Trace element determination of single fluid inclusions by laser ablation ICP-MS: applications for halites from sedimentary basins

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to determine Ca, Sr and Rb in individual natural fluid inclusions in halite. Artificial fluid inclusions made in glass microcapillary tubes were used to quantify the data. An Nd:YAG laser operating at 266 nm was focused and fired in Q-switched mode on 20-30 mu m diameter spots on the microcapillary tubes until the fluid was reached. The standard fluid was ablated and transported with argon to the ICP-MS. Analytes in fluid inclusions in the halite were determined using calibration curves obtained from standard solutions in the microcapillaries. Uncertainties in the analysis of individual fluid inclusions ranged from 4% to 20% RSD for samples from the Palo Duro and Paradox Basins in Texas and Utah, respectively. Ca and Sr in halite from the Palo Duro Basin ranged from 95 to 1028 ppm and from 6.7 to 607 ppm, respectively. Halite from the Paradox Basin contained fluid inclusions with 124 to 178 ppm Ca and 14 to 108 ppm Sr. In all inclusions, Ca had the highest concentration, followed by Sr and Rb. Ca and Sr concentrations for fluid inclusions in halite from the Palo Duro Basin were generally greater than those from the Paradox Basin, and were greater with depth in the basin.