101 Precambrian Geology (Posters)

Monday, 10 October 2011
9:00 AM - 6:00 PM
Hall C

NEW U-PB GEOCHRONOLOGICAL CONSTRAINTS ON THE STRUCTURAL EVOLUTION OF THE SOUTHERN PROVINCE, SUDBURY, CANADA

Paper number: 101-10
Program: Technical Sessions
Time: 9:00 AM – 6:00 PM

Authors

Abstract

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 S1 foliation in the ca. 2420 Ma Creighton Pluton are overprinted by Sudbury impact breccia. The dikes have crystallization ages of 2343±17 Ma and 2344±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±23 Ma and a crystallization age of 1704±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±29 Ma, which is within error of the previously published U-Pb monazite age of 1743±3 Ma from the Eden Lake Complex and the U-Pb titanite age of 1749±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±71 Ma and a crystallization age of 1467±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.