A Review of Mg Isotope Analytical Methods by MC-ICP-MS

Application of multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) has led to big breakthrough of analytical methods for metal stable isotopes, resulting in rapid progresses in non-traditional stable isotope geochemistry. As a new geological tracer, Mg isotopes have been widely applied in studies of almost all important disciplines of geochemistry. High precision Mg isotope data measured by MC-ICP-MS are now available with precision about 0.05‰ amu (2SD) or better. Because mass bias caused by chemical procedure and instrument can easily cause significant analytical error, it is still a challenge to obtain accurate Mg isotope data for natural samples. In this paper, we systematically review the development of analytical technique of Mg isotopes, with a detailed description of a series of important techniques used in the measurement process, including calibration of instrumental mass-bias, chemical purification process, matrix effect, and pitfalls for high precision isotope analyses. We compare standard data from different labs and establish a guideline for Mg isotope analysis procedure. Additionally, we briefly discuss the behaviors of Mg isotopes during geological processes including equilibrium and kinetic Mg isotope fractionations, such as magma differentiation, chemical and thermal diffusion, and continental weathering. Finally, we propose some future prospects for Mg isotope geochemistry in both high and low temperature geological processes.