Potassium Isotope Ratios (δ41K) of Eighteen Chinese Rock Reference Materials

Abstract

Potassium isotope ratios (δ⁴¹K) were determined for eighteen Chinese geological reference materials (RMs, GSR series) encompassing igneous, metamorphic and sedimentary rocks. K₂O mass fractions (w) ranged between 0.15 and 7.5% in these RMs. Measurements were conducted using a collision cell MC-ICP-MS with sample-standard bracketing technique. The intermediate precision of K isotopic determination, based on measurement results collected over 2.5 years, was 0.04‰ (2s, n = 69) for in-house GSB K solution and 0.05‰ (2s, n = 63) for basaltic RM BCR-2. The accuracy of our data was assessed by comparison with previously published data and/or utilising two or three different measurement procedures. The high-precision δ⁴¹K values for these eighteen RMs span a wide range from -1.15‰ (GBW07122, GSR 15, amphibolite) to 0.28‰ (GBW07120, GSR 13, limestone), and data for six RM are presented for the first time, making them valuable references for quality assurance and inter-laboratory comparisons.