Age of Laramide porphyries near Leadville, Colorado; Article 87
Pearson, Robert C; Tweto, Ogden L; Stern, Thomas W; Thomas, Herman H (1962) Age of Laramide porphyries near Leadville, Colorado; Article 87. U. S. Geological Survey Professional Paper, Report: P 0450-C, pp.C78-C80, 1962
| Authors | Pearson, Robert C; Tweto, Ogden L; Stern, Thomas W; Thomas, Herman H |
|---|---|
| Year | 1962 |
| Title | Age of Laramide porphyries near Leadville, Colorado; Article 87 |
| Source | U. S. Geological Survey Professional Paper, Report: P 0450-C, pp.C78-C80, 1962 |
| ISSN | 1044-9612 |
| GeoRef | 1962-008326 |
| Keywords | absolute age; Colorado; dates; geochronology; granites; granitic composition; igneous rocks; Lake County Colorado; Leadville area; plutonic rocks; porphyries; United States; USGS |
Abstract
K-Ar ages on biotite from the successive Pando, Johnson Gulch, and Lincoln porphyries are 70, 41, and 64 m. y. respectively, and granodiorite from the northern Sawatch Range gives 70 m. y. The Pando, Lincoln, and granodiorite ages are believed reliable, and the aberrant Johnson Gulch age is believed due to later heating duringmineralization or intrusion.