K-Ar LASER ABLATION DATING OF CLAY MINERALS WITH LASER-INDUCED BREAKDOWN SPECTROSCOPY (LIBS) AND MASS SPECTROMETRY

Accurately dating clay minerals is crucial for unraveling Earth's geological history and understanding various processes that have shaped our planet. The K-Ar laser ablation dating technique, which combines laser-induced breakdown spectroscopy (LIBS) with noble gas mass spectrometry, has recently emerged as a powerful tool in the field. It allows simultaneous measurement of potassium (via LIBS) and argon in the same sample.

To analyze clay minerals, they must be separated into different grain sizes, which typically results in obtaining small quantities, usually in the milligram range, for each fraction. This is the main problem in conventional K-Ar dating because it often requires large sample sizes. In this study, we present a novel approach to date illites using K-Ar laser ablation dating. We employ a powder-deposited-on-glass-discs preparation technique. This method offers several advantages, including increased ease, speed, cost-effectiveness, and the opportunity to analyze the same sample using X-ray diffraction.

LIBS is particularly well-suited for analyzing clay minerals due to its minimal sample preparation requirements and ability to detect multiple elements simultaneously, enabling precise measurement of potassium content within the mineral structure. This capability is essential for K-Ar dating, as accurate potassium measurements are critical for determining the age of clay mineral samples.

We conducted several experiments on four groups of rocks with different mineral compositions and age ranges, previously determined by other dating methods. The primary objective of these experiments was to determine the optimal laser ablation conditions, including laser energy, frequency, hole diameter, and depth, as well as to verify the suitability of each sample's texture for successful measurements. Once this information was gathered and the appropriate conditions were determined, we tested samples with unknown ages.

The results were successful, demonstrating the potential of LIBS in enhancing the accuracy and efficiency of K-Ar laser ablation dating. Our research aims to revolutionize K-Ar dating by introducing an innovative and streamlined sample preparation method that overcomes the limitations of previous techniques.