Evolution of the northern Cordilleran miogeocline, Nahanni map area (105I), Yukon and Northwest Territories

Gordey, S P; Anderson, R G

doi:10.4095/183983

Cited by 76 publications

(152 citation statements)

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“…1). In most places, however, the inboard and outboard margins of Selwyn basin have been interpreted as facies changes [56]. How such a significant tectonic boundary could be cryptic remains unclear [54,55], but the answer may lie in resolving the significant post-150 Ma translations that have occurred within the orogen.…”

Section: Accretionary Orogensmentioning

confidence: 99%

The odyssey of the Cache Creek terrane, Canadian Cordillera: Implications for accretionary orogens, tectonic setting of Panthalassa, the Pacific superwell, and break-up of Pangea

Johnston

Borel²

2007

Earth and Planetary Science Letters

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The Cache Creek terrane (CCT) of the Canadian Cordillera consists of accreted seamounts that originated adjacent to the Tethys Ocean in the Permian. We utilize Potential Translation Path plots to place quantitative constraints on the location of the CCT seamounts through time, including limiting the regions within which accretion events occurred. We assume a starting point for the CCT seamounts in the easternmost Tethys at 280 Ma. Using reasonable translation rates (11 cm/a), accretion to the StikiniaQuesnellia oceanic arc, which occurred at about 230 Ma, took place in western Panthalassa, consistent with the mixed Tethyan fauna of the arc. Subsequent collision with a continental terrane, which occurred at about 180 Ma, took place in central Panthalassa, N 4000 km west of North America yielding a composite ribbon continent. Westward subduction of oceanic lithosphere continuous with the North American continent from 180 to 150 Ma facilitated docking of the ribbon continent with the North American plate.The paleogeographic constraints provided by the CCT indicate that much of the Canadian Cordilleran accretionary orogen is exotic. The accreting crustal block, a composite ribbon continent, grew through repeated collisional events within Panthalassa prior to docking with the North American plate. CCT's odyssey requires the presence of subduction zones within Panthalassa and indicates that the tectonic setting of the Panthalassa superocean differed substantially from the current Pacific basin, with its central spreading ridge and marginal outward dipping subduction zones. A substantial volume of oceanic lithosphere was subducted during CCT's transit of Panthalassa. Blanketing of the core by these cold oceanic slabs enhanced heat transfer out of the core into the lowermost mantle, and may have been responsible for the Cretaceous Normal Superchron, the coeval Pacific-centred mid-Cretaceous superplume event, and its lingering progeny, the Pacific Superswell. Far field tensile stress attributable to the pull of the slab subducting beneath the ribbon continent from 180 to 150 Ma instigated the opening of the Atlantic, initiating the dispersal phase of the supercontinent cycle by breaking apart Pangea. Docking of the ribbon continent with the North American plate at 150 Ma terminated the slab pull induced stress, resulting in a drastic reduction in the rate of spreading within the growing Atlantic Ocean.

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Section: Accretionary Orogensmentioning

confidence: 99%

The odyssey of the Cache Creek terrane, Canadian Cordillera: Implications for accretionary orogens, tectonic setting of Panthalassa, the Pacific superwell, and break-up of Pangea

Johnston

Borel²

2007

Earth and Planetary Science Letters

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“…3; Rainbird et al 1996). All of the metamorphic rocks in the study area belong to the greenschist or sub-greenschist facies except for contact metamorphic aureoles around Cretaceous plutons, where andalusite-bearing pelitic rocks indicate local amphibolite facies conditions (Gordey and Anderson 1993). Recognized structures include syn-sedimentary extensional faults (Aitken and Cook 1974;Eisbacher 1981;Jefferson 1983;Pyle and Jones 2009;Turner and Long 2008;Martel et al 2011) and Cretaceous-Tertiary folds and thrust faults (Morris and Nesbitt 1998;Mair et al 2006a;Pyle and Jones 2009;.…”

Section: Introductionmentioning

confidence: 95%

Metallogenic Evolution of the Mackenzie and Eastern Selwyn Mountains of Canada’s Northern Cordillera, Northwest Territories: A Compilation and Review

