Figure 21. Step-wise heating experiments for magnetites and olivine separated from ultrabasic rocks (see Tables 1-3 for SB-3 and KV-5, and Table 5 for BEG-1). Notice three separated loss events: (1) Low temperature loss which is most probably related to decripitation of large vesicles; both trapped 3He (see Figures 12, 14) and radiogenic 4He* = 3He (4He/3Hemeas - 4He/3Heinitial) are releasing at this low temperature, < 800oC. (2) Preferential loss of 4He* from related radiation a -tracks under moderate temperature from 600oC to 1100oC. (3) Preferential loss of 3He under high temperature, 1400oC. Arrows indicate that the upper limits of 3He concentrations are shown.