The geology of the Abiete-Toko gold district in South Cameroon is investigated using a combination of Landsat 7 ETM+/SRTM image processing techniques, conventional geologic field mapping and geostatistical analysis. The satellite images were treated using Principal Component Analysis and Sobel filters to separate the background noise from lithotectonic structures which were matched with field data. The results show that this area has been affected by a polyphase deformation represented by S 1 foliation, S c1 schistosity, L 1 lineation, S 2 foliation, F 2 folds, and F 3 shear zones and faults. A detailed analysis of all the structures led to the identification of two major networks of dextral and sinistral shear zones oriented WNW-ESE and NE-SW, respectively. These results may serve in mining prospection, especially in the search for tectonically controlled primary mineralization and so may significantly guide the exploration of primary gold mineralization in the Abiete-Toko area subjected to years of artisanal gold mining.

To decipher the thermal history of mineralized systems across the Freegold Mountain area (Yukon, Canada), a combined geochronology (zircon U-Pb and hornblende, biotite, and whole rock Ar-Ar) and thermochronology (apatite and zircon (U-Th)/He) study was carried out. Previous U-Pb data combined with new U-Pb and Ar-Ar data show that intrusive bodies across the Freegold Mountain were emplaced during two protracted episodes, the first spanning from 109.6 to 98 Ma and the second between 79 and 68 Ma. Overprinting of the first intrusive event by a second magmatic hydrothermal event is suggested by a zircon U-Pb age of 108.7 ± 0.4 Ma for a chlorite-altered dyke and a whole rock Ar-Ar plateau age of 76.25 ± 0.53 Ma. Zircon (U-Th)/He data are between 66 and 89 Ma, whereas apatite (U-Th)/He data are scattered (38.7-109.9 Ma) and bracket the two magmatic emplacement events. Our combined data reveal a complex history of reheating that led to resetting of numerous chronometers. In most of the investigated magmatic hydrothermal systems, early fast cooling from igneous emplacement through hydrothermal alteration (between 900 and 200°C) was followed by later and slower cooling accompanying post mineralization uplift and erosion (between 200 and 70°C). Preliminary models indicate intrusive bodies associated with the Stoddart Cu-Mo ± W prospect cooled slowly (23°C/Ma) compared with the ones spatially associated with the Revenue Au-Cu prospect (43°C/Ma), and the similarity of the zircon U-Pb and (U-Th)/He ages from Revenue dyke further supports a rapid cooling from 700 to 180°C. Erosion rates of 0.035-0.045 mm/year are consistent with tectonic quiescence during the Late Tertiary combined with the lack of Pleistocene glaciation in central Yukon. Such low rates of exhumation favour the formation and preservation of supergene mineralization, such as that found north of Freegold Mountain. Résumé : Afin de pouvoir décoder l'historique thermique des systèmes minéralisés à travers le secteur du mont Freegold (Yukon, Canada), une étude combinée de géochronologie (U-Pb sur zircon et Ar-Ar sur hornblende, biotite et la roche entière) et de thermochronologie (apatite et zircon (U-Th)/He) a été entreprise. Les données antérieures U-Pb, combinées aux nouvelles données U-Pb et Ar-Ar montrent que des amas intrusifs ont été mis en place au mont Freegold au cours de deux épisodes prolongés, le premier de 109,6 à 98 Ma et l'autre entre 79 et 68 Ma. Une surimpression du premier événement intrusif par un autre événement magmatique hydrothermal est suggérée par une datation U-Pb sur zircon, de 108,7 ± 0,4 Ma, pour un dyke altéré par de la chlorite; aussi, un âge plateau Ar-Ar, pour la roche entière, donne 76,25 ± 0,53 Ma. Des données (U-Th)/He pour le zircon varient entre 66 et 89 Ma alors que des données (U-Th)/He pour l'apatite sont plus dispersées (entre 38,7 et 109,9 Ma) et encadrent les deux événements magmatiques de mise en place. Nos données combinées révèlent un historique complexe de réchauffements qui ont conduit au rajustement de nombreux ch...

No abstract

No abstract

No abstract