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

Mesozoic extension along Australia's southern margin and the evolution and architecture of the Otway Basin were probably controlled by three factors: 1) changes in global plate movements driven by mantle processes; 2) the structural grain of Palaeozoic basement; and, 3) changes in subduction along Gondwana's Pacific margin. Major plate realignments controlled the Jurassic onset of rifting, the mid-Cretaceous break-up and the Eocene onset of rapid spreading in the Southern Ocean.The initial southern margin rift site was influenced by the northern limit of Pacific margin (extensional) Jurassic dolerites and the rifting may have terminated dolerite emplacement. Changed conditions of Pacific margin subduction (e.g. ridge subduction) in the Aptian may have placed the Australia-Antarctic plates into minor compression, abating Neocomian southern margin rifting. It also produced vast amounts of volcanolithic sediment from the Pacific margin arc that was funnelled down the rift graben, causing additional regional subsidence due to loading. Albian orogenic collapse of the Pacific margin, related to collision with the Phoenix Plate, influenced mid-Cretaceous breakup propagating south of Tasmania and into the Tasman Sea.Major offsets of the spreading axis during breakup, at the Tasman and Spencer Fracture zones, were most likely controlled by the location of Palaeozoic terrane boundaries. The Tasman Fracture System was reactivated during break-up, with considerable uplift and denudation of the Bass failed rift to the east, which controlled Otway Basin facies distribution. Palaeozoic structures also had a significant effect in determining the half graben orientations within a general N-S extensional regime during early Cretaceous rifting. The late Cretaceous second stage of rifting, seaward of the Tartwaup, Timboon and Sorell fault zones, left a stable failed rift margin to the north, but the attenuated lithosphere of the Otway-Sorell microplate to the south records repeated extension that led to continental separation and may be part of an Antarctic upper plate.

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A Cretaceous back-arc basin in the Coast Belt of the northern Canadian Cordillera: evidence from geochemical and neodymium isotope characteristics of the Kluane metamorphic assemblage, southwest Yukon

Canadian Journal of Earth Sciences ◽

10.1139/e00-076 ◽

2001 ◽

Vol 38 (1) ◽

pp. 91-103 ◽

Cited By ~ 15

Author(s):

Jochen E Mezger ◽

Robert A Creaser ◽

Philippe Erdmer ◽

Stephen T Johnston

Keyword(s):

Late Jurassic ◽

Metamorphic Rock ◽

Tectonic Setting ◽

Source Region ◽

Canadian Cordillera ◽

Metasedimentary Rocks ◽

Depleted Mantle ◽

Metamorphic Assemblage ◽

Continental Source ◽

Back Arc

The Coast Belt of the northern Cordillera in Canada is the locus of the boundary between accreted and ancient North American margin rocks. The largest exposure of metasedimentary rocks in the Coast Belt is the Kluane metamorphic assemblage (KMA), a northwest-striking belt 160 km long of graphitic micaquartz schist and gneiss with minor interfoliated olivine serpentinite. The KMA does not appear to correlate with other sedimentary or metamorphic rock assemblages in the Canadian Cordillera. To determine its tectonic setting and protolith provenance, we analyzed trace element, rare earth elements, and neodymium isotope compositions of the KMA, of the adjacent pericratonic Aishihik metamorphic suite (AMS) of the YukonTanana terrane, and of adjacent slates of the Dezadeash Formation (DF), filling a Late Jurassic Early Cretaceous flysch basin. The εNd(0) values of analyzed KMA samples range from 1.4 to 5.6 and depleted mantle model ages (TDM) range from 1.16 to 1.45 Ga. KMA samples are intermediate between more evolved AMS samples (average εNd(0) 25, TDM = 2.6 Ga) and more juvenile DF samples (εNd(0) = +1.9, TDM = 0.95 Ga). The intermediate characteristics of the KMA samples cannot be linked to a known source region and are interpreted to reflect homogeneous mixing from predominantly juvenile and minor evolved sedimentary sources. A compatible tectonic setting is a back-arc basin within influence of a continental source. Eastward subduction of the KMA beneath ancient North America collapsed the back-arc basin by latest Cretaceous time.

