Abstract:
Thin and polished sections of thirty-six rock samples from Amoanda Pit in the Tarkwaian
showed that the banket footwall quartzites contain mainly quartz, chlorite, plagioclase,
amphibole and minor sericite, epidote, chalcopyrite, pyrite, magnetite, hematite and trace
gold. The protoliths of the rock were probably sublitharenite, feldspathic litharenite and
litharenite. Overlying banket conglomerate at the Saddle Pit is oligomictic or polymictic
with large rounded pebbles and moderately sorted quartz, chert, schist, and hornstone; the
matrix is made up of quartz, plagioclase feldspars, sericite, chlorite, garnet and amphiboles.
At the Saddle Pit, diorite sills and dykes contain mainly plagioclase feldspars, amphibole,
chlorite, sericite and quartz with minor epidote, biotite, garnet, pyroxene, pyrite, pyrrhotite
and chalcopyrite. Pyrite is partially altered to secondary hematite and magnetite. The
intrusive heat might have introduced secondary amorphous gold other than the palaeoplacer
granular gold in the banket footwall quartzite and the conglomerate. Post placer gold was
secondary mainly at the contacts with diorite and associated with second generation
hematite and magnetite. Generally the rocks were affected by greenshist facies
metamorphism which post-date peak amphibolite facies. Whole rock XRF analyses show
Al2O3 range from 6.86 to 26.6 wt% possibly due to plagioclase which is partially altered to
sericite and quartz. Eu anomaly values are greater than 1 probably due to plagioclase
accumulation while high total REE could be due to high alteration of the rocks.
