Phanerozoic crustal growth: U–Pb and Sr–Nd isotopic evidence from the granites in northeastern China

Cordilleran orogenic systems, such as the modern Andes, are long belts of deformation and magmatism that are associated with the subduction of oceanic plates beneath continental ones. Although the oceanic plates have been thought to control the evolution of such systems, a number of processes operating in the upper continental plates have not been fully accounted for. The western American Cordilleras, for example, display a 25–50 million year (Myr) cycle of linked upper-plate processes. In a typical cycle, as the two plates converge and a magmatic arc forms, most of the continental crust shortens by thrusting behind the arc, whereas the lowermost continental lithosphere is shoved beneath the arc — a process that fuels episodic high-flux magmatism in the arc and simultaneously generates dense melt residues. On reaching a critical mass, these residues sink into the mantle, creating space beneath the arc and setting the stage for renewal of the cycle. This alternative model explains key features of Cordilleran systems, such as cyclical trends in the flux and composition of magma supplied to the upper plate, and the foundering of arc roots. Cordilleran orogenic systems are long belts of deformation and magmatism that form when oceanic plates subduct beneath continental ones. Links between processes in the upper continental plate explain key features of Cordilleran systems, such as cyclical trends in the flux and composition of magma supplied to the upper plate.

Cyclicity in Cordilleran orogenic systems

▪ Abstract The Cordilleran orogen of western North America is a segment of the Circum-Pacific orogenic belt where subduction of oceanic lithosphere has been underway along a great circle of the globe since breakup of the supercontinent Pangea began in Triassic time. Early stages of Cordilleran evolution involved Neoproterozoic rifting of the supercontinent Rodinia to trigger miogeoclinal sedimentation along a passive continental margin until Late Devonian time, and overthrusting of oceanic allochthons across the miogeoclinal belt from Late Devonian to Early Triassic time. Subsequent evolution of the Cordilleran arc-trench system was punctuated by tectonic accretion of intraoceanic island arcs that further expanded the Cordilleran continental margin during mid-Mesozoic time, and later produced a Cretaceous batholith belt along the Cordilleran trend. Cenozoic interaction with intra-Pacific seafloor spreading systems fostered transform faulting along the Cordilleran continental margin and promoted incipient ...

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Evolution of the north american cordillera

Abstract Palaeozoic to early Mesozoic terranes of the North American Cordillera mostly originated from three distinct regions in Palaeozoic time: the western peri-Laurentian margin, western (Asian) Panthalassa, and the northern Caledonides–Siberia. A review of geological history, fossil and provenance data for the Caledonian–Siberian terranes suggests that they probably occupied an intermediate position between northern Baltica, northeastern Laurentia and Siberia, in proximity to the northern Caledonides, in early Palaeozoic time. Dispersion of these terranes and their westward incursion into eastern Panthalassa are interpreted to result from development of a Caribbean- or Scotia-style subduction system between northern Laurentia and Siberia in mid-Palaeozoic time, termed here the Northwest Passage. Westward propagation of a narrow subduction zone coupled with a global change in plate motion, related to the collision of Gondwana with Laurentia–Baltica, are proposed to have led to initiation of subduction along the western passive margin of Laurentia and development of the peri-Laurentian terranes as a set of rifted continental fragments, superimposed arcs and marginal ocean basin(s) in mid- to late Palaeozoic time. Diachronous orogenic activity from Late Silurian in Arctic Canada, to Early Devonian in north Yukon and adjacent Alaska, Middle Devonian in southeastern British Columbia, and Late Devonian–Early Mississippian in the western USA records progressive development of the Northwest Passage and southward propagation of subduction along western Laurentia.

A Palaeozoic Northwest Passage: incursion of Caledonian, Baltican and Siberian terranes into eastern Panthalassa, and the early evolution of the North American Cordillera

Lithospheric velocity structure and its relationship to regional tectonics and development of the southern Canadian Cordillera are derived from a synthesis of interpretations from nine in-line seismic refraction–wide-angle reflection profiles and broadside data recorded during the Lithoprobe Southern Cordillera Refraction Experiment (SCoRE) and other refraction experiments across southern British Columbia, and one profile in northwestern Washington. Consistency of the SCoRE two-dimensional models at their intersection positions is achieved through application of a simultaneous inversion of all relevant traveltime data. The cross-sectional and map presentations demonstrate the strong degree of three-dimensional heterogeneity within the crust and upper mantle. A first-order characteristic is the continuous increase in crustal velocities westward from the Foreland belt to the Insular belt. The variations do not correlate with the morphogeological belts; they do correspond with large-scale geological and (or)...

Lithospheric structure in the southern Canadian Cordillera from a network of seismic refraction lines

Sr and Nd isotopic compositions of the late Paleozoic metavolcanics and Late Triassic to early Tertiary granitoids from four magmatic episodes in the southern Canadian Cordillera from the Kootenay ...

Nd–Sr isotopic constraints on the interactions of the Intermontane Superterrane with the western edge of North America in the southern Canadian Cordillera

Eleven U–Pb zircon dates from seven intrusives in the Nelson–Castlegar area provide new age constraints on the granitoid magmatism in southeastern British Columbia. Four samples from the Nelson Batholith date three distinct intrusive phases spanning ca. 10 Ma. One sample from the eastern porphyritic phase (Coffee Creek) yields the oldest age at 172.5 ± 5.0 Ma. Two samples from the central K-feldspar megacrystic phase (Crescent Bay) give precise ages at 162.0 ± 1.0 and 161.5 ± 1.5 Ma, and possibly date the youngest phase of the batholith. An intermediate age of emplacement at 166.0 ± 3.0 Ma is suggested for the southern tail of the batholith. The new and published data suggest that the Nelson Batholith was emplaced in roughly concentric zones. In contrast, the southern quartz diorite phase and the northwestern granodiorite phase of the Bonnington Pluton were emplaced coevally during the Middle Jurassic at 167.4 ± 2.0 and 165.0 ± 3.0 Ma, respectively. Middle Jurassic ages were also obtained for a sample of ...

U–Pb geochronology of Jurassic to early Tertiary granitic intrusives from the Nelson–Castlegar area, southeastern British Columbia, Canada

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Nd–Sr isotopic constraints on the interactions of the Intermontane Superterrane with the western edge of North America in the southern Canadian Cordillera

U–Pb geochronology of Jurassic to early Tertiary granitic intrusives from the Nelson–Castlegar area, southeastern British Columbia, Canada