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EXPLORATION AND MNING GEOLOGY JOURNAL EMG Archean and Paleoproterozoic Geology and Metallogeny of the Southern Canadian Shield Characterization of Mineralization in the Sullivan-North Star Corridor and Enhanced Exploration for Other Mineral Deposits in the Purcell Basin, Southeastern British Columbia: Application of High-resolution Airborne Geophysics Contrasting Styles of Gold Mineralization along the Grand Pabos-Restigouche Fault System: Implication for Carlin-like Au-mineralization in the Southwestern Gaspé Appalachians The Specogna gold deposit: A Late Tertiary, low-sulfidation epithermal hot spring deposit, Graham Island, Queen Charlotte Islands, British Columbia, Canada
K. HOWARD POULSEN Abstract — The Archean Superior Province craton and the Paleoproterozoic Penokean Orogen are major geological sub-divisions of the southern Canadian Shield and account for much of the metallic mineral production of North America. The Superior Province experienced a mainly Archean history involving several cycles of volcanism, plutonism, and tectonism, primarily in the Neo-archean but also including Meso-archean and Paleo-archean cycles as well. Superior Province consists of northern and southern high-grade gneiss sub-provinces and a broad central region of alternating greenstone-granite and metasedimentary belts. The sub-provinces may represent tectonic terranes assembled in the Archean by accretion processes similar to those of some Phanerozoic orogens. Most of the mineral deposits, including VMS, intrusion-related, and lode gold deposits occur in the greenstone-granite sub-provinces where they were formed in an interval of 100 million years or less around 2.7 Ga. The Paleoproterozoic Penokean Orogen comprises supracrustal sequences deposited in fault-controlled epicratonic and rifted margin settings developed on and about the Superior craton. Deposition of the ~2.4 Ga Huronian Supergroup and its paleoplacer uranium deposits in the eastern Penokean Orogen, and their pre-2.2 Ga deformation, were probably unrelated to the deposition of the ~2.1 Ga Marquette Range and Animikie groups and their major taconite iron formations in the west. However, these sequences were deformed together during the ~1.85 Ga Penokean Orogeny which resulted when an assembly of island arcs containing VMS deposits, the Wisconsin magmatic terrane, collided with the Superior block and its Paleoproterozoic cover. The Sudbury structure with its world class Ni-Cu-PGE ores was also formed at this time, possibly triggered by meteorite impact. Metallogenic patterns in the Paleoproterozoic rocks were controlled by a complex interplay of factors including tectonically controlled variations in deposition and deformation, distribution of mineralization in the Archean basement, and oxyatmoversion, the transition from anoxic to oxygenic atmospheric conditions that occurred during the deposition of these sequences. © 1999 Canadian Institute of Mining, Metallurgy and Petroleum. All rights reserved.
Characterization of Mineralization in the Sullivan-North Star Corridor and Enhanced Exploration for Other Mineral Deposits in the Purcell Basin, Southeastern British Columbia: Application of High-resolution Airborne Geophysics
Contrasting Styles of Gold Mineralization along the Grand Pabos-Restigouche Fault System: Implication for Carlin-like Au-mineralization in the Southwestern Gaspé Appalachians Abstract — In the southern Gaspé Appalachians, gold mineralization is spatially associated with the Acadian dextral strike-slip Grand Pabos-Restigouche fault system. Two different structurally-controlled gold prospects, the Lac Arsenault and the Saint-André-de-Ristigouche, are described to unravel the genesis of gold mineralization in this part of the Canadian Appalachians. The Sb-Au-As mineralization of the Saint-André-de-Ristigouche gold prospect, in the southwestern Gaspé area, comprises extension veins in the extension direction emplaced in brittle conditions. Mineralized veins are hosted by calcilutite and laminated silty and argillaceous limestone of the Early Silurian part of the White Head Formation, which belongs to the Gaspé Belt, the Middle Paleozoic successor basin in the Gaspé Appalachians. Metamorphic grade of the White Head Formation in the southwestern Gaspé area is very low, but the gold mineralization is included in a zone of hydrothermal propylitic alteration which includes two Cu-skarn mineral occurrences. The