“Antler” elastics in the Canadian Cordillera

Gordey, S P; Abbott, J G; Tempelman-Kluit, D J; Gabrielse, H

doi:10.1130/0091-7613(1987)15<103:aeitcc>2.0.co;2

Cited by 46 publications

(31 citation statements)

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“…Although the form of the subsidence curves from sections within the carbonate bank facies of the miogeocline indicates a characteristic passive-margin subsidence, geologic relations farther to the west, in the preserved outer portions of the ancient passive margin, suggest intermittent tectonic activity throughout the Paleozoic. Such tectonic activity has been attributed to continued extensional tectonism (D. Klepacki, personal communication, 1986), possibly related to a broad zone of transform faulting (Eisbacher 1983;Gordey et al 1987). A possible counterpart to the early Paleozoic margin of North America has yet to be identified, and it is important to note that the subsidence analyses do not distinguish between thermal subsidence of a passive-margin sequence that formed in response to fragmentation of a major continental plate, the rifting of a continental fragment, or an island arc (Bond et al 1985; Devlin 1986).…”

Section: Discussionmentioning

confidence: 96%

The initiation of the early Paleozoic Cordilleran miogeocline: evidence from the uppermost Proterozoic – Lower Cambrian Hamill Group of southeastern British Columbia

Devlin¹,

Bond²

1988

Can. J. Earth Sci.

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The uppermost Proterozoic -Lower Cambrian Hamill Group of southeastern British Columbia contains geologic evidence for a phase of extensional tectonism that led directly to the onset of thermally controlled subsidence in the Cordilleran miogeocline. Moreover, the Harnill Group contains the sedimentological record of the passage of the ancient passive margin from unstable tectonic conditions associated with rifting and (or) the earliest phases of thermal subsidence to post-rift conditions characterized by stabilization of the margin and dissipation of the thermal anomaly generated during the rift phase (the rift to post-rift transition). Widespread uplift that occurred prior to and during the deposition of the lower Hamill Group is indicated by an unconformable relation with the underlying Windermere Supergroup and by stratigraphic relations between Middle and Upper Proterozoic strata and unconformably overlying upper Lower Cambrian quartz arenites (upper Hamill Group) in the southern borderlands of the Hamill basin. In addition, the coarse grain size, the feldspar content, the depositional setting, and the inferred provenance of the lower Hamill Group are all indicative of the activation of basement sources along the margins of the Hamill basin. Geologic relations within the Hamill Group that provide direct evidence for extensional tectonism include the occurrence of thick sequences of mafic metavolcanics and rapid vertical facies changes that are suggestive of syndepositional tectonism.Evidence of extensional tectonism in the Hamill Group directly supports inferences derived from tectonic subsidence analyses that indicate the rift phase that immediately preceded early Paleozoic post-rift cooling could not have occurred more than 10-20 Ma prior to 575 + 25 Ma. These data, together with recently reported isotopic data that suggest deposition of the Windermere Supergroup began -730-770 Ma, indicate that the rift-like deposits of the Windermere Supergroup are too old to represent the rifting that led directly to the deposition of the Cambro-Ordovician post-rift strata. Instead, Windermere sedimentation was apparently initiated by an earlier rift event, probably of regional extent, that was part of a protracted, episodic rift history that culminated with continental breakup in the latest Proterozoic -Early Cambrian.Le Groupe de Hamill, d'lge prottrozoique tardif -cambrien hltif, dans le sud-est de la Colombie-Britannique, exhibe des phtnomtnes gtologiques qui ttmoignent en faveur d'une phase de tectonisme d'extension qui serait directement responsable du dtmarrage d'une subsidence, crontr6lte par des conditions thermiques, dans le miogtoclinal de la Cordilltre. En outre, les sediments du Groupe de Hamill portent les marques de la transition d'une ancienne marge passive a des conditions tectoniques instables associks a la formation d'un rift et (ou) de phases pkcoces de subsidence thermique passant ?I des conditions postrift caractCrisCes par une stabilisation de la marge et une dissipation de l'anomalie thermique e n...

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Section: Discussionmentioning

confidence: 96%

The initiation of the early Paleozoic Cordilleran miogeocline: evidence from the uppermost Proterozoic – Lower Cambrian Hamill Group of southeastern British Columbia

Devlin¹,

Bond²

1988

Can. J. Earth Sci.

