Geology and origin of epigenetic lode gold deposits, Tintina Gold Province, Alaska and Yukon

Richard J. Goldfarb; Erin E. Marsh; Craig J. R. Hart; John L. Mair; Marti L. Miller; Craig Johnson

doi:10.3133/sir20075289A

Geology and origin of epigenetic lode gold deposits, Tintina Gold Province, Alaska and Yukon

Scientific Investigations Report 2007-5289-A

By: Richard J. Goldfarb, Erin E. Marsh, Craig J. R. Hart, John L. Mair, Marti L. Miller, and Craig Johnson

Edited by: Larry P. Gough and Warren C. Day

https://doi.org/10.3133/sir20075289A

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Larger Work: This publication is Chapter A of Recent U.S. Geological Survey Studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada-Results of a 5-Year Project
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Abstract

More than 50 million ounces of lode gold resources have been defined in the previous 15 years throughout accreted terranes of interior Alaska and in adjacent continental margin rocks of Yukon. The major deposits in this so-called Tintina Gold Province formed around 105 to 90 million years ago in east-central Alaska and Yukon, and around 70 million years ago in southwestern Alaska, late in the deformational history of their host rocks. All gold deposits studied to date formed from CO₂ -rich and ¹⁸O-rich crustal fluids, most commonly of low salinity. The older group of ores includes the low-grade intrusion-related gold systems at Fort Knox near Fairbanks and those in Yukon, with fluids exsolved from fractionating melts at depths of 3 to 9 kilometers and forming a zoned sequence of auriferous mineralization styles extending outward to the surrounding metasedimentary country rocks. The causative plutons are products of potassic mafic magmas generated in the subcontinental lithospheric mantle that interacted with overlying lower to middle crust to generate the more felsic ore-related intrusions. In addition, the older ores include spatially associated, high-grade, shear-zonerelated orogenic gold deposits formed at the same depths from upward-migrating metamorphic fluids; the Pogo deposit is a relatively deep-seated example of such. The younger gold ores, restricted to southwestern Alaska, formed in unmetamorphosed sedimentary rocks of the Kuskokwim basin within 1 to 2 kilometers of the surface. Most of these deposits formed via fluid exsolution from shallowly emplaced, highly evolved igneous complexes generated mainly as mantle melts. However, the giant Donlin Creek orogenic gold deposit is a product of either metamorphic devolatilization deep in the basin or of a gold-bearing fluid released from a flysch-melt igneous body.

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Additional publication details
Publication type	Report
Publication Subtype	USGS Numbered Series
Title	Geology and origin of epigenetic lode gold deposits, Tintina Gold Province, Alaska and Yukon
Series title	Scientific Investigations Report
Series number	2007-5289
Chapter	A
DOI	10.3133/sir20075289A
Year Published	2007
Language	English
Publisher	U.S. Geological Survey
Publisher location	Reston, VA
Contributing office(s)	Eastern Mineral Resources Science Center, Eastern Mineral and Environmental Resources Science Center
Description	iii, 18 p.
Larger Work Type	Report
Larger Work Subtype	USGS Numbered Series
Larger Work Title	Recent U.S. Geological Survey studies in the Tintina Gold Province, Alaska, United States, and Yukon, Canada— Results of a 5-year project (Scientific Investigations Report 2007-5289)
Country	Canada, United States
State	Alaska, Yukon
Other Geospatial	Tintina Gold Province
Google Analytic Metrics	Metrics page