The Snowbird Tectonic Zone (STZ) is a geological structure in the western

Canadian Shield The Canadian Shield (french: Bouclier canadien ), also called the Laurentian Plateau, is a geologic shield, a large area of exposed Precambrian igneous and high-grade metamorphic rocks. It forms the North American Craton (or Laurentia), the anc ...

which forms a geophysical boundary between the

Hearne Craton The Hearne Craton is a craton in northern Canada which, together with the Rae Craton, forms the Western Churchill Province. Hearne is one of the six Archaean cratons of the Canadian Shield (the other being Slave, Rae, Wyoming, Superior, Nain) ...

and the south-west arm of the

Rae Craton 250px, North America cratons and basement rock. The Rae Craton is an Archean craton located in northern Canada north of the Superior Craton. Ungava Peninsula The Ungava Peninsula, situated on the northeast portion of the Canadian Shield, is wher ...

. It is enigmatic and has been interpreted as a Proterozoic suture or escape structure, or an Archaean suture reactivated during either the Archaean or Palaeoproterozic. It stretches from the

Canadian Cordillera The Pacific Cordillera, also known as the Western Cordillera or simply The Cordillera, is a top-level physiographic region of Canada, referring mainly to the extensive cordillera system in Western and Northwestern Canada that constitutes the northe ...

north-east to

Hudson Bay Hudson Bay ( crj, text=ᐐᓂᐯᒄ, translit=Wînipekw; crl, text=ᐐᓂᐹᒄ, translit=Wînipâkw; iu, text=ᑲᖏᖅᓱᐊᓗᒃ ᐃᓗᐊ, translit=Kangiqsualuk ilua or iu, text=ᑕᓯᐅᔭᕐᔪᐊᖅ, translit=Tasiujarjuaq; french: b ...

, diagonally crossing

Alberta Alberta ( ) is one of the thirteen provinces and territories of Canada. It is part of Western Canada and is one of the three prairie provinces. Alberta is bordered by British Columbia to the west, Saskatchewan to the east, the Northwest Ter ...

Saskatchewan Saskatchewan ( ; ) is a province in western Canada, bordered on the west by Alberta, on the north by the Northwest Territories, on the east by Manitoba, to the northeast by Nunavut, and on the south by the U.S. states of Montana and North ...

, the

Northwest Territories The Northwest Territories (abbreviated ''NT'' or ''NWT''; french: Territoires du Nord-Ouest, formerly ''North-Western Territory'' and ''North-West Territories'' and namely shortened as ''Northwest Territory'') is a federal territory of Canada. ...

, and

Nunavut Nunavut ( , ; iu, ᓄᓇᕗᑦ , ; ) is the largest and northernmost territory of Canada. It was separated officially from the Northwest Territories on April 1, 1999, via the '' Nunavut Act'' and the '' Nunavut Land Claims Agreement Act'' ...

. It truncates the

Taltson Magmatic Zone The Taltson Magmatic Zone (TMZ) is a north-trending belt of Archean to Paleoproterozoic granitic basement gneiss, amphibolite supracrustal gneissic rock and Paleoproterozoic magmatic rocks in the Canadian Shield, extending from Northern Alberta to ...

, which suggests an age younger than 1.95 Ga. In the Baker Basin (near Baker Lake, northern STZ) it is overlapped by

lamprophyre Lamprophyres () are uncommon, small-volume ultrapotassic igneous rocks primarily occurring as dikes, lopoliths, laccoliths, stocks, and small intrusions. They are alkaline silica- undersaturated mafic or ultramafic rocks with high magne ...

dykes and volcanics, suggesting a minimum age of 1.85 Ga; however, a younger age (1.84–1.78 Ga) can be inferred from convergence across the STZ in Alberta. interpreted it as part of the Hudsonian orogeny, a collisional event in which microcontinents were accreted to

Laurentia Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, althoug ...

around 1.85 Ga. Using U-Pb dating, estimated the timing of

eclogite Eclogite () is a metamorphic rock containing garnet ( almandine- pyrope) hosted in a matrix of sodium-rich pyroxene ( omphacite). Accessory minerals include kyanite, rutile, quartz, lawsonite, coesite, amphibole, phengite, paragonite, ...

facies In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with specified characteristics, which can be any observable attribute of rocks (such as their overall appearance, composition, or condition of formatio ...

metamorphism, a process which require transport to mantle depth, to 1.904 Ga. They, nevertheless, concluded that it remains unclear whether the STZ is a reactivated Archaean structure or a suture documenting the opening and closure of a Proterzoic ocean.

References

Notes

Sources

* * * * Archean volcanism Paleoproterozoic volcanism Volcanism of Alberta Volcanism of the Northwest Territories Volcanism of Nunavut Volcanism of Saskatchewan {{Canada-geology-stub