The Mode of Occurrence, Petrography, Metamorphism and Origin of Amphibolites of Devgad Baria Panchmahals District, Gujarat State

Amphibolites occur towards south and south-east of Devgad Baria town in the Panchmahals district of Gujarat State, in the form of disconnected bands showing concordant relationship with the rocks of the Banded gneissic complex and passing into striped varieties, and also as caught-up patches in the granitic intrusive bodies. Mineralogically, the former type is a quartz and plagioclase bearing amphibolite, while the latter is only plagioclase-bearing.

The quartz-amphibolites are shown to be para-amphibolites on the basis of their intimate association with the impure calcareous metamorphosed sedimentary rocks, lack of relict igneous textures, absence of sphene and plagioclase, high modal percentage of quartz, and low weight percentage of TiO₂ and Al₂O₃ showing a near concordance with the alumina content of marbles of the area. On the other hand, the plagioclase-amphibolites show, in addition to the disconnected sill-like form, relic sub-ophitic texture, high proportion of sphene and high weight percentage of TiO₂ and Al₂O₃ indicating their primary igneous nature.