Assean Lake Tonalite Gneiss Canada [343 gm ~ 3.5 Ga]

Assean Lake Complex: A Window into Early Crustal Evolution

The Assean Lake Complex is located adjacent to the Superior Craton, primarily in the area that marks the transition between the Superior Craton and the Trans-Hudson Orogeny. It's part of the Assean Lake crustal block, which geologists believe might represent a distinct crustal fragment sutured onto the Superior Craton during the formation of the Trans-Hudson Orogenic Belt. Its age is estimated to be 3.5 - 3.3 Ga. The Assean Lake Complex contains 4 Ga zircons, perhaps derived from a previously extensive "Acasta continent."

Adjacent Superior Craton: Ancient and Stable

The Superior Craton, located across Ontario, Quebec, and Manitoba in Canada, and extending into the United States, is one of Earth's oldest and most stable cratonic regions, formed during the Archean Eon over 3.5 to 2.5 billion years ago. This ancient craton contains rich geological features, including tonalitic gneisses and greenstone belts, and represents a vital record of early continental crust formation.

Insights from the Assean Lake Complex Tonalite Gneiss

The Assean Lake Complex, located at the northwestern edge of the craton in Manitoba, contains tonalite gneiss dated to 3.5–3.3 Ga — among the oldest crustal fragments on Earth. Similar to the renowned Acasta gneiss (~ 4.02 Ga) and Beartooth zircons (up to 3.96 Ga), the Assean Lake gneiss offers essential insights into early tectonic processes and the stability of Earth's primordial crust. Each formation, with its ancient zircons, provides critical data for reconstructing the early Earth's crustal history, showcasing unique snapshots of early tectonic evolution, and allowing researchers to explore the origins of continental stability and composition.

Assean Lake Complex Specimen Details

• Size: 110mm L X 77mm W X 30mm D, Weight: 343 grams
• What's Included: Certificate of Authenticity, tag, tag stand, specimen stand, and scientific information.
• Remarks: This is a nice size hand specimen with a flat front and rough back. Lightly sprayed for photographic purposes.

Assean Lake Complex: A Rare and Fascinating Ancient Crust Specimen

This region in Canada exhibits high-grade metamorphic rocks, including gneisses and granitoids, similar to rocks within the Superior Craton, but it also shows evidence of deformation associated with tectonic events characteristic of the Trans-Hudson orogeny. These features make the Assean Lake Complex a fascinating subject for collectors and geologists interested in early Earth tectonics and the geological evolution of the Canadian Shield.