Analysis - Trace elements
Trace element abundances offer important constraints on petrogenetic processes. The trace elements are measured through a suitable isotope (either the most abundant isotope or one free from interference). The isotope ratios are ratioed to the isotope of a major element (e.g. Ca, Si) whose concentration can be determined through electron microprobe anlaysis. The ionic ratios are calibrated to a standard for which the trace element concentrations are independently known.
[Ci] = SFi*[Ca]*(ci+/44Ca+)
Ci is the concentration of the element i
SFi is the sensitivity factor of element i relating the yield of the element to the yield of the normalizing isotope (44Ca) and the Ca concentration of a standard.
[Ca] is the concentration of Ca in the unknown determined by electron microprobe
(ci+/44Ca+) is the measured ion intensity of the relevant isotope to 44Ca+.
Trace element abundance pattern in Archean komatiite glass inclusions showing systematic incompatible element depletion. Zr and Ti are also depleted because these elements have fractionated into clinopyroxene. (McDonough and Ireland 1993).