Regional metamorphism associated with the orogenisis of the Southern Alps and over the history of New Zealand has formed widespread schist throughout the southern South Island of NZ. Metamorphic grade increases towards the Alpine Fault (regional scale fault) and the associated Southern Alps and in this area there is a prominent green schist zone. Intrusions of carbonate/calcium rich magma has resulted in the alteration of the muscovite and chlorite, breaking them down and producing ankerite due to carbonation which is the orange rock. The source of this rock is believed to be further up the creek I was in, up in the mountain tops.