Otago Schist in the
Mount Patriarch, High Burn and Cameron Creek areas of northwest Otago grades from
textural grade IIA in the east to textural grade III in the west. The entire
region is of the actinolite-pumpellyite metamorphic facies. Lithologies in the
area are interbedded turbidite sequences comprising pelite and psammite together
with pebble conglomerate, greenschist and metachert horizons. The mineral
assemblage of the schist is typically
quartz-albite-epidote-actinolite-pumpellyite-chlorite-stilpnomelane-calcite. A
good foliation is well defined in the area and is predominantly parallel to
bedding, except in hinges of mesoscopic isoclinal folds. The structure of the
area appears to be defined by a large southwest plunging isoclinal fold defined
by bedding with a steeply dipping axial planar foliation. Kink folding and
dextral strike-slip faulting in the area postdates the ductile phase of
deformation. Pods of rhodonite, rhodochrosite, spessartine garnet, coombsite,
caryopilite, Mnstilpnomelane and Ni-Cu-Zn sulphides were found in concordant
metachert layers in the Mount Patriarch area. Metachert was also found
in float in the Cameron Creek area. Malachite occurrences relating
to copper mineralisation were also noted in a green metachert horizon on the
eastern flank of Mount Patriarch. The coombsite, in only the
third observation worldwide, is the most Fe-rich variety
reported.