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Geochemistry and tectonic setting of volcanics from the Anyox mining camp, British Columbia

Canadian Journal of Earth Sciences ◽

10.1139/e93-005 ◽

1993 ◽

Vol 30 (1) ◽

pp. 48-59 ◽

Cited By ~ 5

Author(s):

Alan D. Smith

Keyword(s):

Field Strength ◽

Basaltic Andesite ◽

Middle Jurassic ◽

High Field ◽

Tectonic Setting ◽

Canadian Cordillera ◽

High Field Strength ◽

Volcanogenic Massive Sulphide ◽

Mid Ocean Ridge ◽

Ocean Ridge

Volcanogenic massive sulphide deposits at Anyox in the Tracy Arm terrane of the Canadian Cordillera are associated with a sequence of tholeiitic basalts with minor intercalated basaltic andesite tuffs and siliceous sediments. Sm–Nd and Pb–Pb systematics indicate an Early to Middle Jurassic age. The tholeiites are characterized by normal mid-ocean-ridge basalt to weak island-arc tholeiite trace element signatures with slight enrichment in large-ion lithophile elements and depletion in high-field-strength elements, high 207Pb/204Pb, and εNd(170 Ma) values of +8.2 to +8.4. The mineralized sequence is conformably overlain by argillaceous sediments and minor limestones. These features, combined with the location of the strata and similarities with the Spider Peak Formation of the Methow terrane, indicate an origin in a narrowing marginal basin that once separated superterranes I and II.

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Hilislope geomorphology and geotechnique

Progress in Physical Geography Earth and Environment ◽

10.1177/030913339301700205 ◽

1993 ◽

Vol 17 (2) ◽

pp. 173-189 ◽

Cited By ~ 4

Author(s):

Michael J. Bovis

Keyword(s):

Debris Flows ◽

Mass Movement ◽

Canadian Cordillera ◽

Eastern Canada ◽

The Pacific ◽

Rock Creep ◽

Flow Slides ◽

Talus Slopes ◽

Hillslope Geomorphology ◽

Geotechnical Studies

This review focuses on recent Canadian contributions to hillslope geomorphology, and emphasizes geotechnical studies of mass movement phenomena in the Canadian Cordillera, including debris flows, rock avalanches, talus slopes, rock creep, and slow earthflows. A brief discussion is included of quick-clay flow slides in eastern Canada, and gelifluction phenomena in arctic and alpine areas. Comparisons are made with similar geotechnical work conducted in the Pacific-rim steeplands.

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A Gondwana pre-break up related magmatism in Bafoussam area, west Cameroon: source characteristics and 40Ar/39Ar geochronology

International Journal of Advanced Geosciences ◽

10.14419/ijag.v7i1.21354 ◽

2019 ◽

Vol 7 (1) ◽

pp. 23

Author(s):

Gus Djibril Kouankap Nono ◽

Pierre Wotchoko ◽

Evine Laure Tanko Njiosseu ◽

Sylvestre Ganno ◽

Joelle Flore Tene Djoukam ◽

...

Keyword(s):

High Temperature ◽

Early Stage ◽

Tectonic Setting ◽

Central Africa ◽

High Alumina ◽

Primitive Mantle ◽

Plate Tectonic ◽

Calc Alkaline ◽

Source Characteristics ◽

Break Up

The Gondwana pre-break up related formations in Bafoussam area are transitional calc-alkaline doleritic dykes exhibiting high Alumina and low Ti-Mg contents. Their REE compositions are similar to those of E-MORB (Nd/Nb≈1, Zr/Nb≤20). A high partial melting of about 20% of Garnet peridotites source having primitive mantle composition, is inferred to the studied rocks. They are slightly evolved 50<Mg#<54, and its clinopyroxenes are augite of high temperature (600°C-1100°C). The studied dykes were emplaced in a within-plate tectonic setting and yield a 40Ar-39Ar plateau ages of 229±7Ma. These ages are slightly different from those of dolerites from the Oban-Obudu massif (Nigeria), from the basaltic dyke of the Cameroon Volcanic Line and from the Karoo-Ferrar mafic magmatism, all interpreted as magmatism that preceded the break-up of Gondwana. The emplacement age of 229±7Ma of dolerites from Bafoussam area relates them to the very early stage of Gondwana pre-break up magmatism in central Africa.

