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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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Africa
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Central Africa
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Congo Democratic Republic (1)
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Reguibat Ridge (1)
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Southern Africa
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Primary terms
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Africa
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Central Africa
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Congo Democratic Republic (1)
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Reguibat Ridge (1)
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Southern Africa
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South Africa
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Witwatersrand (2)
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West Africa
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Burkina Faso (3)
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Ghana (7)
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Guinea (2)
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Liberia (2)
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Mali (2)
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Niger (1)
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Senegal (2)
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West African Craton (3)
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Asia
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Baikal Mountains (1)
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Baikal region (1)
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Sayan (1)
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Siberian fold belt (1)
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Tien Shan (1)
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Australasia
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Australia
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Northern Territory Australia
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Pine Creek Geosyncline (1)
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Western Australia
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Capricorn Orogen (1)
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Damang Deposit
Exhumation-Driven Devolatilization as a Fluid Source for Orogenic Gold Mineralization at the Damang Deposit, Ghana
Abstract Gold mineralization at the Damang deposit is unique among known deposits in Ghana, comprising two distinct styles of mineralization. These include a stratigraphically controlled auriferous quartz-pebble metaconglomerate that is overprinted by later gold contained in a complex fault-fracture vein array with surrounding hydrothermal alteration. A systematic study using portable, field-based infrared reflectance spectroscopy has proven to be a valuable exploration tool at Damang. Spectral parameters such as the ferrous-iron response, the AlOH/H 2 O absorption depth ratio, and automated mineral identification successfully distinguish metasedimentary and metadoleritic lithologic units at Damang. Systematic variations in these parameters, together with the water/OH absorption depth, both downhole and in three-dimensional models, provide vectors to gold mineralization. The spectral parameters AlOH wavelength and MgOH wavelength are used to define the regolith profile at Damang, throughout which the ferrous-iron response parameter provides a reliable indicator of gold mineralization. All recorded changes in spectral parameters can be linked to sample petrography and are supported by mineral-chemical data. These results show that portable infrared spectroscopy can be used in a variety of roles, including regolith mapping, geologic mapping and logging, and recognition of hydrothermal alteration patterns, as each lithology and alteration style exhibit distinct and identifiable spectral characteristics. These spectrally derived alteration proxies indentify a broader zone of potential gold mineralization than gold grades alone, providing a larger target for exploration. The rapidity of data collection and ease of analysis of spectral data make infrared reflectance spectroscopy a useful methodology that can be readily incorporated into both preexisting and established exploration programs in other tropical terrains.
Simplified geologic maps of the Birimian terrane of Ghana and the Damang ar...
A, B, and C. Photographs of the Wassa deposit (modified from Perrouty et a...
Re-Os Geochronological Evidence for Multiple Paleoproterozoic Gold Events at the Scale of the West African Craton
West Africa: The World’s Premier Paleoproterozoic Gold Province
Simplified geologic map of the West African craton, showing locations of th...
Gold Deposits of the Birimian and Tarkwaian in Ghana
Student Field Trip 17 visited a number of paleoplacer and orogenic gold deposits throughout southwest Ghana over a week. The itinerary and route map include visits to active open-pit and underground operations, including Damang, Iduapriem, Nkran/Esaase, Obuasi, Prestea-Bogosu, and Wassa, as well as exploration projects at Homase-Akrokerri, all hosted within the Birimian Supergroup. The course material covers the geology and mineralization of these deposits in the context of regional and local geological settings, focusing on their similarities and differences, ore resources, deposit models, and exploration methods.
Student Field Trip 17 visited a number of paleoplacer and orogenic gold deposits throughout southwest Ghana over a week. The itinerary and route map include visits to active open-pit and underground operations, including Damang, Iduapriem, Nkran/Esaase, Obuasi, Prestea-Bogosu, and Wassa, as well as exploration projects at Homase-Akrokerri, all hosted within the Birimian Supergroup. The course material covers the geology and mineralization of these deposits in the context of regional and local geological settings, focusing on their similarities and differences, ore resources, deposit models, and exploration methods.
Grade-tonnage diagram for West African orogenic Au deposit resources; the o...
Back-scattered electron microscope images of hydrothermal xenotime. (A) Xen...
Hydrothermal Monazite and Xenotime Geochronology: A New Direction for Precise Dating of Orogenic Gold Mineralization
Evidence for Two Stages of Mineralization in West Africa’s Largest Gold Deposit: Obuasi, Ghana
Abstract Paleoproterozoic terranes of the Man-Leo Shield in the southern part of the West African craton host one of the world’s largest gold provinces with an overall endowment >10,000 metric tons (t). Although gold deposition commenced by ca. 2170 Ma, most deposits formed later, either during the inversion and metamorphism of intraorogenic sedimentary basins between ca. 2110 and 2095 Ma, or during later transcurrent deformation and associated widespread high K plutonism following docking of Archean and Paleoproterozoic domains within the craton at ca. 2095 Ma. Deposits formed between ca. 2110 and 2095 Ma include those with free gold in quartz veins and refractory gold in arsenopyrite and/or pyrite, and are associated with halos of carbonate, sericite, chlorite, and albite alteration. Most are located in bends and intersections between shear zones, minor faults, folds, and entrained blocks of relatively reactive igneous rock. Conglomerate-hosted gold deposits of the Tarkwa district formed early in the 15-m.y.-long period. Gold deposits that formed subsequently between ca. 2095 and 2060 Ma have a wider variety of styles, geologic settings, and metal assemblages. District-scale albite, carbonate, and tourmaline alteration, hydrothermal breccias, and a close relationship to high K granitoids characterize some of these deposits, whereas others are more typical orogenic gold deposits that are similar to those formed earlier during the craton evolution.