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GEOREF RECORD

Direct dating of mineralization at Goldfield, Nevada, by potassium-argon and fission-track methods

R. P. Ashley and M. L. Silberman
Direct dating of mineralization at Goldfield, Nevada, by potassium-argon and fission-track methods
Economic Geology and the Bulletin of the Society of Economic Geologists (August 1976) 71 (5): 904-924

Abstract

Potassium-argon dating of hypogene alunite and K-mica from hydrothermally altered rocks at Goldfield, Nevada, yields mineralization ages of 20 to 21 m.y., in good agreement with a mineralization age established by potassium-argon dating of unaltered premineralization and postmineralization volcanic units. Premineralization volcanic units that are pervasively propylitized cannot be dated by the potassium-argon method but yield zircon fission-track ages, and in several cases yield concordant apatite fission-track ages. Two samples from premineralization units yield apatite ages concordant with the age of mineralization established by potassium-argon geochronometry, reflecting annealing of the apatite during the hydrothermal episode.Potassium-argon dating of supergene alunite samples yields imprecise ages in the range 9 to 12 m.y. that probably record the first exposure of their hydrothermally altered host rocks to oxidizing conditions. Potassium-argon dating of postmineralization basalts and silicic tuffs interbedded with conglomerates bearing altered rock clasts shows that the altered area was eroded nearly to present topographic levels by 11 m.y. ago, at which time it was covered by basalt flows now represented only by scattered remnants. Apatites from premineralization volcanic units give fission-track ages of 20 m.y. or more, indicating that no significant thermal event has affected altered rocks at Goldfield since mineralization took place.


ISSN: 0361-0128
EISSN: 1554-0774
Coden: ECGLAL
Serial Title: Economic Geology and the Bulletin of the Society of Economic Geologists
Serial Volume: 71
Serial Issue: 5
Title: Direct dating of mineralization at Goldfield, Nevada, by potassium-argon and fission-track methods
Affiliation: U. S. Geol. Surv., Menlo Park, Calif., United States
Pages: 904-924
Published: 197608
Text Language: English
Publisher: Economic Geology Publishing Company, Lancaster, PA, United States
Accession Number: 1977-008154
Categories: Geochronology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. tables, geol. sketch maps
N36°55'60" - N38°28'00", W118°28'00" - W117°10'00"
N36°00'00" - N39°07'60", W118°15'00" - W115°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Society of Economic Geologists
Update Code: 1977
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