Analysis of fluid inclusion leachates from quartz by ion chromatography

Abstract 20 chemical species have been detected and quantified in standard solutions using a Dionex 2000i-SP ion Chromatograph. These species are (minimum detection limits in ppb in injected sample follow each species; anions and cations listed in order of increasing retention time): F − (14), CH 3 COO − (12), HCOO − (4), Cl − (6), NO − 2 (9), Br - (19), NO − 3 (16), HPO 2− 4 (28), SO 2− 4 (26), C 2 O 2− 4 oxalate (250), I − (20), Li + (0.5), Na + (0.7), NH + 4 (0.6), K + (1.6), Rb + (3.5), Cs + (5.9), Mg 2+ (5), Ca 2+ (15) and Sr 2+ (100). A technique has been developed to clean fluid inclusion-bearing samples and obtain fluid inclusion leachates by hand crushing ~1–2 g samples under leaching solutions in an agate mortar and then separating the leachates by vacuum filtration. High-efficiency ion removal from the crushed sample is required since gas Chromatographic H 2 O analyses of sample splits have been used to calculate species concentrations in fluid inclusions. Three separate crushes using different leaching solutions are required for a complete analysis. Cleaning procedures have been established for all components involved in the crush/leach procedure, and a system blank has been obtained by crush/leach analysis of heat-treated Brazilian quartz. The contact time between the leachate and the component (i.e., agate mortar) has been established as an important control on blank levels. The technique has been applied to three samples from the Tanco granitic pegmatite: the analyses show both a ‘pegmatitic’ and a possibly external fluid component. A combined, single sample, gas and ion Chromatographic procedure has been developed to link directly the fluid inclusion volatile and leachate data.