Crystal size distribution of garnet and geochemistry of Hal Hal Chaldoran garnet amphibolites-Northwest corner of Iran

The Hal Hal Chaldoran garnet amphibolites, one of the Mesozoic colored mélange components, are investigated for their geochemistry and crystal size distribution (CSD). These rocks are rich in (Fe-Mn rich) garnet and green/blue amphiboles and have less plagioclase, chlorite, epidote and opaque minerals have porphyroblastic texture and foliation due to regional metamorphism. The rocks are ortho-amphibolites which have a tholeiitic basalt protolith formed on an intra-plate setting with a high degree of crustal contamination. The garnet with considerable abundance (due to access to suitable materials and mechanism) show a linear CSD pattern with a slope of -3 for coarse-grain samples up to -7 for finer grain rocks. The ratio of nucleation to growth rates for these minerals is 4 to 7 times. Multiple nuclei were formed by a large degree of overstepping in the rocks and regular morphology of the grains indicates crystallization under crystal interface control (not fluid diffusion control).