High Temp Stable Isotope

Stable isotope ratios can be used in metamorphic and igneous (i.e., High Temperature) studies to estimate temperatures of mineral equilibration and to identify sources of metamorphic fluids. We routinely analyze oxygen, chlorine, and hydrogen isotope ratios in whole rock, silicates, and oxides.

Laser Fluorination

We are equipped with a laser fluorination oxygen extraction line that is capable of measuring δ¹⁸O and δ¹⁷O values in silicates and oxides. This system utilizes a New Wave Research MIR10-30 laser that is coupled to a BrF5 vacuum extraction system. An aliquot (approximately 0.1 atmosphere) of purified BrF5 is expanded into the sample chamber. The laser is used to heat the minerals in the presence of BrF5, producing oxygen gas and solids and gaseous fluorides as reaction products. The oxygen gas is then purified using a series of liquid nitrogen and NaCl traps. Purified oxygen is quantitatively collected on 5Å molecular sieve. Oxygen isotope values are measured using a dual inlet belows system in our Thermo MAT253 stable isotope ratio mass spectrometer. Up to 44 samples and standards can be loaded at one time. We require approximately 2.0mg of sample for a typical analysis. Precision is ±0.05‰.

Chlorine Extraction

We are equipped with a CH3Cl purification line to measure δ³⁷Cl values of Cl in silicates and natural waters. Solid samples are washed with 18 megaohm deionized water in an ultrasonic bath and then dried at low heat to remove any soluble chloride. Washed solid samples are pyrohydrolized (melted in a water vapor stream) to extract structurally-bound Cl from the sample into an aqueous solution. Cl-bearing solutions are reacted with AgNO3 to produce AgCl. Trace levels of sulphur are removed using 50% nitric acid with gentle heating on a hot plate. The AgCl is then reacted with CH3I to produce CH₃Cl in vacuum-sealed pyrex glass break seals. CH₃Cl is separated from excess CH3I using the online purification system.  δ³⁷Cl values are measured using our MAT253 isotope ratio mass spectrometer configured for collecting masses 50 and 52 simultaneously. Both dual inlet and continuous flow analyses can be performed.

Thermal Conversion Elemental Analysis

We are equipped with a TCEA to measure hydrogen isotope ratios from solid samples including volcanic glasses. Depending on hydrogen content, up to 5mg of sample is loaded into silver capsules. Using a Costech Zeroblank autosampler, the samples are dropped into a 1450°C glassy carbon reactor in a continuous flow of helium. Carbon monoxide, Nitrogen and hydrogen are separated using gas chromatography. Hydrogen isotope ratios (δD values) are measured with our MAT253 isotope ratio mass spectrometer configured for collecting masses 2 and 3 simultaneously.