Lac Arsenault gold prospect has many characteristics of “greenstone-hosted quartz-carbonate vein” deposits whereas the southwestern Gaspé area, which includes the Saint-André-de-Ristigouche gold prospect, shows affinities with the geological setting of sediment-hosted gold deposits (Carlin-like deposits). The two gold prospects are controlled by the Grand Pabos-Restigouche fault system but they were not emplaced at the same level in the crust. Acadian strike-slip fauting played a major role in their respective genesis in providing channelways for ore-bearing fluids. The recognition of the analogy of the geological setting of the southwestern Gaspé area with that of Carlin-like mineralization gives new ideas for exploration in the area and elsewhere in the Appalachians. Dans le sud-ouest de la Gaspésie, la minéralisation à Sb-Au-As de Saint-André-de-Ristigouche est dans des veines d’extension comprises dans la direction d’extension et mises en place dans des conditions de déformation fragile. Les veines minéralisées sont encaissées dans les calcaires argileux et les calcilutites de la partie silurienne de la Formation de White Head qui appartient à la ceinture de Gaspé, le bassin successeur du Paléozoïque moyen des Appalaches de la Gaspésie. Le degré métamorphique des roches du White Head est très bas, mais les veines aurifères sont incluses dans de larges zones d’altération hydrothermale propylitique qui comprennent deux indices de skarns cuprifères. L’indice du Lac Arsenault a plusieurs caractéristiques des gîtes du type greenstone-hosted quartz-carbonate vein, tandis que l’environnement géologique régional du sud-ouest de la Gaspésie avec l’indice de Saint-André-de-Ristigouche montre des affinités avec les gîtes de type sediment-hosted gold deposit (Carlin-like deposit). Les deux indices d’or sont contrôlés par le système de failles de Grand Pabos-Restigouche mais ne se sont pas mis en place à la même profondeur dans la croûte terrestre. Les failles de coulissage acadiennes ont joué un rôle majeur dans la genèse respective de chaque indice en fournissant des conduits pour la migration des fluides hydrothermaux minéralisateurs. La reconnaissance d’une analogie entre le cadre géologique du sud-ouest de la Gaspésie avec celui des gîtes d’or de type Carlin donne de nouvelles idées pour l’exporation en Gaspésie et ailleurs dans les Appalaches. © 1999 Canadian Institute of Mining, Metallurgy and Petroleum. All rights reserved.
The Specogna Gold Deposit: A Late Tertiary, Low-sulfidation Epithermal Hot Spring Deposit, Graham Island, Queen Charlotte Islands, British Columbia, Canada Abstract — Two examples are used to describe how geological features impact on the development of semi-variogram models to be used for geostatistical resource/reserve estimation of porphyry-type deposits. In the Main zone of the Huckleberry porphyry copper deposit, mineralization is concentrated in fracture zones localized in volcanic rocks, along the eastern and southern margins of a granitic stock. Mineralized volcanic rocks can be subdivided into three separate domains, each with its own preferred direction of mineralization that is reflected in contoured Cu diagrams and semi-variograms. The East zone at Huckleberry deposit, spatially distinct from the Main zone, is controlled by a fracture zone elongate roughly east-westerly and bounded on the south by a major fault (easterly striking and steeply dipping) across which there is a dramatic drop in grades. The eastern part of the East zone appears to be coaxial with a large intrusive body; the western part contains a small, elongate dike-like intrusion. Contoured Cu values for many levels suggest that the principal direction of geological elongation of the east and west domains of the East zone differs significantly. Independently derived semi-variogram models for each domain are different and reflect this difference in trend. In both Main and East zones of the Huckleberry deposit, block estimates by ordinary kriging are significantly different using a domain-specific semi-variogram model than using a deposit-general semi-variogram model. The domain-specific estimates are deemed better because they are based on local controls of mineralization and have less conditional bias than those generated by the deposit-general semi-variogram model. © 1999 Canadian Institute of Mining, Metallurgy and Petroleum. All rights reserved. Last updated: |
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