Large-scale coast-parallel displacements in the Cordillera: a granitic resolution to a paleomagnetic dilemma

Johnston, Stephen T.

doi:10.1016/s0191-8141(99)00015-2

Cited by 17 publications

(9 citation statements)

References 12 publications

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“…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. Paleomagnetic data implies that large portions of the orogen underwent significant midCretaceous southerly displacements [57], coeval with fold and thrust belt formation within the foreland, widespread dextral strike-slip faulting and voluminous granitic magmatism as far inboard as the eastern limit of Selwyn basin [58]. Paleomagnetic data from Late Cretaceous strata require significant northward translations, relative to the autochthon [59,60] coeval with fold and thrust belt formation in the foreland and oroclinal buckling of the ribbon continent in Alaska [55].…”

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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“…Hamilton, 1994; Smellie, 1994). More recently, many structural geologists have recognized from strong field evidence that some magma intrusions have occurred directly along coeval regional strike‐slip faults (Jacques and Reavy, 1994; Johnston, 1999; Olivier et al ., 1999) or associated with block‐rotation along strike‐slip faults (Marra, 2001). At the same time, transcurrent tectonics guiding the location of volcanic centres has been assessed based on strike‐slip faults aligned with, or close to, coeval volcanoes (DeBeoer et al ., 1980; Bahar and Girod, 1983; Harmand and Moukadiri, 1986; Kozhurin, 1990; Tibaldi, 1992; Marinoni and Pasquarè, 1994; Lavenu and Cembrano, 1999).…”

Section: Introductionmentioning

confidence: 99%

Do transcurrent faults guide volcano growth? The case of NW Bicol Volcanic Arc, Luzon, Philippines

Pasquarè

Tibaldi

2003

Terra Nova

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This paper shows that although volcanoes can be aligned along transcurrent faults, their growth can in reality be controlled by secondary structures that have a different orientation and kinematics. Assessing the relationships between local structures and volcano growth can be very useful for the evaluation of volcanic hazards and for economic purposes such as geothermal and hydrogeological exploration. In the north‐western Bicol Volcanic Arc (Luzon, Philippines) the Quaternary Labo and Caayunan volcanoes are aligned with the NW‐striking transcurrent Philippine Fault System. They are exceptional examples of composite volcanoes mostly comprising lava domes, where regional tectonic structures and hydraulic radial fracturing have alternated to control volcano growth. Field data and analogue modelling demonstrate that apical depressions affecting the domes reflect the geometry of magma‐feeding fractures. These data, together with alignments of domes and hot springs and other structural information, suggest that magma rose at depth along the NW‐striking transcurrent faults, but that in the uppermost crust magma rose along NE‐striking fractures parallel to the greatest principal stress.

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“…2A). It is a westnorthwest-trending, dextral strike-slip fault characterized by fractured, brecciated, and mylonitized rock that extends >300 km across central west Yukon (Johnston 1999). The BCF extends across the Freegold Mountain area, cuts the DRB, and is unconformably overlain by and predates Upper Cretaceous lava flows of the Carmacks Group.…”

Section: Geological Settingmentioning

confidence: 99%

“…The BCF extends across the Freegold Mountain area, cuts the DRB, and is unconformably overlain by and predates Upper Cretaceous lava flows of the Carmacks Group. Despite the fact that the BCF cuts the DRB, it was proposed that the batholith (and probably other mid-Cretaceous plutons) intruded during, and may in part have initiated, dextral shearing (Johnston 1999).…”

Section: Geological Settingmentioning

confidence: 99%

Emplacement ages and exhumation rates for intrusion-hosted Cu–Mo–Sb–Au mineral systems at Freegold Mountain (Yukon, Canada): assessment from U–Pb, Ar–Ar, and (U–Th)/He geochronometers

et al. 2012

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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...

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Large-scale coast-parallel displacements in the Cordillera: a granitic resolution to a paleomagnetic dilemma

Cited by 17 publications

References 12 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

Do transcurrent faults guide volcano growth? The case of NW Bicol Volcanic Arc, Luzon, Philippines

Emplacement ages and exhumation rates for intrusion-hosted Cu–Mo–Sb–Au mineral systems at Freegold Mountain (Yukon, Canada): assessment from U–Pb, Ar–Ar, and (U–Th)/He geochronometers

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