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TitleEarly Mesozoic terrane paradox in the northern Cordillera: a GEM2 perspective
AuthorZagorevski, AORCID logo
SourceBritish Columbia Geological Survey Open House 2018; 2018 p. 1
Alt SeriesNatural Resources Canada, Contribution Series 20190509
MeetingBritish Columbia Geological Survey Open House 2018; Victoria, BC; CA; November 2, 2018
ProvinceBritish Columbia; Yukon
NTS94; 95; 104; 105; 106; 114; 115; 116; 117
Lat/Long WENS-141.0000 -120.0000 70.0000 56.0000
Subjectstectonics; economic geology; Science and Technology; Nature and Environment; tectonic evolution; orogenies; terranes; accretion; sutures; mineral assemblages; oceanic crust; mineral deposits; porphyry deposits; ore mineral genesis; tectonic setting; Canadian Cordillera; Cache Creek Terrane; Stuhini-Lewes River-Nicola Arc; Intermontane Superterrane; Phanerozoic; Mesozoic; Jurassic; Triassic; Paleozoic
ProgramGEM2: Geo-mapping for Energy and Minerals Western Cordillera, Stikine Terrane
Released2018 11 02
The northern Cordillera comprises a collage of terranes that were accreted to the North American continental margin. Each terrane has its own stratigraphy, tectonic history and mineral deposits, and is bounded by faults. Identification of terranes in the Cordillera during the 1980s revolutionized the understanding of orogenic systems and continues to guide tectonic analysis of orogens and mineral exploration; however, inadequate modern understanding of some of the Cordilleran terranes, general lack of recognition of primary synaccretionary sutures and improper assignment of late faults as terrane boundaries necessitate a reassessment of the Cordilleran terrane framework. Using the Cache Creek Terrane as an example, I will outline how oceanic terranes were previously defined and demonstrate that, although revolutionary at the time, they do not conform to modern tectonic concepts. I will demonstrate that the Cache Creek Terrane is composed of at least two distinct terranes that were juxtaposed by a Middle Triassic and Middle to Late Triassic overlap assemblage. The overlap assemblage is correlative to the Stuhini-Lewes River-Nicola arc. This is consistent with some previous studies that interpreted the Stuhini and Nicola arcs as overlap assemblages on top previously deformed terranes. Recognition of the Middle to Late Triassic overlap in the Intermontane Superterrane has important implications for understanding the tectonics and the mineral endowment of the Cordillera. Primarily, re-evaluation of the Cache Creek Terrane highlights the need to re-examine other 'oceanic' and 'arc' terranes, their boundaries and their significance. Secondly, Paleozoic and early Mesozoic mineralized sequences may extend across currently drawn terrane boundaries. Lastly, Late Triassic to Early Jurassic calcalkalic and alkalic porphyry deposits did not form in intra-oceanic arcs, but rather in postcollisional successor arc sequences.

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