Seminar

Arc magma generally records higher oxidation states than magma generated in other tectonic settings, but the origin of the oxidized nature remains controversial. Some studies proposed that primary magmas in arc system derived from the mantle wedge oxidized by slab-derived components. By contrast, redox-sensitive element ratios (e.g., V/Sc, V/Ga, or Zn/Fe) in primitive arc rocks argue that redox exchange during the prolonged magma ascent and differentiation may account for the oxidization state of arc magma. Melt inclusion offers a unique opportunity to check the redox state of the primitive magma before differentiation, although recent studies indicate possible modification after their entrapment. In this study, two types of olivines and their melt inclusions from the pillow lava at Margi in the Troodos ophiolite, were taken for systematic analyses. The results illustrate limited change of V distribution coefficient between the olivine and melt inclusion at the post entrapment stage. The oxidation state is calculated to be about FMQ +1.5, which is higher than the mid ocean ridge basalts, therefore supporting the view that the oxidized nature of the arc magmas is inherited from the mantle source rather than a result of magma evolution.