Ootes

Gleeson

Turner

et al. 2013

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The Mackenzie and eastern Selwyn Mountains, Northwest Territories, Canada, are the northeast expression of the Cordilleran orogen and have a geologic history that spans the last one billion years. The region has undergone a diverse tectonic evolution, which is reflected in an equally diverse collection of mineral deposits and prospects. More than 300 of these deposits and prospects have been documented in this area of the Northwest Territories and here they are categorized into mineral deposit types and their mode of formation evaluated and highlighted. Stratiform/stratabound Cu-Ag occurrences are hosted in the Neoproterozoic Coates Lake Group, generally preserved in the hanging wall of the Cretaceous Plateau fault, and define a belt through the central part of the Mackenzie Mountains. Low-grade phosphatic stratiform iron (47.5% Fe) occurs as iron formation in the Neoproterozoic Rapitan Group in the very northwest of the Mackenzie Mountains. Sedimentary exhalative Zn-Pb (± Ba) deposits are preserved in Cambrian through Devonian strata of the Selwyn Basin in the eastern Selwyn Mountains. Numerous carbonate-hosted Zn-Pb (± base-metals) occurrences are located in the Paleozoic strata of the Mackenzie Platform in the Mackenzie Mountains. Cretaceous felsic-intermediate plutons, which occur throughout the eastern Selwyn Mountains, are associated with tungsten skarn (proximal to intrusions), base-metal skarn (distal from intrusions), rare metals, semi-precious tourmaline related to pegmatites, and vein-hosted emeralds. Other resources of potential interest include coal deposits, placer gold, and possible Carlin-type gold deposits that have recently been identified farther west in the Yukon.SOMMAIRELes monts Mackenzie et ceux de la chaîne orientale de Selwyn, dans les Territoires du Nord-Ouest, au Canada, sont l'expression au nord-est de l'orogène de la Cordillère, et leur histoire géologique s’étale sur le dernier milliard d’années. La région a été l’hôte d’une évolution tectonique diversifiée, et cela se reflète par une suite tout aussi diversifiée de gisements minéraux et d’indices prometteurs. Plus de 300 de ces dépôts et indices prometteurs ont été documentées dans cette région des Territoires du Nord-Ouest, et le présent article ils sont classés en types de gîtes minéraux, et l’attention est portée sur leur mode de formation. Les gisements de Cu-Ag stratiformes ou stratoïdes sont encaissés dans le Groupe néoprotérozoïque de Coates Lake, et ils sont généralement préservés dans l'éponte supérieure de la faille du plateau crétacé, et ils forment une bande qui traverse la partie centrale des monts Mackenzie. Le fer se retrouve dans des gisements phosphatées stratiformes à faible teneur (47,5% Fe) qui provient de formations de fer dans le Groupe néoprotérozoïque de Rapitan situé dans la pointe nord-ouest des monts Mackenzie. Des gisements sédimentaires exhalatifs de Zn-Pb (± Ba) sont préservés dans des strates cambriennes à dévoniennes du bassin de Selwyn dans la portion est des monts Selwyn. De nombreux indices de Zn-Pb (± métaux communs) dans des roches carbonatées des strates paléozoïques de la plate-forme de Mackenzie, des monts Mackenzie. Des plutons felsiques intermédiaires crétacés, qui pointent tout au long de la chaîne est de Selwyn, sont associées à des skarns de tungstène (proximaux), à des skarns de métaux communs (distaux), à des concentrations de métaux rares, de tourmaline semi-précieuses liés aux pegmatites, et à des émeraudes filoniennes. Parmi d’autres ressources d'intérêt, on retrouve des gisements de charbon, d'or alluvionnaire, et d’éventuels gisements d'or de type Carlin qui ont été découverts récemment plus à l'ouest au Yukon.

