Yukon-Tanana terrane
Tags: amphibolite cretaceous granite granite gneiss green schists paleoproterozoic pluton quartzite schist
Description:
The Fairbanks mining district is located in the northwestern part of the Yukon-Tanana terrane (YTT), which consists of Paleoproterozoic, polymetamorphosed schist, of primarily sedimentary origin. The terrane is bounded on the north by the Tintina fault system and on the south by the Denali Fault system (Bundtzen, 1981). Hall (1985) suggests a more complex deformational history identifying four phases of penetrative tectonism. Northeast-trending faults, related to the Tintina and Denali fault systems, are the dominant structural trends. These regional fault systems have created different levels of crustal exposure, through oblique offsets that are primarily dip-slip, with a sinistral sense of shear (Robinson, 1990; Newberry, 1996). E-W to NW-directed faults and shears are present and are locally an important structural control to mineralization at most gold occurrences in the district.
The Fairbanks Schist, a unit of the Yukon-Tanana terrane, is host to much of the mineralization in the Fairbanks mining district. The dominant lithologies present include grey to brown, fine-grained micaceous-quartz schist and micaceous quartzite. Interlayered within the Fairbanks Schist is the Cleary sequence, a more varied assemblage of metamorphic lithologies. The Fairbanks Schist has undergone amphibolite facies metamorphism followed by a retrograde greenschist facies event.
The Fort Knox, Gilmore Dome, and Pedro Dome plutons are post-metamorphic, Late Cretaceous (~92 Ma) granitic complexes that intrude the metamorphic rocks in the eastern half of the Fairbanks mining district. A plutonic origin has been ascribed to much of the gold mineralization in the Fairbanks district. Fort Knox is hosted entirely within granite, whereas the other gold occurrences are in favourable metamorphic units or structures, near plutonic rocks.
Regional Geology of the Fairbanks District, Yukon-Tanana Terrane. Simplified from Newberry et al. (1996).
Deposits
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Name: Fort Knox
Phase: Operations
Mine Type: Pit
Intro:
Fort Knox is located 42 km by road northeast of the city of Fairbanks, in Alaska, United States of America. It is situated in the Fairbanks North Star Borough.
Mineralizations
No mineralizations available.
Placers
No placers available.