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Conference Proceedings

World Gold 2019

Conference Proceedings

World Gold 2019

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Orogenic gold mineral systems of the North American Cordillera – a review

Late Jurassic to Early Cretaceous orogenic gold systems in British Columbia, Yukon, and Alaska contain deposits that are structurally linked to collision of the Intermontane terranes with the ancient North American margin. In British Columbia localities, penetrative strain fabrics of the host-rock sequence are consistent with orogen-normal shortening and subsequent orogen-parallel extension. Many of the Late Jurassic to Early Cretaceous orogenic gold systems are predominantly situated in fold-and-thrust belts, and not steep, crustal penetrating transcurrent fault zones. Orogen-parallel escape tectonics was initiated in the mid-Cretaceous, possibly triggered by a change in the trajectory of North America at about 110 Ma. All the structural zones active in the mid-Cretaceous were kinematically linked by middle to lower crustal detachments to produce cross-orogen shortening. These structures outline a large Intermontane tectonic flake that was escaping to the northwest, bounded by sinistral shear in the Coast belt to the west, dextral shear in the Omenica belt to the east, and the Tombstone thrust on its leading northern edge. Many of the mid-Cretaceous orogenic gold deposits developed in and adjacent to these mid-Cretaceous fault zones. Orogenic gold deposits in northwestern BC have formed at different depths in second/third-order structures along the long-lived (Jurassic to Eocene), crustal-scale Llewellyn fault zone in the late Cretaceous (75-120 Ma). This older history is obscured by late, brittle, strike-slip faulting and syntectonic magmatism associated with young (62-37 Ma) low-sulphidation epithermal gold-silver mineralization. Some workers speculate that the same Eocene event produced orogenic gold deposits of the Juneau gold belt in southeastern Alaska. Collectively, these geological and geochronological studies allow for the creation of a mineral systems framework for orogenic gold in the northern American Cordillera similar to that which exists for several Proterozoic and Archean cratons. This is an abstract only. No full paper was prepared for this abstract. CITATION:Rowins, S M, 2019. Orogenic gold mineral systems of the North American Cordillera a review, in Proceedings World Gold 2019, p 95 (The Australasian Institute of Mining and Metallurgy: Melbourne).
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  • Published: 2018
  • PDF Size: 0.695 Mb.
  • Unique ID: p201906014

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