Approximately 2.4 million ounces of gold and 11.3 million ounces
of silver have been produced from the Umuna Lode by Misima
Mines Pty Limited between June 1989 and the end of Decemeber
1996. Reserves remaining at the end of December were 32.1
million tonnes at 1.0 gram per tonne gold and 9.7 grams per tonne
silver. To attain precious metal production of this volume, an estimated
K60,000,000 (1996 Kina) was spent on exploration alone. from
the 1940s to the present day. Exploration expenditure for the 1996
calendar year was approximately K4,400,000. With such a large investment in exploration, large quantities of
data were generated and stored in various forms. To make best
use of this data, it was necessary to organise and systematically
store this data in a form compatible with a modern Geographical
Information System (GIS). The Umuna Lode on Misima Island is a low sulphidation gold- silver deposit dated at 3.5 0.2 Ma. The deposit is controlled by
the 50 to 100 metre wide Umuna Fault- a moderate dipping,
brecciated clay- chlorite- carbonate altered, normal fault zone.
There is approximately 230 metres of mostly dip slip offset on
this fault, which is measurable by the offset of the Cretaceous
schist, marble and greenstone host sequence. Late Miocene
microdiorite spatially related to the Umuna Lode does not appear
to be genetically related to the gold- silver mineralisation. GIS was introduced to Misima at the end of 1995 and until recently
has been mostly used for data storage and retrieval, the over- laying of various data sets to assist in targeting prospective areas,
and as a drafting tool. The use of data-driven, predictive data
analysis is the most recent effort in maximising the use of the
extensive Misima database. By characterising the key controls and properties of the Umuna- type mineralisation, a Weights of Evidence, data-driven analysis
produced a prospectivity map of Misima Island. The purpose of
this map was to identify prospective areas yet to be explored and
to assess the effectiveness of exploration to date.