Skip to main content
U.S. flag

An official website of the United States government

Reconnaissance geology, mineral occurrences, and geochemical anomalies of the Yentna district, Alaska

January 1, 1968

The Yentna district, in south-central Alaska, is underlain by slightly metamorphosed Mesozoic sedimentary rocks, and by sandstones, conglomerates and coaly minerals of the Tertiary Kenai Formation. The bedrock is locally covered by extensive surficial deposits of Quaternary and Recent (Holocene) age. The Mesozoic strata are cut by a quartz monzonite batholith in the Tokositna Mountains and by alaskitic dikes and plugs in the Peters and Dutch Hills. A silica-carbonate dike, which formed by alteration of a mafic or ultramafic dike, was noted in the Peters Hills.

The major ore deposits are gold placer deposits of several types, including stream and bench deposits of Recent (Holocene) age, glacial-fluviatile deposits of Quaternary age, and conglomerates of Tertiary age. Quartz-rich conglomerates and breccias have also been productive and are interesting and controversial genetically. The present study indicates that they are closely related to shear zones containing quartz veins and highly altered rocks; previously the origin of the associated altered rocks had been ascribed to deep weathering.

The report also contains descriptions of a few gold lode prospects and of geochemically anomalous areas such as those at Bunco Creek and near Mount Goldie.

Publication Year 1968
Title Reconnaissance geology, mineral occurrences, and geochemical anomalies of the Yentna district, Alaska
DOI 10.3133/ofr6835
Authors Allen L. Clark, C. C. Hawley
Publication Type Report
Publication Subtype USGS Numbered Series
Series Title Open-File Report
Series Number 68-35
Index ID ofr6835
Record Source USGS Publications Warehouse
Was this page helpful?