Summary of potassium/argon age dating, 1980

A significant improvement in efficiency of the K-Ar laboratory was brought about by completion of a second extraction line. Two extractions can now be done routinely each day and the Ar spike ratios of the new table will permit dating of much younger samples than previously. Extensive K-Ar dating of samples from the Mineral Mountains shows intervals of silicic volcanism at 0.5, 0.8, and 7.5 m.y. K-Ar dating of plutonic units does not present a consistent picture, however. Plutonic events 35 to 40 m.y., 29 m.y. and 19 to 21 m.y. ago are suggested but interpretation must be considered preliminary. Joint programs with the US Geological Survey now underway to study the Rb-Sr and U-Pb systematics of the Mineral Mountains pluton should aid in unravelling its history. Dating of basalts from the Cove Creek Domes/Twin Peaks area, Utah, aided in delineating the timing of basaltic volcanism. This adds to the already extensive data on the chronology of volcanic activity in the area.