Application of microprobe-based flank method analysis of Fe3+ in garnet of North Qilian eclogite and its geological implication

作者：Li, Xiaoli^*; Song, Shuguang; Zhang, Lifei; Hoefer, E. Heidi

来源：Science Bulletin, 2018, 63(5): 300-305.

DOI：10.1016/j.scib.2018.01.025

• Microprobe
• Flank method
• Ferric iron
• Garnet
• North Qilian eclogite

A newly developed microprobe-based methodology (the Flank Method) for Fe3+/Sigma Fe quantification has been successfully applied to some natural garnets from the North Qilian eclogites by JEOL JXA-8100 microprobe at Peking University. The results demonstrated an obvious discrepancy in comparison with the outcomes by conventional stoichiometric calculations. This methodology allows to measure the Fe3+/Sigma Fe ratio and perform elemental analyses simultaneously in the same condition. Accurate in-situ measurement of Fe3+ content in garnet may bring certain impact on the garnet-based P-T estimation. According to the compositional zonation displayed in the studied eclogitic garnets from North Qilian, a prograde metamorphic PT path from 19.5 kbar, 520 degrees C to 22 kbar, 600 degrees C was reconstructed. More interestingly, the measured Fe3+/RFe ratios in garnets decreasing from core to rim may probably imply that the oxygen fugacity (fO(2)) declines with the depth of the subduction zone.

• 出版日期2018-3-15
• 单位北京大学