Publication Type:
Book ChapterSource:
Geological Society of America, 2011 annual meeting, Geological Society of America (GSA), Boulder, CO, United States, Volume 43, p.270 (2011)ISBN:
0016-7592Keywords:
absolute age, age, Canada, Canadian Shield, dates, eastern canada, nesosilicates, North America, Ontario, orthosilicates, Precambrian, silicates, Southern Province, Sudbury Ontario, U/Pb, zircon, zircon groupAbstract:
Results from LA-ICP-MS U-Pb zircon geochronology provide new constraints on the timing of deformation events of the Southern Province southeast of the 1850 Ma Sudbury impact structure. The ages of samples collected along a traverse from the Grenville Front Tectonic Zone to the base of the Sudbury Igneous Complex suggest that the Southern Province underwent several deformation events from the Paleoproterozoic to late Mesoproterozoic. Two pre-impact granitic dikes, which cut an early S (sub 1) foliation in the ca. 2420 Ma Creighton Pluton are overprinted by Sudbury impact breccia. The dikes have crystallization ages of 2343 + or - 17 Ma and 2344 + or - 47 Ma providing the best-estimated minimum ages for the Blezardian Orogeny, which is the oldest deformation event in the Southern Province in the Sudbury region. The Southern Province experienced several post-impact orogenic events. A weakly foliated granitic dike that cuts across a post-impact foliation has an inherited zircon age of 2639 + or - 23 Ma and a crystallization age of 1704 + or - 13 Ma, which is interpreted as the minimum age for earliest post-impact deformation of the Southern Province. A post-impact granitic intrusion of the Eden Lake Complex near the Grenville Front Tectonic Zone yielded a crystallization age of 1744 + or - 29 Ma, which is within error of the previously published U-Pb monazite age of 1743 + or - 3 Ma from the Eden Lake Complex and the U-Pb titanite age of 1749 + or - 12/8 Ma from a biotite-granodiorite near Little Raft Lake. This age defines the maximum age of weak foliation in the Eden Lake Complex. A foliated and lineated megracrystic granite collected from the Chief Lake Complex yielded a lower intercept age of 945 + or - 71 Ma and a crystallization age of 1467 + or - 18 Ma, which defines the maximum age of the strong foliation within the Chief Lake Complex. The younger age of ca. 945 Ma may reflect the high-grade metamorphism of the surrounding area and indicating that the Southern Province was further deformed during the 1.2-1.0 Ga Grenvillian Orogeny.
Notes:
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