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“…2). Dominant structures of the range are the Fork Anticline and the Summit Syncline, which form the major features of the Selwyn Fold Belt (Gordey & Anderson 1993). Folds trend and plunge northwest.…”

Section: Geology Of the Little Nahanni Pegmatitesmentioning

confidence: 99%

“…The Group is in the Upper Hyland Lake segment (105I/2, 1:50,000) of the Nahanni map area (105I, 1:250,000). The regional geology of the LNPG was described by Gordey & Anderson (1993), from which the following summary is adapted. From the late Precambrian to middle Devonian, a northwest-trending facies belt consisting of turbiditic sandstone, deep-water limestone, shale and chert (the Selwyn Basin) developed in the map area.…”

Section: Regional Geology and Metallogenymentioning

confidence: 99%

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Geology and Mineralogy of the Little Nahanni Rare-Element Granitic Pegmatites, Northwest Territories

Groat

Mulja²,

Mauthner

et al. 2003

The Canadian Mineralogist

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The Little Nahanni rare-element granitic pegmatite group (LNPG; ca. 82 Ma) in the western part of the Northwest Territories, occurs as subparallel dike swarms over an area of ~11 ϫ 5 km in the walls of a series of cirques dominated by schists of the Upper Proterozoic Hyland Group. These pegmatite bodies, up to a few meter wide, are divisible into spodumene-bearing and spodumenefree varieties that occur close together; some dikes split into these two variants. The two types are mineralogically similar. Both contain K-feldspar, plagioclase, quartz, mica (muscovite to lepidolite), columbite-group minerals, cassiterite, tourmaline, beryl, lithiophilite and garnet; they differ in the abundance of mica and accessory phases. The spodumene-free pegmatites have more mica, particularly lepidolite, than the spodumene-bearing variety. Apatite and montebrasite occur primarily in the former, whereas most lithiophilite is present in the latter. Sparse galena, titanian rutile, fluorite and helvite are also found in both variants. Subsolidus phases are zeolite-group minerals, microlite, and secondary phosphate minerals such as triploidite. Internal zoning in both pegmatites varies from complex to symmetrical. Where well developed, the zoning is typical from border through wall and intermediate to core zone. Quartz and the feldspars occur throughout the dikes. Micas and columbite-group minerals initially increase from the border to the wall zone and subsequently decrease toward the core, whereas tourmaline becomes less abundant toward the core. Spodumene and cassiterite first appear in the wall zone and become more abundant toward the core zone, whereas the reverse is true for beryl. 140THE CANADIAN MINERALOGIST lithiophilite in the spodumene pegmatites. Garnet remains a trace mineral in all zones, with the exception of the core zone. where it is absent. Sporadic small cavities containing quartz, K-feldspar, apatite, Mg-rich beryl, elbaite and calcite are present in some dikes. The composition of the rock-forming minerals in both types of pegmatite is similar. An example of the chemical evolution of the minerals is shown by tourmaline, which becomes richer in Al and Li, but poorer in Mg, and shows decreasing Na/(Na + vacancy) and increasing Al/(Al + Fe) values from the schist to the inner (wall + intermediate) zone of the pegmatite. These trends, together with the changes in the abundances and paragenetic sequence of the major minerals, are interpreted to reflect an increase in the Rb, Cs, Li, F, P, Be, and Ta contents, and a decrease in the contents of Mg, Fe, and B contents, in the felsic liquids during crystallization.Keywords: spodumene, lepidolite, granitic pegmatite, chemical evolution of minerals, Nahanni, Northwest Territories. SOMMAIRELe groupe de pegmatites granitiques à éléments rares de Little Nahanni (LNPG; ca. 82 Ma), situé dans le secteur ouest des Territoires du Nord-Ouest, se présente sous forme d'essaims de filons subparallèles sur une superficie d'environ 11 ϫ 5 km dans les parois de cirques, où affleu...

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Evolution of the northern Cordilleran miogeocline, Nahanni map area (105I), Yukon and Northwest Territories

Cited by 76 publications

References 0 publications

The odyssey of the Cache Creek terrane, Canadian Cordillera: Implications for accretionary orogens, tectonic setting of Panthalassa, the Pacific superwell, and break-up of Pangea

The odyssey of the Cache Creek terrane, Canadian Cordillera: Implications for accretionary orogens, tectonic setting of Panthalassa, the Pacific superwell, and break-up of Pangea

Metallogenic Evolution of the Mackenzie and Eastern Selwyn Mountains of Canada’s Northern Cordillera, Northwest Territories: A Compilation and Review

Geology and Mineralogy of the Little Nahanni Rare-Element Granitic Pegmatites, Northwest Territories

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