Skip to main content
Skip to main content

Overview

Aeromagnetic map centered over the carbonatite deposit at Mountain Pass, California. The deposit is right along the edge of a magnetic high that may be associated with the carbonatite.
Aeromagnetic map centered over the carbonatite deposit at Mountain Pass, California. The deposit is right along the edge of a magnetic high that may be associated with the carbonatite.

As a result of the increasingly high-demand for rare earth elements in emerging technologies and the reduction of rare earth element exports from China, there is a growing national focus on rare earth element deposits. In an effort to better understand domestic resource potential, the USGS is investigating the genetic relationship among three rare earth element deposits in the southeast Mojave Desert: Music Valley (Pinto Mountains, California), Thor (New York Mountains, Nevada), and the world-class rare earth element deposit at Mountain Pass, California. Such a combined study would significantly improve our knowledge of rare earth element deposits in this unusual extensional terrane that includes the largest rare earth element deposit in the U.S.

Research focuses on understanding one of the largest carbonatite deposits in the world and the search for similar deposits in the surrounding permissive Proterozoic terranes of southeast California. Knowledge gained will fill gaps in our understanding of the nature, structure, age, and genesis of these unusual rare earth element deposits. Typical studies include gravity, magnetic, electromagnetic, radiometric, possibly LiDAR, and gravity gradiometry methods. Carbonatite deposits typically have prominent geophysical signatures that include gravity, magnetic, and radiometric anomalies. In addition, geophysical studies may yield insights on through-going or possibly reactivated geologic features that might control these mineral deposits. Thus, an investigation of these unusual rare earth element deposits will likely provide new insights on their setting and genesis. These methods and techniques are applicable to the investigation of other domestic or global rare earth element deposits.

Top

Project Activities

ASTER image of the Mountain Pass area showing the carbonatite deposit and the outline of Precambrian igneous and metamorphic rocks.
ASTER image of the Mountain Pass area showing the carbonatite deposit and the outline of Precambrian igneous and metamorphic rocks.

Geophysical Investigations

Contact: Kevin Denton, kmdenton@usgs.gov

We will conduct gravity, magnetic, radiometric, and magnetotelluric investigations of the southeast Mojave Proterozoic terrane for possible rare earth element deposits. In particular, we plan to integrate studies of the Mountain Pass deposit (Ponce et al., 2013; Denton et al., 2014) with results from the Music Valley and Thor deposits and determine their relationship to hydrothermal alteration events that encompassed the region.

Geologic Investigations

Contact: David Miller, dmiller@usgs.gov

We will conduct detailed geologic mapping of the Mountain Pass and surrounding area to determine the lithotectonic framework and alteration history of the region by completing the Proterozoic parts of the Mescal Range and Clark Mountain 7.5’ quadrangles. These studies will be integrated with past geologic studies at the Thor deposits to derive a comprehensive geologic, structural, and alteration history of greater Ivanpah Valley region. We will study and integrate the geologic mapping of the Music Valley and Thor rare earth element deposits and evaluate patterns of intrusion and alteration.

Geochronology / Geochemistry Investigations

Contacts: Wayne Premo, wpremo@usgs.gov, and Kathyn Watts, kwatts@usgs.gov

We will use high-resolution analytical tools (electron microprobe, SEM, SHRIMP-RG, SIMS) to obtain geochemical, isotopic and geochronologic measurements within melt inclusions. Analyzing sequentially trapped melt inclusions along U-Pb dated core to rim zircon growth domains will allow reconstruction of discrete time slices in magmatic evolution that would be impossible to resolve through time-integrated whole-rock records. These new age data, trace-element characteristics, and isotopic fingerprinting can map the various stages of regional alteration and make a new geochemical template for the formation of these rare earth element deposits.

