187-9 The Anorthositic Central Uplift of the Manicouagan Impact Structure

See more from this Division: Topical Sessions
See more from this Session: Planetary Pummeling: Cataclysmic Bombardment of the Solar System as Catastrophe, Catalyst, Cauldron, and Crucible

Monday, 6 October 2008: 10:15 AM
George R. Brown Convention Center, 310AD

Marc B. Biren, Planetary and Space Science Centre, Dept. Geology, University of New Brunswick, Fredericton, NB, Canada, John G. Spray, Planetary and Space Science Centre, Department of Geology, University of New Brunswick, Fredericton, NB, Canada and Lucy M. Thompson, Planetary and Space Science Centre, Department of Geology, Fredericton, NB, Canada
Abstract:
The Manicouagan impact crater, located at 51˚30'N, 68˚30'W in eastern Quebec, was formed by meteorite impact at 214±1 Ma. This well-preserved, undeformed structure is a ~100 km diameter complex crater formed in predominantly crystalline rocks of the Grenville province. Weathering and episodic glacial scouring have eroded and exposed its internal structure, which makes Manicouagan a valuable source of data. The rock types, level of preservation, and good outcrop at Manicouagan have the potential to facilitate comparisons with other planetary bodies; in particular the Moon.

The intention of this study is to establish how the central uplift at Manicouagan was emplaced. Impact scaling laws suggest it has undergone 10 – 15 km of rapid structural uplift. Four months of field work investigating the central uplift reveals a core of metamporhosed anorthositic rocks, that constitute Mont de Babel (957 m) and Maskelynite Peak (945 m), and associated high-grade, granitic and metabasic gneisses. These rocks retain their overall coherency (i.e., are not breccias), but are interspersed with pseudotachylite veins typically 1 mm to 15 cm thick. Sporadically distributed anastamosing, multi-vein pseudotachylite systems, 1 to 2 m wide, are interconnected by more pervasive subsidiary veins that occur at angles to these multi-vein zones. Where observed, offset associated with the pseudotachylite zones is typically 20-30 cm. Initial results indicate that the pseudotachylite systems have facilitated movement within the host rocks, but are unlikely to have enabled kilometer-scale displacements necessary for central uplift formation.

See more from this Division: Topical Sessions
See more from this Session: Planetary Pummeling: Cataclysmic Bombardment of the Solar System as Catastrophe, Catalyst, Cauldron, and Crucible