Titanite (1%) use to develop a reaction rim around rutile (Figures 5c-d).
Ti-clinohumite (low PHF), a mineral of the humite group, formed in forsterite marbles and may be stabilized by the presence of Ti (probably as a result of the formation of titanite reaction rims around rutile.
Map cracking, exudation of white gel, and reaction rim around aggregates are characteristic of AAR .
In addition, the characteristics of alkali-aggregate reaction such as map cracking, white gel, and reaction rim around aggregates have not been found both in field and in lab.
The Fe content in titanites which form reaction rims around ilmenite is low, about 0.02 a.p.f.u.
In thin sections, the apparent reaction rims of titanite on ilmenite grains occur in a direct association with plagioclase and amphibole in amphibolites, thuis representing another sign of variable oxygen fugacity or [H.sub.2]O activity during the Moldanubian metamorphism.