4:30 PM - 4:45 PM
[SGC50-09] Fluorine content reveals new insight into arc magmatism of Southern Volcanic Zone, Chile.
Keywords:fluorine, subduction zone, slab melt, slab fluid
Fluorine contents of most analyzed samples are 100-300 ppm. To understand behavior of fluorine on fractional crystallization, the correlations of SiO2 and FeO*/MgO with fluorine data from a volcano are plotted. This result indicates that the fluorine dependency with these parameters changes at SiO2 = 55 wt% and FeO*/MgO = 4.2, resulting from apatite crystallization and removal from the magma. Thus, the evolved rock samples from which apatite crystallized were excluded from further discussion.
We compared fluorine with major and trace element data obtained by previous study (Shinjoe et al., 2013) and newly revealed that the fluorine concentrations of selected samples were not correlated with boron concentrations. This means that fluorine shows different behavior in the subduction zone magmatism though both fluorine and boron are fluid-mobile elements. The basaltic samples from Hudson, the southernmost volcano of SVZ, show very high fluorine concentration (〜1000 ppm). Similar anomalies were confirmed also with Nb and Ta. The chemical characteristics suggest that the magma source of this region has been derived from the metasomatized mantle wedge by influence of slab-derived melt (Kilian and Behrmann 2003; Shinjoe et al., 2013). The fluorine concentration possibly becomes new sensitive detector of slab-derived melt in arc volcanism.