6:15 PM - 7:30 PM
[SIT07-P02] Petrography of mantle xenoliths from Lyudao, in the Luzon arc, Taiwan
Keywords:xenolith, mantle, peridotite, Luzon arc, Taiwan, Lyudao
Peridotite xenoliths are mainly harzburgite with one olivine websterite. Harzburgite shows two types in terms of grain size; fine-grained (less than 0.1mm across) and coarse-grained (several millimeters across). These textures coexist in hand-specimen. There is no difference in mineral mode between them. These petrological textures are the same as those of Batan Island (Arai et al., 1996). Amphibole occurs at the border part of the host andesite and peridotite xenoliths. The Fo content [=100Mg/(Mg+Fe2+) atomic ratio] of olivine is from 91 to 92. The Al2O3 content and Mg# [=Mg/(Mg+Fe2+) atomic ratio] of orthopyroxene are from 2.4 to 3.5 wt%, and from 0.90 to 0.92, respectively. The Al2O3 and Cr2O3 content, and Mg# of clinopyroxene are from 1.7 to 4.3 wt%, about 1 wt%, and from 0.90 to 0.94, respectively. The TiO2 and Na2O contents of clinopyroxene are very low, being from 0 to 0.2 wt%. Fe3+/(Cr+Al+Fe3+) atomic ratio of spinel is very low, mostly being less than 0.2, There Cr# [=Cr/(Cr+Al) atomic ratio] and TiO2 content is from 0.4 to 0.6, and from 0 to 0.1wt%, respectively.