Second generation ‘diamond-in-water’ ablation – a step forward in trace element and isotopic composition analysis

Abstract

A second generation diamond-in-water laser ablation system combined with mass spectrometry measurements is presented for trace elements and radiogenic isotopic analyses of microinclusion-bearing diamonds. Ablation was conducted using a Nd: YV04 laser (532 nm, 136 µJ/pulse, 25 ns pulse duration, 2000 Hz repetition rate) in a closed ultra-clean glass cuvette filled with milli-Q water (18.2 MΩ cm). Multiple experiments indicate a highly stable and precise ablation process that proceeded at an average rate of 0.75 ± 0.41 mg/h. Triple Quadrupole inductively coupled plasma mass spectrometer (ICP-MS) trace element analyses of the ablated material reveal primitive mantle normalized patterns that are similar to previously analyzed microinclusion-bearing diamonds. Results comparable with previous ablation analyses of individual diamonds, and results of BHVO-2G and BCR-2G standards determined using this new ablation technique confirm its accuracy. Furthermore, the reference material results provide a means to estimate the uncertainty for the elemental concentrations in the diamonds, suggesting that it is generally below 10% for most elements of interest, and likely under 15% for all elements. The new ablation system produces enough material for successful Sr, Nd, and Pb isotope analyses by combined wet-chemistry and thermal ionization mass spectrometer (TIMS) using 10¹¹ or 10¹³ Ω resistors. The Sr–Nd–Pb isotope values of BHVO-2G and BCR-2G ablated, purified using ion chromatography and measured by the same technique validate its accuracy. Low total procedural blank levels (Sr average of 71 ± 21 pg; Nd of 0.42 ± 0.25 pg Nd; Pb of 9.4 ± 3.6 pg) have little impact on the measured isotope values, but a blank correction can be applied if necessary.