Remote Sensing Investigations

Contact: John Mars, jmars@usgs.gov

We will use AVIRIS, HyTES and WorldView-3 in conjunction with a regional ASTER mineral map (Mars, 2014) to map carbonatites and minerals typically associated with hydrothermally-altered rocks such as alunite, kaolinite, sericite (white mica), chlorite-epidote, and hematite-goethite at Mountain Pass, Thor, and Music Valley in the southeast Mojave Desert. Spectral measurements of rare earth element-bearing minerals indicate that subtle variations in the shapes and wavelength positions of individual Lanthanide element absorptions are controlled by mineralogy (Swayze et al., 2013). Analytical results will be used to create mineral maps of rare earth element-bearing mineral phases.

Top

Products

Reports

Mars, J.C., 2013, Hydrothermal alteration maps of the central and southern Basin and Range province of the United States compiled from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data (ver. 1.1, April 8, 2014): U.S. Geological Survey Open-File Report 2013–1139, 5 p., 13 plates, scale 1:1,300,000, http://dx.doi.org/10.3133/ofr20131139.

Ponce, D.A., Denton, K.M., and Miller, D.M., 2013, Geophysical expression of a carbonatite terrane in the eastern Mojave Desert, California in Parmentier, P., (ed.), Eastern Mojave Desert Earth Resources-Then and Now, 40th Annual South Coast Geological Society Field Trip, October 4-6, 2013, p. 149-156. [PDF file, 1.7 MB]

Poster / Presentation Abstracts

Denton, K.M., Ponce, D.A., and Miller, D.M., Peacock, J., and Miller, J.T., 2015, Geophysical Investigations of a Proterozoic Carbonatite Terrane, southeast Mojave Desert, California: Eos (Transactions, American Geophysical Union), v. 95, no. 53, Abstract GP13B-1293 presented at 2015 Fall Meeting, AGU, San Francisco, Calif., 14-18 Dec. View Denton 2015 AGU abstract.

Denton, K.M., Ponce, D.A., and Miller, D.M., 2012, Regional geophysical expression of a carbonatite terrane in the eastern Mojave Desert: Eos (Transactions, American Geophysical Union), v. 93, no. 53, Abstract GP43B-1136 presented at 2012 Fall Meeting, AGU, San Francisco, Calif., 3-7 Dec. View Denton 2012 AGU abstract.

Denton, K.M., Ponce, D.A., Miller, D.M., and Jernigan, C.T., 2014, Regional gravity and magnetic anomalies related to a Proterozoic carbonatite terrane in the eastern Mojave Desert, California: Abstract GP33A-3688 presented at 2014 Fall Meeting, AGU, San Francisco, Calif., 15-19 Dec. View Denton 2014 AGU abstract.

Denton, K.M., Ponce, D.A., Miller, D.M., and MacPherson-Krutsky, C., 2013, Carbonatite: A geophysical investigation of a rare earth element terrane, eastern Mojave Desert, California: Eos (Transactions, American Geophysical Union), v. 94, no. 53, Abstract GP51C-1092 presented at 2013 Fall Meeting, AGU, San Francisco, Calif., 9-13 Dec. View Denton 2013 AGU abstract.

Hoefen, T.M., Livo, K.E., Swayze, G.A., Giles, S.A., Van Gosen, B.S., Emsbro, P., and Karst, A., 2013, Spectroscopic investigations of REE hosted heavy mineral sand and phosphates: Geological Society of America Abstracts with Program, v. 45, no. 7, p. 278. View Hoefen 2013 GSA abstract.

Mars, J.C., 2013, Spectral features of the Khanneshin carbonatite volcano, Afghanistan: Geological Society of America Abstracts with Program, v. 45, no. 7, p. 278. View Mars 2013 GSA abstract.

Swayze, G.A., Pearson, N., Wilson, S., Benzel, W.M., Clark, R.N., Hoefen, T.M., Van Gosen, B.S., Adams, M., and Reitman, J., 2013, Spectrally distinguishing between REE-bearing minerals based on differences in their crystal field f- f transition absorptions: Geological Society of America Abstracts with Program, v. 45, no. 7, p. 278. View Swayze 2013 GSA abstract.

Top

The use of firm, trade, and brand names is for identification purposes only and does not constitute endorsement by the U.S. government.

Download if needed: Excel Viewer | PDF Reader | Powerpoint Viewer | Word Viewer