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“…19; Gordey et al, 1987;Goodfellow et al, 1995;Paradis et al, 1998). This arc and continent rifting started at 365 to 360 Ma (e.g., Nelson, 1993;Dusel-Bacon et al, 2004;Piercey et al, 2004) and continued after the Wolverine deposit formed as the Slide Mountain back-arc basin widened (e.g., Nelson, 1993;Nelson et al, 2006;Piercey et al, 2006).…”

Section: Regional Implicationsmentioning

confidence: 95%

Petrology and U-Pb Geochronology of Footwall Porphyritic Rhyolites from the Wolverine Volcanogenic Massive Sulfide Deposit, Yukon, Canada: Implications for the Genesis of Massive Sulfide Deposits in Continental Margin Environments

Piercey¹,

Peter²,

Mortensen³

et al. 2008

Economic Geology

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Porphyritic rhyolite sills form an important component of the footwall of the Wolverine volcanogenic massive sulfide (VMS) deposit, Yukon, Canada, and occur proximal to mineralization in the immediate deposit area (Wolverine/Lynx zone) and at similar stratigraphic levels along strike (Fisher, Puck, and Sable zones). Porphyritic rhyolites are of two types: an older quartz-feldspar porphyritic (QFP) rhyolite suite; and a younger feldspar porphyritic (FP) suite. Both the QFP and FP suites of intrusions are semiconcordant, suggesting a silllike morphology, and are altered and crosscut by veinlet mineralization, suggesting that they are pre-to synmineralization. The margins of QFP suite of intrusions contain minor xenoliths of surrounding shales and poorly developed chilled margins suggesting emplacement into partially consolidated sedimentary rocks, whereas the FP suite of intrusions shows well-developed chilled margins indicative of emplacement into fully solidified sedimentary rock. These features suggest that the QFP suite of intrusions represents an older phase of rhyolitic magmatism, whereas the FP suite represents a younger event. This is supported by U-Pb zircon ages, which indicate a 352.4 ± 1.5 Ma emplacement age for the FP suite and a ~347 to 346 Ma emplacement for the FP suite (two ages at 347.8 ± 1.3 and 346.0 ± 2.2 Ma). Both suites of porphyries have inherited Proterozoic zircon and have ratios of La/SmUCN~1 and Nb/ThUCN~1 (UCN -upper continental crust normalized), indicating derivation from and/or extensive interaction with ancient upper continental crustal materials. The FP suite, however, has elevated high field strength element (HFSE) and rare earth element (REE) contents, high zircon saturation temperatures, and higher Nb/Ta ratios and lower Ti/Sc ratios than the QFP suite. These features are interpreted to reflect that the FP suite of magmas was hotter (>900°C) melts with a greater mantle component in their genesis. Both suites, however, are interpreted to have formed due to basaltic upwelling, crustal melting, and crust-mantle mixing during ensialic back-arc basin activity. The presence of mantle heat within the Wolverine basin from ~352 to ~347 to 346 Ma, a minimum of 5 m.y., suggests that sustained mantle heat flow was critical to the genesis of the Wolverine porphyries. It is also suggested that this sustained mantle heat was responsible for the Wolverine hydrothermal system and that upwelling mantle may be essential in providing the heat to drive hydrothermal systems even in continental margin-type VMS environments (e.g., Bathurst, Iberian pyrite belt).The Wolverine porphyries are among the most HFSE-and REE-enriched felsic rocks associated with VMS mineralization globally. The high HFSE and REE concentrations in these rocks are interpreted to be due to

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“…Some studies (e.g., Dusel- Bacon and Aleinikoff, 1985;Nokleberg and Aleinikoff, 1985;Rubin et al, 1990;Mortensen, 1992) suggested that the Late Devonian to Early Mississippian metaigneous rocks of the Yukon-Tanana terrane represent a continental magmatic arc. Other investigations interpreted these magmatic belts to have formed in an extensional environment, either due to rifting (Tempelman-Kluit, 1976;Duke et al, 1984;Gordey et al, 1987;Hansen et al, 1991;Hudson, 1994;Hansen and Dusel-Bacon, 1998;Dusel-Bacon and Cooper, 1999), large-scale strike-slip faulting (Eisbacher, 1983), or fl exural extension in the foreland of a contractional orogen (Smith et al, 1993). Newberry et al (1997) concluded that most Alaskan VMS deposits of Devonian-Mississippian age are hosted in felsic metavolcanic rocks that are part of bimodal volcanic suites in which associated intermediate-composition rocks are rare, thus suggesting a rift setting.…”

