Three texturally distinct symplectites occur in mafic granofels of the Arthur River Complex at Mt Daniel, Fiordland, New Zealand. These include symplectic intergrowths of clinopyroxene and kyanite, described here for the first time. Pods of mafic granofels occur within the contact aureole of the Early Cretaceous Western Fiordland Orthogneiss batholith. The pods have cores formed entirely of garnet and clinopyroxene, and rims of pseudomorphous coarse-grained symplectic intergrowths of hornblende and clinozoisite that reflect hydration at moderate to high-P. These hornfelsic rocks are enveloped by a hornblende-clinozoisite gneissic foliation (S1). Narrow garnet reaction zones, in which hornblende and clinozoisite are replaced by garnet-clinopyroxene assemblages, developed adjacent to fractures and veins that cut S1. Fine-grained symplectic intergrowths of (1) clinopyroxene and kyanite and (2) clinozoisite, quartz, kyanite and plagioclase form part of the garnet reaction zones and partially replace coarse-grained S1 hornblende and clinozoisite. The development of the garnet reaction zones and symplectites was promoted by dehydration most probably following cooling of the contact aurcole. Maps of oxide weight percent and cation proportions, calculated by performing matrix corrections on maps of X-ray intensities, are used to study the microstructure of the symplectites.
- Garnet granulite
- Hornblende-clinozoisite and clinopyroxene-kyanite symplectites
- Lower crust
- New Zealand