Geochronologic, Isotopic, and Geochemical Data from Igneous Rocks in the Lane Mountain Area, San Bernardino County, California

Open-File Report 2019-1070
By: , and 

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Abstract

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.

Suggested Citation

Stone, P., Brown, H.J., Cecil, M.R., Fleck, R.J., Vazquez, J.A., Fitzpatrick, J.A., and Rosario, J., 2019, Geochronologic, isotopic, and geochemical data from igneous rocks in the Lane Mountain area, San Bernardino County, California: U.S. Geological Survey Open-File Report 2019–1070, 34 p., https://doi.org/10.3133/ofr20191070.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Geographic Setting
  • Previous Investigations and General Geologic Framework
  • Purpose and Scope
  • Methods
  • Results
  • Discussion
  • Summary
  • Acknowledgments
  • References Cited
  • Figures and Tables

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Geochronologic, isotopic, and geochemical data from igneous rocks in the Lane Mountain area, San Bernardino County, California
Series title Open-File Report
Series number 2019-1070
DOI 10.3133/ofr20191070
Year Published 2019
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Geology, Minerals, Energy, and Geophysics Science Center
Description 34 p.
Country United States
State California
County San Bernardino County
Online Only (Y/N) Y