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Open-File Report 2012–1117

Constraining the Location of the Archean–Proterozoic Suture in the Great Basin Based on Magnetotelluric Soundings

By Brian D. Rodriguez and Jay A. Sampson

Thumbnail of and link to report PDF (17.6 MB)Abstract

It is important to understand whether major mining districts in north-central Nevada are underlain by Archean crust, known to contain major orogenic gold deposits, or, alternatively, by accreted crust of the Paleoproterozoic Mojave province. Determining the location and orientation of the Archean-Proterozoic suture zone between the Archean crust and Mojave province is also critical because it may influence subsequent patterns of sedimentation, deformation, magmatism, and hydrothermal activity. In the Great Basin, the attitude of the suture zone is unknown because it is concealed below cover. A regional magnetotelluric sounding profile along the Utah-Nevada State line reveals a deeply penetrating, broad electrical conductor that may be the Archean-Proterozoic suture zone in the northwest corner of Utah. This major crustal conductor’s strike direction is northwest, where it broadens to about 80 km wide below about 3-km depth. These results suggest that the southwestern limit of intact Archean crust in this part of the Great Basin is farther north than previously reported. These results also suggest that the major gold belts in north-central Nevada are located over the Paleoproterozoic Mojave province, and the Archean terrain lies northeast in the northwest corner of Utah. Rifted Archean crust segments south and west of the suture suggest that future mineral exploration northeast of current mineral trends may yield additional gold deposits.

First posted June 27, 2012

For additional information contact:
Director, Crustal Geophysics and Geochemistry Science Center
U.S. Geological Survey
Box 25046, Mail Stop 964
Denver, CO 80225
http://crustal.usgs.gov/

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Suggested citation:

Rodriguez, B.D., and Sampson, J.A., 2012, Constraining the location of the Archean–Proterozoic suture in the Great Basin based on magnetotelluric soundings: U.S. Geological Survey Open-File Report 2012–1117, 30 p.



Contents

Abstract

Introduction

Electrical Rock Properties

Magnetotelluric Method

Magnetotelluric Survey

Resistivity Modelling

Geologic Correlations

Results

Discussion

Summary and Conclusions

References Cited

Appendix 1. Magnetotelluric Data


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