Dating of Igneous Dike, Eastern Uinta Mountains

Abstract

Age of a gabbroic dike which intrudes the Precambrian metasediments of the Uinta Mountains in T. 1 S., Rs. 18 and 19 E. , Uintah County, Utah, has been determined by the K-Ar method. Analyses of the whole rock and a feldspar concentrate from it were run. The whole-rock determination gave an age of 412 ± 17 my and the feldspar concentrate 453 ± 17 my. The whole-rock determination would place the age in the uppermost Silurian; the feldspar concentrate determination would place the age as medial to uppermost Ordovician. Geochron Laboratories Division of Krueger Enterprises, Inc., Cambridge, Massachusetts, who performed the analyses, commented that this rock is at least lower Paleozoic in age, and almost certainly it is pre-Devonian.