HIGH-PRECISION IN SITU OXYGEN ISOTOPE ANALYSIS OF QUARTZ USING AN ARF LASER - A STORY OF PARTIAL MELTING AND CRYPTIC METASOMATISM IN THE MANTLE

Abstract

High precision in situ oxygen isotope analyses of quartz using an ArF laser are described. The high precision is documented by comparing in situ ArF laser data with CO2 laser and conventional analyses of silica and quartz. In contrast to the CO2 and Nd:YAG laser, no oxygen isotope fractionation occurs during in situ ablation of quartz with high power ultra-violet ArF laser light pulses. Therefore, high oxygen yields are no prerequisite for accurate and precise δ18O measurements. No data correction are necessary when analyzing quartz. The high spatial resolution and in situ capabilities of the ArF laser technique are demonstrated by analyzing hydrothermally precipitated quartz, which shows a rhythmic growth history. A model is also presented that explains the behavior of quartz during ablation with ultra-violet laser.