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Abstract: The Teslin suture zone (TSZ) forms the fundamental boundary between rocks deposited along the ancient margin of North America and allochthonous terranes to the west. Both North American and allochthonous rocks were ductilely deformed and concurrently metamorphosed under upper greenschist to amphibolite facies conditions at temperatures of 450-650°C and pressures greater than or equal to 6 kbars, probably during Late Triassic to mid-Jurassic time. North-northwest-striking foliation dips steeply in the western portion of the TSZ, but flattens to the east in North American autochthonous rocks.
The TSZ in the combined eastern Laberge/western Quit Lake map area is divisible into three distinct elongate structural domains parallel to the NNW-trending TSZ. Domains are identified by the distribution of differently oriented stretching lineations, Le1 and Le2, which formed during non-coaxial ductile deformation, and their associated "motion planes." Le1 trends westward and plunges down dip, whereas Le2 trends NNW-SSE and plunges shallowly. Le1 and Le2 are associated with the same mineral assemblages and formed under similar metamorphic conditions. Silicate mineral assemblages record temperatures up to 625°C, and pressures to 8 kbars; carbonate assemblages record temperatures in the range 350-500°C. The difference in temperature suggested by these assemblages may reflect lower temperatures of ductile flow and recrystallization in carbonate rocks.
Elongate lensoidal domains of Le1 are separated from each other by narrower NNW-trending zones of Le2, forming a regional-scale anastomosing shear zone. Two western domains of Le1 chiefly comprise allochthonous rocks, or rocks of uncertain affinity; however, the eastern domain comprises North American autochthonous rocks, previously considered to be unaffected by TSZ metamorphism and deformation. Macroscopic and microscopic kinematic indicators consistently record right-lateral or top-to-the-north movement parallel to Le2. Kinematics associated with Le1 are more complex. To the west, kinematic indicators record west-side-down (normal) movement parallel to Le1; elsewhere, both reverse and normal movement are recorded. Field relations suggest Le1 began forming earlier than Le2, followed by a period during which both Le1 and Le2 formed, and ended with movement parallel only to Le2. These geometries and movement histories indicate that rocks of the TSZ and structurall associated autochthonous rocks record a history of right-lateral transpression along this portion of the North American margin during Triassic-Jurassic time. Movement consisted of early tectonic shortening at a high angle to the ancient margin, followed by a period of right-lateral translation approximately parallel to the Mesozoic margin of western North America.
The TSZ in the combined eastern Laberge/western Quit Lake map area is divisible into three distinct elongate structural domains parallel to the NNW-trending TSZ. Domains are identified by the distribution of differently oriented stretching lineations, Le1 and Le2, which formed during non-coaxial ductile deformation, and their associated "motion planes." Le1 trends westward and plunges down dip, whereas Le2 trends NNW-SSE and plunges shallowly. Le1 and Le2 are associated with the same mineral assemblages and formed under similar metamorphic conditions. Silicate mineral assemblages record temperatures up to 625°C, and pressures to 8 kbars; carbonate assemblages record temperatures in the range 350-500°C. The difference in temperature suggested by these assemblages may reflect lower temperatures of ductile flow and recrystallization in carbonate rocks.
Elongate lensoidal domains of Le1 are separated from each other by narrower NNW-trending zones of Le2, forming a regional-scale anastomosing shear zone. Two western domains of Le1 chiefly comprise allochthonous rocks, or rocks of uncertain affinity; however, the eastern domain comprises North American autochthonous rocks, previously considered to be unaffected by TSZ metamorphism and deformation. Macroscopic and microscopic kinematic indicators consistently record right-lateral or top-to-the-north movement parallel to Le2. Kinematics associated with Le1 are more complex. To the west, kinematic indicators record west-side-down (normal) movement parallel to Le1; elsewhere, both reverse and normal movement are recorded. Field relations suggest Le1 began forming earlier than Le2, followed by a period during which both Le1 and Le2 formed, and ended with movement parallel only to Le2. These geometries and movement histories indicate that rocks of the TSZ and structurall associated autochthonous rocks record a history of right-lateral transpression along this portion of the North American margin during Triassic-Jurassic time. Movement consisted of early tectonic shortening at a high angle to the ancient margin, followed by a period of right-lateral translation approximately parallel to the Mesozoic margin of western North America.
Authors: Hansen, V.L.
Citation: Hansen, V.L., 1986. Petrotectonic study of the Teslin suture zone, Yukon: A progress report. In: Yukon Geology Volume 1, J.A. Morin and D.S. Emond (eds.), Exploration & Geological Services Division, Indian & Northern Affairs Canada, p. 125-130.
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| 1986GeolVol1 | Contained By | Morin, J.A. and Emond, D.S. (eds.) | Yukon Geology Volume 1 |
