2024 Undergraduate Research Showcase

Assessing the Accuracy and Precision of LA-ICP-MS Compared to SEM Analyses for Feldspar Characterization

Document Type

Student Presentation

Presentation Date


Faculty Sponsor

Dr. Darin Schwartz


As part of a larger study to better understand the tectonic history of western Idaho, we have studied the reliability of laser ablation inductively coupled mass spectrometry (LA-ICP-MS) to characterize the major cation composition of feldspar. Feldspar is a common rock forming mineral composed of three phases with differing major cation proportions, internal textures, and isotopic composition, all reflective of its formation conditions. The major cation proportions need to be quantified in order to contextualize more advanced classifications. Feldspar samples were collected from various intrusive igneous rocks within the Salmon River Canyon. These samples were then analyzed by Scanning Electron Microscopy (SEM), and those same sample spots were reanalyzed by LA-ICP-MS, then compared. We hypothesized that major cations determined by LA-ICP-MS would be < 5% different than those derived by SEM. However, we found that on average there are significant discrepancies between the results obtained by SEM and LA-ICP-MS. We discuss how these discrepancies are likely attributed to issues such as fractured mineral grains, spot size inconsistency over fine-scale compositional zonations, and technical limitations leading to human error. To overcome these limitations, we further assess precision and accuracy between the two techniques using mineral standards with known and more homogeneous compositions.

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