In-situ laser K Ar dating of Archean feldspar by using laser-induced breakdown spectroscopy - Mass spectrometry technique

Recent reconsideration of potassium‑argon (K Ar) dating has emerged due to challenges associated with neutron irradiation of samples, which constrain the applicability of 40 Ar/ 39 Ar dating methods. This reconsideration is driven by increasing demands for chronological data in studies related to climate evolution, environmental changes and resources exploration. Furthermore, the in-situ K Ar dating technique has garnered considerable interest, especially following the advent of laser-induced breakdown spectroscopy (LIBS) in deep-space exploration missions. In the present study, we developed a custom laser spectroscopy-mass spectrometry system designed to perform in-situ K Ar dating. A series of reference minerals were employed to establish a calibration curve for quantifying potassium content in geological samples. Additionally, a K Ar dating standard mineral with a precisely calibrated radiogenic 40 Ar ⁎ concentration was utilized to evaluate the sensitivity of the quadrupole mass spectrometer (QMS) and to subsequently determine the argon content within the samples. Comparative analysis between the internal normalization method and the peak intensity method for potassium (K) quantification revealed that the internal normalization approach generally yielded superior results across most samples. However, for samples exhibiting elevated concentrations of potassium, iron, or magnesium, the peak intensity method demonstrated enhanced effectiveness relative to the internal normalization technique. The accuracy of the in-situ K Ar dating method fundamentally depends on the determination of K content via LIBS, underscoring the necessity of employing a suite of matrix-matched standards to ensure precise and reliable measurements.