Section: Introductionmentioning

confidence: 99%

U-Pb zircon and geochemical evidence for bimodal mid-Paleozoic magmatism and syngenetic base-metal mineralization in the Yukon-Tanana terrane, Alaska

Dusel-Bacon

Wooden

Hopkins

2004

Geol Soc America Bull

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New SHRIMP (sensitive, high-resolution ion microprobe) U-Pb zircon ages and trace element geochemical data for mafi c and felsic metaigneous rocks of the pericratonic Yukon-Tanana terrane in east-central Alaska help defi ne the tectonic setting of mid-Paleozoic magmatism and syngenetic hydrothermal Zn-Pb-Ag mineralization along the ancient Pacifi c margin of North America. We compare data from similar greenschist-facies sequences of bimodal volcanic and subvolcanic rocks associated with carbonaceous and siliciclastic marine sedimentary rocks, in the Wood River area of the Alaska Range and the Salcha River area of the Yukon-Tanana Upland, and from amphibolite-facies augen gneiss and mafi c gneiss (amphibolite) in the Goodpaster River area of the upland. Allowing for analytical uncertainties, igneous crystallization age ranges of 376-353 Ma, 378-346 Ma, and 374-358 Ma are indicated by 13 new SHRIMP U-Pb dates for the Wood River, Salcha River, and Goodpaster River areas, respectively. Bimodal magmatism is indicated by Late Devonian crystallization ages for both augen gneiss (371 ± 3 and 362 ± 4 Ma) and associated orthoamphibolite (369 ± 3 Ma) in the upland and by stratigraphic interleaving of mafi c and felsic rocks in the Alaska Range. Metabasites in all three study areas have elevated HFSE (high fi eld strength element) and REE (rare earth element) contents indicative of generation in a within-plate (extensional) tectonic setting. Within-plate trace element signatures also are indicated for peralkaline metarhyolites that host the largest volcanogenic massive sulfi de deposits of the Bonnifi eld district in the Wood River area and for metarhyolite tuff interlayered with the carbonaceous Nasina assemblage, which hosts sedimentary exhalative sulfi de occurrences in the Salcha River area. Most of the other felsic metaigneous samples from the Alaska Range and the Yukon-Tanana Upland have geochemical signatures that are similar to those of both average upper continental crust and continental-margin arc rocks generated in thick continental crust. Given the absence in our study areas of intermediate-composition magmatic products generally found in most arcs, and the presence of bimodal magmatism, the alkalic within-plate chemistry of the mafi c rocks and some of the felsic rocks, and the widespread occurrence of interlayered carbonaceous sedimentary rocks indicative of deposition within a restricted marine basin or submerged continental margin, we consider it most likely that this prolonged Late Devonian to Early Mississippian magmatic episode resulted from attenuation of the ancient continental margin of western North America, rather than development of an arc, as proposed by many others.

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“Antler” elastics in the Canadian Cordillera

Cited by 46 publications

References 0 publications

The initiation of the early Paleozoic Cordilleran miogeocline: evidence from the uppermost Proterozoic – Lower Cambrian Hamill Group of southeastern British Columbia

The initiation of the early Paleozoic Cordilleran miogeocline: evidence from the uppermost Proterozoic – Lower Cambrian Hamill Group of southeastern British Columbia

Petrology and U-Pb Geochronology of Footwall Porphyritic Rhyolites from the Wolverine Volcanogenic Massive Sulfide Deposit, Yukon, Canada: Implications for the Genesis of Massive Sulfide Deposits in Continental Margin Environments

U-Pb zircon and geochemical evidence for bimodal mid-Paleozoic magmatism and syngenetic base-metal mineralization in the Yukon-Tanana terrane, Alaska

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