Yukon Geological Survey publication metadata (English, HTML)

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2026-08-26

The White Channel Gravel (Pliocene) is the most important gold-bearing unit in the world famous Klondike goldfields of west-central Yukon. It is up to 46 m thick and consists of framework-supported, poorly bedded, slightly muddy sandy gravel that was deposited by braided rivers. Historically, this unit is subdivided into a lower 'white gravel' and an upper 'yellow gravel'. The colour of the white gravel is due to an abundance of quartz clasts and an alteration of the sand-mud matrix that has been referred to as 'leaching' or 'bleaching'. Previous researchers concluded that the alteration is hydrothermal in origin, but a review of this research shows that there is no unequivocal evidence supporting hydrothermal alteration. Petrographic examination of in situ samples from both the white and yellow gravel reveals a depositional fabric and an alteration fabric, although the alteration is better developed in the white gravel. The alteration is reinterpreted as the result of weathering, and particularly diagenesis due to groundwater flow.

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