Host: The Japanese Association of Mineralogists, Petrologists and Economic Geologists
Khondalite is a graphitic garnet-sillimanite-alkali feldspar-quartz granulite commonly associated with quartzites and dolomitic marbles in the Highland Complex of Sri Lanka.Symplectitic intergrowth of corundum and alkali feldspar (or K-feldspar and sodic plagioclase) is newly found to replace sillimanite partially in the vicinity of quartz in some khondalites, in which both sillimanite and garnet are irregularly replaced by symplectitic intergrowths of hercynite + sodic plagioclase most probably caused by fluid infiltration. Partial melting is inferred to have taken place in the rock when the fluid infiltration occurred, because such a local steep gradient of chemical potential of silica can be formed not by the presence of fluid but by partial melting of coarse-grained dissimilar minerals (e.g., quartz and feldspar) as revealed by experiments.
