We present new geochronologic, isotopic, and geochemical data for selected igneous rocks in the Lane Mountain area, California. We determined SHRIMP-RG U-Pb zircon ages for the following units: (1) Larrea complex (~253 Ma and ~149–146 Ma); (2) Daisy granodiorite (~151 Ma); (3) Jack Spring quartz monzonite (~85–82 Ma); (4) unnamed porphyritic dikes and stocks (~80–73 Ma); and (5) Lane Mountain volcanics (~22 Ma). These results confirm and refine previous age determinations for the Larrea complex, Jack Spring quartz monzonite, and Lane Mountain volcanics, and provide the first reliable ages for the Daisy granodiorite and the unnamed porphyritic rocks. Sri of the plutonic rocks increases from ~0.704 to ~0.705–0.706 to ~0.708–0.709 for samples dated as ~250, ~150, and ~85–70 Ma, respectively, which indicates progressively greater involvement of Precambrian continental lithosphere in magma generation through time. The Sri and geochemical data suggest that the most significant change in magmatic source occurred between ~150 and 85 Ma.
Citation Information
| Publication Year | 2019 |
|---|---|
| Title | Geochronologic, isotopic, and geochemical data from igneous rocks in the Lane Mountain area, San Bernardino County, California |
| DOI | 10.3133/ofr20191070 |
| Authors | Paul Stone, Howard J. Brown, M. Robinson Cecil, Robert J. Fleck, Jorge A. Vazquez, John A. Fitzpatrick, Jose J. Rosario |
| Publication Type | Report |
| Publication Subtype | USGS Numbered Series |
| Series Title | Open-File Report |
| Series Number | 2019-1070 |
| Index ID | ofr20191070 |
| Record Source | USGS Publications Warehouse |
| USGS Organization | Geology, Minerals, Energy, and Geophysics Science Center |
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