalous concentrations of Ag, Co, Cu, Fe, and Mo occur within these auriferous rocks. The second metal factor is defined by Ag-Bi-Pb ± As, Au and Te. It characterizes metalliferous vein samples that have uncommonly low Au:Ag ratios and may represent a second hydrothermal episode. Tungsten shows little consistent correlation with the metalliferous veins in either element suite. RÉSUMÉ Des filons de quartz aurifère stratifiés et des zones de cisaillement silicifiées sont présents le long des bordures et dans les zones à cornéennes adjacentes de six amas intrusifs situés à proximité de la source du ruisseau Clear (115P/14). Ces amas font partie de la ceinture de Tombstone de 91Å0,5 Ma et leur composition va de la monzonite quartzifère à la diorite. Ils sont recoupés par des dykes d'aplite et de lamprophyre tardifs et pénètrent des roches clastiques du faciès des schistes verts inférieur à granulométrie fine du Groupe de Hyland d'âge s'échelonnant du Néo-protérozoïque au Cambrien précoce. Les plutons et les dykes se rencontrent de façon constante le long de structures d'extension orientées est-ouest. Les filons et les zones de cisaillement minéralisées ont produit 120 000 oz d'or alluvionnaire en aval. Ces filons contiennent généralement de la pyrrhotite, de la pyrite, de la scheelite et de l'arsenopyrite en abondance. Les minéraux de gangue fréquents sont le feldspath potassique, la muscovite et la tourmaline. De nombreux indices minéralisés à forte teneur en or sont associés dans l'espace avec des cornéennes à forte teneur en biotite dans des roches clastiques, avec des zones de greisen dans des granitoïdes et avec de petites zones de skarn à tungstène dans des roches calcaires.
Ore Geology Reviews, 2017
Recently discovered gold-rich mineral deposits in the eastern Nadaleen trend of northeastern Yukon Territory occur in unmetamorphosed Neoproterozoic carbonate and siliciclastic rocks and their location is partly controlled by structures. Regional deformation largely resulted from mid-Cretaceous NNE-vergent, thinskinned fold-thrust activity. However, structures in the eastern Nadaleen trend are more complex and include strikeslip and reverse faults, and SSW-, Wand nd E-plunging folds. Local structures are cospatial with regional geologic features, including (1) an E-striking structural triangle zone defined by oppositely dipping reverse faults that verge toward the eastern Nadaleen trend, (2) a transition zone between Paleozoic Ogilvie platform rocks in the north to Selwyn basin rocks in the south, and (3) a change in regional deformation character from west to east, whereby to the west, rocks in the south are more deformed than rocks in the north, whereas to the east, rocks show no obvious change in deformation style. The structural complexity within the eastern Nadaleen trend probably resulted from these regional geological features and was further complicated by local competency contrasts between rock units. The cospatial location of the regional geological features may have been caused by a pre-existing, W-trending subsurface basement structure. Reverse faults bounding the E-striking triangle zone may have acted as low permeability aquitards that directed mineralizing fluids up-dip into reactive carbonate stratigraphy in the eastern Nadaleen trend. Gold-rich mineral deposits in the eastern Nadaleen trend occur preferentially in SSW-plunging anticlines and near faults, both of which probably influenced the migration of mineralizing fluid.