Mineral Assemblages from the Mountain Pass REE Deposit for Age Determination
Faculty Mentor
Chad Pritchard
Presentation Type
Poster
Start Date
May 2025
End Date
May 2025
Location
PUB NCR
Primary Discipline of Presentation
Geosciences
Abstract
Sulfide Carbonatites from the Mountain Pass Rare Earth Mine in eastern California have greatly interested geologists since the 1950's and are critical for US economic development. Due to the critical nature of these deposits, it is paramount to understand how REE from within the US (and around the world), hence the need for more detailed age dating and mineral analyses. Samples from the REE mine are composed of large quantities of bastnasite, monazite, calcite, barite, and dolomite. These mineral assemblages are unique and do not contain minerals that are commonly used for age determination. From the REE deposit, minerals of interest in this separation are bastnasite and monazite. Based on previous bastnasite ages, the deposits are 1,370 Ma to 1,380 Ma (Castor, 2008). As part of the EWU-USGS cooperative samples were processed at EWU campus in collaboration with the USGS to separate out the desired minerals. Representative samples were crushed in a specialized rock crusher, sieved to an appropriate grain size, then ran through a Frantz magnetic separation machine. The mineral grains were then picked under a microscope and returned to the USGS for analysis.
Recommended Citation
Herman, Logan and Pritchard, Chad, "Mineral Assemblages from the Mountain Pass REE Deposit for Age Determination" (2025). 2025 Symposium. 10.
https://dc.ewu.edu/srcw_2025/ps_2025/p2_2025/10
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Mineral Assemblages from the Mountain Pass REE Deposit for Age Determination
PUB NCR
Sulfide Carbonatites from the Mountain Pass Rare Earth Mine in eastern California have greatly interested geologists since the 1950's and are critical for US economic development. Due to the critical nature of these deposits, it is paramount to understand how REE from within the US (and around the world), hence the need for more detailed age dating and mineral analyses. Samples from the REE mine are composed of large quantities of bastnasite, monazite, calcite, barite, and dolomite. These mineral assemblages are unique and do not contain minerals that are commonly used for age determination. From the REE deposit, minerals of interest in this separation are bastnasite and monazite. Based on previous bastnasite ages, the deposits are 1,370 Ma to 1,380 Ma (Castor, 2008). As part of the EWU-USGS cooperative samples were processed at EWU campus in collaboration with the USGS to separate out the desired minerals. Representative samples were crushed in a specialized rock crusher, sieved to an appropriate grain size, then ran through a Frantz magnetic separation machine. The mineral grains were then picked under a microscope and returned to the USGS for analysis.
