Geophysical investigation and reconstruction of lithospheric structure and its control on geology, structure, and mineralization in the Cordillera of northern Canada and eastern Alaska

Abstract

A reconstruction of the Tintina fault is applied to regional geophysical and topographic data, facilitating the definition of west trending lineaments within the lower crust and/or mantle lithosphere, oblique to the NW trending structure of the Cordilleran terranes. The lineaments, which exhibit a range of geophysical and geological signatures, are interpreted to be related to the Liard transfer zone, continuous to the Denali fault, that divided lower and upper plates during late Proterozoic-Cambrian rifting of the Laurentian margin. Three-dimensional gravity models show a density increase in the lower crust and mantle lithosphere to the north. The transfer zone also divides bimodal mantle xenolith suites to the south from unimodal suites to the north. These conclusions suggest that extended North American basement, related to Laurentian margin rifting that would have brought mantle lithosphere rocks to a shallow depth, continuously underlies a thin carapace of accreted terranes in western Yukon and eastern Alaska. The interpreted continuity of North American basement reaffirms that if oroclinal bending of the Intermontane terranes occurred, then it was prior to its emplacement upon the rifted basement. Examination of the spatial relationships between mineral occurrences and postaccretionary, Cretaceous lithospheric lineaments, from their manifestation in geophysical, geological, and topographic data, suggest that the late Proterozoic lineaments influenced Mesozoic mineralization through influence on the development of the shallow crustal structure, intrusion, and exhumation and erosion.

Landscape antiquity and Cenozoic drainage development of southern Yukon, through restoration modeling of the Tintina Fault

“…1) is a steeply NE-dipping (Welford et al 2001) right-lateral strike-slip fault (Roddick 1967), with the main period of movement generally interpreted to have occurred during the Paleogene, as discussed in the following text (Roddick 1967;Tempelman-Kluit 1980;Gabrielse et al 2006). The absolute magnitude of right-lateral displacement along the Tintina Fault was fairly well established in the seminal work of Roddick (1967), and varies only modestly (ϳ425-490 km) between workers, depending on the geological or geophysical offset markers considered (Roddick 1967;Dover 1994;Murphy et al 2002;Gabrielse et al 2006;Saltus 2007;Hayward 2015). However, the absolute timing of (continuous or episodic?)…”

“…The mapped fault locations were regularly sampled at a point spacing of ϳ3.5 km from 54.26°N to 65.67°N. The best-fit circle to these data, which has a center (rotation pole) at 27.5°N 160.92°W and a radius of ϳ4480 km (Hayward 2015), was found through iterative minimization of the square of the error between the circle and fault locations. The rotation pole is in close agreement with that estimated by Struik (1993).…”

The 3D Geophysical Investigation of a Middle Cretaceous to Paleocene Regional Décollement in the Cordillera of Northern Canada and Alaska

“…Lower plate rifting typically produces a broad zone of lithospheric thinning, with the fragmentation and rotation of upper crustal blocks, overlain by thick sedimentary sag basins (e.g., Lister et al, , ). The margin of the cold, strong craton (e.g., Tesauro et al, ), which has an architecture that extends for hundreds of kilometers to the west (e.g., Cook & Erdmer, ; Hansen et al, ; Hayward, ; Lund, ; Stewart, , and the references therein), exhibits a strong structural control on younger deformation. For example, the NE trending Liard line (LL, Figure ) is interpreted as a Precambrian structure that controlled the northern margin of a Mesoproterozoic basin within the craton (e.g., Muskwa, Ross et al, ).…”

“…See Table for legend. KP, Klondike plateau; LL, Liard line (Cecile et al, ; Hayward, ); RT, Richardson trough. Faults: DAW, Dawson; DF, Denali; IT, Inconnu thrust; PT, Plateau thrust; RST, Robert Service thrust; TES, Teslin; TF, Tintina; TL, Tummel; TT, Tombstone thrust.…”

“…Unraveling the complex and protracted tectonic history of accretionary orogens requires a multidisciplinary approach integrating geological and geophysical techniques (e.g., Cook et al, ; Elger et al, ; Gabrielse et al, ; Hayward, ; Johnston, ; Nelson et al, ; Pfiffner, ). The northern Cordillera of Canada and Alaska, and the Cordillera Oriental to Subandean zone of the Andes of Bolivia and Argentina are representative of contractional orogens with atypically (e.g., Pfiffner, ) backarc positioned fold and thrust belts that may result from flat‐slab subduction (e.g., Ramos, ; Ramos & Fulguera, ).…”