Age and origin of the Darrough Felsite, southern Toiyabe Range, Nevada

Journal of Research of the U.S. Geological Survey
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Abstract

The name Darrough Felsite was originally assigned to a body of fine-grained quartzofeldspathic igneous rock probably greater than 3 km thick that is exposed continuously over 100 km2 in the southern Toiyabe Range of central Nevada. The Darrough was supposed to consist mostly of intrusive rocks of probable Permian age. Reexamination of parts of the Darrough Felsite indicates that it is Tertiary and has no genetic affiliation to pre-Tertiary sedimentary and volcanic rocks of the Toiyabe Range. The Darrough constitutes an enormously thick succession of crystal-lithic tuff, tuff breccia, crystal tuff, and volcanogenic sedimentary breccia and sandstone. The tuffaceous rocks are strongly compacted where ash particles are the dominant constituent but are much less compacted where lithic fragments and crystals constitute a rigid framework. Much of the Darrough Felsite may have undergone extensive siliciflcation, probably as a postcompaction event. Contact relations of the Darrough Felsite indicate that it is younger than pre-Tertiary rocks of the southern Toiyabe Range and the Ophir pluton, here dated at 53.9 m.y. (K-Ar, biotite). Three K-Ar ages of minerals from tuff of the Darrough are 26.1, 22.7, and 22.3 m.y., suggesting a middle Tertiary age. A large dike intruding the Darrough. previously assigned a Jurassic age, gives a K-Ar-biotite age of 29.4 m.y. We tentatively interpret the Darrough Felsite to represent an accumulation of ash and breccia flows in a volcanotectonic depression.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Age and origin of the Darrough Felsite, southern Toiyabe Range, Nevada
Series title Journal of Research of the U.S. Geological Survey
Volume 4
Issue 1
Year Published 1976
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Description 7 p.
First page 75
Last page 81
Country United States
State Nevada
Other Geospatial Toiyabe Range
Online Only (Y/N) N
Additional Online Files (Y/N) N