Fingerprinting and tracing the signature of basement-hosted unconformity-type uranium alteration through thick Quaternary tills: an example from the Thelon Basin, Nunavut

• Main Author: Bustard, Aaron
• Format: Master Thesis
• Language: English
• Published: University of Waterloo 2016
• Subjects: geology; drift prospecting; Quaternary; till geochemistry; 3D modelling; Nunavut
• Online Access: http://hdl.handle.net/10012/10493

The question of whether or not it is possible to trace the signature of alteration haloes surrounding deep-seated unconformity-type U mineralization through thick Quaternary tills is one of great importance for those conducting exploration in glaciated areas. The geochemical signals associated with alteration are often subtle and subject to numerous sources of noise, and multi-till stratigraphies can completely mask or truncate dispersal patterns. To study glacial dispersal from alteration zones surrounding unconformity-type uranium mineralization, this study focuses on a deep-seated (>100 m) basement-hosted unconformitytype U mineralized body known as Tatiggaq, which is located in the Thelon Basin of Nunavut. The Tatiggaq area presents an ideal opportunity to investigate this problem, since the area is blanketed by a thick (12-34 m) multi-till stratigraphy, mineralization does not intersect the bedrock-till interface, and the mineralization is surrounded by an extensive illitic alteration halo that reaches the bedrock surface. The recovery of till samples from diamond drill core from the multi-till stratigraphy overlying the subcropping alteration halo provides a unique opportunity to model glacial dispersal and identify whether the fingerprint of buried alteration can be traced through three dimensions to the modern day surface. Sampling of till recovered during diamond drilling was combined with the sampling of surficial mudboils in the area surrounding Tatiggaq to trace the dispersal of alteration. The drill core samples were collected from four stratigraphic units that were deposited by early southwesterly and southerly ice flows, followed by a reversal in ice flow towards the northwest and westnorthwest. Knowledge of the till stratigraphy directly above the Tatiggaq alteration zone was used to construct a three dimensional model of the sediments overlying bedrock to allow the tracing of alteration through the subsurface. The geochemical fingerprint of the alteration halo at Tatiggaq was identified by ...