Report (English, PDF)

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Publisher-reported update

2026-08-26

The northeast corner of Grass Lakes map area is underlain by polydeformed metasedimentary, metavolcanic and metaplutonic rocks of Yukon-Tanana Terrane, and ultramafic rocks of unknown affinity. Layered metasedimentary and metavolcanic rocks, about half the area mapped, include a basal unit of quartz-rich schist, psammite, metapelitic schist, and grit with a laterally continuous sandy marble marker high in the unit; a unit made up of a variety of mafic metavolcanic (?) rock types interlayerd with carbonaceous phyllite, grey quartzite, quartzofeldspathic psammite and grit; Devono-Mississippian felsic metavolcanic (?) rocks interlayered with carbonaceous phyllite and grey quartzite, and an upper mafic metavolcanic (?) unit with quartzofeldspathic psammite and grit, and carbonaceous phyllite and quartzite. Metarhyolite of the third unit hosts the Kudz Ze Kayah massive sulphide deposit and underlies numerous gossans. The succession is thought to be upright based on an interpretation of the structure of metarhyolitic rocks at Kudz Ze Kayah. The remainder of the area is underlain by metaplutonic rocks. Quartz-feldspar metaporphyry near Kudz Ze Kayah is thought to be a hypabyssal…

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