37 D1. Recent Advances in Geoscience and Geoscience Education (Posters)

Friday, 17 May 2024
9:00 AM - 1:30 PM
Grand Ballroom

A THEORETICAL GEOPHYSICAL ANALYSIS OF A SUBSURFACE CARBONATITE BODY AT MOUNTAIN PASS, CA

Paper number: 37-4
Program: Technical Sessions
Time: 9:00 AM – 1:30 PM

Authors

  • Erin Toulou Presenting Author
    Eastern Washington University, Cheney, WA
  • Geoff Phelps
    Geology, Minerals, Energy, and Geophysics Science Center, Moffett Field, CA
  • Kathryn E. Watts
    Geology, Minerals, Energy, and Geophysics Science Center, Spokane, WA

Abstract

The Mountain Pass mine in California is one of the world's largest mass producers of light rare earth elements (REEs). These REEs are essential components for green energy and defense technologies. Neodymium and praseodymium are currently the most economically important REEs extracted from the mine and are used in high-strength magnets. A carbonatite stock hosts the REE ore at Mountain Pass and is an irregularly shaped intrusion that generally strikes north and dips steeply (30-60 degrees) to the west. The ore body is dissected by faults, including a large N50W left-lateral fault (Celebration fault) that bisects the stock, displacing the southern part of the ore body to the southeast and the northern part of the ore body to the northwest. It is unknown whether the ore body is fault-repeated elsewhere in the subsurface, which is vital for identifying minable resources. We are determining if it is possible to detect the existence of possible fault-offset portions of the carbonatite body near the Mountain Pass mine using gravity data. If it is possible, this would allow us to detect additional subsurface carbonatite bodies within the same area. For simplicity, we model the irregular-shaped carbonatite body as a sphere and vary the sphere’s size, depth, and density contrast with the surrounding country rock to understand relevant conditions for detection. Based on field experience, we estimate that a subsurface carbonatite body should be detectable if it produces a gravity anomaly with an amplitude of >+1 milligal (mGal). If the amplitude ranges between +0.5 to +1 mGal, it is possible but challenging to detect. Using estimates of the known carbonatite’s density and volume, we determined that additional carbonatite bodies with a density contrast of +0.3 g/cm3 and a radius of 200 m are detectable at a depth of 50 m, and possibly detectable at a depth of up to 150 m.

Geological Society of America Abstracts with Programs. Vol. 56, No. 4

doi: 10.1130/abs/2024CD-399832

© Copyright 2024 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.