Bulk composition of the Tanco pegmatite at Bernic Lake, Manitoba, Canada

Abstract

The Tanco pegmatite at Bernic Lake, Manitoba, Canada is a highly fractionated rare-element class, LCT family pegmatite with 9 internal zones and is one of the largest complex internally zoned pegmatites in the world. The outer zones of the pegmatite are generally concentric, while the shape of the inner zones, based on underground workings and drill core observations, are very irregular and complex. Tanco presents a unique opportunity to calculate the bulk composition of a pegmatite which, unlike previous works on other pegmatites, does not need to consider structural deformation and/or erosion to reconstruct the original size and shape. Tanco is essentially an undeformed blind pegmatite, with only minimal exposure through erosion at the bottom of Bernic Lake. Almost no reconstructive interpretation is required as th amount of eroded material is negligible and does not affect the over-all bulk composition calculations. Given the available information from the drill core logs and underground workings on theTanco pegmatite, it was possible to create the first 3D computer representation of a pegmatite. (Abstract shortened by UMI.)