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Singularity Analysis of Volcanic Ages and Implications for Tectonic Setting in the Mesozoic, Great Xing’an Range, Northeast China

Minerals ◽

10.3390/min9070419 ◽

2019 ◽

Vol 9 (7) ◽

pp. 419

Author(s):

Zhu ◽

Cheng

Keyword(s):

Tectonic Setting ◽

Singularity Analysis ◽

Pacific Plate ◽

Late Mesozoic ◽

Plate Movement ◽

Geological Processes ◽

The Pacific ◽

Slab Rollback ◽

Slab Breakoff ◽

Great Xing’An Range

Frequency distribution of zircon U–Pb ages has been commonly utilized to interpret the age of a magmatic event. Anomalies in age peaks are related to plate movement caused by mantle convection during the formation of supercontinents and continent crust growth. In this paper, a singularity analysis method (frequency anomalies) is used to analyze a dataset (n = 823, discordance lower than 10%) of zircon U–Pb ages from the Great Xing’an Range (GXR), in order to characterize the causal relationship between age transitions and Pacific Plate subduction. The numberage plot result shows that there is a peak around at 125 Ma, and the log–log plot reveals that there are two transitional ages (knee points) at 125 Ma and 145 Ma. The age densities of the peak at 125 Ma and the transition at 145 Ma can both be fitted by power law functions, which indicate transitional ages have the characteristic of singularity. Combined with the subduction geological background in the late Mesozoic, the possible singularity mechanisms corresponding to the age peak at 125 Ma and the transition at 145 Ma are slab rollback and slab breakoff of the Pacific Plate, which is consistent with conclusions from geology and geochemistry. This result suggests that singularity analysis can be used as a new method to quantitatively characterize volcanic activities and tectonic setting in geological processes.

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Break-up spots: Could the Pacific open as a consequence of plate kinematics?

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2007.10.013 ◽

2008 ◽

Vol 265 (1-2) ◽

pp. 195-208 ◽

Cited By ~ 19

Author(s):

Valérie Clouard ◽

Muriel Gerbault

Keyword(s):

The Pacific ◽

Break Up ◽

Plate Kinematics

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Spatial Patterns of Preinstrumental Moisture Variability in the Southern Canadian Cordillera

Journal of Climate ◽

10.1175/jcli3416.1 ◽

2005 ◽

Vol 18 (15) ◽

pp. 2847-2863 ◽

Cited By ~ 14

Author(s):

Emma Watson ◽

Brian H. Luckman

Keyword(s):

Twentieth Century ◽

Severity Index ◽

Drought Severity ◽

Canadian Cordillera ◽

Entire Area ◽

The Pacific ◽

Dry Conditions ◽

The Pacific Ocean ◽

Instrumental Records ◽

Precipitation Records

Abstract Extreme wet and dry intervals of the last 350 yr in the Canadian Cordillera and adjacent United States are examined using a network of 25 tree-ring-based precipitation and Palmer Drought Severity Index (PDSI) reconstructions. Reconstructed twentieth-century-mapped patterns compare well with patterns based on the instrumental records at both annual and decadal scales. During the most extreme events, dry conditions occurred over the entire area. The longest widespread drought in the last 350 yr occurred from 1917 to 1941. Shorter intervals of more severely dry conditions occurred in the early 1720s, 1750s, 1790s, 1860s–70s, and the 1890s. Many of the driest individual years and most extreme dry periods of <7 yr are reconstructed for the eighteenth century. The longest, wettest periods identified by these reconstructions occurred in the early twentieth century. In agreement with published studies that explore links between instrumental precipitation records from the region and conditions in the Pacific Ocean, the reconstructed records show that drier (wetter)-than-normal conditions are associated with El Niño (La Niña) events and the positive (negative) phase of the Pacific decadal oscillation (PDO).

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