Geological Society of America Bulletin
Rb-Sr isochron data from whole-rock samples of dolerite and metadolerite indicate emplacement of dikes 2,826 ± 58 m.y. ago, during formation of the Bighorn gneiss and granitic complexes. Whole-rock samples of other dolerite dikes and mineral separates mark another intrusive event at 2,200 ± 35 m.y. B.P., well after the regional metamorphism. Two episodes of mafic dike emplacement are consistent with field relations but are not in agreement with recent K-Ar age determinations.
Stueber, Alan M.; Heimlich, Richard; and Ikramuddin, Mohammed (1976). Rb-Sr Ages Of Precambrian Mafic Dikes, Bighorn Mountains, Wyoming. Geological Society of America Bulletin 87, 909-914. Retrieved from http://digitalcommons.kent.edu/geolpubs/11